An Affine Parameter Dependent Controller for an Autonomous Helicopter at Different Flight Conditions

In this paper we address the design of a controller that achieves stabilization and reference tracking at different flight conditions for an unmanned helicopter. The controller proposed is in the form of an H-infinity gain-scheduler, and is used for stabilization and reference tracking, for the 4 axis autopilot. (heave, pitch, roll and yaw control) A nonlinear helicopter model has been built, trimmed and linearized at different flight conditions. Based on the linearized models an approximate affine parameter dependent model has been constructed. Then, a linear parameter dependent controller is synthesized which stabilizes the affine parameter dependent helicopter model. By doing so, a single controller achieves stabilization and reference tracking of a family of linear models by scheduling the controller gains based on the online measurement of the scheduling parameter, which is the forward velocity. Moreover, the affine parameter dependent controller is fitted into the nonlinear helicopter model. It is seen that this single parameter dependent controller successfully stabilizes the nonlinear helicopter model at different flight conditions.