Research On Coordination Failure Compensation Control Of Electro-booster And Esc System

In recent years,to meet the requirements of automotive intelligence and electrification,the automotive brake system has gradually evolved toward the direction of brake-by-wire system(BBW).The conventional vacuum booster brake system is difficult to adapt to the new functional requirements such as active braking and energy recovery proposed by BBW.And the pure BBW has also been greatly restricted in marketing due to manufacturing difficulties,production costs,and security risks.Therefore,the world’s major auto parts manufacturers have proposed a variety of different configurations of brake system,seeking to transition to a pure BBW.The iBooster produced by BOSCH represents a kind of electronically booster brake system(Ebooster)to replace the traditional vacuum booster.By cooperating with the electronic stability controller(ESC),it can realize the functions of active braking and energy recovery.The brake system of this solution is equipped with two actuators in the hydraulic brake system,which can achieve partial functional redundancy and improve the safety performance of the brake system.This paper relies on the school-enterprise cooperation project and the National Natural Science Foundation project to carry out research on the coordination failure compensation control of the Ebooster and ESC System.Firstly,the basic booster control strategy of the Ebooster is completed.Secondly,the wheel cylinder pressure control strategy of the ESC for failure compensation is designed.Thirdly,when the Ebooster’s function of booster brake fails,the compensation redundancy control strategy based on the active brake of the ESC is proposed.Finally,as for the failure of ESC/ABS,the cascading anti-lock braking redundancy control strategy based on the Ebooster is studied.The details are as follows:(1)The basic booster control strategy of the Ebooster: Firstly,the working principle of Ebooster is analyzed,and the mechanism model,friction model and hydraulic system model of Ebooster are established;Secondly,the basic booster control strategy including the booster ratio control layer,the servo-displacement control layer of the booster valve body,and the operation control layer of motor is designed.Thirdly,a hardware-in-the-loop(HiL)test bench for the Ebooster based on the electric cylinder is build;Finally,the test and verification of the basic booster control strategy of the Ebooster are completed on the experimental bench.(2)The wheel cylinder pressure control strategy of the ESC for failure compensation: Firstly,we introduce the working principle of ESC’s active braking for booster compensation,and the control scheme of the high-speed switching solenoid valve in the ESC is analyzed.Secondly,a double brake actuator including the Ebooster and ESC system in HiL bench is built.Thirdly,based on the pressurized and depressurized characteristics of the brake wheel cylinder,we propose the wheel cylinder pressure control strategy of ESC for booster compensation.Finally,the design strategy is tested and verified on the experimental bench.(3)The Ebooster’s booster failure compensation redundant control strategy: Firstly,the booster failure characteristics of the Ebooster are analyzed.Secondly,we designed the Ebooster’s booster failure compensation redundant control strategy including the identification of the booster failure,the identification of the driver’s desired brake pressure,and the coordinated distribution control between the two brake actuators.Finally,on the experimental bench of the double brake actuator,the Ebooster’s booster failure compensation redundant control strategy based on the brake pedal force and the brake pedal displacement are tested and verified,respectively.(4)The cascaded anti-locking brake redundancy control strategy based on the Ebooster: Firstly,the anti-lock braking principle and characteristics of the Ebooster are analyzed,and the HiL experimental bench based on the real-time simulator is built.Secondly,we propose the cascading anti-locking brake redundancy control strategy for the driver’s braking condition including the wheel slip rate control layer based on the sliding mode control,pressure-servo control layer and bottom motor control layer.As for active braking conditions,we propose to optimize the servo layer in the above cascade controller by using a three-step nonlinear method.Finally,the two control strategies are tested and verified on the experimental bench,respectively.