Study On Control Strategy Of Composite Braking System For A Bus

Based on “Research on Composite Braking Technology for Dual-source and Fastcharge Electric Bus” project of the Ministry of Science and Technology,taking CBS(Composite Braking System)as the research object and aming to improve the energy efficiency under the premise of ensuring the safety of vehicle,this paper designs a control strategy for CBS of a bus.In this paper,a simulation model is established to realize the design and simulation of regenerative braking and pneumatic ABS control strategy of CBS.The simulation results show that the control strategy proposed can achieve the expected design goal.This paper mainly studies the following:Firstly,a simulation model of CBS for a bus is established,including a permanent magnet synchronous motor(PMSM)model considering the mechanical and thermal characteristics,a lithium ion battery model,an ABS solenoid valve model,an axle modulator model,a brake model,a tire model considering combined longitudinal-slip and cornering,and a 7 DOF vehicle model.Secondly,a regenerative braking control strategy is designed.This paper studies the braking force distribution strategy based on regulatory constraints.The influence of vehicle speed and battery SOC on the control strategy is considered by introducing the influence coefficient.Based on the motor thermal model,the maximum braking torque that the PMSM can provide under the presence of maximum charging current is deduced.And,the concept of optimal motor braking torque is proposed based on the analysis of the effect of PMSM motor efficiency on regenerative braking energy recovery.Then,the control strategy of the RBS is developed based on the above work.Thirdly,a control strategy of pneumatic ABS is designed.A vehicle speed estimator based on CKF algorithm is designed to realize the accurate estimation of vehicle speed.In order to better control the proportional relay valve,a new PID control algorithm is proposed and the parameters of the algorithm are optimized by using pattern search.The control algorithm of axle modulator and ABS solenoid valve is also studied.Based on the above work,the pneumatic ABS control strategy is designed.Finally,a joint simulation platform based on Cruise,Amesim,Truck Sim and SIMULINK is built.Simulations under different working conditions are preformed to verify the effectiveness the control strategy of CBS proposed.