Showing papers presented at "American Control Conference in 1986"
18 Jun 1986
TL;DR: In this paper, a new adaptive law motivated by that given in [1] is proposed for the robust adaptive control of plants with unknown parameters, in which output error plays a dual role in the adjustment of the control parameter vector.
Abstract: A new adaptive law motivated by that given in [1] is proposed for the robust adaptive control of plants with unknown parameters. In this adaptive law the output error e l plays a dual role in the adjustment of the control parameter vector. In the ideal case the adaptive system has bounded solutions; in addition the error equations are uniformly asymptotically stable in the large when the reference input is sufficiently persistently exciting. The adaptive system is also shown to be robust under bounded external disturbances. Finally it is shown that, by suitably modifying the adaptive law, the overall system can be made robust in the presence of unmodeled dynamics of the plant.
349 citations
18 Jun 1986
TL;DR: In this article, the authors overview the Linear-Quadratic-Gaussian method with Loop-Tranfer-Recovery (LQG/LTR) and provide a pragmatic exposition, with special emphasis on the step-by-step characteristics for designing multivariable feedback control systems.
Abstract: In this paper we overview the so-called Linear-Quadratic-Gaussian method with Loop-Tranfer-Recovery (LQG/LTR) Our objective is to provide a pragmatic exposition, with special emphasis on the step-by-step characteristics for designing multivariable feedback control systems
210 citations
18 Jun 1986
TL;DR: A simplified form of probabilistic data association logic was developed for real-time multitarget tracking by a microprocessor associated with a radar track-while-scan system, but the weighted-average updating feature of the PDA approach was abandoned in favor of a "nearest-neighbor PDA" method.
Abstract: A simplified form of probabilistic data association (PDA) logic was developed for real-time multitarget tracking by a microprocessor associated with a radar track-while-scan system. A variety of practical problems with the method led to a relatively complex set of algorithms, while certain fundamental shortcomings of the approach still threatened performance due to anomalous behavior in some situations. Ultimately, the weighted-average updating feature of the PDA approach was abandoned in favor of a "nearest-neighbor PDA" method, which utilizes the PDA association probabilities to associate a single measurement with each track.
196 citations
18 Jun 1986
TL;DR: This paper considers the processing functions performed by each DSN node and presents some simulation results on tracking vehicles moving over a road network.
Abstract: A distributed sensor network (DSN) consists of a set of processing nodes collecting data from sensors. When the nodes communicate, each node fuses the information received from other nodes with the local information to update its estimate on the state of the world. Previous papers have dealt with the theoretic algorithms for tracking multiple targets using a DSN. This paper considers the processing functions performed by each DSN node and presents some simulation results on tracking vehicles moving over a road network.
115 citations
18 Jun 1986
TL;DR: In this article, the authors examined the potential use of sliding surfaces for observer design and showed that a particular observer structure including switching terms is shown to have promising properties in the presence of modelling errors and sensor noise.
Abstract: Sliding controllers have recently been shown to feature excellent robustness and performance properties for specific classes of nonlinear tracking problems. This paper examines the potential use of sliding surfaces for observer design. A particular observer structure including switching terms is shown to have promising properties in the presence of modelling errors and sensor noise.
83 citations
18 Jun 1986
TL;DR: In this paper, the problem of obtaining stabilizing memoryless state feedback controllers for a class of uncertain systems described by difference equations (discrete-time systems) is considered, and controllers are presented which yield the desired behavior.
Abstract: We consider the problem of obtaining stabilizing memoryless state feedback controllers for a class of uncertain systems described by difference equations (discrete-time systems). Based on Lyapunov functions, controllers are presented which yield the desired behavior.
83 citations
18 Jun 1986
TL;DR: A parameterized family of two-stage stochastic control problems with nonclassical information patterns, which includes the famous 1968 counterexample of Witsenhausen, is considered, which shows that the parameter region can be partitioned into two regions, in which the optimal solution is linear whereas in the other it is inherently nonlinear.
Abstract: In this paper we consider a parameterized family of two-stage stochastic control problems with nonclassical information patterns, which includes the famous 1968 counterexample of Witsenhausen. We show that the parameter region can be partitioned into two regions, in one of which the optimal solution is linear whereas in the other it is inherently nonlinear. In the latter, the best piecewise-constant solution does not always outperform the best linear solution, whereas a linear plus piecewise-constant policy leads to a uniformly better performance in that region. Extensive numerical computations complement the study.
74 citations
18 Jun 1986
TL;DR: In this article, a nonlinear inverse dynamics model is used to develop a control system that provides satisfactory response over the entire flight envelope for extreme flight conditions such as stalls and spins.
