The Stability Analysis of the Nonlinear Shimmy
Wang Xuejun Qiau Xin (Department of Aircraft Engineering)
Several nonlinear terms, such as backlash, Coulomb friction and velocity-squared damping in the nonlinear shimmy system, have the significant effect on stability. This paper assumes that the top of nose wheel strut is fixed and gives the complete nonlinear equations used to describe the shimmy system with five degrees of freedom. The describing function method is used to analyse the contribution of the above nonlinear terms to the shimmy stability region. The nonlinear equations are transferred into the state space. The amplitude of limit cycle, frequency and the critical parameter curves are determined by optimizing the real part of complex eigenvalues. Meanwhile, this method can extricate designers from the tedious algebraical derivation in the early shimmy stability analysis. For comparison, the corresponding linear shimmy stability is also analysed. It is shown that the influence of several nonlinear terms in the strut on the shimmy stability region is significant. Because of backlash, the critical taxiing speed of aircraft decreases greatly.
【CateGory Index】： V214.13;;V214. 34;