Design and Testing of a Nonlinear Model Predictive Controller for Ride Height Control of Automotive Semi-Active Air Suspension Systems

With the rapid growth of the automotive technology, electronically controlled air suspension has been widely used to improve ride comfort and handling stability of the vehicle by actively modulating the suspension stiffness, vehicle height, and posture. Ride height control (RHC) is the main function of the semi-active air suspension, and it is achieved by conducting air charging and discharging of the air spring, which plays a critical role in improving the vehicle dynamic performance. In addition, the unevenness distribution with payloads at the four wheels, the different dynamic characteristics of the front and rear air suspensions, and the undesired roll and pitch angles make adjustment effect of the vehicle ride height hard to be well addressed. Therefore, an effective control strategy is very essential, which is not only for RHC but also for keeping the vehicle posture, as well as the vehicle dynamic performance. Considering that the full car dynamics is a highly nonlinear model, this paper proposes a novel nonlinear model predictive controller to handle the multi-objective control requirement of a full car system. In order to evaluate the performance of the proposed controller, comparisons among the proposed control algorithm, the existing proportional- integral-derivative method, and the sliding-mode controller are carried out by a numerical analysis. The numerical results show that the proposed method excels the other methods and is effective in the adjustment of the vehicle ride height.