Study On The Hybrid Anti-lock Braking Control In Electric Vehicle

As the representation of new energy vehicles,electric vehicle has the advantages of zero emission,small noise and high utilization of energy.But most electric vehicles have low endurance,which makes it difficult to use the electric vehicle widely.Regenerative braking of motor is an effective means to increase the mileage of electric vehicles,and the motor has the advantages of quick response,precise control,and energy recovery.But the motor braking force is relatively small and the stability is poor,so the hydraulic brake system is still used in the anti-lock braking of electric vehicles.In order to use motor braking in the anti-lock braking process and realize motorhydraulic coordinated anti-lock braking control,the following aspects have been done in this paper:Based on the analysis of the composition and working principle of the hydraulic braking system,the corresponding mathematical model of hydraulic braking system is established.The structure of Brushless DC motor is analyzed and its equivalent mathematical model is established.The braking adjustment process of the motor with half bridge modulation and full bridge modulation is analyzed respectively,and the two modulation modes are compared by simulation.Aiming at achieving energy recovery,three hybrid braking force coordinated control strategies are proposed.From the perspective of feasibility and braking stability,the integrated energy recovery coordinated control strategy is selected.The hydraulic anti-lock braking system and the motor anti-lock braking system are established respectively based on slip rate control,and the current control mode of the motor is analyzed by simulation.On the basis of vehicle longitudinal dynamic model and according to the difference of road adhesion coefficient,three control strategies are designed and applied to the hybrid anti-lock braking control mode,then the force distribution strategy of front and rear shafts in the hybrid braking system is designed.Aiming to achieve the ideal slip rate,the hybrid anti-lock braking control system of the electric vehicle is designed based on the fuzzy PID control method.The hybrid anti-lock braking control model is established,and in order to verify the effectiveness and advancement of hybrid braking,the hydraulic anti-lock braking control model is also established to do comparative analysis.In the single and joint road conditions,simulations of the hydraulic anti-lock braking and the hybrid anti-lock braking are carried out respectively.The simulation results show that: in the high,medium and low adhesion coefficient conditions,the slip rate can be controlled to remain at the ideal value with the two braking modes,but the braking time and distance can be effectively reduced by the hybrid braking mode.On the joint road,the braking time and distance can also be reduced by the hybrid braking mode,and the control effect for slip ratio of hybrid braking mode is better than the hydraulic braking mode.The hybrid braking mode has a good energy recovery function in both the single and joint road conditions.The hardware-in-the-loop simulation test simplified system of hybrid anti-lock braking control is designed,and the theoretical analysis,control strategy and simulation results in this paper are verified.The anti-lock braking tests in low and medium adhesion coefficient conditions are simulated respectively.In the tests,the slip rate can be controlled near the ideal value,and the test results are consistent with the simulation results,which can effectively verify the hybrid anti-lock braking control system designed in this paper.