In this paper, motion differential equation of the two degrees of freedom(2-DOF) vehicle is established based on the linear two degrees of freedom vehicle model and is derived without simplifying the front wheel steering angle(FWSA), then we analyze the vehicle's steady-state response , transient response and the amplitude-frequency characteristic of yaw velocity under different FWSA with the help of the matlab software and finally compare the results with the simplified ones to determine how the FWSA influences the level of the vehicle handling and stability(VHS). At the same time in order to better improve the VHS, this paper proposes a set of active control theory to optimize vehicle’s steady-state performance.The results show that: while the FWSA is small, it has a less influence on vehicle handling and stability, the FWSA is large,it has a greater influence on vehicle handling and stability and the active control can make the vehicle in the best response state when it is in the steady-state.

In this paper, the theory of a variable structure model following control (VSMFC) is employed to the design of the controller for an active suspensions of 4-degree-of-freedom (4-DOF) automobile model. The sliding mode equation is derived by applying VSMFC theory and the parameters of the switching function are obtained by using the method of pole assignment; a hierarchical algorithm with control variables started in sequence is applied to solve the active force; a method of exponential approach law is used to improve the dynamic performance of the controller. The efficacy of the controller is verified by simulation carried out with the help of Matlab/ Simulink. The results show that the active suspension controller based on VSMFC theory is superior in both robustness and performance.