L1 ADAPTIVE SPEED CONTROL FOR A HELICOPTER

Adaptive control theory is used to improve robustness of systems against model uncertainties and disturbances. Two of the main drawbacks of adaptive controllers is the lack of criteria to measure the robustness of the controller and the speed of the adaptation loop. In L1 adaptive control theory both problems are solved by the introduction of a low pass filter in the control input. The L1 adaptive control robustness and stability are guaranteed by numerical criteria. L1 adaptive control raised a great interest in the aerospace field due to the presence of nonlinear and uncertain dynamics that affects aircraft flight performances. Such strategy by the way has not been widely used and explored for rotorcrafts. In this article the authors propose an L1 output feedback speed controller for helicopters. The control system architecture is tested by means of a simulation test campaign through the use of a nonlinear helicopter model. Both performances and robustness of the controller are evaluated, even in presence of disturbances.