bluuebunny/crossref_metadata_2025 huggingface dataset:
A Controller Design for a Class of Nonlinear Systems Using the Lyapunov-Bellman Approach
Authors: Yanushevsky R. T.
Published: March 2008

The method of synthesis for a wide class of nonlinear systems affine in control is considered. The proposed approach is based on the solution of a special optimal control problem. The integrand of the optimized functional is chosen in such a way that the Bellman equation has a desired solution. The nonlinear system design is reduced to the examination of the integrand of the optimized functional. To extend the domain of asymptotic stability of the nonlinear system, a sequence of the Lyapunov functions is used. The whole system becomes a system with variable structure.
Effects of Noise on Sensor Placement for On-Orbit Modal Identification of Large Space Structures
Authors: Kammer D. C.
Published: March 2008

A method of sensor placement for the purpose on-orbit modal identification and test-analysis correlation is presented. The method is an extension of the Effective Independence method presented in past work to include the effects of a general representation of measurement noise. Sensor noise can be distributed nonuniformly throughout the structure as well as correlated between sensors. The only restriction is that the corresponding noise covariance intensity matrix is positive definite. The technique presented offers a fast and efficient approach for reducing a relatively large initial candidate sensor location set to a much smaller optimum set which retains the linear independence of the target modes and maintains the determinant of the Fisher Information Matrix resulting in improved modal response estimates. The noise covariance intensity matrix which has been introduced into the method can be thought of as a sensor weighting matrix which modifies the shape of the target modes. The mode shape coefficients are modified based upon the noise levels at the sensor locations. Inclusion of the noise model results in higher ranking of sensor locations with low noise levels and suppression of sensor locations with high noise levels. A criterion is also presented which can be used during the course of the sensor placement analysis to determine how many sensors are required to maintain a desired level of signal-to-noise ratio over all the target modes. Simple numerical examples are presented which clearly demonstrate the ideas and trends presented in the paper.
Identification of a Simulation Model and a Control Model for a Coke Oven Battery Operating Under Transient Conditions
Authors: Be´nard C. , Rosset-Loue¨rat M.-M.
Published: March 2008

This work addresses the problem of identifying a model of a coke oven plant that would allow its control under unsteady operating conditions. Knowing that coal thermal kinetics in the oven are the most significant factors affecting the resulting coke quality, considering that control is global since all the heating chambers of a battery are supplied by the same feeder, and that constraints arising in the process involve local and global variables, our study is based on the use of two dynamic models: a detailed elementary model of one oven and a global model of the plant. The first model is deduced from a detailed physical model and gives, for an elementary oven, the relationship between the heating power input and the coke temperature output or coke-gas yield indicator. It is tested by comparison with measurement performed at the Sollac-Fos plant. The second model is a lumped state representation that describes, with a few state variables, the evolution of the two batteries. Its parameters are identified with the help of measurements performed at the Sollac-Fos plant.
Application of a Generalized Actuator Model to the Study of Energy Regeneration Control Strategies
Authors: Heinzmann R. Kurt , Seth Bhartendu , Turi Janos
Published: March 2008

This paper illustrates the implementation of a method to optimize energy regeneration in a variety of dynamic systems. Two control strategies were first simulated on a computer and then tested on an electro-mechanical apparatus. The test apparatus consisted of a battery powered mechanism containing a d-c motor, an electric power converter and a brake, connected to an active load simulator. The simulations and the tests confirmed that in many cases, to maximize regeneration, some power must be dissipated in a brake. For high torque at low speed, regeneration could be achieved only if a brake was used in conjunction with the actuator.
Simplified Dynamic Model for Amount of Directional Correction of Small-Diameter Tunneling Robot
Authors: Aoshima Shin-ichi , Yabuta Tetsuro
Published: March 2008

In the last decade, small-diameter tunneling technology has improved considerably. As a result, the use of this technology is expected to increase dramatically [1]. For example, one microtunneling system can produce microtunnels ranging in diameter from 45 to 150 mm by using mechanically assisted high-pressure, low-volume fluid jets [2]. However, no dynamic model or automatic direction control has yet been designed for this technology. This paper describes a simplified dynamic model for the amount of vertical directional correction for a small-diameter tunneling robot designed to install telecommunication cable conduit. This model can also be used for the horizontal direction. The direction control of a tunneling robot conventionally depends on both the experience and intuition of the operator, and there have been no studies with regard to its automation. Therefore, in order to establish an automatic control technology for a small-diameter tunneling robot, we construct a simplified dynamic model for the amount of directional correction of the robot taking its past trajectory into consideration. We can make a dynamic simulator for the tunneling robot using this dynamic model. With this simulator, we can establish control laws for robot control. So, this study can contribute to the development of automatic control technology for a tunneling robot.
Sensor-Based Chatter Detection and Avoidance by Spindle Speed Selection
Authors: Smith S. , Delio T.
Published: March 2008

