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Showing papers presented at "American Control Conference in 1983"


Journal ArticleDOI
22 Jun 1983
TL;DR: In this paper, the authors present a methodology of feedback control to achieve accurate tracking for a class of nonlinear time-varying systems in the presence of disturbances and parameter variations.
Abstract: A methodology is presented of feedback control to achieve accurate tracking for a class of nonlinear time-varying systems in the presence of disturbances and parameter variations. The methodology uses in its idealized form piecewise continuous feedback control laws, resulting in the state trajectory `sliding' along a discontinuity surface in the state space. The idealized form of the methodology results in perfect tracking of the required signals; however certain non-idealities associated with its implementation cause the trajectory to 'chatter' along the sliding surface resulting in the generation of an undesirable high-frequency component which may excite high-frequency unmodelled dynamics of the control systems. To rectify this situation, it is shown how continuous control laws which approximate the discontinuous control law may be used to obtain disturbance and parameter variation insensitive tracking. At the same time, the continuous control laws decrease the extent of unwanted high-frequency signals.

1,636 citations


Proceedings ArticleDOI
22 Jun 1983
TL;DR: In this article, the canonical variate method is extended to approximately solve this problem and give a near optimal reduced-order state space model, which is related to the Hankel norm approximation method.
Abstract: Very general reduced order filtering and modeling problems are phased in terms of choosing a state based upon past information to optimally predict the future as measured by a quadratic prediction error criterion. The canonical variate method is extended to approximately solve this problem and give a near optimal reduced-order state space model. The approach is related to the Hankel norm approximation method. The central step in the computation involves a singular value decomposition which is numerically very accurate and stable. An application to reduced-order modeling of transfer functions for stream flow dynamics is given.

362 citations


Proceedings ArticleDOI
22 Jun 1983
TL;DR: In this paper, the authors present an optimal control policy which results in minimum-time motion for a robotic manipulator along any predetermined path in a 3D space, which does not interfere with the manipulator's industrial utility.
Abstract: High speed motions and increased productivity are linked in the industrial applications of many robotic manipulators, yet the speeds which can be achieved by a manipulator during a given task are limited by a number of factors. The dynamic properties of a manipulator and its actuator limitations and characteristics are probably the most important factors. This paper presents an optimal control policy which results in minimum-time motion for a robotic manipulator along any predetermined path in three dimensional space. The technique permits the manipulator user to specify completely the path of the arm; therefore the method does not interfere with the manipulator's industrial utility. The method accounts for the nonlinear dynamics of articulated manipulators with rigid links and limitations on the actuators. These limitations may be arbitrary functions of the manipulator joint positions and velocities. The algorithm developed for obtaining the optimal control is computationally simple, and it does not require the extensive iterations often found in optimal control strategies. Examples are presented of the method's application.

156 citations


Proceedings ArticleDOI
01 Jan 1983

54 citations


Proceedings ArticleDOI
James Taylor1
22 Jun 1983
TL;DR: In this paper, the authors provide an overview of one school of thought in this area, typified by the following key ideas: 1. Quasilinear models of the nonlinear system that account for the operating range of system variables must be more realistic than conventional linear models. 2. The designer should be led to a nonlinear controller design if and only if it is really required.
Abstract: Recent research in the area of describing function approaches (both random-input and sinusoidal-input) has laid the foundation for a systematic approach to designing controllers for nonlinear plants. This paper provides an overview of one school of thought in this area, typified by the following key ideas: 1. Quasilinear models of the nonlinear system that account for the operating range of system variables must be more realistic than conventional linear models. 2. A staged design approach that applies more power to "difficult" nonlinear plants than to "easy" ones is more sensible than a single design method. 3. The designer should be led to a nonlinear controller design if and only if it is really required. These points will be developed, illustrated and justified in this presentation.

