Active shimmy damping using fuzzy adaptive output feedback control

In the context of aircraft, shimmy is an oscillatory phenomenon of the landing gear mainly due the tire dynamics and the landing gear structural dynamics. This phenomenon, which can result in severe structural damages of the landing gear, is here actively damped by a direct adaptive output feedback controller. The difficulties to model the ground/wheel interface require the use of an adaptive controller that can modify its behaviour in accordance with the plant dynamics. Thus, the proposed controller uses a fuzzy system to approximate the ideal feedback linearization law. Based on Lyapunov´s theory, it is proven that the proposed adaptive control solution guarantees that all the error signals of the close-loop system are bounded. The main advantage of this control solution lies in the fact that the states of the system are not required for the synthesis of the controller. Simulation results show that the proposed control law creates a realistic control input which properly damps the oscillations. This work is supported by the European DRESS project (Distributed and Redundant Electromechanical nose gear steering System).