Showing papers on "Robust control published in 1978"

Robustness with observers

Abstract: This paper describes an adjustment procedure for observer-based linear control systems which asymptotically achieves the same loop transfer functions (and hence the same relative stability, robustness, and disturbance rejection properties) as full-state feedback control implementations.

Robustness of multiloop linear feedback systems

Abstract: This paper presents a new approach to the frequency-domain analysis of multiloop linear feed-back systems. The properties of the return difference equation are examined using the concepts of singular values, singular vectors and the spectral norm of a matrix. A number of new tools for multiloop systems are developed which are analogous to those for scalar Nyquist and Bode analysis. These provide a generalization of the scalar frequency-domain notions such as gain, bandwidth, stability margins and M-circles, and provide considerable insight into system robustness.

Decentralized robust control of unknown systems using tuning regulators

Abstract: The problem of determining a decentralized robust controller for a general servomechanism problem, in which the system to be regulated is unknown, is considered in this paper. In this problem, the unknown system is subject to disturbances and it is desired to find a decentralized controller so that the outputs track given specified reference inputs, independent of any disturbances occurring in the system, and such that this occurs for any perturbations in the parameters of the system (which do not cause instability). The only assumptions made regarding the system to be regulated are that 1) the system is described by a finite linear time-invariant multivariable model and 2) the system is stable. Note that the order of the system is not assumed to be known. The approach taken to solve the problem is in the same spirit of some results recently obtained on "multivariable tuning regulators" for centralized control systems [1]. In this problem formulation, the constraint is imposed that only one controller (at a given control station) may be adjusted at any time (and that when adjusted, this controller will remain fixed), and that the closed-loop system must remain stable at all times during the tuning procedure. It is shown that necessary and sufficient conditions for a solution to exist to the problem can be obtained by performing some simple experiments on the plant, and that a robust decentralized controller can then be synthesized using the results of these experiments in conjunction with a series of one-dimensional parameter searches performed on the closed-loop system. This later procedure is called "tuning the controller on line." The most interesting feature of this problem which differs from the centralized control problem is that the controller synthesis must be carded out in a certain preassigned order with respect to each controller agent (not necessarily unique); if this ordering is not carried out, then there may not exist a controller synthesis for the problem.

Flight control application of model algorithmic control with IDCOM

Abstract: Some of the outstanding problems in the application of modern control theory to Flight Control Systems are: (i) model selection, (ii) incorporation of state and control constraints, and (iii) robustness and sensitivity to unknown parameters and disturbances. In this paper, we use a technique called Model Algorithmic Control (MAC) with IDCOM which resolves the above problems in an effective manner. The technique was originally developed for industrial applications in France. It is based on an identification-optimization approach, which is very general in nature. MAC is a digital technique that makes full use of the capabilities of current microprocessors and any future developments in microprocessor technology would further enhance its effectiveness. In this paper, we describe an application of MAC to the design of an adaptive autopilot for pitch control of a high performance aircraft.

New structures for parameter-insensitive controllers

Abstract: Several methods have been proposed for designing feedback control laws which are minimally sensitive to variations in system parameters. The restricted structure of these control laws often limits the extent of their parameter insensitivity. In this paper, we show how the state feedback controller form may be extended to allow maximum variations in system parameters without loss of stability or significant deterioration in performance. All control structures are passive and linear. They appear to be most useful when there are large variations in parameter values.