Wheel shimmy suppression through the piecewise nonlinear energy sink: elimination of detrimental isolas

Self-excited shimmy deteriorates the stability and safety of almost every type of vehicle. The triggering mechanism of shimmy has been thoroughly analyzed, but the most typical suppression methodology is not always applicable in many systems, since it affects the prescribed handling performance. In this paper, based on the recent advancement in the nonlinear energy sink (NES), we propose an approach to globally mitigate the shimmy of a towed wheel through an ungrounded NES. The cubic NES, although exhibits good performance, is lacking robustness against external perturbations because an isolated branch of large amplitude oscillations coexists with a favorable small amplitude quasi-periodic motion. Then, an NES with non-smooth damping characteristics is developed, which proved to be able to completely suppress the detrimental isola, without reducing performance; thus, representing an effective and robust solution for shimmy mitigation.