Abstract: Aircraft in extreme flight conditions such as stalls and spins experience nonlinear forces and moments generated from high angles of attack and high angular rates. Flight control systems based upon nonlinear inverse dynamics offer the potential for providing improved levels of safety and performance in these flight conditions over the competing designs developed using linearizing assumptions. Inverse dynamics are generated for specific command variable sets of a 12-state nonlinear aircraft model to develop a control system that provides satisfactory response over the entire flight envelope. Detailed descriptions of the inertial dynamic and aerodynamic models are given, and it is shown how the command variable sets are altered as functions of the system state to add stall prevention features to the system. Simulation results are presented for various mission objectives over a range of flight conditions to confirm the effectiveness of the design.
72 citations
18 Jun 1986
TL;DR: In this paper, a joint torque servo-mechanism has been designed and implemented for a PUMA 500 and a model of the actuator-transmission load system, including flexibility, was developed and verified using both time and frequency domain techniques.
Abstract: Accurate control of joint forces is essential to achieve high performance in advanced assembly and other tasks that involve fine motion, active force control, or high speed operations. Joint force control can be substantially improved by sensory feedback. In this paper we present the design and describe the actual characteristics of a joint torque sensor for a PUMA 500. Using this sensor, a joint torque servo-mechanism has been designed and implemented. A model of the actuator-transmission-load system, including flexibility, was developed and verified using both time and frequency domain techniques. Compensators based on this model were designed and tested. Experimental results obtained from pure torque control and joint motion tracking are presented. These results demonstrate a significant reduction of the effective friction (97%), and substantial improvement in fine motion control.
18 Jun 1986
TL;DR: This paper is an up-to-date tutorial account of the fundamental ideas of DAC theory and a review of the current state of its development.
Abstract: Disturbance-Accommodating Control (DAC) is a relatively new branch of modern control and system theory which addresses the problems of: (i) dynamic modeling of uncertain disturbances which act on systems, and (ii) designing feedback/feedforward controllers which achieve and maintain system performance specifications in the face of such disturbances. This paper is an up-to-date tutorial account of the fundamental ideas of DAC theory and a review of the current state of its development.
18 Jun 1986
TL;DR: In this paper, a two-time scale sliding control approach is applied to the control of robot manipulators with flexible joints in the presence of model uncertainty, where a singular perturbation model is used to decompose the manipulator dynamics into a slow and a fast submodel, using the concept of slow manifold.
Abstract: This paper applies a two-time scale sliding control approach to the control of robot manipulators with flexible joints in the presence of model uncertainty. A singular perturbation model is used to decompose the manipulator dynamics into a slow and a fast submodel, using the concept of slow manifold. A slow sliding controller is designed in order to account for parametric uncertainty on the slow manifold. Further, a fast sliding controller guarantees that the slow manifold is attractive (i.e. all fast system trajectories converge to the slow manifold) despite parametric uncertainty.
18 Jun 1986
TL;DR: In this article, differential equations for process tension control are derived, simplified, and linearized, and the two methods of tension control by means of torque control as well as velocity control of a roller or rewinding roll of material are compared.
Abstract: Because of the transport of strain across rollers in a tension control system, the output from one tension control station is a disturbance to the next station. Tension disturbances are also transmitted upstream if frictional engagement between the web and the roller is inadequate or if velocity control of a driven roller between the spans is imperfect. Differential equations for process tension control are derived, simplified, and linearized. Tension control by means of torque control as well as velocity control of a roller or rewinding roll of material is examined, and the two methods are compared.
18 Jun 1986
TL;DR: Singular value decomposition (SVD) is proving to be a very useful tool in modern linear system theory and is also finding an important role in analysis and design of control systems for those real industrial processes which tend to not be so well behaved as assumed by the theory.
Abstract: Singular Value Decomposition (SVD) is proving to be a very useful tool in modern linear system theory. It is also finding an important role in analysis and design of control systems for those real industrial processes which tend to not be so well behaved as assumed by the theory. This paper will describe how the concepts of SVD analysis can be used to help determine realistic answers to the many practical questions that must be addressed by the control engineer if he or she is going to tackle real multivariable control problems. Such questions as: What is the effect of process design alternatives and operating conditions on the control problem? The paper will also show how SVD can be used to design simple but effective multivariable control systems.
18 Jun 1986
TL;DR: In this paper, a complete solution of the SISO discrete-time problem is provided, which consists of two parts, the calculation of the minimum norm, which is done by solving a linear programming problem, and the construction of the optimal solution (when it exists).
