Robust control and its application to a Bell 205 fly-by-wire helicopter

In the last two decades, the control community has witnessed several major developments in robust control. Theoretical results, especially in H/sub /spl infin// control, have produced a wealth of techniques with which to understand, analyse and design controllers for uncertain systems. A variety of textbooks on robust control is now available and some major applications of advanced control have been carried out. Notable examples of the latter are the Harrier jump jet and the Bell 205 helicopter by Cambridge University and Leicester University respectively, both of which have resulted in successful flight tests. There is also evidence of a growing awareness of, and willingness to apply, advanced control techniques in industry, partly as a result of knowledgeable PhD students moving into industry and partly because of the increasing demands within many sectors of industry for greater levels of reliability, efficiency and performance. There is still, however, a large body of practising control engineers who are unfamiliar with the new theories and accompanying techniques. The control community needs to properly demonstrate the potential of advanced control and it can only do this through real applications. The article reviews some important results in robust control and demonstrates their use through the design of a full-authority flight control system for the Bell 205 fly-by-wire helicopter.