Active steering control is one of the approach that can be used to improve the vehicle's lateral and yaw stability. By combining active front steering and active rear steering control, the vehicle's handling and stability can be improved via four wheel active steering (4WAS) control. In this paper, a robust control algorithm of sliding mode control is designed for 4WAS vehicle. Single track 2 d.o.f linear model is utilized for controller design and simulation purpose. Simulation for 4WAS and front steering (AFS) is carried out in Simulink for step steer and double lane change maneuver to verify the effectiveness of the proposed control system. The result shows that the 4WAS perform better than the AFS in tracking the desired response trajectory.

The composite nonlinear feedback (CNF) control technique is successfully applied to design the controller based on control law for an active suspension system. The CNF control law is composed of a linear control law and a nonlinear feedback part. The main idea of CNF is to design the linear control law with a low damping-ratio to achieve fast rising time and to design the nonlinear feedback part to result in a high damping-ratio to remove the overshoot caused by the linear control law when the system controlled output approached the reference. Such the CNF control laws can improve the tracking and regulating performances of the resulting closed-loop systems. The active suspension system is hierarchically divided into two subsystems with the system transformation based on the system structural properties at first and then the CNF control laws are designed for the two subsystems each One of the CNF control laws is designed for tracking control and the other is designed against the mismatching disturbance. The complete control law is made by combining the two CNF control laws and the system transformation. The simulation results show that CNF controller is better than LQR controller and passive model. The computer simulation is done to prove the CNF control performance.

The vehicle handling and stability in emergency situation can be enhanced with direct yaw moment control (DYC). In this paper, a new controller using super twisting technique based on second order sliding mode control (SOSM) is proposed for the yaw moment control. The controller is designed based on two degree of freedom (2DOF) nonlinear model. The effectiveness of the proposed controller is compared to PI controller and conventional sliding mode controller by co-simulations in CarSim and Matlab/Simulink. The results show that the SOSM give better performance in tracking the desired response necessary for the vehicle handling and stability. In addition, the chattering phenomenon is also reduced, giving a smooth tracking trajectory.

The purposes or functions of the commercial car suspension system are to take care on the car body weight, to isolate the car body from road profiles disturbance and to maintain the grip force between the wheel and road profiles. The Composite Nonlinear Feedback (CNF) control law is proposed in this comparative study between conventional linear model and Macpherson model. The control performance consists of velocity of car body, suspension deflection, wheel deflection and velocity of a car wheel. The main measurement in this study is the acceleration of the car body. The Linear Quadratic Regulator (LQR) and passive model are involved in this control performance is for comparison purposes. The mathematical model of linear model and MacPherson model are focused on the quarter car model active suspension system. The simulation work is done by using MATLAB and SIMULINK to see the control performance on the quarter car active suspension model. In this paper we can conclude that the CNF achieved the main objective of active suspension which is the ride comfort and road handling.