Showing papers on "Control theory published in 1993"
TL;DR: In this paper, the three principal control effects found in present controllers are examined and practical names and units of measurement are proposed for each effect and corresponding units for a classification of industrial processes in terms of two principal characteristics affecting their controllability.
Abstract: In this paper, the three principal control effects found in present controllers are examined and practical names and units of measurement are proposed for each effect. Corresponding units are proposed for a classification of industrial processes in terms of the two principal characteristics affecting their controllability. Formulas are given which enable the controller settings to be determined from the experimental or calculated values of the lag and unit reaction rate of the process to be controlled
5,412 citations
Book•
01 Jan 1993
TL;DR: A guide to the fundamental mathematics of neurocomputing, a review of neural network models and an analysis of their associated algorithms, and state-of-the-art procedures to solve optimization problems are explained.
Abstract: From the Publisher:
Artificial neural networks can be employed to solve a wide spectrum of problems in optimization, parallel computing, matrix algebra and signal processing. Taking a computational approach, this book explains how ANNs provide solutions in real time, and allow the visualization and development of new techniques and architectures. Features include a guide to the fundamental mathematics of neurocomputing, a review of neural network models and an analysis of their associated algorithms, and state-of-the-art procedures to solve optimization problems. Computer simulation programs MATLAB, TUTSIM and SPICE illustrate the validity and performance of the algorithms and architectures described. The authors encourage the reader to be creative in visualizing new approaches and detail how other specialized computer programs can evaluate performance. Each chapter concludes with a short bibliography. Illustrative worked examples, questions and problems assist self study. The authors' self-contained approach will appeal to a wide range of readers, including professional engineers working in computing, optimization, operational research, systems identification and control theory. Undergraduate and postgraduate students in computer science, electrical and electronic engineering will also find this text invaluable. In particular, the text will be ideal to supplement courses in circuit analysis and design, adaptive systems, control systems, signal processing and parallel computing.
1,522 citations
TL;DR: A direct adaptive fuzzy controller that does not require an accurate mathematical model of the system under control, is capable of incorporating fuzzy if-then control rules directly into the controllers, and guarantees the global stability of the resulting closed-loop system in the sense that all signals involved are uniformly bounded is developed.
Abstract: A direct adaptive fuzzy controller that does not require an accurate mathematical model of the system under control, is capable of incorporating fuzzy if-then control rules directly into the controllers, and guarantees the global stability of the resulting closed-loop system in the sense that all signals involved are uniformly bounded is developed. The specific formula for the bounds is provided, so that controller designers can determine the bounds based on their requirements. The direct adaptive fuzzy controller is used to regulate an unstable system to the origin and to control the Duffing chaotic system to track a trajectory. The simulation results show that the controller worked without using any fuzzy control rules, and that after fuzzy control rules were incorporated the adaptation speed became much faster. It is shown explicitly how the supervisory control forces the state to remain within the constraint set and how the adaptive fuzzy controller learns to regain control. >
1,488 citations
Book•
01 Aug 1993
TL;DR: This paper presents a meta-modelling framework for computer-aided design of the power-electronic controller and some examples show how this approach can be applied to motor design.
Abstract: Introduction 1. Energy conversion principles 2. Motor design 3. Dynamic operation 4. Computer-aided design 5. The power-electronic controller 6. Control strategies 7. Losses and cooling 8. Applications 9. Example design 10. Tests and measurements References Index
1,263 citations
TL;DR: A torque sensorless control for a multi-degree-of-freedom manipulator and several experimental results are shown to confirm the validity of the proposed sensorless force controller.
Abstract: A torque sensorless control for a multi-degree-of-freedom manipulator is described. In the method, two disturbance observers are applied to each joint. One is used to realize a robust motion controller. The other is used to obtain a sensorless torque controller. A robust acceleration controller based on the disturbance observer is shown. To obtain the sensorless torque control, it is necessary to calculate the reaction torque when the mechanical system performs a force task. The calculation method for the reaction torque is explained. Then the method is expanded to workspace force control in the multi-degree-of-freedom manipulator. Several experimental results are shown to confirm the validity of the proposed sensorless force controller. >
1,150 citations
TL;DR: An infinite horizon controller that allows incorporation of input and state constraints in a receding horizon feedback strategy is developed and guarantees nominal closed-loop stability for all choices of the tuning parameters in the control law.
