Research On The Development Of Hill Start Assist Strategy Based On EHB

Nowadays,with the development of the automobile industry,the number of vehicles is increasing.In order to solve the road traffic pressure,various overpasses and underground garages have emerged,and the driving conditions of the vehicles have become more complicated.The typical complicated condition of the start of the slope is one of the inevitable conditions in daily driving.Under such conditions,if the driver improperly operates the vehicle,it is very easy to cause a safety accident.Therefore,the development of the ramp start assist system has become particularly important.As an emerging brake system,the Electrical Hydraulic Brake System meets the development needs of the current electrified and intelligent of vehicles,and improves the driving feeling to a certain extent.In this paper,based on the various problems in the starting process of the vehicle ramp,a derailed EHB based ramp control strategy is proposed.Through the longitudinal dynamic analysis of the vehicle,the force of the vehicle in the starting work of the slope and the working principle of EHB are studied.Based on this,the design of the starting strategy of the ramp is carried out,and the flow chart of the control strategy is given.It is proposed that the vehicle is slipping as the evaluation index of the reliability of the control strategy during the start of the vehicle ramp;the impact degree is used as the evaluation index of the superiority of the control strategy.Aiming at the difficult problem in the slope start control strategy: different recognition algorithms are proposed for vehicle quality identification and slope angle recognition.The slope angle is identified by installing the acceleration sensor,using the measurement principle of the acceleration sensor and filtering the collected data to obtain the ramp angle.The longitudinal quality equation is proposed for the vehicle quality identification,and the recursive factor with the forgetting factor is used.The least squares method is used to identify the vehicle quality,and the effectiveness of the algorithm is verified by the actual vehicle.According to the characteristics of the electronic hydraulic brake system and the requirements of the vehicle chassis system for the brake system,the advantages of the feedforward control algorithm and the PID control algorithm are analyzed.A hydraulic pressure control algorithm for feedforward + segmented PI control is designed.The electronic hydraulic brake system has better robustness and response time,and meets the requirements of the vehicle chassis system.The model establishment and simulation of ramp start control strategy,vehicle quality identification and hydraulic pressure control algorithm were carried out in Matlab/Simulink.The simulation results show that the slope start control strategy designed in this paper is effective and feasible.The actual vehicle experiment was carried out on an electric passenger car.According to the experimental data analysis,the comfort in the vehicle ramp start-up project was improved under this control strategy.Therefore,the strategy designed in this paper is effective and feasible.