Research And Development Of Automobile Traction Control Unit

With the increase of car ownership and frequent traffic accidents,automotive safety is paid more attention.As one of the active safety techniques,traction control system(TCS)can improve the safety of automotive driving.Through adjusting engine torque and wheel cylinder brake pressure,the excessive spin of the driver wheels are limited by TCS.Thus,the acceleration ability and driving stability in standing start and acceleration process are improved under complicated road conditions.Taking a front wheel drive passenger vehicle as the research object,a TCS hierarchical control strategy is designed.Which includes the identification layer,the TCS control layer and the actuator layer.Low friction coefficient road and split friction coefficient road are recognized in identification layer.The output of TCS control layer are the target engine torque and wheel cylinder brake pressure.TCS control layer is designed based on improved PID algorithm and pressure step-increase logic.The pressure step-increase logic is introduced to correct the expected pressure of PID calculation.The engine output torque and wheel cylinder pressure following the desired value are achieved through actuator layer.Since the wheel speed signal is the basis of TCS control.A wheel speed signal filter based on Kalman algorithm is adopted to improve the quality of the wheel speed signal.A bottom pressure control module is proposed,to achieve the expected pressure of the TCS control layer followed by wheel cylinder pressure.Through actual vehicle test,the two module are verified.Based on MC9S12XS128 microcontroller unit,the hardware circuit module and control software of TCS controller are designed and manufactured.The basic functions of signal acquisition and processing,control decision and actuator drive in TCS controller are achieved.A TCS sliding mode controller is designed based on the sliding mode variable structure theory,to limit the excessive spin of the driver wheels.The TCS controller based on improved PID algorithm and sliding mode algorithm are analyzed through Matlab/simulink and Carsim simulation platform.Then the control effects of the two control algorithms are compared.The effectiveness of the improved PID and pressure step-increase logic algorithm is verified by simulation,and some control parameters are preliminarily matched.Well preparation is made for the real vehicle test of TCS controller through offline simulation.The real vehicle test for TCS controller based on improved PID and pressure stepincrease logic algorithm is carried out.The complicated road conditions test results show that,by controlling the engine torque and the braking pressure,the excessive slip of the drive wheels is effectively limited.And the acceleration ability of the vehicle at horizontal and slope pavement are improved,the validity of the algorithm is verified.Based on the research of traction control technology,the TCS control unit is developed.The results of real vehicle test and offline simulation show that,with the control unit,the drive wheels slip is controlled and the acceleration performance of the test vehicle in complex road conditions is improved.