bluuebunny/crossref_metadata_2025 huggingface dataset:
High-Speed Vehicle Models Based on a New Concept of Vehicle/Structure Interaction Component: Part I—Formulation
Authors: Vu-Quoc L. , Olsson M.
Published: March 2008

High-speed vehicle/structure models constructed based on a new formulation of dynamic interaction between high-speed vehicles and flexible guideways are presented. A basic vehicle/structure interaction model forms a basic building block of complex vehicle/structure models in which lumped-parameter sub-components of the vehicle component (e.g., suspended masses with springs and dashpots) are assembled onto the basic vehicle/structure interaction component. A vertical and an inclined vehicle models are formulated. These vehicle models can serve as yet more advanced building-block models in the hierarchical construction of complex vehicle/structure models. The inclined vehicle model can be used to study the effects of braking of high-speed vehicles of flexible guideways. Fully nonlinear equations of motion of both models are given. Upon introducing approximations to the nonlinear kinematics, mildly nonlinear equations with an unusual mathematical structure are consistently derived. These equations are appropriate for use under realistic working conditions of the system, and are particularly amenable for numerical treatment using a recently proposed class of predictor/corrector algorithms.
Decoupled Control/Error Weighting for Predictive Control
Authors: Kurfess T. R. , Whitney D. E.
Published: March 2008

This paper presents a basic review and explanation of the predictive control, discusses the inherent inadequacies with the control/error weighting scheme employed by the predictive control, and recommends some modifications to greatly improve its performance. Some simple examples are presented at the end of the paper to verify that the enhanced weighted scheme does, indeed, improve the predictive controller’s performance. Recommendations are also made on the implementation of the new controller.
Neural Networks and Identification of Systems With Unobserved States
Authors: Goh C. J. , Noakes Lyle
Published: March 2008

Consider a nonlinear control system, whose structure is not known (apart from the order of the system) and whose states are not observed. We observe the output of the system for a period of time using persistently exciting input, and use the observation to train a neural network emulator whose output approximates that of the original system. We point out that such an explicit dynamical relationship between the input and the output is useful for the purpose of construction of output feedback controller for nonlinear control systems. Specialization of the method to linear systems allows swift convergence and parameter identification in some cases.
State Estimation Using Randomly Delayed Measurements
Authors: Ray A. , Liou L. W. , Shen J. H.
Published: March 2008

This paper presents a modification of the conventional minimum variance state estimator to accommodate the effects of randomly varying delays in arrival of sensor data at the controller terminal. In this approach, the currently available sensor data is used at each sampling instant to obtain the state estimate which, in turn, can be used to generate the control signal. Recursive relations for the filter dynamics have been derived, and the conditions for uniform asymptotic stability of the filter have been conjectured. Results of simulation experiments using a flight dynamic model of advanced aircraft are presented for performance evaluation of the state estimation filter.
Adaptive Control of Robotic Manipulators Using an Extended Kalman Filter
Authors: Gourdeau R. , Schwartz H. M.
Published: March 2008

This paper presents a new adaptive motion control scheme for robotic manipulators. This is an adaptive computed torque method (CTM) that requires only position measurements. These measurements and the input torques are used in an extended Kalman filter (EKF) to estimate the inertial parameters of the full non-linear robot model as well as the joint positions and velocities. These estimates are used by the CTM to generate the input torques. The theory behind Kalman filtering provides clear guide-lines on the selection of the design parameters for the controller when noise is present. Simulation results illustrate the performance of this scheme and demonstrate its noise rejection properties.
An Adaptive Approach to Motion and Force Control of Multiple Coordinated Robots
Authors: Hu Yan-Ru , Goldenberg A. A.
Published: March 2008

In this paper an approach to motion and force control of multiple coordinated robots, based on an adaptive scheme, is developed. The approach can be used to control the motion of an object held by the robots, the contact force between the object and the environment, and the internal force which do not contribute to the object motion and contact force. Three subsystem error equations are generated, i.e., position error subsystem, contact force error subsystem, and internal force error subsystem. The adaptive law is derived to estimate the unknown parameters of the multiple coordinated robots, the object, and the environment in terms of the three error subsystem equations. The convergence of the position, contact, internal force errors, and parameter errors is analyzed based on the Lyapunov stability theory. The paper shows that the adaptive control scheme improves the position, and the internal and contact force tracking accuracy for a class of robotic systems with uncertain knowledge of the dynamic model.
Output Tracking for a Nonlinear Flexible Arm
Authors: Lucibello P. , Di Benedetto M. D.
Published: March 2008

