bluuebunny/crossref_metadata_2025 huggingface dataset:
Distributed Link-Layer Control for Automated Highway Systems
Authors: Peng Huei
Published: February 2008

The modeling and design of a link-layer control algorithm for automated highway systems are presented in this paper. Link-layer control systems address the coordination of traffic on a stretch of highway, and serve as the intermediate layer between traffic management (ATMS) and vehicle control (AVCS) systems. The key role of the link layer control system is to use macroscopic traffic information for improved traffic flow. A distributed control algorithm is developed based on optimal control theory. The proposed control law is implemented in a simulation program which keeps track of the motions of each individual vehicles on the highway. Simulation results under three perturbed conditions—uneven traffic distribution, broken vehicle, and traffic merging—are presented.
Time-Optimal Negative Input Shapers
Authors: Singhose W. E. , Seering W. P. , Singer Neil C.
Published: February 2008

Input shaping reduces residual vibration in computer controlled machines by convolving a sequence of impulses with a desired system command. The resulting shaped input is then used to drive the system. The impulse sequence has traditionally contained only positively valued impulses. However, when the impulses are allowed to have negative amplitudes, the rise time can be improved. Unfortunately, excitation of unmodeled high modes and overcurrenting of the actuators may accompany the improved rise time. Solutions to the problem of high-mode excitation and overcurrenting are presented. Furthermore, a simple look-up method is presented that facilitates the design of negative input shapers. The performance of negative shapers is evaluated experimentally on two systems; one driven by a piezo actuator and the other equipped with DC motors.
Land Vehicle Roll/Yaw Product of Inertia Measurement
Authors: Durisek N. J. , Heydinger G. J. , Chrstos J. P. , Guenther D. A.
Published: February 2008

This paper focuses on the measurement of the roll/yaw product of inertia of a vehicle and describes a four-degree-of-freedom lumped-parameter ADAMS model used to simulate the test configuration. The measurement is performed by oscillating the vehicle in yaw and monitoring the resulting yaw acceleration and roll torque. The product of inertia is calculated from equations representing the motion of a rigid body relative to a nonmoving reference frame modified to accommodate for the misalignment of the vehicle center of gravity and the test apparatus yaw axis, and to approximate the compliant behavior between the test device and vehicle. The effects of the vehicle center of gravity misalignment from the test apparatus’ yaw axis and the compliance between the test vehicle and test device are studied. The measurement uncertainty is found using the law of propagation of uncertainty.
A Non-Normality Measure of the Condition Number for Monitoring and Control
Authors: Huh Kunsoo , Stein Jeffrey L.
Published: February 2008

Because the behavior of the condition number can have highly steep and multi-modal structure, optimal control and monitoring problems based on the condition number cannot be easily solved. In this paper, a minimization problem is formulated for κ2(P), the condition number of an eigensystem (P) of a matrix in terms of the L2 norm. A new non-normality measure is shown to exist that guarantees small values for the condition number. In addition, this measure can be minimized by proper selection of controller and observer gains. Application to the design of well-conditioned controller and observer-based monitors is illustrated.
The Shape From Motion Approach to Rapid and Precise Force/Torque Sensor Calibration
Authors: Voyles R. M. , Morrow J. D. , Khosla P. K.
Published: February 2008

We present a new technique for multi-axis force/torque sensor calibration called shape from motion. The novel aspect of this technique is that it does not require explicit knowledge of the redundant applied load vectors, yet it retains the noise rejection of a highly redundant data set and the rigor of least squares. The result is a much faster, slightly more accurate calibration procedure. A constant-magnitude force (produced by a mass in a gravity field) is randomly moved through the sensing space while raw data is continuously gathered. Using only the raw sensor signals, the motion of the force vector (the “motion”) and the calibration matrix (the “shape”) are simultaneously extracted by singular value decomposition. We have applied this technique to several types of force/torque sensors and present experimental results for a 2-DOF fingertip and a 6-DOF wrist sensor with comparisons to the standard least squares approach.
Cross Calibration by FFT Equalization
Authors: Peleg K.
Published: February 2008

The classical calibration problem is primarily concerned with comparing an approximate measurement method with a very precise one. Frequently, both measurement methods are very noisy, so we cannot regard either method as giving the true value of the quantity being measured. Sometimes, it is desired to replace a destructive or slow measurement method, by a noninvasive, faster or less expensive one. The simplest solution is to cross calibrate one measurement method in terms of the other. The common practice is to use regression models, as cross calibration formulas. However, such models do not attempt to discriminate between the clutter and the true functional relationship between the cross calibrated measurement methods. A new approach is proposed, based on minimizing the sum of squares of the differences between the absolute values of the Fast Fourier Transform (FFT) series, derived from the readings of the cross calibrated measurement methods. The line taken is illustrated by cross calibration examples of simulated linear and nonlinear measurement systems, with various levels of additive noise, wherein the new method is compared to the classical regression techniques. It is shown, that the new method can discover better the true functional relationship between two measurement systems, which is occluded by the noise.
System Dynamics Modeling of Porous Media
Authors: Fahrenthold E. P. , Venkataraman M.
Published: February 2008

