Showing papers on "Control theory published in 1985"

Nonlinear Control Systems

Abstract: : The principal goal of this three years research effort was to enhance the research base which would support efforts to systematically control, or take advantage of, dominant nonlinear or distributed parameter effects in the evolution of complex dynamical systems. Such an enhancement is intended to support the development of flight controllers for increasing the high angle of attack or high agility capabilities of existing and future generations of aircraft and missiles. The principal investigating team has succeeded in the development of a systematic methodology for designing feedback control laws solving the problems of asymptotic tracking and disturbance rejection for nonlinear systems with unknown, or uncertain, real parameters. Another successful research project was the development of a systematic feedback design theory for solving the problems of asymptotic tracking and disturbance rejection for linear distributed parameter systems. The technical details which needed to be overcome are discussed more fully in this final report.

Distributed Piezoelectric-Polymer Active Vibration Control of a Cantilever Beam

Abstract: An active vibration damper for a cantilever beam was designed using a distributed-parameter actuator and distributed-parameter control theory. The distributed-parameter actuator was a piezoelectric polymer, poly (vinylidene fluoride). Lyapunov's second method for distributed-parameter systems was used to design a control algorithm for the damper. If the angular velocity of the tip of the beam is known, all modes of the beam can be controlled simultaneously. Preliminary testing of the damper was performed on the first mode of the cantilever beam. A linear constant-gain controller and a nonlinear constant-amplitude controller were compared. The baseline loss factor of the first mode was 0.003 for large-amplitude vibrations (± 2 cm tip displacement) decreasing to 0.001 for small vibrations (±0.5 mm tip displacement). The constant-gain controller provided more than a factor of two increase in the modal damping with a feedback voltage limit of 200 V rms. With the same voltage limit, the constant-amplitude controller achieved the same damping as the constant-gain controller for large vibrations, but increased the modal loss factor by more than an order of magnitude to at least 0.040 for small vibration levels.

The Robust Control of Robot Manipulators

Abstract: A new scheme is presented for the accurate tracking control of robot manipulators. Based on the more general suction control methodology, the scheme addresses the following problem: Given the extent of parametric uncertainty (such as imprecisions or inertias, geometry, loads) and the frequency range of unmodeled dynamics (such as unmodeled structural modes, neglected time delays), design a nonlinear feedback controller to achieve optimal tracking performance, in a suitable sense. The methodology is compared with standard algorithms such as the computed torque method and is shown to combine in practice improved performance with simpler and more tractable controller designs.

Industrial applications of fuzzy control

Abstract: Preface. Automatic Train Operation System by Predictive Fuzzy Control (S. Yasunobu, S. Miyamoto). Application of Fuzzy Reasoning to the Water Purification Process (O. Yagashita, O. Itoh, M. Sugeno). The Application of a Fuzzy Controller to the Control of a Multi-Degree-of-Freedom Robot Arm (E.M. Scharf, N.J. Mandic). Optimizing Control of a Diesel Engine (Y. Murayama et al.). Development of Performance Adaptive Fuzzy Controllers with Application to Continuous Casting Plants (G. Bartolini et al.). A Fuzzy Logic Controller for Aircraft Flight Control (L.I. Larkin). Automobile Speed Control System Using a Fuzzy Logic Controller (S. Murakami, M. Maeda). An Experimental Study on Fuzzy Parking Control Using a Model Car (M. Sugeno, K. Murakami). A Fuzzy Controller in Turning Process Automation (Y. Sakai, K. Ohkusa). Design of Fuzzy Control Algorithms with the Aid of Fuzzy Models (W. Pedrycz). Human Operator's Fuzzy Model in Man-Machine System with a Nonlinear Controlled Object (K. Matsushima, H. Sugiyama). The Influence of Some Parameters on the Accuracy of a Fuzzy Model (J.B. Kiszka, M.E. Kochanska, D.S. Sliwinska). A Microprocessor Based Fuzzy Controller for Industrial Purposes (T. Yamazaki, M. Sugeno). The Application of Fuzzy and Artificial Intelligence Methods in the Building of a Blast Furnace Smelting Process Model (H. Zhao, M. Ma). An Annotated Bibliography of Fuzzy Control (R.M. Tong).

