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ASME Conference Presenter Attendance Policy and Archival Proceedings

2014;():V04AT00A001. doi:10.1115/IMECE2014-NS4A.
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This online compilation of papers from the ASME 2014 International Mechanical Engineering Congress and Exposition (IMECE2014) 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to ASME’s conference presenter attendance policy, if a paper is not presented at the Conference, the paper will not be published in the official archival Proceedings, which are registered with the Library of Congress and are submitted for abstracting and indexing. The paper also will not be published in The ASME Digital Collection and may not be cited as a published paper.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

Dynamics, Vibration, and Control: Control Theory and Applications

2014;():V04AT04A001. doi:10.1115/IMECE2014-36152.

Micro-motion control on the peak drilling, particularly in 3C industry processing, is difficult for the spindle to precisely follow the high-frequency commands, mainly because the repetitive motion distance is very small and it passes through zero velocity frequently to cause serious problems of friction. Experimental results indicate that the axis is nearly unmoved by applying traditional controllers in practice. By applying the static friction compensation constructed under constant-speed operations, results indicate that it is suitable only when the motion command is slowly-varying in a low frequency range. In this paper, the LuGre model is adopted and a systematic approach is proposed to obtain corresponding modeling coefficients. Results indicate that by applying the controller with the LuGre model, the bandwidth of the velocity loop is greatly improved from 394Hz to 663.7Hz, and the position loop is greatly improved from 9.5 Hz to 113.8 Hz. The LuGre model has also been realized on a DYNA 1007 CNC machine to prove its feasibility. Moreover, the tracking error of its peck drilling is improved 67.5% in RMS and the maximum peak error improvement is 72.0%.

Commentary by Dr. Valentin Fuster
2014;():V04AT04A002. doi:10.1115/IMECE2014-36154.

In this research, it is developed to design LQG controller for wind turbine systems which are identified with Predictor-Based System Identification (PBSID) technique. The PBSID technique works well under closed-loop condition, which is useful for a system requiring closed-loop operation due to safety reason. First, a wind turbine system is identified using PBSID technique in full range of wind speed. Afterwards, using the identified system matrices, 1-DOF LQG controller is designed. The controller enables power generation to track the optimal power trajectory of a system. Simulation is used to demonstrate its usefulness.

Commentary by Dr. Valentin Fuster
2014;():V04AT04A003. doi:10.1115/IMECE2014-37147.

An actuator array is a planar distributed manipulation system that uses multiple two degree-of-freedom actuators to manipulate objects with three degrees of freedom (x, y and θ). This paper presents an accurate method of estimating position and orientation of an object using local sensing and communication. In this method, each of the distributed modules contains a number of binary sensors, weight sensors, and two planar actuators. The binary sensors combined together give a binary image and analog sensors in each module combined together form a grayscale image representation of the weight distribution of the object under manipulation. Additive normalization has been used to combine binary and grayscale distributed sensing images together to come up with increased precision estimates of the position and orientation of an object. A distributed sensing simulation has been developed in Simulink and the effectiveness of this method has been verified for rectangular and circular objects using the Simulink model.

Commentary by Dr. Valentin Fuster
2014;():V04AT04A004. doi:10.1115/IMECE2014-37151.

The field of control and stabilization of distributed parameter systems described by partial differential equations has recently seen an increasing number of results published by very respected researchers in excellent control engineering and applied mathematics journals. This paper presents a survey of control and stabilization results with emphasis on controls. Various distributed parameter dynamic control and stabilization problems have been studied corresponding to heat conduction, wave propagation, Schrodinger equation, crowd (swarm) dynamics, magneto-hydro-dynamic channel flow, string and beam equations, viscous Burger equation, and general diffusion equations. Various techniques have been used for control and stabilization of such systems: Lyapunov stabilization, backstepping, gain scheduling, singular perturbations, sliding mode control, observer driven controller, tracking control, sampled-data control, neural networks. The field still remains widely open for future research. Applications of surveyed results to various areas including robots, aircraft, networks, transmission lines, electrochemical processes in energy systems are indicated.

Commentary by Dr. Valentin Fuster
2014;():V04AT04A005. doi:10.1115/IMECE2014-37238.

In practical control systems, the plant states are not always measurable, so state estimation becomes essential before the state feedback control is applied. In this paper, we consider output feedback model predictive control (MPC) for linear parameter varying (LPV) systems with input constraints. We proposed two approaches to obtain the observer gain, that is to compute the gain in the dynamic optimization at each time instant (on-line), and to compute the gain in advance (off-line), respectively. By applying both approaches, the state estimation error goes to zero asymptotically, meanwhile, the state feedback gain is optimized. In fact, the on-line approach can help enlarge the feasibility region and improve the control performance. It has been shown that feasibility of both approaches can be maintained for the closed-loop control systems even in the presence of state estimation error. Finally, the proposed output-feedback MPC strategies are applied to an angular positioning control system and the control of a transcritical CO2 vapor compression refrigeration system.

Commentary by Dr. Valentin Fuster
2014;():V04AT04A006. doi:10.1115/IMECE2014-37253.

Micro vibration in the ideal-zero gravity environments has complicated science experiment results. A magnetic levitation vibration isolation platform is needed to isolate the vibration source to provide acceptable acceleration level in low frequency range. The configuration of the Lorentz actuators is discussed in the paper. And the modeling of the transformation matrix from the force to the current is deduced. In order to generate desired force, the current is needed to predict precisely. To study the characteristics of the system, the single degree of freedom system is analyzed. A multi-closed loop control scheme is put forward to achieve vibration isolation control. To evaluate the effect of each control parameter, frequency domain analysis of the transfer function is simulated. In order to further increase the control effectiveness, a feed forward compensation control algorithm is added to control the vibration of cables that connect the upper platform and the base. By regulating these control parameters, bode curves can be obtained. Comparing the two methods, it can be concluded that the control method with feed forward compensation is better than the one without that.

Commentary by Dr. Valentin Fuster
2014;():V04AT04A007. doi:10.1115/IMECE2014-37817.

This paper presents a novel Generalized State Dependent Riccati Equation control approach with the purpose of providing a more effective control design framework for continuous time nonlinear systems to achieve a mixed Nonlinear Quadratic Regulator and H control performance criteria. By solving the Generalized State Dependent Riccati Equation, the optimal control solution is found to achieve mixed performance objectives guaranteeing nonlinear quadratic optimality with inherent stability property in combination with H type of disturbance reduction. An efficient computational algorithm is given to find the solution to the Generalized State Dependent Riccati Equation. The efficacy of the proposed technique is used to design the control system for inverted pendulum, an under-actuated nonlinear mechanical system.

Commentary by Dr. Valentin Fuster
2014;():V04AT04A008. doi:10.1115/IMECE2014-37991.

In this paper, a class of uncertain piecewise affine (PWA) systems, subject to system and measurement external disturbances are studied. The uncertainties are assumed to be norm bounded and the external disturbance signals belong to the L2 space. The problem of optimizing the system response in the H sense, by means of a piecewise affine observer-controller, is formulated as an optimization problem subject to a number of constraints in the form of matrix inequalities. The derived constraints are obtained by considering a partially piecewise quadratic Lyapunov function in combination with the general conditions for H stability. Then the uncertain PWA approximation of the nonlinear attitude dynamics of a simplified helicopter model, subject to system and measurement external disturbances, is presented. The uncertainties arise in the form of the difference between the actual nonlinear dynamics and the PWA approximation. Utilizing the introduced methods, a robust PWA observer-controller is designed and implemented on the simplified nonlinear helicopter model to demonstrate the effectiveness of the proposed observer-controller design method.

Commentary by Dr. Valentin Fuster
2014;():V04AT04A009. doi:10.1115/IMECE2014-38932.

In-vitro dynamic knee simulators allow researchers to investigate changes in natural knee biomechanics due to pathologies, injuries or total joint replacement. The advent of the instrumented tibia, which directly measures knee loads in-vivo, has provided a wealth data for various activities that in-vitro studies now aim to replicate [1, 2]. Dynamic knee simulators, such as the Kansas Knee Simulator (KKS), achieve these physiological loads at the joint by applying external loads to either bone ends or musculature. Determining the external loading conditions necessary to replicate activity specific joint loads, obtained from instrumented tibia data, during dynamic simulations are calculated using computational models.

Commentary by Dr. Valentin Fuster
2014;():V04AT04A010. doi:10.1115/IMECE2014-39183.

Fuel cells are sources of clean energy which have become a key enabling technology in a wide spectrum of applications, ranging from automotive and aerospace applications to power supply for off-grid communities. The adequate functioning of a fuel cell requires permanent electrical power delivery to its load, operating at its maximum possible efficiency, even under load variations. Controlling the operating point of the fuel cell to manage changes in load conditions allows extending its service life. Several variables must be monitored and/or controlled to achieve optimal operating conditions of the fuel cell. This work deals with the design of a linear-quadratic-Gaussian, LQG, state-space controller for a proton exchange membrane fuel cell. The LQG controller is commonly used in fuel cell applications because it features an observer which can reconstruct states that are needed for the control strategy and that many times are difficult or too expensive to measure. The tuning of the parameters of the controller is performed by means of genetic algorithms procedures. The goal of the optimization is to prevent low levels of reactant gases due to sudden increases in the load. This will avoid damages to the membrane and other components of the stack while improving the overall performance of the system. The open loop and closed loop system response are presented using the lineal and non-lineal model of the plant. The response of the compensated system using the LQG controller is compared to the response using a basic state space controller, designed by the pole placing method, to assess the robustness of the LQG controller under disturbances. The results demonstrate the ability of the genetic algorithm technique to design a controller that can help preserving the integrity of the fuel cell while optimizing its performance.

Commentary by Dr. Valentin Fuster
2014;():V04AT04A011. doi:10.1115/IMECE2014-40006.

Torsional vibration control of a rotating mechanical system which incorporates a Hooke’s joint is investigated by pole assignment techniques. Linearized analytical models for the torsional system are established for the purposes of controller design. The resulting two-degree-of-freedom rotational system which contains time varying coefficients is parametrically excited due to an inherent non-linear velocity ratio across the Hooke’s joint. The controller is designed via full state feedback and observer based feedback in the transformed domain, using Lyapunov transformation. This transformation reduces the original time-varying system to a form suitable for controller design. A dual-system approach is employed to calculate the observer gain matrix for the time-varying system. Numerical simulation results show that the proposed control method is effective for suppressing torsional vibration of a Hooke’s joint driven system.