Abstract: The problem under consideration is how to design a compensator to stabilize a given plant, and optimaly reject all persistent bounded disturbances. A complete solution of the SISO discrete-time problem is provided. The solution consists of two parts, the calculation of the minimum norm, which is done by solving a linear programming problem, and the construction of the optimal solution (when it exists), which is done by solving a set of linear equations.
18 Jun 1986
TL;DR: It is shown that a pxm transfer function G(s) with p⩾m can be decomposed as G = (I-νNΔ-1) and G gives a good low order approximation to G in the sense of relative error.
Abstract: It is shown that a pxm transfer function G(s) with p⩾m can be decomposed as G = (I-νNΔN)-1...(I-νr+2Δr+2)-1 (I-νr=1Δr=1)-1GO where Δi are stable all-pass transfer functions, 1=ν1..=νr≫νr=1..≫νN≫0 are the Hankel-singular-values of GW*-1 where G*G=WW* with W stable and minimum phase. Results on the McMillan degree of GΛ:=(I-νiΔi)..(I-νNΔN)G then show that GΛ gives a good low order approximation to G in the sense of relative error.
18 Jun 1986
TL;DR: In this paper, it was shown that the positive realness conditions can be satisfied in almost stable discrete-time multivariable linear systems, namely, systems that can be stabilized via static or dynamic output feedback, including non-minimum phase systems.
Abstract: Recently, it was shown for continuous-time systems, that the positive realness conditions can be satisfied without the need for the prior knowledge about the order and the pole-excess of the controlled plant. Thes results are extended here to discrete-time systems. It is shown that the positive realness conditions can be satisfied in "almost stable" discrete-time multivariable linear systems, namely, systems that can be stabilized via static or dynamic output feedback, including non-minimum phase systems, at the price of bounded rather than vanishing output tracking errors. Satisfaction of the positivity conditions may facilitate implementation of simple adaptive control procedures that maintain robustness in the presence of parasitic dynamics and disturbances.
18 Jun 1986
TL;DR: In this paper, an analysis of camera location and steering errors that can be determined from the row crops is determined by simulating the geometric relationships between the crop canopy and the image plane.
Abstract: The ordered structure of agricultural row crops can provide useful guidance information for tractor control. A description of research for coupling a machine vision system and a solid state camera to derive vehicle guidance parameters for a tractor is presented. Image segmentation is enhanced by optical filtering and controlling light intensity to the image sensor. An analysis of camera location and steering errors that can be determined from the row crops is determined by simulating the geometric relationships between the crop canopy and the image plane.
18 Jun 1986
TL;DR: In this paper, the authors present guidelines for developing a multivariable centralized automatic flight control system (AFCS) for a twin lift helicopter system (TLHS) using singular value ideas to formulate performarce and stability robustness specifications.
Abstract: This paper presents guidelines for developing a multivariable centralized automatic flight control system (AFCS) for a twin lift helicopter system (TLHS). Singular value ideas are used to formulate performarce and stability robustness specifications. A Linear-Quadratic-Gaussian with Loop Transfer Recovery (LQG/LTR) design is obtained and evaluated.
18 Jun 1986
TL;DR: In this article, an exact modal state-space representation for a single-link, flexible remote manipulator with a noncollocated sensor and actuator is derived in detail for a direct model following adaptive controller.
Abstract: An exact modal state-space representation is derived in detail for a single-link, flexible remote manipulator with a noncollocated sensor and actuator. A direct model following adaptive controller is designed to control the torque at the pinned end of the arm so as to command the free end to track a prescribed sinusoidal motion. Conditions that must be satisfied in order for the controller to work are stated. Simulation results to date are discussed along with the potential of the model following adaptive control scheme in robotics and space environments.
18 Jun 1986
TL;DR: The optimal control is obtained from the QP approach, but the QPF which produces near-optimal control, is more robust and easier to implement in real-time applications.
Abstract: Spatial coupling between the control points in a cross-machine profile of a sheet property is a primary concern in cross-machine control problems. The goal of the cross-machine direction (CD) control is to minimize the deviation from a desired profile with certain constraints on the control action. Two approaches, quadratic programming (QP) and quadratic penalty function (QPF), were evaluated for inclusion in a commercial CD control product. The optimal control is obtained from the QP approach, but the QPF which produces near-optimal control, is more robust and easier to implement in real-time applications. A comparison between QP and QPF results is shown by simulated examples. Field test results of the QPF method are also included. The QPF approach is well suited for practical applications and has been successfully incorporated in over 40 commercial installations.