53 citations


Proceedings ArticleDOI
22 Jun 1983
TL;DR: An `asymptotic recovery' design procedure is proposed for square discrete-time, linear, time-invariant multivariable systems and indications are given of conditions under which the procedure can be expected to work well.
Abstract: An `asymptotic recovery' design procedure is proposed for square discrete-time, linear,-time-invariant multivariable systems Both the cases of negligible processing time (compared with the sampling interval) and of significant processing time are discussed Indications are given of conditions under which the procedure can be expected to work well, although a complete theoretical justification is not yet available An example of the use of the procedure is given

51 citations


Proceedings ArticleDOI
22 Jun 1983
TL;DR: In this article, a fundamental time-scaling property of manipulator dynamics has been identified that allows modification of movement speed without complete dynamics recalculation, and it can be determined whether a planned trajectory is dynamically realizable given actuator torque limits, and if not, how to modify the trajectory to bring it within dynamic and actuating constraints.
Abstract: A fundamental time-scaling property of manipulator dynamics has been identified that allows modification of movement speed without complete dynamics recalculation. By exploiting this property, it can be determined whether a planned trajectory is dynamically realizable given actuator torque limits, and if not, how to modify the trajectory to bring it within dynamic and actuating constraints.

47 citations


Journal ArticleDOI
22 Jun 1983
TL;DR: In this article, a microcomputer-based solar tracking and control system (TACS) is proposed to maintain the peak power position of a photovoltaic (PV) array by adjusting the load on the array for maximum efficiency and changing the position of the array relative to the sun.
Abstract: This paper details the design, development, and evaluation of a microcomputer-based solar tracking and control system (TACS) capable of maintaining the peak power position of a photovoltaic (PV) array by adjusting the load on the array for maximum efficiency and changing the position of the array relative to the sun. At large PV array system installations, inverters are used to convert the dc electrical output to ac for power grid compatibility. Adjustment of the inverter or load for maximum array output is one function performed by the tracking and control system. Another important function of the system is the tracking of the sun, often a necessity for concentrating arrays. The TACS also minimizes several other problems associated with conventional shadow-band sun trackers such as their susceptibility to dust and dirt that may cause drift in solar alignment. It also minimizes effects of structural warpage or sag to which large arrays may be subject during the day. Array positioning is controlled by a single-board computer used with a specially designed input/output board. An orderly method of stepped movements and the finding of new peak power points is implemented. This maximum power positioning concept was tested using a small two-axis tracking concentrator array. A real-time profile of the TACS activity was produced and the data analysis shows a deviation in maximum power of less than 1% during the day after accounting for other variations.

43 citations


Proceedings ArticleDOI
22 Jun 1983
TL;DR: In this paper, symbolic equations defining the effective joint inertias and gravity loading torques for the Unimate PUMA manipulator are derived, and these equations define the inertias to within 10% and the gravity torques to within 1%.
Abstract: Symbolic equations defining the effective joint inertias and gravity loading torques for the Unimate PUMA manipulator are derived. These equations define the inertias to within 10% and the gravity torques to within 1%. The equations are very simple and are suitable for on-line computation. They also give insight into the general control problem.

36 citations


Proceedings ArticleDOI
22 Jun 1983
TL;DR: It is discovered that in general the agents have to remember some of the past conditional probabilities and may even have to request additional information from other agents when reconstructing the conditional probability of the random state.
Abstract: In this paper, we consider the distributed estimation problem by a set of agents connected by an arbitrary communication network. Specifically, the problem of reconstructing the conditional probability of the random state using the conditional probabilities communicated from other agents is discussed. It is discovered that in general the agents have to remember some of the past conditional probabilities and may even have to request additional informtion. A method for generating the fusion algorithm for each agent based on the network structure is presented and applied to some examples. The results are applicable to both dynamic and static states.

33 citations


Proceedings ArticleDOI
22 Jun 1983
TL;DR: The problem of designing a feedback compensator to minimize a weighted L∞ norm of the sensitivity function of a MIMO linear time invariant system is considered and is solved by establishing its equivalence to the different but related problem of multivariable zeroeth order optimal Hankel approximation.
Abstract: The problem of designing a feedback compensator to minimize a weighted L∞ norm of the sensitivity function of a MIMO linear time invariant system is considered. The problem is solved by establishing its equivalence to the different but related problem of multivariable zeroeth order optimal Hankel approximation solved recently by Kung and Lin.

