| The electrification and intelligentization of automobiles put forward higher requirements for the braking system,and the traditional vacuum brake booster can hardly meet these requirements.The electric brake booster developed in recent years has the advantages of decoupling from the brake pedal,good dynamic performance,etc.It can help realize the functions of braking energy recovery and active braking.This paper takes the electric brake booster as the research object,focusing on the system selection,the design of the booster motor controller,the active pressure build-up control and the development of comfortable parking function.(1)The structure selection of electric brake booster is matched with the booster motor.The existing electric power braking system has various forms.According to the project requirements,the advantages and disadvantages of each configuration are analyzed,and the mechanical decoupling configuration is selected as the research object.Select the transmission mechanism,calculate and analyze the parameters of the booster motor,divide the main working modes of the booster into ordinary braking mode and active braking mode,and introduce the working principles of the booster in different modes in detail.In order to meet the redundancy requirements of the braking system,a three-level failure backup strategy is designed.(2)Development of the controller of the booster motor based on the model design.According to the control requirements of booster,the hardware circuit of controller is designed,which consists of MCU circuit pre-drive circuit,full-bridge drive circuit,resolver circuit and protection circuit.The motor vector control code is developed based on the model design method.On this basis,the hardware and software of the motor controller are verified to ensure the normal operation of the system.(3)Research on the control algorithm of booster motor and voltage building control of electric booster.As the power source of electric brake booster,the performance of permanent magnet motor directly affects the pressure building capacity of the whole brake system.The simulation model of permanent magnet synchronous motor is built to verify the correctness of the mathematical model of permanent magnet synchronous motor.According to the basic principle of vector control algorithm,the controller of permanent magnet synchronous motor is built.Based on the analysis of the voltage-building control strategy of the system,three closed-loop simulation strategies of position,speed and current are designed.A three-loop vector control algorithm model is built and the effectiveness of the model is verified by simulation.Set up the motor-to-drag test bench,simulate the master cylinder load with servo motor,and test the motor’s transient response ability and steady-state following ability under different loads.An electric brake booster test bench is built,and the booster’s pressure building capacity is tested under real load condition.The test results show that the motor has high dynamic response characteristics,and can quickly follow and respond to the target value.(4)Development of comfortable parking function of electric brake booster.This paper analyzes the causes of uncomfortable parking braking,and puts forward that the braking comfort can be improved by re-planning the vehicle speed curve at the later stage of braking,so that it changes in quadratic curve.The effectiveness of the algorithm is verified by simulation.In order to ensure the braking safety of the vehicle,the solution of "decompression-pressure keeping-pressure increasing" of the braking system is put forward.The simulation and real vehicle test results show that the improved algorithm has good effect and improves the braking comfort on the premise of ensuring the braking safety. |
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