Abstract: An infinite horizon controller that allows incorporation of input and state constraints in a receding horizon feedback strategy is developed. For both stable and unstable linear plants, feasibility of the contraints guarantees nominal closed-loop stability for all choices of the tuning parameters in the control law. The constraints' feasibility can be checked efficiently with a linear program. It is always possible to remove state constraints in the early portion of the infinite horizon to make them feasible. The controller's implementation requires only the solution of finite-dimensional quadratic programs. >
1,046 citations
01 Feb 1993
TL;DR: The authors present algorithms for robotic (eye-in-hand configuration) real-time visual tracking of arbitrary 3D objects traveling at unknown velocities in a 2D space (depth is given as known).
Abstract: The authors present algorithms for robotic (eye-in-hand configuration) real-time visual tracking of arbitrary 3D objects traveling at unknown velocities in a 2D space (depth is given as known). Visual tracking is formulated as a problem of combining control with computer vision. A mathematical formulation of the control problem that includes information from a novel feedback vision sensor and represents everything with respect to the camera frame is presented. The sum-of-squared differences (SSD) optical flow is used to compute the vector of discrete displacements each instant of time. These displacements can be fed either directly to a PI (proportional-integral) controller or to a pole assignment controller or discrete steady-state Kalman filter. In the latter case, the Kalman filter calculates the estimated values of the system's states and the exogenous disturbances, and a discrete LQG (linear-quadratic Gaussian) controller computes the desired motion of the robotic system. The outputs of the controllers are sent to the Cartesian robotic controller. Performance results are presented. >
613 citations
15 Dec 1993
TL;DR: In this paper, a controller called a "supervisor" switches into feedback with a SISO process, a sequence of linear positioning or set-point controllers from a family of /spl Fscr//sub C/ of candidate controllers, so as to cause the output of the process to approach and track a constant reference input.
Abstract: This paper describes a simple, 'high-level' controller called a 'supervisor' which is capable of switching into feedback with a SISO process, a sequence of linear positioning or set-point controllers from a family /spl Fscr//sub C/ of candidate controllers, so as to cause the output of the process to approach and track a constant reference input. The process is assumed to be modeled by a SISO linear system whose transfer function is in the union of a number of subclasses, each subclass being small enough so that one of the controllers in /spl Fscr//sub C/ would solve the positioning problem, were the process's transfer function to be one of the subclasses members. The supervisor decides which controller to put in feedback with the process, not by an exhaustive search-i.e., by experimentally evaluating each and every candidate controller's performance by briefly applying it to the process-but rather by continuously comparing in real time suitably defined 'output estimation errors' generated by the candidate controllers, whether or not they are in feedback with the process. It is shown that under reasonably mild conditions, the supervisor can successfully perform its function in spite of modeling errors, provided the errors are sufficiently small. It is also shown that the supervisor will invariably correctly classify the process in finite time, so long as the reference input is nonzero and the "dc gains" of the "nominal" candidate process model transfer functions are distinct. >
451 citations
TL;DR: The basic question of nonlinear H/sup infinity / control theory is to decide, for a given two-port system, when feedback that makes the full system dissipative and internally stable exists.
Abstract: The basic question of nonlinear H/sup infinity / control theory is to decide, for a given two-port system, when feedback that makes the full system dissipative and internally stable exists. This problem can also be viewed as a question about circuits, and, after translation, also has a game-theoretic statement. Several necessary conditions for solutions to exist are presented, and sufficient conditions for a certain construction to lead to a solution are given. >
419 citations
01 Dec 1993
TL;DR: A key point in this design strategy is a fine tuning of the controller and observer structure to each other, which provides solutions to the output-feedback robot control problem that are conceptually simple and easily implementable in industrial robot applications.
Abstract: Passivity-based control methods for robots, which achieve the control objective by reshaping the robot system's natural energy via state feedback, have, from a practical point of view, some very attractive properties. However, the poor quality of velocity measurements may significantly deteriorate the control performance of these methods. In this paper the authors propose a design strategy that utilizes the passivity concept in order to develop combined controller-observer systems for robot motion control using position measurements only. To this end, first a desired energy function for the closed-loop system is introduced, and next the controller-observer combination is constructed such that the closed-loop system matches this energy function, whereas damping is included in the controller- observer system to assure asymptotic stability of the closed-loop system. A key point in this design strategy is a fine tuning of the controller and observer structure to each other, which provides solutions to the output-feedback robot control problem that are conceptually simple and easily implementable in industrial robot applications. Experimental tests on a two-DOF manipulator system illustrate that the proposed controller-observer systems enable the achievement of higher performance levels compared to the frequently used practice of numerical position differentiation for obtaining a velocity estimate. >
398 citations
TL;DR: In this article, a quasi-LPV (quasilinear parameter varying) state transformation is used to bring a longitudinal autopilot to a quasilevel form via a state transformation.