Proceedings ArticleDOI
22 Jun 1983
TL;DR: In this article, a computer-based controller combines supervisory functions and adaptive control algorithms in a hierarchical structure for the simultaneous control of cardiac output and blood pressure by multiple drug infusion.
Abstract: Although various control schemes have been successful in controlling mean arterial blood pressure by infusing a vasoactive drug, the simultaneous control of cardiac output and blood pressure by multiple drug infusion has to-date received little attention. To this effect, this paper describes the design of an automated multiple drug delivery system. The proposed computer-based controller combines supervisory functions and adaptive control algorithms in a hierarchical structure. Given a set of measured cardiovascular parameters, the supervisor determines the underlying disordered physiology and initiates the relevant control mode. Each mode is a set of allowable drug types, set-point commands and single or multiple feedback loops. The feedback control laws are adapted to each patient's drug response. The adaptive scheme used here is based on pole-placement self-tuning algorithms. This design method accomodates constraints on maximum drug infusion and physiological response rates and, can deal with unknown varying time delays. Adaptive control appears to be better suited for this application because of the wide range of drug sensitivities among patients, time variations in parameters, unknown drug interaction and physiological distrubances.

Proceedings ArticleDOI
01 Jan 1983

Proceedings ArticleDOI
22 Jun 1983
TL;DR: It is shown by simulation that for certain geometries and loading the proposed nonlinear adaptive scheme can produce considerable improvement in performance over the linear scheme proposed in earlier investigations.
Abstract: This paper considers the problem of adaptively controlling the nonlinear dynamics associated with connected mechanical links such as those which form robotic manipulators. By first considering a single link, linear and nonlinear adaptive control methodologies are compared. It is shown by simulation that for certain geometries and loading the proposed nonlinear adaptive scheme can produce considerable improvement in performance over the linear scheme proposed in earlier investigations. The case of a two degree of freedom, two link, planar arm is then considered in detail. A discrete time model matching adaptive controller is then derived using a specific descretization of the continuous time nonlinear dynamics. Conditions which guarantee global stability of the control scheme are derived for the case of controlling the descretized model, and simulations are presented for the case of controlling the actual continuous time dynamics.

Proceedings ArticleDOI
22 Jun 1983
TL;DR: In this article, the Selective Modal Analysis (SMA) framework is proposed for analyzing and reducing the large, linear, time-invariant models that arise in the study of dynamic stability in power systems.
Abstract: The research described in this work has been aimed at the development and application of a promising new framework for analyzing and reducing the large, linear, time-invariant models that arise in the study of dynamic stability in power systems. This framework has been termed Selective Modal Analysis or SMA. The results demonstrate that SMA goes beyond traditional modal analysis methods in ways that appear crucial to eventual practical use of modal methods in both off-line and on-line applications.

Proceedings ArticleDOI
22 Jun 1983
TL;DR: A lightweight arm mechanism for the direct-drive robots by replacing the serial link mechanism with a four-bar-link mechanism in order to avoid the mounting of heavy motors at the serial links and high performance brushless motors have been developed so that large torques can be obtained with relatively small power dissipation.
Abstract: Direct drive is an ideal drive method which has excellent features including no backlash, low friction, and high mechanical stiffness. Applying the direct drive method to robot arms, however, leads to an impractical design because of the following two drawbacks. One is that a direct-drive arm tends to be heavier than a conventional arm with transmission mechanisms; because the motors of direct-drive arm are located at each joint of the arm the weight of each motor is a load to the previous motors down the serial linkage of the arm. Another problem is insufficient drive torques due to the elimination of gears which amplify the motor torques. This paper describes a lightweight arm mechanism for the direct-drive robots. The major improvements are: (1) the serial link mechanism is replaced by a four-bar-link mechanism in order to avoid the mounting of heavy motors at the serial links, (2) high performance brushless motors have been developed so that large torques can be obtained with relatively small power dissipation. Throughout the basic analysis and experiments, the arm which has been developed is evaluated in terms of efficiency, load capacity and dynamic response.

Proceedings ArticleDOI
22 Jun 1983
TL;DR: In this article, approximation techniques for use in numerical schemes for estimating spatially varying coefficients in continuum models such as those for Euler-Bernoulli beams are discussed, based on quintic spline state approximations and cubic spline parameter approximation.
Abstract: We discuss approximation techniques for use in numerical schemes for estimating spatially varying coefficients in continuum models such as those for Euler-Bernoulli beams. The techniques are based on quintic spline state approximations and cubic spline parameter approximations. Both theoretical and numerical results are presented.