A new design of constrained controllers for linear systems

Abstract: A new method is presented to find stabilizing saturated linear state feedback controllers for linear continuous-time and discrete-time systems. A controller of this type was satisfactorily tested on board a submarine as a depth regulator.

Microcomputer Control of a Residential Photovoltaic Power Conditioning System

Abstract: Microcomputer-based control of a residential photovoltaic power conditioning system is described. The microcomputer is responsible for array current feedback control, maximum power tracking control, array safe zone steering control, phase-locked reference wave synthesis, sequencing control, and some diagnostics. The control functions are implemented using Intel 8751 single-chip microcomputer-based hardware and software. The controller has been tested in the laboratory with the prototype power conditioner and shows excellent performance.

Modeling and feedback control of a flexible arm

Abstract: When a flexible arm is rotated by a motor about an axis through the arm's fixed end, transverse vibration may occur. The motor torque should be controlled in such a way that the motor rotates by a specified angle, while simultaneously stabilizing vibration of the flexible arm so that it is arrested as soon as possible at the end of rotation. In this paper, we first derive a partial differential equation and a set of boundary conditions governing the vibration. Then, a feedback control system which incorporates a dynamic compensator is designed using sensor outputs. A set of experiments has been constructed to demonstrate control strategies for a flexible arm, where a strain gage was used as a vibration sensor and a microcomputer was equipped as a controller. Several satisfactory experimental results are shown.

A covariance control theory

Abstract: There is much theory for the use of covariance matrices in both identification and in state estimation. However, there exists no theory for the control of covariances. The need for a theory of covariance control may be argued from two points: 1) Many engineering systems have performance requirements which are naturally stated in terms of root-mean-square (RMS) values of the system states or outputs and 2) the various theories of identification, estimation, and model reduction use covariances as a measure of performance. Hence a theory on covariance control may help unify the modeling and control problem. This paper introduces a theory for designing linear feedback controllers so that the closed loop system achieves a specified state covariance.

On-Line Efficiency Optimization of a Variable Frequency Induction Motor Drive

Abstract: The problems associated with the implementation of an optimal efficiency controller in variable frequency induction motor drives are examined. A simple method for minimizing, on-line, the global system losses is presented. This method is based on the adaptive control of the rotor flux in a field-oriented drive system. The effectiveness of this control strategy is verified using digital simulation.

Design of an optimal controller for a discrete-time system subject to previewable demand

Abstract: This paper is concerned with a method of designing a type one servomechanism for a discrete-time system subject to a time-varying demand and an unmeasurable constant disturbance. It is assumed that the time-varying demand is previewable in the sense that some finite future as well as present and past values of the demands are available at each time. A controller with state feedback plus integral and preview actions is derived by applying a linear quadratic integral (LQI) technique due to Tomizuka and Rosenthal (1979). It is shown under the stabilizability and detectability conditions that the closed-loop system achieves a complete regulation in the presence of small perturbations in system parameters, eliminating the effect of disturbance. An example of power plant control is presented to show the flexibility of the design method and the effectiveness of the preview action for improving the transient responses of the closed-loop system.

Hand controllers for teleoperation. A state-of-the-art technology survey and evaluation

Abstract: Hand controller technology for teleoperation is surveyed in three major catagories: (1) hand grip design, (2) control input devices, and (3) control strategies. In the first category, 14 hand grip designs are reviewed and evaluated in light of human factor considerations. In the second, 12 hand controller input devices are evaluated in terms of task performance, configuration and force feedback, controller/slave correspondence, operating volume, operator workload, human limitations, cross coupling, singularities, anthropomorphic characteristics, physical complexity, control/display interference, accuracy, technological base, cost, and reliability. In the third catagory, control strategies, commonly called control modes, are surveyed and evaluated. The report contains a bibliography with 189 select references on hand controller technology.

