Stability analysis of expert control systems

An expert system is a computer program that is designed to emulate a human's skills in a specific problem domain. If it is designed to emulate the expertise of a human in performing control activities, it is called an "expert controller". An expert control system (ECS) utilizes an expert controller to interpret plant outputs and reference inputs, to reason about alternative control strategies, and to generate inputs to the plant to improve the performance of the closed-loop system. While expert controllers are frequently being utilized to perform complex control functions, most often it is the case that no formal analysis of the dynamics is conducted since mathematical analysis of such systems is often considered to be beyond the scope of conventional control theory. In this paper we show how to represent the "rule-based" expert controller (including the inference engine and knowledge-base) and ECS with a mathematical model. Then we show that it is possible to characterize and formally analyze reachability and stability properties for the expert controller and ECS. We illustrate the results by showing how to perform modeling, analysis, and design of an ECS for a part balancing problem in flexible manufacturing systems.<<ETX>>