This paper presents the results of a series of experimental studies of a control system which, based on information from available sensors (in this case a microphone was primarily used), automatically adjusts the spindle speed and the feed rate so as to achieve stable milling. It is seen that by iteratively adjusting the spindle speed so that the frequency with which the teeth pass is equal to the dominant frequency in the spectrum of the sensor output, the system will very quickly be driven into a stable region, if such a stable region exists. Experimental results which confirm the applicability of this control scheme to a variety of milling operations are presented. They include slotting and partial immersion cuts in cast iron and aluminum. Since this strategy is based on information supplied by the sensors, it is capable of adapting to tool changes, thin webs, corners, etc… which cause changes in the dynamics of the machine-tool-workpiece system and therefore may cause chatter to arise during the course of a milling operation. This strategy does not require an a priori knowledge of the dynamics of the machine-tool-workpiece system as do most of the off-line methods.
Linear Quadratic Regulator With Varying Finite Time Durations
Authors: Tasch Uri , Nagurka Mark L.
Published: March 2008

The optimal state trajectories of time-invariant linear quadratic regulator problems with different time horizons can be found from a single Riccati gain matrix shifted appropriately in time. This result has significant ramifications for real-time implementation of optimal controllers driving systems at various speeds.
Control and System Design for the Czochralski Crystal Growth Process
Authors: Gevelber M. A. , Stephanopoulos G.
Published: March 2008

An expanded set of control objectives is proposed for the Czochralski crystal growth process. Consideration of the thermal stress near the interface yields an operating regime specification in terms of interface shape. A lumped parameter model is used to determine the performance of alternate inputs and outputs. Based on these considerations, a new control structure is proposed to maintain crystal diameter, interface shape, and thermal gradients throughout the batch growth cycle. The performance of alternative control structures are evaluated.
High-Speed Vehicle Models Based on a New Concept of Vehicle/Structure Interaction Component: Part II—Algorithmic Treatment and Results for Multispan Guideways
Authors: Vu-Quoc L. , Olsson M.
Published: March 2008

The predictor structural equations for the vehicle models developed in Part I are derived here for use with a new class of predictor/corrector algorithms to solve the mildly nonlinear equations of motion of the vehicle/structure models. Having all accelerations of the vehicle component eliminated, and with the aid of further simplifying approximations, the predictor structural equations are linear with respect to the structural degrees of freedom. In the algorithms, the predictor structural equations are different from the corrector structural equations; the proposed algorithmic treatment has been proved (elsewhere) to yield accurate energy balance. Results obtained for both continuous and discontinuous guideways are discussed, and optimal guideway configurations suggested. Effects of high-speed vehicle braking on a flexible guideway are analyzed using the vehicle models and the proposed algorithmic treatment. The influence of the guideway flexibility on the vehicle speed, an important feature of the present formulation, is clearly demonstrated.
On the Use of Robust Design Methods in Vehicle Longitudinal Controller Design
Authors: Hauksdo´ttir A. S. , Sigurðardo´ttir G.
Published: March 2008

A robustness-based methodology for designing a vehicle longitudinal controller is presented. The resulting controller, which is intended for point-following operations, is applied to velocity-dependent (slowly varying) automobile dynamics. The results obtained effectively demonstrate how robust design methods may be applied to this class of dynamics. Further, similar approaches might be applied to controller designs for vehicles under different operating modes, e.g., under car-following operations. The design consists of a cascade compensator, which is selected to achieve small tracking errors, and an observer/controller compensator. Kharitonov-related robustness methods are used to design a fixed (constant coefficient) observer/controller, such that the resulting closed-loop pole-clusters are confined to an acceptable area of the s-plane. The performance of the resulting overall system is evaluated using a large-signal, entry merging command and some small-signal mainline commands. The results are comparable to ones obtained by utilizing more complex controllers based on parameter (gain) scheduling [1,2] and nonlinear design methods [3] and designed to achieve a velocity-invariant response.
Multibody Systems With Loops: A Pseudo-Constraint Approach
Authors: Samin J.-C. , Willems P.-Y.
Published: March 2008

The paper presents an original approach for solving kinematical problems related to constraints, in particular those appearing in multibody systems with loops. This approach uses linear combinations of the time derivatives of the constraints in order to construct a pseudo-gradient which can be computed from straightforward kinematical considerations. Moreover, this method permits avoiding numerical convergence toward undesired solutions.
Approximate Decoupling of Weakly Nonclassically Damped Linear Second-Order Systems Under Harmonic Excitations
Authors: Shahruz S. M. , Packard A. K.
Published: March 2008