In this paper, an inversion-based control of the end effector of a two-link flexible robot arm is investigated. The challenge in solving this problem consists in the instability of the inverse system. Arbitrary initialization of the inverse system leads to unbounded elastic vibrations, even if along the desired trajectory the inertial forces associated with the rigid motion are bounded. We show that bounded solutions of the inverse system exist and we provide procedures for computing such solutions in the case of periodic velocities of the end effector. In particular, we consider the case of tracking an unbounded trajectory, e.g., an end point ramp. A technique for the stabilization of the trajectories to be tracked is also proposed and some numerical simulations illustrate the performance of the controlled system.
Decentralized Control of a Class of Large-Scale Systems by Uncertainty Estimator
Authors: Chen Min-Shin
Published: March 2008

A new decentralized controller is proposed for a group of subsystems subject to unknown interconnections and external disturbances. Under the assumption that the interconnections and disturbances satisfy a certain structural condition, the new controller suppresses the disturbances and intercoupling effects completely, making the overall system behave as a decoupled system. In this new control design, each local controller uses an uncertainty estimator proposed by Chen (1990) for estimation of the interconnections and disturbances, and then cancels these undesirable inputs directly. The major advantages of the proposed controller are that the interconnections need not satisfy the so-called “conical” condition, and there is no need for a priori information on the magnitudes of interconnections and disturbances.
Analysis of Linear Time Invariant Systems With Time Delay
Authors: Youcef-Toumi K. , Reddy S.
Published: March 2008

Time Delay Control has recently been suggested as an alternative scheme for control of systems with unknown dynamics and unpredictable disturbances. The proposed control algorithm does not require an explicit plant model nor does it depend on the estimation of specific plant parameters. Rather, it uses information in the recent past to directly estimate the unknown dynamics at any given instant, through time delay. In earlier papers, analysis and implementation of Time Delay Controller for nonlinear systems were discussed. This paper analyzes the continuous Time Delay Controller for a class of linear systems and presents necessary and sufficient conditions for control system stability. A necessary condition for stability is derived using the properties of linear time-delayed systems. This condition involves only a few of the system and controller parameters and facilitates design of the Time Delay Controller. It is proved that this necessary condition is also sufficient if the delay time is chosen to be infinitesimally small. The convergence of closed loop system error to zero for certain classes of inputs and disturbances when the system is stable is also established. It is also shown that certain approximations in the control algorithm and certain additional unmodeled dynamics render the closed loop system under continuous Time Delay Control to be not exponentially stable due to the controller poles on the imaginary axis at infinitely high frequencies. However, in digital implementation, all the signals are prefiltered by anti-aliasing filters prior to sampling. Hence, the highest frequency component is automatically limited and the issue of exponential instability is not encountered. A discussion is presented comparing Time Delay Control with Repetitive Control. It is indicated that the Time Delay Controller can perform the functions of a repetitive controller with the delay time replaced by the period of the reference input while the repetitive controller can perform the functions of Time Delay Controller for sufficiently small “period” for a certain class of linear systems. Furthermore, examples are included to illustrate the results.
Design of Disturbance Decoupled Observer for Bilinear Systems
Authors: Hac´ A.
Published: March 2008

An observer for a bilinear system with an unknown unmeasurable disturbance is considered. Necessary and sufficient conditions for the existence of disturbance decoupled full order and minimal order observers are formulated. The conditions analogous to detectability and pole assignment of linear observers are also given. These conditions provide a basis for verification of observer existence and design procedures to select observer matrices using straightforward matrix calculus. The observers are intended for application to the state estimation of a semi-active vehicle suspension system and the design procedures are illustrated for this particular case. The procedures developed, however, are general and can be applied to any bilinear system.
Passive and Active Inertia Forces in Flexible Body Dynamics
Authors: Hsu W. C. , Shabana A. A.
Published: March 2008

This investigation is devoted to a discussion on the effect of the coupling between the longitudinal and transverse displacements of kinematically driven rotating beams. To this end, the inertia forces that act on a flexible body as the result of the finite rotation are categorized into two classes. These are the passive and active inertia forces. While the effect of the active inertia forces of kinematically driven systems is recognized in the absence of external disturbances and nonzero initial conditions, the passive inertia forces of such systems are not recognized in the case of zero initial conditions and in the absence of external excitations. Depending on the assumed displacement field, three classes of mechanical systems are defined in this paper. These are the active, partially active, and passive systems. The active system has a mathematical model in which both passive and active inertia forces are fully presented. In a partially active system, a part of the passive inertia forces and the active inertia forces appear in the mathematical model. The vibration of the kinematically driven passive system is governed by homogeneous equations which contain only the passive inertia forces. In the case of zero initial conditions and in the absence of external excitation, the response of the passive kinematically driven system is zero regardless of the value of the angular velocity. The effect of the inertia forces of the passive system appear as a time varying modification of the system parameters. It is shown in this investigation that a rotating beam model in which the axial deformation is neglected is a partially active or passive system. It is also demonstrated that the neglect of the effect of the longitudinal displacement has two significant effects. It decouples the modes of vibration and makes the form of the complementary solution independent of the sense of rotation. The behavior of the active, partially active, and passive systems when they are subjected to driving constraints (specified motion) is examined and it is shown that the response of the passive system converges to the partially active system if the effect of the initial conditions becomes dominant as compared to the effect of the active inertia forces of the partially active system.
Formulas for Computing Closed-Loop Time Responses of Flexible Systems Using Truncated Models
Authors: Lacey N. F. , Chait Y. , MacCluer C. B.
Published: March 2008

