Design of a Nonlinear Controller for a Quarter Vehicle Active Suspension System

In this paper, a nonlinear sliding mode control scheme for active suspension systems was proposed. Simulation results suggest that the proposed control scheme may result in a system with fast-response and high-precision tracking of a virtual sky-hook damper force so that high ride quality and handling performance can be obtained. In general, the higher of the ride quality is required, the larger of the suspension travel deflection is needed. A nonlinear variable coefficient virtual sky-hook damper with suspension travel deflection function was derived to resolve the inherent trade-off between ride quality and suspension travel deflection. Two road profiles, a sine-wave and a single bump, respectively, were given to demonstrate the effectiveness of the proposed control scheme. Thereby, softening the suspension when suspension deflection is small and stiffening up as it approaches the deflection limits.