A wide range of engineering problems involve porous media modeling. General porous media models are highly nonlinear, geometrically complex, and must account for energy transfer between fluid and solid constituents normally modeled in distinct Lagrangian and Eulerian reference frames. Combining finite element discretization techniques with bond graph methods greatly simplifies the model formulation process, as compared to alternative schemes based on weighted residual solutions of the governing partial differential equations. The result generalizes existing numerical models of porous media and current network thermodynamics/bond graph theory.
Stable Optimal Model Reduction of Linear Discrete-Time Systems
Authors: Puri N. N. , Lim M. T.
Published: February 2008

A new algorithm is presented for finding reduced-order models of the linear time-invariant systems. Proposed recursive algorithm minimizes a weighted mean squared impulse (or step) response error between the original system and the reduced order model. This proposed optimization algorithm require solving very easy linear equations rather than the usual complicated non-linear equations. The procedure guarantees a reduced order stable model at each recursive stage. Method is easily extended to multi-input/multi-output systems. Algorithm’s performance is compared with other methods reported in the literature.
Robust Decentralized Stabilization of Large-Scale Delay Systems Via Sliding Mode Control
Authors: Yan Jun-Juh , Tsai Jason Sheng-Hong , Kung Fan-Chu
Published: February 2008

The present paper is concerned with the decentralized stabilization problem of large-scale systems with delays in the intercon-nections using sliding mode control. A robust stability condition of the sliding mode and a robust decentralized sliding mode controller are newly derived for large-scale delay systems. Also a proportional-integral sliding mode is designed to make it easy to assure the stability of dynamics in the sliding mode.
Fuzzy Neural Network Control for DC-Motor Micromaneuvering
Authors: Tzes Anthony , Peng Pei-Yuan
Published: February 2008

The application of a fuzzy neural network controller for compensating the effects induced by the friction in a DC-motor micromaneuvering system is considered in this article. A back-propagation neural network is employed to decrease the effects of the system nonlinearities. The input vector to the neural network controller consists of the time history of the motor angular shaft velocity within a prespecified time window. A fuzzy cell space controller supervises the overall scheme and reduces the amplitude and repetitions of control switchings. Simulation studies are presented to indicate the effectiveness of the proposed algorithm.
Vibration Reduction Using Multi-Hump Input Shapers
Authors: Singhose W. E. , Porter L. J. , Tuttle T. D. , Singer N. C.
Published: February 2008

Input shaping is a method for reducing residual vibrations in computer-controlled machines. Vibration is eliminated by convolving an input shaper, which is a sequence of impulses, with a desired system command to produce a shaped input. The shaped input then becomes the command to the system. Requiring the vibration reduction to be robust to modeling errors and system nonlinearities is critical to the success of the shaping process on any real system, Input shapers can be made very insensitive to parameter uncertainty; however, increasing robustness usually increases system delays. A design process is presented that generates input shapers with insensitivity-to-time-delay ratios that are much larger than traditionally designed input shapers. The advantages of the new shapers are demonstrated with computer simulations and their performance is verified with experimental results from the MIT Middeck Active Control Experiment, which was performed on board the Space Shuttle Endeavor.
Vibration Controllability of 3D Flexible Manipulators
Authors: Lo´pez-Linares S. , Konno A. , Uchiyama M.
Published: February 2008

Structural vibrations of flexible robots are not always fully controllable in all the workspace. In some cases, there exist configurations where the actuators cannot affect some of the vibration modes, and thus cannot control their vibrations. This problem has been neglected in the case of the one-link and two-link planar manipulators; however, it must be dealt with in depth when trying to control a 3D flexible robot. This paper discusses the vibration controllability of flexible manipulators. Vibration uncontrollable configurations are estimated both by the minimum singular values of the controllability matrix and the closed-loop behavior. A 2-link 3-joint prototype flexible manipulator is used for a case study, and the uncontrollable configurations of the manipulator are found.
Position Control of Single Link Flexible Manipulator by Variable Structure Model Following Control
Authors: Thomas S. , Bandyopadhyay B.
Published: February 2008

A variable structure model following controller (VSMFC) is designed for the tip position control of a single flexible link. The design is done for the system model in which only the first two flexible modes are included. Due to the simplicity in choosing second order models for the subsystems representing the dynamics of the various flexible modes, the design can be easily extended to include any desired number of flexible modes. The tip position response is made to assume a second order step response by suppressing the flexible modes very quickly. Hence the tip position response can be easily controlled by a suitable choice of the damping factor and natural frequency of the second order model which the rigid body mode of the link is made to follow. The controller is robust to parameter variations and disturbances.
A Neural Network Approach to Electromyographic Signal Processing for a Motor Control Task
Authors: Lester W. T. , Gonzalez R. V. , Fernandez B. , Barr R. E.
Published: February 2008

