An intelligent Assistant for Control System Design

Abstract

Design of control systems following initial component selection generally involves an iterative process in which the designer considers the placement of one or more compensation elements (lag, lead, laglead, PI etc.) in one or more locations in the system (main feedforward or feedback loop, minor loop(s) etc.) and subsequently derives a mathematical representation for the system usually in the form of a transfer function. The designer then checks that the design specifications can be met and when a number of alternatives meet the design specifications other criteria such as cost can be considered.

This paper discusses how an Expert System Design Assistant with computer algebra capabilities can be used in providing a very good working environment for CAD of control systems. A preliminary version of such a system for servomechanism design is presented. The present version accepts the components of the system as block diagram elements and its knowledge base includes transfer function descriptions for the elements as well as for a catalogue of compensation elements. Also included in the knowledge base are the characteristics of the various elements and their effects on overall system characteristics which may form part of the design specifications. The Expert System provides assistance in selecting the compensation type and the most appropriate synthesis and analysis approach.