Abstract: This paper presents a gain-scheduled design for a missile longitudinal autopilot. The gain-scheduled design is novel in that it does not involve linearizations about trim conditions of the missile dynamics. Rather, the missile dynamics are brought to a quasilinear parameter varying (LPV) form via a state transformation. An LPV system is defined as a linear system whose dynamics depend on an exogenous variable whose values are unknown a priori but can be measured upon system operation. In this case, the variable is the angle of attack. This is actually an endogenous variable, hence the expression "quasi-LPV." Once in a quasi-LPV form, a robust controller using H synthesis is designed to achieve angle-of-attack control via fin deflections. The final design is an inner/outerloop structure, with angle-of-attack control being the inner loop and normal acceleration control being the outer loop.
TL;DR: An attempt is made to indicate how practically viable controllers can be designed using neural networks, based on results in nonlinear control theory, to complement the theoretical discussions.
Abstract: An attempt is made to indicate how practically viable controllers can be designed using neural networks, based on results in nonlinear control theory. The problem of stabilization of a dynamical system around an equilibrium point when the state of the system is accessible is considered. Simulation results are included to complement the theoretical discussions. >
TL;DR: In this paper, a new controller for the generator excitation system is described that uses a combination of feedback linearizing and the observation decoupled state space, which can be realistically implemented using only local measurements, and whose performance is consistent with respect to changes in network configuration, loading and power transfer conditions.
Abstract: A new controller for the generator excitation system is described that uses a combination of feedback linearizing and the observation decoupled state space. This creates a controller that can be realistically implemented using only local measurements, and whose performance is consistent with respect to changes in network configuration, loading and power transfer conditions. The control differs in this respect from linear constant-gain controllers such as power system stabilizers, whose characteristics can vary significantly with changes in operating conditions. The design is well-suited to a multimachine setting, in that it is not based on an infinite-bus approximation. Simulations were performed on a 38-bus reduced modelof the Northeast Power Coordinating Council system and benchmarked against simulations in which automatic voltage regulators with power system stabilizers were substituted in place of the nonlinear controls. >
TL;DR: In this article, the authors consider some basic properties of nonsmooth and set-valued mappings (multifunctions) connected with open and inverse mapping principles, distance estimates to the level sets (metric regularity), and a locally Lipschitzian behavior.
Abstract: We consider some basic properties of nonsmooth and set-valued mappings (multifunctions) connected with open and inverse mapping principles, distance estimates to the level sets (metric regularity), and a locally Lipschitzian behavior. These properties have many important applications to various problems in nonlinear analysis, optimization, control theory, etc., especially for studying sensitivity and stability questions with respect to perturbations of initial data and parameters. We establish interrelations between these properties and prove effective criteria for their fulfillment stated in terms of robust generalized derivatives for multifunctions and nonsmooth mappings
01 Jan 1993
TL;DR: The central message of this paper is to show that the global control performance criterion must determine the identification criterion, which leads to non standard identification criteria, which can be minimized by appropriate experimental set-ups.
Abstract: This paper aims at introducing the reader to the various issues that arise in the development of a coherent methodology for the development of robust control design on the basis of models identified from data. When a reduced complexity model is identified with the purpose of designing a robust controller, the model is just a vehicle for the computation of a controller. The design of the identification and of the controller must be seen as two parts of a joint design problem. The central message of this paper is to show that the global control performance criterion must determine the identification criterion. This leads to non standard identification criteria, which can be minimized by appropriate experimental set-ups.
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TL;DR: In this article, a closed-loop characteristic polynomial p(s, q,k) is generated, where the vector k contains the free design parameters in the fixed controller structure and q contains the uncertain plant parameters in a given operating domain.
