Research On The Hybrid Braking Control Of The Electric Wheel

Withthe increasingly serious problems of energy shortage and environmentalpollution, the research on Electric Vehicle (EV),which has a great advantage inenvironmental protection and energy efficiencyhas become animportantdevelopmentdirecitonin automobilefield.The mileage deficiency has become one of the mainbottleneck for the commercialization of electricvehicles.The regenerative brakingsystem canconvert the mechanical energy into electrical energy, realizing theregenerative use of braking energy,which canimprove the energy utilization efficiencyand extend the driving range of electric vehicles, thus it is of great significance to thedevelopment of electric vehicles. Sinceregenerative braking system has a limitedcapability, itneedsto provide braking force together with mechanical braking systemforming a hybrid braking systemto meet extreme braking demands.Therefore, how toallocate the motor regenerative braking force and mechanical braking force of thehybrid braking systemand coordinate ABS control to ensure the braking safety ofvehicles and meanwhilerecover the maximum braking energy is of great imortance.In this thesis,the quarter-vehicle model ofa in-wheel-motor vehiclewas studied, ofwhich the hybrid braking system is composed of permanent magnet synchronousmotor(PMSM) regenerative braking system and electro-mechanical braking(EMB)system,and an integrated control strategybased on hybrid braking forcedistribution and ABS control, considering braking performance and energy recovery andbraking mode was proposed.In this paper,after introducing the PMSM vector control principle, the regenerativebraking control algorithm based on zero direct-axis current vector control of PMSM inthe electric wheel was studied.And also the detailed energy feedback process of theregenerative braking system based on SVPWM modulation was analyzed.Simulationresults proved its efficiency. In order to achieve optimal braking performance, thesliding mode variable structure control algorithmbased on the optimal slip ratiowas usedfor the ABS control in this thesis,which features itsgood robustness andstabilization.Then, under the considerationof the working characteristics of the EMBand PMSM,a new integrated control strategy including the hybrid braking forcedistribution control and ABS control was proposed.Simulation results demonstrate that, the integrated control strategy can achievereal-time coefficient judgment andreasonable distribution of hybrid brakingforcein different braking conditions, accomplishing the optimal slip ratio of the currentroad.Besides, the strategy also has the advantages of fast response andgood robustness,while maintaining optimal energy feedback rate.