On the analysis of passive vibration mitigation of nose landing gears

Shimmy is the self-excited rotational-lateral oscillation encountered in some wheeled structures. In landing gears, shimmy can lead to passenger discomfort, impairing pilot's visibility, and even structural failure of the gear system. The challenge of nose landing gear shimmy vibrations is largely addressed through adding passive shimmy suppression devices to the gear, known as shimmy dampers. Despite the wide treatment of shimmy modeling in the literature using various approaches, little is known about shimmy dampers'performance and their influence on the dynamics. This is mainly due to ignoring the shimmy damper in gear dynamic models or simplifying the shimmy damper to a mere damping coefficient added to the landing gear's structural damping. In this work we present a multi degree of freedom nose landing gear model including a two-piece strut, with a generic shimmy damper added in between of the struts as it is the case in the physical system. Using linear stability analysis and nonlinear time domain simulations, we identify stability trends of the coupled system and offer recommendation for design of future shimmy dampers.