ASME Conference Presenter Attendance Policy and Archival Proceedings

2012;():i. doi:10.1115/DSCC2012-MOVIC2012-NS2.

This online compilation of papers from the ASME 2012 5th Annual Dynamic Systems and Control Conference joint with the JSME 2012 11th Motion and Vibration Conference (DSCC2012-MOVIC2012) represents the archival version of the Conference Proceedings. According to ASME’s conference presenter attendance policy, if a paper is not presented at the Conference, the paper will not be published in the official archival Proceedings, which are registered with the Library of Congress and are submitted for abstracting and indexing. The paper also will not be published in The ASME Digital Collection and may not be cited as a published paper.

Commentary by Dr. Valentin Fuster

Legged Locomotion

2012;():1-9. doi:10.1115/DSCC2012-MOVIC2012-8562.

Since fall has been identified as the number one cause of death and injury of old people, development of technologies for prediction and prevention of falls is highly needed, especially for the aging society. This paper presents a preliminary study of using two indices related to dynamic stability of a human body in standing and walking for the potential application of predicting the risk of falls. The dynamic stability index for standing measures the degree of alignment between the center of mass and the center of pressure of a human body when the human is intended to standing still. The dynamic stability index for walking is derived from the well-known inverted pendulum model of human walking dynamics. The two indices can be easily computed from the test data measured by a 3D motion capture system and an instrumented treadmill. As a pilot study, five older adults who have recent history of falls were tested and another five older regular adults were also tested as a control group. The test data showed that the values of the indices for the two groups are clearly distinguishable. This is a good indication that the proposed indices have a good potential for predicting the risk of falls of older adults. This finding encourages further research along the line.

Commentary by Dr. Valentin Fuster
2012;():11-18. doi:10.1115/DSCC2012-MOVIC2012-8566.

In this research, we developed an ankle-foot assist device for foot rehabilitation and walking assistant purpose. In order to support all 6 DOFs human foot motion (the rotations of human foot and the displacement of rotation axes), a six air cylinders drive Stewart Platform Mechanism was used. In our previous work, we have proposed a measuring and calculating method to get the posture of human foot and estimate the instantaneous rotation axis of ankle joint [1]. In this paper, we further propose a new method to control the position, force and stiffness of this device. The position can be controlled even if the potentiometers do not measure the length of air cylinders directly. The force can be controlled by changing the air pressures in two chambers of each cylinder, without using any force sensors. The stiffness can also be controlled which is controlled by changing the stiffness of all cylinders, by changing the pressures in chambers. These control methods are tested in experiments for one cylinder and for developed assist device. The results show the accuracy and validity of the device and the method in the control of position, force and stiffness.

Topics: Stiffness
Commentary by Dr. Valentin Fuster
2012;():19-23. doi:10.1115/DSCC2012-MOVIC2012-8663.

In steady human walking and running, every step is similar to every other, but they are not all identical. That is, the motion is nearly but not exactly periodic. In this paper, we construct models of the dynamics near the periodic motion of human locomotion from the near-periodic steady data. We use a sequence of Poincare sections (transverse to the periodic orbit) in the neighborhood of the periodic orbit and linearized dynamics of the state from one Poincare section to the next, essentially resulting in a piecewise linear dynamical system around the periodic orbit. Using human locomotion data obtained from a high-accuracy motion capture system, a piecewise linear dynamical model is constructed to represent human running/walking. The piecewise linear model can predict human transient dynamics under various circumstances. We show responses to perturbations to the swing leg.

Commentary by Dr. Valentin Fuster
2012;():25-32. doi:10.1115/DSCC2012-MOVIC2012-8673.

Normal human gait, described as passive dynamic walking, is neither completely passive nor always dynamic. In this article, we introduce the formulations of Passive Gait Measure (PGM) and Dynamic Gait Measure (DGM) that quantify passivity and dynamicity levels, respectively, of a given biped walking motion. The proposed concepts will be demonstrated through the analysis of human walking experimental data. The PGM measures the relative actuation contribution of the pivot joint of stance leg in the inverted pendulum analogy. The DGM, associated with gait stability, quantifies the effects of inertia in terms of the Zero-Moment Point (ZMP) and the ground projection of center of mass (GCOM). Human walking motion during single and double support phases is reconstructed from raw experimental data, and ZMP and GCOM trajectories during one full step cycle are generated. The calculated PGM values show the passive nature of human walking when the inverted pendulum analogy is adopted. The DGM results verify the dynamic nature of human walking demonstrating their dependence on the walking motion as well as the step phase; the double support phase results a static motion, opposite to the highly dynamic single support phase. The results will benefit the human gait studies and the development of walking robots.

Commentary by Dr. Valentin Fuster
2012;():33-39. doi:10.1115/DSCC2012-MOVIC2012-8697.

Iterative adaptive on-off control is a potential control strategy for ultra-low-power control of micro-actuators that behave as capacitive loads. Such an approach allows for relatively low sensor sampling frequencies and the use of simple switched inputs, which can be implemented at lower power levels than control with analog inputs and real-time feedback. A technique is presented for estimating the convergence time of an on-off controller proposed for controlling stepping motion in autonomous micro-robots. Error in measured outputs at each iteration are estimated using upper bounds on output error as a function of error in on-off switching times and lower bounds on the change in on-off switching times from iteration to iteration. While a strict upper bound on error is not provided by the final error estimator, simulation and experimental results from the test case of a piezoelectric micro-robotic leg joint indicate reasonable agreement between estimated error and full controller behavior. Convergence estimates may then be used to improve controller design with respect to total energy consumed.

Topics: Robotics
Commentary by Dr. Valentin Fuster
2012;():41-48. doi:10.1115/DSCC2012-MOVIC2012-8754.

In this study, a feasibility study on the stability of quadrupedal gait patterns with changeable body stiffness is reported. The periodic motions of the legs are generated as a rhythmic motion. The stability of locomotion strongly depends on the mechanical properties of the body mechanism, visco-elastic property of the the trunk. In this report, the muscle tone of the robot motion at the trunk is changeable by using the changeable visco-elasticity of the pneumatic actuators. The stability of quadruped locomotion in crawl, trot and pace patterns with changeable body’s visco-elasticity was evaluated with hardware experiments. And the stabilization mechanism is approximated by a simple two-inertia system model and analyzed with numerical simulations.

Commentary by Dr. Valentin Fuster

Mechatronic Systems

2012;():49-54. doi:10.1115/DSCC2012-MOVIC2012-8549.

Galvano scanners are used as laser beam scanners in laser drilling machines. The galvano scanner requires high-speed and high-precision control for more precise laser processing with high throughput. Heat generated by current amplifiers becomes problematic as the positioning speed of the galvano scanner increases. We propose a final-state control (FSC) method that considers voltage constraint of the current amplifiers. By considering the constraint of the applied voltage on the motor, the power supply voltage of the current amplifier can be lowered. Therefore, the electricity consumption and the heat generated by the current amplifier can be reduced. Experimental results show the effectiveness of the proposed method.

Commentary by Dr. Valentin Fuster
2012;():55-60. doi:10.1115/DSCC2012-MOVIC2012-8560.

Series magnetic suspension is applied to force measurement. In a double series magnetic suspension system, two floators are suspended with a single electromagnet. The attractive force of the electromagnet directly acts on the first floator in which a permanent magnet is installed. The motion of the second floator is controlled indirectly through the attractive force of the permanent magnet. When PID control is applied to the second floator, the first floator displaces proportionally with the external force acting on the second floator even though the second floator does not move in the steady state. Therefore, the force can be estimated for the displacement of the first floator. When the stiffness between the first and second floators is low, even small force leads to large displacement so that the proposed measurement method is suitable for noncontact measurement of micro force. An apparatus was fabricated for experimental study on the proposed measurement method. Its effectiveness was demonstrated experimentally.

Commentary by Dr. Valentin Fuster
2012;():61-65. doi:10.1115/DSCC2012-MOVIC2012-8602.

This paper presents a novel modeling method and a control system design procedure for a flexible rotor with many elastic modes using active magnetic bearings. The purpose of our research is to let the rotor rotate passing over the 1st and the 2nd critical speeds caused by flexible modes. To achieve this, it is necessary to control motion and vibration of the flexible rotor simultaneously. The new modeling method named as Extended Reduced Order Physical Model is presented to express its motion and vibration uniformly. By using transfer function of flexible rotor-Active Magnetic Bearings system, we designed a local jerk feedback control system and stability analysis by using root locus is carried out. Levitation experimentation is performed and stable levitation and significant vibration suppression effect is achieved.

Commentary by Dr. Valentin Fuster
2012;():67-72. doi:10.1115/DSCC2012-MOVIC2012-8812.

A double parallel magnetic suspension with parallel connection is achieved. In the double parallel magnetic suspension system, two magnetic suspension subsystems are controlled with a single power amplifier. Double parallel suspension systems are classified into two types based on the connection of the two coils: series-connected and parallel-connected. The feasibility of series-connected magnetic suspension has been already demonstrated in the previous works. This paper focuses on the parallel-connected parallel suspension. The controllability of the parallel-connected parallel suspension is discussed based on a mathematical model. The feasibility of parallel-connected magnetic suspension is demonstrated experimentally.

Commentary by Dr. Valentin Fuster
2012;():73-79. doi:10.1115/DSCC2012-MOVIC2012-8825.

This paper describes non-contact manipulation mechanism of multi-DOF (degrees of freedom) magnetically suspended system. This manipulation system uses unique suspension mechanism whose suspension force is controlled by air gap length. This mechanism is composed of permanent magnets and linear actuators. We study the stability of a 2 DOF suspension system which manipulate the object in the vertical plane. To analyze the stability of the system, we assume that the attractive force acts on the direction from the magnet tip to the center of the object, and is inversely proportional to the square of the air gap length. In this paper, the principle of the suspension mechanism is explained and a prototype 2 DOF system is introduced. We make a linearized model of the system and the feedback gains are calculated by linear control theory. Numerical simulations on the nonlinear 2 DOF system are carried out. In experimental system, the magnetic field analysis is investigated on the system by an integral element method and the characteristics of the system are studied. Non-contact suspension is examined experimentally. Numerical and experimental results support the feasibility of the multi-DOF non-contact manipulation system.

Commentary by Dr. Valentin Fuster
2012;():81-85. doi:10.1115/DSCC2012-MOVIC2012-8876.

Design aspects of a linear reluctance actuator used as shaker in vibration test rigs are presented. The bidirectional trajectory tracking device provides forces up to 10 kN and a stroke range of 7 mm. Key features for high performance and robust operation are a polarized topology and strong armature springs. Core and armature lamination ensure high actuator dynamics. Experimental results with a prototype device confirm the presented methods and design aspects. The main advantage compared to conventional shakers are a high force density and energy efficiency.

Commentary by Dr. Valentin Fuster


2012;():87-94. doi:10.1115/DSCC2012-MOVIC2012-8526.

Electro-Mechanical Valve Actuators (EMVA) are a promising solution to actuate engine valves for future camless engines. Their use can increase engine power, reduce fuel consumption and pollutant emissions, and improve significantly engine efficiency. This paper is concerned with the soft landing control of a double magnet EMVA system. In particular, a force control algorithm based on a combined feedforward and feedback sliding mode control actions is presented. The aim of the control is to stabilize the system while tracking a model-based reference trajectory. It is shown by numerical simulations that the proposed control approach guarantees soft landing operation even in the presence of external force perturbations and friction force variations.

