Nose Landing Gear Simple Adaptive Shimmy Suppression System

The occurrence of shimmy vibration in aircraft nose landing gear can cause an increase of fatigue stress on the nose landing gear mechanical elements that can eventually lead to high wearing of components as well as to severe damage of the leg, giving raise to safety issues. The use of the Modified Simple Adaptive Controller is investigated for the realization of an adaptive shimmy suppression system. The nonlinear governing equations that model the shimmy vibration behavior of an aircraft nose landing gear are first linearized in order to synthesize the adaptive controller, while nonlinear terms are then taken into account as disturbances. The almost strict passivity of the plant is obtained by using a parallel feedforward compensator. The parallel feedforward compensator is designed as the inverse of a stabilizing controller while the Modified Simple Adaptive Controller is tuned by considering the minimization of some dynamic performance parameters as design requirements. The influence of the advancing speed on the controlled plant response is studied by simulating scenarios of aeronautical interests.