Primary Study On Anti-lock Braking System For Passenger Car

To insure the steerability and directional stability on driving emergencies, the anti-lock braking system(ABS) presented itself in 1978. There are several critical technologies of ABS, such as the design and manufacture of modulator, the method of accurate distinguishing the property of road surface, and the most important is the method of control.This paper made a deep research on the basis of ABS, and made the passenger car's hydraulic ABS, which include the wheel rotating speed sensor, the hydraulic modulator, and the electronic control unit(ECU), as the research object. The vehicle dynamic model was founded, which is based on the four-sensor four-control-circuit model. The hydraulic modulator's mathematical model was founded, which is based on the circulative modulator. The controller model was established, which is based on the self-optimizing control method.This paper used the software, MATLAB, to establish simulation model, which include the vehicle dynamic model, the hydraulic modulator model, and the controller model. According to the models, the simulative test was carried out in order to investigate the effect of clearance between the piston and master cylinder, which would bring forth oscillation of braking pressure when the clearance exceed some value. The same tests were adopt to investigate the effect of different road surface, which would influence the modulating frequency of the wheel cylinder pressure, and the braking performance. The conclusion of these tests is that the modulating frequency should be faster when the car is on high adhesion coefficient road surface and the model of ABS could recognize the optimal slide rate.The result of these tests testify the system model is coincident with the actual condition, and the control method was effective to distinguish the property of road surface. All these result make up the foundation to further research of ABS.