Commentary by Dr. Valentin Fuster
2012;():95-102. doi:10.1115/DSCC2012-MOVIC2012-8711.

This paper shows a practical design method for a displacement amplification mechanism for a piezoelectric actuator which employs a buckling-like phenomenon. This mechanical singularity realizes a substantial displacement magnification, at least 50 times, within a simple structure. An SMA preload mechanism essentially provides potential for full range push-pull actuation to the piezoelectric actuator. This integrated actuator performs a high energy transfer ratio and is suitable for brake mechanisms due to their requirement of high force, specific displacement and energy efficiency. A practical design method is shown and is evaluated by comparing the analytical model with finite element analysis and experimental hardware performance. The actuator properties obtained by these methods fit well each other with errors less than 13%.

The experimental actuators are applied to a brake for a commercial motor and its properties are evaluated. The brake can produce more than 2.5Nm in the displacement range of 0.5mm. These experimental results suggest that this novel piezoelectric actuator has potential for use in a wide range of applications.

Commentary by Dr. Valentin Fuster
2012;():103-112. doi:10.1115/DSCC2012-MOVIC2012-8775.

In addition to a well-designed and tuned control system and a properly designed mechanical system, accurate motion control in industrial machines heavily depends on trajectory planning and the appropriate selection of the motors controlling the axes of the machine. A model-based design approach to properly select a motor prior to building a prototype is proposed in this paper. Additionally, a trajectory planning approach is proposed and demonstrated to improve position control accuracy of industrial machines. The proposed motor selection process and trajectory planning approach are demonstrated via modeling and simulation of a commonly used planar robot (H-Bot).

Commentary by Dr. Valentin Fuster
2012;():113-122. doi:10.1115/DSCC2012-MOVIC2012-8798.

This paper experimentally validates the simulation model developed in previous work to improve the reliability and efficiency of robot arms via a passive-assist design approach. Specifically, this procedure alters the mechanical design of a robot arm by incorporating a parallel spring designed to reduce the peak motor torque and energy required to perform a specified maneuver. Our experiment consisted of a single link robot arm, worm gear transmission, DC motor, sensors, and a PC based controller. We experimentally demonstrated that our model is accurate to within 3% and that the addition of a well-designed spring can reduce peak motor torques by ∼50% and energy consumption by as much as 25%.

Topics: Robots , Reliability , Design
Commentary by Dr. Valentin Fuster
2012;():123-130. doi:10.1115/DSCC2012-MOVIC2012-8813.

Due to the limited displacement of piezoelectric stack actuators, common practice is to use some form of displacement amplification mechanism. This paper focuses on an externally leveraged mechanism that utilized a buckling motion to achieve large amplification ratios within a single stage. This mechanism interfaces with a sinusoidal gear track that acts as the load. The dynamics of the system are derived and are shown to be fifth order. Due to the significantly nonlinear amplification caused by the buckling phenomenon and the gear, the dynamics are run in simulation to gain insight into the performance of the actuator. There is shown to be an optimal speed at which to run the actuator to maximize the possible power output. Furthermore, due to the simple binary control significant benefits are achieved by varying the control timing based on the velocity to ensure the force and velocity of the output are in phase.

Commentary by Dr. Valentin Fuster
2012;():131-138. doi:10.1115/DSCC2012-MOVIC2012-8833.

A key step along the way to understanding the natural motion is producing a physical, well understood actuator with a dynamic model closely resembling biological muscle. This actuator can then serve as the basis for building viable, full-strength, and safe muscles for disabled patients, human force amplification, and humanoid robotic systems. This paper presents an expanded fingerprint method for calculating the dynamic equations of motion for cellular actuator arrays, an actuator technology which combines many small flexible ‘cell’ actuator units for large-scale motion. The new method is simpler and quicker than generating the dynamic equations of motion from base principles, allows for fast recalculation for different and immense cell array structures, and provides an intuitive base for future controls work on cell array actuators. The paper also presents a physical SMA based cellular actuator array which, when compared with simulated results, matches the presented theory closely. Finally a brief discussion about the uses of the expanded fingerprint method, including controls and design work in robotics, is given. In the future, the theory will be used and extended to develop high degree-of-freedom cellular array actuated robotic devices with natural motion for use in rehabilitation, prosthesis development, human force amplification, and general robotics. These new devices will be especially effective at working safely around and with humans in complex human environments.

Commentary by Dr. Valentin Fuster

Mechatronics for Aquatic Environments

2012;():139-146. doi:10.1115/DSCC2012-MOVIC2012-8511.

In this paper, the feasibility of tracing shallow water flows in illuminated light conditions by using buoyant fluorescent particles is investigated. An automated image analysis-based procedure is developed for on-line detection and real-time tracking of particles using a computationally inexpensive algorithm implemented on recorded videos. The methodology is validated through experiments conducted in a custom-built miniature channel specifically developed for simulating controlled shallow water conditions. Experimental findings suggest that the proposed methodology could be successfully integrated in field flow tracing systems for overland flow velocity.

Commentary by Dr. Valentin Fuster
2012;():147-154. doi:10.1115/DSCC2012-MOVIC2012-8520.

This paper presents a small scale experimental setup for autonomous target tracking of a surface vessel in the presence of obstacles in rough sea states through wave, current, and wind generation in an indoor pool. The experimental setup and a method of scaling and similitude with real world scenarios are discussed. Absolute position of the agent, the target, and obstacle size and position are provided through an overhead camera by detecting color light emitting diodes installed on all objects. A sliding mode control is implemented for real time tracking control which is capable of rejecting large wave and wind disturbances. The sliding mode control signals are sent to wireless receivers on the autonomous vessel where a proportional integral speed controller maintains the commanded speed. In these experiments, the USV mission is to follow a target vessel while avoiding any obstacles that are present on its path in rough sea conditions.

Commentary by Dr. Valentin Fuster
2012;():155-162. doi:10.1115/DSCC2012-MOVIC2012-8521.

This paper studies the response of zebrafish to a bioinspired robotic-fish. The robot’s color pattern and morphophysiology are modulated to emphasize features normally admired by zebrafish in conspecifics. A three-chambered instrumented tank is utilized to conduct a series of preference tests, offering the robotic-fish as a stimulus, juxtaposed with an empty compartment, to live zebrafish. The time spent by fish in the proximity of either stimulus compartment is used to score the preference of an individual to a stimulus. The tail-beating motion of the robotic fish is manipulated based on closed- and open-loop control strategies. The closed-loop controller uses the distance of the live-fish from the robotic-stimulus as its control input, while the open-loop controller provides a tail-beating motion, irrespective of fish behavior. Live-fish locomotion patterns and their preference space are compared and analyzed to ascertain the effects of closed-loop control on zebrafish response. This study’s results suggest that closed-loop control reinforces attraction to the robotic-stimulus, as compared to the open-loop approach, over extended exposure to the robot, therefore aiding against habituation to a stimulus.

Commentary by Dr. Valentin Fuster
2012;():163-170. doi:10.1115/DSCC2012-MOVIC2012-8545.

In this paper, we propose a computational approach to estimate the forces acting on a rigid wedge as it impacts a free water surface. The approach is based on the Lattice-Boltzmann Method, wherein the fluid is described as a set of particles streaming and colliding in a discrete time-space environment. Predicted slamming forces are compared with closed-form results based on potential flow and experimental results on drop-tests of rigid wedges.

Commentary by Dr. Valentin Fuster
2012;():171-178. doi:10.1115/DSCC2012-MOVIC2012-8571.

Although many species of robotic animal models have been developed in recent years, their effect on animal behavior is largely unexplored. In this work, we investigate the feasibility of regulating the behavior of golden shiners (Notemigonus crysoleucas) engaged in a risk-taking test using a robotic fish displaying characteristics of bold or shy individuals. Fish are characterized according to an individual boldness criterion and their individual interactions with a self-propelled biomimetic robot exhibiting typical bold and shy behaviors are scored. We find that bold individuals are relatively insensitive to the behavior of the robot, while the presence of the robot may embolden shy fish. Specifically, shy fish show affinity for the robotic fish when it displays both bold and shy behaviors. The results of this work may inform the design of engineering methods to regulate fish behavior for the purposes of animal control, conservation, and production.

Topics: Robots
Commentary by Dr. Valentin Fuster
2012;():179-186. doi:10.1115/DSCC2012-MOVIC2012-8655.

Motion control of bio-inspired mobile robotic platforms can prove a challenging problem. In particular, models for the considered type of systems may prove nonlinear, uncertain, and fairly complicated. To address these issues, use of an output predictor-based control algorithm was proposed. In particular, the approach relies on the design of a virtual system, constructed to emulate the actual system’s input/output behavior. Then, a control law is designed to leverage the dynamic information contained within this predictor. The resulting control scheme proves reasonably concise, and effectively circumvents issues related to partial state measurements and system uncertainty. Simulation results for an anguilliform swimming robot illustrate the control scheme’s efficacy.

Commentary by Dr. Valentin Fuster
2012;():187-193. doi:10.1115/DSCC2012-MOVIC2012-8680.

The Synergistically Propelled Ichthyoid [SPI] is a novel submersible propelled by the combined jet and tail action of a fluttering fluid-conveying pipe. A model for an SPI’s motion in a general planar frame is presented which includes a time-variable conveyed fluid velocity. Simulations using this model show that the tail of the SPI may be used as an effective control surface by leveraging the tail’s ability to “vector” its fluid jet as well as turn the oncoming external fluid like a fish. Methods used to effect rapid turns and simultaneous control of orientation and jet speed are also demonstrated.

Commentary by Dr. Valentin Fuster
2012;():195-201. doi:10.1115/DSCC2012-MOVIC2012-8693.

This paper describes the development of a robot that combines a powerful propeller with a pump-valve system that enables high maneuverability. In order to reduce size and improve turning performance, the design does not include external stabilizers such as fins. Therefore the robot is directionally unstable (yaw direction). In this work we outline the design of a linear stabilizing controller that does not require complicated flow sensors and instead simply uses angle and rate measurements. The linear controller was simulated and then implemented on a prototype robot. Preliminary results reveal that this stabilization method works to enable straight motions and is also able to reject substantial disturbances.

Commentary by Dr. Valentin Fuster
2012;():203-212. doi:10.1115/DSCC2012-MOVIC2012-8695.

Among the various designs of robotic fish, tail-actuation is particularly attractive since it is simple, enables both swimming and turning, and allows a rigid body for housing sensors and electronics. In this paper we present a new dynamic model for robotic fish propelled by a flexible tail that is actuated at the base, and explore the effect of stiffness of the tail beam on the locomotion performance of the robot. The tail is approximated by multiple rigid elements connected in series through rotational springs and dampers, to effectively and efficiently capture the large deformation of the beam. The hydrodynamic force on each segment is evaluated with Lighthill’s large-amplitude elongated-body theory. Model analysis shows that, given the same base movement, the stiffness of the tail has a prominent influence on the tail dynamics and the resulting motion (e.g., speed) of the robotic fish. Experiments are conducted on a robotic fish prototype when it is mounted with a rigid and flexible tail, respectively. The results show that the model is able to predict the motion of the robot for both cases, when the tail base is actuated with a variety of patterns. The model is expected to be instrumental in the optimization and control of robotic fish.

Commentary by Dr. Valentin Fuster
2012;():213-220. doi:10.1115/DSCC2012-MOVIC2012-8747.

