Weighting function specification in H∞ design [battlefield helicopter]

This paper describes the application of H_∞ to the design of a controller for a battlefield helicopter. It shows the effect of the choice of the weighting functions on the performance of the resulting closed loop system, and indicates how to utilise the freedom of choice. The appropriate handling qualities requirements documents describe the response shapes that are desirable for particular flight conditions, and these can be used as guidelines for further development of the cost function weights. Bandwidths on selected channels can be manipulated to a certain extent by moving the sensitivity function weights, and overshoots can be corrected by careful targeting of the rate feedback channel weights. Actuator movements can be monitored by examining time responses, and these give useful indicators of the feasibility of any design changes