Research On Stability Control Of Electro-hydraulic Compound Braking For Distributed Front Driven Electric Vehicle Under Multiple Operating Conditions

With the rapid development of new energy vehicles in China,electric vehicles have become a hot selling model of various vehicle companies,while distributed driven electric vehicles have inherent advantages.Because each motor can be independently driven and braking,the two sets of brake actuator: motor braking and hydraulic braking system can complement each other,forming a control system with multi actuator output.Compared to traditional fuel vehicles or centralized electric vehicle,distributed driven electric vehicle can achieve vehicle stability control more freely,flexibly and quickly.For the braking process of a distributed driven electric vehicle,how to combine the advantages of the motor brake and the hydraulic brake to realize the electro-hydraulic composite braking and give full play to the braking stability to achieve the distributed driven electric vehicle brake stability control through a variety of operating conditions is the purpose of this study.This paper first analyzes the structural characteristics of the distributed driven electric vehicle,completes the system dynamics modeling of the vehicle in Carsim,and completes the dynamic parameter matching by setting the dynamic performance requirements.Based on the space vector control algorithm,the model of permanent magnet synchronous motor was built,and the performance of the vehicle model was verified to meet the experimental requirements.Then,for the general braking conditions,a front-rear braking force distribution method based on the stability weight coefficient is adopted.The safe braking interval of the distributed front-drive electric vehicle is optimized to be divided.The stability weight coefficient is analyzed according to the driver's braking intention and the driving condition of the vehicle,so that the braking force distribution of the front and rear axles can be adjusted in real time and combined with the motor braking and hydraulic braking to achieve braking stability of the vehicle under general braking conditions.Secondly,through the differential braking control strategy based on the additional yaw moment,the driving stability of the distributed driven electric vehicle under certain extreme conditions is achieved.In this paper,a hierarchical control strategy is adopted.For the upper controller,it is necessary to make accurate identification through the running state of the vehicle.According to the state parameters of the vehicle and the driver's input parameters,the resultant force and the resultant force moment of the lower controller are obtained.The lower controller in consideration of the constraints of the hydraulic motor and at the same time,achieving the optimal allocation of the braking force of each wheel through the system optimal objective function,so that the vehicle can remain stable under the extreme conditions.Finally,the establishment of the control strategy model was completed,and the joint control simulation platform based on Carsim and Matlab/Simulink was established.Through the simulation experiments of multiple operating conditions,the feasibility of the stability control of electro-hydraulic compound braking for distributed front driven electric vehicle under multiple operating conditions was verified.