Stuty Of Control Strategy Of Pure Electric Commercial Vehicle Composite Braking System Based On Auxiliay Braking

With the rapid development of new energy automobile industry, the pure electric commercial vehicle becomes heavier and the speed of it becomes faster, thus the load of the braking system of the vehicle also increases. While the drive motor of the pure electric commercial vehicle can recover part of the braking energy to reduce the load of the mechanical brake, the drive motor does not work in extreme braking condition(emergency braking) for the constraints of SOC, vehicle speed, etc. The mechanical brake is affected in these conditions and the brake wear accelerates. In this paper, the composite braking system of the electric commercial vehicle based on the auxiliary braking system not only reduces the brake wear of the mechanical brake and prolongs service life but also improves the vehicle economy to increase the drive range by regenerating the braking energy. The main contents are as follows:(1) The composite braking system of the electric commercial vehicle is studied to analyze the braking dynamics in detail on the braking condition according to the longitudinal dynamics of the vehicle. The distribution of the braking forces on the front and rear axle of the vehicle during the brake condition is researched to confirm the reasonable requirement for the vehicle safety and the braking stability. The braking requirements for different vehicle types and the braking capacity of the braking system on different ramps of all levels of the highway are determined.(2)Three braking control strategies in the existing literature are introduced briefly and the braking requirement is analyzed for different braking conditions. The whole process of the vehicle brake control is proposed through the composite braking system frame which is built on the vehicle frame and braking requirements(security and economy). The distribution control strategy of the composite braking system is developed on the foundation of asynchronous parallel control strategy according to the distribution of the braking force on the front and rear axles through the analysis of complex factors which influences the braking process. The fuzzy logic control is used to determine the proportion of the retarder and the brake motor, and the strategy is divided into six braking modes. Different models have their own operation conditions and the distribution of the braking force.(3) The vehicle model involving the composite braking system is built on AVL / Cruise platform based on parameters of the vehicle and the components in the module according to vehicle dynamics and the characteristics of the related parts on the pure electric commercial vehicle. The braking control strategy is programmed in the Function module and simulated on the platform. The results of the simulation verify the feasibility and practicability of the brake control strategy which is based on the asynchronous parallel mode.