A hybrid modeling structure composed of a one degree of freedom computational musculo-skeletal model and a multilayer perceptron neural network was used to effectively map electromyography (EMG) from a human exercise trial to muscle activations in a physiologically feasible and accurate fashion. Several configurations of the complete hybrid system were used to map four muscle surface EMGs from a ballistic elbow flexion to normalized muscle activations, estimated individual muscle forces and torque about the joint. The net joint torque was used to train the neural portion of the hybrid system to minimize kinematic error. The model allowed the estimation of the nonobservable parameters: normalized muscle activations and forces which was used to penalize the learning system. With these parameters in the learning equation, our system produced muscle activations consistent with the classic triphasic response present in ballistic movements.
Robust Filtering for Interconnected Uncertain Systems Under Sampled Measurements
Authors: Shi Peng , Wang Youyi , Xie Lihua
Published: February 2008

This paper presents the results of robust filtering for a class of interconnected uncertain systems under sampled measurements. We address the problem of designing filters, using sampled measurements, which would guarantee a prescribed H∞ performance in the continuous-time context, irrespective of the parameter uncertainty and unknown initial states. Both the cases of finite and infinite horizon filtering are investigated in terms of N pairs of Riccati equations with finite discrete jumps.
On the Inverse Kinematics of Space Manipulators for Avoiding Dynamic Singularities
Authors: Xi F. , Fenton R. G.
Published: February 2008

A spacecraft-manipulator system is considered in this paper. Dynamic singularities are the singularities occurring when inverting the system generalized Jacobian required by the conventional method for solving the inverse kinematics of space manipulators. To avoid dynamic singularities, three methods are developed here based on the manipulator Jacobian, instead of the system generalized Jacobian. These methods are compared with the conventional method on the basis of their convergence rates, accuracies and sensitivities. Results of this comparison are presented in this paper.
Dynamical Characteristics of Gyroscopic Weight Measuring Device
Authors: Kurosu Shigeru , Adachi Motoyuki , Kamimura Kazuyuki
Published: February 2008

This paper describes analytical and experimental studies about an entirely new system for measuring forces using a gyroscope(called Gyroscopic Weight Measuring Device, or simply “GWMD” throughout this paper) which provides precise direct digital output proportional to the single axis weight applied. In spite of the complexity of the servo-mechanism, the action of the GWMD is inherently linear, hysteresis, and drift free. Topics in this paper are summarized as follows: 1) The principal dynamical characteristics of the GWMD using a two-degree-of-freedom mathematical model for a gyroscope are analyzed theoretically. 2) The GWMD is designed with suitable parameters and constructed. Some systematic errors caused by various influences are examined. 3) Performance tests are promising for practical applications. The GWMD constructed in this study offers a repeatable accuracy up to 1/15,000 for weight in the range 0 to 150 N.
A Robust Controller for Second-Order Systems Using Acceleration Measurements
Authors: Chuang C.-H. , Courouge Oliver , Juang Jer-Nan
Published: February 2008

This paper presents a robust control design using strictly positive realness for second-order dynamic systems. A robust strictly positive real controller stabilizes second-order systems with only acceleration measurements. An important property of this design is that the stabilization is independent of the system plant parameters. The control design connects a virtual system to a given plant such that any strictly positive real controller can be used to achieve robust stability. A spring-mass system is used as an example to demonstrate the robust stability and robust performance of this design.
Accounting for Out-of-Bandwidth Modes in the Assumed Modes Approach: Implications on Colocated Output Feedback Control
Authors: Clark R. L.
Published: February 2008

Colocated, output feedback is commonly used in the control of reverberant systems. More often than not, the system to be controlled displays high modal density at a moderate frequency, and thus the compliance of the out-of-bandwidth modes significantly influences the performance of the closed-loop system at low frequencies. In the assumed modes approach, the inclusion principle is used to demonstrate that the poles of the dynamic system converge from above when additional admissible functions are used to expand the solution. However, one can also interpret the convergence of the poles in terms of the zeros of the open-loop system. Since colocated inputs and outputs are known to have interlaced poles and zeros, the effect of a modification to the structural impedance locally serves to couple the modes of the system through feedback. The poles of the modified system follow loci defined by the relative location of the open-loop poles and zeros. Thus, as the number of admissible functions used in the series expansion is increased, the interlaced zeros of the colocated plant tend toward the open-loop poles, causing the closed-loop poles to converge from above as predicted by the inclusion principle. The analysis and results presented in this work indicate that the cumulative compliance of the out-of-bandwidth modes and not the modes themselves is required to converge the zeros of the open-loop system and the poles of the closed-loop system.
Nonlinear Inverse and Predictive End Point Trajectory Control of Flexible Macro-Micro Manipulators
Authors: Yim Woosoon , Singh Sahjendra N.
Published: February 2008