In this paper we derive formulas for computing the closed-loop time response of an uncertain flexible mechanical system with a truncated model. It is assumed that the dynamics of the flexible mechanical system is described by an infinite series of lightly damped vibration modes. The modal parameters, damping ratio, and natural frequency, are assumed to lie within known ranges. Given a truncated model and a robust control solution, our formulaes define upper and lower bounds for the time response of single-input/output systems about the closed-loop response of the truncated model.
Digital Motion Control and Profile Planning for Pneumatic Servos
Authors: Pu J. , Weston R. H. , Moore P. R.
Published: March 2008

This paper considers the use of “profile-planning” to (i) improve/optimize certain performance characteristics of pneumatic servos and (ii) simplify procedures associated with their tuning. The underlying approach is to preplan the transient behavior of the system thereby generating an appropriate command profile. To assist in applying this technique to the control of air-powered servo-systems, the paper highlights important knowledge derived previously with regard to the stability and operating characteristics of pneumatic drives. Preliminary rules for conducting such planning are then proposed with reference to a series of experimental observations. This approach can be employed to significantly reduce or prevent overshoot and instability of servo-driven pneumatic actuators (cylinders in particular) which are difficult to overcome by using conventional methods. At the same time, increased operating speeds and improved positioning can be attained. The proposed control scheme has been implemented in prototype form through using a proprietary programmable motion controller which incorporates software mechanism for generating gearbox and cam-like motion profiles.
On-Line Tool Wear Estimation Using Force Measurement and a Nonlinear Observer
Authors: Park Jong-Jin , Ulsoy A. Galip
Published: March 2008

On-line tool wear monitoring in metal-cutting operations is essential for an on-line process optimization. In this paper, tool flank wear is estimated on-line by utilizing a nonlinear observer with the feedback of cutting force measurements. Based on a previously developed cutting process model for turning, a nonlinear observer is designed such that the estimated flank wear converges to the actual flank wear development in the presence of poor initial estimates. The stability analysis for the resulting observer error dynamic system is carried out using a physical limitation of the actual flank wear development and the Total Stability Theorem. The experimental results show that the proposed nonlinear observer estimates the flank wear quite well not only in the presence of poor initial estimates but also in the presence of unexpected fluctuations in the cutting force measurements. However, the method has drawbacks resulting from difficulties in obtaining accurate model parameters. An adaptive version of the presented nonlinear observer, periodically calibrated by off-line direct tool wear measurements using computer vision, is considered to be a promising strategy for industrial implementation.
The Influence of Semi-Empirical Control Valve Model Parameter Accuracy on Simulated Hydraulic System Responses
Authors: Handroos H. , Vilenius M.
Published: March 2008

A parameter sensitivity analysis method is applied to an investigation of the importance of the identification accuracy of the parameter values describing the steady-state and dynamic behavior of three commonly used fluid power circuit components, i.e., single-stage pressure relief, reducing, and two-way flow control valves. The component models are verified; these semi-empirical models take into account the most important continuous and discontinuous nonlinearities.
Estimation of Subsample Delays for Computer Control Systems
Authors: Pak H. Ali , Li G. Q.
Published: March 2008

A new method is described for estimating input time delays in linear plants. The method is based on discrete-time domain identification of such delays, and provides direct estimates in real-time. For computer control systems, the delay is allowed to be a noninteger multiple of the sampling period. Both input (actuator) delays and subsample (computational) delays can be estimated. The identification algorithm is based on a recursive Gaussian-Newton prediction error search technique. A simulation study indicating fast convergence for a second order delayed system is included.
Arbitrary Assignment of Eigenvectors With State Feedback
Authors: Shaw Jinsiang , Jayasuriya Suhada
Published: March 2008

Conditions under which eigenvectors of linear multivariable systems can be arbitrarily assigned using state feedback are derived. A procedure for obtaining the required feedback gain matrix is also given. Embedded within the procedure is the freedom to minimize the gain matrix as well as select eigenvalues associated with the assigned eigenvectors. Consequently, arbitrary shaping of the system transient response is possible by concentrating system energy in specific modes. This technique is well suited for applications in the active vibration control of mechanical systems.
Automated Cloth Handling Using Adaptive Force Feedback
Authors: Patton R. , Swern F. , Tricamo S. , van der Veen A.
Published: March 2008

