ASME Conference Presenter Attendance Policy and Archival Proceedings

2013;():V002T00A001. doi:10.1115/DSCC2013-NS2.

This online compilation of papers from the ASME 2013 Dynamic Systems and Control Conference (DSCC2013) 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to ASME’s conference presenter attendance policy, if a paper is not presented at the Conference, the paper will not be published in the official archival Proceedings, which are registered with the Library of Congress and are submitted for abstracting and indexing. The paper also will not be published in The ASME Digital Collection and may not be cited as a published paper.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

Control, Monitoring, and Energy Harvesting of Vibratory Systems: Analysis and Passive Control

2013;():V002T18A001. doi:10.1115/DSCC2013-3811.

Axially moving continua such as belt, chain, and conveyer are common transmission components. The study of the vibration response of axially moving continua is an essential topic to understand the fundamentals of vibration and improve the performance of the machines. However, it typically requires more rigorous effort in mathematical derivation to obtain the analytical forced vibration responses of the axially moving continua because of the characteristics of non-self-adjoint equation of motion. The methods utilized to obtain the analytical solutions include the modal analysis, canonical form, wave propagation, Laplace transform, and transfer function. In this review paper, these methods will be reviewed and presented. The advantages and disadvantages of different methodologies are discussed as well.

Topics: Vibration
Commentary by Dr. Valentin Fuster
2013;():V002T18A002. doi:10.1115/DSCC2013-3861.

This paper proposes two types of novel Tuned Multi-mass Dampers (TMMD), namely Unequally-divided TMMD (UTMMD) and Wired TMMD (WTMMD).

It is widely known that the TMMD made of plural identical tuned mass dampers (TMDs) achieves higher vibration suppression effect than a single big TMD. In this study, the idea of UTMMD made of plural unequal TMDs is presented and its vibration suppression effect is explored numerically. It is clarified that the vibration suppression effect of UTMMD is essentially the same as that of TMD, while the robustness might be slightly improved.

Meanwhile, the extension of the stroke of TMD is an important issue. WTMMD is another novel TMMD made of an auxiliary mass connected with two small auxiliary masses via wires for each. In this study, an experimental structure and WTMMD is built, and vibration suppression property of WTMMD is investigated experimentally. The WTMMD showed satisfactory vibration suppression performance.

Commentary by Dr. Valentin Fuster
2013;():V002T18A003. doi:10.1115/DSCC2013-3922.

This paper deals with electrostatically actuated Carbon Nano-Tubes (CNT) cantilevers using Reduced Order Model (ROM) method. Forces acting on the CNT cantilever are electrostatic, van der Waals, and damping. The van der Waals forces are significant for values of 50 nm or lower of the gap between the CNT and the ground plate. As both forces electrostatic and van der Waals are nonlinear, and the CNT electrostatic actuation is given by AC voltage, the CNT undergoes nonlinear parametric dynamics. The Method of Multiple Scales (MMS), and ROM are used to investigate the system under soft excitations and/or weak nonlinearities. The frequency-amplitude and frequency-phase behaviors are found in the case of parametric resonance.

Commentary by Dr. Valentin Fuster
2013;():V002T18A004. doi:10.1115/DSCC2013-3976.

The tapping mode (TM) is a popularly used imaging mode in atomic force microscopy (AFM). A feedback loop regulates the amplitude of the tapping cantilever by adjusting the offset between the probe and sample; the image is generated from the control action. This paper explores the role of the trajectory of the tapping cantilever in the accuracy of the acquired image. This paper demonstrates that reshaping the cantilever trajectory alters the amplitude response to changes in surface topography, effectively altering the mechanical sensitivity of the instrument. Trajectory dynamics are analyzed to determine the effect on mechanical sensitivity and analysis of the feedback loop is used to determine the effect on image accuracy. Experimental results validate the analysis, demonstrating better than 30% improvement in mechanical sensitivity using certain trajectories. Images obtained using these trajectories exhibit improved sharpness and surface tracking, especially at high scan speeds.

Commentary by Dr. Valentin Fuster
2013;():V002T18A005. doi:10.1115/DSCC2013-4006.

Real structures are always subject to uncertainties due to material imperfection, machining tolerance, and assemblage error, etc. These uncertainties lead to variations in structural vibratory responses. In order to reduce the likelihood of unexpected failures in structures, we need to minimize the response variations, which is the underlying idea of robust design. In this paper, we present an inverse sensitivity-based algorithm that allows us to tailor the structural design such that, under the same level of uncertainties, the response variations can be effectively reduced. We first develop a direct relation between the structural uncertainties and the response variations including the means and variances. We then formulate an optimal identification algorithm that will yield design perturbation to minimize the response variances while maintaining the mean values. Case analyses are carried out to validate the validity and efficiency of the new algorithm.

Commentary by Dr. Valentin Fuster
2013;():V002T18A006. doi:10.1115/DSCC2013-4058.

This paper presents an improvement of a nonlinear piezoelectric impedance modulation (NPIM)-based damage detection method, a damage-sensitive, baseline-free structural health monitoring technique proposed by the authors, by introducing self-excited oscillation. The NPIM-based damage detection utilizes the modulation of high-frequency wave field of structures caused by the contact acoustic nonlinearity at the damaged part. In this study, the high-frequency wave field is induced as a self-excited oscillation of the structure by positively feed-backing the strain signal measured by a surface-bonded piezoelectric sensor, followed by a phase-shift in 90 degrees and a nonlinear element consisting of a saturation element and a negative linear gain. The induced self-excitation can have multiple stable limit cycles at certain eigenmode frequencies, and one can switch among them by inputting an auxiliary excitation signal into the feedback loop. The current flowing through the piezoelectric sensor is measured to detect its modulation due to the stiffness fluctuation due to the existence of the contact-type damage. Experiments using a specimen with a simulated damage are conducted to examine the performance of the self-excitation circuit and its applicability to the NPIM-based damage detection method.

Commentary by Dr. Valentin Fuster

Control, Monitoring, and Energy Harvesting of Vibratory Systems: Energy Harvesting

2013;():V002T19A001. doi:10.1115/DSCC2013-3757.

Ocean wave energy is an indirect form of solar energy with great potential worldwide. Technologies on extracting energy from the ocean wave have been explored for centuries and are still undergoing with challenges. The nature of ocean wave and ocean wave energy are introduced with their mathematical models in this paper. The features and working principles of three forms of mainstream ocean wave energy converters (OWEC), including floating bodies (point absorber, attenuator, and terminator), oscillating water column (OWC) and wave overtopping, are presented together with their hydrodynamic performances. The corresponding control methodologies for these ocean wave energy converters, such as latching control, declutch control, reactive control, model predictive control (MPC), etc., are analyzed in a comprehensive manner thereafter. Optimal conditions for maximum power absorption are also introduced with mathematical modeling and derivations.

Topics: Ocean energy
Commentary by Dr. Valentin Fuster
2013;():V002T19A002. doi:10.1115/DSCC2013-3758.

This paper presents a novel approach to damage identification in a class of collocated multi-input multi-output structural systems. In the proposed approach, damage is identified via the structural Markov parameters obtained from a system identification procedure, which is in turn exploited to localize and quantify damage by evaluating relative changes occurring in the mass and stiffness matrices associated with the structural system. To this aim, an explicit relationship between structural Markov parameters versus mass and stiffness matrices is developed. The main strengths of the proposed approach are that it is capable of quantitatively identifying the occurrence of multiple damages associated with both mass and stiffness characteristics in the structural system, and it is computationally efficient in that it is solely based on the structural Markov parameters but does not necessitate costly calculations related to natural frequencies and mode shapes, making it highly attractive for structural damage detection and health monitoring applications. Numerical examples are provided to demonstrate the validity and effectiveness of the proposed approach.

Commentary by Dr. Valentin Fuster
2013;():V002T19A003. doi:10.1115/DSCC2013-3780.

A vibration energy harvester is typically composed of a spring–mass system, with the advantage of high energy density, simple structure and easily being miniaturized. Recently, effects of cantilever beam’s structural parameters and cross-section shape on energy-harvesting micro-device is concerned and investigated in this paper, so as to study its performance of energy harvesting to meet the needs of low resonant frequency and maximum output power. The effect of a cantilever beam’s structure dimensions as well as quality of the mass on the device’s resonance frequency and maximum output power can be detected through formula computing. Further study on effect of a cantilever beam’s cross-section shape has also been worked out. According to the simulation experimental results gained from ANSYS with appropriate parameters defined by theoretical derivation, we manage to receive concordant conclusions. To receive a better performance of the energy harvester, we should choose a shorter, wider and thicker cantilever beam with rectangular cross-section and heavier mass at its end. However, to meet the requirement of low resonant frequency for piezoelectric vibration energy harvesting, we still need to define either an upper or a lower limit while choosing parameters of the device.

Commentary by Dr. Valentin Fuster
2013;():V002T19A004. doi:10.1115/DSCC2013-3804.

The energy harvesting system of piezoceramic plate is studied on the electrode configuration to improve the electromechanical transferring efficiency. The piezoceramic plate is used to perform the vibration characteristics by experimental measurements and finite element method (FEM). Thereafter, the dynamic characteristics and the electromechanical coupling efficiency of the piezoelectric energy harvesting system are studied by the electrode design method of the piezoceramic plate. Several experimental techniques are used to measure the dynamic characteristics of piezoceramic plate. First, the full-filed optical technique, amplitude-fluctuation electronic speckle pattern interferometry (AF-ESPI), can measure simultaneously the resonant frequencies and mode shapes for out-of-plane and in-plane vibrations. Second, the pointwisely measuring system, laser Doppler vibrometer (LDV), can obtain resonant frequencies by dynamic signal swept-sine analysis. Third, the correspondent in-plane resonant frequencies and anti-resonant frequencies are obtained by impedance analysis. The experimental results of vibration characteristics are verified with numerical calculations. Besides the dynamic characteristics of piezoceramic plates are analyzed in converse piezoelectric effect, the direct piezoelectric effect of piezoceramic plates are excited by shaker to generate the electric voltage. It has excellent consistence between resonant frequencies and mode shapes on the vibration characteristics by experimental measurements and finite element numerical calculations. In this study, the Electrical Potential Gradient (EPG) calculated by FEM is proposed to evaluate the electromechanical coupling efficiency of piezoceramic plate on the specific vibration mode. The correspondent electrode configuration, which is designed by EPG, can produce the best electromechanical transfer both in direct and converse piezoelectric effects. It is concluded that the vibration characteristics of piezoelectric materials have excellent consistence determined by experimental measurements and FEM.

