Study On Mode-switch Of Hybrid Electric Vehicle Equipped With Electric-mechanical Continuously Variable Transmission

In order to solve the environmental pollution and the shortage of resources,developing the new energy vehicles vigorously has become the main trend. Hybrid electric vehicle have become the most acceptable and the most easily industrialized new energy vehicles because its long endurance mileage, multiple work modes and no high requirements for battery at present. The hybrid power system have at least two power sources, according to the different combination of the two power sources, it produces different working modes. When different working modes switch over each other, working state of all working parts in transmission system will possibly change, it will cause transmission system’s power interruption or torque ripple, and then affect vehicle driving performance. So, we must get on coordinated control during hybrid electric vehicle working mode switching process.This paper relies on National Natural Science Foundation of China, by taking uni-axial parallel hybrid power system equipped with electric-mechanical continuously variable transmission as the research object, it researched on dynamic coordination control strategy when hybrid power system shifting over working mode. The main research works have the following aspects:Firstly, it analyzed structural characteristic of uni-axial parallel hybrid power system and dynamic characteristic of transmission system main parts, respectively established engine 、 ISG motor 、 automatic clutch 、 electric-mechanical continuously variable transmission and other key parts models. Meanwhile, it gave evaluation index of mode switch control strategy.Secondly, it analyzed working mode of uni-axial parallel hybrid power system, and divided working mode into driving mode and braking mode. Mode switching process has been divided into three categories: switching process between driving modes、switching process between braking modes and switching process between driving and braking modes.It gave the two typical driving mode switching process and switching process between driving and braking mode detailed dynamic analysis. According to different mode switching process, coordinated control strategy which comprehensively considered engine、motor、automatic clutch and transmission dynamic characteristic has been carried out.At last, it analyzed the proposed three kinds of mode switching process inMatlab/Simulink simulation platform, and comparatively analyzed simulation results of using dynamic coordinated control strategy or not. It shows that mode switching process with dynamic coordinated control algorithm have smaller degree of shock, and it proved that dynamic coordinated control strategy can improve mode switching quality.