Research On Control Strategy And Hardware In The Loop Of The Electric Power Assisted Brake System Of Passenger Car

At present,intelligent driving vehicles and new energy vehicles have put forward higher requirements on the functions and control of passenger vehicle braking systems.However,traditional braking systems are difficult to meet these needs.In recent years,the configuration of electric brake hydraulic brake systems for passenger cars with electric brake boosters as their core has been constantly emerging.The electric booster of this configuration uses a permanent magnet synchronous motor as a braking power source,which has good dynamic performance and controllability.What's more,it can realize functions such as active braking and adjustable pedal feel.The electric brake booster can work in conjunction with a traditional hydraulic adjustment unit to back up each other to achieve a redundant backup function of the braking system.The operating mode of the system can be divided into conventional driver operating modes,active braking modes,etc.,which can meet the new working requirements of the braking system of contemporary automobiles without requiring major changes to the current braking system.Relying on the school-enterprise cooperation project "Development of Control Algorithm of Intelligent Driving Braking System " and "Development of Ebooster Principle Prototype for New Energy Vehicles ",research on the control strategy and hardware in the loop of the electric booster braking system has been carried out in this thesis.The following aspects are mainly included.(1)?Analysis and determine the key parameters of electric power brake system for passenger cars.To achieve similar boosting characteristics(brake feeling)as the vacuum booster,the working principle of the vacuum booster and the reasons for its basic boosting characteristics were first analyzed.Then,introduce the structure,basic working mode,working principle,advantages and control ideas of an electric booster were introduced.And a detailed comparison with the vacuum booster was made.Finally,to establish a dynamic model of the electric brake booster used for simulation and parameter matching optimization,key parameters of the servo motor,transmission mechanism,and feedback disc of the power coupling device were measured through relevant tests.(2)? Establish a simulation model of the electric power-assisted braking system.Establishing a model of an electric power-assisted braking system for simulation and parameter matching optimization can not only provide theoretical guidance for system scheme verification and prototype production in the early stage,but also effectively shorten the development cycle of the system control algorithm.The brake actuator model of an electric power-assisted braking system,including an electric brake booster and a hydraulic system from the master cylinder to the wheel cylinder are established in thesis.The brake booster model includes a dq axis model of permanent magnet synchronous motor,a reduction gearing mechanism model,a power coupling device feedback disc model,and an inverse model thereof.A brake hydraulic system model of a plunger-type master cylinder,a hydraulic adjustment unit,and a wheel cylinder for a hydraulic load of an electric booster model was established.Based on the data collected by the brake test bench,the established hydraulic system model was verified.(3)?Study on the control strategy of electric power-assisted braking system of passenger car.Firstly,an algorithm for identifying the driver's braking operation intention is designed.Secondly,the hierarchical control strategy of the electric booster is designed.The upper level is to obtain the target servo displacement,and the lower level is to control the position of the motor.According to the characteristics of the feedback disc and the working principle of the booster,the position error between the servo displacement and the pedal input displacement is designed and the target servo displacement of the servo body is obtained with the help of the input pusher displacement.Then,a modified PID position servo loop controller,a feedforward decoupled current controller,and a field weakening controller are designed for the control of the motor.Finally,the effectiveness of the motor control algorithm is verified by simulation experiments.In addition,a pressure closed-loop control algorithm for active braking is also designed,which is used to achieve accurate control of the brake master cylinder pressure,laying the foundation for the application of electric boosters to complete vehicles.(4)?Simulation of electric power-assisted braking system and hardware-in-the-loop test verification for vehicle applications.Firstly,the control strategy of the complete electric power-assisted braking system is verified by using the data of the real braking test bench.Secondly,the automatic emergency braking(AEB)and braking anti-lock(ABS)function algorithm based on the optimal slip rate through the active pressure control of the electric brake booster is also designed.Then,a hardware-in-the-loop test platform based on dSPACE software and hardware,vehicle dynamics software CarSim RT,and real electric powerassisted braking system-in-the-loop was built.Finally,through the AEB test conditions of Euro NCAP and various road attachment conditions,hardware-in-the-loop tests were performed to verify the performance of the AEB braking pressure response and the function of ABS only based on electric brake booster.The experimental results show that the electric brake booster can achieve AEB and ABS functions and the effect is satisfactory.