Study on the Algorithm of Active Pressurization Control of Regenerative Braking System in Pure Electric Vehicle 2015-01-2708
During the vehicle braking, the Regenerative braking system (RBS) transforms the kinetic energy into electric power, storing it in the power sources. To secure the baking process, it is required to use hydraulic braking pressure to coordinately compensate the regenerative braking pressure. The traditional hydraulic pressure control algorithm which is used in regenerative braking system coordinated control has obvious laddering effect in braking. Unit control cycle pressure deviations seriously affect the comfort and the braking feeling on the vehicle. In order to ensure the accurate implementation of the brake pressure on the wheel cylinder, according to the hardware configuration of regenerative braking system, this paper analyzes the active pressurization state of RBS during braking, acquires the overflow characteristics of the switch valve in ESP hydraulic control unit by designing of high frequency characteristic test experiment, the control range of valve core displacement in the state of inlet valve differential pressure balanced and the relationship between pressure growing rate and inlet valve control duty ratio under the different states of wheel cylinder pressure. On this basis, this paper finishes the development of algorithm of active pressurization control, building the hardware-in-loop testing platform. The test result shows that the actual wheel cylinder pressure can follow the aiming wheel cylinder well, the differential of wheel cylinder can be controlled in the range from −5Bar to 5Bar, the whole pressurization rate follows well compared with traditional control algorithm, justifies the feasibility of the active pressurization control algorithm through the virtual cycle.