Commentary by Dr. Valentin Fuster
2014;():V04AT04A012. doi:10.1115/IMECE2014-40348.

Dynamic compressors are known to suffer from surge, which can severely damage compressor components and disturb production. Surge may arise by the occurrence of disturbances (e.g. compressor discharge valve closure) that would bring its operating point to a region at low flows delimited by the so called surge line (SL). Therefore, dynamic compressors are always equipped with anti-surge mechanisms: typically a fast actuating recycle valve controlled by a PI anti-surge controller. Since surge develops extremely fast, the compressor is usually not allowed to operate too close to the surge line. A surge safety margin is considered, which is the region between the SL and a surge control line (SCL), which may be defined as a line parallel and to the right of the SL. Once the compressor crosses the SCL towards the SL, PI controller action starts. Depending on a number of factors the recommended surge margin adopted may vary. This control objective (keep the compressor away from the SL) is conflicting with energy efficiency requirements, since higher efficiency operating points are located close to the SL. Therefore, it is desirable to operate the compressor using the smallest possible surge margin that still guarantees anti-surge action is effective. In this paper we propose a method for triggering the compressor anti-surge action, aiming at a faster action than traditional PI control, which could enable the adoption of reduced surge margins and operation with higher efficiency. Given a typical single compressor system topology, the possibility of a compressor reaching the surge region coming from a stable operating point can be retrieved through the state of the system actuators. Considering a certain combination of values of the system actuators (compressor suction valve opening, discharge valve opening and motor drive torque), if the steady state operating point (calculated based on a nonlinear variable speed compressor system model) lies to the right of the SCL, then no anti-surge action is necessary. If the resulting steady state lies to the left of the SCL, anti-surge action is deemed necessary and therefore triggered. The proposed anti-surge control method relies on an offline computation of necessary recycle valve openings for each possible combination of the system actuators positions mentioned above, considering a predefined discrete set of values from the actuators positioning ranges. This generates a look-up table for online use. The values from the look-up table are used to trigger a “steady state control action” for the recycle valve that would keep the system stable after transients vanish. They are also used to identify the necessary compressor flow set-point for a feedback controller, which is responsible for ensuring that the system trajectory goes from the state upon anti-surge activation to the desired steady state. The control action from this feedback controller is added to the steady state control action so that its contribution should vanish after transients vanish. A PI and a sliding mode controller are used in feedback control action and results are compared to the traditional anti-surge control approach.

Commentary by Dr. Valentin Fuster
2014;():V04AT04A013. doi:10.1115/IMECE2014-40392.

In this paper, the model of pipe conveying fluid, like marine risers, is modeled with the effect of the interaction between the fluid and structure. A torque is assumed at one end of the pipe to control the vibration of the pipe. The stability of the pipe under time varying disturbance in forced vibration using boundary control law is proved. Exponential stability can be achieved under the free vibration condition. The proposed control law is simple and could be attained by some simple sensors at the end of the pipe. The control law is independent from system parameters so the controller is robust to disturbances and environmental conditions. The controller is obtained via a Lyapunov function in PDE form. Numerical simulations are used to verify the effectiveness of the proposed method.

Commentary by Dr. Valentin Fuster

Dynamics, Vibration, and Control: Design and Control of Robots, Mechanisms and Structures

2014;():V04AT04A014. doi:10.1115/IMECE2014-36052.

Usually, a dynamic system with impact conditions is an interesting problem with practical applications in the fields of dynamics, vibrations, and control. One difficulty in controlling robotics (i.e., a multi DOF two-cooperating or two-link planar) is the subject to impact between the end-effectors of manipulators is that the dynamics (i.e., equations of motion) are different when the system status changes suddenly from a non-contact state to a contact state. In this paper, a Tuned PID controller with different design scenarios is developed to regulate the states of two dynamic systems that collide. Further, in this work, three types of errors are used to compare among different cases that are; (1) the steady state error, (2) the root mean square error, and (3) the final value error. The results of the Tuned PID controller are compared to those obtained by a classical PID controller. The PID controller is tuned using the Ziegler–Nicholas approach. The simulation results of the robotic manipulators confirmed the theoretical effectiveness of the proposed controller, based on MATLAB/Simulink. Unlike the classical PID results (i.e., the impact-induced force is found to be 2.0 N), the Tuned PID controller successfully determined the impact-induced force as same as the desired force (i.e., 0.6 N). Moreover, the Tuned PID satisfied all other desired design values.

Commentary by Dr. Valentin Fuster
2014;():V04AT04A015. doi:10.1115/IMECE2014-36178.

A concussion is a mild traumatic brain injury as a result from a blow to the head. From battlefields to football fields, concussions are unavoidable risks that occur on a daily basis. The goal of this research is to design and test the prototype of a portable concussion assessment device that can offer a quick indication of the state of concussion immediately after the concussion. Approximate Entropy (ApEn) values reflecting the amount of irregularity hiding in center-of-pressure (COP) oscillations will be used to calculate the index. The prototype will adopt a portable design and use the measurements of the load cells located at the four corners of the prototype. The test subject will be asked to stand on the device in normal stance for 30 seconds with their eyes closed. The COP oscillations will then be recorded. Based on the oscillation measurements, the ApEn index will be calculated and quickly displayed to indicate the state of concussion.

Topics: Design , Testing
Commentary by Dr. Valentin Fuster
2014;():V04AT04A016. doi:10.1115/IMECE2014-36358.

Oil and gas refineries present challenging environments in which to work and operate, especially in places like the Middle East where temperatures can reach 50 °C and sand storms which can reduce visibility to a few meters. In addition, there can be gas or steam leaks which present health and safety hazards to the workers. At present, continuous operation of these plants requires that human workers venture out into these conditions in order to observe and report on the conditions within the plant. The goal of this work is to design, fabricate, assemble, and test an inspection robot in an effort to reduce the exposure and risks to human operators while increasing the flexibility and range of remote observations provided by a mobile robot.

In this paper, we will report on the design approach taken, the subsystems identified and developed, the software environment chosen, and the application tasks envisioned. We will also report on the challenges of developing a robust localization algorithm for use in the challenging environment of a refinery as well as the needs for robust wireless communications in order to maintain command and control from the operators control room. An overview of the five-degree-of-freedom arm designed and fabricated, and its real-time control will also be presented. Results from GPS navigation and localization experiments will be presented. While average errors during parked operations were often less than one meter for the WAAS enabled GPS system, locational errors during dynamic operations were often more than three meters. This is due to multi-path signals near building structures and piping infrastructure. Real-time arm control has been implemented using FPGAs and while tuning presented some challenge, the FPGA has provided smooth and repeatable operation. Sensors include gas detectors, acoustic sensors, thermal imaging, and video camera streaming. In addition, we will report on a multi-faceted approach to localization using three different sensor technologies and integrated using a Kalman filter.

Topics: Inspection , Robots
Commentary by Dr. Valentin Fuster
2014;():V04AT04A017. doi:10.1115/IMECE2014-36407.

Automated equipment is used for the ship fabrication process to obtain its higher productivity. However, in the final assembly stage of ship structures, automatic welding system has some constraints on application because of angled and curved surfaces. In order to overcome these constraints, wall climbing mechanism which has mobility and strong adhesion force is necessary. This paper presents an autonomous mobile platform designed for climbing on ferrous 3-D surfaces with welding head. The switchable permanent magnets are used for adhesion, which are capable of adjusting a maximum adhesion force if a variation in the magnetic field strength is required. The mechanism of mobile platform has identical twin bodies, link, flexible rail and sensing devices. Experimental results on the test block verified that the proposed mechanism was feasible and suitable for mobile platform of welding head.

Topics: Manufacturing , Ships , Hull
Commentary by Dr. Valentin Fuster
2014;():V04AT04A018. doi:10.1115/IMECE2014-36564.

The main objectives of a vehicle suspension system are to isolate the road excitations to reach the sprung mass of the vehicle and proper road holding. This paper proposes a solution to optimize a quarter car linear passive suspension parameters while passing over a bump with variable speeds to improve the ride comfort and road holding. The Teaching-learning based optimization algorithm (TLBO) is used to solve the problem and results are compared to those obtained by Genetic algorithm (GA) technique. The quarter car model presented is simulated in time domain subjected to a Cosine speed bump considering the variable speeds of the vehicle over it. Results show sprung mass acceleration, and tire displacement are reduced by 26.03%, and 23.7% respectively by using TLBO and 22.3%, and 18.52% respectively by using GA, conforming the capabilities of the optimization techniques.

Commentary by Dr. Valentin Fuster
2014;():V04AT04A019. doi:10.1115/IMECE2014-36815.

Path generation is to guide a point tracing a prescribed path. Compliant mechanisms (CMs) have been synthesized for path generation mechanisms. In this paper, each connection in a synthesized CM is represented as a variable width spline curve and the entire synthesized CM is modeled as a set of variable width spline curves. The synthesis of a path generation CM is systemized as the optimization of control parameters of a set of variable width spline curves. A variable width spline curve is a center spline curve with variable perpendicular width. The center spline curve is for the shape description of its represented connection while variable width is for the size of the connection. The shape and size of a variable width spline curve is defined by its interpolation circles. The locations of interpolation circles are utilized as interpolation nodes of the center spline curve for connection shape and the diameters of interpolations circles are interpolated for connection size. The centers of all interpolation circles in a synthesized CM form a network of nodes. The network of nodes decides the topology of the synthesized CM and can be classified based on degree of genus (DOG). The presented synthesis approach is demonstrated by synthesizing CMs with different DOGs to generate curved paths.

Commentary by Dr. Valentin Fuster
2014;():V04AT04A020. doi:10.1115/IMECE2014-36864.