Robotic vehicles working in unknown environments require the ability to determine their location while learning about obstacles located around them. A classic approach to solving this problem is feature-based Simultaneous Localization and Mapping (SLAM) using an Extended Kalman Filter (EKF). In this paper, feature-based EKF SLAM is used to examine the feasibility of using a low cost vision-based sensor for performing SLAM in enclosed underwater environments. Classic acoustic-based range sensors suffer from poor performance in enclosed areas due to reflections, furthermore the relatively high cost of acoustic-based navigation sensors prevents their use on low cost underwater vehicles. To overcome these challenges, a custom vision-based range finder and a downward facing camera for the implementation of a standard feature tracking algorithm are used to perform EKF SLAM.

Topics: Sensors , Testing
Commentary by Dr. Valentin Fuster
2012;():221-225. doi:10.1115/DSCC2012-MOVIC2012-8863.

We present a model for the self-propulsion of a circular cylindrical vehicle through a planar ideal fluid. The input to the system is the relative angular velocity of a balanced rotor mounted above the vehicle’s center of mass. A Kutta condition is enforced regularly in time at a point along the edge of the vehicle, enabling the exchange of momentum between the vehicle and the surrounding fluid through discrete vortex shedding. Between vortex-shedding events, the dynamics of the vehicle and its wake are governed by a system of equations with non-canonical Hamiltonian structure. We present simulation results depicting the translational acceleration of the vehicle from rest as a result of sinusoidal oscillations in the position of the rotor, and we demonstrate that the propulsive efficiency of such oscillations exhibits a relative maximum at a certain driving frequency.

Topics: Vortex shedding
Commentary by Dr. Valentin Fuster

MEMS Control

2012;():227-234. doi:10.1115/DSCC2012-MOVIC2012-8698.

A parameterized model for the impact dynamics of a piezoelectric microactuator is proposed, and a system identification procedure for quantifying model parameters presented. The proposed model incorporates squeeze-film damping, adhesion, and coefficient-of-restitution effects. Following parameter quantification from sample data of bouncing impacts and progressive ramped-square-wave inputs, the model is found to be effective at predicting the time response of the actuator to a range of square wave and sinusoidal input. Presence, absence, and quantity of bounces upon impact is successfully predicted, while error in oscillation amplitudes and contact durations range from 1–25% over many test cases of periodic inputs between 5 and 100 Hz.

Commentary by Dr. Valentin Fuster
2012;():235-244. doi:10.1115/DSCC2012-MOVIC2012-8773.

Vibratory micro rate integrating gyroscopes (MRIG) are conventionally modeled using the position and velocity of the gyroscope, as the state space variables. This work describes the dynamic analysis of a z-axis MRIG using an alternate set of dynamic variables, which are the angular momentum, the inner product between position and linear momentum vectors, the Lagrangian and total energy of the system. This alternate description is used to derive the conditions for the ideal gyroscope to operate at the correct precession rate with minimal quadrature. A self-tuning algorithm is presented, which compensates the gyroscope’s damping and sitffness mismatches, while allowing the gyroscope to precess at the correct precession rate with minimal quadrature and reasonable control effort.

Topics: Algorithms
Commentary by Dr. Valentin Fuster
2012;():245-250. doi:10.1115/DSCC2012-MOVIC2012-8828.

This paper deals with the nonlinear response of electrostatically actuated MEMS cantilever resonator under soft DC voltage and soft AC voltage of frequency near natural frequency. The mathematical model of the system is obtained using Lagrange equations. The equations of motion are nondimensionalized and then the method of multiple scales is used to investigate the voltage-amplitude response of the resonator. The influence of the soft DC voltage, fringe effect, and damping on the voltage-amplitude response are reported.

Commentary by Dr. Valentin Fuster
2012;():251-256. doi:10.1115/DSCC2012-MOVIC2012-8829.

This paper investigates the influence of nonlinearities resulting from parametric soft AC electrostatic excitation on the response of cantilever micro-beams near primary resonance. Most of the analysis in literature investigates pull-in phenomenon, stability, amplitude–frequency relations, or finds time responses of such systems. This work uses Reduced Order Model method and shows that the steady-state amplitudes in the amplitude-voltage response are higher than predicted by the Method of Multiple Scales, which is a perturbation method. This result is extremely important for predicting pull-in phenomenon and level of amplitudes at resonance.

Commentary by Dr. Valentin Fuster

Model Predictive Control

2012;():257-266. doi:10.1115/DSCC2012-MOVIC2012-8523.

This paper deals with the problem of robust model predictive control of an uncertain linearized model of a building envelope and HVAC system. Uncertainty of the model is due to the imperfect predictions of internal and external heat gains of the building. The Open-Loop prediction formulation of the Robust Model Predictive Control (OL-RMPC) is known to be unnecessarily over-conservative in practice. Therefore, we adopt a Closed-Loop prediction formulation of Robust Model Predictive Control (CL-RMPC) which exploits an uncertainty feedback parameterization of the control sequence and results in a tractable formulation of the problem. To improve on the efficiency of CL-RMPC we propose a new uncertainty feedback parameterization of the control input, which leads to a number of decision variables linear in time horizon as opposed to quadratic as in previous approaches. To assess our approach we compare three different robust optimal control strategies: nominal MPC which does not have a priori information of the uncertainty, OL-RMPC and CL-RMPC. We show results from a quantitative analysis of performance of these controllers at different prediction error values of the disturbance. Simulations show that CL-RMPC provides a higher level of comfort with respect to OL-RMPC while consuming 36% less energy. Moreover, CL-RMPC maintains perfect comfort level for up to 75% error in the disturbance prediction. Finally, the newly proposed parameterization maintains the performance of CL-RMPC while reducing the simulation time by an average of 30%.

Commentary by Dr. Valentin Fuster
2012;():267-273. doi:10.1115/DSCC2012-MOVIC2012-8586.

This paper discusses energy optimal point-to-point motion control for linear time-invariant (LTI) systems using energy-optimal Model Predictive Control (EOMPC). The developed EOMPC, which is based on time-optimal MPC, aims at performing energy-optimal point-to-point motions within a required motion time. Energy optimality is achieved by setting the object function of the EOMPC optimization problem equal to the system’s energy losses. The key issue is to utilize the strategy of the prediction horizon to ensure that the motion time is exactly equal to the required motion time. Application of EOMPC on a badminton robot shows the practical applicability of the developed method. In addition, an experimental comparison with time-optimal MPC is provided.

Commentary by Dr. Valentin Fuster
2012;():275-284. doi:10.1115/DSCC2012-MOVIC2012-8613.

This paper presents the design and simulation results of a model predictive controller (MPC) applied to the longitudinal dynamics of a lighter-than-air wind energy system being pioneered by Altaeros Energies. The unique Altaeros design features a traditional horizontal axis wind turbine that is held aloft by a buoyant shroud, which is tethered to a ground based platform. This structure provides access to strong, high-altitude winds, requires minimal setup, and builds upon proven aerostat components, making the system an attractive component in expanding wind energy throughout the world. However, because the system replaces a conventional tower with tethers, its dynamics are highly susceptible to variations in the wind. In particular, the control system must keep the shroud pitch angle and tether tensions within acceptable bounds in order to maintain stable operation and remain within structural limitations of the system. In this paper, we apply MPC to achieve desirable longitudinal system performance while simultaneously enforcing the constraints. We describe the longitudinal dynamic model of the system, detail the linear MPC design, and provide simulation results on both the linearized and nonlinear system for a variety of real-world wind conditions, including a Dryden turbulence model and data acquired from the Altaeros functional prototype test site at Loring Air Force Base in Limestone, Maine.

Commentary by Dr. Valentin Fuster
2012;():285-292. doi:10.1115/DSCC2012-MOVIC2012-8742.

A controller based on an adaptive generalized predictive control scheme for power-split in a simplified model of a diesel-electric hybrid vehicle is presented. The proposed controller gets an optimal partition of power between a diesel engine and an electric machine where parametric uncertainty and constraints on the input and output signals are considered. Simulation results are presented showing good performance of the adaptive predictive control over a driving cycle, maintaining good power tracking and meeting the constraints. The proposed controller has low computational cost.

Commentary by Dr. Valentin Fuster
2012;():293-301. doi:10.1115/DSCC2012-MOVIC2012-8822.

This paper presents a model predictive control based optimal feedforward tracking integrated with a robust repetitive feedback control aimed for generating complex engine piston profiles in non-circular engine piston turning using dual-stage long stroke linear motor/high bandwidth piezoelectric actuators. By formulating and solving receding horizon optimization, which explicitly takes into account practical constraints and specific dynamic capabilities of the dual-stage actuators integrated with repetitive feedback control, the methodology is demonstrated in simulation to precisely track fast oscillating but non-periodic reference signals derived from an industrial engine piston profile. In comparison, linear repetitive feedback control alone would violate dual-stage actuator constraints and as a result generate tracking errors 50 times larger than the proposed approach.

Commentary by Dr. Valentin Fuster
2012;():303-312. doi:10.1115/DSCC2012-MOVIC2012-8851.

In this paper, we present a model predictive controller to reduce road traffic congestion in freeway networks. The model predictive controller regulates traffic in the freeway through the use of ramp metering and variable speed limits. The controller uses a Link-Node Cell transmission model (LN-CTM) to represent freeway dynamics. We modify the standard LN-CTM to account for the capacity drop phenomenon, which is observed as a discontinuous decrease in flow throughput when traffic density exceeds a critical value. The resulting optimal control problem with a modified model, which accounts for the capacity flow phenomenon, is non-convex. We present heuristic restrictions on the solution trajectories, which allow us to solve the problem efficiently. This enables us to obtain the solution of the actual optimal control problem by solving a sequence of relaxed linear programs. We describe the procedure which can be used to map the optimal solution of this relaxed problem to the solution of the actual optimal control problem. Finally, we demonstrate the application of the model predictive controller on a simulated example, and discuss the characteristics of the controller.

Commentary by Dr. Valentin Fuster

Modeling and Model-Based Control of Advanced IC Engines

2012;():313-319. doi:10.1115/DSCC2012-MOVIC2012-8537.

Comparing to the air-path loop control, the fuel injection on Diesel engines is a fast control actuator in the realization of advanced combustion modes and the smooth transitions during combustion mode switchings. In this paper, given the estimated in-cylinder conditions (ICCs) at the crank angle of intake valve closing (IVC), models describing the relationship between the fuel injection split ratio and the combustion performance indices, such as CA50 and IMEP, are proposed and validated through experimental data obtained on a medium-duty Diesel engine. Such models can be potentially instrumental in systematic and cooperative control of air-path and fuel-path in the Diesel engine advanced combustion modes and the transient operations during combustion mode switching processes.

Commentary by Dr. Valentin Fuster
2012;():321-327. doi:10.1115/DSCC2012-MOVIC2012-8670.

This paper describes a control-oriented charge mixing and Homogeneous Charge Compression Ignition (HCCI) combustion model, where the in-cylinder charge is divided into the well-mixed and unmixed zones as the result of charge mixing. Simplified fluid dynamics is used to predict the residual gas fraction at the intake valve closing, which defines the size of the unmixed zone, during real-time simulations. The unmixed zone size not only determines how well the in-cylinder charge is mixed, which affects the start of HCCI combustion, the peak in-cylinder pressure and also the temperature during the combustion process. The developed model was validated in the HIL (hardware-in-the-loop) simulation environment. The HIL simulation results show that the proposed charge mixing and HCCI combustion model provides better agreement with these of the corresponding GT-Power than the previously developed one-zone model.

