Sliding Mode Control with Nonlinear Disturbance Observer for Suspension Performance Improvement in Active Pneumatic Quarter-Car Systems

This paper presents an advanced control method combining Sliding Mode Control (SMC) with a Nonlinear Disturbance Observer (NDO) to improve the suspension performance in a quarter-car active pneumatic suspension system. The proposed SMC ensures the convergence of system states, improving the response and robustness against the uncertainties of the system parameters. Meanwhile, the NDO estimates and compensates for the external disturbances and model uncertainties in real time, thereby eliminating the system disturbance. In addition, a mathematical model of the quarter-car active pneumatic suspension system is developed, considering the dynamics and nonlinearities of the air spring system. And then, the stability of the proposed closed-loop system is proved by using Lyapunov theory. Finally, simulation results demonstrate that the proposed SMC-NDO controller significantly reduces the vehicle body acceleration, suspension deflection, and tire dynamic force compared with the conventional sliding controller and passive suspension system. The effectiveness of the proposed approach is determined by improving ride comfort, handling stability, and road holding under various road excitation conditions based on ISO 2631.