A simple and commonly used approximate technique of solving the normalized equations of motion of a nonclassically damped linear second-order system is to decouple the system equations by neglecting the off-diagonal elements of the normalized damping matrix, and then solve the decoupled equations. This approximate technique can result in a solution with large errors, even when the off-diagonal elements of the normalized damping matrix are small. Large approximation errors can arise in lightly damped systems under harmonic excitations when some of the undamped natural frequencies of the system are close to the excitation frequency. In this paper, a rigorous analysis of the approximation error in lightly damped systems is given. Easy-to-check conditions under which neglecting the off-diagonal elements of the normalized damping matrix can result in large approximation errors are presented.
Exponentially Stable Tracking Control for Multijoint Flexible-Link Manipulators
Authors: Paden B. , Chen D. , Ledesma R. , Bayo E.
Published: March 2008

In this paper we describe a new tracking control law for multijoint flexible-link manipulators. The scheme is a synthesis of the inverse dynamics solution for flexible manipulators developed by Bayo at UCSB and tracking control theory for rigid-link manipulators put forth by Bayard, Wen and others. We show that passive joint controllers, together with the feedforward of nominal joint torques corresponding to a desired end-effector trajectory, results in exponentially stable tracking control. Stability is proved (local to the desired trajectory) for a large class of passive controllers which include proportional and derivative controllers, and lead compensators. The proof is based on a simple Lyapunov analysis and the Positive-Real lemma.
Sampled-Data Optimal Design and Robust Stabilization
Authors: Chen Tongwen , Francis Bruce A.
Published: March 2008

This paper considers sampled-data control of time-delay systems. First we show that under a certain nonpathological sampling condition, a sampled-data system is internally stable in continuous time if and only if the corresponding discretized system is stable in discrete time. Based on this, we then study two sampled-data design problems for (unstable) time-delay systems: ℋ2-optimal disturbance attenuation and robust stabilization. In both cases, the sampled-data problem can be recast via operator methods as exactly a discrete-time problem and hence be solved using known techniques.
Vehicle Lateral Velocity and Yaw Rate Control With Two Independent Control Inputs
Authors: Matsumoto N. , Tomizuka M.
Published: March 2008

In automatic lateral control, which will play a key role in highway automation, vehicles must follow a given path and vehicle direction must be controlled as desired. Therefore, the ideal is for the lateral motion and yaw motion of the vehicle to be controlled independently. This requires at least one additional control input which is independent of the front steering angle. This paper explores the use of two independent control inputs, which are the front steering angle and an extra control input. Three types of extra control inputs are considered: (1) a differential driving torque between the two front wheels; (2) that between the two rear wheels; and (3) the rear steering angle. The analysis utilizing a linearized vehicle model shows that the front and rear independent steering allows a wider variation of lateral velocity and yaw rate in the steady state. A control algorithm with front and rear independent steering, which features continuously changing gains dependent on vehicle velocity and road conditions, is presented. Performance evaluation is based on a simulation study on a nonlinear vehicle model and an experimental study with a laboratory model vehicle.
Model-Based Maneuvering Controls for Autonomous Underwater Vehicles
Authors: Healey A. J.
Published: March 2008

This paper proposes the development of a model following autopilot system for an Autonomous Underwater Vehicle (AUV) depth changing control. The parameters to command a maneuver are generated off-line and selected as appropriate by the vehicle’s autonomous control system. A series of such preprogrammed maneuvers can be stored in an on-board computer, and used as command generation systems for the autopilot. The paper presents a linear model following control (LMFC) design based on the open-loop linearized vehicle model as the reference model, a robustness analysis of the scheme and simulation results of response in the diveplane using the full nonlinear vehicle system equations. LMFC has been proposed for aircraft where certain desirable handling characteristics based on an arbitrary model are required or where decoupled control for Control Configured Vehicle (CCV) performance is needed. It is shown here that this model-based LMFC autopilot for underwater vehicles exhibits relatively robust behavior under conditions of parameter uncertainty and non-linearity which is not worse than the equivalent LQR/LTR for linear output feedback systems. Also, a tailored transient response is provided, conducive to near time optimal response.
Collision Avoidance of a Multiple Degree of Redundancy Manipulator Operating Through a Window
Authors: Zghal H. , Dubey R. V. , Euler J. A.
Published: March 2008

The problem of collision-free operation of a multiple-degree-of-redundancy manipulator operating through a window is addressed. An efficient gradient projection optimization scheme is presented for the kinematic control of manipulators with multiple degrees of redundancy. This scheme was developed for dextrous robotic and telerobotic applications in space station construction as well as in congested shop floor environment. A performance criterion is defined to maximize the shortest distances between the manipulator links and the edges of the window. Effectiveness of this scheme and the validity of the performance criterion are verified through simulations of the seven-degree-of-freedom NASA Laboratory Telerobotic Manipulator (LTM).
Control of Spin-Stabilized Spacecraft With Sloshing Fluid Stores
Authors: Hill D. E. , Baumgarten J. R.
Published: March 2008