This paper presents a new approach to end-point trajectory control of flexible macro-micro manipulator based on nonlinear inversion and predictive control techniques. In this approach, precise control of the end-effector trajectory is accomplished by the inverse controller of the rigid micro manipulator, and the predictive controller steers the end point of the flexible macro manipulator with limited elastic oscillation. The predictive control law is obtained by minimizing a quadratic function of the tip tracking error, the elastic deflection, and the input torque of the flexible macro manipulator. The feedback parameters of the predictive controller are chosen such that zero dynamics are asymptotically stable. The combination of the inverse and the predictive controllers accomplishes precise end-effector trajectory tracking and elastic mode stabilization. These results are applied to a planar macro-micro manipulator system consisting of one flexible link and two micro rigid links. Simulation results are presented to show that in the closed-loop system time varying end point trajectory control and elastic mode stabilization are accomplished.
On the Tracking Control of Differentially Steered Wheeled Mobile Robots
Authors: Zhang Y. L , Velinsky S. A. , Feng X.
Published: February 2008

Fundamental tracking control algorithms of a differentially steered wheeled mobile robot with two conventional driven wheels are studied through analyzing the robot’s inherent kinematics. This includes the tracking variable assignment as well as the tracking singularity and position-orientation tracking decoupling problems. Globally convergent tracking control algorithms are proposed, which can exactly track any differentiable reference path. A fundamental motion orientation equation under the condition of exact position tracking is developed, and it is shown that it is not possible to exactly track both position and orientation concurrently for this kind of mobile robot configuration if the tracking point is not on the baseline. Examples are provided illustrating the tracking ability of the developed control algorithms.
The Effective Fluid Bulk-Modulus Within a Hydrostatic Transmission
Authors: Manring N. D.
Published: February 2008

In this study, the fluid bulk-modulus within a hydrostatic transmission is examined. Specifically, a method for measuring the effective fluid bulk-modulus is proposed based upon the definition of the fluid bulk-modulus and the conservation of mass within the system. Using the measured parameters of flow and pressure, a numerical solution for the effective fluid bulk-modulus is carried out and a closed-form approximation to this solution is presented. Furthermore, the accuracy expectations of this method are discussed and compared with traditional methods of estimating the fluid bulk-modulus and it is shown that significant improvements can be made when the method of this research is employed.
Accelerometer Placement for Angular Velocity Determination
Authors: Genin Joseph , Hong Juehui , Xu Wei
Published: February 2008

An accelerometer placement scheme to determine the angular velocities and accelerations of a rigid body is presented. We show that the least number of uniaxial accelerometers required in a sensor array to uniquely determine the angular velocities in a moving frame is nine.
Stability of PDF Controller With Stick-Slip Friction Device
Authors: Yen Jia-Yush , Huang Chih-Jung , Lu Shu-Shung
Published: February 2008

This paper presents the precision control of drive devices with significant stick-slip friction. The controller design follows the Pseudo-Derivative Feedback (PDF) control algorithm. Using the second order system model, the PDF controller offers arbitrary pole placement. In this paper, the stability proof for the controller with stick-slip friction is presented. On the basis of this proof, the stability criteria are derived. The paper also includes both the computer simulation and the experimental works to confirm the theoretical result. The experiments conducted on a Traction Type Drive Device (TTDD) shows that control accuracy of as high as ±1 arc – second is achieved.
Discrete-Time Sliding Mode Control for Nonlinear Systems With Unmatched Uncertainties and Uncertain Control Vector
Authors: Misawa E. A.
Published: February 2008

This paper presents a technique for control system design that provides robust stability in the presence of bounded modeling errors. The proposed method is a discrete-time version of a well known sliding mode control technique with saturation functions that generates the boundary layer without requiring either matched uncertainties or smooth functions. It is shown that the boundary layer can be made attractive and that the boundary layer thickness is bounded under mild coditions. It is also shown that asymptotic stability can be guaranteed if the available model is assumed to be perfect. An example is used to illustrate the proposed design technique.
Control of Linear Time-Varying Systems Using Forward Riccati Equation
Authors: Chen Min-Shin , Kao Chung-yao
Published: February 2008

This paper presents a new state feedback control design for linear time-varying systems. In conventional control designs such as the LQ optimal control, the state feedback gain is calculated off-line by solving a Differential Riccati Equation (DRE) backwards with the boundary condition set at some future time. The apparent disad-vantage of using a backward DRE is that future information of the system matrices is required to find the state feedback gain at every time instant. In this paper, an inversion state transformation is applied to the system so that the DRE associated with the transformed system becomes forward in the sense that its boundary condition is set at the initial time of operation (t = t0). As a result, the forward DRE can be calculated on-line without using future information of the system matrices.
H ∞ Optimal Repetitive Controller Design for Stable Plants
Authors: Peery T. E. , O¨zbay H.
Published: February 2008

