Design And Study Of A New-Ttype Hybrid Powertrain Based On Two-stage CVT

Faced with an increasingly serious energy and environmental problems, the more environment-friendly new energy vehicles have accounted for a growing market in the automotive industry. As a transition vehicle from traditional vehicle to pure electric vehicle, hybrid electric vehicles are more and more popular with its good dynamic performance, economic performance, emissions performance.There are two power sources in hybrid powertrain, one is internal combustion engine and another is electric traction motor. How to arrange the traction motor directly affects the vehicle’s dynamic and economic performance. A new-type hybrid powertrain is designed in this paper which combines a two-stage CVT transmission with a electric traction motor, and some feasible schemes of this design are proposed. Based on this scheme, some studies below are carried out.(1) The structure and characteristics of two-stage CVT transmission are analyzed. Based on this two-stage CVT powertrain, four feasible schemes of hybrid powertrain are proposed. The options for launching device and traction motor are analyzed and a most feasible scheme is determinedand. The working mode of new-type hybrid powertrain and working state of corresponding shift actuator are analyzed. The coordinated working state of two variators when they are working together is analyzed;(2) Through a comparative analysis of the existing vehicles which are equipped with two-stage CVT transmission, a prototype vehicle is determined. Combined with the relevant design standards of hybrid electric vehicle, and to ensure the dynamic performance, design requirements of new-type hybrid powertrain are put forward. The powertrain parameters were matched based on design requirements. The three-dimensional parameters of key components in powertrain are determined and a 3D concept model is set up on the platform of UG with 1:1 scale.(3) According to the structural and operating characteristics of new-type hybrid powertrain, a logic threshold control strategy is put forward in order to increase the economic performance, including internal combustion engine control, traction motor control, battery system control, CVT ratio control, auxiliary transmission gear mechanism control, regenerative braking force distribution control and the mode switching control etc. According to the working principle of powertrain and control strategies, a whole vehicle simulation model and control system model are established on Matlab / Simulink platform.(4) According to the vehicle model whice is established, the dynamic and economic performance simulation of new-type hybrid powertrain are carried out. The correctness of the simulation model and the rationality of control strategy are verified. Four typical driving cycles are chosen to do the economic performance simulation and simulation results were compared with the first-generation Toyota Prius which has nearly the same function and class of what designed on this paper. It is showed that the design of the new-type hybrid transmission based on two-stage CVT not only has much improvement compared to the prototype vehicle, but also has advantages over first-generation Prius on all aspecets. It is proved that the development of hybrid potertrain which is designed in this paper is very valuable.