Research On Control Algorithms Based On Wheel Slip Ratio For ABS

As a typical active safety component for automotives, the main goal of antilock braking system(ABS) is to prevent wheel lockup, to maintain steerability and stability, to reduce the vehicle's stopping distance, and to improve the performance of the brake system effectively during emergency braking.On the basis of the achievement of predecessors, control algorithms of ABS are mainly discussed in this paper. Most of the control methods in the application of ABS including logic threshold control and control method based on wheel slip ratio are introduced, and their advantages and disadvantages are analyzed respectively. Because ABS is a time-variant nonlinear system and sliding-mode controller possesses better self-adaptation for the system uncertainties and external disturbances, in this paper, a chattering-free sliding mode controller with a disturbance observer(DOB) is designed for ABS on the basis of the ABS dynamics model which consists of vehicle dynamics model, tyre model, hydraulic system model and brake model. DOB is introduced to sliding mode controller for compensation of the system uncertainties, and a smooth control law is used to reduce the chattering phenomenon in the sliding mode control. In addition, the effective solutions to the key problems of the ABS such as slip-optimizer and estimation of vehicle speed are proposed. A self-optimizing control is introduced to perform an on-line search for the optimal wheel slip, and the vehicle speed can be estimated from the wheel angular speeds and vehicle acceleration.The development of practical ABS is a comprehensive project. Limited by the experimental condition, ABS simulation studies have been carried out to test the feasibility of control algorithms and simulation results show that the proposed control method can obtain better control performance.