Spin-stabilized spacecraft with sloshing fluid stores are known to be a source of dynamic instability for certain spacecraft configurations. A time varying linear feedback control law was developed, using an equivalent spherical pendulum mechanical model of the fluid motion coupled to the main body dynamics, which stabilizes the highly nonlinear dynamic system within a large region of operation. The control law was also demonstrated to perform a pointing maneuver. A control design for a specific spacecraft is outlined and implemented by sensing only the main body angular rates and attitude.
Precision Tracking Control of Discrete Time Nonminimum-Phase Systems
Authors: Menq Chia-Hsiang , Chen Jin-jae
Published: March 2008

In this paper, a precision tracking control scheme for linear discrete time nonminimum-phase systems is proposed. This control scheme consists of a preview filter, a tracking-performance filter, a command feedforward controller, and a feedback controller. A command feedforward controller, whose design is based on the minimal order inverse model of the plant being controlled, will result in a completely decoupled system. The preview filter is introduced to compensate the phase and gain errors induced by the nonminimum phase zeros or lightly damped zeros of the system. Using the command feedforward controller along with the proposed preview filter, the tracking performance of the proposed control scheme can be characterized by the frequency response of the tracking-performance filter. For the design of the preview filter, a generalized Nth order preview filter and its associated penalty function that quantifies the tracking error of a design are defined. It is shown that, given the desired bandwidth and the order of the preview filter, the optimal solution for the design of the preview filter can be obtained explicitly. The proposed control scheme together with the optimal preview filter is shown to be very effective in achieving precision tracking control of discrete time MIMO nonminimum phase systems. It is also shown that the tracking performance is improved as the order N of the preview filter is increased.
Interaction Between the Actuators in Loaded Multi-Channel Electrohydraulic Drives
Authors: Ramachandran S. , Dransfield P.
Published: March 2008

This paper describes some of the interaction effects arising between two electrohydraulic servoactuator systems operating to sustain predetermined and separate force programs on a cantilever beam load system. The work is intended to be relevant to the simultaneous multi-channel drive situations of structure fatigue testing rigs, flight simulators, industrial robots and some machine tools. Simulation and experimental responses of a single-actuator system for a few locations of the drive on the beam and of the two-actuator system for a number of location combinations are presented, compared, and discussed. Combinations of step inputs of desired force were used to excite the system. Simulation and experimental responses show reasonable agreement. Interaction and its effects are quantified in terms of dynamic characteristics of the force responses of the actuators measured from the simulation and experimental results. The model for simulation was obtained via power bond graph modeling technique. The results show that interaction modifies the responses of the actuators, and that the level of interaction, its magnitude and nature are functions of the relative positions of the actuators. Interactions and its effects are also examined using simulation for a three-actuator force control system. The results confirm the earlier observation. The relative gain array developed for steady-state analysis of interaction by Bristol and extended by Witcher and McAvoy for use in dynamic situations is developed as a measure of interaction and is designated as interaction index. Interaction index is calculated and presented for a few cases. The results show that interaction index can be used to examine the magnitude and nature of interaction for multi-actuator systems. The objective of this study was to further appreciation of the origins, nature, and effects of interaction on the response patterns of several powered actuator systems acting simultaneously on one load.
Fool’s Paradise: The Wedding Dance of Physics and Control
Authors: Paynter Henry M.
Published: March 2008

This paper discusses the subtle interplay between physics and control guided by the metaphor of a marriage, with its wedding dance, shivaree and consummation. Physics is constrained by conservation, control, by causality. The revolutionary concept of a signal is the shotgun that forced the wedding.
Reflections on Engineering Systems and Bond Graphs
Authors: Rosenberg R. C.
Published: March 2008

An important aspect of modern engineering systems is their great diversity. Often they include interactions among different physical domains, contain control subsystems, and are large-scale and complex. The bond graph is a powerful and versatile tool that can help the engineer to design modern engineering systems. Three issues are explored from a bond graph perspective: modeling of engineering systems, simulation of their behavior, and teaching about engineering systems. It is the author’s observation that bond graph methodology is one of the most useful engineering system techniques available and belongs in the problem-solving tool kit of every mechanical engineer. This paper develops a rationale for this viewpoint both for readers familiar with bond graph methods and for readers to whom they are new.
From Robots to Design
Authors: Whitney Daniel E.
Published: March 2008