Commentary by Dr. Valentin Fuster
2012;():329-338. doi:10.1115/DSCC2012-MOVIC2012-8687.

Strict emissions constraints and interest in increasing engine efficiency are causing growing attention on advanced combustion strategies such as premixed charge compression ignition (PCCI) which can drastically lower particulate matter, and nitrogen oxide emissions. Control of PCCI requires an understanding of the underlying dynamics that govern the combustion process and can be challenging since there is no direct trigger for beginning the combustion process. In addition, the timing of the actual start of combustion (SOC) is affected by the in-cylinder conditions (such as temperature and pressure) as well as the fuel being utilized. This paper focuses on the development of a control-oriented physics-based model which predicts the SOC for diesel and biodiesel to within ±2°CA. Validation efforts demonstrate the effectiveness of the model in capturing SOC for multiple fuels and point to the strong role of in-cylinder oxygen content in influencing the SOC. A control framework which controls SOC through regulation of in-cylinder conditions is shown to be effective in controlling combustion phasing for both diesel and biodiesel in PCCI.

Commentary by Dr. Valentin Fuster
2012;():339-348. doi:10.1115/DSCC2012-MOVIC2012-8723.

Imprecisions from controller software implementation can substantially affect a controller’s performance for leading a physical plant to a desired behavior. In this paper, a discrete-time quasi-sliding mode approach is used to design a controller with improved robustness to software implementation imprecisions. The application of the controller is illustrated for automotive cold start hydrocarbon emissions. The designed controller shows more robustness with respect to implementation imprecisions including sampling, quantization and fixed-point arithmetic when compared to its continuous-time counterpart. In particular, the influence of the sampling time is investigated and a controller configuration with minimal computational requirements is proposed. Finally, the performance of the new controller is verified with real-time simulations.

Commentary by Dr. Valentin Fuster
2012;():349-358. doi:10.1115/DSCC2012-MOVIC2012-8730.

Engine control plays a crucial role in the sustained operation of turbofan engines which are complex nonlinear systems. As engines have evolved to higher capabilities it is essential to update the control strategy. Current baseline controllers house the min-max architecture consisting of individual limit controllers. In this paper the industrial baseline controller is replaced by a Model Predictive Control (MPC) law, a model based control technique that can handle complex constrained dynamics. This allows the incorporation of component faults in the control design, that occur during an engine’s operation due to wear and tear and foreign object ingestion affecting the engine performance. A multi-model MPC with on-line optimization is applied to a nonlinear turbofan engine in the presence of component faults, investigating the control of both, fan speed and thrust. Simulations are verified with C-MAPSS40k demonstrating the successful replacement of the baseline controller with an on-line fault tolerant MPC.

Commentary by Dr. Valentin Fuster
2012;():359-367. doi:10.1115/DSCC2012-MOVIC2012-8779.

This paper takes a first step towards model-based feedback control for the transition between spark ignition (SI) and homogeneous charge compression ignition (HCCI) combustion modes by approaching the transfer out of SI operation during the SI into HCCI transition in a closed-loop control framework. The combustion mode switch is taken to be directly from SI to HCCI without an intermediate combustion mode between the two, and the HCCI phase of the transition is not addressed. The transfer out of SI operation is formulated as a multi-input, multi-output control problem with input and output constraints. A baseline feedback controller for the transfer is designed using linear quadratic regulator methods, and is tested in simulation on a nonlinear mean value engine model. A simple open-loop transition based on look-up table set points is included as well for comparison. The feedback controller shows the ability to complete the SI phase of the transition in a short number of cycles, while maintaining a minimal disturbance to the engine torque in comparison to the open-loop controller.

Commentary by Dr. Valentin Fuster

Modeling and Simulation

2012;():369-375. doi:10.1115/DSCC2012-MOVIC2012-8607.

This paper examines the development of a linear single particle model that can be used for model based power train simulation, design, estimation and control in hybrid and electric vehicles. The model assumes that the cell consists of spherical particles in each electrode, neglects the electrolyte dynamics, and uses Padé approximations of the particle transcendental transfer functions. The Padé approximated single particle model matches well with the transcendental model, indicating the accuracy of 3rd order Padé approximations for the particle surface concentrations. This model also accurately reproduces the frequency response of a more complex model from the literature, showing that electrolyte diffusion has limited impact on cell impedance. The model also predicts the experimentally measured EIS and moderate (≤ 5C) current pulse charge/discharge of a 3.1 Ah Li-ion cell. The explicit form of the impedance allows the development of an equivalent circuit with resistances and capacitances related to the cell parameters.

Commentary by Dr. Valentin Fuster
2012;():377-383. doi:10.1115/DSCC2012-MOVIC2012-8642.

Modeling of compliant contact is an important issue for simulation and control of mechanical systems. Empirical results in the literature show that, in some mechanical systems such as biological tissues, the relation between the contact force and the indentation is characterized by the following three features: (i) continuity of the force at the time of collision, (ii) Hertz-like nonlinear force-indentation curve, and (iii) non-zero indentation at the time of loss of contact force. The conventional Hunt-Crossley (HC) model does not capture the feature (iii) as the model makes the contact force and indentation reach zero simultaneously. This paper proposes a compliant contact model based on a differential-algebraic equation that satisfies all the three features. The behaviors of the model and the effect of parameters in the model are investigated through numerical simulations.

Topics: Algebra
Commentary by Dr. Valentin Fuster
2012;():385-393. doi:10.1115/DSCC2012-MOVIC2012-8690.

In recent years two-wheeled inverted pendulums have been used as personal transporters. Their maneuverability and small footprint give them desirable properties for such function. However, they are intrinscally unstable and their safety as personal transporters has not been carefully assessed. Dynamic models of these transporters should be developed, and used to investigate failure conditions that would be difficult to safely test with a real machine and human operator. This paper describes the process involved in developing and calibrating such a model. A numerical model of one of these transporters (the Segway i2) was formed and its parameters were matched to the dynamic behavior observed in experimental tests.

Topics: Modeling , Testing , Pendulums
Commentary by Dr. Valentin Fuster
2012;():395-404. doi:10.1115/DSCC2012-MOVIC2012-8708.

A simplified electrochemical model of infinite order for electric double-layer capacitors is approximated through spatial semidiscretization. A family of reduced order models which are linear and time invariant, easy to analyze and implement, have few parameters and physical meaning is obtained. Three typical discretization methods are compared in time and frequency domains: finite difference, finite element and differential quadrature. In addition, two criteria to select the order of approximations are explored, one based on bandwidth and one on residue analysis. Differential quadrature based on polynomials proves to be the most accurate approximation, whereas the residue analysis criterion leads to lower order models. Finally, sufficient conditions to assure controllability and observability of the resulting lumped models are stated with the assumption of certain symmetry properties on the discretization matrices.

Topics: Capacitors
Commentary by Dr. Valentin Fuster
2012;():405-414. doi:10.1115/DSCC2012-MOVIC2012-8737.

A model for thermal behavior of a moving web transported over a heat transfer roller is developed in this paper. Heat transfer rollers are employed widely in roll-to-roll systems that contain processes such as printing, coating, lamination, etc., which require heating/cooling of the moving web material. The web is either cooled or heated by wrapping the moving web around the rotating heat transfer roller. The goal in such roll-to-roll processes is to transport the web over heating/cooling rollers at a specified web tension and transport velocity, and web tension in the material is affected by mechanical strain and thermal strain in the web. Temperature distribution in the moving web is needed to determine thermal strain. A general one-dimensional heat transfer model is used for describing the heat transfer process in the moving web material and the outer shell of the heat transfer roller. Based on this model, the temperature distribution in the web in the region of wrap on the heat transfer roller and in the free span are obtained by considering appropriate boundary conditions and initial conditions. Model simulations are conducted to determine the temperature profile in the web wrapped on a heat transfer roller; simulations are also conducted for a portion of an embossing line which contains heat transfer rollers. The model simulation results are compared with a limited amount of measured data available on a production embossing line.

Commentary by Dr. Valentin Fuster
2012;():415-421. doi:10.1115/DSCC2012-MOVIC2012-8857.

The problem of model reference predictive control for eliminating contaminant cloud from a pipe fluid system by boundary control action is addressed. A lab-scale pipe fluid system prototype is developed for studying the control of fluid system. Experimental results validate the possibility of eliminating the contaminant cloud by boundary control. A model reference control architecture is constructed, in which a parameterizable reduced order mathematical model for simulating fluid particle path-lines is developed. Compared to traditional Computational Fluid Dynamics (CFD) method, this reduced order model can be solved within very short time by common Ordinary Differential Equation (ODE) solver which enables the implementation of iterative optimal control.

Commentary by Dr. Valentin Fuster

Multi-Agent and Cooperative Systems

2012;():423-429. doi:10.1115/DSCC2012-MOVIC2012-8534.

This paper is concerned with the decentralized formation control of multi-agent systems moving in the plane. Using a single-integrator agent model, we propose a new distributed control law to asymptotically stabilize the inter-agent distance error dynamics. Our approach exploits the infinitesimal and minimal rigidity of the undirected graph that models the formation. A Lyapunov-based analysis shows that these two properties are necessary conditions for asymtptotic stability. The control, which is explicitly dependent on the graph rigidity matrix, is derived for a class of potential functions.

Commentary by Dr. Valentin Fuster
2012;():431-438. doi:10.1115/DSCC2012-MOVIC2012-8788.

This work presents a cyclic pursuit model based on non-linear inter-agent interactions driven by double-integrator dynamics. Cyclic pursuit models, beginning with the famous “Three-Bug problem”, have spurred a strong interest in the research community, encompassing linear and non-linear control models, synchronous and asynchronous pursuit and other similar variants and extensions. Much of the work, however, has been towards the development of kinematic pursuit models. Double-integrator models with directed interactions such as in cyclic pursuit models present strong challenges in the evaluation of the system stability and the emergence of global dynamic attributes based on local non-linear agent interactions. This work proposes and evaluates a control model based on a particular form of agent interactions involving linear attractive and non-linear repulsive forcing functions, directed from each agent to its leading agent along the pursuit curve. Specifically, the non-linear controller enforces a stricter implementation of collision avoidance among agents during pursuit, allowing for a reversal in pursuit direction when inter-agent separations drop to low values. Starting from arbitrary initial conditions for the multi-agent system, the emergence of stable cyclic pursuit configurations purely from local agent interactions is demonstrated. The proposed work has strong potential in co-operative perimeter-tracking applications such as wildfire monitoring and border patrol, where the need for efficient spatial distribution of agents around perimeters while in pursuit is essential for efficient data gathering and developing improved situational awareness for dynamic events.

Commentary by Dr. Valentin Fuster
2012;():439-448. doi:10.1115/DSCC2012-MOVIC2012-8831.

In this paper a continuum approach for controlling the motion of a swarm of particles (“agents”) is presented. The control objective is to move the swarm from an initial reference configuration to a final configuration possibly of a different shape and size, avoid obstacles and inter-agent collisions while satisfying hard constraints on agent kinematics. The agents are considered to be inside a rectangle and it is assumed that the task is to move the swarm so that at the final time the agents are confined to a rectangle of possibly different size and orientation. It is shown that the agents can locally control their motions so that a collision free transfer respecting all agent constraints can be achieved with minimal inter-agent communication. At the nucleus of this approach is the “deformation of the group shape from a given reference configuration to a desired configuration”. The key idea is to find an appropriate homeomorphism between the initial and final configurations that respect all agent constraints. We show that a class of homogeneous transformations has very beneficial attributes. In particular, each particle or agent has a well-defined path that is based solely on its reference position. It necessarily means that an agent does not have to know the location of any other agent once the motion map is made available to an agent. We emphasize: (1) that minimum to no communication between agents is required for its implementation, and (2) it is independent of the number of agents, meaning that the approach is completely scalable. These two attributes are major advantages that are not present in most currently known path planners for swarms. Presented will be simulation results to illustrate the key ideas of the proposed approach.

