Evaluating H-infinity controllers on the NRC Bell 205 fly-by-wire helicopter

This paper describes the development and validation of a nine-degree-of-fre edom (DOF) helicopter model, and the use of this model in designing H-infin ity optimal controllers for testing on an experimental fly-by-wire helicopt er. The model includes rotor flapping dynamics and an inflow correction fac tor. Its use has led to improvements (with respect to earlier designs based on a different model) in the robustness properties of the resulting contro ller. For example, the need for predictor-type filters in the feedback path has been eliminated. Flight-test results are presented. Discrepancies stil l remain between predicted and achieved performance, but overall handling q uality ratings have improved with respect to a previous H-infinity design, and clear improvements have been obtained in pitch and roll attitude contro l: e.g. an increase in roll axis bandwidth from 1.9 to 2.5 rad/s. (C) 2001 Elsevier Science Ltd. All rights reserved.