Formationkeeping for a Pair of Satellites in a Circular Orbit

Abstract: Certain future missions will require that a pair of satellites—ma ster and slave—fly in a fixed relative formation. Active control is required to maintain this formation in spite of disturbances such as aerodynamic drag and solar radiation pressure. This paper develops a closed-loop formationkeeping controller for satellites in any circular orbit using digital optimal control theory. A formationkeepi ng sensor concept, tradeoffs, design, brassboard demonstration, and modeling are discussed. The formationkeeping actuators are assumed to be chemical thrusters on the slave satellite. Two satellites flying in trail 700 m apart in geosynchronou s orbit are used as an example to present closed-loop formationkeeping simulation plots. The results show that formation is maintained to within the ±21 m allocated requirement in the in-track and out-of-plane directions.

Pole assignment by multirate sampled-data output feedback

Abstract: Multirate sampled-data control of a linear time-invariant continuous-time plant is considered. It is shown that, if the plant is controllable and observable, we can always construct a multirate sampled-data gain controller such that the poles of the closed-loop system become a given symmetric set of n complex numbers (n is the dimension of the state vector of the plant). It is also shown that the input sampling rate {N1,...,Np} can be chosen equal to the Kronecker invariants or other "locally minimum controllability indices." This capability gives a new perspective to the application of multirate sampled-data controllers.

Video exercise or game floor controller with position indicating foot pads

Abstract: Operation of a video game or an exercise system utilizing a video display is enhanced by a floor controller utilizing weight sensitive pads that allows an operator to input information into the system by locating his feet in specific portions of the floor controller. The system includes an interface circuit which obtains foot location signals from the floor controller and transmits this information to a system microprocessor which in turn is used to control the video display. The system can also include light segments that are under control of the microprocessor and which are associated with each of the weight sensitive pads.

Stabilization of time-delay systems using finite-dimensional compensators

Abstract: For linear time-invariant systems with one or more noncommensurate time delays, necessary and sufficient conditions are given for the existence of a finite-dimensional stabilizing feedback compensator. In particular, it is shown that a stabilizable time-delay system can always be stabilized using a finite-dimensional compensator. The problem of explicitly constructing finite-dimensional stabilizing compensators is also considered.

Dynamic visual servo control of robots: An adaptive image-based approach

Abstract: Sensory systems, such as computer vision, can be used to measure relative robot end-effector positions to derive feedback signals for control of end-effector positioning. The role of vision as the feedback transducer affects closed-loop dynamics, and a visual feedback control strategy is required. Vision-based robot control research has focused on vision processing issues, while control system design has been limited to ad-hoc strategies. We formalize an analytical approach to dynamic robot visual servo control systems by first casting position-based and image-based strategies into classical feedback control structures. The image-based structure represents a new approach to visual servo control, which uses image features (e.g., image areas, and centroids) as feedback control signals, thus eliminating a complex interpretation step (i.e., interpretation of image features to derive world-space coordinates). Image-based control presents formidable engineering problems for controller design, including coupled and nonlinear dynamics, kinematics, and feedback gains, unknown parameters, and measurement noise and delays. A model reference adaptive controller (MRAC) is designed to satisfy these requirements.

Control theory concepts in production and inventory control

Abstract: The use of efficient production and inventory control systems is of great importance for industry. Therefore this area could be expected to provide many fruitful applications of control theory techniques. However, control theory has traditionally been aimed at applications in other fields, and results have only limited applicability in production and inventory control. This paper gives an overview of earlier research concerning control theory applications in production and inventory control. Areas given special emphasis are those in which control theory seems to have a stronger potential of practical application.

A multiprocessor-based controller for the control of mechanical manipulators

Abstract: A cost-effective architecture for the control of mechanical manipulators based on a functional decomposition of the equations of motion of a manipulator are described. The Lagrange-Euler and the Newton-Euler formulations were considered for this decomposition. The functional decomposition separates the inertial, Coriolis and centrifugal, and gravity terms of the Lagrange-Euler equations of motion. The recursive nature of the Newton-Euler equations of motion lend themselves to being decomposed to the terms used to generate the recursive forward and backward equations. Architectures tuned to the functional flow of the two algorithms were examined. An architecture which meets our design criterion is proposed. The proposed controller architecture can best be described as a macro level pipeline, with parallelism within elements of the pipeline. The pipeline is designed to take maximum benefit of the serial nature of the Newton-Euler equations of motion.