The repetitive controller design problem is studied for stable plants in the framework of the H∞ optimal control. For a given nominal repetitive controller, first stability robustness is optimized by solving a finite dimensional H∞ control problem. Then the nominal design is modified in an optimal way so that the performance is improved while keeping the robustness level approximately the same. This problem is formulated as a two block H∞ problem involving a delay system and two weighting functions. The resulting controller can be implemented by adding a few blocks to the existing nominal design. An example is given to illustrate the numerical aspects of this approach.
Uniform Damping and Stiffness Control of Structures With Distributed Actuators
Authors: Washington G. N. , Silverberg L.
Published: February 2008

The research in this paper introduces an algorithm for uniformly damping and stiffening structures using distributed actuators. Inherent in this algorithm is the ability to eliminate structural biases, which can cause steady state error. The method involves the utilization of modal techniques to calculate the proportional, integral, and derivative gains in a feedback control law. The gains are calculated by first converting the system into the modal domain, second by employing the principles of uniform damping and stiffening to the system in the modal domain, and finally by converting that system back into the physical domain. The beauty of this technique lies in the fact that even though the principles of modal control are used in gain setting, no modal information is needed in the fined control law. The theory is validated by simulations and is illustrated in an example. Since a modal approach and distributed actuation is utilized, the benefit to active control and adaptive structures is discussed.
Continuous Sliding Mode Control of a Pneumatic Actuator
Authors: Surgenor B. W. , Vaughan N. D.
Published: February 2008

Sliding mode control has been promoted as a means to overcome the nonlinearities associated with pneumatic positioning systems. Previously published performance results have been disappointing with reported accuracies of only ±5 mm and poor tracking of the sliding surface. New experimental results demonstrate that a properly designed continuous sliding mode controller (CSLM) is capable of accuracies of better than ±0.2 mm. Further, the CSLM controller is able to maintain performance when the load mass is varied by upwards of a factor of 10. Direct comparison to a conventional pro-portional differential pressure controller provides evidence that CSLM is indeed more robust than comparable controllers for this application.
On the Linear Quadratic Optimal Systems Design in the Frequency Domain
Authors: Lin Chih-Min , Lu Tarn-Sea
Published: February 2008

By frequency-domain approach, a synthesis methodology of single-input-single-output optimal control system is developed to ensure closed-loop stability and to minimize a linear quadratic cost function. Furthermore, the equivalent two-degree-of-freedom system is designed so that the feedback-loop can satisfy the return difference equality, i.e., this system possesses the system performance with the optimal control sense and the stability margins properties as in time-domain approach LQR optimal systems. The F-4E flight control system is considered as the design example to illustrate the validity of the design method.
Sliding Mode Control With Perturbation Estimation (SMCPE) and Frequency Shaped Sliding Surfaces
Authors: Moura Jairo T. , Ghosh Roy Rajiv , Olgac Nejat
Published: February 2008

Sliding Mode Control with Perturbation Estimation (SMCPE) is a recent control routine which steers uncertain dynamic systems with disturbances to follow a desired trajectory. It eliminates the conventional requirement for the knowledge of uncertainty upper bound. A perturbation estimation scheme provides a tool for robustness. This text offers an additional robustizing mechanism: selection of time-varying sliding functions utilizing frequency shaping techniques. Frequency shaping together with sliding mode control introduces a behavior for selectively penalizing tracking errors at certain frequency ranges. This combination provides two advantages concurrently: (a) It filters out certain frequency components of the perturbations therefore eliminating the possible excitation on the unmodelled dynamics, and (b) it drives the state to the desired trajectory despite perturbations. The crucial point is that a priori knowledge of the perturbation upper bound is not necessary to eliminate the perturbation effects at the designated frequencies. Numerical examples prove the effectiveness of this novel scheme.
Use of Convex Hulls for Plant Template Approximation in QFT Design
Authors: Lasky T. A. , Ravani B.
Published: February 2008

A method is presented for the rapid approximation of plant templates for the Quantitative Feedback Theory (QFT) control design methodology. The approach is based on the convex hull of the template, and works for a wide variety of system uncertainty. The method presented will work for systems in which the model is not affine in the uncertain parameters. It represents an algorithmic implementation of a critical step in the QFT design methodology.
A Study of Fuzzy-Neural Force Control for a Quadrupedal Walking Machine
Authors: Tsai Chau-Ren , Lee Tsu-Tian
Published: February 2008

In this paper, the inverse kinematics and the foot force distributions of a planetary gear type quadrupedal walking machine are analyzed. This walking machine has four legs and each leg has three-degrees-of-freedom. The whole system has a total of seventeen links. The planetary gear leg is designed for a quadruped which can walk and trot under the following design criteria: high efficiency, compact size, and high payload/weight ratio. A neural network structure fuzzy logic controller is applied to control the foot force distribution of the quadruped walking machine. The performance of this fuzzy logic control algorithm is evaluated. Experimental results show that the fuzzy logic controller is effective in controlling this walking machine.
Bifurcations and Chaos in a PD-Controlled Pendulum
Authors: Alvarez Joaqui´n , Verduzco Fernando
Published: February 2008