In this paper, a control loop for the handling of cloth is described and tested. The control loop is an adaptive force feedback controller which both provides correct tension on the cloth and straightens wrinkles in the cloth. The control loop was implemented and tested on a PUMA 560 robot with a LORD 15/50 force/torque sensor mounted on its wrist. Experiments demonstrate the ability of the control loop to straighten the cloth and to exert a specified tension on the cloth.
Real-Time Expert System for Fault-Tolerant Supervisory Control
Authors: Ramamurthi K. , Agogino A. M.
Published: March 2008

Many mechanical systems are sufficiently complex that it is impractical to describe their dynamics by exact mathematical models. In the presence of such modeling uncertainties, advanced controllers like adaptive controllers perform better than linear feedback controllers since they actively reduce the uncertainty by online parameter estimation. Unfortunately, the advanced control strategies, due to their lack of robustness, can become unstable in the presence of unpredictable external disturbances, and hence, there exists a need for a fault-tolerant approach to preserve the overall system integrity even at the cost of design performance. This motivated the research, presented in this paper, to investigate the suitability of the IDES (Influence Diagram Based Expert System) as an expert supervisory controller to predict incipient instability, a significant failure mode, and take corrective action in real-time when closed loop stability appears to be in danger. The expert supervisory control scheme is demonstrated on a model-referenced adaptive controller as applied to a robotic manipulator. The real-time expert system, with the information from sensors, dynamically optimizes the cost of control and as a result chooses between a robust auxiliary controller and the nonrobust adaptive controller depending on inferences made from the observable variables. IDES, as a real-time expert supervisory controller, preserves the stability of the system even under potentially destabilizing unexpected disturbances, exhibiting on demand a fault-tolerant behavior by trading design performance for overall system integrity. The results indicate the potential for influence diagram expert systems in monitoring and controlling mechanical systems where exact mathematical models are difficult or not practical to obtain.
Strong Diagonal Dominance by Quantitative Feedback Theory
Authors: Perez R. A. , Nwokah O. D. I. , Thompson D. F.
Published: March 2008

This paper uses strong diagonal dominance theory to obtain a systematic solution to the MIMO-QFT problem by an n times solution of the SISO-QFT sensitivity constraint problem. This is analogous to the current MIMO-QFT formulation that requires an n times solution for the elements of the closed-loop transfer matrix. Of equal but independent interest is the establishment of the first early verifiable existence and uniqueness conditions for robust diagonal stabilizability.
Design Guide of Master Arms Considering Operator Dynamics
Authors: Yokokohji Y. , Yoshikawa T.
Published: March 2008

In this paper, a design guide of master arms for teleoperation is discussed. The quality of the master arm design has a considerable influence on the maneuverability of master-slave systems. A quantitative measure of the manipulative ability of master arms is proposed, and is obtained by extending the concept of the dynamic manipulability. It is pointed out that the directional property of the manipulability ellipsoid in the work space is an important factor. A second quantitative measure is proposed which evaluates the similarity of the manipulability ellipsoids produced by two situations—when the operator maneuvers the master arm and when he has no payload. Numerical examples and several guidelines for master arm design are shown.
A Miniature Mobile Robot Using Piezo Vibration for Mobility in a Thin Tube
Authors: Aoshima Shin-ichi , Tsujimura Takeshi , Yabuta Tetsuro
Published: March 2008

This paper proposes a miniature mobile robot that uses piezo vibration to move within a thin tube. The robot consists of a piezo bimorph with elastic fins attached at an angle. Robot movement is driven by differences in the friction of the fin’s against the tube wall between the forward and backward fin movements induced by piezo vibration. After analyzing the dynamics of the piezo elements, we analyzed the robot’s mobile mechanism by extending Hamilton’s principle using the dynamic results of the piezo vibration analysis. Measurements of both mobile velocity and tractive force of an experimental robot agree closely with theoretical results. This indicates that the proposed dynamic mobile mechanism accurately expresses robot motion within a thin tube.
A New Sensor for Real-Time Milling Tool Condition Monitoring
Authors: Li C. James , Li S. Y.
Published: March 2008

A new sensor has been developed to automatically detect face-milling insert fracture, chipping, and wear. With a befitting PVDF (polyvinylidene fluoride) sensor, and an optical transmitter based on frequency modulation technique, a miniature sensor, with little influence on the cutting process, was positioned very close to the cutting site. Due to this closeness, the state of the insert can be reliably recognized with extremely simple and fast algorithms. A tool wear index which is sensitive to wear but insensitive to cutting conditions, a tool fracture index, and a chipping recognition scheme based on a linear pattern classifier have been developed and proven to be effective by experimental data.
Optimum Settings for Automatic Controllers
Authors: Ziegler J. G. , Nichols N. B.
Published: March 2008

