Parameter Design of a Parallel Hydraulic Hybrid Vehicle Driving System Based on Regenerative Braking Control Strategy 2019-01-0368

With the advantage of high power density and low cost, hydraulic hybrid vehicle has a great potential to reduce energy consumption and vehicle emission of city used medium duty vehicle, such as bus and refuse collection vehicle. Tailored system parameters and suitable energy management strategy are vital to improve the vehicle performance. This paper aims to select and optimize the hydraulic driving system parameters and design energy management strategy for a parallel hydraulic hybrid vehicle. The vehicle working conditions and hydraulic system characteristics are analysed. Power, torque and speed demands during typical cycles are analysed, which is used to select and optimize the hydraulic system parameters. Mechanical braking and hydraulic braking are jointly used during braking. The regenerative braking strategy is designed considering energy recovering efficiency and safety requirements. Due the proportional relationship of hydraulic pressure and hydraulic motor/pump output torque, the hydraulic accumulator working pressure is designed based on vehicle braking requirement. The hydraulic driving system has relatively low energy density, so it is mainly used to start the vehicle and recover braking energy. A rule based energy management strategy is designed to allocate engine and hydraulic motor driving torque. The energy efficiency benefit of the designed hydraulic hybrid vehicle and the effectiveness of the energy management strategy are verified by simulation analysis.