Active Nonlinear Vehicle-Suspension Variable-Gain Control

This paper presents a novel control method applied to nonlinear vehicle suspension systems. Here, a quarter-car two-degree-of-freedom system with nonlinear suspension dynamics that is excited by unknown road profiles is considered. An extended observer is used to estimate the nonlinear effects as well as the road profile. This observer relies on 2 position (or deflection) measurements. Based on the estimation, a simple adaptive feedback-linearization scheme is implemented to cancel the effects of the nonlinear suspension. Finally, the frequency content of the estimated road profile serves as a selection criterion in a variable-gain linear control scheme. Simulation results demonstrate the merits and the applicability of the proposed approach