Optimization Study On Control Strategy For The Cooperative Braking System In An Electric Vehicle With Independently Driven Front And Rear Axles

With the increasing problems of environmental pollution and energy crisis, clean andefficient electric vehicles have become the main choice. Since cooperative braking systemcan effectively improve electricity economy and braking stability, it has become currentresearch focus. In this dissertation, based on an electric vehicle with independently drivenfront and rear axles, a dual-motor power coupling system, cooperative braking systemconfigurations, optimization methods and a cooperative braking control strategy et,al arestudied.To sovle the problem of the independently driven front and rear axles, a dual-motorpower coupling system which has four working modes is designed, also, considering thestructure and dynamic disciplines, the optimum design parameters are got for the powercoupler with a multi-disciplinary optimization method. The bench and real vehicle testsshow that the power coupler meets the design requirements and the independently drivenfront and rear axles can be realized through the dual-motor power coupling system.To improve the performance of the cooperative braking, aiming at the advantages anddisadvantages of the series and parallel configurations, a seccondary subdivided brakingseverity method which is called combine cooperative braking configuration is proposed.Every optimization model and the optimization strategy is systematically studied fordifferent working modes and different cooperative braking configurations, the design spaceconcept is provided and a overall evaluation method for the cooperative brakingperformance is designed, the evaluation results show that the cooperative brakingperformance of the combine configuration is better than the parallel configuration and is thesame as the series configuration in the four-wheel driving mode, in addition, this mode isalso the best driving mode for the electric vehicle.Based on the four-wheel working mode, a cooperative braking strategy which isbased on the coordination between parallel and combine configurations is proposed. Theglobal cooperative braking design space is divided by regular and irregular border subspacedivision methods, then the subspaces are obtained and the corresponding cooperative braking configuration is designed.To solve the problem of the real-time control and improve the reliability of thealgorithms, aiming at the combine configuration of the different subspaces, the combinestrategies are designed based on DOE sampling, uncertain optimization and responsesurface methods; aiming at the parallel configurations of the different subspaces, theparallel algorithms are designed based on the DOE sampling, certain optimization and theDOE analysis methods. The analysis results show that the algorithms which are based onthe irregular border have better reliability and implementation. The simulation and realvehicle tests show that the algorithms can improve the cooperative braking performanceand have better real-time performance.A cooperative braking control stream is designed. The cycle run simulation shows thatthe regenerative braking energy recovery efficiency is45.132%; the simulation and realvehicle tests show that the control stream has a better cooperative braking performance.