Parallel manipulators, compared to serial manipulators, have some interesting properties, such as high stiffness, low inertia, high velocity, good accuracy and large payload capacity. Thus, parallel manipulators, especially the ones with one translation and two rotations as outputs (1T2R), are being increasingly studied. The 3PRS mechanism is a very typical example of this category, but it has accuracy problems caused by the parasitic motion, and low orientation capability. To overcome these problems, new mechanisms are being studied, such as the 2PRU-1PRS manipulator. As the 3PRS manipulator, the degrees of freedom of the 2PRU-1PRS are one translation along the Z-axis and two rotations about the X- and Y-axes. The advantages are that the parasitic motion appears only in one direction instead of in three and that the orientation capability is higher. In this paper we present the design of a 2PRU-1PRS mechanism suitable for vibration tests. In order to do this, we develop a code with an intuitive GUI (graphical user interface) that, for given variable limits, solves the inverse kinematic and dynamic problem for all the variable combinations and obtains the combination that consumes less power for an harmonic trajectory. Taking the simulations results into account, we propose a design that fulfils all the requirements for vibration tests in the three axes.

Commentary by Dr. Valentin Fuster
2014;():V04AT04A021. doi:10.1115/IMECE2014-37043.

This work deals with the design and comparison of two adaptive position control schemes with a classical PID controller for fully constrained and redundant planar robots. First, a novel method based on inclusion of virtual cables facilitates the linear separation of the uncertain parameters from the input-output signals. Then, two Lyapunov based adaptive controllers based on the sliding mode and PD schemes are designed to compensate for the structure matrix uncertainties, which result from errors in the anchor point locations. Finally, the adaptive controllers are evaluated and compared with a classical PID controller through simulations for a desired 2D singularity-free pose of the mobile platform. The simulation results have shown that the adaptive PD control scheme has the best performance for both fully constrained and redundant cases.

Commentary by Dr. Valentin Fuster
2014;():V04AT04A022. doi:10.1115/IMECE2014-37055.

In this paper is described a new solution for a stair-climbing wheelchair: a device that allows disabled people to autonomously overcome architectural barriers. The paper presents the evolution of a project introduced in previous works. The aim is to obtain a wheelchair able to move both in structured and unstructured environments and overcome single steps or an entire staircase.

The innovative aspect of this work is the introduction of a hybrid solution, with a locomotion system based on wheels and an idle track for the vehicle stability.

The locomotion group permits to overcome obstacles through an original architecture based on an epicycloidal transmission. The control logic manages the motors that drive independently the two degrees of freedom of the transmission and allows to switch from an advancing mode to a climbing one.

The wheelchair must be able to move in different environments, such as flat ground or stairs, which require different specifications, sometimes in contrast. For this reason the main part of the work regards the design of a reconfiguration mechanism able to prepare the wheelchair for different working conditions.

First of all the relative positions between the elements that compose the wheelchair structure in different configuration are studied in order to optimize the performances especially in terms of regularity.

Then several possible solutions for the reconfiguration mechanism are presented and qualitatively evaluated, in order to choose the one that satisfy the design specifications.

Topics: Stairs , Design , Wheelchairs
Commentary by Dr. Valentin Fuster
2014;():V04AT04A023. doi:10.1115/IMECE2014-37057.

Cable-based robots generally perform better than other parallel robots with rigid links in terms of wider workspace and higher acceleration of end effector because of lightweight of robot links. Cable based robots allow an easy mounting and remounting for outside applications; however, this requires a precise assembly of components at the cable anchor points. In this study, firstly a parametric model is developed for estimation of position errors of anchor points for fully-constrained and redundant planar cable robots. A novel method based on inclusion of virtual cables facilitates the linear separation of the uncertain parameters from the input-output signals for redundant planar robots. In addition, the adaptive law (parameter estimator) updates the estimated parameters using the least squares algorithm. The simulation results show that the least squares method reduces the time of estimation convergence compared to gradient algorithms. Furthermore, the least squares method allows simple persistent excitation signals to estimate parameters.

Topics: Robots , Cables
Commentary by Dr. Valentin Fuster
2014;():V04AT04A024. doi:10.1115/IMECE2014-37081.

In this paper, kinematic and dynamic models are derived for a forklift-like four-wheeled mobile robot, and then, based on the models, a new trajectory control scheme is designed and evaluated for the robot. The dynamic model, exhibiting non-minimum-phase characteristics, is derived by applying Lagrange’s equations and then the control law is design by using Lyapunov stability theorem and the loop shaping method. The proposed control scheme consists of a trajectory generator, a motion control law, and a steering control law. First, a real-time trajectory generator is designed based on the nonholonomic kinematic constraints of the robot, in which the reference driving speed and time rate of heading angle are computed in real time for a given desired trajectory of the robot. The proposed trajectory generator guarantees a local asymptotic stability. Next, motion and steering control laws are designed based on the dynamic model of the robot. The motion and steering control laws are used to control the robot speed and steering angle. The proposed control guarantees asymptotic stability of the trajectory control while keeping all internal signals bounded. Finally, the validity of the proposed control scheme is shown by realistic computer simulations with one sampling-time delay in the control loop.

Commentary by Dr. Valentin Fuster
2014;():V04AT04A025. doi:10.1115/IMECE2014-37116.

Mobile platforms that make use of concurrent localization and mapping algorithms have industrial applications for autonomous inspection and maintenance, such as the inspection of flaws and defects in oil pipelines and storage tanks. An important component of these algorithms is feature extraction, which involves detection of significant features that represent the environment. For example, points and lines can be used to represent features such as corners, edges, and walls. Feature extraction algorithms make use of relative position and angle data from sensor measurements gathered as the mobile vehicle traverses the environment. In this paper, sound navigation and ranging (SONAR) sensor data obtained from a mobile vehicle platform are considered for feature extraction and related algorithms are developed and studied. In particular, different combinations of commonly used feature extraction algorithms are examined to enhance the representation of the environment. The authors fuse the Triangulation Based Fusion (TBF), Hough Transfrom (HT), and SONAR salient feature extraction algorithms with the clustering algorithm. It is shown that the novel algorithm fusion can be used to capture walls, corners as well as features such as gaps in walls. This capability can be used to obtain additional information about the environment. Details of the algorithm fusion are discussed and presented along with results obtained through experiments.

Commentary by Dr. Valentin Fuster
2014;():V04AT04A026. doi:10.1115/IMECE2014-37602.

This work focuses on the bond graph modelling method and its application on multi-body system, especially on the five-bar parallel robot. Five-bar parallel robot is comprised of four arms, two revolute actuators and five revolute joints. This paper adopts five-bar parallel robot in symmetric configuration as simulation object. As it will be used as a pickup and placing machine, its workspace is fixed on Cartesian coordinate. The relationship between the two rotating angles and end effector’s desire position is built by inverse kinematics. Bond graph is used to describe moment, torque, velocity, angle relationships. In this project, the dynamic performances between arms, motors at robot basement and end effector will be researched. In this paper, an investigation about how to use bond graph to model DC (direct current) servo motor and an integrated motion control system is carried out. During a typical end effector point-point displacement, the torque change between arms is plotted. Finally, 3-D animation experiment is conducted. Experiment results show that bond graph can simulate robot dynamics performance without having to make a large number of equations. It is able to simulate and solve five-bar kinematics problem in the process.

Commentary by Dr. Valentin Fuster
2014;():V04AT04A027. doi:10.1115/IMECE2014-37700.

This paper presents a method for kinematic retargeting that is general to a broad class of kinematic chains. Kinematic retargeting is the adaptation of a pose or motion from one kinematic embodiment to another. Our method distinguishes itself in its ability to adapt poses to new robots with very little configuration by the user. We accomplish this by defining two general metrics for retargeting and minimizing a cost function which is the weighted sum of these two metrics. This allows the method to automatically adapt poses between source and target chains that have different link lengths and degrees of freedom.

These capabilities address a specific problem in Human-Robot Interaction (HRI), where behaviors are often defined in a robot-specific manner. The ability to automatically adapt behaviors from humans to new robots, and from one robot to another, will facilitate experimental repeatability. Through simulation and experiments, we demonstrate that our method is effective in adapting poses across chains with different numbers of joints, and in adapting socially expressive gestures from a human to two very different robots.

Topics: Kinematics , Robots
Commentary by Dr. Valentin Fuster
2014;():V04AT04A028. doi:10.1115/IMECE2014-37791.

An adaptive output feedback controller for electrically-driven robot manipulators is developed in this paper. The proposed controller can compensate for parametric uncertainties while only requiring link position measurements. To eliminate the need for measuring link velocity and electrical winding current, two individual observers are used as a surrogate for unmeasurable quantities: one for joint velocity estimation, and another for motor current estimation. Based on these observers, a modified adaptive integrator backstepping procedure is utilized to design input voltage which guarantees semiglobal asymptotic link position/velocity tracking in spite of the mechanical parametric uncertainties and lack of link velocity and rotor current measurements. The main novelty of our presented work lies in simultaneous estimation of joint velocities, rotor currents, and mechanical uncertainties to produce a controller which provides a system level input, the voltage to an electric actuator, to control the link position/velocity of electrically-driven robot manipulators.

Commentary by Dr. Valentin Fuster
2014;():V04AT04A029. doi:10.1115/IMECE2014-38074.

In this paper, an augmented image based visual servoing (AIBVS) using image moment features is proposed to improve the visual servoing performance. The AIBVS controller produces acceleration as the controlling command. In order to generate the acceleration command, a general analytical formulation for calculating interaction matrix relating the image moments features to camera acceleration is derived. A proportional derivative (PD) controller is developed to provide the controlling command of the robot. Using the derived interaction matrix this controller can achieve smoother feature trajectory in image space and reduce the amount of overshoot that appears in the response of the system. The developed control method also enhances the camera trajectory in 3D space. Simulation tests on three image moments sets, proposed by Chaumette [1], Tahri et al. [2] and Liu et al. [3], are performed on a 6 DOFs robotic system to validate the effectiveness of the proposed controller.

Commentary by Dr. Valentin Fuster
2014;():V04AT04A030. doi:10.1115/IMECE2014-38162.

In this paper a boat simulator is designed using parallel manipulators. The simulator allows the training of five or seven people in a river environment. Due to the high payload and high inertial forces, it was proposed to divide the simulator into various synchronized platforms. Additionally different configurations of mechanisms were evaluated as well as linear or rotational actuation. The dimensional synthesis was performed by introducing a power index based on the Virtual Work equations of motion, and applying Genetic Algorithms for optimization. This design process results in using two coordinated manipulators with rotational actuators. The first one has two degrees of freedom (pitch and roll); it will simulate the motion of the boat’s stern. The second one has three degrees of freedom: pitch, roll and heave; and simulates the motion of the boat’s bow. The detail design was concluded and the manipulators were built. A real time controller is under design nowdays and the integration of the fluid and the boat dynamics into the inverse dynamics analysis of the manipulators is proposed as future work.