This paper describes the evolution of the author’s research focus from a single manufacturing technology, robots, to a broader and less technical focus on design processes. This evolution was not haphazard, but was prompted by technical and nontechnical lessons acquired while performing research and attempting to apply it in industrial settings. The inability of any one technology to solve a wide range of problems, and the inability of technology alone to impact the complexities of manufacturing are among the facts learned. What follows is a rather personal account of this evolution.
On One Approach to the Control of Uncertain Systems
Authors: Leitmann G.
Published: March 2008

This paper is a personal history of one area of research with which I have been concerned over the past twenty years and which continues to attract my albeit waning attention, the control of dynamical systems based on uncertain models. Thus, it is a subjective account of various factors which I believe to have steered me to approach the problem via a constructive use of Lyapunov stability theory.
Evolution of Adaptive Control
Authors: Landau Ioan D.
Published: March 2008

The evolution of the adaptive control algorithms driven by the results obtained in the application of the 1st generation of adaptive controllers (model reference adaptive control, self-tuning minimum variance) is examined. Research in the field of adaptive control has been directed, on the one hand, toward the development of a robust general purpose adaptive controller and, on the other, towards the extension of the model reference adaptive control approach to nonlinear systems. Research has also investigated the stability/passivity approach for developing dedicated adaptive control algorithms for particular classes of nonlinear plants (e.g., rigid robots). The paper will review the results obtained in these directions both from the theoretical and the practical points of view. In the final part, current research directions will be included.
Learning Control of Robot Manipulators
Authors: Horowitz Roberto
Published: March 2008

Learning control encompasses a class of control algorithms for programmable machines such as robots which attain, through an iterative process, the motor dexterity that enables the machine to execute complex tasks. In this paper we discuss the use of function identification and adaptive control algorithms in learning controllers for robot manipulators. In particular, we discuss the similarities and differences between betterment learning schemes, repetitive controllers and adaptive learning schemes based on integral transforms. The stability and convergence properties of adaptive learning algorithms based on integral transforms are highlighted and experimental results illustrating some of these properties are presented.
Linear, Multivariable Robust Control With a μ Perspective
Authors: Packard Andy , Doyle John , Balas Gary
Published: March 2008

The structured singular value is a linear algebra tool developed to study a particular class of matrix perturbation problems arising in robust feedback control of multivariable systems. These perturbations are called linear fractional, and are a natural way to model many types of uncertainty in linear systems, including state-space parameter uncertainty, multiplicative and additive unmodeled dynamics uncertainty, and coprime factor and gap metric uncertainty. The structured singular value theory provides a natural extension of classical SISO robustness measures and concepts to MIMO systems. The structured singular value analysis, coupled with approximate synthesis methods, make it possible to study the tradeoff between performance and uncertainty that occurs in all feedback systems. In MIMO systems, the complexity of the spatial interactions in the loop gains make it difficult to heuristically quantify the tradeoffs that must occur. This paper will look at the role played by the structured singular value (and its computable bounds) in answering these questions, as well as its role in the general robust, multivariable control analysis and design problem.
Real Time Estimation of Elastic Deformation for End-Point Tracking Control of Flexible Two-Link Manipulators
Authors: Xia Jack Zhijie , Menq Chia-Hsiang
Published: March 2008

In this paper, an elastic-deformation estimator is proposed for real time end-point tracking control of a flexible two-link manipulator. Due to the noncolocated characteristics of the system, the inverse model (from end-point motion to control torques) is divided into two subsystems, namely, the stable subsystem and the unstable one, corresponding to the causal part and noncausal part of the system’s elastic motion, respectively. A digital filter is formulated to replace the unstable subsystem so as to estimate the noncausal part of the elastic motion associated with a specified end-point motion. For the design of the filter, the frequency response ratio between the filter and the unstable subsystem is used as the criterion, the objective of which is to have the frequency response ratio have zero phase shift as well as unity gain within a specified frequency range. It is shown that due to the noncausal characteristics of the unstable subsystem, preview information of the input trajectory is required for implementing the proposed filter, and the estimation accuracy increases as increasing the preview steps. Based on the stable subsystem and the proposed digital filter, a time-varying estimator is designed to estimate the elastic motion of the system when the end-point motion is specified. A command feedforward controller is then used to calculate the required control torques based on the estimated elastic deformation and the desired end-point motion. The computed torques along with a feedback controller then form a control scheme making the flexible two-link manipulator become capable of precision end-point tracking. Simulation results are presented to show the performance of the proposed end-point tracking scheme as well as the elastic-deformation estimator.
Dynamics of Flexible Manipulator Arms: Alternative Derivation, Verification, and Characteristics for Control
Authors: Yuan B.-S. , Book W. J. , Huggins J. D.
Published: March 2008