The complex dynamics of a pendulum controlled by a Proportional-Derivative (PD) compensator are analyzed. A classification of equilibrium points and the characterization of their bifurcations is also presented. It is shown that the controlled pendulum may exhibit a chaotic behavior when the desired position is periodic and the proportional gain and total dissipation are small enough.
K-Fold Exosystem and the Robust Nonlinear Servomechanism Problem
Authors: Huang Jie
Published: February 2008

Asymptotic tracking and disturbance rejection in uncertain nonlinear systems is studied in the context of output feedback control. This study is facilitated by formalizing the notion of k-fold exosystem and generalizing the internal model principle to the nonlinear setting.
Mapping a Space Manipulator to a Dynamically Equivalent Manipulator
Authors: Liang Bin , Xu Yangsheng , Bergerman Marcel
Published: February 2008

In this paper, we discuss the problem of how a free-floating space manipulator can be mapped to a conventional, fixed-base manipulator which preserves both its dynamic and kinematic properties. This manipulator is called Dynamically Equivalent Manipulator (DEM). The DEM concept not only allows us to model a free-floating space manipulator system with simple, well-understood methods, but also to build a conventional manipulator system to experimentally study the dynamic performance and task execution of a space manipulator system, without having to resort to complicated experimental set-ups to simulate the space environment. This paper presents the theoretical development of the DEM concept, demonstrates the dynamic and kinematic equivalence, and presents simulation results to illustrate the equivalence under open-loop and closed-loop control strategies.
Emergency Lane-Change Maneuvers of Autonomous Vehicles
Authors: Shiller Zvi , Sundar Satish
Published: February 2008

This paper addresses the issue of collision avoidance using lane-change maneuvers. Of particular interest is to determine the minimum distance beyond which an obstacle cannot be avoided at a given initial speed. Using a planar bicycle model, we first compute the sharpest dynamically feasible maneuver by minimizing the longitudinal distance of a lane transition, assuming given initial and free final speeds. The minimum distance to an obstacle is then determined from the path traced by the optimal maneuver. Plotting the minimum distance in the phase plane establishes the clearance curve, a valuable tool for planning emergency maneuvers. For the bicycle model, the clearance curve is shown to closely correlate with the straight line produced by a point mass model. Examples demonstrate the use of the clearance curve for planning safe avoidance maneuvers.
Modeling and Designing a Hydrostatic Transmission With a Fixed-Displacement Motor
Authors: Manring N. D. , Luecke G. R.
Published: February 2008

This study develops the dynamic equations that describe the behavior of a hydrostatic transmission utilizing a variable-displacement axial-piston pump with a fixed-displacement motor. In general, the system is noted to be a third-order system with dynamic contributions from the motor, the pressurized hose, and the pump. Using the Routh-Hurwitz criterion, the stability range of this linearized system is presented. Furthermore, a reasonable control-gain is discussed followed by comments regarding the dynamic response of the system as a whole. In particular, the varying of several parameters is shown to have distinct effects on the system rise-time, settling time, and maximum percent-overshoot.
Modeling and Identification of Elastomeric Bearing Characteristics for Large-Scale Simulations
Authors: Morman K. N. , Nikolaidis E. , Rakowska J. , Seth S.
Published: February 2008

A constitutive equation of the differential type is introduced to model the nonlinear viscoelastic response behavior of elastomeric bearings in large-scale system simulations for vibration assessment and component loads prediction. The model accounts for the nonlinear dependence of dynamic stiffness and damping on vibration amplitude commonly observed in the behavior of bearings made of particle-reinforced elastomers. A testing procedure for the identification of the model parameters from bearing component test data is described. The experimental and analytical results for predicting the behavior of four (4) different car bushings are presented. In an example application, the model is incorporated in an ADAMS simulation to study the dynamic behavior of a car rear suspension.
The Dynamics of Clattering I: Equation of Motion and Examples
Authors: Goyal S. , Papadopoulos J. M. , Sullivan P. A.
Published: February 2008

The “clattering” motion that results when flat objects, like portable electronic products, strike the ground at an angle, is introduced and studied. During clattering one corner of the product touches down first, then successive corners strike one or more times, before it either bounces clear, or comes to rest on the floor. (This stands in distinct contrast to standard fragility tests which involve a single impact and no rotation.) The problem is formalized through the small-angle clattering of a unidimensional “bar” which contacts the ground only at its ends. Its equation of motion is constructed via transition matrices that govern the jumps in endpoint velocities from each collision. It is shown that the number and severity of the individual impacts experienced by the bar is highly variable, depending on mass distribution and coefficient of restitution. For several choices of these parameters, graphical results are presented for quantities that bear on shock-damage, such as: the total number of impacts, sequence of linear and angular velocity jumps, total time before clattering ends, total energy loss, peak linear impulse, etc. In particular, it is illustrated that parts of the bar can undergo a rapid sequence of “amplified” velocity reversals. A companion paper (Goyal et al., 1998b) outlines some global results, and practical implications for shock protection.
On the Properties of a Dynamic Model of Flexible Robot Manipulators
Authors: Arteaga Marco A.
Published: February 2008

