Variable Structure Control With Sliding Mode For Automobile Anti-lock Braking Systems

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, robust theory must be adopted in the development of ABS controller. The main research fruits based on variable structure control with sliding mode in this thesis show below:Based on the analysis of the structure and the principles of this system, Because of the structure character of vehicle and physics principle, and presume some points which can make the analysis more simple, then quarter vehicle dynamics model and wheel adhesion force model are established.Designed the improved variable structure controller with sliding mode based on slip-ratio. The goal of the proposed controller is to maintain slip rate of the wheel within the vicinity of required value. The simulations are carried out in different road conditions and compared the braking performance with common variable structure controller. The result indicated that the system can work well to follow variety of optimal slip-ratio on different roads quickly, exert the robustness fully as well with small braking time and braking distance, and the braking torque can change smoothly which can satisfy the requirement of stability for the vehicle braking process.To solve the problem of the strong nonlinearity and uncertainty in the design of antilock braking system, designed a strong robustness global variable structure controller, the numerical simulation result validate the method.