| Concerns about environmental pollution, rapid increase in fuel cost, and depletion of fossil fuel reserves have been the main motivations behind the efforts made by the increasing of the number of cars. In the condition that the key technologies of the pure electric vehicle and fuel cell vehicle have not made a breakthrough, and the fuel economy is limited in the traditional hybrid vehicle, the plug in hybrid electric vehicle which have both the advantages of the pure electric vehicle and traditional hybrid vehicle is popular all over the world. And the regenerative braking is an important function of hybrid electric vehicle distinguish from traditional vehicle. On the premise of braking security, the braking energy can be saved to battery through regenerative braking to achieve the energy recovery in the process of vehicle braking.The focus of this paper is on a plug-in hybrid electric vehicle equipped with CVT, using the characteristics of CVT speed ratio can change continuously, the braking system is operated on the optimal curve by regulation the CVT ratio to maximize the recovery energy of regenerative braking. And the simulated and theoretical researches of dynamic characteristic and control strategy of continuously variable transmission system under the braking condition have been carried out. This paper involves followed content:(1) Based on the analysis of plug-in hybrid electric vehicle equipped with CVT braking dynamics and comparison of the advantages and disadvantages of exited three kinds of traditional braking force distribution strategy, comprehensive consideration the ECE regulations and the operation characteristics of motor, a regenerative braking force distribution control strategy for plug-in hybrid electric vehicle equipped with CVT is proposed.(2) Based on the efficiency characteristic of motor?battery and CVT, a motor?battery and CVT braking system comprehensive efficiency model was built, and the optimal curve of the braking system comprehensive working efficiency is obtained, according to the optimal curve the CVT ratio control strategy was built. The simulation of motor working on the optimal curve only and the braking system working on the optimal curve are carried out under different braking intensity and conditions.(3) The dynamic model of braking process for continuously variable transmission system is established, the dynamic characteristic of continuously variable transmission system in the process of braking under normal control method is analyzed, and the simulation of continuously variable transmission system are carried out under the braking intensity remains constant and braking intensity dynamic change conditions.(4) Based on the analysis of the dynamic characteristic of continuously variable transmission system in the process of braking, a control strategy of motor torque control together with the CVT ratio change rate limit are proposed. Finally, the simulation of the PHEV equipped with CVT is built by the MATLAB/Simulink software under different braking intensity and conditions, and the simulation results verify the correctness and effectiveness of the proposed control strategy. |
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