Abstract: By assuming controller structures in Chapter 2 we have generated several examples of closed-loop characteristic polynomials p(s, q,k), where the vector k contains the free design parameters in the fixed controller structure and q contains the uncertain plant parameters in a given operating domain Q, i.e. q ∈Q.
01 Aug 1993
TL;DR: The parallel approach to force/position control of robotic manipulators is presented, which shows a complete use of the available sensor measurements by operating the control action in a full-dimensional space without using selection matrices.
Abstract: Force/position control strategies provide an effective framework to deal with tasks involving interaction with the environment. In this paper the parallel approach to force/position control of robotic manipulators is presented. It shows a complete use of the available sensor measurements by operating the control action in a full-dimensional space without using selection matrices. Conflicting situations between the position and force tasks are managed using a priority strategy: the force control loop is designed to prevail over the position control loop. This choice ensures limited deviations from the prescribed force trajectory in every situation, guaranteeing automatic recovery from unplanned collisions. A dynamic force/position parallel control law is presented and its performance in presence of an elastic environment is analyzed; simplification of the dynamic control law is also discussed leading to a PID-type parallel controller. Two case studies are worked out that show the effectiveness of the approach in application to an industrial robot. >
TL;DR: A novel discrete-time control strategy is introduced that employs the PNN for direct online estimation of the required feedforward control input.
Abstract: Tracking control of a general class of nonlinear systems using a perceptron neural network (PNN) is presented. The basic structure of the PNN and its training law are first derived. A novel discrete-time control strategy is introduced that employs the PNN for direct online estimation of the required feedforward control input. The developed controller can be applied to both discrete- and continuous-time plants. Unlike most of the existing direct adaptive or learning schemes, the nonlinear plant is not assumed to be feedback linearizable. The stability of the neural controller under ideal conditions and its robust stability to inexact modeling information are rigorously analyzed. >
TL;DR: A class of systems which can be transformed into a global normal form with no zero dynamics is treated, and an output feedback controller that stabilizes the origin and includes the given compact set in the region of attraction can be designed.
Abstract: The stabilization of a class of multivariable nonlinear systems, about an equilibrium point at the origin, using output feedback, is considered. In particular, a class of systems which can be transformed into a global normal form with no zero dynamics is treated. Semiglobal stabilization means that for every compact set of initial conditions, an output feedback controller that stabilizes the origin and includes the given compact set in the region of attraction can be designed. The system equations are allowed to depend on constant unknown parameters which do not change the vector relative degree of the system, and the controller is robust with respect to these parameters. Global Lipschitz conditions are not required. >
TL;DR: An application of this result to fuzzy control is presented which shows that this type of Sugeno controller is a universal controller.
TL;DR: New learning schemes using feedback-error-learning for a neural network model applied to adaptive nonlinear feedback control are presented and it is shown that learning impedance control is derived when one proposed scheme is used in Cartesian space.
TL;DR: Algorithms are proposed for the solution of the robotic (eye-in-hand configuration) visual tracking and servoing problem and the computational complexity and the experimental results demonstrate that the proposed algorithms can be implemented in real time.
Abstract: The use of a vision sensor in the feedback loop is addressed within the controlled active vision framework. Algorithms are proposed for the solution of the robotic (eye-in-hand configuration) visual tracking and servoing problem. Visual tracking is stated as a problem of combining control with computer vision. The sum-of-squared differences optical flow is used to compute the vector of discrete displacements. The displacements are fed to an adaptive controller (self-tuning regulator) that creates commands for a robot control system. The procedure is based on the online estimation of the relative distance of the target from the camera, but only partial knowledge of the relative distance is required, obviating the need for offline calibration. Three different adaptive control schemes have been implemented, both in simulation and in experiments. The computational complexity and the experimental results demonstrate that the proposed algorithms can be implemented in real time. >
TL;DR: The Taylor Instrument Company introduced a completely redesigned version of its Fulscope pneumatic controller in 1939 as mentioned in this paper, which provided an action which the Taylor Instrument Companies called pre-act.
Abstract: In 1939, the Taylor Instrument Companies introduced a completely redesigned version of its Fulscope pneumatic controller. In addition to proportional and reset control actions, this new instrument provided an action which the Taylor Instrument Companies called pre-act. In the same year the Foxboro Instrument Company added Hyper-reset to the proportional and reset control actions provided by their Stabilog pneumatic controller. The pre-act and Hyper-reset actions each provide a control action proportional to the derivative of the error signal. Reset provides a control action proportional to the integral of the error signal and hence both controllers offered PID control. The historical development of these controllers is discussed. >
01 Jan 1993
TL;DR: In this paper, a robust controller based on the Riccati-equation approach is proposed for power system load-frequency control, which is simple, effective and can ensure that the overall system is asymptotically stable for all admissable uncertainties.