Commentary by Dr. Valentin Fuster
2013;():V002T19A005. doi:10.1115/DSCC2013-3864.

In addition to the wide range of applications of stochastic resonance in the field of signal processing, the phenomenon has also been investigated as an effective tool for enhancing vibrational energy harvesting. This paper proposes a hypothetical method for achieving stochastic resonance and increasing the available energy from external ambient vibration. In order to illustrate this proposal, a bistable mechanical system is proposed to study the feasibility by theoretical analysis. The amount of available energy and the energy consumed to produce the small-scale additional force is analyzed through numerical simulations. It is shown that the proposed method can significantly enhance the harvested vibrational energy.

Commentary by Dr. Valentin Fuster
2013;():V002T19A006. doi:10.1115/DSCC2013-4101.

A variable electromotive-force generator (VEG), which is a modified generator with an adjustable overlap between the rotor and the stator, is proposed to improve the efficiency and/or expand the operational range of a conventional generator, with particular applications to wind turbines, hybrid vehicles, and so on. A mathematical model of the VEG is developed, and a novel prototype is designed and fabricated. The performance of the VEG with the active control system, which adjusts the overlap ratio based on the desired output power at different input speeds, is theoretically and experimentally studied. The results show that reducing the overlap between the rotor and the stator of the generator at low speeds results in a reduced torque loss of the generator and an increased rotational speed of the generator rotor.

Commentary by Dr. Valentin Fuster

Cooperative and Networked Control

2013;():V002T20A001. doi:10.1115/DSCC2013-3742.

We consider the problem of optimal coverage with area-constraints in a mobile multi-agent system. For a planar environment with an associated density function, this problem is equivalent to dividing the environment into optimal subregions such that each agent is responsible for the coverage of its own region. In this paper, we design a continuous-time distributed policy which allows a team of agents to achieve a convex area-constrained partition of a convex workspace. Our work is related to the classic Lloyd algorithm, and makes use of generalized Voronoi diagrams. We also discuss practical implementation for real mobile networks. Simulation methods are presented and discussed.

Commentary by Dr. Valentin Fuster
2013;():V002T20A002. doi:10.1115/DSCC2013-3778.

This paper investigates bandwidth allocation of networked control systems (NCSs) with nonlinear-programming techniques. The bandwidth utilization (BU) is defined in terms of sampling frequency. An exponential approximation is formulated to describe system performance versus the sampling frequencies. The optimal sampling frequencies are obtained by solving the approximation with Karush-Kuhn-Tucker (KKT) conditions. Simulation and experimental results verify the effectiveness of the proposed approximation. The exponential approximation can minimize the BU so that the plants can be scheduled along with the system PIFs being optimized.

Commentary by Dr. Valentin Fuster
2013;():V002T20A003. doi:10.1115/DSCC2013-3846.

Motivated by applications in which a nonholonomic robotic vehicle should sequentially hit a series of waypoints in the presence of stochastic drift, we formulate a new version of the Dubins vehicle traveling salesperson problem. In our approach, we first compute the minimum expected time feedback control to hit one waypoint based on the Hamilton-Jacobi-Bellman equation. Next, minimum expected times associated with the control are used to construct a traveling salesperson problem based on a waypoint hitting angle discretization. We provide numerical results illustrating our solution and analyze how the stochastic drift affects the solution.

Commentary by Dr. Valentin Fuster
2013;():V002T20A004. doi:10.1115/DSCC2013-3940.

A recent trend in networked control systems (NCSs) is the use of wireless networks enabling interoperability between existing wired and wireless systems. One of the major challenges in these wireless NCSs (WNCSs) is to overcome the impact of the message loss that degrades the performance and stability of these systems. Moreover, this impact is greater when dealing with burst or successive message losses. This paper discusses and presents the experimental results of a compensation strategy to deal with this burst message loss problem in which a NCS mathematical model runs in parallel with the physical process, providing sensor virtual data in case of packet losses. Running in real-time inside the controller, the mathematical model is updated online with real control signals sent to the actuator, which provides better reliability for the estimated sensor feedback (virtual data) transmitted to the controller each time a message loss occurs. In order to verify the advantages of applying this model-based compensation strategy for burst message losses in WNCSs, the control performance of a motor control system using CAN and ZigBee networks is analyzed. Experimental results led to the conclusion that the developed compensation strategy provided robustness and could maintain the control performance of the WNCS against different message loss scenarios.

Topics: Control systems
Commentary by Dr. Valentin Fuster
2013;():V002T20A005. doi:10.1115/DSCC2013-4034.

Radar deception problems serve as a motivation to address the key issue of feasibility in trajectory planning for constrained dynamics of multi-agent systems. In a recent paper, Jayasuriya et al. presents an algorithm which claims to produce a dynamically feasible reference trajectory in real time. However, there was no proof provided for the proposed control strategy. This paper work through that algorithm; and, with a slight modification, provides some conditions on configuration parameters and the desired trajectory such that the proposed control guarantees consensus. These conditions dictate certain conditions on the initial configuration of the agents, consistent with the limitations on their actuators. Simulations support the idea that if the initial configuration along the final team goal is in admissible regions, the agents would always reach a consensus and maintain the formation.

Topics: Phantoms , Radar
Commentary by Dr. Valentin Fuster
2013;():V002T20A006. doi:10.1115/DSCC2013-4041.

A hybrid intelligent algorithm is proposed. The algorithm utilizes a particle swarm and a Tabu search algorithm. Swarm based algorithms and single agent based algorithms each, have distinct advantages and disadvantages. The goal of the presented work is to combine the strengths of the two different algorithms in order to achieve a more effective optimization routine. The developed hybrid algorithm is tailored such that it has the capability to adapt to the given cost function during the optimization process. The proposed algorithm is tested on a set of different benchmark problems. In addition, the hybrid algorithm is utilized for solving the estimation problem encountered for estimating the finger force output given a surface electromyogram (sEMG) signal at the input. This estimation problem is commonly encountered while developing a control system for a prosthetic hand.

Commentary by Dr. Valentin Fuster

Delay Systems

2013;():V002T21A001. doi:10.1115/DSCC2013-3703.

It has been shown that the stability of LTI time-delayed systems with respect to the delays can be analyzed in two equivalent domains: (i) delay space (DS) and (ii) spectral delay space (SDS). Considering a broad class of linear time-invariant time delay systems with multiple delays, the equivalency of the stability transitions along the transition boundaries is studied in both spaces. For this we follow two corresponding radial lines in DS and SDS, and prove for the first time in literature that they are equivalent. This property enables us to extract local stability transition features within the SDS without going back to the DS. The main advantage of remaining in SDS is that, one can avoid a non-linear transition from kernel hypercurves to offspring hypercurves in DS. Instead the potential stability switching curves in SDS are generated simply by stacking a finite dimensional cube called the building block (BB) along the axes. A case study is presented within the report to visualize this property.

Topics: Stability , Delays
Commentary by Dr. Valentin Fuster
2013;():V002T21A002. doi:10.1115/DSCC2013-3812.

The effect of time delays on the stability of a recently proposed continuum approach for controlling a multi agent system (MAS) evolving in n-D under a special local inter-agent communication protocol is considered. There a homogenous map determined by n+1 leaders is learned by the follower agents each communicating with n+1 adjacent agents. In this work both position and velocity information of adjacent agents are used for local control of follower agents whereas in previous work [1, 2] only position information of adjacent agents was used. Stability of the proposed method under a time delay h is studied using the cluster treatment of characteristic roots (CTCR) [3]. It is shown that the stability of MAS evolution can be preserved when (i) the velocity of any follower agent is updated using both position and velocity of its adjacent agents at time (t-h); and (ii) the communication matrix has real eigenvalues. In addition, it is shown that when there is no communication delay, deviations from a selected homogenous map during transients may be minimized by updating only the position of a follower using both position and velocity of its adjacent agents.

Commentary by Dr. Valentin Fuster
2013;():V002T21A003. doi:10.1115/DSCC2013-3860.

This paper deals with the problem of active vibration suppression using the concept of delayed resonator with acceleration feedback. A complete dynamics analysis of the resonator and its coupling with a single degree of freedom mechanical system are performed. It is shown that due to presence of a delay in the derivative feedback, the dynamics of the resonator itself, as well as the dynamics of its coupling with the system are of neutral character. Subsequently, the spectral approach is used to obtain the stability boundaries in the space of the resonator parameters. Both, analytical and numerical methods are employed in the analysis. As the contributions, we display a methodology to determine the resonator parameters in order to guarantee desirable functioning of the resonator and to provide safe stability margins. An example is included to demonstrate these analytical results.

Topics: Stability , Design , Feedback
Commentary by Dr. Valentin Fuster
2013;():V002T21A004. doi:10.1115/DSCC2013-3878.

Co-simulating distributed hardware-in-the-loop systems in real time over the Internet entails communication delays that can lead to significant loss of fidelity and even instability in the system. To address this challenge, this paper proposes an observer based framework that, unlike previously reported efforts, does not require the observer to know and model the observed system dynamics. This is achieved by deriving the closed-loop dynamics of the observer based on a sliding surface. Even though the resulting error system does not necessarily stay on a sliding surface, its asymptotic convergence to zero is still guaranteed. First, this idea is developed for a generic networked system simulation framework and its stability is established. Then, it is applied to a mass-spring-damper system to illustrate the mechanics of the approach on a simple, linear example and demonstrate that the approach can stabilize the system that is otherwise unstable due to delay. Finally, a vehicle-engine-driver system simulation is considered to evaluate the performance of the approach on a more realistic, nonlinear example. An improvement of up to 33% is observed in the fidelity of the simulation. The conclusion is that the approach holds a significant potential to alleviate the negative impact of delay and improve the stability and fidelity of networked system simulations. Its benefits become more pronounced as the delay increases.

Commentary by Dr. Valentin Fuster
2013;():V002T21A005. doi:10.1115/DSCC2013-3952.

