Analysis of a shimming aircraft NLG controlled by the modified simple adaptive control

The aircraft nose landing gear (NLG) can suffer of an unstable vibration called shimmy that is responsible of discomfort and of fatigue stress on the gear strut components. An adaptive controller is proposed in this paper to cope with the aforementioned problem. It is based on a method called Modified Simple Adaptive control (MSAC) which is able of governing the NLG motion by using a feedback signal that relies on just one output of the plant. The MSAC only asks for the passivity of the controlled plant. With this aim, a parallel feedforward compensator is employed in this work to let the system satisfies the almost strictly passivity (ASP) requirements. The nonlinear equations that govern the aircraft NLG shimmy vibration behavior are used to analyzed the controlled system transient response undergoing an initial disturbance and taking into account different taxiing speed values.