Control design of flexible robot manipulators can take advantage of the structural properties of the model used to describe the robot dynamics. Many of these properties are physical characteristics of mechanical systems whereas others arise from the method employed to model the flexible manipulator. In this paper, the modeling of flexible-link robot manipulators on the basis of the Lagrange’s equations of motion combined with the assumed modes method is briefly discussed. Several notable properties of the dynamic model are presented and their impact on control design is underlined.
3 1/2 DOF Polynomial Solution of the Inferential H2/H∞ Control Problem With Application to Metal Rolling
Authors: Grimble M. J.
Published: February 2008

The solution of a new inferential 3 1/2-degree-of-freedom stochastic optimal control problem is discussed which may be either H2 or H∞ optimal. The system includes a 2 1/2-degree-of-freedom inferential tracking controller and a feedforward control action. The feedback controller must be robust and is therefore normally designed to minimize an H∞, criterion. However, the solution obtained is sufficiently general that the feedback, tracking or feedforward control functions can be chosen to minimize either an H2 or a H∞ criterion. The inferential control problem considered was motivated by a problem in the control of metal strip rolling mills. The design study presented considers the control of strip thickness given stand force measurements, and the use of feedforward signal from an upstream stand.
Experimental and Theoretical Results in Output-Trajectory Redesign for Flexible Structures
Authors: Dewey J. S. , Leang K. , Devasia S.
Published: February 2008

In this paper we study the optimal redesign of output trajectories for linear invertible systems. This is particularly important for tracking control of flexible structures because the input-state trajectories, that achieve tracking of the required output, may cause excessive vibrations in the structure. Therefore, a trade-off is required between tracking and vibration reduction. We pose and solve this problem, in the context of linear systems, as the minimization of a quadratic cost function. The theory is developed and applied to the output tracking of a flexible structure and experimental results are presented.
Applications of Adaptive Controllers to Systems With Nonlinear Parametrization
Authors: Annaswamy A. M. , Thanomsat C. , Mehta N. , Loh Ai-Poh
Published: February 2008

Nonlinear parametrizations occur in dynamic models of several complex engineering problems. The theory of adaptive estimation and control has been applicable, by and large, to problems where parameters appear linearly. We have recently developed an adaptive controller that is capable of estimating parameters that appear nonlinearly in dynamic systems in a stable manner. In this paper, we present this algorithm and its applicability to two problems, temperature regulation in chemical reactors and precise positioning using magnetic bearings both of which contain nonlinear parametrizations. It is shown in both problems that the proposed controller leads to a significantly better performance than those based on linear parametrizations or linearized dynamics.
Passivity-Based Interaction Controller and Observer for Robot Manipulators
Authors: Siciliano Bruno , Villani Luigi
Published: February 2008

This work presents the design of a passivity-based controller and observer for a robot manipulator interacting with a compliant environment. Regulation of the contact force along the constrained direction and tracking of the end-effector position along the unconstrained directions is achieved; semiglobal exponential stability is proved. The control scheme is implemented in the joint space, and experimental results are illustrated for an open control architecture industrial robot which is endowed with joint position sensors and wrist force sensor, but no joint velocity sensors.
Position and Force Control of Two CRS A460 Robots Manipulating a Flexible Sheet: Theory and Experiment
Authors: Sun Dong , Mills James K.
Published: February 2008

It is verified in theory and experiment that through proper design of the control gains, the simple PD position feedback can control a flexible sheet manipulated by two industrial robots to a desired position while regulating its deformations at the contacts to zero. The offsets of all static deformations of the sheet with reference to the original positions decay to zero. A hybrid controller is further developed to control the motion of the sheet as well as its interactions with the manipulators by adding a force feedforward term to the PD scheme. This is the first time that conventional PD control has been shown to be applicable for use in the manipulation of flexible payload.
Tracking Control of Robot Manipulators Using a Robust Deterministic Control Law
Authors: Kang C.-G. , Horowitz R. , Leitmann G.
Published: February 2008

There have been theoretical developments on the control of dynamic systems based on deterministically uncertain and singularly perturbed models in recent years. In this paper, a robust deterministic control scheme proposed originally by M. Corless et al. is modified, and is applied to the tracking control of robot manipulators. Simulation and experimental studies for a two degree of freedom, direct drive SCARA manipulator are conducted to evaluate the effectiveness of the control scheme.
Approximate Feedback Linearization: A Normal Form Approach
Authors: Talwar S. , Namachchivaya N. Sri , Voulgaris P. G.
Published: February 2008

