Reliable Controller Design Research Articles

Reliable control design of fuzzy dynamic systems with time-varying delay

This paper focuses on the reliable fuzzy control design problem for fuzzy control systems with time delay. Based on linear matrix inequality (LMI) approach, a method for designing a reliable fuzzy controller is presented. The resulting fuzzy control systems are reliable in the sense that asymptotic stability is achieved not only when all control components are operating well, but also in the presence of some component failures. A reliable fuzzy control design scheme via state feedback is proposed in terms of LMIs. The result is extended to the case of observer-based reliable fuzzy control. Two illustrative examples are given to illustrate the validity of the proposed design procedures.

Reliable control design using a two-stage linear quadratic reliable control

Two-step linear quadratic optimal control update equations and a sequential gain updating scheme are used to design a reliable guaranteed cost discrete-control system called two-stage linear quadratic reliable control (TSLQRC). Using this method reliable linear quadratic design results for continuous-time systems can be easily extended to discrete-time systems. The stability and performance gain margins of the TSLQRC are evaluated to show the connections between the continuous-time and the discrete-time designs.

Robust Low-Order Controller Design for Model-Matching Optimization Using Coprime Factors for Linear Discrete MIMO Systems

This research develops a reliable and systematic low-order controller design method for solving model -matching problem of linear discrete time-invariant multi-input multi-output system. Using the coprime factors and properties of discrete outer function, the low order controller design is reformulated as a convex optimization problem. The solutions are obtained using linear matrix inequality techniques. An IEC turbofan engine is used to illustrate the model-matching design algorithm.

Reliable robust flight tracking control: an LMI approach

This paper studies the reliable robust tracking controller design problem against actuator faults and control surface impairment for aircraft. First, models of actuator faults and control surface impairment are presented. Then a reliable robust tracking controller design method is developed. This method is based on the mixed linear quadratic (LQ)//H/sub /spl infin// tracking performance index and multiobjective optimization in terms of linear matrix inequalities. Flight control examples are given, and both linear and nonlinear simulations are given.

An Iterative LMI Method to Discrete-time Reliable State-feedback Controller Design with Mixed H2/H∞ Performance

This paper studies the reliable mixed H 2 /H ∞ , state-feedback control of discrete-time linear systems based on the iterative linear matrix inequality (ILMI) approach. The design goal is to find an internally stabilizing state-feedback controller such that the nominal mixed H 2 /H ∞ performance measure of a closed-loop transfer matrix is optimized. The designed controller satisfies the H ∞ robust stability constraint and the reliability constraint (in terms of stability and performance) under actuator faults. Besides the advantage of optimizing nominal performance, this new reliable design has the flexibility that it can be formulated to tolerate the actuator faults within certain admissible set of actuators, or to tolerate any single actuator fault. Either partial or complete actuator fault is allowed. Two examples are also given to illustrate the design method and benefits.

Robust reliable control for a class of uncertain nonlinear systems with time-varying multistate time delays

This paper deals with the problem of robust reliable controller design for a class of uncertain nonlinear systems. The system under consideration is subject to time-varying multistate time delays, parameter uncertainties, nonlinearities and even failures in prescribed subsets of auctuators. The nonlinearities are assumed to satisfy boundedness conditions. The parameter uncertainties and multistate time delays are time varying and structured. A systematic approach using linear matrix inequalities (LMIs) is proposed to solve the design problem of this controller. Sufficient conditions for robust stability in the presence of possible actuator failure are given in terms of the LMIs and the controller that stabilizes the system is computed using standard LMI techniques.

Robust reliable control for a class of uncertain nonlinear systems with time-varying multistate time delays

This paper deals with the problem of robust reliable controller design for a class of uncertain nonlinear systems. The system under consideration is subject to time-varying multistate time delays, parameter uncertainties, nonlinearities and even failures in prescribed subsets of auctuators. The nonlinearities are assumed to satisfy boundedness conditions. The parameter uncertainties and multistate time delays are time varying and structured. A systematic approach using linear matrix inequalities (LMIs) is proposed to solve the design problem of this controller. Sufficient conditions for robust stability in the presence of possible actuator failure are given in terms of the LMIs and the controller that stabilizes the system is computed using standard LMI techniques.

