Research On H_∞ Control Of Vehicle Active Suspension System Based On Four DOF Vehicle Model

In this paper, four degree-of-freedom (DOF) mathematical models of vehicle active suspension and passive suspension have been set up and robust control of active suspension has been studied given the complexity of the disturbance and unmodeled high order dynamics in the model. Firstly, considering the uncertainty as full-block matrix whose H norm is bounded, a robust controller is designed and robust stability of the system is analyzed using method. Secondly, given the structure information of the uncertainty, synthesis is adopted to design a robust-performance controller to eliminate conserveness in H design. Finally, combining the individual advantage of H2 control and H control, a mixed H2/H optimal controller is designed based on linear matrix inequality which makes the system have good time-domain LQR performance as well as robust stability. All the active suspension systems above and corresponding passive suspension system are numerically simulated in MATLAB6.1. The results of the simulation show that, compared to the passive suspension system, the active suspension systems effectively suppress the vibration of vehicle in the range of frequencies sensitive of human body, greatly improve the ride comfort and have strong robustness. Hence, it provides some valuable theoretic reference for the research of vehicle active suspension control.