Adaptive Sliding Mode Control of Air Suspension with Auxiliary Chamber Subject to External Disturbance

Controlling the suspension system by using the air spring with auxiliary chamber system is a difficult and complicated challenge due to its strong non linearity, uncertainty and various external disturbances. To guarantee the smoothness of vehicle motion and driving stability, this paper proposes the integration of a nonlinear disturbance observer with sliding mode control, applied to the supplementary air spring with auxiliary chamber system. Firstly, based on thermodynamics and fluid mechanics, a nonlinear model of the air chamber, throttle element and auxiliary chamber are established, and active suspension model considering the variable stiffness of the air spring with auxiliary chamber is designed. Secondly, disturbance observer is designed to observe the uncertainties, and by employing disturbance estimation to design a novel sliding surface, even in the presence of unmatched disturbances. This ensures that the system state progressively converges to the desired equilibrium state along the sliding surface, granting the control strategy the ability to adapt to the suspension system state in real-time. Finally, based on MATLAB/Simulink, the proposed control strategy's effectiveness and robustness are verified through simulations of random road excitation (general conditions) and bump road excitation (harsh conditions).