Investigation on the effect of coulomb friction on nose landing gear shimmy
Landing gear shimmy remains a challenge in aircraft design despite abundant advances in aircraft engineering in the past few decades. Accurate shimmy prediction is closely tied to availability of dynamic models with all relevant types of motions and key nonlinear elements, a matter which has been accomplished in the present study through including rotational, lateral, longitudinal, and axial degrees of freedom and tire, shock absorber, and Coulomb friction nonlinearities. Using multi body dynamic simulations, stability of the nose landing gear is studied as a function of key system parameters. Influences of nonlinearities are investigated in isolation, with a more in depth look at the Coulomb friction effect, which is modeled as a function of the shock absorber stroke rate and rotational shimmy speed. It is found that Coulomb friction is a key factor in determining the onset and type of shimmy. The effect of friction parameters is then studied using nonlinear sensitivity analyses, and witnessed trends are utilized to draw design recommendations.