In this paper, the three principal control effects found in present controllers are examined and practical names and units of measurement are proposed for each effect. Corresponding units are proposed for a classification of industrial processes in terms of the two principal characteristics affecting their controllability. Formulas are given which enable the controller settings to be determined from the experimental or calculated values of the lag and unit reaction rate of the process to be controlled. These units form the basis of a quick method for adjusting a controller on the job. The effect of varying each controller setting is shown in a series of chart records. It is believed that the conceptions of control presented in this paper will be of assistance in the adjustment of existing controller applications and in the design of new installations.
Human Centered Control in Robotics and Consumer Product Design
Authors: Asada Harichiko , Federspiel Clifford C. , Liu Sheng
Published: March 2008

Human factors in the control and programming of robots and electric appliances are addressed in this paper. Systems and control techniques for the enhancement of human-machine communication as well as learning and adaptation to human needs are described with exemplary case studies. First, fundamental issues and methodologies, as well as historical perspective of relevant fields, are summarized, and two case studies are then discussed. One is user-adaptable control of air conditioners, a new type of adaptive control that allows an air conditioner to learn the thermal preference of the user. The other is a user-friendly programming method for advanced robot control. A task-level adaptive control system is developed by acquiring control skills by direct communication with human experts. The importance of human-machine communication and its impact on product development are addressed from the systems and control point of view.
Modeling and State Estimator Design Issues for Model-Based Monitoring Systems
Authors: Stein Jeffrey L.
Published: March 2008

The JOURNAL OF DYNAMIC SYSTEMS, MEASUREMENT, AND CONTROL has a rich history in the areas of system modeling, control theory, and system design. In this paper, I demonstrate the primary importance of modeling to the design and performance of model-based (dynamic, observer-based) monitoring systems. The focus is on monitoring rather than diagnostics, but the results show, nevertheless, that good monitoring systems impact the design and performance of diagnostic systems. Modeling procedures, some based on results from the automated modeling literature, are developed to produce not only simple, accurate models to improve estimation accuracy, but also to utilize existing sensors to measure accessible signals, generate models for which estimation techniques exist, and finally to produce models that reduce the complexity of the diagnostic task, thus reducing the heavy reliance on empirical rule-based decision systems. In addition, for model-based monitors based on deterministic state estimators, a design procedure is described to control the shape of the transient error and the steady-state bias error of the estimates. This procedure utilizes a performance index, which accounts for many of the realistic problems encountered in implementing these systems, such as model uncertainty, round-off errors, and unknown initial conditions. Machine tool drive systems are used to motivate and illustrate the monitoring ideas and techniques. Model-based monitoring appears, despite its current limited use in machine monitoring, to hold great potential as the basis for high-performance, low-cost machine monitoring systems.
Analysis and Control of Nonlinear Systems
Authors: Hedrick J. Karl
Published: March 2008

This paper describes my work on nonlinear analysis and control over the last twenty years. The first part of the paper concerns the development of nonlinear analysis tools for predicting stability and forced response characteristics of high speed ground vehicles. The principal motivation was to develop an alternative to “brute force” time domain simulation. The developed tools were extensions of “describing function” or “equivalent linearization” methods for both periodic and stochastic excitation. The “statistical linearization” analysis tools were then extended and applied to design control laws for nonlinear stochastic regulators. The second part of the paper was motivated by control system design for highly nonlinear, multivariable systems, such as automotive powertrain control and aircraft flight control. For these classes of systems, statistical linearization procedures are computationally cumbersome and also provide no stability or robustness guarantees. A method which has proven extremely powerful, both theoretically and experimentally, is “sliding control.” This technique is a form of input/output linearization that directly incorporates model error information with stability and performance measures. My students and I found several difficulties in the direct application of this method to automotive and aircraft control. This paper describes our solutions to the problems of repeated model differentiation, differentiation of model error, undesirable “internal dynamics” and systems with saturating control inputs.
Intelligent Control Systems: Are They for Real?
Authors: Shoureshi Rahmat
Published: March 2008

The fundamental concept of feedback to control dynamic systems has played a major role in many areas of engineering. Increases in complexity and more stringent requirements have introduced new challenges for control systems. This paper presents an introduction to and appreciation for intelligent control systems, their application areas, and justifies their need. Specific problem related to automated human comfort control is discussed. Some analytical derivations related to neural networks and fuzzy optimal control as elements of proposed intelligent control systems, along with experimental results, are presented. A brief glossary of common terminology used in this area is included.
Optimal Feedback Design for Uncertain Systems: A Time-Domain Fixed-Point Approach in L∞
Authors: Barnard R. , Beydoun S.
Published: March 2008