Reliable LQG control with sensor failures

The paper deals with reliable LQG controller design for linear systems with sensor failures. A model of sensor failures more practical than outage is adopted. Two procedures of designing reliable LQG controllers are presented: stabilising solutions of three coupled Riccati equations; and solutions to one Riccati equation and two linear matrix inequalities. The resulting control systems are guaranteed to be robustly stable and with a known cost bound on the LQG cost against sensor failures. Algorithms are developed to obtain a solution and illustrated via numerical examples.

A normalizing precompensator for the design of effective and reliable commutative controllers

Sensitivity to parameter perturbation represents the main caution regarding the use of the characteristic locus method on the design of multivariable control systems. The method is not effective when the condition number of the plant eigenvector matrix is high or, equivalently, when the plant transfer matrix differs a great deal from normality. With the view to coping with this problem, it is proposed in this paper a precompensator structure and, in the sequel, two optimization problems are formulated and solved: the first one, for 2 x 2 systems, aims at minimizing the eigenvector matrix condition number; the second one, for the general m x m case, is intended to make the precompensated system as normal as possible by minimizing a defined measure of normality. Once the precompensated system matrix has been made close to a normal one, the characteristic locus method can then be applied effectively, leading to reliable control systems, as far as stability in face of uncertainty is concerned.

Reliable guaranteed cost control for uncertain nonlinear systems

This paper deals with the reliable control design problem for uncertain nonlinear systems. A more practical model of actuator failures than outage is adopted. Based on the Hamilton-Jacobi inequality approach from nonlinear H/sub /spl infin// control theory, a method for designing reliable state feedback controllers is presented. The resulting control systems are robustly stable and with an H/sub 2/ performance bound against plant uncertainty and actuator failures.

Robust reliable control for a class of uncertain nonlinear state-delayed systems

This paper deals with the problem of robust reliable control design for a class of nonlinear uncertain state-delayed systems. The system under consideration involves state time delay, parameter uncertainties and unknown nonlinear disturbances. The nonlinearities are assumed to satisfy the boundedness condition, and the parameter uncertainties are allowed to be time-varying unstructured. The purpose of this problem is to design the state feedback controller such that, for all admissible uncertainties as well as actuator failures occuring among a prespecified subset of actuators, the plant remains globally exponentially stable, independently of the time delay. An effective, modified algebraic Riccati equation approach is developed to solve the problem addressed. It is shown that designed nonlinear time-delay control systems provide guaranteed robust reliable stability despite possible actuator failures. We present an illustrative example to demonstrate the applicability of the proposed design approach.

Reliable Control of Uncertain Nonlinear Systems

This paper is concerned with the reliable controller design problem for a class of uncertain nonlinear systems. For the primary contingency problem, a procedure of designing reliable nonlinear controllers is presented in terms of solutions of Hamilton–Jacobi inequalities. The resulting closed-loop nonlinear system is reliable in the sense that the performance (i.e. internal stability and H ∞ attenuation) of the closed-loop system is guaranteed not only when all sensors and actuators are operational, but also when some sensor and actuator outages occur.

A reliable sequence controller design methodology based on SMT framework

This paper presents a design methodology based on SMT (Supervisor-Monitor-Troubleshooter) framework to construct a reliable sequence controller. In the SMT framework, the supervisor conducts normal process control, the monitor detects fault occurrences, and tho troubleshooter performs fault diagnosis and recovery. The three components colla.borate with each other to enhance process reliability. The design of supervisor, monitor, and troubleshooter is sequentially presented. Via the proposed methodology, a sequence controller can be systematically constructed. Consequently, programming and debugging efforts arc greatly reduced. A mold filling process is also employed to demonstrate the effectiveness of the proposed scheme's design and implementation.

A new controller design scheme for cooperating manipulators - a reliable design approach

A new controller design framework for cooperating manipulators is considered in this paper based on a reliable controller design concept. The objective of this paper is to derive a set of controllers for cooperating manipulators, particularly those that can hand over an object. The key idea is to reformulate the original problem of coordinated control as a reliable stabilization problem, i.e. to design a set of controllers which can stabilize a plant both jointly and alone. By introducing a kind of strict force control scheme in the workspace, the reliably stabilizing controller design technique is applied to derive the controllers. Two contributions exist: (i) clarifying a class of the object which can be handed over by using the proposed control scheme and (ii) presenting a constructive design method of the controllers. Experimental results on the hand-over control of a spherical inverted pendulum with two 6 d.o.f. manipulators are included.

