The shimmy vibration is a nonlinear vibration of the fork-wheel assembly about the steering axis that takes energy from the friction tire-road interaction of the aircraft during taxiing. Because the amplitude of the fork-wheel rotation can increase quickly and causes damages to the NLG, there is the necessity of damping the shimmy vibration as soon as possible.

Passive shimmy dampers are usually installed but their performance lower in off-design working conditions. Adaptive approaches present in the literature ask for the implementation of several sensors and/or for state observer and this can be seen as a drawback because the installation of many sensors means an increase of cost for aircraft manufacturers. To cope with such issues, an adaptive shimmy suppression system based on the Modified Simple Adaptive Control MSAC is proposed in this work. In fact, since MSAC is an output feedback controller, it only requests the measurement of the fork-wheel rotation angle. Moreover, its adaptation scheme is quite simple and this can reduce the online computational burden. The only condition to be satisfied for a safe implementation of the MSAC is the Almost Strict Passivity ASP of the plant. A Parallel Feedforward Compensator PFC is thus designed to let the augmented system meet the ASP requirements and the MSAC is then applied to augmented plant. The nose landing gear shimmy dynamics equations are first recalled. Then the PFC-MSAC is designed and results are last presented and commented.