Commentary by Dr. Valentin Fuster
2012;():449-456. doi:10.1115/DSCC2012-MOVIC2012-8844.

In this paper, we present coordination algorithms for an heterogeneous robotic group consisting of a mobile manipulator and a number of mobile sensing agents to cooperatively estimate a toxic field and trace its maximum point. In particular, we treat the mobile manipulator as a master machine and mobile sensing agents as slave machines such that, at the converged configuration, the end effector of the manipulator can reach the maximum point. The unknown field has been modeled by a network of radial basis functions and mobile robots are coordinated by flocking and gradient control algorithms based on their estimated fields. A simulation study demonstrates the validity of the proposed scheme in an industrial disaster or emergency scenario.

Commentary by Dr. Valentin Fuster
2012;():457-466. doi:10.1115/DSCC2012-MOVIC2012-8853.

The teleoperation systems involving cooperative multi-robots to cope with different tasks on a single target with a team of homogeneous robots have been developed with (1) modified potential field based leader-follower formation, (2) adaptive multi-robotic impedances, (3) compensation for contact forces. However, most of the homeland security applications, e.g. military reconnaissance, exploration, and etc, need a team of heterogeneous robots to work on the multi-task simultaneously on the multi-target with a robot-task-target pairing. Therefore, the main contribution of this paper is to propose the cooperative teleoperation control method integrating not only (1–3) but also the robot-task-target pairing for a multi-robot multi-task multi-target defensive application.

The robot-task-target pairing is derived from the proven auction algorithm for multi-robot multi-task multi-target cases, which optimizes effects-based robot-task-target pairing based on a heuristic algorithm. The pairing method for the robot-task-target pairing is developed to produce a weighted attack guidance table (WAGT), which includes the benefits of assignments of robotic combinations (subteams) to tasks and targets. Therefore, the optimal robot-task-target pairs are computed based on WAGT with the heuristic algorithm. Simulation studies illustrate the efficacy of the teleoperation system with the proposed control method for multi-task multi-target scenarios.

Topics: Robotics
Commentary by Dr. Valentin Fuster
2012;():467-471. doi:10.1115/DSCC2012-MOVIC2012-8871.

A nonlinear modeling framework is presented for autonomous cruise control (ACC) equipped vehicles which allows one to analyze car-following scenarios in a wide range of velocities and headways. By designing the range policy as well as the controller one can improve the ride qualities for individual vehicles and increase the throughput of the overall traffic systems.

Topics: Modeling
Commentary by Dr. Valentin Fuster

Musculoskeletal Dynamic Systems

2012;():473-482. doi:10.1115/DSCC2012-MOVIC2012-8556.

Passive joint compliance is a key feature of the human hand that plays an important role in realizing dexterous, precise and graceful movements. Our goal is to study the role of passive compliance in the human hand joints and develop ways for implementing human-like passive compliance in a robotic form. While a variety of factors influence joint stiffness in a tendon-driven system the focus of this paper is on investigating the effects of variation in moment arms, defined by the joint shape, on the joint stiffness characteristics. We present a method for analyzing the effects of variable moment arms on the joint stiffness variations and a mathematical technique to synthesize joint shapes based on the stiffness requirements. We study the role of variable passive stiffness by analyzing energy consumption and dynamic response with system models. We validate our theoretical results in shape synthesis with an experimental platform involving a single degree of freedom tendon driven joint. The analysis and results of our work have implications in the design of various robotic systems, including robotic hands, that seek to incorporate human-like joint stiffness characteristics.

Topics: Stiffness , Tendons
Commentary by Dr. Valentin Fuster
2012;():483-492. doi:10.1115/DSCC2012-MOVIC2012-8592.

The presented work addresses the implementation of Functional Electrical Stimulation (FES) into a closed-loop control system as a means of rehabilitation for patients with spinal cord injury (SCI). FES is a neuroprothesis technique applied to reinnervate the motor function in affected muscles. In clinical settings, FES is applied via an open-loop system which is not an efficient approach. Therefore, this study focuses on experimentally applying two model-free feedback controllers: a Proportional-Integral (PI) controller and a Model Reference Adaptive Control (MRAC) algorithm. A comparative study evaluating these controllers is carried out in vitro mimicking the knee-joint tracking system. The experimental setup is composed of a muscle-mass-spring system where the muscle is stimulated while forces are measured and the muscle position is tracked. Thus, the muscle’s instantaneous position is used as feedback signal. Consequently, the effectiveness of both controllers is evaluated to develop improved strategies for the system’s tracking.

Topics: Feedback , Muscle
Commentary by Dr. Valentin Fuster
2012;():493-502. doi:10.1115/DSCC2012-MOVIC2012-8593.

Haptic devices require physical contact between operator and machine, using force feedback and creating a coupled system. Human contact reduces stability due to the response of human operators to stiffen the arm to stabilize the system, leading to a less stable system. Controllers cannot account for this, as operator stiffness is not measurable. This research examined the decreased stability due to increased operator arm stiffness and designed a system to compensate by providing the controller with additional information about the environment. Operator arm stiffness was estimated by measuring muscle activity using EMGs, then the dynamic characteristics of an impedance controller were adjusted according. The design is discussed and experimentally validating, showing increased stability and higher performance. Based on the results, an advanced probabilistic model of operator actions is explored for its applicability to enhance the system. Such a system could be used in many applications, including force assisting devices in industrial facilities.

Commentary by Dr. Valentin Fuster
2012;():503-510. doi:10.1115/DSCC2012-MOVIC2012-8595.

In an effort to better understand the human head-neck target tracking response, we have developed a procedure for designing a robustly optimal experimental configuration for system identification. This configuration is comprised of a parametrized input sequence along with physical parameters for the experiment. We have developed both nominal and experimental models containing uncertainties for the target tracking task based on several preliminary experimental data sets, and identified a feasible population of subject controller parameters. We applied a min-max optimization scheme to minimize a performance cost over the feasible experimental configurations, while simultaneously maximizing it over the population of subject controller parameters. In this way, a minimum level of design performance for any subject within the defined population can be guaranteed. We show that in the worst-case, the performance cost is 0.473 in flexion/extension, and 0.122 in axial rotation.

Commentary by Dr. Valentin Fuster
2012;():511-517. doi:10.1115/DSCC2012-MOVIC2012-8683.

Functional electrical stimulation (FES) is an effective rehabilitation tool for gait retraining for individuals suffering from various neurological disorders. Traditionally, FES is only delivered to activate ankle dorsiflexor muscles during the swing phase of the gait to correct “foot drop”. Recent research indicates that improved functional ambulation can be achieved by delivering FES to both the plantarflexor and dorsiflexor muscles during gait. Closed-loop electrical stimulation has the potential to yield positive rehabilitative outcomes by enabling accurate and precise limb motions during gait retraining. Naturally, the motion of ankle during gait is an event-driven system combining continuous evolution of the angle between the foot and shank, alternate moving segments of the foot and shank, and alternate activation of the plantarflexor and dorsiflexor muscles. A switched sliding mode based controller is developed to ensure that the ankle tracks a designed or recorded normal trajectory during gait which can be used for gait retraining. Semi-global asymptotic tracking of the hybrid controller is analyzed using multiple Lyapunov functions and the performance is illustrated through simulations.

Commentary by Dr. Valentin Fuster
2012;():519-528. doi:10.1115/DSCC2012-MOVIC2012-8847.

Neuromuscular electrical stimulation (NMES) is a technique that is widely used as a tool for rehabilitation and restoration of basic functions for people suffering from upper motor neuron lesion (UMNL). Closed-loop methods have shown a potential for improving the effectiveness of NMES. In this paper, uncertainties in the muscle contraction dynamics are taken into consideration when compensating for the muscle contraction dynamics. Accounting for the muscle contraction dynamics is a challenge because of uncertainty, nonlinearity and the fact that the contraction states are not measurable. A neural-network (NN)-based controller together with a dynamic NN-based identifier is designed to enable semi-global uniformly ultimately bounded tracking of a desired limb trajectory and on-line estimation of the limb acceleration. The overall stability of the identifier-controller system is analyzed through Lyapunov methods. Simulation results are provided to illustrate the controller performance.

Commentary by Dr. Valentin Fuster

Nano Systems

2012;():529-534. doi:10.1115/DSCC2012-MOVIC2012-8548.

Electroosmosis is a low-cost actuation methodology for micro- and nanofluidic systems including lab-on-chip technologies. Potential applications include transport and analysis of DNA, RNA, proteins, vaccines, antibiotics, and a range of other molecules at the micro- and nanoscales. Fields of application range from microbiology, biochemistry, and medicine to genetics. This paper develops new control-oriented frequency-response models for thin rectangular channels that, for example, relate applied voltage to flow rate. These are 2D models, which can be approximated with simple first-order responses whose bandwidth can be expressed in terms of the fundamental actuator parameters of solution density and viscosity and channel height. The DC response is characterized largely by channel height, viscosity, permittivity, and the zeta-potential (ζ-potential), which is the electrical potential in the solution at the channel walls.

Commentary by Dr. Valentin Fuster
2012;():535-541. doi:10.1115/DSCC2012-MOVIC2012-8660.

In this paper, a controller featuring cross-coupled control and iterative learning control schemes is designed and implemented on a modular two-axis positioning system in order to improve both contour and tracking accuracy. Instead of using the standard contour estimation technique proposed with the variable gain cross-coupled control, a computationally efficient contour estimation technique is incorporated with the presented control design. Moreover, implemented contour estimation technique makes the presented control scheme more suitable for arbitrary nonlinear contours. Effectiveness of the control design is verified with simulations and experiments on a two-axis positioning system. Also, simulations demonstrating the performance of the control method on a three-axis positioning system are provided. The resulting controller is shown to achieve nanometer level contouring and tracking performance. Simulation results also show its applicability to three-axis nano-positioning systems.

Commentary by Dr. Valentin Fuster
2012;():543-552. doi:10.1115/DSCC2012-MOVIC2012-8661.

This paper presents a new method to increase the available measurement resolution of quadrature encoder signals. The proposed method features an adaptive signal correction phase and an interpolation phase. Typical imperfections in the encoder signals including amplitude difference, mean offsets and quadrature phase shift errors are corrected using recursive least squares with exponential forgetting and resetting. Interpolation of the corrected signals are accomplished by a quick access look-up table formed offline to satisfy a linear mapping from available sinusoidal signals to higher order sinusoids. The position information can be derived from the conversion of the high-order sinusoids to binary pulses. With the presented method, 10nm resolution is achieved with an encoder having 1μm of original resolution. Further increase in resolution can also be satisfied with minimizing electrical noises. Experiment results demonstrating the effectiveness of the proposed method for a single axis and two axis slider systems are given.

Commentary by Dr. Valentin Fuster
2012;():553-560. doi:10.1115/DSCC2012-MOVIC2012-8701.

