ROBUST CONTROL APPLICATIONS

Abstract

This plenary presentation will demonstrate the growing importance of robust control theory by describing its application to some non-trivial practical control problems. The talk will begin with a description of the design and flight test of a new batch of H∞ controllers for the Bell 205 helicopter. At the heart of each controller is an H∞ loop-shaping controller, augmented with a hand-tuned reference filter to improve tracking performance and to reduce a perceived phase lag which pilots had complained of previously. Flight testing revealed that, with such an architecture, it was relatively easy to get Level 1 handling qualities ratings in low aggression manoeuvres. Further fine tuning resulted in Level 1 qualities for high aggression manoeuvres and one controller performed to Level 1 standard in all manoeuvres tested.The second half of the talk will consider how robust control techniques can be used to design anti-windup compensators to counter problems associated with saturating actuators, such as pilot-induced oscillations in aircraft and stability/robust performance problems in state-of-the-art hard-disk drive servo systems.The paper is written in two parts: Part 1 considers helicopter control and Part 2 addresses saturation problems in high-performance head-positioning servo systems in high-density hard-disk drives.