This paper considers an alternative to quantitative feedback theory (QFT), an alternative deriving solely from a time-domain setting in Banach space L∞ and providing both a precise, amplitude-oriented design formulation and a general, computer-oriented design procedure. System dynamics, stability, and tracking are characterized as fixed-point operator equations and conditions under which tracking errors satisfy explicit bounds. The design formulation and procedure are illustrated by two design examples.
Centralized Control of n Identical Plants
Authors: Unbehauen H. , Vakilzadeh I.
Published: March 2008

In an elegant and yet easily comprehensible and applicable way, it is shown how the outputs of n identical plants G(s)=K/sp∏l=1μ(s+al) with different output initial conditions can be made to perfectly track a reference, or command, input r(t) through the commissioning of only one central controller H(s). Two simulations support the theoretical results. The proposed technique has wide applications in industrial plants and research centers: it drastically reduces the effort and cost of controllers dictated by the orthodox one-plant/one-controller philosophy.
Active and passive Damping of Euler-Bernoulli Beams and Their Interactions
Authors: Pang S. T. , Tsao T.-C. , Bergman L. A.
Published: March 2008

Active and Passive damping of Euler-Bernoulli beams and their interactions have been studied using the beam’s exact transfer function model without mode truncation or finite element or finite difference approximation. The combination of viscous and Voigt damping is shown to map the open-loop poles and zeros from the imaginary axis in the undamped case into a circle in the left half plane and into the negative real axis. While active PD collocated control using sky-hooked actuators is known to stabilize the beam, it is shown that the derivative action using proof-mass (reaction-mass) actuators can destabilize the beam.
Time-Optimal Control of Two Robots Holding the Same Workpiece
Authors: Bobrow J. E. , McCarthy J. M. , Chu V. K.
Published: March 2008

An algorithm is given which minimizes the time for two robots holding the same workpiece to move along a given path. The unique feature of these systems is that they have more actuators than degrees of freedom. The method can be applied to any constrained robot system, including the case where one robot arm moves in contact with a surface. In addition to finding the optimum torque histories, the algorithm determines the optimum contact force between the each robot and the workpiece throughout the motion. Constraints on these internal forces are easily introduced into the algorithm.
A Model of Driver Steering Control Behavior for Use in Assessing Vehicle Handling Qualities
Authors: Modjtahedzadeh A. , Hess R. A.
Published: March 2008

A control theoretic model of driver steering control behavior is presented. The resulting model is shown capable of producing driver/vehicle steering responses which compare favorably with those obtained from driver simulation. The model is simple enough to be used by engineers who may not be manual control specialists. The model contains both preview and compensatory steering dynamics. An analytical technique for vehicle handling qualities assessment is briefly discussed. Driver/vehicle responses from two driving tasks evaluated in a driver simulator are used to evaluate the overall validity of the driver/vehicle model. Finally, the model is exercised in predictive fashion in the computer simulation of a lane keeping task on a curving roadway where the simulated vehicle possessed one of three different steering systems: a conventional two-wheel steering system and a pair of four-wheel steering systems.
Nonlinear Analysis of Automotive Hydraulic Engine Mount
Authors: Kim Gun , Singh Rajendra
Published: March 2008

Nonlinear properties of a generic hydraulic mount with an inertia track are identified and characterized by using experimental and analytical approaches. A low-frequency lumped-parameter mathematical model of the hydraulic mount is developed over 1 to 50 Hz, based on the measured nonlinear system parameters such as the steady-state inertia track fluid resistances and fluid chamber compliances. New experiments specifically designed for this study are also described. The effect of temperature on the mount dynamic properties is discussed briefly. When compared with measured signals under sinusoidal testing conditions, our model predicts time and frequency domain responses reasonably well. One of the reasons for some discrepancies between theory and experiment is attributed to the need for an accurate model describing the gas-liquid phase transformation and cavitation phenomenon.
Detection of Cracks in Turborotors—A New Observer Based Method
Authors: So¨ffker D. , Bajkowski J. , Mu¨ller P. C.
Published: March 2008

The clear relation between shaft cracks in turborotors and vibration effects measured in bearings can be established by model-based methods very well. Here a new concept has been presented, based on the theory of disturbance rejection control, extended for nonlinear systems and applied on a turborotor. Simulations have been done, showing the theoretical success of this method, especially for reconstructing disturbance forces as inner forces caused by the crack. Calculating the relative crack compliance as the ratio of additional compliance caused by the crack and undamaged compliance a clear statement about the opening and closing, and therefore for the existence of the crack, and about the crack depth is possible. Theoretically it has been shown that it is possible to detect a crack with very small stiffness changes which corresponds to a crack depth of 5 percent of the radius of the rotor.
A New Plug-In Adaptive Controller for Rejection of Periodic Disturbances
Authors: Hu Jwusheng , Tomizuka Masayoshi
Published: March 2008

