The Development And Fault Tolerance Control Of Vehicular Regenerative By-wire Braking Systems

The electrification and intelligence of automobiles have become an important forcus of the automobile industry.The combination of electrification and intelligence has become more and more popular,and many intelligent functions are developed based on the electricized platform.Novel technologies such as braking energy recovery RBS,adaptive cruise ACC,automatic emergency braking function AEB,etc.,have made significant contributions to improving vehicle energy economy,safety and comfort.But these novel systems also place new demands on chassis handling systems,especially braking systems.The brake system not only needs to cooperate with the motor to realize coordinated regenerative braking,but also needs to track target hydraulic braking force with a high-precision and achieve fast step braking force response.All of these require the brake system to achieve a combination of energy recovery and by-wire control.The complexity and technical difficulty of the system have been greatly increased,and a series of novel problems have been proposed for system design,control and fault tolerance.In this study,the hydraulic modulation unit of the brake system was designed by analyzing the requirements of the electric intelligent vehicle for the function and performance of the brake system.Through the hydraulic topology design,the regenerative brake-by-wire system design is completed without increasing the complexity of the brake system.Through the design optimization of core components such as solenoid coil and solenoid valve spool,the response frequency and long energization time of the switch solenoid valve are improved,and conventional hydraulic braking coordinated regenrerative braking,vehicle stability control programs and intelligent active braking are realized and integrated.A mathematical physics model of solenoid-mechanical-electro-hydraulic coupling of the on/off switch vavle is established.The influence mechanism of the duty cycle of the control signal on each physical parameter and its changing law are derived.The underlying control method,saturation pilot,which makes the flow characteristic of the solenoid valve consistent and locally linearized is proposed.Aiming at the dynamic pressure difference existing in the system scheme,the hybrid high-frequency pressure difference correction method is studied,which improves the cycle consistency and flow control accuracy of the switching solenoid valve.Based on the adaptive gain scheduling control method,a closed-loop hydraulic pressure control algorithm is designed.According to the high-pressure accumulator and the control target,the controller parameters are automatically adjusted,and the highprecision hydraulic braking force tracking control is realized.Pressure tremors is suppressed by the logic threshold method proposed.Based on the braking pressure control algorithm,the regenerative braking control strategy is optimized to further improve the recovery efficiency of the vehicle.The essence of the over-actuated control system of the brake-by-wire system is revealed.The maximum unrelated element control channel decoupling method and the virtual control channel establishment method are proposed.An integral sliding mode fault-tolerant controller is designed to solve the virtual control input.Through the online control allocation method,the automatic offline of the faulty actuator is realized,and the control target is redistributed in the health actuator to ensure the longitudinal braking performance and directional stability of the vehicle.