| Anti-lock Braking System (ABS) is an important installment for improving the automobile active safety. With the automobile high speed today, its application is more and more widespread day by day. The control method is the core technology of ABS, so to grasp the design and the match of the control method has the important practical meaning for developing ABS independently and for futher research of automobile active safety theory and technology.In this paper, sliding mode variable structure control is applied for ABS research. Through analysis, I learn that in the sliding mode control of basing on the reach law, the gain parameter of sign function is the main reason that causes the chattering of the system. So in the paper, the compound control strategy which unifies the fuzzy control and the variable control is proposed, using fuzzy controller to adjust the sign function gain parameter of the sliding mode control auto-adaptedly. This method can not only ensure the robustness of sliding mode control, but also can weaken the chattering effectively.In the ABS control system that bases on slip ratio control, how to gain the goal slip ratio is the key technology for realizing the control. In this paper, with Kiencke μ-S model and using the recursive least squares method to realize the optimal slip ratio real-time and online identification is presented. This method can adapt each kind of road change, and judge the optimal slip ratio accurately. According to this, to trace the optimal slip ratio rapidly in the ABS basing on slip ratio control can be guaranteeed, and optimal control can be realized.On the base of theory analysis, using the Simulink and fuzzy control toolbox in MATLAB to establish some models such as single wheel vehicle model, controller model, optimal slip ratio identification model, emulate road model and so on for simulation verification. The simulation results have further confirmed the validity of the fuzzy variable structure control algorithm and the optimal slip ratio identification algorithm. Beside these, the reasonable control logic and the parameters of the sofeware programming is provided. The simulation results show that fuzzy variable structure control of ABS can control slip ratio to target value steadily, and can make full use of the road surface adhesion condition, so its braking time and braking distance is short. Furthermore, this control method can weaken the sliding mode chattering of general variable control. With the optimal slip ratio identification method basing on Kiencke μ-S model, the optimal slip ratio can be identified exactly not only in single road surface condition, but also in variable road suface condition. With this optimal slip ratio identification method, the fuzzy variable structure control of ABS can realize optimal control.Basing on MC9S12DP256 MCU, the new generation of ABS controller's hardware and software is developed. This lay the solid foundation for realizing the product. Using HCS12 of Singhua university and labotatory debice such as signal accur and oscillograph, software and hardware debugging is done. The debugging results analysis prove that the ECU that have been designed can implement the control function basicly.In all, the research results have proven the feasibility and the validity of fuzzy variable structure control of ABS. With the optimal silp ratio real-time online identification technology, it is an effective control method. It can avoid wheel to lock steadily, and enhance the automobile braking efficiency obviously. It not only has the theory meaning, but also has the practical value.
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