Proceedings ArticleDOI
22 Jun 1983
TL;DR: It is shown that the problems of multitarget tracking in surveillance theory, Markov chain-driven systems, estimation under uncertain observations, maneuvering target tracking and system failure detection are special cases of this general formulation of an event-driven, linear stochastic system model.
Abstract: In many practical situations, dynamic systems are subjected to abrupt structural and parametric changes at random instants of time. A general mathematical framework is presented for classifying the existing state estimation and hypothesis-testing problems arising in systems subjected to random structural and parametric disturbances. The mathematical approach is based on an event-driven, linear stochastic system model comprising a hybrid (i.e., continuous and discrete) state space. It is shown that the problems of multitarget tracking in surveillance theory, Markov chain-driven systems, estimation under uncertain observations, maneuvering target tracking and system failure detection are special cases of this general formulation.

Proceedings ArticleDOI
22 Jun 1983
TL;DR: In this paper, a procedure for the design of preccapensators for linear multivariable continuous-time systems based on reduced-order plant models is described, and the closed-loop stability of the full order plant and compensator can then be deduced from this approximation error and a robust stability result.
Abstract: A procedure for the design of preccapensators for linear multivariable continuous-time systems based on reduced-order plant models is described. The reducedorder model is obtained via an optimal Hankel-norn approximation method, whose approximation error can be accurately predicted. The closed-loop stability of the full-order plant and compensator can then be deduced from this approximation error and a robust stability result.

Proceedings ArticleDOI
Chi-Haur Wu1
22 Jun 1983
TL;DR: In this paper, a linear analytical model between the six Cartesian errors and the four independent kinds of kinematic errors has been developed and can be used as a guide to minimize the open-loop kinematics errors of the robot manipulator.
Abstract: The correct relationship between two connective joint coordinates of a robot manipulator is defined by four link parameters; one is the joint variable and the others are geomatrical values. Also, the basis for all open-loop manipulator control is the relationship between the Cartesian coordinates of the end effector and the joint coordinates. Hence, the fidelity of the Cartesian position and orientation of the end-effector to the real world depends on the accuracy of the four link parameters of each joint. In this paper, a linear analytical model between the six Cartesian errors and the four independent kinds of kinematic errors has been developed. Based on this model, the Cartesian error envelopes due to any combination of four kinds of kinematic errors can be uniquely determined. From the point of view of design, this error model can be used as a guide to minimize the open-loop kinematic errors of the robot manipulator. Finally, a new calibration technique based on this model has also been developed which can be used to correct the kinematic errors of the robot manipulator.

Proceedings ArticleDOI
22 Jun 1983
TL;DR: The kinematic and dynamic analysis of an n-link manipulator with flexible members is presented, where the deformation of a link from its rigid body position is modeled by a homogeneous transformation.
Abstract: This paper presents the kinematic and dynamic analysis of an n-link manipulator with flexible members. The deformation of a link from its rigid body position is modeled by a homogeneous transformation. The dynamic equations are obtained using an Euler-Lagrange formulation. These equations are compared to those describing a rigid link mechanism.

Proceedings ArticleDOI
22 Jun 1983
TL;DR: In this paper, the authors describe an analysis tool for the interactive design of control systems for manipulators and similar electro-mechanical systems amenable to representation as structures in a topological chain.
Abstract: This paper describes the development of an analysis tool for the interactive design of control systems for manipulators and similar electro-mechanical systems amenable to representation as structures in a topological chain. The chain consists of a series of elastic bodies subject to small deformations and arbitrary displacements. The bodies are connected by hinges which permit kinematic constraints, control, or relative motion with six degrees of freedom. The equations of motion for the chain configuration are derived via Kane's method, extended for application to interconnected flexible bodies with time-varying boundary conditions. A corresponding set of modal coordinates has been selected. The motion equations are imbedded within a simulation that transforms the vector-dyadic equations into scalar form for numerical integration. The simulation also includes a linear, time-invariant controller specified in transfer function format and a set of sensors and actuators that interface between the structure and controller. The simulation is driven by an interactive set-up program resulting in an easy-to-use analysis tool.