The emerging field of nonlinear control theory has attempted to alleviate the problem associated with applying linear control theory to nonlinear problems. A segment of nonlinear control theory, called exact feedback linearization, has proven useful in a class of problems satisfying certain controllability and integrability constraints. Approximate feedback linearization has enlarged this class by weakening the integrability conditions, but application of both these techniques remains limited to problems in which a series of linear partial differential equations can easily be solved. By use of the idea of normal forms, from dynamical systems theory, an efficient method of obtaining the necessary coordinate transformation and nonlinear feedback rules is given. This method, which involves the solution of a set of linear algebraic equations, is valid for any dimensional system and any order nonlinearity provided it meets the approximate feedback linearization conditions.
ER Shear Characteristics: Volume Fraction, Shear Rate, Time Response
Authors: Bullough W. A. , Makin J. , Johnson A. R. , Hosseini-Sianaki A. , Firoozian R.
Published: February 2008

Electro-stress and electron-hydraulic time delay are investigated in shear mode tests on ERF (electro-rheological fluid). These parameters are examined using a concentric, Couette clutch operating over a range of shear rates, volume fraction of solid in the ERF, and temperature. Pointers to system design, associated control strategy, fluid selection and optimal operating conditions are derived from these results.
A New High Supply Pressure Pneumatic Flapper-Nozzle With Linear Behavior
Authors: Colin S. , Bonnet A. , Caen R.
Published: February 2008

In order to optimize the devices which incorporate flapper-nozzle systems, the behavior of these systems must be completely modeled theoretically. However, the complexity of the flow between the nozzle and the flapper generally requires an empirical calibration of the discharge coefficients. In this article we will propose two types of flapper-nozzle designs which make completely theoretical determination of steady flow possible. This is required for device optimization. The second design makes it possible to obtain strictly linear behavior, which offers several advantages compared to classic devices. The results of experimental testing correspond closely to the theoretical predictions.
Automated Fault Tree Analysis for Hydraulic Systems
Authors: Hogan P. A. , Burrows C. R. , Edge K. A. , Atkinson R. M. , Montakhab M. R. , Woollons D. J.
Published: February 2008

Fault Tree Analysis is a commonly used technique for assessing the reliability and safety of engineering systems at the design stage but it is tedious and time-consuming to apply. A reconfigurable program is presented which utilizes a library of qualitative component models to enable fault tree type analyses of arbitrary hydraulic circuit configurations. It is applied to the analysis of failures of an experimental rig and a complex industrial system, and some features of its design and performance are discussed.
Constraint Formulation for Invariant Hybrid Position/Force Control of Robots
Authors: Jankowski K. P. , ElMaraghy H. A.
Published: February 2008

This paper focuses on the formulation of constraints for hybrid position/force control of robots. Since the noninvariant nature of the classical approach based on orthogonality of some subspaces has recently been demonstrated, alternative methods are proposed in the paper. The geometrical approach is based on the use of an appropriately located compliant frame in which the position and force controlled directions can be clearly identified. Performing the coordinate transformation using sets of curvilinear coordinates is referred to as the analytical approach. The relation between both approaches is described, and their applicability is discussed. It is shown that the analytical approach is more general. The properties of the task space decomposition are analyzed, and the invariant and noninvariant formulations are discussed. The reasons why some previously published approaches produced results with noninvariant terms and some quantities with a misleading physical sense are explained. Two examples illustrate the application of both approaches.
Parametric Control of Conservative Mechanical Systems
Authors: Rahn C. D. , Mote C. D.
Published: February 2008

Parametric excitation is used to control the vibration of a conservative mechanical system. The excitation is varied according to a quadratic, state feedback, control law. If the system has distinct eigenvalues and a full rank, diagonalizable, parametric control matrix, then the control law is asymptotically stabilizing. To eliminate the required full state sensing, an observer is designed to estimate the states from the minimum number of linear measurements. There always exists an observer if the system is linearly observable and the control is bounded. An example demonstrates the method.
Variable Structure Hybrid Control of Manipulators in Unconstrained and Constrained Motion
Authors: Zhen Robert R. Y. , Goldenberg Andrew A.
Published: February 2008

This paper addresses the problem of robust hybrid position and force control of robot manipulators. Variable structure control with sliding mode is used to implement the hybrid control strategy. Two variable structure control algorithms are developed in task space. One of the algorithms is based on hierarchical control method, and the other is developed for control of robot manipulators used to carried out both unconstrained and constrained tasks.
Numerical Approach to Nonlinear Control Design
Authors: Ostojic Mile
Published: February 2008

The paper presents a new approach to designing tracking control of uncertain nonlinear plants. The approach is entirely based on numerical methods and corresponding recurrence relations. It results in recursive control laws that resolve plant nonlinearities and compensate all disturbances and parameter variations. Also, it enables a free shaping of the control error dynamics. Control algorithms based on the method of successive substitutions and the Newton’s method are studied in detail. Detailed description of an application and experimental evaluation is included.