In this paper, an adaptive digital algorithm for rejecting periodic disturbances is proposed. Modified from the adaptive tracking controller [4], the controller is constructed in a “plug-in” manner, i.e., it can be added to an existed feedback control system without altering the original closed-loop configuration. It is shown that the controller can reject disturbances at selected frequencies independently. Furthermore, since the controller only deals with phase and gain of the error signal, no structural information about the plant is required. The controller is implemented on a disk drive system for track following. The result shows that by rejecting the disturbance up to four times of its fundamental frequency, the tracking error is reduced substantially.
Decentralized Variable Structure Control Design in Perturbed Nonlinear Systems
Authors: Wang Wen-June , Lee Jia-Ling
Published: March 2008

This paper presents a new robust decentralized variable structure control (DVSC) to stabilize a class of perturbed nonlinear large-scale systems. Only the bounds of perturbations, disturbances and interconnections of the system are needed. Based on Lyapunov theory, the DVSC is designed such that a Lyapunov function converges to a composite switching hyperplane in finite time, at least with an exponential rate. Our design method need not use the dynamic compensation or the integral of interconnections in the sliding mode definition, or the hierarchical control. Furthermore, both the convergence rate and the hitting time can be assigned. Finally, a two-pendulum system is given to illustrate the design method.
PD-Based Trajectory Tracking Control for Robot Manipulators
Authors: Bailin Cao , Huitang Chen
Published: March 2008

In this paper, it is proved that a trajectory tracking system of a manipulator is globally stable if the system is controlled under the decentralized PD control law plus a sliding term with a constant coefficient, and the norm of the coefficient matrix of its differential term is no less than that of the centripetal and Coriolis’ force term corresponding to the desired angular velocity, i.e., ∥Kd∥ ≥ ∥C(q, q˙d)∥. Condition ∥Kd∥ ≥ ∥C(q, q˙d)∥ implies that Kd increases only with q˙d instead of q˙. A type of globally asymptotically stable adaptive sliding mode PD-based control scheme is proposed, and the proof of stability of the system is also given. It is easy to implement in real-time compared with other adaptive control laws as no estimation of gravitational and frictional forces is necessary.
The Effect of Bandwidth of Semiactive Dampers on Vehicle Ride
Authors: Lieh J.
Published: March 2008

A passenger car model with a full car body and four wheel-axle assemblies is used to investigate the influence of semiactive suspensions on ride performance. Mean square values are evaluated for various damping levels and control valve switching times. Due to severe nonlinearities, frequency responses are not obtained directly. They are reconstructed from Fast Fourier Transform (FFT) using a Hanning window. The results are compared with those from LQR active suspensions and pure on-off dampers. The effect of control valve switching time (bandwidth) is studied and shows a significant influence on the vehicle ride, suspension travels, and tire deflections.
Normal Form and Luenberger Observer for Linear Mechanical Descriptor Systems
Authors: Hou M. , Schmidt Th. , Schu¨pphaus R. , Mu¨ller P. C.
Published: March 2008

Normal forms are presented for linear mechanical systems with holonomic and/or nonholonomic constraints. These forms provide deep insight into the peculiar system structure of constrained linear mechanical systems or the so-called linear mechanical descriptor systems. Based on these normal forms, an explicit observer design method is proposed under a weaker observability assumption, i.e., finite observability or reachable observability on the linear mechanical descriptor systems. The observer has the Luenberger observer form and provides the estimation of displacements, velocities, and constraint forces simultaneously. The finite observability is shown to be a necessary and sufficient condition for the existence of this type of observer. The reason for the existence of the Luenberger observers for finitely observable linear mechanical descriptor systems is due to the special system structure. Two examples are included to illustrate the design method.
Real-Time Simulation of Multibody Dynamics on Shared Memory Multiprocessors
Authors: Chung Shu , Haug Edward J.
Published: March 2008

This paper presents a recursive variational formulation for real-time simulation of multibody mechanical systems on shared memory parallel computers. Static scheduling algorithms are employed to evenly distribute computation on shared memory multi-processors. Based on the methods developed, a general-purpose dynamic simulation program is shown to simulate multibody systems faster than real-time, enabling operator-in-the-loop simulation of ground vehicles and robots.
Autonomous System for Multistage Cylindrical Grinding
Authors: Xiao Guoxian , Malkin Stephen , Danai Kourosh
Published: March 2008

An optimization strategy is presented for cylindrical plunge grinding operations. The optimization strategy is designed to minimize cycle time while satisfying production constraints. Monotonicity analysis together with local linearization are used to simplify the non-linear optimization problem and determine the process variables for the optimal cycle. At the end of each cycle, the uncertain parameters of the process are estimated from sensory data so as to provide a more accurate estimation of the optimal process variables for the subsequent cycle. The optimization strategy is validated both in simulation and for actual grinding tests.
On the SPR Condition in Output Error Estimation Schemes
Authors: Dahleh M. , Ricci M.
Published: March 2008