In order to enable the high-speed control of scanning probe microscopes (SPMs), a model of the SPM nanopositioner must typically be acquired. Modeling of SPM systems is difficult due to issues with external nanoposition sensor resolution, integration, and availability. In order to overcome these problems, a method capable of finding a model of the SPM nanopositioner using only the SPM’s existing imaging capabilities is presented. In this method, images acquired using a known spiral input trajectory are analyzed to determine the amplitude and phase of the output signal, which can be used to determine the magnitude and phase of a transfer function model. The method is presented, followed by simulations and preliminary experiments that show the validity of the approach.

Commentary by Dr. Valentin Fuster
2012;():561-565. doi:10.1115/DSCC2012-MOVIC2012-8757.

This paper exemplifies methods to estimate sample properties, including topographical properties, from a high bandwidth estimate of tip-sample interaction forces between the probe tip and the sample surface in an atomic force microscope. The tip-sample interaction force is the most fundamental quantity that can be detected by the probe tip. The fact that sample features as well as physical properties of the sample are a function of tip-sample interaction model chosen is exploited, and the property estimates are obtained by fitting appropriate physical models to the force estimate data. The underlying idea is to treat the non-linear tip-sample interactions as a disturbance to the cantilever subsystem and design a feedback controller that ensures the cantilever deflection tracks a desired trajectory. This tracking allows scanning speeds as high as 1/10th of the cantilever resonance frequency compared to typical scanning modes that regulate derivatives of the probe deflection such as amplitude or phase, providing much lower scan speeds. The high bandwidth disturbance rejection and consequent estimation provides estimates of the tip-sample interaction force.

Commentary by Dr. Valentin Fuster
2012;():567-573. doi:10.1115/DSCC2012-MOVIC2012-8848.

In this paper, we present significant improvements to a scanning probe microscope (SPM) modeling technique that uses the SPM’s probe-surface interaction signal to model the lateral dynamics of the SPM. The fundamental idea behind this modeling method is to use the topography signal resulting from a sinusoidal scan of a known calibration surface to develop a transfer function model of the AFM dynamics. This method is useful in situations where sensors are either unavailable, insufficient, or require independent calibration. The method is experimentally implemented to model a commercial atomic force microscope system (AFM).

Commentary by Dr. Valentin Fuster

Nonlinear Systems

2012;():575-579. doi:10.1115/DSCC2012-MOVIC2012-8581.

The performance enhancement of a reverse osmosis (RO) unit through periodic control is studied by manipulating the feed pressure and the flow rate. To ensure the periodic behavior of the inputs, the manipulated variables (MV) are transformed into sinusoidal functions. In this case, the amplitude and the period of the sinusoidal functions become the surrogate MV and are regulated via nonlinear model predictive control algorithm. It was clear from the simulation results that the control system can generate cyclic inputs necessary to enhance the closed-loop performance by increasing the permeate production and lowering the salt concentration. The proposed control system can achieve its objective with arbitrary set point for the controlled outputs. It is important to note that reliable results were obtained even in the presence of modeling errors.

Topics: Reverse osmosis
Commentary by Dr. Valentin Fuster
2012;():581-589. doi:10.1115/DSCC2012-MOVIC2012-8612.

This paper addresses performance enhancement using disturbance observers for a class of hysteresis nonlinearities. The proposed approach makes use of internal model-based estimation of exogenous disturbances. The synthesis is then formulated as an H weighted-sensitivity optimization for static output feedback (SOF) gain of a Luenberger observer. A sequential linear programming approach is then implemented to solve the bilinear-matrix-inequality (BMI) constrained semi-definite program (SDP) for the (sub)optimal static gain. Simulation results indicate that tracking performance is indeed enhanced using the DOB at different excitation frequencies in the closed loop control system.

Commentary by Dr. Valentin Fuster
2012;():591-596. doi:10.1115/DSCC2012-MOVIC2012-8724.

A nonlinear robust observer has been developed by combining the advantages of the variable structure systems (VSS) theory with those of the self-tuning fuzzy logic algorithm. The observer does not require an exact knowledge of the system dynamics or the construction of a rule-based expert fuzzy inference system. Instead, it requires the upper bounds on the modeling imprecision to be known. The observer design involves the derivation of inequality conditions that must be satisfied by the tuning parameters in order to ensure the convergence of the estimation process.

The observer has been applied to estimate the state variables of an under-actuated marine vessel. The simulation results demonstrated the capabilities of the observer in providing accurate estimates of the state variables in spite of considerable modeling imprecision and significant environmental disturbances.

Commentary by Dr. Valentin Fuster
2012;():597-606. doi:10.1115/DSCC2012-MOVIC2012-8778.

An application and experimental verification of the online structure from motion (SFM) method is presented to estimate the position of a moving object using a moving camera. An unknown input observer is implemented for the position estimation of a moving object attached to a two-link robot observed by a moving camera attached to a PUMA robot. The velocity of the object is considered as an unknown input to the perspective dynamical system. Series of experiments are performed with different camera and object motions. The method is used to estimate the position of the static object as well as the moving object. The position estimates are compared with ground-truth data computed using forward kinematics of the PUMA and the two-link robot. The observer gain design problem is formulated as a convex optimization problem to obtain an optimal observer gain.

Commentary by Dr. Valentin Fuster
2012;():607-616. doi:10.1115/DSCC2012-MOVIC2012-8849.

A method for calculating all periodic solutions and their domains of attraction for flexible systems under nonlinear feedback control is presented. The systems considered consist of mechanical systems with flexible modes and a relay type controller coupled with a linear control law, operating in a feedback configuration that includes a time delay. The proposed approach includes three steps. First, limit cycle frequencies and periodic fixed points are computed exactly, using a block diagonal state-space modal representation of the plant dynamics. Then the relay switching surface is chosen as the Poincare mapping surface and is discretized using the cell mapping method. Finally, the region of attraction for each limit cycle is computed using the cell mapping algorithm and employing an error based convergence criterion. An example consisting of a model of a flexible system, a relay with hysteresis, a linear control law, and a pure time delay is used to demonstrate the proposed approach.

Commentary by Dr. Valentin Fuster
2012;():617-624. doi:10.1115/DSCC2012-MOVIC2012-8866.

The conservation of momentum can be useful in designing control laws for underactuated mechanical systems. However, the momentum is conserved only for unactuated variables with symmetry. If a symmetry-breaking force is applied to a system, the momentum is not conserved any longer in general. The main objective of this paper is to show that there exist forces linear in velocity such as the damping force that break the symmetry but induce a new conserved quantity in place of the original momentum map. This paper formalizes that such a new conserved quantity can be constructed by combining the time integral of a general damping force and the original momentum map associated with the symmetry. Especially, we show that the new conserved quantity can exist for multiple variables with symmetry. From the perspective of stability theories, the major implication of the new conserved quantity is that the corresponding variables possess the self recovery phenomenon, i.e. they will be globally attractive to the initial condition of the variables. What is fundamental in the damping-induced self recovery is not the positivity of the damping coefficient but certain properties of the time integral of the damping force. Self recovery effect and theoretical findings are demonstrated by simulation results using a two-link manipulator and a planar pendulum. The results in this paper will be useful in designing and controlling mechanical systems with underactuation.

Topics: Damping
Commentary by Dr. Valentin Fuster

Nonlinear Systems and Control

2012;():625-634. doi:10.1115/DSCC2012-MOVIC2012-8508.

The concept of Lyapunov exponents is a powerful tool for analyzing the stability of nonlinear dynamic systems especially when the mathematical models of the systems are available. However, for real world systems, such models are often unknown, and estimating these exponents reliably from experimental data is notoriously difficult. A novel method of estimating Lyapunov exponents from a time series is presented in this paper. The method combines the ideas of reconstructing the attractor of the system under study and approximating the embedded attractor through tuning a Radial-Basis-Function (RBF) network, which facilitates the derivation of the Jacobian matrices for applying the model-based algorithm. Simplified as a two-link inverted pendulum with one additional rigid foot-link, a standing biped with a Linear Quadrtic Regulator (LQR) is selected as a case study. The biped balance system has a spectrum including four negative Lyapunov exponents, of which the high numerical accuracy derived through the newly proposed method can be guaranteed even in presence of the measurement noise. We believe that the work can contribute to the stability analysis of nonlinear systems of which the dynamics are either unknown or difficult to model due to complexities.

Commentary by Dr. Valentin Fuster
2012;():635-643. doi:10.1115/DSCC2012-MOVIC2012-8611.

This paper deals with the problem of synthesizing feedforward control to aid the regulation of output of a nonlinear system in the presence of partially known exogenous inputs. Currently known methods for this problem either require the solution of a constrained partial differential equation or the preview information of the signal to be tracked. The novelty of this paper lies in synthesizing feedforward control as the solution of an algebraic - differential equation, which is considerably less complex. The techniques developed in this paper generalize very directly to nonlinear systems governed by differential-algebraic equations. In this paper, we consider two separate problems: the problem of tracking reference signals and the problem of regulating the output while rejecting the disturbances. We assume that the disturbance and the reference signals are outputs of known exogenous systems. Furthermore, we assume that the initial conditions for the exogenous system corresponding to the reference signals are known while those for the exogenous system corresponding to disturbances are unknown. We develop a parameter identification scheme to estimate the unknown initial conditions for the exogenous system in the case of output regulation. We illustrate the effectiveness of the control schemes for tracking problem with the example of a ball and beam system, and for the disturbance attenuation problem with two examples, nonlinear vibration absorber and a rotational translational actuator.

Commentary by Dr. Valentin Fuster
2012;():645-652. doi:10.1115/DSCC2012-MOVIC2012-8644.

In this work, we develop a new control design approach to deal with saturated polynomial nonlinear systems by using higher order Lyapunov functions. By combining power transformation with Sum-of-Squares (SOS) techniques, we can augment the systems with more state variables representing higher order combinations of the original ones. Then, the search of higher order Lyapunov functions for original systems can be recast to the design of quadratic Lyapunov functions for augmented systems. By computing for higher order Lyapunov functions using norm-bounded differential inclusion (NDI) LMI conditions, the flexible representations of augmented systems can help us to achieve better performance than quadratic based method. Two examples illustrate the improvements to enlarge the region of attraction and to improve the ℋ performance for nonlinear systems subjected to saturation nonlinearity, respectively.

Commentary by Dr. Valentin Fuster
2012;():653-660. doi:10.1115/DSCC2012-MOVIC2012-8664.

In this paper we propose a new method for the design of an output feedback controller for a helicopter which is an uncertain, input-nonaffine, Multi-Input-Multi-Output (MIMO), nonlinear system. By combining dynamic inversion control together with extended high-gain observer, our output feedback controller is able to bring the trajectories of the closed-loop system arbitrarily close to that of a given target system. The conditions applicable to a helicopter model for dynamic inversion control are obtained. The proposed method is illustrated by simulation.

Topics: Design
Commentary by Dr. Valentin Fuster
2012;():661-670. doi:10.1115/DSCC2012-MOVIC2012-8665.

Finite-time stability involves dynamical systems whose trajectories converge to an equilibrium state in finite time. In various tasks that the real world systems have to perform, the execution time is critical, and thus, it is important to enforce that the system trajectories that converge to a desired state do so in finite time. In this paper, we consider a general class of fully actuated mechanical systems described by Euler-Lagrange dynamics and the class of underactuated systems represented by mobile robot dynamics that are required to reach and maintain the desired trajectory in finite time. Specifically, we develop feedback controllers using sliding mode approach that guarantee finite-time tracking. The approach is based on designing non-smooth sliding surfaces such that, while on the sliding surface, the error states converge to the origin in finite time thus ensuring finite-time tracking. We demonstrate the efficacy of our approach by implementing it for a scenario when multiple dynamic agents are required to move in a fixed formation with respect to the formation leader.