Topics: Design , Manipulators , Boats
Commentary by Dr. Valentin Fuster
2014;():V04AT04A031. doi:10.1115/IMECE2014-38548.

Most modern navigation systems solve the localization problem by extensively using global positioning system (GPS) data. Unfortunately the GPS data quality depends on several factors, which can lead to large positioning errors. Known GPS errors fall in two groups: either atmospheric errors, or multipath errors. Because of these errors, differential GPS systems have been developed using both ground based and satellite based reference systems. The cost of a differential GPS unit such as a Novatel range from a little over $2000 to over $9000, which can be prohibitive for use on certain home service robotic vehicles such as autonomous snow plows or autonomous lawn mowers. This paper discusses ways of mitigating GPS errors on low cost single frequency GPS units such as Copernicus II, Skytraq and U-Blox, which cost far less than $100 each, and hence are attractive for use in many robotic applications such as those mentioned above. The paper will present a model of GPS noise and use that model to process GPS data for use in navigation of an autonomous snow plow designed for use in residential driveways and side-walks; it will be supported by experimental results only.

Commentary by Dr. Valentin Fuster
2014;():V04AT04A032. doi:10.1115/IMECE2014-38553.

The Advanced Fiber Placement (AFP) machines have brought significant improvement on the manufacturing of composite. However, the current AFP machines are not capable of handling some applications with more complex shapes. This paper presents a collaborative AFP machine which consists of a 6-RSS parallel platform, a 6-DOF manipulator and a spindle mounted on the platform to hold the mandrel. The collaborative modeling is built and simulated in SimMechanics/Matlab. The inverse kinematic models are established for trajectory planning. In addition, the workspaces of both parallel robot and collaborative AFP machine are analyzed using geometrical method and programmed in Solidworks. A simulation example for the manufacturing of a hemisphere is provided. The result shows that the collaborative AFP machine could enlarge the manufacture workspace, simplify the trajectory planning and enhance the productive efficiency.

Topics: Machinery , Fibers , Modeling
Commentary by Dr. Valentin Fuster
2014;():V04AT04A033. doi:10.1115/IMECE2014-38564.

This article discusses the design and implementation of two Matlab graphical user interfaces (GUIs) for mechanism synthesis. The first GUI addresses the four location Burmester synthesis problem. The designer specifies the 4 locations that are used to generate the Burmester curves for these prescribed locations. The GUI enables the designer to interact with these curves and choose a pair of moving and fixed pivots forming an RR dyad. The second GUI addresses dimensional synthesis of RR dyads for hybrid motion generation tasks. Given a hybrid motion generation task, the designer can either pick the fixed or moving pivots and the corresponding pivots of an RR dyad is determined. In both the interfaces, the designer is provided with tools to specify tasks. The GUIs were designed with an objective to provide the designer with a simple workflow. Design case studies that illustrate the features and capabilities of each GUI are included.

Commentary by Dr. Valentin Fuster
2014;():V04AT04A034. doi:10.1115/IMECE2014-38565.

Autonomous navigation of ground vehicles is a growing research area. Skid steered wheeled ground vehicles are of interest because of the system’s relatively easy control parameters. Steered wheels require actuation and control for the steering and speed of the steered wheels while skid steering just requires actuation and control of the wheel speeds, usually just a left and right wheel speed. Four Wheeled differentially steered vehicles are built primarily for straight line motion since the instantaneous centers of zero velocities for the four wheels are always at infinity when there is no sliding in the wheels. When the vehicle has to negotiate a corner, it uses the differential velocities between sides to force the wheels to slide and perform the cornering maneuver. Maneuvering is difficult when the ground friction is very high because of undue stresses in the axle structure. This paper analyses the dynamics of such vehicles that relates the traction and skid friction forces and proposes a suitable control system. At this time, the paper is supported by simulation results while experimental work is still going on.

Commentary by Dr. Valentin Fuster
2014;():V04AT04A035. doi:10.1115/IMECE2014-38574.

This paper presents a methodology of vision-based pose and motion estimation of non-cooperative targets as well as a control scheme for robotic manipulators to perform autonomous capture of non-cooperative targets. A combination of photogrammetry and extended Kalman filter is proposed for real time state estimation of the non-cooperative target. Once the vision-based estimation is obtained, a real state of the target regarding to the global frame is calculated based on the transformation matrices of coordinate frames. So as to make a capture, a desired state of the end effector is defined in accordance with the real state of the target aforementioned, and further a corresponding desired state of the robotic manipulator is derived by inverse kinematics. Then a close-loop control scheme is adopted to drive the robot to the desired state previously obtained. Experiments have been designed and implemented on a custom built six degrees of freedom robotic manipulator with an eye-in-hand configuration. The experimental results demonstrated the feasibility and effectiveness of the proposed methodology and control scheme.

Commentary by Dr. Valentin Fuster
2014;():V04AT04A036. doi:10.1115/IMECE2014-38639.

Mobile robots consist of a mobile platform with manipulator can provide interesting functionalities in a number of applications, since, combination of platform and manipulator causes robot operates in extended work space. The analysis of these systems includes kinematics redundancy that makes more complicated problem. However, it gives more feasibility to robotic systems because of the existence of multiple solutions in a specified workspace. This paper presents a novel combination of evolutionary algorithms and artificial potential field theory for motion planning of mobile manipulator which guaranteed collision and singularity avoidance. In the proposed algorithm, the developed concepts of potential field method are applied to obstacle avoidance and interaction of mobile base with manipulator is used as a new idea for singularity avoidance ability of intermediate links for mobile operations. For this purpose, kinematic and dynamic modeling is derived to define redundant solutions. Afterward, methods from potential field theory combine with evolutionary algorithms to provide an optimum solution among possibly of redundancy resolution scheme. A controller based on dynamic feedback linearization is augmented to track the selective motion trajectory. Simulation results verify obstacle avoidance, singularity avoidance for the manipulators and asymptotic convergence of the robots errors.

Commentary by Dr. Valentin Fuster
2014;():V04AT04A037. doi:10.1115/IMECE2014-38641.

In this paper the kinematics and dynamics of a uniball robot is demonstrated. The motion of a uniball robot is derived from the dynamics of a sphere rolling on a surface which is considered as a motion about a fixed point. The equations of motion are derived using Newton-Euler method incorporating the geometrical features of the surface. A uniball-robot can be considered as a Routh’s sphere whose center of mass is not at the geometrical center and have equal principal moments of inertia in the plane perpendicular to the axis connecting the center of mass and the geometrical center. The Euler angles are obtained using the Meusnier’s theorem which deals with the evolution of the surface as the robot moves along.

Commentary by Dr. Valentin Fuster
2014;():V04AT04A038. doi:10.1115/IMECE2014-39036.

We present an underactuated approach for steering a vehicle which reduces the number of required servos. This method replaces steering servos with braking actuators which can reduce energy use, weight and support electronics. The design of the steering system, the control system and comparison to traditional steering is considered.

Topics: Vehicles , Braking
Commentary by Dr. Valentin Fuster
2014;():V04AT04A039. doi:10.1115/IMECE2014-39047.

This paper presents a new reactive power-based performance index of planar mechanisms. This index quantifies how much of the power introduced to a mechanism is transformed into motion. Generally, the mechanical advantage is used as an index to quantify the force or the velocity ratio between the input and the output link of a mechanism. However, this index is sensitive to the dimensions of the inlet and outlet of the mechanism so it cannot be used for the comparison of different types of mechanisms. To overcome the drawback of the physical inconsistency, the concept of reactive power is proposed to quantify the losses that occur in a mechanism and, based on this concept, the reactive power-based index is defined. The proposed approach is applied to various mechanisms and it is compared with the mechanical advantage to observe that the proposed index provides the same information as the mechanical advantage, but being dimensionally consistent for the analyzed cases (dimensionless in all cases), it can be used to the analysis, comparison and optimal design of different planar mechanisms.

Topics: Dimensions , Design
Commentary by Dr. Valentin Fuster
2014;():V04AT04A040. doi:10.1115/IMECE2014-39136.

Industrial robotic arms are widely used nowadays. Accuracy and efficiency that fulfill user’s requirements are achieved through robust controller. This paper investigates dynamics modeling and control of a four DOF (PRRR) robot that is dedicated to perform a Pick-and-Place move of a certain product. The arm is undergoing manufacturing process. Forward and inverse kinematics solutions are introduced to solve the joint space trajectories associated with the desired End Effector (EE) Cartesian space path. The performance of two controllers under the presence of model uncertainties is inspected through a simulation study; Non-Linear Feedback Control (NLFC) and Sliding Mode Control (SMC) are designed and tested over the required joint space trajectories and Cartesian space path. Results showed that NLFC achieved better results than SMC in terms of RMSE when model uncertainties were absent. However, when model uncertainties were introduced, SMC performance was more robust than NLFC. Simulation results are very encouraging towards using the SMC over the actual robotic arm.

Commentary by Dr. Valentin Fuster
2014;():V04AT04A041. doi:10.1115/IMECE2014-39326.

This paper describes the design of a child humanoid robot hand with SMA actuators and servo motors. Human hands can grasp and manipulate complicated objects relying on its flexible structure and real-time control. However, it is difficult to replicate an exact human hand using rigid structures because of intricate biomechanical structure. In human hand, one metacarpal and three phalanges make up each finger, except for the thumb which only has two phalanges. Each finger except the thumb is composed of 3 joints: the metacarpophalangeal (MCP), the proximal interphalangeal (PIP) and distal interphalangeal joints (DIP). The DIP and PIP joints are always moving simultaneously, while the MCP joint can move independently. The child-sized robot hand is developed which replicates a seven year-old child’s hand in its fundamental structure. The robot hand has five fingers and all the fingers consist of 3 links. Servo motors and shape memory alloy actuators were used as a drive mechanism for the fingers and mathematical model of the SMA actuators are described to study the finger dynamics. A prototype humanoid robot hand was fabricated using 3D printing techniques and experimental results are presented.

