Improvement of helicopter handling qualities using Hinfinity -optimisation

Presents the results of a study into the use of H^infinity -optimisation for the design of robust feedback control laws for improving the handling qualities of high-performance helicopters. A low-speed controller was designed to give accurate control of pitch and roll attitude yaw rate and heave velocity for a typical combat helicopter. The design was based on a linearised model obtained from a six-degree-of-freedom nonlinear model of a helicopter. Robustness was a major issue because rotor dynamics were not included in the design model. Numerical compliance of the design with handling qualities requirements was assessed by testing simulated responses against specifications from a proposed airworthiness design standard. Robust stability was assessed from singular-value plots. In addition, the qualitative features of the design were assessed in a piloted flight simulation trial held at RAE, Bedford.