Various models have been proposed to estimate the undeformed thickness of chips produced by a CNC milling tool, in order to calculate the forces acting on the tool. The choice of model significantly affects the simulated dynamics of the tool, thereby affecting the dynamic stability of the simulated process and whether or not chatter occurs in a given cutting scenario. Simulations of the dynamics of the milling process can be used to determine the conditions at which chatter occurs, which can lead to poor surface finish and tool damage. The dynamics of a traditional model and a more detailed numerical model are simulated here with particular emphasis on the differences in their chatter bifurcation points. High-speed, low-radial-immersion milling processes are simulated because of their application in industrial high-precision machining.

Commentary by Dr. Valentin Fuster
2013;():V002T21A006. doi:10.1115/DSCC2013-4020.

A class of LTI consensus network dynamics with heterogeneous agent coupling strengths and homogeneous inter-agent delays is under investigation. An approach to design the graph Laplacian of the system is developed here for achieving fast consensus, departing from the analytical study of the rightmost eigenvalue behavior of this dynamics. Detailed design procedure is presented with a demonstrative example.

Topics: Design , Couplings , Delays
Commentary by Dr. Valentin Fuster

Dynamical Modeling and Diagnostics in Biomedical Systems

2013;():V002T22A001. doi:10.1115/DSCC2013-3708.

Communication between specialized regions of the brain is a dynamic process allowing for different connections to accomplish different tasks. While the content of interregional communication is complex, the pattern of connectivity (i.e., which regions communicate) may lie in a lower dimensional state-space. In epilepsy, seizures elicit changes in connectivity, whose patterns shed insight into the nature of seizures and the seizure focus. We investigated connectivity in 3 patients by applying network-based analysis on multi-day subdural electrocorticographic recordings (ECoG). We found that (i) the network connectivity defines a finite set of brain states, (ii) seizures are characterized by a consistent progression of states, and (iii) the focus is isolated from surrounding regions at the seizure onset and becomes most connected in the network towards seizure termination. Our results suggest that a finite-dimensional state-space model may characterize the dynamics of the epileptic brain, and may ultimately be used to localize seizure foci.

Commentary by Dr. Valentin Fuster
2013;():V002T22A002. doi:10.1115/DSCC2013-3726.

In an effort to establish an initial step towards the ultimate goal of developing an analytic tool to optimize the vasopressor-inotrope therapy through individualized dose-response relationships, we propose a phenomenological model intended to reproduce the hemodynamic response to vasopressor-inotropes. The proposed model consists of a cardiovascular model relating blood pressure to cardinal cardiovascular parameters (stroke volume and total peripheral resistance) and the phenomenological relationships between the cardinal cardiovascular parameters and the vasopressor-inotrope dose, in such a way that the model can be adapted to individual patient solely based upon blood pressure and heart rate responses to medication dosing. In this paper, the preliminary validity of the proposed model is shown using the experimental epinephrine dose versus blood pressure and heart rate response data collected from five newborn piglets. Its performance and potential usefulness are discussed. It is anticipated that, potentially, the proposed phenomenological model may offer a meaningful first step towards the automated control of vasopressor-inotrope therapy.

Commentary by Dr. Valentin Fuster
2013;():V002T22A003. doi:10.1115/DSCC2013-3881.

The occurrence and risk of recurrence of brain related injuries and diseases are difficult to characterize due to various factors including inter-individual variability. A useful approach is to analyze the brain electroencephalogram (EEG) for differences in brain frequency bands in the signals obtained from potentially injured and healthy normal subjects. However, significant shortcomings include: (1) contrary to empirical evidence, current spectral signal analysis based methods often assume that the EEG signal is linear and stationary; (2) nonlinear time series analysis methods are mostly numerical and do not possess any predictive features. In this work, we develop models based on stochastic differential equations that can output signals with similar frequency and magnitude characteristics of the brain EEG. Initially, a coupled linear oscillator model with a large number of degrees of freedom is developed and shown to capture the characteristics of the EEG signal in the major brain frequency bands. Then, a nonlinear stochastic model based on the Duffing oscillator with far fewer degrees of freedom is developed and shown to produce outputs that can closely match the EEG signal. It is shown that such a compact nonlinear model can provide better insight into EEG dynamics through only few parameters, which is a step towards developing a framework with predictive capabilities for addressing brain injuries.

Commentary by Dr. Valentin Fuster
2013;():V002T22A004. doi:10.1115/DSCC2013-3888.

Parkinson’s disease (PD) is a neurodegenerative condition with neuronal cell death in the substantia nigra and striatal dopamine deficiency that produces slowness, stiffness, tremor, shuffling gait and postural instability. More than 1 million people in North America are affected by PD resulting in balance problems and falls. It is observed that postural instability and gait problems become resistant to pharmacologic therapy as the disease progresses. Furthermore, studies suggest that postural sway abnormalities are worsened by levodopa, the mainstay of therapy for PD. This paper presents a classification of postural balance test data using Support Vector Machines (SVM) to identify the effect of medicine (levodopa) as well as dyskinesia. It is demonstrated that SVM is a useful tool and can complement the widely accepted (but very resource intensive) Unified Parkinson’s Disease Rating Scale (UPDRS).

Commentary by Dr. Valentin Fuster
2013;():V002T22A005. doi:10.1115/DSCC2013-3954.

Tremor is a rhythmical and involuntary oscillatory movement of a body part. Mechanical loading via wearable exoskeletons is a non-invasive tremor suppression alternative to medical treatments. In this approach, the challenge is attenuating the tremor without affecting the patient’s intentional motion. An adaptive tremor suppression algorithm was designed to estimate and restrict motion within the tremor frequency band. An experimental setup was designed and developed to simulate the dynamics of a human arm joint with intentional and tremorous motion. The required orthotic suppressive force was applied via a pneumatic cylinder. The algorithm was implemented with a real-time controller and experimental results show tracking of the tremor frequency and a 97% reduction of tremor amplitude at the fundamental frequency.

Commentary by Dr. Valentin Fuster
2013;():V002T22A006. doi:10.1115/DSCC2013-4057.

This paper discusses the control of a medical exoskeleton swing leg that has a “passive” (unactuated) knee. Previous work in legged locomotion has demonstrated the feasibility of achieving natural, energy efficient walking with minimally actuated robotic systems. This work will present early results for a medical exoskeleton that only has actuation that powers the flexion and extension of the biological hip. In this work, a hybrid model of the state dependent kinematics and dynamics of the swing leg will be developed and parameterized to yield swing hip dynamics as a function of desired knee flexion dynamics. This model is used to design swing hip motions that control the flexion behavior of the passive swing knee in a human-like manner. This concept was tested by a paraplegic user wearing a new minimally actuated exoskeleton. The presented results show that a human-like swing phase can be achieved with an exoskeleton that has fewer actuated degrees of freedom than current medical exoskeletons.

Topics: Biomedicine
Commentary by Dr. Valentin Fuster

Estimation and Identification of Energy Systems

2013;():V002T23A001. doi:10.1115/DSCC2013-3809.

This paper focuses on developing a partial differential equation (PDE)-based model and parameter identification scheme for heterogeneous populations of thermostatically controlled loads (TCLs). First, a coupled two-state hyperbolic PDE model for homogenous TCL populations is derived. This model is extended to heterogeneous populations by including a diffusive term, which provides an elegant PDE control-oriented model. Second, a novel parameter identification scheme is derived for the PDE model structure, which utilizes only boundary measurements and aggregated power measurements. Simulation results against a Monte Carlo model of a large TCL population demonstrate the usefulness of the approach. The proposed model and parameter identification scheme provide system critical information for advanced demand side management control systems.

Commentary by Dr. Valentin Fuster
2013;():V002T23A002. doi:10.1115/DSCC2013-3925.

One of the main issues with vanadium redox flow batteries is that vanadium ions travels across the membrane during operation which leads to a concentration imbalance and capacity loss after long-term cycling. Precise state of charge (SOC) monitoring allows the operator to effectively schedule electrolyte rebalancing and devise a control strategy to keep the battery running under optimal conditions. However, current SOC monitoring methods are too expensive and impractical to implement on commercial VRFB systems. Furthermore, physical models alone are neither reliable nor accurate enough to predict long-term capacity loss. In this paper, we present an application of using an extended Kalman filter (EKF) to estimate the total vanadium concentration in each half-cell by combining three voltage measurements and a state prediction model without crossover effects. Simulation results show that the EKF can accurately predict capacity loss for different crossover patterns over a few hundred cycles.

Commentary by Dr. Valentin Fuster
2013;():V002T23A003. doi:10.1115/DSCC2013-3935.

Enforcement of constraints on the maximum deliverable power is essential to protect lithium-ion batteries from over-charge/discharge and overheating. This paper develops an algorithm to address the often overlooked temperature constraint in determining the power capability of battery systems. A prior knowledge of power capability provides dynamic constraints on currents and affords an additional control authority on the temperature of batteries. Power capability is estimated using a lumped electro-thermal model for cylindrical cells that has been validated over a wide range of operating conditions. The time scale separation between electrical and thermal systems is exploited in addressing the temperature constraint independent of voltage and state-of-charge (SOC) limits. Limiting currents and hence power capability are determined by a model-inversion technique, termed Algebraic Propagation (AP). Simulations are performed using realistic depleting currents to demonstrate the effectiveness of the proposed method.

Commentary by Dr. Valentin Fuster
2013;():V002T23A004. doi:10.1115/DSCC2013-3981.

A control law for an electromagnetic vibration energy harvester is derived using the maximum power transfer theorem. Using regenerative electronics, the controller cancels the reactive portion of the harvester’s impedance by eliminating the effect of mechanical inertia and stiffness elements, and the coil’s electrical inductive element. The result is an energy harvester approach that captures more vibrational energy than a passive tuned harvester. It is shown that the controlled system acts like an infinite series of passive harvesters tuned to all frequency components within a certain frequency range. The control approach also avoids the delay and computational overhead of a Fast Fourier Transform as it does not require the explicit calculation of the excitation frequency. An experimental prototype harvester was built and characterized. The prototype’s multi-domain dynamics were modeled using bond-graph techniques, and its behavior as a passive harvester was experimentally validated. The prototype’s behavior under the proposed control method is simulated and compared to the passive case. It is shown that the proposed control method harvests more power for a range of excitation frequencies than the passive harvester.