Commentary by Dr. Valentin Fuster
2014;():V04AT04A042. doi:10.1115/IMECE2014-39545.

Simulation of robot systems is getting very popular, especially with the lowering cost of computers. The robotic arm is presumably the most mathematically complex for the dynamic and kinematic analysis. The purpose of this paper is to build a simulation framework for a 3R robotic arm using PTC Creo Parametric 2.0 and also to identify its advantages and disadvantages for such analysis. Trajectory of the robotic arm is optimized by considering the shortest path as an objective function between the initial and final position which results in straight line motion using an effective optimization technique known as Teaching learning based optimization (TLBO). Intermediate positions of the optimized results are taken as an input for the simulation of the 3R robotic arm in PTC Creo Parametric 2.0. The results obtained by using TLBO and PTC Creo Parametric 2.0, such as angular positions, joint velocities and joint accelerations are compared based on RMS errors. The verification of the obtained results by both the methods allows us to qualitatively evaluate, underline the rightness of the chosen model and to get the right conclusions.

Topics: Simulation , Robotics
Commentary by Dr. Valentin Fuster
2014;():V04AT04A043. doi:10.1115/IMECE2014-39840.

In this paper a magnetic levitation system is modeled and an eddy current based damping force is identified and used for position control of the levitated object in the system. In the magnetic levitation technology, contactless manipulation of a levitated object is done by use of magnetic fields. Also, the eddy-current based force is used to damp the motion of the levitated object. Eddy-current is generated in a plate which is placed underneath the levitated object due to the change of current in an electromagnet and the motion of the levitated object.

First, using finite element method (FEM), the magnetic levitation system is modeled and the eddy-current based force acting on the levitated object is obtained. The thickness of the plate and the magnetic dipole moment of the levitated object are optimized so that the maximum value of the eddy current based force is gained. The effect of the eddy-current based force on the 2-D motion of the levitated object is studied. Also a controller using the damping effect of the eddy force is designed to control the position of the levitated object in one particular dimension. Results show that the controller can effectively regulate the position of the levitated object.

Commentary by Dr. Valentin Fuster

Dynamics, Vibration, and Control: Dynamics and Control in Micro/Nano Engineering

2014;():V04AT04A044. doi:10.1115/IMECE2014-37986.

Nonlinear vibration of nanobeam with the quadratic rational Bezier arc curvature is investigated. The governing equation of motion of the nanobeam based on the Euler-Bernoulli beam theory is developed. Accordingly, the non-uniform rational B-spline (NURBS) is implemented in order to write the implicit form of the governing equation of the structure. The simply-supported boundary conditions are assumed and the Galerkin procedure is utilized to find the nonlinear ordinary differential equation of the system. The nonlinear natural frequency of the system is found and the effects of different parameters, namely, the waviness amplitude, oscillation amplitude, aspect ratio, curvature shape and the Pasternak foundation coefficient are fully investigated. The hardening and softening responses of the natural frequency of structure are detected for variations of the shape and amplitude of the curvature waviness. It is revealed that the ratio of nonlinear to linear frequency increases with an increase in the oscillation amplitudes. It is found that by increasing the Pasternak foundation coefficient, the ratio of nonlinear to linear frequency decreases.

Commentary by Dr. Valentin Fuster
2014;():V04AT04A045. doi:10.1115/IMECE2014-38217.

This paper deals with MEMS resonator sensors under double electrostatic actuation. The system consists of a MEMS cantilever between two parallel fixed plates. The frequencies of actuation are near natural frequency and near half natural frequency. The frequency response of the simultaneous resonance of the structure is investigated using Reduced Order Model (ROM) method.

Commentary by Dr. Valentin Fuster
2014;():V04AT04A046. doi:10.1115/IMECE2014-38386.

This paper presents results obtained numerically by an experimental approach. The sensor of the atomic force microscope generated cantilever deflections series that were recorded in data files as a function of time and as a function of tip-sample distance. With these series of deflections, we attempted to adjust parameters and refine models of classical oscillators atomic force microscope, making them more sensitive to tip-sample distance, through the method of system identification proposed by [12]. This method allows us to choose any model and, through its analytical solution, compare the results obtained with the experiment. The reconstruction of the state space is done with the intention of observing different phase portraits for different distances between sample-tip.

Commentary by Dr. Valentin Fuster
2014;():V04AT04A047. doi:10.1115/IMECE2014-38509.

In this paper, the nonlinear model of an asymmetric micro-bridge resonator with an attached eccentric mass is investigated. The resonator is treated using the Euler-Bernoulli beam theory. The attached mass represents the electrostatic comb-drive actuator in micro-electromechanical applications. The center of mass of the actuator is assumed to be off the neutral axis of the beam. The governing equations of motion are derived assuming that a concentrated harmonic force is applied to the attached mass. The nonlinear forced vibration of the system is studied using the method of multiple scales. It has been demonstrated that the eccentricity of the mass may lead to different types of nonlinear resonance, e.g., superharmonic and internal resonance. The end application of the structure under investigation is in resonant sensing and energy harvesting applications.

Topics: Vibration
Commentary by Dr. Valentin Fuster
2014;():V04AT04A048. doi:10.1115/IMECE2014-38957.

The nonlinear free vibration of multi-layered nano-scale graphene sheets is studied. Using the von Kármán and nonlocal continuum theories, large amplitude of vibration is included in the analysis as well as the size effect of nano-structure. The SSSS boundary condition is considered for the multi-layered graphene sheet and coupled nonlinear differential equations of motion of layers are taken into account based on Galerkin method. Variational iteration method (VIM) is employed as the solution procedure and nonlinear natural frequencies of the system are analytically determined. Two different geometries are taken into account and the analytical results are compared with frequencies obtained by numerical method. Finally, influence of geometrical parameters and amplitude of vibration on nonlinear frequencies of the system is examined.

Commentary by Dr. Valentin Fuster
2014;():V04AT04A049. doi:10.1115/IMECE2014-39835.

Design and control of micro robots have been one of the interesting fields in robotics in recent years. One class of these micro robots is the legged robots. Various designs of legged robots have been proposed in the literature. All designs rely on friction for locomotion. In this paper dynamic model of a planar two-legged micro robot is presented using Luger friction model, and an adaptive neural controller used to control the robot to improve robustness and velocity of the robot.

As mentioned earlier, friction plays an important role in locomotion of the legged robots. However, especially in legged micro robots, it is difficult to model the frictional force correctly since environmental disturbances like dust and changes in shape of the test bed can significantly alter its value. Therefore, one needs to design a controller that adapt to new condition and had enough robustness so one chooses neural network controller. Result show that with updating weight of neural network robot could follow desired trajectory, and with change in friction coefficient training time was low enough to update weight at each step.

Commentary by Dr. Valentin Fuster

Dynamics, Vibration, and Control: Dynamics Modeling, Theory and Application

2014;():V04AT04A050. doi:10.1115/IMECE2014-36007.

Passive vibration isolators are extensively used in wide ranging applications such as automotive, aerospace, railroad and earth moving equipment in the mechanical industry, and in structural applications in the civil industry. These isolators serve as spring-damper units that isolate specific parts of a system from external dynamic loading, or from other sub-systems that cause vibration excitation. Passive isolators exhibit very complex behavior that depends on excitation frequency, displacement amplitude, ambient temperature and pre-load in addition to geometry, design features as well as material composition of the isolator. Various models are prevalent in the existing literature for the design and analysis of such isolators, ranging from the basic Voigt model to more complex models such as the Maxwell-Voigt model with multiple Maxwell elements, the Maxwell ladder model, the three dimensional viscoelastic model, the fractional derivative model, and models specifically used for capturing the hysteresis behavior or the displacement limiting behavior. However, each of these models is successful in representing certain characteristics of the isolator while being unable to capture other key attributes. This paper provides a comparative study of some of the main models that are commonly used for the design and analysis of passive vibration isolators. Experimental data collected from a passive elastomeric isolator under varying excitation conditions is used to identify parameters associated with some of the commonly used models. The analysis results are compared and specific highlights and shortcomings of each model are identified and discussed.

Commentary by Dr. Valentin Fuster
2014;():V04AT04A051. doi:10.1115/IMECE2014-36286.

The increasing complexity in the development and manufacturing process of internal combustion engines leads to a higher demand for more effective testing and monitoring methods. Cold engine testing becomes progressively the main End-of-Line test which is used nowadays from automotive engine manufacturers with the purpose of determining the integrity of engine assembly. The present work is focused on the development of a detailed physics-based, lumped-parameter, dynamic model of a single cylinder internal combustion engine coupled with an alternating current transient dynamometer for cold engine testing applications. The overall transient engine test cell model is described based on a two-inertia system model consisting of the engine, the dynamometer and the coupling shaft. The internal combustion engine is modelled based on First Law of Thermodynamics and Second Newton’s Law for rotational bodies. The transient dynamometer is actually an alternating current three-phase induction motor which is modelled according to direct-quadrature axis approach, and its drive unit which is responsible for controlling the speed of the motor using indirect field orientation scheme. The engine and dynamometer are connected through a coupling shaft which is modelled as a compliant member with damping. The model is validated against experimental measurements such as engine cylinder pressure, engine excitation torque and alternating currents of the induction motor. All of the experimental measurements were recorded from an identical single cylinder transient engine test cell using a highly advanced instrumentation system. The described model serves as an ideal platform for developing innovative model-based fault detection and diagnosis techniques for cold engine testing applications. In conclusion, this is presented successfully for two simulated fault cases, a process fault and a sensor fault, proving the functionality and usefulness of the model.

Commentary by Dr. Valentin Fuster
2014;():V04AT04A052. doi:10.1115/IMECE2014-37150.

Galfenol, a novel magnetostrictive and ferromagnetic material, has been employed in various applications because of the material’s outstanding mechanical properties. For high frequency applications, the energy loss of eddy-current is a critical criterion because this loss not only reduces the power efficiency for Galfenol material, but also rapidly generates large amounts of heat that can destabilize the system. While laminating ferromagnetic material has been proved to be an effective way that minimises eddy-current, the objective of this research is to investigate the laminated Galfenol material’s plausibility in high frequency applications. For the prescribed geometry, an accurate model for the generated eddy-current is derived based on the Maxwell equations. Combining a built magnetic coupled dynamic model, the relationship between the strain response and the applied magnetic field is derived under high frequency conditions. The simulative results of the laminated Galfenol rods are compared to those rods without laminations. The comparison shows that the laminated Galfenol rod exhibits a milder hysteresis than the non-laminated Galfenol rod. Furthermore, the laminated Galfenol rod is able to maintain a high strain output with a broader frequency range compared to the non-laminated Galfenol rod. This work proves that laminating Galfenol rods are capable of restricting the generation of eddy-current and improving high frequency characteristics significantly.

