| With the development and progress of China's new-energy automobile industry,the proportion of electric vehicles is increasing.As regenerative braking is an important means to improve the endurance of electric vehicles,the research on braking energy recovery is of great significance to the development of electric vehicles.Since the addition of regenerative braking force will affect the traditional hydraulic braking system and ABS,how to better coordinate the regenerative braking force and hydraulic braking force is of great significance to the recovery of braking energy and active safety system of vehicles.The current relevant research almost focus on hybrid or centralized electric vehicles while the research of Electric-wheel vehicle is very little,so this paper is dedicated to Electric-wheel vehicle.In this paper,the braking force distribution strategy of electro-hydraulic composite braking system and the ABS control strategy by adjusting motor torque were designed based on newly hydraulic control unit.In addition,this paper also researched on the ABS control strategy by cooperatively adjusting motor torque and hydraulic braking torque.Then these strategies were simulated through the built simulation platform.Finally,the hydraulic control unit test and regenerative braking test were carried out.Specific research contents are as follows:Firstly,the overall layout of the electro-hydraulic composite braking system and the structure of the newly hydraulic control unit were determined by analyzing the performance requirements of the electro-hydraulic composite braking system and the influencing factors of braking energy recovery.Then,the braking force distribution strategy of the front and rear axles and the motor-hydraulic braking force distribution strategy were determined.An antilock control strategy based on pure motor torque regulation was proposed.In addition,the ABS coordinated regulation based on motor braking torque and hydraulic braking torque was realized by the logic threshold control method.Secondly,the hydraulic control model and motor regenerative braking system model were established based on AMESim,and the simulation test platform was built by combining CarSim and Simulink.The conventional braking simulation test were carried out using the simulation testing platform in different intensity under different braking initial speed after setting the corresponding simulation working condition as well as the evaluation index.The results indicate that the proposed braking force distribution strategy not only can achieve the goal of the driver braking intensity but also possess high braking energy recycling ability.Moreover,the anti-lock braking test was carried out on the different adhesion coefficient of road surface including low adhesion coefficient,high adhesion coefficient and variable adhesion coefficient.The result show that the ABS control strategy by adjusting motor torque can control the wheel slip-rate near the ideal slip-rate.Compared with the collaborative regulation scheme,the ABS based on motor regulation can control the wheel state more quickly and accurately.Finally,the hydraulic control unit test and motor regenerative braking test were carried out.Taking the ESC hydraulic control unit as the prototype,the newly hydraulic control unit was approximately equivalent by controlling the booster valve.The test results show that the newly hydraulic control unit designed in this paper can achieve a pretty accurate response to the target hydraulic braking torque.In addition,a vehicle test platform for hub motor driven vehicle was built,and regenerative braking test of hub motor was conducted on this platform.The test results show that the motor can generate current when the vehicle speed is higher than 10 km/h;the motor cannot generate current when the vehicle speed is lower than 10 km/h.Two experiments lay a foundation for further research on electro-hydraulic composite braking system. |
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