Commentary by Dr. Valentin Fuster
2012;():671-675. doi:10.1115/DSCC2012-MOVIC2012-8786.

We present a general formulation for estimation of the region of attraction (ROA) for nonlinear systems with parametric uncertainties using a combination of the polynomial chaos expansion (PCE) theorem and the sum of squares (SOS) method. The uncertain parameters in the nonlinear system are treated as random variables with a probability distribution. First, the decomposition of the uncertain nonlinear system under consideration is performed using polynomial chaos functions. This yields to a deterministic subsystem whose state variables correspond to the deterministic coefficient components of the random basis polynomials in PCE. This decomposed deterministic subsystem contains no uncertainty. Then, the ROA of the deterministic subsystem is derived using sum of squares method. Finally, the ROA of the original uncertain nonlinear system is derived by transforming the ROA spanned in the decomposed deterministic subsystem back to the original spatial-temporal space using PCE. This proposed framework on estimation of the robust ROA (RROA) is based on a combination of PCE and SOS and is specially useful, with appealing computation efficiency, for uncertain nonlinear systems when the uncertainties are non-affine or when they are associated with a specific probability distribution.

Topics: Chaos , Polynomials
Commentary by Dr. Valentin Fuster

Optimal Control

2012;():677-686. doi:10.1115/DSCC2012-MOVIC2012-8546.

Process control for vacuum arc remelting is a challenging and interesting problem that has captured the attention of the metallurgy and control communities for decades. The main goal of the process is the production of homogeneous ingots with an appropriate chemistry, physical size, and grain structure. Traditionally, this process has been controlled by applying a desired current to the furnace expecting to control the solidification profile and, therefore, the microstructure of the ingot. It is believed that the final ingot grain microstructure is strongly influenced by the molten metal pool profile. Thus, if pool profile was controlled during the melt then defect-free microstructures would be obtained. However, there was no controller capable of performing such a task. The recent development of a reduced-order model of solidification in vacuum arc remelting allowed the design of the first pool profile controller. A Linear-Quadratic-Gaussian (LQG) controller was designed to account for inaccuracies in the reduced-order model and the measurements. Simulation and experimental results show the accurate performance of the controller.

Commentary by Dr. Valentin Fuster
2012;():687-694. doi:10.1115/DSCC2012-MOVIC2012-8604.

This paper presents a method for optimizing the machining parameters in rough turning processes to control the vibrations and deformations and minimize the production time per component under practical constraints. The optimization model is formulated, in which piecewise constraints are introduced based on the varying length-to-diameter (L/D) ratio of the workpiece. The optimization problem is solved in two phases. The first phase is to determine the minimum production time for each cutting pass for preset equal-spaced depths of cut. A hybrid solver of combining a genetic algorithm (GA) and sequential quadratic programming (SQP) technique is adopted. In the second phase, a dynamic programming (DP) technique is employed to achieve the optimal production time per component and sequential subdivision of the total depth of cut. An example illustrates the method in detail. The inclusion relation of the solutions is also discussed.

Commentary by Dr. Valentin Fuster
2012;():695-701. doi:10.1115/DSCC2012-MOVIC2012-8713.

Given a set of targets that need to be monitored and a vehicle, we consider a combinatorial motion planning problem where the objective is to find a path for the vehicle such that each target is visited at least once by the vehicle, the path satisfies the motion constraints of the vehicle and the length of the path is a minimum. This is an NP-hard problem and currently, there are no algorithms that can find an optimal solution to this problem. In this article, we model the motion of the vehicle as a Dubins car and develop a method that can provide tight lower bounds to the motion planning problem. We accomplish this by relaxing the constraints corresponding to the angle of approach at each of the targets and then penalizing them whenever they are violated. The solution to the Lagrangian relaxation gives a lower bound, and this lower bound is maximized over the penalty variables using subgradient optimization. The proposed method is the first of its kind for finding tight lower bounds for combinatorial motion planning problems and can be extended to similar problems with more general motion constraints.

Topics: Vehicles , Computation
Commentary by Dr. Valentin Fuster
2012;():703-709. doi:10.1115/DSCC2012-MOVIC2012-8802.

Based on a bivariate spline representation of United States Geological Survey (USGS) digital elevation model (DEM) data, the brachistochrone on a 2D curved surface without friction was solved numerically using dynamic and control models in MATLAB® in conjunction with the Spline Toolbox for surface modeling. This extends in a natural manner previous work by several of the authors (Hennessey and Shakiban) on both the 1D and 2D curved surface brachistochrone using optimal control and resulting in a two-point boundary value problem. DEM data permits an accurate representation of the surface in question (30 m resolution data for Lone Mountain in MT) and the Spline Toolbox provides a sufficiently smooth version of the surface, including access to spatial partial derivatives needed in the minimum-time control law. Step-by-step results are reported, including the surface representation details, the minimum-time route & travel time, evaluation of the generalized k = 1 Legendre-Clebsch optimality condition, and comparison with competing routes, namely the constant yaw rate and constant bearing angle routes.

Commentary by Dr. Valentin Fuster
2012;():711-718. doi:10.1115/DSCC2012-MOVIC2012-8862.

To effectively control vapor compression cycle (VCC) systems whose dynamics are highly nonlinear, it is necessary to develop plant models and control laws for different operating regions. This paper presents a first-principles modeling framework that captures four operation modes over the operating envelope to construct an invariant-order switched system. To synthesize a multi-input multi-output (MIMO) control system, the Linear Quadratic Regulator (LQR) technique is framed as a control optimization problem with Linear Matrix Inequality (LMI) constraints which can be simultaneously solved for the set of considered linear systems. Stability and performance characteristics of the controlled system are guaranteed using a common quadratic Lyapunov function. Simulation results in a case study show that the LMI-based controller can maintain system operation at optimal set-points with mode switching over a wide operating envelope.

Commentary by Dr. Valentin Fuster

Pattern Recognition and Intelligent Systems

2012;():719-725. doi:10.1115/DSCC2012-MOVIC2012-8554.

In this paper we present a simple heuristic approach to localize and estimate the parameters of unknown threat sources by use of kinematically constrained sensing robots. Since the distributed sensor robots cannot always be guided by a human it becomes imperative to impart decision making ability to the robots so they navigate themselves through the area of interest to determine the most information about the threats. We achieve this by using the current data collected by robots to generate a rough estimate of the threat parameters via a nonlinear least squares fit of the data collected by robots. We assume that the threat’s dispersion surface can be represented by a superposition of radial basis functions. We develop and test a heuristic algorithm for moving the robots to improve our surface estimate. In general, this requires some of the robots to move towards each of the threat sources while exploring area between these sources. As the motion progresses we update and improve our estimate of the threat surface thus allowing us to refine the paths of the robots for additional data collection. This approach is studied in detail with extensive simulations and results are presented. Our goal is to most efficiently recover the parameters of the threat surface within the least time.

Commentary by Dr. Valentin Fuster
2012;():727-735. doi:10.1115/DSCC2012-MOVIC2012-8667.

The paper proposes an approach to intelligent control of dynamic systems integrating prediction and optimization capabilities of brain-like intelligence in a noisy, unknown and uncertain environment. A new hierarchical learning architecture based on adaptive dynamic programming (ADP) and reinforcement learning (RL) is considered utilizing the information of the system interactions with the environment or situation awareness. The situation information is represented in form of a reinforcement signal generated by a reference module within the framework of the adaptive critic design (ACD). The action and critic modules in ACD are generally implemented using traditional multilayer perceptron (MLP) type artificial neural networks (ANN). In this paper, an alternative form of ANN, namely, single multiplicative neuron (SMN) model is considered in place of MLP for representing action, critic and reference modules. The network modules are trained using a variation of particle swarm optimization. The effectiveness of the proposed approach is illustrated through a realistic nonlinear ship dynamics model in heading control.

Topics: Dynamic systems
Commentary by Dr. Valentin Fuster
2012;():737-742. doi:10.1115/DSCC2012-MOVIC2012-8678.

This paper presents a pattern classification method based on sparse representation. This new method bypasses the need for feature extraction and selection that are typically presented in the conventional classification methods, and performs classification using raw sensor signals directly. The performance of this new method is evaluated in the context of human physical activity assessment. Experimental results obtained from 105 human subjects demonstrate higher discriminative power than using the conventional k-nearest neighbor algorithm, verifying the effectiveness of the sparse representation method.

Commentary by Dr. Valentin Fuster
2012;():743-750. doi:10.1115/DSCC2012-MOVIC2012-8725.

It has been shown that a set of multi-input (electrothermal and thermofluidic inputs) Shape Memory Alloy (SMA) actuators implemented into a Network Array Architecture (NAA) and treated like binary actuators can be represented by graph theory, such that the actuator configurations are represented as graph nodes, and transitions between states as graph edges. However, to achieve a desired actuation, a set of sequential control commands is required. A search algorithm was originally developed to identify a set of sequential control commands to go from a start node to a destination node with minimum path cost, where the cost function is a weighted combination of actuation time and energy. The original algorithm only considered one destination at a time, optimizing the present cost with no regard to any future costs. The aim of the current work is to modify the existing algorithm to control these SMA actuator arrays over a trajectory (multi-destination search problem), and take advantage of future destination knowledge to optimize the path cost. To achieve this goal, a sub-search algorithm and modified performance function are developed. For each heating control command, the sub-search algorithm compiles required information from future nodes. Then, this information is used by the modified performance function to estimate the future path cost. The modified performance function is designed to estimate the future path cost, while computing the current path cost. Therefore, the modified performance function will identify the sequence of operations with a minimum total path cost. The results show that the modified algorithm has a total path cost that is up to 30% less than the original algorithm total cost.

Commentary by Dr. Valentin Fuster
2012;():751-760. doi:10.1115/DSCC2012-MOVIC2012-8749.

This research investigates a novel data driven approach to condition monitoring of Electro-Mechanical Actuators (EMAs) consisting of feature extraction and fault classification. The approach is able to accommodate time-varying loads and speeds since EMA’s typically operate under non-steady conditions. The feature extraction process exposes fault frequencies in signal data that are synchronous with motor position through a series of signal processing techniques. A resulting reduced dimension feature is then used to determine the condition of the EMA with a trained Bayesian Classifier. Signal data collected from EMAs in known health configurations is used to train the algorithms so that the condition of EMA’s with unknown health may be predicted. Although the process was developed for EMAs, it can be used generically on other rotating machine applications as a Health and Usage Management System (HUMS) tool.

Commentary by Dr. Valentin Fuster
2012;():761-770. doi:10.1115/DSCC2012-MOVIC2012-8758.

This paper presents a novel approach to find patterns in vehicle x-y-z acceleration data for use in prognostics and diagnostics. In this problem, vehicles are assumed to travel on the same routes and often times as a part of convoys but their GPS and other position information has been removed for privacy reasons. The goal of the pattern matching scheme is to identify the route or convoy associations within vehicles by using the acceleration data collected onboard these vehicles. A crucial step in solving this problem is to choose the right feature vector, as raw matching of acceleration signals is inappropriate due to different velocities, driving behaviors, vehicle loading, etc. In this paper, we demonstrate the feasibility of using ‘Multi-Scale Extrema Features’ for this application. The paper also addresses implementation details to enhance performance for in-vehicle acceleration data, corrupted by different sources of noise. A novel ‘Multi-Scale Encoding’ method is also proposed for the above feature vector and it leads to a significant improvement in the performance over traditional pattern matching methods. While the main focus of the paper is towards identifying feature vectors that effectively describe in-vehicle acceleration data, the feature vector could potentially be used with acceleration data obtained from other applications.