Commentary by Dr. Valentin Fuster
2014;():V04AT04A053. doi:10.1115/IMECE2014-37880.

Bearing performance significantly affects the dynamic behaviors and estimated working life of a rotating system. A common bearing type is the ball bearing, which has been under investigation in numerous published studies. The complexity of the ball bearing models described in the literature varies as models with or without the inclusion of centrifugal forces or the gyroscopic moments of the rolling elements are equally proposed. Naturally, model complexity is related to computational burden. In particular, the inclusion of centrifugal forces and gyroscopic moments significantly increases the system degrees of freedom and lengthens solution time. On the other hand, for low or moderate rotating speeds, these effects can be neglected without significant loss of accuracy.

The objective of this paper is to present guidelines for the appropriate selection of a suitable bearing model for a case study. To this end, two ball bearing models were implemented. One considers high-speed forces, and the other neglects them. Both models were used to study a single structure, and the simulation results were compared. The bearing behavior is studied at different shaft rotation speeds and the simulation results are used to determine when the model containing the centrifugal and gyroscopic forces should be used.

Topics: Ball bearings
Commentary by Dr. Valentin Fuster
2014;():V04AT04A054. doi:10.1115/IMECE2014-37992.

Prior research has shown that the design of a vehicle’s structure has a substantial impact on its overall performance under static loading [1], since the structure affects other components of the vehicle aside from the body. In addition to the past research, dynamic loading is added in this paper as a parameter for design. Bending stiffness and weight are still important factors to consider, since a stiffer structure (higher stiffness) means longer life and stability. A lighter vehicle translates to better fuel economy, lower cost and higher performance. Simple Structural Beams are used to model the structure, where several beam elements are used in the setup. The cross-section properties are analyzed to determine the structure’s weight, bending stiffness, natural frequency and amplitude of vibration. In order to find an acceptable solution, the design must avoid the possibility of resonance. Vibration has a large impact on a structure’s performance, the larger the amplitude, the more uncomfortable the ride is. The goal of this research is to obtain a design that will optimize for vibration and for bending stiffness and weight. The purpose of the optimized design is to provide the best performance and most comfortable ride to the driver. The optimization process is automated iteratively and solves for the beam dimensions that correspond to the optimized parameters.

Commentary by Dr. Valentin Fuster
2014;():V04AT04A055. doi:10.1115/IMECE2014-38032.

Passive magnetic bearings are known due to the excellent characteristics in terms of friction and no requirement of additional energy sources to work. However, passive magnetic bearings do not provide damping, are not stable and, depending on their design, may also introduce magnetic eccentricity. Such magnetic eccentricities are generated by discrepancies in magnet fabrication. In this framework the main focus of the work is the theoretical as well as experimental investigation of the non-linear dynamics of a rotor-bearing system with strong emphasis on the magnetic eccentricities and non-linear stiffness.

In this investigation passive magnetic bearings using axially-aligned neodymium cylinder magnets are investigated. The cylinder magnets are axially magnetised for rotor as well as bearings. Compared to bearings with radial magnetisation, the magnetic stiffness of axially-aligned bearings is considerably lower, nevertheless they allow for asymmetric stiffness mounting, and it could be beneficial for rotor stabilization.

A theoretical model is proposed to describe the non-linear rotor-bearing dynamics. It takes into account non-linear behaviour of the magnetic forces and their interaction with a multi-body system composed of rigid rotor and flexible foundation. The magnetic eccentricities of the shaft magnets are modelled using the distances (amplitudes) and directions (phase angles) between the shaft axis and the centre of the magnetic fields generated. A perturbation method, i.e. harmonic balancing, is used in order to evaluate the frequency response of the non-linear system.

The experimental validation of the model is carried out using a dedicated rotor-bearing system set-up. The test set-up consists of a vertical rigid shaft and disc supported by two passive magnetic bearings using axially-aligned neodymium cylinder magnets. The magnetic bearing housings are flexibly supported, allowing horizontal motions. The housings are connected to each other by means of elastic beams. The shaft is free in one end and coupled to a DC motor on the other by means of a flexible coupling. On the free end a disc is attached where imbalances and gyroscopic effect can be generated.

Comparison between theory and experiment shows high level of resemblance, which validates the theoretical model and the explanations for the quasi-static and dynamic responses. The magnetic eccentricities and mass imbalance effects are clearly detected and distinguished.

Commentary by Dr. Valentin Fuster
2014;():V04AT04A056. doi:10.1115/IMECE2014-38498.

In this paper, dynamic modeling and slippage analysis of a three-link soft finger manipulating a rigid object on a horizontal surface is studied. In order to integrate the dynamics of soft tip with the finger linkage, power-law model and a linear viscous damper are used to model the elastic behavior and damping effect of soft tip respectively. Because of the enlarged contact area in the soft contact, a frictional moment can be exerted at the contact interface along with the normal and tangential forces. Furthermore, because of planar motion of object, frictional forces and moment are applied in the contact of object and ground. Therefore, friction limit surface is used as a mapping between contact forces/moment and sliding motions in both contacts. Instead of using equality and inequality equations of frictional contact conditions, a method is proposed to describe different states of the contact forces and moment by a single second-order differential equation with variable coefficients. This kind of formulation of the system dynamics facilitates the design of a controller to cancel the undesired slippage occurs between the soft tip and object during the manipulation.

Commentary by Dr. Valentin Fuster
2014;():V04AT04A057. doi:10.1115/IMECE2014-38568.

In paper, we build up a simulation program using the nodal position finite element method for the dynamic analysis of the electrodynamic tether system; the model equation is derived from the principle of virtual work. The aerodynamic drag force, gravity force and electrodynamic force are considered. The following models are used, respectively. The NRLMSISE-00 (NRL mass spectrometer, incoherent scatter radar extended model) for the atmosphere density, EGM-2008 (Earth Gravity Model) for the earth gravity field, IGRF-2010 (International Geomagnetic Reference Field) for the earth geomagnetic field, and the IRI-2011 (International Reference Ionosphere model) for the plasma electron density. Two simplified cases of boundary condition are assumed to the governing equation of induced current and voltage, one is for giving the current of anode point just as an input parameter, and the voltage drop in the negative segment is out of consideration; the other one is called full power condition. The program is verified by considering conservative force in the circular orbit, its result shows that the nodal position finite element method is suitable for the long term simulation.

Commentary by Dr. Valentin Fuster
2014;():V04AT04A058. doi:10.1115/IMECE2014-39402.

Recently, there have been a number of research activities on spur gears with asymmetric teeth. The benefits of asymmetric gears are: higher load capacity, reduced bending and contact stress, lower weight, lower dynamic loads, reduced wear depths on tooth flank, higher reliability, and higher efficiency. Each of the benefits can be obtained through asymmetric teeth designed correctly. Gears operate in several conditions, such as inappropriate lubrication, excessive loads and installation problems. In working conditions, damage can occur in tooth surfaces due to excessive loads and unsuitable operating conditions. One of the important parameters of the tooth is stiffness, which is found to be reduced proportionally to the severity of the defect by asymmetric tooth design as described in this paper. The estimation of gear stiffness is an important parameter for determining loads between the gear teeth when two sets of teeth are in contact. In this paper, a 2-D tooth model is developed for finite elements analysis. A novel formula is derived from finite element results in order to estimate tooth stiffness depending on the tooth number and pressure angle on the drive side. Tooth stiffness for spur gears with asymmetric teeth is calculated and the results were compared with well known equations in literature.

Commentary by Dr. Valentin Fuster

Dynamics, Vibration, and Control: Dynamics of Structures With Contact and/or Frictional Interfaces

2014;():V04AT04A059. doi:10.1115/IMECE2014-37198.

Lateral whirl vibrations in long sections of horizontal oilwell drillstrings, which are essentially enclosed shafts lying on the low side of the wellbore, are potentially destructive to the bit, pipes and downhole tools. Forward or backward whirl can lead to impact with the borehole, and stick slip and bit bounce can cause tool joint failure, twist-off, and bit damage. A complete deviated drillstring has been modelled by having decoupled axial and torsional segments for the vertical and curved portions, and nonlinear three-dimensional multibody segments with lateral vibration in the final horizontal section ending at the bit. The model can predict how axial and torsional bit-rock reactions are propagated to the surface, and the role that lateral vibration near the bit plays in exciting those vibrations and stressing components in the bottom-hole-assembly. The proposed model includes the mutual dependence of these vibrations, which arises due to bit-rock interaction and friction dynamics between the drillstring and wellbore wall.

Commentary by Dr. Valentin Fuster
2014;():V04AT04A060. doi:10.1115/IMECE2014-37407.

The friction experiments are conducted on a pin-on-disc friction material testing machine. The sliding velocity, pressure, temperature and friction coefficient are measured. The effects of brake temperature, brake pressure and braking speed on the friction coefficient are examined. Based on energy conservation theory, the model of friction coefficient is established using statistical methods. Then a semi-empirical model of friction coefficient is established by regression analysis methods. And the effects of the temperature, brake pressure, the relative sliding velocity and these cross-terms on the friction coefficient are also discussed.

Commentary by Dr. Valentin Fuster
2014;():V04AT04A061. doi:10.1115/IMECE2014-38263.

In the field of turbo machinery design frictional coupling has been found to be a low cost method to increase the mechanical damping of bladed disks. Underplatform dampers (UPD’s) are commonly used which are metal devices pressed against the blades by centrifugal forces. The main task is to find the optimum value of the contact normal force to maximize energy dissipation. This optimum strongly depends on the excitation of the structure. Traveling waves are excited by engine order excitation and flutter. Flutter caused by fluid structure interaction can be reduced by intentional mistuning of the bladed disk whereas forced response levels will be typically increased by mistuning. A compromise is alternate mistuning.

