The Study And Design On Control Strategy Of Regenerative Braking System Of Pure Electric Bus

Regenerative system is the important part in electric bus,adding regenerative system to the bus will reduce energy consume,extend the driving range of the bus,reduce the charging times of battery and prolong the useful life of mechanical braking system. Adding regenerative system will very little change to the bus,all we need to do is refitting the braking pedal. The motor and the battery structure do not to change. The control program of regenerative braking is the crucial part of whole vehicle control program.Increasing the use ratio of regenerative energy and reducing the jerk when braking mode is changing are two goal of control strategy.My task coming from the contract signing by Jilin University and Gaoxin Electric vehicle co., LTD of Jilin Province.Formulating reasonable control strategy of regenerative braking will extend the driving range of the bus and ensure the comfort when braking mode is changed. Designing the soft and hardware of regenerative braking system and doing the hardware in the loop test will ensure the effectiveness and reliability of the regenerative braking system. This article mainly contain the following contents:(1) Analyzing the main unit of regenerative braking system. Analyzing the mechanism of braking valve. Adding angular rotation sensor to the brake pedal and demarcating the relationship of brake pedal travel and senor’s voltage by pedal test. Analyze the structure and cooling pattern of the motor, measure the motor’s extern torque character; analyze the character of battery,research the base parameters of battery. Acquire the relationship between soc and monomer battery’s terminal voltage and confirm the limit of charging current.(2)formulate the control strategy of regenerative braking, this contain the following contents: Confirm the maximum braking torque of the motor confined by the ECE law and the character of motor and battery. Divide the braking modes into three modes, thus little intensity braking moderate intensity braking and huge intensity braking. Discern the vehicle’s load by the acceleration and rear axle torque. Adjust the changing value of the brake pedal travel if the load is different. Build the control strategy when the braking mode is change.(3) Build the vehicle dynamic module in CURISE and set the simulation running cycle. Build the regenerative braking module in MATLAB/Simulink, this contains the vehicle load recognition module, regenerative braking control module and the control module when braking mode is changed. At last do the joint simulation via the two software.(4) Design the software and hardware of the vehicle control system, this mainly contain the following contents: designing the CAN structure and define the message received and transmit by the VCU. I also define the ratio and excursion of some signal. Write the braking control program and power on/off program by Codewarrior. Conduct hardware in the loop test on the VCU test system. The test results show that the regenerative braking control strategy can improve the vehicle economical efficiency, the load recognition control strategy can improve the utilization of braking energy,and the comfort when braking mode is changed has improved.