An exothermic continuous stirred tank reactor is feedback equivalent to a linear system

Abstract: This brief paper demonstrates the concept of linear feedback equivalence for an exothermic eontinu-ous stirred tank reactor with first order kinetics. Feedback control is achieved by finding a transformation for the nonlinear system which carries this system into a linear controllable system in Brunovsky canonical form. A linear state feedback controller is then designed which achieves control over a broad range of operating conditions. This example demonstrates how recent developments in nonlinear control theory can be applied to chemical systems without relying on the usual methods of local linearization.

A modified Smith predictor and controller for unstable processes with time delay

Abstract: An integrated design procedure is developed for a modified Smith predictor and associated controller for linear time-delay systems having transfer functions of the form k 1, A exp (—sT)/B, where A and B are monic polynomials in s of degree n — l and n, respectively. A is Hurwitz and B has a single right-half-plane root at s = λ. For l=1,2,3, an augmented PI controller guarantees asymptotic stability for λT less than an l-dependent limit. The procedure for l = 3 is extended to l = 4 with the introduction of derivative action into the controller. Design arguments are on root locus topology, and on Nyquist analysis applied to an auxiliary system.

Optimal digital feedback control systems counting computation time of control laws

Abstract: Since microprocessors are easily obtained, multivariable control theory can be applied to many practical control problems, for example control of robots. However, when the time constant of the plant is short and the dynamic order of the plant is high, the time delay due to the computation time of the control law cannot be neglected. In this paper, the author proposes design methods for linear optimal regulators and linear optimal servosystems in which the delay arising from the computation time of the processors is counted properly. From the theoretical point of view, the results are interesting since all the control laws derived in this paper are obtained using only conventional results of optimal regulator theory.

Theory and application of an extended horizon self‐tuning controller

Abstract: A robust version of the self-tuning regulator is developed. The regulator, which requires relatively little knowledge of system characteristics (estimated order of transfer function polynomials and an upper bound for transportation delays), has been shown to yield stable control and convergence for linear, time-invariant systems. Simulations and practical tests on a large pilot-scale process have shown that the inclusion of a variable forgetting factor and an “extended horizon” control criterion provides the regulator with a sufficient degree of robustness and flexibility to perform well in a nonlinear time-varying environment. The regulator makes use of intuitively easy-to-understand concepts and leaves few degrees of freedom for the potential user. Furthermore, extensive experiments and simulation studies have shown it to be insensitive to choice of initial conditions and dynamic characteristics set by the user.

Computer control of space-borne teleoperators with sensory feedback

Abstract: This paper presents the conceptual design, analysis, synthesis and software organization of an advanced teleoperator control system with sensory feedback. The design requirements for the system are discussed in detail and an implementation strategy is presented. The resulting system features maximum autonomy of the local hand controller and remote manipulator subsystems, along with kinematic and dynamic coordination between these subsystems. The final design emphasizes cooperation and interaction between the human operator and the computers in control of the sensor-based manipulator system. The hardware and software modules being used to implement the system at JPL are described.

Controller for battery charger

Abstract: A controller for a battery charger terminates battery charging operation as a function of a time derivative of measured battery voltage. The controller has analog and digital embodiments. A controller with means for determining a time derivative of the measured battery voltage, determining a change in slope of the time derivative, and using said change in slope as a control function for the battery charger.

Control of tool/workpiece contact force with application to robotic deburring

Abstract: The design and implementation of a microprocessor-based system to control the interaction forces between a five-axis articulated robot and a workpiece is described. The control system worked in parallel with a robot controller by calculating position corrections that allowed forces to be controlled in the desired manner. These corrections were successfully interfaced to the controller's position control loop on an individual-axis level. Stable force-control algorithms were designed in spite of limitations imposed by flexibility in the robot drive train. For multi-degree-of-freedom force control, it is shown that each axis can be considered autonomous, obviating the need for a multivariable approach. Force control was implemented in both edge following and deburring experiments. In edge following, the commanded normal force ranged from 1 to 15 N, while the root mean square (rms) force errors remained constant. Errors increased from 0.5 to 1.5 N rms as tangential speed was increased from 1 to 9 cm s-1. The performance of the force control system during deburring operations was characterized across the full force and speed range of the cutting tools used. The smoothness of cut was shown to be consistent with manual deburring operations in terms of optimal feed and metal removal rates.