Design and flight testing of various H∞ controllers for the Bell 205 helicopter

This paper describes the flight testing of a suite of H∞ controllers designed using linearisations extracted from a new nonlinear model of the Bell 205 helicopter. Details of the controller designs are presented, together with a comprehensive analysis of simulation and flight-test results. These are complemented by an evaluation of qualitative and quantitative handling qualities information against the design standard ADS-33. The most notable achievements of the work were: (1) stability was achieved for all controllers tested and, moreover, some of them yielded desirable handling qualities from the first test onwards, and (2) a high degree of consistency between desk-top simulation and flight-test results was observed. Achieved performance was generally satisfactory and future planned flight tests will build on these results with the aim to increase performance further. The paper discusses various aspects of controller design and presents an analysis of the results obtained. The likely direction of further work is also discussed.