Commentary by Dr. Valentin Fuster
2013;():V002T23A005. doi:10.1115/DSCC2013-4037.

This paper presents results for nonlinear state estimation of a nonlinear, control-oriented Moving Boundary heat exchanger model derived from energy and mass conservation principles. The estimator design assumes pressure and temperature measurements typically available in waste heat recovery (WHR) applications. An Extended Kalman Filter (EKF) and a Fixed-Gain state estimator are developed for an open Organic Rankine Cycle (ORC). The ORC model assumes a nonlinear evaporator dynamic model connected to static expander and throttle valve models. Simulations show that the Fixed-Gain state estimator diverges when initial estimation error is present, and thus is not applicable for the nonlinear model. The EKF provides state estimates regardless of initial estimation error for both the Approximated and Full Jacobians used in the linearization update equations. The estimation error is slightly higher for the Approximated case only at the onset of mass flow rate changes, but shortly converge to zero in both cases. The results suggest the Approximated and Full Jacobians are valid for estimation of a nonlinear ORC in the presence of the examined transient inputs. Furthermore, the results are useful for state feedback control design and heat exchanger performance monitoring.

Commentary by Dr. Valentin Fuster
2013;():V002T23A006. doi:10.1115/DSCC2013-4064.

Model-based control of building energy offers an attractive way to minimize energy consumption in buildings. Model-based controllers require mathematical models that can accurately predict the behavior of the system. For buildings, specifically, these models are difficult to obtain due to highly time varying, and nonlinear nature of building dynamics. Also, model-based controllers often need information of all states, while not all the states of a building model are measurable. In addition, it is challenging to accurately estimate building model parameters (e.g. convective heat transfer coefficient of varying outside air). In this paper, we propose a modeling framework for “on-line estimation” of states and unknown parameters of buildings, leading to the Parameter-Adaptive Building (PAB) model. Extended Kalman filter (EKF) and unscented Kalman filter (UKF) techniques are used to design the PAB model which simultaneously tunes the parameters of the model and provides an estimate for all states of the model. The proposed PAB model is tested against experimental data collected from Lakeshore Center building at Michigan Tech University. Our results indicate that the new framework can accurately predict states and parameters of the building thermal model.

Commentary by Dr. Valentin Fuster

Fault Detection

2013;():V002T24A001. doi:10.1115/DSCC2013-3713.

Fault detection and identification (FDI) are important tasks in most modern industrial and mechanical systems and processes. Many of these systems are most naturally modeled by differential algebraic equations. One approach to FDI is based on the use of observers and filters to detect and identify faults. The method presented here uses the least squares completion to compute an ODE that contains the solution of the DAE and applies the observer directly to this ODE. Robustness with respect to disturbances is also addressed by a frequency filtering technique.

Commentary by Dr. Valentin Fuster
2013;():V002T24A002. doi:10.1115/DSCC2013-3727.

A simple model of compressor main bearings was evaluated using the mobility method. The model allows for the simulation of the three loading conditions of the compressor, as well as accounting for the geometry of the connecting rod and crankshaft. The simulation was then compared against the results from measuring the orbit of the crankshaft. This is a simple and low cost way to monitor the main bearings without installing sensors directly into the bearing sleeve. The results show good qualitative agreement to move forward with developing the model and sensor application with the end goal of application to health monitoring.

Topics: Compressors , Bearings
Commentary by Dr. Valentin Fuster
2013;():V002T24A003. doi:10.1115/DSCC2013-3825.

Fault modeling, which is the determination of the effects of a fault on a system, is an effective way for conducting failure analysis and fault diagnosis for complex system. One of the major challenges of fault modeling in complex systems is the ability to model the effects of component-level faults on the system. This paper develops a simulation-based methodology for failure analysis through modeling component-level fault effect on the system level, with application to electric vehicle powertrains. To investigate how a component fault such as short circuit in a power switch or open circuit in a motor winding affects the vehicle system, this paper develops a detailed simulator which allows us to see system and subsystem failure behaviors by incorporating fault models in the system. This fault modeling process provides useful knowledge for designing a reliable and robust fault diagnosis and prognosis procedures for electrified powertrains.

Commentary by Dr. Valentin Fuster
2013;():V002T24A004. doi:10.1115/DSCC2013-3907.

By quantifying the regularity vibration signals measured on rolling bearings, Approximate Entropy (ApEn) provides an effective measure for characterizing the structural degradation of bearings, and the severity of the defect. This paper investigates the relationship between ApEn and different failure modes of bearings. It is shown that. ApEn values decrease with the degradation of bearing defects. After introducing the theoretical background, experimental analysis are presented to quantify variation of ApEn values as a measure for defect mode and severity. A life cycle experiment is introduced to evaluate a defect growth precondition model based on regression analysis and Genetic Algorithm. Results show that ApEn is effective for bearing defect diagnosis and remaining service life prognosis.

Commentary by Dr. Valentin Fuster
2013;():V002T24A005. doi:10.1115/DSCC2013-3967.

A Digital-Displacement Pump/Motor (DDPM) has recently been proposed as an attractive candidate for hydraulic powertrain applications. A DDPM uses solenoid-controlled valves for each cylinder. This provision offers flexibility of control that can be exploited to boost system efficiency by matching individual cylinder operations with load conditions. However, the added complexity from individual cylinder control necessitates mechanisms for fault diagnosis and control reconfiguration to ensure reliable operation of the DDPM. Furthermore, available measurements are often limited to supply and return line pressures, shaft angle and speed. In this paper, it is shown that, with only these measurements, individual cylinder faults are structurally unobservable and un-isolable by the use of a system model relating the cylinder faults to the shaft dynamics. To overcome this difficulty, the phase angles at which possible individual cylinder faults can begin to affect the shaft dynamics are tabulated for each cylinder, and a fault indicator that is akin to a shaft acceleration fault is modeled and estimated via a fast sliding mode observer. Simultaneous detection and isolation of individual cylinder faults can be achieved using this fault indicator and a table of fault begin angles. Illustrative examples are included from simulations of a 5 cylinder DDPM to demonstrate this diagnosis process.

Commentary by Dr. Valentin Fuster
2013;():V002T24A006. doi:10.1115/DSCC2013-4054.

A novel method has been presented in this paper for the diagnostics of nonlinear systems using the features of the nonlinear response and capabilities of computational intelligence. Four features of the phase plane portrait have been extracted and used to characterize the nonlinear response of a nonlinear pendulum. An artificial neural network has been created and trained using the numerical data for the estimation of parameters of a defective nonlinear pendulum setup. The results show that, with appropriately selected features of the nonlinear response, the parameters of the nonlinear system can be estimated with an acceptable accuracy.

Topics: Pendulums
Commentary by Dr. Valentin Fuster

Flow and Thermal Systems

2013;():V002T25A001. doi:10.1115/DSCC2013-3718.

A dynamic model of a heat exchanger containing a phase-changing refrigerant is presented. Due to fundamental characteristics of phase-changing fluids, the model is computationally inefficient. Remedies to this inefficiency, such as hastened computation of fluid properties, realistic heat transfer coefficient blending, and active control of oscillations in the thermodynamic state of the system are presented. These remedies are shown to minimally impact the output of the model while allowing it to execute much more quickly than real-time.

Commentary by Dr. Valentin Fuster
2013;():V002T25A002. doi:10.1115/DSCC2013-3721.

In this paper, the design of a plastic flow control system for continuous gravimetric blenders used in polymer extrusion processes is discussed. The considered plant is a blending machine that mixes four different polymers, bulks and additives. In order to pursue the desired behavior, three control objectives are considered: plastic flow estimation based on weight and screw speed measurements, plastic flow regulation for each meter and control of the recipe with mass constraints such that the mixer can always satisfy the plastic flow variation needed by the extruder. Simulation results are used to show the effectiveness of the proposed approach.

Commentary by Dr. Valentin Fuster
2013;():V002T25A003. doi:10.1115/DSCC2013-3894.

The process of drying coatings constitutes an important step in automotive plants. In this paper, a control scheme for infrared drying of waterborne coatings is outlined and demonstrated. The drying process model, which is described by a coupled system of a nonlinear partial differential equation for moisture content and a nonlinear ordinary differential equation for coating temperature, is first reduced to a system of nonlinear ODEs using the POD-Galerkin method. Then, a nonlinear model predictive control framework is devised to track a prescribed moisture removal profile during the drying process, while optimizing energy consumption and quality criteria. The effectiveness of the approach is demonstrated using system simulations.

Commentary by Dr. Valentin Fuster
2013;():V002T25A004. doi:10.1115/DSCC2013-4009.

Leakage is the major factor for unaccounted losses in every pipe network around the world (oil, gas or water). In most cases the deleterious effects associated with the occurrence of leaks may present serious economical and health problems. Therefore, leaks must be quickly detected, located and repaired. Unfortunately, most state of the art leak detection systems have limited applicability, are neither reliable nor robust, while others depend on user experience.

In this work we present a new in-pipe leak detection system, PipeGuard. PipeGuard performs autonomous leak detection in pipes and, thus, eliminates the need for user experience. This paper focuses on the detection module and its main characteristics. Detection in based on the presence of a pressure gradient in the neighborhood of the leak. Moreover, the proposed detector can sense leaks at any angle around the circumference of the pipe with only two sensors. We have validated the concepts by building a prototype and evaluated its performance under real conditions in an experimental laboratory setup.

Topics: Pipelines , Leakage
Commentary by Dr. Valentin Fuster
2013;():V002T25A005. doi:10.1115/DSCC2013-4022.

This work presents a methodology for real-time estimation of wildland fire growth, utilizing afire growth model based on a set of partial differential equations for prediction, and harnessing concepts of space-time Kalman filtering and Proper Orthogonal Decomposition techniques towards low dimensional estimation of potentially large spatio-temporal states. The estimation framework is discussed in its criticality towards potential applications such as forest fire surveillance with unmanned systems equipped with onboard sensor suites. The effectiveness of the estimation process is evaluated numerically over fire growth data simulated using a well-established fire growth model described by coupled partial differential equations. The methodology is shown to be fairly accurate in estimating spatio-temporal process states through noise-ridden measurements for real-time deploy ability.