18 Jun 1986
TL;DR: In this article, the authors compare the computed-torque control scheme with the feed-forward dynamics compensation scheme, which compensates for the manipulator dynamics in the feedforward path.
Abstract: This paper presents the experimental results of the real-time performance of model-based control algorithms. We compare the computed-torque control scheme with the feedforward dynamics compensation scheme. The feedforward scheme compensates for the manipulator dynamics in the feedforward path while the computed-torque scheme uses the dynamics in the feedback loop for linearization and decoupling. The manipulator control schemes have been implemented on the CMU DD Arm II with a sampling period of 2 ms.
18 Jun 1986
TL;DR: In this article, a recursive method was developed for the solution of coupled algebraic Riccati equations and corresponding linear Nash strategies of weakly interconnected systems, and it was shown that each iteration step improves the accuracy by an order of magnitude, i.e., the accuracy of O(?k), where is a coupling parameter) can be obtained by doing only k-l iterations.
Abstract: The recursive method was developed for the solution of coupled algebraic Riccati equations and corresponding linear Nash strategies of weakly interconnected systems. It is shown that each iteration step improves the accuracy by an order of magnitude, i.e., the accuracy of O(?k), (where ? is a coupling parameter) can be obtained by doing only k-l iterations. On the other hand, only low-order systems are involved in algebraic computations, and no analicity requirements are imposed on the system coefficients.
18 Jun 1986
TL;DR: The architecture of YAMS (Yet Another Manufacturing System), a factory control system for flexible manufacturing currently under development at the Industrial Technology Institute, is described.
Abstract: This paper describes the architecture of YAMS (Yet Another Manufacturing System), a factory control system for flexible manufacturing currently under development at the Industrial Technology Institute. We summarize ? some objectives such a system must satisfy, and ? its overall architecture. Then we focus on three details of the overall system, ? its scheduling strategies, ? strategies for moving tools and materials around the factory, and ? the bottom elements in the hierarchy, the individual workstations.
01 Jan 1986
01 Jan 1986
18 Jun 1986
TL;DR: In this paper, the main theorem of QFT on which the claims are based is shown to be unjustified and counterexamples are given for QFT's main theorem.
Abstract: QFT, a theory developed by Horowitz [H3], is claimed by its advocates to provide a complete and general treatment of feedback design for highly uncertain multi-input-output (MIMO) systems. This paper reviews QFT and shows that while the philosophy behind QFT is attractive, the claims for the theory are unjustified. In particular, counterexamples are given for the main theorem of QFT on which the claims are based. This is in spite of the severe assumptions (no rhp zeros and fixed relative degree) that QFT requires on the plant model.
18 Jun 1986
TL;DR: The expert planner incorporates the knowledge of a control system designer in selecting and applying mathematical algorithms from several branches of control theory such as Kalman filter design, proportional/integral/ derivative control, and optimal state feedback.
Abstract: This paper describes the development of an expert planning framework for design of control systems. The expert planner incorporates the knowledge of a control system designer in selecting and applying mathematical algorithms from several branches of control theory such as Kalman filter design, proportional/integral/ derivative control, and optimal state feedback. The framework has been developed directly in Lisp rather than using any of the available domain-independent expert system frameworks. The planning is done at two levels: a high level that uses general rules about control system design and a low level that uses rules about the use of a computer aided control system design (CACSD) package. The system has been implemented and demonstrated on a Xerox 1100 Lisp workstation controlling a CACSD package running on a VAX 11/780, designing a servo (command tracking) control system for aircraft.
18 Jun 1986
TL;DR: In this article, the authors developed a methodology for the design of autopilots for bank-to-turn missiles, which accommodates the gyroscopic and coriolis cross-coupling between the pitch and the yaw axes that result due to the high roll rates that can be present.
Abstract: The state-space techniques of modern control theory are used to develop a methodology for the design of autopilots for bank-to-turn missiles. The methodology accommodates the gyroscopic and coriolis cross-coupling between the pitch and the yaw axes that result due to the high roll rates that can be present. The design uses the assumption that the roll rate is constant, but not zero, and results in an autopilot structure in which there are cross-couplings between the pitch and yaw channels that are dependent on the roll rate. The autopilot gains are also scheduled as functions of the dynamic pressure. A reduced-order extended Kalman filter, with fixed gains, is used to estimate the actuator states and the commanded acceleration. The performance of an autopilot designed by this methodology was evaluated in a six-degree of freedom simulation using the dynamics of a typical high-performance tactical missile. Excellent performance was obtained in teres of low miss distance and small side-slip.