H∞ hovering and guidance control for autonomous small-scale unmanned helicopter

This paper describes autonomous hovering control and horizontal guidance control with H_∞ controller and performance verification with flight experimental results for the hobby-class small-scale unmanned helicopter. A simple black-box system identification method was applied, and single-input/single-output (SISO) non-cross coupling stable models were obtained. Cross-validation results showed close agreement in the respective output signals obtained by simulation and by experiment. Attitude control was designed as a minor feedback loop of proportional-integral (PI) blocks with a feed-forward compensator for improvement of reference-following performance. An H_∞ horizontal velocity control system was constructed as an outer feedback loop of an attitude control. The H_∞ controllers were designed in the frequency domain using four closed-loop control specifications and were repeatedly tuned according to the time domain specifications. Position control was constructed by a proportional-derivative (PD) controller serving as an outer feedback loop of H_∞ horizontal velocity control. In the flight experiments, hovering performance within a 1-m diameter circle and 15-m square point-to-point horizontal guidance control were achieved. Good consistency between experimental data and simulation data demonstrates the high accuracy of the models and the adequacy of the modeling method.