| Electric and Intelligence of vehicles are the main direction of development of the automotive industry in the future for a long time,this trend puts forward the increasing demand for the braking assist system with active braking function.Among them,because there is no mechanical connection between the brake pedal and the main cylinder of the brake,and the force between them is not affected,the decoupling electric brake booster has a higher feel adjustment of the pedal.In addition,by eliminating the risk of braking failure caused by out-of-control of relief valve in uncoupled system,the decoupling electric brake booster has higher braking reliability.This paper presents a complete decoupled electric brake booster with failure protection and takes decoupling electric brake booster as research object,the following research work has been done in the overall scheme design and mechanism modeling,mechanism parameters and controller hardware design,system control algorithm,system simulation and experimental verification of decoupling electric braking booster.(1)According to the decoupling structure of the electric brake booster,this paper puts forward a decoupled scheme to solve the demand of conventional brake and to keep the feel of the footboard of the vacuum booster,and designs a kind of decoupling scheme for the gap between the footboard pusher and the main cylinder pusher,The scheme is composed of pedal sensing feedback mechanism,brushless DC motor,few teeth difference reducers and rack drive mechanism,brake master cylinder and so on.The scheme has a non-decoupling compact structure and reliable manual backup braking function.In this paper,the dynamic models of the main components of the scheme and the hydraulic braking system are established,and their corresponding simulation models are constructed in AMESim.(2)Based on the conventional braking data obtained from the vehicle braking statistical experiment and the power characteristics extracted from the vacuum booster test,in this paper,the control target of realizing pedal position following control by coupling electric brake booster is determined.And the parameters of motor,main cylinder,driving mechanism and pedal spring are designed and selected.The whole vehicle model simulation verifies the parameters of the design,and passes the vehicle braking coordination time calibration.On the basis of the 3D modeling of the system structure,the prototype of the principle is completed.According to the system control requirements and automobile class specification,this paper designs the controller hardware circuit which are composed of power protection,minimum system,motor driving circuit,CAN and SPI communication circuit.(3)This paper presents a control algorithm for a decoupling electric brake booster.Three brake intentions of drivers can be identified effectively by using the brake intention recognition algorithm of decision tree.The pedal position following control algorithm based on sliding mode variable structure is designed to control the motor driving the main cylinder push rod to quickly follow the pedal target displacement compensation based on brake intention.Vector control based motor bottom control algorithm is designed with the advantages of stable and high precision motor torque control performance(4)In the AMESim simulation software,the performance simulation of the decoupling electric brake booster is carried out in this paper.With the current design parameters,the simulation results show that the decoupling electric brake booster has the similar characteristics as that of the vacuum booster.Simulation results of pedal position following performance show that the decoupling electric brake booster can achieve excellent pedal position following effect when in conventional braking.Based on the braking experiment platform,the pedal position following experiment and manual backup experiment of the coupling electric brake booster are carried out,the experimental results show that the prototype system has good pedal position following effect while maintaining the coupling structure and effective manual backup braking function.The simulation and experiment validates the feasibility of the decoupled electric brake booster solution proposed in this paper. |
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