The present paper deals with the influence of alternate mistuning on frictional coupling of blisks. Firstly, the dynamics of a tuned blisk are explained with a simplified lumped mass cyclic oscillator model. It is pointed out that eigenfrequencies of traveling waves around the blisk are influenced by structural coupling. Alternate mistuning leads to mode coupling with the possibility of energy transfer. The performance of friction coupling strongly depends on the nodal diameter mode shape of vibration which is stated analytically for pure Coulomb sliding contact. Following this, a simplified blisk model with underplatform dampers is developed to analyze alternate mistuning and frictional coupling. The simulation results show a significant influence of the mistuning on the damping performance.

Commentary by Dr. Valentin Fuster
2014;():V04AT04A062. doi:10.1115/IMECE2014-38855.

The use of non-classical evolutionary optimization techniques such as genetic algorithms, differential evolution, swarm optimization and genetic programming to solve the inverse problem of parameter identification of dynamical systems leading to chaotic states has been gaining popularity in recent years. In this paper, three popular evolutionary algorithms — differential evolution, particle swarm optimization and the firefly algorithm are used for parameter identification of a clearance-coupled-impact oscillator system. The behavior of impacting systems is highly nonlinear exhibiting a myriad of harmonic, low order and high order sub-harmonic resonances, as well as chaotic vibrations. The time-history simulations of the single-degree-of-freedom impact oscillator were obtained by the Neumark-β numerical integration algorithm. The results are illustrated by bifurcation graphs, state space portraits and Poincare’ maps which gives valuable insights on the dynamics of the impact system. The parameter identification problem relates to finding one set of system parameters given a chaotic or periodic system response as a set of Poincaré points and a different but known set of system parameters. The three evolutionary algorithms are compared over a set of parameter identification problems. The algorithms are compared based on solution quality to evaluate the efficacy of using one algorithm over another.

Commentary by Dr. Valentin Fuster

Dynamics, Vibration, and Control: Fluid-Structure Interaction

2014;():V04AT04A063. doi:10.1115/IMECE2014-36060.

The fluid-structure interaction phenomenon, as manifested by the pressure pulsation excited by rotor-stator interaction, is the main cause of flow-induced vibrations at the blade passing frequency in large and high pressure centrifugal pumps. This phenomenon is strongly influenced by the clearance gap between impeller and volute diffusers/tongues and the geometry of impeller blade at exit. One way to reduce the effects of this interaction is to increase the effective gap by trimming the impeller. However, trimming the impeller will affect the pump performance and the flow pattern inside the pump volute. In the present work, experiments are carried out using a single stage, double-volute centrifugal model pump to investigate the effect of increasing the clearance gap by trimming the impeller on pump performance and vibration. Pressure fluctuations around the impeller inside pump volute are monitored and recorded. The clearance gap was increased three times by trimming the impeller radius by 1 mm, 2 mm, and 3 mm; respectively. Results showed that trimming the impeller reduces the pump vibration at the expense of the developed pump head. The minimum vibration was measured at the best efficiency point of the pump and the vibration amplitude increases when the pump operates at off-design conditions. Impeller trimming is more effective at flow rates equal to and higher that the design flow rate.

Commentary by Dr. Valentin Fuster
2014;():V04AT04A064. doi:10.1115/IMECE2014-36092.

In order to investigate the pressure fluctuation in a three-stage rotodynamic multiphase pump developed by authors, a bench test is set which choose the mixture of water and air as medium. Nine monitors are set in the pump including the inlet of each impeller, the interfaces of the rotor-stator and the middle section of each impeller. It turns out that the minimum pressure fluctuation is located in the interfaces of the rotor-stator in each stage and the maximum is in the interface of two stages. The domain frequency is the blade passing frequency of the impeller and its multipliers and there is no higher frequency. The coefficients of the pressure fluctuation is first decreased and then increased with the increase of the inlet gas volume fraction at the same rotational speed. But it increases with the increase of rotational speed at the same inlet gas volume fraction.

Topics: Pressure , Pumps
Commentary by Dr. Valentin Fuster
2014;():V04AT04A065. doi:10.1115/IMECE2014-36211.

Many 2D mechanical models have been developed to simulate liquid sloshing of a partially filled tank with different shapes. However, those models don’t represent properly the complex liquid motion, especially in the case of the portable tanks. Indeed, forces exerted on the fluid can be lateral, longitudinal and vertical. Then, liquid displacement and pressure forces applied to the tank walls are undervalued and can cause design flaws. In this case, 2D mechanical models are ineffective for the simulation of liquid motion properly. It this study a 3D equivalent mechanical model has been developed. This dynamical model is used to simulate different liquid motion in a partially filled tank that take into account any sort of excitement forces and get more accurate results in terms of displacements and pressure forces. Afterward, various tank forms and their compatibility with the 3D model are discussed, such as circular, modified oval and modified trapezoidal sections. Finally, equations of motion are developed for each tank shape.

Topics: Simulation
Commentary by Dr. Valentin Fuster
2014;():V04AT04A066. doi:10.1115/IMECE2014-36691.

In this paper, a newly developed nonlinear model is used to predict the dynamical behaviour and stability of a typical towed flexible cylinder. The numerical solutions are obtained via a time-integration method and also via the AUTO software. The effect of some system parameters on the local and overall stability and dynamics of the system is also investigated. Some experiments are then described which were designed to illustrate the dynamical behaviour of towed flexible cylinders and to test the theory. The experimental observations are generally in qualitative agreement with the nonlinear theory. Quantitative comparison of various quantities, e.g. the instability thresholds, between experiment and theory, based on the estimated values of some of the theoretical nondimensional parameters, is also fairly good.

Commentary by Dr. Valentin Fuster
2014;():V04AT04A067. doi:10.1115/IMECE2014-37271.

This study is aimed at analysis of transient lateral slosh in a partially-filled cylindrical tank with different designs of longitudinal partial baffles using a coupled multimodal and boundary-element method. A boundary element method is initially formulated to solve the eigenvalue problem of free liquid slosh, assuming inviscid, incompressible and irrotational flows. Significant improvement in computational time is achieved by reducing the generalized eigenvalue problem to a standard one involving only the velocity potentials on the half free-surface length using the zoning method. The generalized coordinates of the free-surface oscillations under a lateral excitation are then obtained from superposition of the natural slosh modes. The lateral slosh force is also formulated in terms of the generalized coordinates and hydrodynamic coefficients. The validity of the model is illustrated through comparisons with available analytical solutions. Two different designs of longitudinal baffles are considered: bottom- and top-mounted baffles. The effect of different baffle designs on the normalized slosh frequencies, modes and lateral force are investigated. It is shown that the multimodal method yields computationally efficient solutions of liquid slosh within moving baffled containers. The results suggest that the effectiveness of baffles in suppressing the liquid oscillations is strongly affected by the baffle length relative to the free-surface height. The top-mounted baffle yields the greatest effectiveness, when it pierces the free-surface. The bottom-mounted baffle, however, may not be considered as an efficient mean for controlling the liquid slosh in tank vehicles where the liquid fill height is above 50%.

Topics: Containers , Sloshing
Commentary by Dr. Valentin Fuster
2014;():V04AT04A068. doi:10.1115/IMECE2014-37283.

A theoretical approach is presented to study nonlinear vibrations of thin infinitely long rectangular plates subjected to pulsatile axial inviscid flow. The case of plates in axial uniform flow under the action of constant transmural pressure is also addressed for different flow velocities. The equations of motion are obtained based on the von Karman nonlinear plate theory retaining in-plane inertia via Lagrangian approach. The fluid model is based on potential flow theory and the Galerkin method is applied to determine the expression of the flow perturbation potential. The effect of different system parameters such as flow velocity, pulsation amplitude, pulsation frequency, and channel pressurization on the stability of the plate and its geometrically nonlinear response to pulsating flow are fully discussed. In case of zero uniform transmural pressure numerical results show hardening type behavior for the entire flow velocity range when the pulsation frequency is spanned in the neighbourhood of the plate’s fundamental frequency. Conversely, a softening type behavior is presented when a uniform transmural pressure is introduced.

Commentary by Dr. Valentin Fuster
2014;():V04AT04A069. doi:10.1115/IMECE2014-37948.

This paper is concerned with the active vibration control of a hanged rectangular plate partially submerged into a fluid by using piezoelectric sensors and actuators bonded to the plate. A dynamic model for the plate is derived by using the Rayleigh-Ritz method and the fluid effect is modeled by the virtual mass increase that is obtained by solving the Laplace equation. The natural vibration characteristics of the plate in air obtained theoretically are in good agreement with the experimental results. The changes in natural frequencies due to the presence of fluid were measured and compared to the theoretical predictions. Experimental results show that the theoretical predictions are in good agreement with the experimental results. The natural vibration characteristics of the plate both in air and in water are used for the active vibration control design. In this study, the multi-input and multi-output positive position feedback controller was designed based on the natural vibration characteristics and implemented by using a digital controller. Experimental results show that the vibration of the hanged rectangular plate both in air and partially submerged into a fluid can be successfully suppressed by using piezoelectric sensors and actuators.

Commentary by Dr. Valentin Fuster
2014;():V04AT04A070. doi:10.1115/IMECE2014-38076.

Pressure surges and fluid transients, such as steam and water hammer, are events that can occur unexpectedly in operating power plants causing significant damages. When these transients occur the power plant can be out of service for long time, until the root cause is found and the appropriate solution is implemented. In searching for root cause of transients, engineers must investigate in depth the fluid conditions in the pipe line and the mechanism that initiated the transients. The steam hammer normally occurs when one or more valves suddenly close or open. In a power plant, the steam hammer could be an inevitable phenomenon during turbine trip, since valves (e.g., main steam valves) must be closed very quickly to protect the turbine from further damage. When a valve suddenly stops at a very short time, the flow pressure builds up at the valve, starting to create pressure waves along the pipe runs which travel between elbows. Furthermore, these pressure waves may cause large dynamic response on the pipeline and large loads on the pipe restraints. The response and vibrations on the pipeline depend on the pressure waves amplitudes, frequencies, the natural frequencies and the dynamic characteristics of the pipeline itself. The piping flexibility or rigidity of the pipe line, determine how the pipes will respond to these waves and the magnitude of loads on the pipe supports. Consequently, the design of the piping system must consider the pipeline response to the steam hammer loads. In this paper, a design and analysis method is proposed to analyze the steam hammer in the critical hot lines due to the turbine trip using both PIPENET transient module and CAESAR II programs. The method offered in this paper aims to assist the design engineer in the power plant industry to perform dynamic analysis of the piping system considering the dynamic response of the system using the PIPENET and CAESAR II programs. Furthermore, the dynamic approach is validated with a static method by considering the appropriate dynamic load and transmissibility factors. A case study is analyzed for a typical hot reheat line in a power plant and the results of the transient analysis are validated using the theoretical static approach.