Reliable nonlinear control system design by using strictly redundant control elements

This paper is concerned with the single-contingency reliable controller design problem for nonlinear systems. A procedure for designing reliable nonlinear controllers is presented for nonlinear systems with strictly redundant sensors and strictly redundant actuators. The resulting closed-loop nonlinear systems are reliable in the sense that they provide guaranteed local internal stability and H performance not only when all sensors and actuators are operational but also when any one, but only one, sensor or actuator experiences an outage. An example is given to illustrate the design procedure and the effectiveness of the proposed methods.

Reliable nonlinear control system design using duplicated control elements

Reliable L2 gain bounding (i.e., H∞) controllers for nonlinear systems are designed by using redundant control elements. One sensor and one actuator are duplicated, and the resulting closed-loop system is reliable with respect to both the single contingency case and the primary contingency case. The design procedures for reliable controllers are developed by using the Hamilton–Jacobi inequalities from nonlinear H∞ control theory. Linear reliable controller design methods are also obtained by restricting the proposed nonlinear methods to the linear case, and the linear methods are found to be less conservative than existing methods for linear reliable controller design. Examples are given to illustrate the design procedures for both linear and nonlinear reliable controllers and the advantages of the proposed linear method over existing ones. © 1997 by John Wiley & Sons, Ltd.

Reliable nonlinear control system design using duplicated control elements

Reliable L2 gain bounding (i.e., H∞) controllers for nonlinear systems are designed by using redundant control elements. One sensor and one actuator are duplicated, and the resulting closed-loop system is reliable with respect to both the single contingency case and the primary contingency case. The design procedures for reliable controllers are developed by using the Hamilton–Jacobi inequalities from nonlinear H∞ control theory. Linear reliable controller design methods are also obtained by restricting the proposed nonlinear methods to the linear case, and the linear methods are found to be less conservative than existing methods for linear reliable controller design. Examples are given to illustrate the design procedures for both linear and nonlinear reliable controllers and the advantages of the proposed linear method over existing ones. © 1997 by John Wiley & Sons, Ltd.

High speed externally asynchronous/internally clocked systems

Externally asynchronous/internally clocked (EAIC) systems provide a means of reliable controller design and operation, and incorporate many advantages of both synchronous and fully asynchronous methodologies. The basic memory module of an internally-clocked system is the DFLOP the outputs of which are fully protected from metastability-generated anomalies. As a result, the only input constraint on an internally clocked system is a minimum pulse width corresponding to the frequency of the internal clock. In an internally clocked system, a clock event is not generated until all DFLOPs have resolved into alogically defined state. Because the period of the internal clock depends only on propagation delay through the components of the system, the clock always operates at a maximum possible frequency. Several internally clocked systems, involving both static and dynamic logic, are analyzed by using PSPICE simulations and the results of some real time tests are reported for comparison purposes. The operation characteristics of the DFLOP are analyzed at the component level, and system level comparisons are made with previous work. With submicron CMOS designs using dynamic logic, the internal frequencies of EAIC systems are predicted to exceed 300 MHz with throughputs of less than four ns.

Design of Reliable Controllers for State Delayed Systems

The decentralized H ∞ output dynamic controller for the state delayed systems is first derived. Based on this derivation, a reliable decentralized controller for the state delayed systems is constructed, such that the resulting control systems are reliable in that they provide stability and H ∞ performance not only when all control channels are in operation, but also in the case of control channel failures provided that these failures occur only within a prespecified subset of control components. Furthermore, the centralized controllers reliable against sensor or actuator failures, for the state delayed systems, are presented, and illustrative examples are given to demonstrate the applicability of the proposed approaches.

Reliable stabilization of linear plants using a two-controller configuration

A reliable controller design method is developed for linear, time-invariant, multi-input multi-output control systems; two controllers are designed to stabilize the closed-loop system when acting together and acting independently if one fails. All reliable controllers which achieve closed-loop stability are characterized for strongly stabilizable plants using a factorization approach.