This work seeks to provide an effective way for developing the dynamics of a multi-link flexible manipulator consisting of rotary joints connecting two links. Kinematics of both the rotary joint motion and the link deformation are described by 4×4 transformation matrices as proposed in previous works (Book, 1984). The link deflection is assumed small so that the link transformation can be composed of summations of assumed link shapes. To determine the appropriate choice of component mode shapes, two essential techniques employed here are experimental and finite element methods. The resulting equations of motion allow the complete nonlinear model to be recursively derived from the Jacobian matrix and the mass properties via symbolic manipulation. Two prototype models of flexible manipulators are used to verify the dynamics with frequency and time responses. This paper contributes several new results: (1) the velocity terms (Coriolis and centrifugal forces) are related to variations in the mass matrix, (2) the skew symmetry of certain useful terms are shown, (3) the system is theoretically demonstrated to be stable with joint P.D. controllers in addition to an experimental approach, (4) practical and effective incorporation of actuator dynamics (hydraulic cylinder) and structural complexity (non-uniform cross section) is achieved through selection of mode shapes, (5) geometric constraints are incorporated through simplified coordinate transformations and (6) the results are verified on two physical cases.
Sensor Failure Detection in Flexible Structures Using Modal Observers
Authors: Choe K. , Baruh H.
Published: March 2008

A procedure is developed to detect sensor failures in flexible structures by means of observers designed at the modal level. Estimates of the modal coordinates generated by the modal observers are used to estimate the system output at the sensor’s locations. These estimates of the system output are then compared with the sensors’ measurements to detect failure. It is shown that, when the observer gains are properly selected, failure of a certain sensor primarily affects the estimate of that sensor, and it affects the estimates of the operational sensors much less. This makes it possible to detect multiple sensor failures. Because the observers are designed for each mode individually, one can obtain closed-form expressions for the observer poles, making the failure detection procedure applicable to high-order systems.
Stability Analysis of a Bilateral Teleoperating System
Authors: Strassberg Y. , Goldenberg A. A. , Mills J. K.
Published: March 2008

In this paper the stability of a control scheme for bilateral master-slave teleoperation is investigated. Given the nominal models of the master and slave dynamics, and using an approximate feedback linearization control, based on the earlier work of Spong and Vidyasagar, 1987, a robust closed-loop system (position and force) can be obtained with a multiloop version of the small gain theorem. It is shown that stable bilateral teleoperating systems can be achieved under the assumption that the deviation of the models from the actual systems satisfies certain norm inequalities. We also show that, using the proposed scheme, the tracking error (position/velocity and force/torque) is bounded and it can be made arbitrarily small. The control scheme is illustrated using the simulation of a three-degree-of-freedom master-slave teleoperator (three-degree-of-freedom master and three-degree-of-freedom slave).
Dynamic Tire Force Control by Semiactive Suspensions
Authors: Yi Kyongsu , Hedrick Karl
Published: March 2008

This paper presents a semiactive suspension control algorithm to reduce dynamic tire forces and it includes the development and application of observers for bilinear systems with unknown disturbances. The peak dynamic tire forces, which are greatly in excess of static tire forces, are highly dependent on the dynamic characteristics of vehicle suspensions. One way to reduce dynamic tire forces is to use advanced suspension systems such as semiactive suspensions. Semiactive control laws to reduce dynamic tire forces are investigated and a bilinear observer structure for bilinear systems with unknown disturbances is formulated such that the estimation error is independent of the unknown external disturbances and the error dynamics are stable for bounded inputs. The motivation for the development of a disturbance decoupled bilinear observer comes from the state estimation problem in semiactive suspensions. An experimental study on the performance of a semiactive suspension to reduce the dynamic tire forces is made via a laboratory vehicle test rig. The semiactive suspension has been implemented by using a modulable damper, accelerometers and a personal computer. Experimental studies show that the performance of the semiactive suspension is close to that of the best passive suspension for all frequency ranges in the sense of minimizing the dynamic tire forces and that the dynamic tire force can be replaced by the estimated one. The dynamic tire forces for both passive and semiactive control test cases are compared to show the potential of a semiactive suspension to reduce the dynamic tire forces.
Variable Structure Control Method for Fuel-Injected Systems
Authors: Cho Dong-Il Dan , Oh Hee-Keun
Published: March 2008

A nonlinear control method for automotive fuel-injection systems is developed using the theory of variable structure systems. This fuel-injection control method is formulated to be compatible with production sensors and actuators, and its feasibility and potential benefits are demonstrated using a research automobile. The motivation for this research stems from the fact that fuel-injection control is a difficult control problem due to the nonlinear and complex nature of engine dynamics and due to the limitations imposed by a switching-type feedback sensor.
Global Active Noise Control of a One-Dimensional Acoustic Duct Using a Feedback Controller
Authors: Hull A. J. , Radcliffe C. J. , Southward S. C.
Published: March 2008