Commentary by Dr. Valentin Fuster
2014;():V04AT04A071. doi:10.1115/IMECE2014-38108.

Spreading of liquids on solid substrates is governed by mechanisms which induce contact line motion. Providing mechanical vibrations to the substrate is one such method which has proved effective in displacing the contact line. In the present work we experimentally explore the spreading characteristics of a liquid due to the substrate’s modal vibrations, in the frequency range of around 10kHz. The subsequent findings are then employed to subject the liquid to simultaneous low frequency actuations (in the 100Hz range) and substrate modal vibrations to produce a larger and a more evenly distributed spread about the substrate’s axis than that obtained with any of the two methods individually.

Topics: Vibration
Commentary by Dr. Valentin Fuster
2014;():V04AT04A072. doi:10.1115/IMECE2014-38260.

The speed at which a slung load can be carried under an aircraft is often limited by the onset of divergent oscillations. Simulations using highly-resolved airloads maps are described, in an effort to determine divergence speed. Airloads are obtained using the Continuous Rotation technique, which converts the discrete-attitude static airload measurements problem to a periodic problem amenable to closed-form analytical description. Free-swing tests of scaled models are performed in a wind tunnel with and without initial perturbations, to capture quantitative and qualitative records from encoders and from video, also capturing the likely modes that amplify. Results are presented for a cuboid and a porous box, the latter with and without one side closed. The roll divergence mechanism, the coupling of roll and yaw frequency, seen in swing tests is clearly observed in simulations run on the cuboid, both when yaw is forced and when the model is free.

Topics: Simulation , Stress
Commentary by Dr. Valentin Fuster
2014;():V04AT04A073. doi:10.1115/IMECE2014-38441.

Fluid-structure interaction (FSI) and unavoidable vibrations are important characteristics in the operation of hydropower structures and must be taken into account in the analysis and design of such equipment. Hydrodynamic damping influences the amplitude of vibrations and is directly related to fatigue problems in hydraulic machines which are of great importance. The aim of this study is to investigate the coupled effects of flowing fluid on a simplified hydrofoil by using three-dimensional two-way fluid-structure interaction modeling, in order to determine its importance in predicting vibration amplitudes and damping. The effect of considering different flow velocities is also investigated in the present study. The results of this research are compared with those obtained from experiments done by ANDRITZ [1]. The influences of mesh size and time step are also studied. Our results indicate that considering FSI in predicting the frequencies of the fluctuating fluid forces in practical problems might be ignored if the main concern of the analysis is to check the possibility of resonance. However, FSI must be included in the modeling when we aim to predict the influence of the fluid on the damping behavior in the hydrofoil vibration.

Commentary by Dr. Valentin Fuster
2014;():V04AT04A074. doi:10.1115/IMECE2014-38642.

An experiment study on the cross flow-induced vibration of a flexible cylinder with two degrees of freedom had been conducted in a towing tank. The test cylinder was a 45 cm long Tygon tubing with outer and inner diameter of 7.9 mm (5/16 in) and 4.8 mm (3/16 in), giving a mass ratio of 0.77 and an aspect ratio of 56. It was towed from rest up to 1.6 m/s before slowing down to rest again over a distance of 1.6 m in still water, covering the range of Reynolds number from 1500 to 13000 and reduced velocity from 4 to 35. Multi-mode vibration and sudden shift between different modes were observed. The vibration amplitude, frequency and mode were quantified. The results obtained during the brief constant towing speed were expressed in term of the corresponding Reynolds number or reduced velocity. These findings were cast with respect to the existing knowledge in the literature.

Commentary by Dr. Valentin Fuster
2014;():V04AT04A075. doi:10.1115/IMECE2014-38799.

Many challenging fluid-structure interaction problems in nuclear engineering remain unresolved because current CFD methodologies are unable to manage the number of computational cells needed and/or the difficulties associated with meshing changing geometries. One of the most promising recent methodologies for fluid dynamics modeling is the lattice-Boltzmann method — an approach that offers significant advantages over classical CFD methodologies by 1) greatly reducing meshing requirements, 2) offering great scalability, and 3) through relative ease of code parallelization. While LBM often requires increased numerical effort compared to other methods, this can be dramatically reduced by combining LBM with Adaptive Mesh Refinement (LB-AMR).

This study describes an ongoing collaboration investigating nuclear fuel-assembly spacer grid performance. The LB-AMR method, used to simulate the flow field around a specific spacer grid design, is capable of describing turbulent flows for high Reynolds numbers, revealing rich flow dynamics in good qualitative agreement with experimental results.

Prepared by LLNL under Contract DE-AC52-07NA27344.

Commentary by Dr. Valentin Fuster
2014;():V04AT04A076. doi:10.1115/IMECE2014-38937.

Nonlinear free vibration of a microstructure has been analyzed in this study. A fluid-conveying microtube is mathematically modeled using non-classical beam theory. Partial differential equation of the model is considered in non-dimensional form. Simply-supported boundaries are taken into account and assuming three vibrating modes, an analytical method is employed to obtain the nonlinear equations of motion. Variational iteration method has been utilized as an analytical solution technique. In order to obtain the nonlinear natural frequencies of the system, analytical expressions are found based on this method. A parametric study is also carried out to investigate the effect of different parameters on the vibration characteristics of the microstructure.

Commentary by Dr. Valentin Fuster
2014;():V04AT04A077. doi:10.1115/IMECE2014-38954.

The interaction between fuel assemblies during a seismic or loss of coolant accident (LOCA) event is directly associated with safety and reliability issues for all types of nuclear reactors. This study concentrates on the modeling of a single fuel assembly represented by a cylinder subjected to external flow and an external forcing function at the base. The model investigates the response of the fuel assembly using continuum mechanics model. The general behavior of a cylinder supported at both ends and subjected to axial flow is summarized: The cylinder undergoes several flow-induced instabilities as the flow velocity increases. These instabilities start with a pitchfork bifurcation, resulting in the buckling of the cylinder. At higher flow velocities, period-doubling and torus instabilities are observed as well, eventually leading to chaotic oscillations of the cylinder. It is shown that an increased confinement results in lower critical flow velocities for the first point of instability, resulting in buckling at lower flow velocities. The cylinder response to a base excitation is also considered and it is shown that the response amplitude can change depending on the frequency of base excitation.

Commentary by Dr. Valentin Fuster
2014;():V04AT04A078. doi:10.1115/IMECE2014-38997.

A Hybrid friction model has recently been developed by Azizian and Mureithi [1] to simulate the general friction behavior between surfaces in contact. However, identification of the model parameters remains an unresolved problem.

To identify the parameters of the friction model, the following quantities are required: contact forces (friction and impact forces), the slip velocity and displacement in the contact region. Direct measurement of these quantities is difficult. In the present work, a beam clamped at one end and simply supported with the consideration of friction effect at the other is used as a mechanical amplifier of the friction effects at the microscopic level. Using this simplified approach, the contact forces, the sliding velocity and the displacement can be indirectly obtained by measuring the beam vibration response. A new method based on nonlinear modal analysis to calculate the contact forces is developed in the present work. The method is based on the modal superposition principle and Fourier series expansion.

For the harmonic balance method, two approaches were tested. The approach based on sub-harmonic forms gave the best results.

Signal reconstruction made it possible to accurately identify the parameters of the hybrid friction model with a multiple step approach.

Topics: Friction
Commentary by Dr. Valentin Fuster
2014;():V04AT04A079. doi:10.1115/IMECE2014-39234.

In-plane instability of tube arrays has not been a major concern to steam generator designers until recently following observations of streamwise tube failure in a nuclear power plant in U.S.A. However, modeling of fluidelastic instability in two-phase flows still remains a challenge.

In the present work, detailed steady fluid force measurements for a kernel of an array of tubes in a rotated triangular tube array of P/D=1.5 subjected to air-water two-phase flows for a series of void fractions and a Reynolds number (based on the pitch velocity), Re = 7.2 × 104 has been conducted. The measured steady fluid force coefficients and their derivatives, with respect to streamwise static displacements of the central tube, are employed in the quasi-steady model [1, 2], originally developed for single phase flows, to analyze in-plane fluidelastic instability of multiple flexible arrays in two-phase flows. The results are consistent with dynamic stability tests [3].

Commentary by Dr. Valentin Fuster
2014;():V04AT04A080. doi:10.1115/IMECE2014-40200.

A joint experimental and numerical campaign is conducted to provide validation datasets for high-fidelity fluid-structure interaction models of nuclear fuel assemblies during seismic loading. A refractive index matched flow loop is operated on a six-degree-of-freedom shake table and instrumented with non-intrusive optical diagnostics. The test section can house up to three full height fuel assemblies. To guarantee reproducible and controlled initial conditions, special care is given to the test section inlet plenum; in particular it is designed to minimize secondary pulsatile flow that may arise due to ground acceleration. A single transparent surrogate 6×6 fuel subassembly is used near prototypical Reynolds number, Re = 105 based on hydraulic diameter. To preserve dynamic similarity of the model with prototype, the main dimensionless parameters are matched and custom spacer grids are designed. Special instruments are developed to characterize fluid and structure response and to operate in this challenging shaking environment. In parallel to the above experiments we also conducted fully coupled large-eddy simulations, where the equations for the fluid and the structure are simultaneously advanced in time using a partitioned scheme. To deal with the highly complex geometrical configuration, which also involves large displacements and deformations we utilize a second order accurate, immersed boundary formulation, where the geometry is immersed in a block-structured grid with adaptive mesh refinement. To explore a wide parametric range we will consider several subsets of the experimental configuration. A typical computation involves 60K cores, on leadership high performance computing facilities (i.e. IBM Blue-Gene Q – MIRA).

Commentary by Dr. Valentin Fuster

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