Sliding Mode Variable Structure Control For The Anti-lock Braking System

Anti-lock Braking System (ABS) is a kind of new initiative equipment for security in vehicles. The main points of this system is to prevent locking of tires when braking of great urgency, for this, it can improve the performance of braking stabilization, and make it more controllable. The Anti-lock Braking System is a strong nonlinear and time-variable system. To satisfy the stability and anti-jamming performance, I used the method of sliding mode of variable structure control to design the controller.Based on the introduction of developing history, the structure and the principles of this system, I have pay more attention on the application of sliding mode control maneuver for this system. Because of the structure character of vehicle and physics principle, and presume some points which can make the analysis more simple, then established quarter vehicle dynamics model, wheel adhesion force model and arrester model. And construct the slide mode controller using the models.It is needed for a vehicle to get the exact optimal slip ratio on different roads for ABS controller. In this paper, we reach the goal through computing with experience formula and data. And design the adhesion force observer to get the road adhesion force and adhesion coefficient which cannot been measured directly. Chattering is the inherent phenomenon of sliding mode control, it will impact the result of controller, even harm for the whole system, and we use the saturation to reduce chattering in the system response.At last, we use the software of MATLAB/Simulink to validate the design. The results show us that the system can work well to follow variety of optimal slip ratio on different roads, and the braking torque can change smoothly, the result can satisfy the requirement of stability for the vehicle braking process.