Active noise control of acoustic enclosures is a classical engineering problem. The active noise control of a one-dimensional hard-walled duct with a partially dissipative boundary condition is addressed in this paper. Previous techniques have attacked this problem by developing adaptive filters designed to cancel acoustic noise at a single measurement location. The work presented here applies modern, state space, control theory to globally reduce noise levels in a one-dimensional acoustic enclosure rather than at a single location. This global control requires only the addition of a single response measurement microphone and control speaker to the open-loop system. Pressure measurements are taken at the microphone location and passed to an observer, which generates estimates of the system states. Using these state estimates, a pole placement feedback control algorithm is used to lower the noise level. Pole placement reduces noise levels globally by increasing the decay rates of all the controlled acoustic states. Experimental results presented here demonstrate reduction in the noise level at all points in the duct by 58 percent when the system is excited by random amplitude pressure input.
A Method for Optimal Step Adjustment for a Class of Linear Quadratic Optimal Control Problems
Authors: Thomopoulos Stelios C. A. , Papadakis Ioannis N. M.
Published: March 2008

In this paper, a new method for the computation of the optimal step in gradient algorithms for a class of linear quadratic optimal control problems is presented. This method improves the convergence of the gradient algorithms and is optimal, i.e., it outperforms any other step searching scheme in the above class of problems.
An Alternate Geometric Perspective on MIMO Systems
Authors: Nagurka M. L. , Kurfess T. R.
Published: March 2008

An alternate graphical representation of linear, time-invariant, multi-input, multi-output (MIMO) system dynamics is proposed that is highly suited for exploring the influence of closed-loop system parameters. The development is based on the adjustment of a scalar forward gain multiplying a cascaded multivariable controller/plant embedded in an output feedback configuration. By tracking the closed-loop eigenvalues as explicit functions of gain, it is possible to visualize the multivariable root loci in a set of “gain plots” consisting of two graphs: (i) magnitude of system eigenvalues versus gain and (ii) argument (angle) of system eigenvalues versus gain. The gain plots offer an alternative perspective of the standard MIMO root locus plot by depicting unambiguously the polar coordinates of each eigenvalue in the complex plane. Two example problems demonstrate the utility of gain plots for interpreting closed-loop multivariable system behavior.
Stability Analysis of a Class of Interconnected Systems
Authors: Barbieri E.
Published: March 2008

There exists a class of systems that is characterized by having a so called regular cellular structure or homogeneous interconnection. In this note, the bilateral Z-Transform is used to obtain a mathematical model parametrized by z and it is shown that the stability properties of the system can be more easily investigated by a simple test applied to the parametrized model. The analysis is illustrated via three examples: the heat equation, the Euler-Bernoulli beam, and decentralized control of a countably infinite string of interconnected mass-spring-damper systems.
Identification of a Nonlinear Function in a Dynamical System
Authors: Messner W. , Horowitz R.
Published: March 2008

Using an adaptive method introduced in (Messner et al., 1991), a standard identification technique for linear systems can be extended to identify nonlinear functions in dynamical systems under a mild condition. Specifically, the assumption is that the nonlinear function can be represented as a integral equation of the first kind. The method identifies the nonlinear function indirectly by estimating the influence function of the integral equation. By analogy to linear methods the kernel of the integral equation serves as the “regressor,” while the influence function is the “parameter” to be identified. This paper focuses on an application to disk drive servos.
Object Manipulation Using Compliant Fingerpads: Modeling and Control
Authors: Annaswamy A. M. , Seto D.
Published: March 2008

Current industrial robots are often required to perform tasks requiring mechanical interactions with their environment. For tasks that require grasping and manipulation of unknown objects, it is crucial for the robot end-effector to be compliant to increase grasp stability and manipulability. The dynamic interactions that occur between such compliant end-effectors and deformable objects that are being manipulated can be described by a class of nonlinear systems. In this paper, we determine algorithms for grasping and manipulation of these objects by using adaptive feedback techniques. Methods for control and adaptive control of the underlying nonlinear system are described. It is shown that although standard geometric techniques for exact feedback linearization techniques are inadequate, yet globally stable adaptive control algorithms can be determined by making use of the stability characteristics of the underlying nonlinear dynamics.
Reduction of the End Effector Sensitivity to the Structural Deflections of a Single Flexible Link: Theoretical and Experimental Results
Authors: Chalhoub Nabil G. , Zhang Xiaoying
Published: March 2008