Abstract: A robust controller, based on the Riccati-equation approach, is proposed for power system load-frequency control. Only the bounds of the system parameters are required to design the robust load-frequency controller. The proposed robust controller is simple, effective and can ensure that the overall system is asymptotically stable for all admissable uncertainties. Simulation results show that, for the example system, the proposed robust load-frequency controller can achieve good performance even in the presence of generation rate constraint.
TL;DR: Any linear system in controller canonical form perturbed by unknown global Lipschitz nonlinearities satisfying triangularity conditions is shown to be globally stabilizable by a fixed dynamic state feedback compensator whose order equals the state space dimensions.
01 Jul 1993
TL;DR: A methodology for designing adaptive hierarchical fuzzy controllers is presented and a supervisory fuzzy rule set was constructed and used to change the parameters of a hierarchical fuzzy controller to accommodate the variations of system parameters.
Abstract: A methodology for designing adaptive hierarchical fuzzy controllers is presented. In order to evaluate this concept, several suitable performance indices were developed and converted to linguistic fuzzy variables. Based on those variables, a supervisory fuzzy rule set was constructed and used to change the parameters of a hierarchical fuzzy controller to accommodate the variations of system parameters. The proposed algorithm was used in feedwater flow control to a steam generator. Simulation studies are presented that illustrate the effectiveness of the approach. >
TL;DR: A conclusive demonstration for the first time that integral gain control is the best basic strategy for force control of manipulators and the concept of a novel second order low pass filter controller is presented.
Abstract: This paper presents a complete overview of basic strategies that have been proposed for force control of robot manipulators. First, the model of the plant to be controlled is reviewed. Next, the strategies are divided into force-based and position-based categories, according to previously reported implementations. Each of the controller types within these categories is analyzed, and predictions of stability and efficacy are made. Then it is shown that these two categories are actually the same, and this recognition leads to the concept of a novel second order low pass filter controller. Finally, all of the controllers are experimentally tested on the CMU DD Arm II, confirming the theoretical predictions. Among the important results presented is the conclusive demonstration for the first time that integral gain control is the best basic strategy for force control of manipulators. >
TL;DR: In this article, the consequences of the differential algebraic approach in the sliding mode control of nonlinear single-input single-output systems are reviewed in tutorial fashion, and examples illustrating the obtained results are also included.
Abstract: The consequences of the differential algebraic approach in the sliding mode control of nonlinear single-input single-output systems are reviewed in tutorial fashion. Input-dependent sliding surfaces, possibly including time derivatives of the input signal, are shown to arise naturally from elementary differential algebraic results pertaining to the Fliess's Generalized Controller Canonical Forms of nonlinear systems. This class of switching surfaces generally leads to chattering-free dynamically synthesized sliding regimes, in which the highest time derivative of the input signal undergoes all the bang-bang type discontinuities. Examples illustrating the obtained results are also included.
25 Aug 1993
TL;DR: It is shown that standard backpropagation, when used for real time closed-loop control, can yield unbounded NN weights if (1) the net cannot exactly reconstruct a certain required control function, or (2) there are bounded unknown disturbances in the robot dynamics.
Abstract: A neural net (NN) controller for a general serial-link robot arm is developed. The NN has two layers so that linearity in the parameters holds, but the "net functional reconstruction error" is taken as nonzero. The structure of the NN controller is derived using a filtered error/passivity approach. It is shown that standard backpropagation, when used for real time closed-loop control, can yield unbounded NN weights if (1) the net cannot exactly reconstruct a certain required control function, or (2) there are bounded unknown disturbances in the robot dynamics. An online weight tuning algorithm including a correction term to backpropagation guarantees tracking as well as bounded weights. The notions of a passive NN and a robust NN are introduced. >
TL;DR: In this article, a simple solution to the regulation problem of rigid robots based on the availability of only joint position measurements is proposed, which consists of two parts: (1) a gravitation compensation, (2) a linear dynamic first-order compensator.