Adaptive sliding mode control based nonlinear disturbance observer for active suspension with pneumatic spring

Abstract

Pneumatic springs have been used for the automotive suspension to induce a flexible stiffness and create the control forces according to various uncertain masses of passengers and exogenous inputs. However, the control of the vehicle suspension system using the pneumatic spring is a very complicated task because it involves parametric uncertainties, external disturbances, and system nonlinearities. In this paper, an adaptive sliding mode control (SMC) based on nonlinear disturbance observer (NDOB) is designed to obtain passenger comfort and keep the driving safety of the pneumatic active suspension. The nonlinear disturbance observer is proposed to asymptotically reject the external disturbances and overcome parametric uncertainties which exist in the suspension system such as road profiles, different passenger masses, and actuator dynamics. Finally, comparative simulations and experimental results are given and compared by the pneumatic vehicle suspension test bench to demonstrate the efficiency of the proposed SMC - NDOB scheme for different road conditions. Results show that the RMS acceleration value is decreased by 41.5% when the proposed control is used for the experiment with the bump road profile.