The fine positioning problem of the gripper of flexible robotic manipulators is addressed in this study. A two-axis cartesian micro-manipulator is implemented to reduce the sensitivity of the gripper to the structural deformations of a single flexible link. A laser head with a dual axis photodetector are used to provide direct measurements of the transverse deflections at the free-end of the beam and to detect mechanical inaccuracies caused by manufacturing imperfections and assembly misalignment. The advantages of the integrated system of the micro-manipulator with a single compliant beam are demonstrated and compared to the one without the micro-manipulator for two different control schemes, “rigid body controller (RBC)” and “rigid and flexible motion controller (RFMC).” Both theoretical and experimental results have proven the capability of the micro-manipulator in significantly improving the gripper positional accuracy. Furthermore, it was demonstrated that the micro-manipulator tends to complement rather than overlap the efforts exerted by the host beam controller.
A Modern Control Approach to Active Noise Control
Authors: Shoureshi R. , Brackney L. , Kubota N. , Batta G.
Published: March 2008

Active noise control systems currently in use and/or described in the research literature are typically based on adaptive signal processing theory or, equivalently, adaptive feedforward control theory. This paper presents a modern control approach to the problem of active noise cancellation in a three-dimensional space. The controller is designed based on a direct self-tuning regulator. Two forms of adaptive control, namely, pole placement and minimum variance controls are considered and compared in simulation. An implementation of the adaptive minimum variance controller is used to successfully attenuate a harmonic disturbance in a laboratory setting.
Preview Control for Vehicle Lateral Guidance in Highway Automation
Authors: Peng Huei , Tomizuka Masayoshi
Published: March 2008

The continuous time deterministic optimal preview control algorithm is applied to the lateral guidance of a vehicle for an automated highway. In the lateral guidance problem, the front wheel steering angle of the vehicle is controlled so that the vehicle follows the center for a lane with small tracking error and maintains good ride quality simultaneously. A preview control algorithm is obtained by minimizing a quadratic performance index which includes terms representing the passenger ride quality as well as the lateral tracking error, each of these terms is multiplied by a frequency dependent weight. This design method is known as a frequency shaped linear quadratic (FSLQ) optimal control approach. It permits incorporating frequency domain design specifications such as high frequency robustness and ride quality in the optimal controller design. It is shown that the optimal preview control law consists of a feedback control term and two feedforward control terms. The feedback term is exactly the same as that of traditional LQ control algorithm. The feedforward preview control action significantly improves the tracking performance and ride quality. Frequency-domain analyses, as well as numerical simulation results, show the improvements achieved by using the preview control algorithm in both the frequency and time domains.
Sliding Mode Control of Automotive Engines
Authors: Moskwa J. J.
Published: March 2008

There is considerable interest in coordinated automotive engine/transmission control for smooth shifts, or for traction control of front wheel drive vehicles. Closed-loop control of the engine has been shown to be useful in improving shift quality. Because of the nonlinear dynamic behavior of the engine, the control method of sliding modes is well suited for engine control algorithms. The authors outline a dynamic engine model, and develop the sliding control laws to follow desired torque converter pump and turbine speed trajectories. The relationships between these desired trajectories and shift quality are also outlined.
Anti-Windup Control of Second-Order Plants With Saturation Nonlinearity
Authors: Leu Ming C. , Yang Sangsik , Meyer Andrew U.
Published: March 2008

All real-world control systems have saturation nonlinearity in final control elements (including actuators). When controllers involve integral action, reset windup can cause instability as well as make system performance unsatisfactory. Based on the describing function method and the generalized Popov criterion, this paper presents analysis of the global stability of a control system having a saturating second-order plant, both with and without using a deadbeat limiting scheme to constrain its controller output. The improvement of system performance by incorporating the anti-windup feature in the controller is illustrated by computer simulations.
Nonlinear Piezo-Actuator Control by Learning Self-Tuning Regulator
Authors: Li C. James , Beigi Homayoon S. M. , Li Shengyi , Liang Jiancheng
Published: March 2008

This paper presents a learning self-tuning (LSTR) regulator which improves the tracking performance of itself while performing repetitive tasks. The controller is a self-tuning regulator based on learning parameter estimation. Experimentally, the controller was used to control the movement of a nonlinear piezoelectric actuator which is a part of the tool positioning system for a diamond turning lathe. Experimental results show that the controller is able to reduce the tracking error through the repetition of the task.
Three Simple and Efficient Methods for Vibration Control of Slewing Flexible Structures
Authors: Liu Y. C. , Yang S. M.
Published: March 2008

Three simple and efficient methods are presented for the vibration control of slewing flexible structures. These methods are developed based on the constrained motion method in which the rotational maneuver is formulated as prescribed trajectory constraint. The constrained motion method in two stage, CMM-TS, accomplishes the first stage rigid-body slewing motion and minimizes the flexible body vibration at terminal state by an optimal control law. The constrained motion method with active damping, CMM-AD, employs piezoelectric actuator with velocity feedback for active damping control. The required slewing time and settling time is governed by the control torque and control voltage, respectively. The third method, CMM-CO, combines the active damping and optimal torque control for vibration suppression during and after the slewing motion. All methods are shown to be efficient in computation, concise in formulation, and effective in hardware realizable application.