Topics: Vehicles , Time series
Commentary by Dr. Valentin Fuster

Power and Renewable Energy Systems

2012;():771-778. doi:10.1115/DSCC2012-MOVIC2012-8558.

Linear parameter varying (LPV) control of a three-bladed horizontal-axis wind turbine in partial and full load conditions using FAST code is presented. The multivariable LPV controller is designed for a lumped model of the wind turbine with five degrees-of-freedom consisting blades, drive-train and the tower. The controller is scheduled in real-time based on the mean wind speed. The objective is to minimize the H performance index from the wind turbulence to the controlled output vector. The closed-loop responses of the LPV controller are compared with a traditional PI-scheduled controller in the FAST/Simulink environment for the NREL 5MW baseline wind turbine. Compared to the PI-scheduled controller, the LPV design reduced the transient loads in switching between partial to full load regions of the operation. The fluctuations of the generator speed and torque are decreased resulting in a smoother power generation. The wind turbine structural loads in terms of blade root flap-wise bending moments and tower fore-aft bending moment are mitigated in different loading conditions.

Topics: Wind turbines
Commentary by Dr. Valentin Fuster
2012;():779-783. doi:10.1115/DSCC2012-MOVIC2012-8682.

In this contribution a new developed load profile prediction and control optimization approach is applied for a fuel cell/supercap-based hybrid powertrain, whose electrical components are arranged in a Range extender topology. The load profile prediction is based upon past track information. Dependent on the prediction performance, using a variable horizon length, this algorithm can be adapted. The prediction algorithm is combined with a control optimization approach, which is based on a Hamiltonian problem. Hereby the nonlinear dynamic models of the powertrain and the criteria for the optimization of different system properties for a considered time interval are included. The approach is applied both as Model Predictive Controller (MPC) and Dynamic Programming (DP) algorithm. The results show that using this approch a significant improvement of the performance with respect to efficiency, availability, and component lifetime can be obtained in relation to other approaches and also to previous results of the authors.

Commentary by Dr. Valentin Fuster
2012;():785-791. doi:10.1115/DSCC2012-MOVIC2012-8740.

Smart grid has generated much attention recently due to its potential in bringing a revolutionary change in the production, distribution, and utilization of electric power. However, before a smart grid can become fully functional, it requires technological advancements in a number of interdisciplinary domains. Even though smart grid facilitates run-time optimal allocation of power via extensive instrumentation and information accessibility, the process of optimal power allocation becomes challenging due to the massively distributed generation facilities, loads, and due to the intermittency of generation. In this paper, a Market Based technique has been presented to solve the DC optimal power flow problem in a smart grid. The DC optimal power flow problem aims at determining the power generated at each station and voltage angles associated with each bus in the transmission system. The Market Based Resource Allocation is inspired from the concepts in economic market, where resources are allocated to activities through the process of competitive buying and selling. In the proposed technique, every bus in the system acts as a potential power buyer and/or seller. The proposed method derives its significance due to its ability in optimizing power flow in a grid in a distributed manner, i.e., from local interactions. This feature provides immense scalability and robustness to uncertainties. In addition, this paper presents the evaluation of the proposed Market Based technique via a number of simulated scenarios of power consumers and producers in a Smart Grid. The IEEE 30-bus system with six generation units is used to test the proposed method in optimizing the total generation cost, and the results are compared with that obtained from widely used Matpower software.

Topics: Flow (Dynamics)
Commentary by Dr. Valentin Fuster
2012;():793-801. doi:10.1115/DSCC2012-MOVIC2012-8787.

Using state-of-the-art engine technologies, current gasoline internal combustion engines of passenger vehicles convert only 25∼35% of fuel energy into useful power, and 65∼75% of fuel energy are wasted as heat through engine cooling and exhaust gas systems. One of the promising technologies that can dramatically improve fuel economy is the waste heat recovery system using Organic Rankine Cycle (ORC). The working fluid of the ORC, however, undergoes both liquid and gas phases throughout the cycle, and it is a challenge to develop heat exchanger models that can be used in a simple and efficient dynamic ORC model. In this study, a simplified ordinary differential equation (ODE) ORC model is developed for system-level design and control studies. First, the first principles model of heat exchange dynamics is described by two partial differential equations (PDE) and one ODE, and then the moving-boundary approach is used to lump the distributed parameters of the heat exchanger by integrating three governing equations over each length of three phases (gas, two-phase, and liquid). The simulation results demonstrate that the proposed dynamic ORC model provides key transient dynamics of the ORC with much less computational load.

Commentary by Dr. Valentin Fuster
2012;():803-812. doi:10.1115/DSCC2012-MOVIC2012-8792.

This paper develops a nonlinear control system for grid frequency stabilization using the setpoint temperature control of a large number of air conditioning loads. The paper’s ultimate goal is to develop a feedback control law for the demand-side energy management of air conditioning loads, relying on grid frequency measurement only. To achieve this goal, we first integrate the dynamics of aggregated thermostatically-controlled air conditioning loads and grid frequency, and then use the Lyapunov theory to derive a robust sliding mode controller for the system. Both theoretical derivations and numerical simulations show that the developed controller is able to stabilize the grid frequency against disturbances such as sudden loss of load or supply, as well as wind power generation. We envision that the proposed control scheme can be used to build a new class of frequency-responsive air conditioning systems with inherent robustness in their collective performance.

Commentary by Dr. Valentin Fuster
2012;():813-822. doi:10.1115/DSCC2012-MOVIC2012-8815.

This paper presents a novel method of capturing more energy from the wind using short term energy storage in a hydrostatic wind turbine. A hydrostatic transmission not only provides reliable operation but also enables robust energy management features like energy regeneration using hydraulic accumulators. In this study, turbulence-induced wind power transients occurring near rated power are exploited to extract more energy from the wind. Wind characteristics are analyzed to develop models to quantify the potential energy loss due to wind turbulence and energy gains from short term storage. A control strategy to achieve the above objective is proposed. A mathematical model for a proposed energy storage configuration is developed in MATLAB/Simulink. Results show that in a 50 kW mid-size wind turbine, the Annual Energy Production (AEP) can be increased by nearly 4% with a 60 liter accumulator.

Commentary by Dr. Valentin Fuster

Powertrain Systems

2012;():823-831. doi:10.1115/DSCC2012-MOVIC2012-8585.

Recent work in the area of Homogenous Charge Compression Ignition (HCCI) engine control has focused on the use of variable valve timing (VVT) as a near term implementation strategy. Control of valve timing has a significant influence on combustion phasing and can be implemented with cam-based VVT systems already available in production vehicles. However, cam-based VVT systems pose a challenge by introducing cylinder coupling via a shared actuator. This paper presents a Model Predictive Control (MPC) framework that explicitly accounts for this inter-cylinder coupling as a constraint on the system. The prediction time step of this MPC controller differs from the execution time step, enabling consideration of shared actuation among otherwise independent systems. Experimental results on a multi-cylinder HCCI engine test bed provide validation of this controller.

Commentary by Dr. Valentin Fuster
2012;():833-838. doi:10.1115/DSCC2012-MOVIC2012-8638.

A new automatic gear-shift control system is designed for fixed shaft manual transmission, exceeding the process of traditional gear-shifting and achieving gear-shift control without the disengagement of the clutch. The process to achieve the vision is described based on analyzing the process of traditional gear-shifting, using the integrated control methods and strategies. Finally the feasibility and advantage for this control method is validated through vehicle road test.

Topics: Gears
Commentary by Dr. Valentin Fuster
2012;():839-845. doi:10.1115/DSCC2012-MOVIC2012-8652.

This paper presents a computationally efficient Multi-Objective Dynamic Programming (MODP) algorithm. The algorithm is applied to obtain the optimal supervisory control for PHEVs to minimize two objectives — total CO2 emissions and operational dollar costs to an individual PHEV owner. The algorithm integrates the concept of crowding distance from the Multi-Objective Evolutionary Algorithms (MOEA) literature. This distance metric is used to refine the optimal Pareto front at every time step for each state discretization. The refinement of the Pareto front significantly reduces the computational time and memory required for MODP, making it feasible. At the same time, the results show that the refinement retains optimality and produces a Pareto front with a good spread ranging from one extremal point to the other. The results also reveal interesting insights for the tradeoffs that can be achieved in minimizing the CO2 emissions and cost objectives for the underlying grid mix and driving conditions assumed.

Commentary by Dr. Valentin Fuster
2012;():847-856. doi:10.1115/DSCC2012-MOVIC2012-8796.

Over the past several decades numerous hybrid electric (HE) configurations have been researched and developed for various vehicle applications. The origination of HE vehicle concepts resulted in many new research directions in vehicle dynamics and control and vehicle system design. However, vehicle driveline systems, which distribute power between the drive wheels, have not yet been included in the area of interest nor researched for their potential contribution to the HE power transformation.

This paper presents a work in a new proposed direction, specifically fusion of the HE power conversion process with optimization of power distribution between the drive wheels. A new principle is proposed to optimize power distribution between the front and rear wheels and to minimize slip power losses in tires by maintaining equal tire slippages and, thus, reducing energy consumption; wheel power optimization is algorithmically integrated with the mechanical-electrical-mechanical power conversion in a 4×4 terrain vehicle with a series HE powertrain.

Commentary by Dr. Valentin Fuster
2012;():857-865. doi:10.1115/DSCC2012-MOVIC2012-8818.

This paper presents a systematic design methodology for split hybrid vehicles using a single planetary gearset (PG) as the transmission. The design methodology consists of four steps: 1) analyze clutch locations on the PG and operation modes, 2) generate dynamic models, 3) evaluate drivability (acceleration performance) via forward simulations, and 4) optimize the fuel economy using the dynamic programming technique. The 1-PG split hybrid transmission can have 12 configurations, and each configuration can have four operation modes when three clutches are added. This methodology systematically evaluates all configuration candidates and identifies the optimal design, and we demonstrate how it helps to identify a simplified design based in the output-split configuration used by the Chevy Volt. The simplified design, named the Volt, has only two of the four operation modes of the original Volt. The Volt achieves the same fuel economy as the original Volt in the FUDS cycle, and has only slightly reduced drivability and fuel economy in the HWFET cycle. In addition, an improved design based on the input-split configuration used by the Toyota Prius is also identified, named the Prius+, which has one additional mode than the original Prius. The Prius+ outperforms the Prius in both drivability and fuel economy.

Commentary by Dr. Valentin Fuster
2012;():867-876. doi:10.1115/DSCC2012-MOVIC2012-8856.

The main focus of this paper will be on the modeling of a simulated Intake Airflow Simulator (IAS), a patented device that can manipulate the gas dynamics of the intake plenum of an internal combustion engine, with the use of proportional and poppet pneumatic valves that operate in parallel with each other. The goal of the IAS, with regard to the Powertrain Control Research Laboratory (PCRL), is to simulate a multi-cylinder’s intake air gas dynamics on a single-cylinder research engine that is unique to the PCRL. This paper will include background of the technology developed in the PCRL, the methodology behind, current work, results obtained, conclusions inferred, and references used to model and control the simulated IAS [1].

Commentary by Dr. Valentin Fuster

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