Commentary by Dr. Valentin Fuster
2013;():V002T25A006. doi:10.1115/DSCC2013-4097.

Self-optimizing control methods have received significant attention recently, due to the merit of nearly model-free capability of real-time optimization. Of particular interest in our study are two classes of self-optimizing control strategies, i.e. the Extremum Seeking Control (ESC) and Simultaneous Perturbation Stochastic Approximation (SPSA). Six algorithms, including dither ESC, adaptive dither ESC, switching ESC, one-measurement SPSA, and adaptive one-measurement SPSA are compared based on simulation study with a Modelcia based virtual plant of chiller-tower plant. The integral performance indices are evaluated to incorporate both transient and steady-state characteristics. Some design procedures are summarized for these self-optimizing control algorithms.

Commentary by Dr. Valentin Fuster

Haptics and Hand Motion

2013;():V002T26A001. doi:10.1115/DSCC2013-3701.

This paper analyzes the effect of velocity filtering cut-off frequency on the Z-width performance in haptic interfaces. Finite Difference Method (FDM) cascaded with a lowpass filter is the most commonly used technique for estimating velocity from position data in haptic interfaces. So far, there is no prescribed method for obtaining the FDM+filter cut-off frequency that will maximize the Z-width performance. We present a simulation based method to demonstrate that there exists such an ideal FDM+filter cut-off frequency, and that it can be predicted by numerical simulation. Experiments are conducted on a single degree-of-freedom linear haptic interface to validate the simulation results.

Topics: Filters
Commentary by Dr. Valentin Fuster
2013;():V002T26A002. doi:10.1115/DSCC2013-3832.

Electromyographic (EMG) processing is an important research area with direct applications to prosthetics, exoskeletons and human-machine interaction. Current state of the art decoding methods require intensive training on a single user before it can be utilized, and have been unable to achieve both user-independence and real-time performance. This paper presents a real-time EMG classification method which generalizes across users without requiring an additional training phase. An EMG-embedded sleeve quickly positions and records from EMG surface electrodes on six forearm muscles. An optimized decision tree classifies signals from these sensors into five distinct movements for any given user using EMG energy synergies between muscles. This method was tested on 10 healthy subjects using leave-one-out validation, resulting in an overall accuracy of 79±6.6%, with sensitivity and specificity averaging 66% and 97.6%, respectively, over all classified motions. The high specificity values demonstrate the ability to generalize across users, presenting opportunities for large-scale studies and broader accessibility to EMG-driven applications.

Commentary by Dr. Valentin Fuster
2013;():V002T26A003. doi:10.1115/DSCC2013-3842.

This paper presents a model-mediated approach for teleoperation with haptic feedback in the presence of time delays on the order of seconds. The target application for the control scheme is teleoperation of robotic manipulators for space systems in geosynchronous orbit. Previous work in model-mediated teleoperation allowed operators to interact with a virtual model of the remote robot and environment, where the remote robot follows the operator’s commands after a delay and the virtual model is updated when the remote data is available. Our approach adds predictive models, mediated command execution, and a dynamic slave model. A single-degree-of-freedom experiment using a simulated robot and environment demonstrate improvements in the control of remote robot position and environment contact forces, in comparison to previous approaches.

Commentary by Dr. Valentin Fuster
2013;():V002T26A004. doi:10.1115/DSCC2013-3866.

The aim of this study is to develop a compact haptic glove that can present a variety of grasping sensations. This paper proposes a mechanism of compressing a finger joint to induce friction torque between the link and joint. In order to reduce weight and produce greater force, shape memory alloys were chosen as an actuator. The result of an experiment showed a linear relationship between the compressing force of a finger joint and friction torque, and suggested the effectiveness of the proposed mechanism. The prototype system suggested the proposed device is small and lightweight compared to the conventional device.

Commentary by Dr. Valentin Fuster
2013;():V002T26A005. doi:10.1115/DSCC2013-3982.

In this work different friction models are evaluated to determine how well these models are suited for performance simulation and control of a 6-DOF haptic device. The studied models include, Dahl model, LuGre model, Generalized Maxwell slip model (GMS), smooth Generalized Maxwell slip model (S-GMS) and Differential Algebraic Multistate (DAM) friction model. These models are evaluated both numerically and experimentally with an existing 6-DOF haptic device that is based on a Stewart platform. In order to evaluate how well these models compensate friction, a model-based feedback friction compensation strategy along with a PID controller were used for position tracking accuracy. The accuracies of the friction compensation models are examined separately for both low-velocity and high-velocity motions of the system. To evaluate these models, we use criteria based on fidelity to predict realistic friction phenomena, easiness to implement, computational efficiency and easiness to estimate the model parameters. Experimental results show that friction compensated with GMS, S-GMS and DAM models give better accuracy in terms of standard deviation, Root Mean Squared Error, and maximum error between a reference and measured trajectory. Based on the criteria of fidelity, ease of implementation and ease to estimate model parameters, the S-GMS model, which represents a smooth transition between sliding and pre-sliding regime through an analytical set of differential equations, is suggested.

Topics: Friction , Haptics
Commentary by Dr. Valentin Fuster
2013;():V002T26A006. doi:10.1115/DSCC2013-4077.

HAPTIC PONG is a force-feedback version of the classic arcade game “Pong”, conceived as an educational game that can teach physics and controls concepts to high school students. Our design incorporates two identical linear one-degree-of-freedom haptic paddles, each with a four-bar linkage transforming motor rotation to linear motion. Virtual environments were designed to incorporate dynamic systems describing the force-displacement relationships of each paddle. At a demonstration with 50 high school students, a prototype of the device was rated as both educational and fun to use. After the initial proof of concept, a design optimization study was conducted to improve the kinematic performance of the linear haptic devices based on the device constraints for the application. Optimization considered both the linearity of the coupler point and Jacobian minimum singular value. While maintaining a satisfactory level of linearity, the optimized linkage lengths produced an estimated 160% improvement in the maximum consistent force output.

Commentary by Dr. Valentin Fuster

Human Assistive Systems and Wearable Robots: Applications and Assessment

2013;():V002T27A001. doi:10.1115/DSCC2013-3839.

We present a real-time human body-segment (e.g., upper limbs) orientation estimation scheme in rider-bicycle interactions. The estimation scheme is built on the fusion of measurements of an un-calibrated monocular camera on the bicycle and a set of small wearable gyroscopes attached to rider’s upper limbs. The known optical features are conveniently collocated with the gyroscopes. The design of an extended Kalman filter (EKF) to fuse the vision/inertial measurements compensates for the drifting errors by directly integrating gyroscope measurements. The characteristic and constraints from human anatomy and the rider-bicycle interactions are used to enhance the EKF performance. We demonstrate the effectiveness of the estimation design through bicycle riding experiments. The attractive properties of the proposed pose estimation in human-machine interactions include low-cost, high-accuracy, and wearable configurations for outdoor personal activities. Although we only present the application for rider-bicycle interactions, the proposed estimation scheme is readily extended and used for other types of human-machine interactions.

Topics: Bicycles
Commentary by Dr. Valentin Fuster
2013;():V002T27A002. doi:10.1115/DSCC2013-3891.

This research aims at developing a magnetic resonance (MR)-compatible equivalent of an exoskeleton used for wrist movement rehabilitation therapy of neurological patients. As a crucial step towards the accomplishment of this goal, this paper investigates the development of a novel actuation architecture suitable for interaction control in MR environments, the MR-SEA (SEA stands for Series Elastic Actuator). MR-SEA consists of the combination of a non-backdriveable MR-compatible actuator and of a compliant force-sensing element. The preliminary design of a 1 DOF actuator is presented, in addition to non-linear dynamical model of the system featuring the most relevant actuator non linearities. A switching controller is proposed, and the asymptotic stability of the resulting discontinuous dynamical system is demonstrated for force control in blocked output conditions. Simulation results show that the proposed system is adequate for the implementation of force control for wrist movement protocols in fMRI, demonstrating a bandwidth higher than 8 Hz for force control. For stiffness control, simulation results demonstrate that the system is passive for all values of desired virtual stiffness lower than the stiffness of the physical spring, and isolated stability is obtained for the entire range of stiffness values considered.

Topics: Elasticity , Actuators
Commentary by Dr. Valentin Fuster
2013;():V002T27A003. doi:10.1115/DSCC2013-4042.

Robotic systems provide a paradigm shift in maximizing neural plasticity as part of human motor control recovery following stroke. Such a system shifts the treatment from therapist dependent to patient dependent by its potential to increase the treatment dose and intensity, as long as the patient can tolerate it. The experimental protocol included 10 post stroke hemiparetic subjects in a chronic stage. Subjects were treated with an upper limb exoskeleton system (EXO-UL7) using a unilateral mode, and a bilateral mode. Seven virtual reality tasks were utilized in the protocol. A kinematic-based methodology was used to study the intensity of the virtual reality tasks in each one of the operational modes. The proposed method is well suited for early evaluation of a given virtual reality task, or movement assistance modality during the development process. Pilot study data were analyzed using the proposed methodology. This allowed for the identification of kinetic differences between the assistance modalities by assessing the intensity of the virtual reality tasks.

Commentary by Dr. Valentin Fuster
2013;():V002T27A004. doi:10.1115/DSCC2013-4043.

In order for stroke victims to gain functional recovery of their hemiparetic limbs, facilitation techniques such as the repetitive facilitation exercise, or RFE, have been developed. Currently, there is a lack of understanding of the neural mechanisms associated with these types of facilitation techniques. To better understand the neural mechanisms associated with the RFE a functional magnetic resonance imaging (fMRI) study should be conducted. This paper presents initial experimental results testing the feasibility of implementing an fMRI-compatible actuator to facilitate a myotatic reflex in synchronization with the patient’s intention to move the hemiparetic limb. Preliminary data from a healthy individual demonstrated the feasibility of overlapping the long latency component of the afferent myotatic reflex with descending nerve impulses in a time window of 15ms. In addition, to implement the RFE into an fMRI-compatible device, a pneumatic actuation time delay due to long transmission line was evaluated. The results may be used for the assessment of the RFE using an fMRI-compatible robotic device in the future.

Commentary by Dr. Valentin Fuster
2013;():V002T27A005. doi:10.1115/DSCC2013-4073.