In this paper we will analyze the SPR condition in output error adaptive estimation schemes. An idea of Tomizuka is used to reduce the restrictive nature of the SPR condition, and is strengthened by exploiting certain a priori information on the uncertainty structure of the underlying plant, which is represented by an interval plant description. New results for the analysis of these types of systems are obtained, and are subsequently incorporated in the analysis of the adaptive system.
Interpolated Mapping System Identification for Free and Forced Systems
Authors: Bursal F. H. , Tongue B. H.
Published: March 2008

In this paper, we discuss a method of system identification based on Interpolated Mapping (IM). The method assumes the presence of sampled values of system states, based on which a map is defined that takes a set of initial conditions to their respective images. Using this map with time step T, maps with time steps T/2, T/4, …, are subsequently found. Ultimately, when the time step has become small enough, difference quotients are used to estimate the state derivatives. A function fit can then be applied to these derivatives in order to obtain the equations of motion of the system. The methodology of IM is used to approximate the images of states that are not on the primary grid. The above scheme works for autonomous systems because a single map can be used to follow the progress of the system at all times; the vector field of the system is invariant with time. However, the procedure breaks down when the system is forced. In this case, time enters the equations of motion explicitly, and different vector fields (and, hence, different maps) exist at different times. We show in this paper that the necessary modifications to the basic methodology are relatively minor. The work and storage requirements can increase by as little as a factor of two, regardless of the dimension of the state space. This is essentially a result of the fact that IM may be used to perform interpolation in the time direction, as well. However, when the forcing is such that its variation over time is entirely unknown, more data would be required to correctly observe its progress over the time period of interest. Functions of time that are flat for small times also necessitate additional effort for proper identification.
Inertia Matrix Singularity of Series-Chain Spatial Manipulators With Point Masses
Authors: Agrawal Sunil K.
Published: March 2008

Often, the dynamic behavior of multi-degree-of-freedom mechanical systems such as robots and manipulators is studied by computer simulation. An important step in this simulation is the inversion of inertia matrix of the system. In singular configurations of the inertia matrix, the simulation is prone to large numerical errors. Usually, it is believed that an inertia matrix is always positive definite. In this paper, it is shown that for spatial series-chain manipulators, when the links are modeled as point masses, a multitude of configurations exists when the inertia matrix becomes singular. These singularities arise because point masses lead to incomplete models of the system.
Analytic Loop Shaping Methods in Quantitative Feedback Theory
Authors: Thompson D. F. , Nwokah O. D. I.
Published: March 2008

Quantitative Feedback Theory (QFT), a robust control design method introduced by Horowitz, has been shown to be useful in many cases of multi-input, multi-output (MIMO) parametrically uncertain systems. Prominent is the capability for direct design to closed-loop frequency response specifications. In this paper, the theory and development of optimization-based algorithms for design of minimum-gain controllers is presented, including an illustrative example. Since MIMO QFT design is reduced to a series of equivalent single-input, single-output (SISO) designs, the emphasis is on the SISO case.
A Time-Domain Inverse Dynamic Tracking Control of a Single-Link Flexible Manipulator
Authors: Kwon Dong-Soo , Book Wayne J.
Published: March 2008

A manipulator system with a large workspace volume and high payload capacity has greater link flexibility than do typical industrial robots and teleoperators. If link flexibility is significant, position control of the manipulator’s end-effector exhibits nonminimum-phase, noncollocated, and flexible-structure system control problems. This paper addresses inverse dynamic trajectory planning issues of a single-link flexible manipulator. The inverse dynamic equation of a single-link flexible manipulator was solved in the time-domain. By dividing the inverse system equation into its causal part and anticausal part, the inverse dynamic method calculates the feed-forward torque and the trajectories of all state variables that do not excite structural vibrations for a given end-point trajectory. Through simulation and experiment with a single-link manipulator, the effectiveness of the inverse dynamic method in producing fast and vibration-free motion has been demonstrated.
Dynamic Analysis of Noncollocated Flexible Arms and Design of Torque Transmission Mechanisms
Authors: Park Jahng-Hyon , Asada Haruhiko
Published: March 2008

A new actuation method for one-link flexible arms is presented. The endpoint control of a flexible arm has been known as a nonminimum phase system due to the noncollocated sensor and actuator. By relocating the actuator near the endpoint, the system can be modified to approximate a minimum phase system. In order to implement this, transmission mechanisms are developed which transform the actuator torque to a combination of force and torque and transmit them to an appropriate point on the arm link. Exact pole-zero configurations are analyzed with regard to the location of the actuation point and the type of actuator used. Guidelines for design of the transmission mechanisms and the actuation points are developed with respect to the operation bandwidth, stability and controllability. A prototype flexible arm is designed based on the design guidelines and open-loop and closed-loop tests are performed to verify the effectiveness.