Constructing hybrid control systems from robust linear control agents

Abstract

Hybrid control systems (HCS) arise when the plant, a continuous state system (CSS), is controlled by a discrete event system (DES) controller. It is assumed that there exists a specification on the plant's desired symbolic behaviour. This specification describes how various operational modes of the controlled plant should fit together. One design problem involves determining an HCS that “realizes” the specified behaviour in a “stable” manner. In this paper, a solution is posed which involves finding a sequence of subgoals and controllers achieving the specified behaviour in a “logically” stable manner. The solution can therefore be viewed as a “logically” stable extension of the previously given symbolic specification on the plant's behaviour. This paper shows how such an extension can be constructed using multiple H∞ control agents exhibiting robust stability. The problem formulation leads to a design problem which can be solved using existing H∞ control techniques.