This paper investigates the possibility of implementing force-feedback controllers using measurement of interaction force obtained through force-sensing resistors (FSRs), to improve performance of human interacting robots. A custom sensorized handle was developed, with the capability of simultaneously measuring grip force and interaction force during robot-aided rehabilitation therapy. Experiments are performed in order to assess the suitability of FSRs to implement force-feedback interaction controllers. In the force-feedback control condition, the applied force for constant speed motion of a linear 1DOF haptic interface is reduced 6.1 times compared to the uncontrolled condition, thus demonstrating the possibility of improving transparency through force-feedback via FSRs.

Commentary by Dr. Valentin Fuster
2013;():V002T27A006. doi:10.1115/DSCC2013-4083.

This paper presents a task model and communication method used to control and coordinate a wearable robot, termed Supernumerary Robotic Limb (SRL), with a human worker during the execution of a specialized task. When controlling a collaborative system like this, we need strong communication between the robot and its wearer in order to be able to coordinate their actions. We address the communication challenges between the human worker and the SRL by monitoring the worker’s actions with wearable sensors. Combining these wearable sensors together with a well defined task model allows the robot to act according to the wearer’s intent. The task model is structured using Coloured Petri Nets (CPN) due to the process’ deterministic and concurrent nature. We performed various tests in which the user had to execute a task while wearing the sensor suit. This data was used to establish the threshold values for our predetermined gestures and postures of interest. Detecting these postures and gestures are used to trigger task transitions in the CPN model. This allows the wearer to communicate his intentions effectively to the SRL and execute the task in a well-structured and coordinated manner with the SRL.

Topics: Robotics
Commentary by Dr. Valentin Fuster

Human Assistive Systems and Wearable Robots: Design and Control

2013;():V002T28A001. doi:10.1115/DSCC2013-3893.

Rehabilitation of upper extremity, especially hands, is critical for the restoration of independence in activities of daily living for individuals suffering from hand disabilities. In this work, we propose a biologically-inspired design of an index finger exoskeleton. The design has passive stiffness at each joint with antagonistic tendon driven actuation allowing for (1) improved kinematic and dynamic compatibility for effective therapy; and (2) conformation of exoskeleton and finger joints axes of rotation. We present a kinematics and dynamics model of the coupled index finger-exoskeleton system that incorporates human-like passive torques at the metacarpophalangeal (MCP), proximal interphalangeal (PIP) and distal interphalangeal (DIP) joints. We carry out simulations using this coupled system model to study the role of passive stiffness on workspace and tendon forces, actuator force and displacement requirements, and reaction forces and moments acting at the finger joints for an index finger flexion-extension task. Results show that accurately modeling the coupled system can help in optimizing the design and control of the device, thus, exploiting its passive dynamics for effective functioning.

Commentary by Dr. Valentin Fuster
2013;():V002T28A002. doi:10.1115/DSCC2013-3908.

There is increasing interest in powered prosthesis. To reduce energy, power, and torque requirements on the active input, current systems, such as powered ankle prosthetics, utilize a combination of passive and active components. By storing and releasing energy during gait, the passive component reduces the energy/power/torque requirements of the active component. Therefore, it is advantageous to maximize the use of the passive component for achieving the desired motion. Typically, the passive component utilizes elastic elements such as springs, which cannot be easily adjusted to achieve a desired optimal nonlinear response. In this work, we report the use of a cam profile to achieve a general desired nonlinear response. The results show that the added design flexibility (to achieve nonlinear response of the passive element) can substantially reduce the energy/power/torque requirement of the active component.

Topics: Robotics , Springs
Commentary by Dr. Valentin Fuster
2013;():V002T28A003. doi:10.1115/DSCC2013-3980.

Passive variable stiffness at the human hand joints is shown to be critical for achieving stable and dexterous grasping and manipulation. Our long-term goal is to implement it in robotic hand joints. We introduce a novel design, using linear springs and non-circular cam, for a variable stiffness joint mechanism that mimics the passive stiffness characteristics of human hand joints. We present a methodology based on the principle of virtual work for synthesizing the cam shape in the joint. Key innovations of our design are a) human-like joint stiffness profile, b) large joint range of motion, and c) modular arrangement for varying torque range. We have built a prototype for validating our approach and the experimental results demonstrate that the proposed joint mechanism fulfills the design goals of our study.

Commentary by Dr. Valentin Fuster
2013;():V002T28A004. doi:10.1115/DSCC2013-4038.

Lower-extremity powered exoskeletons have traditionally used four to ten powered degrees of freedom to provide gait assistance for individuals with spinal cord injury (SCI). Systems with numerous high-impedance powered degrees of freedom commonly suffer from cumbersome walking dynamics and decreased utility due to added weight and increased control complexity. We propose a new approach to powered exoskeleton design that minimizes actuation and control complexity by embedding intelligence into the hardware. This paper describes a minimalistic system that uses a single motor for each exoskeleton leg in conjunction with a bio-inspired hip-knee coupling mechanism to enable users to walk, sit, and stand. Operating in concert with a custom orthotic knee joint, the exoskeleton hip joint has been designed to mimic the biarticular coupling of human leg muscles thus allowing a single actuator to power both hip and knee motions simultaneously. The implementation of this design resulted in a system that provides comparable performance to existing exoskeletons. This system has been tested on paraplegic subjects and has successfully enabled patients to stand up, sit down, and ambulate in numerous real world situations.

Topics: Design , Biomedicine
Commentary by Dr. Valentin Fuster
2013;():V002T28A005. doi:10.1115/DSCC2013-4093.

The ability to control individual muscle activity is widely applicable in clinical diagnostics, training, and rehabilitation. Inducing muscle patterns that amplify abnormal muscle coordination can assist with early diagnosis of neuromuscular disorders. Individual muscle control also allows for targeted exercise of muscles weakened by disease, injury, or disuse. The goals of this research are to test a system for individual muscle control and introduce the use of muscle ultrasound as an alternative to electromyography (EMG). The system integrates a computational model of the right upper extremity with a robotic manipulator to predict and control muscle activity. To test the system, subjects gripped the manipulator and isometrically resisted loads applied to the hand. Muscle activity was measured via EMG and ultrasound. The system was able to induce the desired direction of muscle activity change but with limited precision. EMG measurement appeared susceptible to error due to crosstalk in the forearm.

Commentary by Dr. Valentin Fuster
2013;():V002T28A006. doi:10.1115/DSCC2013-4107.

The paper presents a control approach based on vertebrate neuromodulation and its implementation on an autonomous robot platform. A simple neural network is used to model the neuromodulatory function for generating context based behavioral responses to sensory signals. The neural network incorporates three types of neurons — cholinergic and noradrenergic (ACh/NE) neurons for attention focusing and action selection, dopaminergic (DA) neurons for curiosity-seeking, and serotonergic (5-HT) neurons for risk aversion behavior. The implementation of the neuronal model on a relatively simple autonomous robot illustrates its interesting behavior adapting to changes in the environment. The integration of neuromodulation based robots in the study of human-robot interaction would be worth considering in future.

Topics: Robots
Commentary by Dr. Valentin Fuster

Instrumentation and Characterization in Bio-Systems

2013;():V002T29A001. doi:10.1115/DSCC2013-3847.

Compartment syndrome is a major concern in cases of extremity trauma, which occur in over 70% of military combat casualty. Without treatment, compartment syndrome can lead to paralysis, loss of limb, or death. This paper focuses on the development of a handheld sensor that can be used for the non-invasive diagnosis of compartment syndrome. Analytical development of the sensing principle is first presented in which a relation is obtained between the pressure in a fluid compartment and the stiffness experienced by a handheld probe pushing on the compartment. Then a handheld sensor that can measure stiffness of an object without requiring the use of any inertial reference is presented. The handheld sensor consists of an array of three miniature force-sensing spring loaded pistons placed together on a probe. The center spring is chosen to be significantly stiffer than the side springs. The ratio of forces between the stiff and soft springs is proportional to the stiffness of the soft object against which the probe is pushed. Small mm-sized magnets on the pistons and magnetic field measurement chips are used to measure the forces in the individual pistons. Experimental results are presented using an in-vitro test rig that replicates a fluid pressure compartment. The sensor is shown to measure pressure accurately with a resolution of 0.1 psi over the range 0.75 psi to 2.5 psi.

Commentary by Dr. Valentin Fuster
2013;():V002T29A002. doi:10.1115/DSCC2013-3855.

This article addresses output-boundary regulation for high-scan-frequency Atomic Force Microscope (AFM) imaging of soft samples. The main contribution of this article is to use the causal inverse for nonminimum phase systems to rapidly transition an output away from a specified boundary whenever the output approaches the boundary due to unknown disturbances. The proposed feedforward-based control technique overcomes both: (i) lack of preview information of the disturbances; and (ii) performance limitations of feedback-based control methods for non-minimum phase systems. Simulation results for an example AFM are presented to illustrate the approach.

Commentary by Dr. Valentin Fuster
2013;():V002T29A003. doi:10.1115/DSCC2013-3994.

We present the design and fabrication of a Micro-Electro-Mechanical Systems based piezoresistive cantilever force sensor as a potential candidate for micro/nano indentation of biological specimens such as cells and tissues. The fabricated force sensor consists of a silicon cantilever beam with a p-type piezoresistor and a cylindrical probing tip made from SU-8 polymer. One of the key features of the sensor is that a standard silicon wafer is used to make silicon-on-insulator (SOI), thereby reducing the cost of fabrication. To make SOI from standard silicon wafer the silicon film was sputtered on an oxidized silicon wafer and annealed at 1050 °C so as to obtain polycrystalline silicon. The sputtered silicon layer was used to fabricate the cantilever beam. The as-deposited and annealed silicon films were experimentally characterized using X-ray diffraction (XRD) and Atomic Force Microscopy (AFM). The annealed silicon film was polycrystalline with a low surface roughness of 3.134 nm (RMS value).

Commentary by Dr. Valentin Fuster
2013;():V002T29A004. doi:10.1115/DSCC2013-4023.