Proceedings ArticleDOI
22 Jun 1983
TL;DR: The use of nonlinear simulation, discrete identification and in-vehicle control synthesis provides a framework for systematic control system design tradeoffs.
Abstract: The automotive engine idle-speed regulation problem is one which lends itself to the application of a variety of control theory techniques. The process is distributed and nonlinear with a combination of continuous and discrete elements. There are known and unknown disturbances with both periodic and random process noise. The process is time varying over both short and long time intervals. This paper discusses the application of modern and classical control techniques to the idle speed regulation problem. The use of nonlinear simulation, discrete identification and in-vehicle control synthesis provides a framework for systematic control system design tradeoffs.

Proceedings ArticleDOI
22 Jun 1983
TL;DR: An algebraic theory for analysis and design of linear multivariable feedback systems, which is sufficiently general to apply to lumped and distributed systems as well as continuous or discrete time is presented.
Abstract: This paper presents an algebraic theory for analysis and design of linear multivariable feedback systems, which is sufficiently general to apply to lumped and distributed systems as well as continuous or discrete time. By use of a controller with two vector inputs, results are obtained which give global parametrizations of all I/O and D/O maps achievable for a given plant by a stabilizing compensator. Also given are conditions sufficient for the asymptotic tracking of a class of inputs. Sufficient conditions for the robustness of the above results are also presented. In the special case of lumped systems it is shown that the design theory can be simplified to involve manipulations of polynomial matrices only.

Proceedings ArticleDOI
22 Jun 1983
TL;DR: In this article, the primal-dual approach is extended to nonconvex problems, and a new Lagrangian function is proposed to preserve separability of the problem.
Abstract: The primal-dual approach is quite effective in decomposing a convex separable optimization problem into several subproblems of smaller sizes. In this paper, we present a new technique which extends the primal-dual approach to nonconvex problems. Since a straightforward application of the so-called multiplier method destroys separability, a new Lagrangian function is proposed here which preserves separability. Based on this new function we develop a new iterative method for finding an optimal solution to the problem and show that the method is locally convergent to an optimal solution. Furthermore, the effect of certain parameters on the ratio of convergence is investigated and a simple example is given to illustrate the proposed approach.

Proceedings ArticleDOI
22 Jun 1983
TL;DR: In this paper, a method for obtaining stable partial Pade approximation reduced order models is described, which permits the determination of the effect of changes in the coefficients in the partial pade approximation on the poles of the reduced order transfer function by means of standard root locus plots.
Abstract: While the Pade approximation can often be used to produce good reduced order transfer functions, the method suffers from the disadvantage that a stable reduced order model is not always obtained for an original model that is stable. A method is described for obtaining stable partial Pade approximation reduced order models. The method permits the determination of the effect of changes in the coefficients in the partial Pade approximation on the poles of the reduced order transfer function by means of standard root locus plots.

Proceedings ArticleDOI
22 Jun 1983
TL;DR: The study indicates that a digital control law which accommodates computation delay can stabilize the wing with reasonable rms performance and adequate stability margins.
Abstract: A method for synthesizing digital active flutter suppression controllers using the concept of optimal output feedback is presented. A recently developed convergent algorithm is employed to determine constrained control law parameters that minimize an infinite-time discrete quadratic performance index. Low-order compensator dynamics are included in the control law and the compensator parameters are computed along with the output feedback gain as part of the optimization process. An input noise adjustment procedure is used to improve the stability margins of the digital active flutter controller. Results from investigations into sample rate variation, prefilter pole variation, and effects of varying flight conditions are discussed. The study indicates that a digital control law which accommodates computation delay can stabilize the wing with reasonable rms performance and adequate stability margins.

Proceedings ArticleDOI
22 Jun 1983
TL;DR: The issues of robust failure detection is considered and an alternative measure of reliability for a redundancy relation is discussed.
Abstract: The issues of robust failure detection is considered. The problem of robust failure detection is concerned with generating signals which are maximally sensitive to some effects (failures) and minimally sensitive to others (model errors). An alternative measure of reliability for a redundancy relation is discussed.

Proceedings ArticleDOI
22 Jun 1983
TL;DR: A single loop adaptive controller algorithm has been successfully applied to the control of an eight plate distillation column separating a mixture of methanol and water.
Abstract: A single loop adaptive controller algorithm has been successfully applied to the control of an eight plate distillation column separating a mixture of methanol and water. Computer control of loops controlling overhead and bottom composition has been implemented using a NOVA 3/12 minicomputer with 32k RAM and a disk operating system. The control algorithm is based on pole-zero placement.