This paper develops an efficient vision-based real-time vein detection algorithm for preclinical vascular insertions. Mouse tail vein injections perform a routine but critical step in most preclinical applications. Compensating for poor manual injection stability and high skill requirements, Vascular Access System (VAS) has been developed so a trained technician can manually command the system to perform needle insertions and monitor the operation through a near-infrared camera. However, VAS’ vein detection algorithm requires much computation and is, therefore, difficult to reflect the real-time tail movement during an insertion. Furthermore, the detection performance is often disturbed by tail hair and skin pigmentation. In this work, an effective noise filtering algorithm is proposed based on convex optimization. Effectively eliminating false-positive detections and preserving cross-sectional continuity, this algorithm provides vein detection results approximately every 200 ms at the presence of tail hair and skin pigmentation. This developed real-time tail vein detection method is able to capture the tail movement during insertion, therefore allow for the development of an automated Vascular Access System (A-VAS) for preclinical injections.

Commentary by Dr. Valentin Fuster
2013;():V002T29A005. doi:10.1115/DSCC2013-4062.

Engineered skeletal muscle tissue has the potential to be used as dual use actuator and stress-bearing material providing numerous degrees of freedom and with significant active stress generation. To exploit the potential features, however, technologies must be established to generate mature muscle strips that can be controlled with high fidelity. Here, we present a method for creating mature 3-D skeletal muscle tissues that contract in response to optical activation stimuli. The muscle strips are fascicle-like, consisting of several mm-long multi-nucleate muscle cells bundled together. We have found that applying a tension to the fascicle-like muscle tissue promotes maturation of the muscle. The fascicle-like muscle tissue is controlled with high spatiotemporal resolution based on optogenetic coding. The mouse myoblasts C2C12 were transfected with Channelrhodopsin-2 to enable light (∼470 nm) to control muscle contraction. The 3D muscle tissue not only twitches in response to an impulse light beam, but also exhibits a type of tetanus, a prolonged contraction of continuous stimuli, for the first time. In the following, the materials and culturing method used for 3D muscle generation is presented, followed by experimental results of muscle constructs and optogenetic control of the 3D muscle tissue.

Topics: Actuators , Muscle
Commentary by Dr. Valentin Fuster
2013;():V002T29A006. doi:10.1115/DSCC2013-4105.

In this study, we introduce a novel method for control of self-organization of nanoparticles in microchannels using the control of nanoliter droplets and show its useful applications. By controlling capillary force and evaporation process, nanoparticles can be assembled at the desired area and they can be used from nanoporous membranes to biosensor itself. As the biosensor applications, biologically inspired humidity sensor and IgG antibody detector were developed. They can recognize the target materials by the change of visual color without using any fluorescent probe and external electrical power source. These highly organized nanoparticles also induce the unique nanoelectrokinetics, which open new application fields such as such as separation, filtering, accumulation, and analysis of biomolecules, energy generation, and optofluidic system. Among them, we introduce two techniques that are diffuse based chemical gradient generation and sea water desalination.

Commentary by Dr. Valentin Fuster

Intelligent Transportation Systems

2013;():V002T30A001. doi:10.1115/DSCC2013-3830.

To improve the ride quality in connected vehicle platoons, information about the motion of the leader can be transmitted using vehicle-to-vehicle (V2V) communication and such information can be incorporated in the controllers of the following vehicle. However, according to the current V2V standards, dedicated short range communication (DSRC) devices transmit information every 100 ms which introduces time delays into the control loops. In this paper we study the effects of these time delays on the dynamics of vehicle platoons subject to digital control and derive conditions for plant stability and string stability. It is shown that when the time delay exceeds a critical value, no gain combination can stabilize the system. Our results have important implications on connected vehicle design.

Commentary by Dr. Valentin Fuster
2013;():V002T30A002. doi:10.1115/DSCC2013-3876.

This paper presents a reconfigurable control design technique that integrates a robust feedback and an iterative learning control (ILC) scheme. This technique is applied to develop vehicle control systems that are tolerant to failures due to malfunctions or damages. The design procedure includes solving the robust performance condition for a feedback controller through the use of μ-synthesis that also satisfies the convergence condition for the iterative learning control rule. The effectiveness of the proposed approach is verified by simulation experiments using a radio-controlled (R/C) model airplane. The methods presented in this paper can be applied to design of global intelligent control systems to improve the operating characteristics of a vehicle and increase safety and reliability.

Commentary by Dr. Valentin Fuster
2013;():V002T30A003. doi:10.1115/DSCC2013-3882.

Merging is one of the important issues in studying roadway traffic. Merging disturbs the mainline of traffic, which reduces the efficiency or capacity of the highway system. In this paper, we have considered the application of a Stackelberg game theory to a driver behavior model in a merging situation. In this model, the so-called payoffs that reflect the drivers’ aggressiveness affect the decision to proceed to merge and whether to accelerate or decelerate in the game theoretic framework. These merging behaviors in turn impact the mainline traffic, which may lead to a variety of influences, such as collisions or reduced roadway throughput. Consequently, this impact depends on the level of aggressiveness of the driver merging in and those in the mainline, which results in both longitudinal and lateral disturbances in the mainline due to their interaction.

Commentary by Dr. Valentin Fuster
2013;():V002T30A004. doi:10.1115/DSCC2013-3885.

In this paper we present an enhancement of model-based trajectory selection algorithms — a popular class of collision avoidance techniques for autonomous ground vehicles. Rather than dilate a set of individual candidate trajectories in an ad hoc way to account for uncertainty, we generate a set of trajectory clouds — sets of states that represent possible future poses over a product of intervals representing uncertainty in the model parameters, initial conditions and actuator commands. The clouds are generated using the sparse-grid interpolation method which is both error-controlled and computationally efficient. The approach is implemented on a differential drive vehicle.

Commentary by Dr. Valentin Fuster
2013;():V002T30A005. doi:10.1115/DSCC2013-3919.

Combining hybrid powertrain optimization with traffic information has been researched before, but tradeoffs between optimality, driving-cycle sensitivity and speed of calculation have not been cohesively addressed. Optimizing hybrid powertrain with traffic can be done through iterative methods such as Dynamic Programming (DP), Stochastic-DP and Model Predictive Control, but high computation load limits their online implementation. Equivalent Consumption Minimization Strategy (ECMS) and Adaptive-ECMS were proposed to minimize computation time, but unable to ensure real-time charge-sustaining-operation (CS) in transient traffic environment. Others show relationship between Pontryagin’s Minimum Principles (PMP) and ECMS, but iteratively solve the CS-operation problem offline. This paper proposes combining PMP’s necessary conditions for optimality, with sum-of State-Of-Charge-derivative for CS-operation. A lookup table is generated offline to interpolate linear mass-fuel-rate vs net-power-to-battery slopes to calculate the equivalence ratio for real-time implementation with predicted traffic data. Maximum fuel economy improvements of 7.2% over Rule-Based is achieved within a simulated traffic network.

Topics: Optimization , Traffic
Commentary by Dr. Valentin Fuster
2013;():V002T30A006. doi:10.1115/DSCC2013-4040.

Wireless vehicle-to-vehicle communication technologies such as the dedicated short range communication (DSRC) may be used to assist drivers in sensing and responding to impalpable information such as the precise acceleration of vehicles ahead. In this paper, we investigate the impact of delayed acceleration feedback on traffic flow using a nonlinear car-following model. It is shown that acceleration feedback can improve the stability of uniform traffic flow, though excessive acceleration feedback leads to undesired high frequency oscillations. Additionally, time delays in the communication channel may shrink the stable domain by introducing mid-frequency oscillations. Finally, we show that one may stabilize vehicle platoons using delayed acceleration feedback even in cases when finite driver reaction time would destabilize the system. Our results may lead to more robust cruise control systems with increased driver comfort in connected vehicle environment.

Commentary by Dr. Valentin Fuster

Linear Systems and Robust Control

2013;():V002T31A001. doi:10.1115/DSCC2013-3710.

Output reversibility involves dynamical systems where for every initial condition and the corresponding output there exists another initial condition such that the output generated by this initial condition is a time-reversed image of the original output with the time running forward. Through a series of necessary and sufficient conditions, we characterize output reversibility in linear single-output discrete-time dynamical systems in terms of the geometric symmetry of its eigenvalue set with respect to the unit circle in the complex plane. Furthermore, we establish that output reversibility of a linear continuous-time system implies output reversibility of its discretization regardless of the sampling rate. Finally, we present a numerical example involving a discretization of a Hamiltonian system that exhibits output reversibility.

Topics: Dynamic systems
Commentary by Dr. Valentin Fuster
2013;():V002T31A002. doi:10.1115/DSCC2013-3716.

In this paper, the input covariance constraint (ICC) control problem is solved by a convex optimization with linear matrix inequality (LMI) constraints. The ICC control problem is an optimal control problem that is concerned with finding the best output performance possible subject to multiple constraints on the input covariance matrices. The contribution of this paper is the characterization of the control synthesis LMIs used to solve the ICC control problem. To demonstrate the effectiveness of the proposed approach a numerical example is solved with the control synthesis LMIs. Both discrete and continuous-time problems are considered.

Commentary by Dr. Valentin Fuster
2013;():V002T31A003. doi:10.1115/DSCC2013-3789.

This paper further studies the analysis and control problems of continuous-time switched linear systems subject to actuator saturation. Using the norm-bounded differential inclusion (NDI) description of the saturated systems and the minimal switching rule, a set of switched output feedback controllers is designed to minimize the disturbance attenuation level defined by the regional ℒ2 gain over a class of energy-bounded disturbances. The synthesis conditions are expressed as bilinear matrix inequalities (BMIs) and can be solved by numerical search coupled with linear matrix inequality (LMI) optimization. Compared to the previous method based on polytopic differential inclusion (PDI), the proposed approach has good scalability and potentially renders better performance. Numerical examples are provided to verify effectiveness of the proposed approach.

Commentary by Dr. Valentin Fuster
2013;():V002T31A004. doi:10.1115/DSCC2013-3814.

A disturbance observer (DOB) is a useful control algorithm for systems with uncertain dynamics, such as nonlinearity and time-varying dynamics. The DOB, however, is designed based on a nominal model, and its stability is sensitive to the magnitude of discrepancy between a controlled system and its nominal model. Therefore, to increase the stability margin of the DOB, it requires an accurate model identification, which is often difficult for nonlinear or uncertain systems. In this paper, the parameters of the nominal model are continuously updated by a parameter adaptation algorithm (PAA) to keep the model discrepancy small, such that the DOB is able to show its desired performance without losing stability robustness even in the presence of nonlinearity and/or time-varying dynamics. In the integration of the DOB and the PAA, however, there exists a complicated signal interaction. In this paper, such interaction problem is solved from a practical point of view; signal filtering. The proposed method shows improved performance for an electric motor system, and is verified by experimental results in this paper.

Commentary by Dr. Valentin Fuster
2013;():V002T31A005. doi:10.1115/DSCC2013-3989.

When a continuous-time linear system is discretized using a hold, stability of poles are preserved. However, the transformations of zeros are much more complicated and the number of the zeros increases in some cases in the discretization process. This paper is concerned with the zeros of a sampled-data model resulting from a continuous-time multivariable system which is not decouplable by static state feedback and has all of the relative degrees one. Two cases of a zero-order hold and a fractional-order hold are treated. An approximate expression of the zeros is given as power series expansions with respect to a sampling period in the zero-order hold case. Further, the limiting zeros are analyzed in the fractional-order hold case. Then, the advantage of the fractional-order hold to the zero-order hold is discussed from the viewpoint of stability of the zeros.

Commentary by Dr. Valentin Fuster

Marine Vehicles

2013;():V002T32A001. doi:10.1115/DSCC2013-3717.

In general, sensor networks have two competing objectives: (i) maximization of network performance with respect to the probability of successful search with a specified false alarm rate for a given coverage area, and (ii) maximization of the network’s operational life. In this context, battery-powered sensing systems are operable as long as they can communicate sensed data to the processing nodes. Since both operations of sensing and communication consume energy, judicious use of these operations could effectively improve the sensor network’s lifetime. From these perspectives, the paper presents an adaptive energy management policy that will optimally allocate the available energy between sensing and communication operations at each node to maximize the network performance under specified constraints. With the assumption of fixed total energy for a sensor network operating over a time period, the problem is reduced to identification of a network topology that maximizes the probability of successful detection of targets over a surveillance region. In a two-stage optimization, a genetic algorithm-based meta-heuristic search is first used to efficiently explore the global design space, and then a local pattern search algorithm is used for convergence to an optimal solution. The results of performance evaluation are presented to validate the proposed concept.

Topics: Sensor networks
Commentary by Dr. Valentin Fuster
2013;():V002T32A002. doi:10.1115/DSCC2013-3745.

In this paper, we describe the development of an experimental testbed capable of producing controllable ocean-like flows in a laboratory setting. The objective is to develop a testbed to evaluate multi-robot strategies for tracking manifolds and Lagrangian coherent structures (LCS) in the ocean. Recent theoretical results have shown that LCS coincide with minimum energy and minimum time optimal paths for autonomous vehicles in the ocean. Furthermore, knowledge of these structures enables the prediction and estimation of the underlying fluid dynamics. The testbed is a scaled flow tank capable of generating complex and controlled quasi-2D flow fields that exhibit wind-driven double-gyre flows. Particle image velocimetry (PIV) is used to extract the 2D surface velocities and the data is then processed to verify the existence of manifolds and Lagrangian coherent structures in the flow. The velocity data is then used to evaluate our previously proposed multi-robot LCS tracking strategy in simulation.

Commentary by Dr. Valentin Fuster
2013;():V002T32A003. doi:10.1115/DSCC2013-3838.

This article presents an experimental assessment of an Unmanned Surface Vehicle (USV) executing an approach behavior to several stationary targets in an obstacle field. A lattice-based trajectory planner is implemented with a priori knowledge of the vehicle characteristics. In parallel, a low-level controller is developed for the vehicle using a proportional control law. These systems are integrated on the USV control system using the Lightweight Communications and Marshalling (LCM) message passing system. Filtered vehicle-state information from onboard sensors is passed to the planner, which returns a least-cost, dynamically feasible trajectory for achieving the ascertained goal. The system was tested in a 750 m by 150 m area of the US Intracoastal Waterway in South Florida in the presence of wind and wave disturbances to characterize its effectiveness in a real-world scenario. The vehicle was able to replicate behavior predicted in simulations when navigating around obstacles. The approach distance to each target was favorably lower than the user-defined limit. Owing to the fact that the USV uses differential thrust for steering, the vehicle tracked the planned trajectories better at lower speeds.

Topics: Vehicles
Commentary by Dr. Valentin Fuster
2013;():V002T32A004. doi:10.1115/DSCC2013-3849.

The authors developed an approach to a “best” time path for Autonomous Underwater Vehicles sailing uncertain currents. The numerical optimization tool DIDO is used to compute minimum time paths for a sample of currents between ebb and flow. A simulated meta-experiment is performed where the vehicle traverses the resulting paths under different current strengths per run. The fastest elapsed time emerges from a payoff table.

Commentary by Dr. Valentin Fuster
2013;():V002T32A005. doi:10.1115/DSCC2013-3963.

In this paper we apply backstepping technique to develop a novel hybrid target-tracking control scheme for a carangiform robotic fish, based on a dynamic model that combines rigid-body dynamics with Lighthill’s large-amplitude elongated-body theory. This hybrid controller consists of an open-loop turning controller and a closed-loop approaching controller. A hysteretic switching strategy based on the orientation error is designed. Using Lyapunov analysis, we show that the trajectory of the robotic fish will converge to the target point. The effectiveness of the proposed control strategy is demonstrated through both simulations and experiments.

Commentary by Dr. Valentin Fuster
2013;():V002T32A006. doi:10.1115/DSCC2013-4015.

Gliding robotic fish is a new type of underwater robots that combines the energy-efficiency of underwater gliders and the high maneuverability of robotic fish. The tail fin of a gliding robotic fish provides the robot more control authority, especially for the lateral motion, compared with traditional underwater gliders. In this paper, the design and development of a gliding robotic fish prototype is first presented, followed by its dynamic model. We then focus on the problem of tail-enabled yaw stabilization during gliding, where a sliding mode controller is proposed. Both simulation and experimental results are demonstrated to validate the effectiveness of the proposed controller.

Commentary by Dr. Valentin Fuster

Nonholonomic Systems

2013;():V002T33A001. doi:10.1115/DSCC2013-3843.

In this paper we present an energy-based algorithm to minimize limit cycles in dynamically balancing wheeled inverted pendulum (IP) machines. Because the algorithm is not based on the numerical value of parameters, performance is robust and accounts for mechanical reconfiguration and wear. The effects of phenomena such as drive-train friction, rolling friction, backlash and sensor bandwidth are well known, causing either limit cycles or instabilities in IP balancing machines and yet compensation or control design to mitigate these effects are not well known. The effects of these non-linearities can be observed in the energy behavior of IP balancing machines, hence, as a broader goal we seek to establish an energy-based framework for the investigation of non-linearities in this class of machines. We successfully demonstrate the effectiveness of our algorithm on a two-wheeled IP balancing machine, “Charlie”, developed in our laboratory. As an example we show a reduction in the amplitude of limit cycles by 95.9% in wheel angle and 89.8% in pitch over a 10 second period.

Commentary by Dr. Valentin Fuster
2013;():V002T33A002. doi:10.1115/DSCC2013-3883.

We address trajectory generation for the snakeboard, a system commonly studied in the geometric mechanics community. Our approach derives a solution using body coordinates and local trajectory information, leading to a more intuitive solution compared to prior work. The simple forms of the solution clearly show how they depend on local curvature and desired velocity profile, allowing for a description of some simple motion primitives. We readily propose techniques to navigate paths, including those with sharp corners, by taking advantage of the snake-board’s singular configuration, as well as discuss some implications of torque limits.

Commentary by Dr. Valentin Fuster
2013;():V002T33A003. doi:10.1115/DSCC2013-3902.

In this paper, we develop a coordination control technique for a group of agents described by a general class of underactuated dynamics. The objective is for the agents to reach and maintain a desired formation characterized by steady-state distances between the neighboring agents. We use graph theoretic notions to characterize communication topology in the network determined by the information flow directions and captured by the graph Laplacian matrix. Furthermore, using sliding mode control approach, we design decentralized controllers for individual agents that use only data from the neighboring agents which directly communicate their state information to the current agent in order to drive the current agent to the desired steady state. Finally, we show the efficacy of our theoretical results on the example of a system of wheeled mobile robots that reach and maintain the desired formation.

Commentary by Dr. Valentin Fuster
2013;():V002T33A004. doi:10.1115/DSCC2013-3941.

We present a novel mechanical system, the “landfish,” which takes advantage of a combination of articulation and a nonholonomic constraint to exhibit fishlike locomotion. We apply geometric mechanics techniques to establish the equations of motion in terms of the system’s nonholonomic momentum and analyze the system’s equilibrium properties. Finally, we demonstrate its locomotion capabilities under several controllers, including heading and joint velocity control.

Commentary by Dr. Valentin Fuster
2013;():V002T33A005. doi:10.1115/DSCC2013-3946.

Geckos that jump, cats that fall, and satellites that are inertially controlled fundamentally locomote in the same way. These systems are bodies in free flight that actively reorientate under the influence of conservation of angular momentum. We refer to such bodies as inertial systems. This work presents a novel control method for inertial systems with drift that combines geometric methods and computational control. In previous work, which focused on inertial systems starting from rest, a set of visual tools was developed that readily allowed on to design gaits. A key insight of this work was deriving coordinates, called minimum perturbation coordinates, which allowed the visual tools to be applied to the design of a wide range of motions. This paper draws upon the same insight to show that it is possible to approximately analyze the kinematic and dynamic contributions to net motion independently. This approach is novel because it uses geometric tools to support computational reduction in automatic gait generation on three-dimensional spaces.

Topics: Design
Commentary by Dr. Valentin Fuster
2013;():V002T33A006. doi:10.1115/DSCC2013-4051.

In this paper we focus on the trajectory optimization problem for a specific family of robots; nonholonomic mobile robots. We study the particular case where such robots operate on smooth, non-flat terrains, i.e. terrains with large differences in elevation. Initially we present the governing equations of such robots and then study the trajectory optimization problem in order to solve for the optimal control policy. We test two different approaches for this problem, namely a shooting and a collocation method, for evaluating and optimizing a performance index.

Commentary by Dr. Valentin Fuster

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