Research On The Variable Speed Ratio Power System Based On DC Motor

The new energy vehicle has been vigorous development as the oil of increasingly stringentscarce, rising fuel prices and increasingly stringent emission regulations. The major vehicleenterprises and research institutions have pay attention to the electric vehicle which has beenlooked as an important solution of the new energy vehicle. Compared with traditional internalcombustion engine, the motor in electric vehicle is more suitable for vehicle operation withwide speed range, low speed-high torque characteristics.The low-speed electric vehicle power-driven system is consist of the electric motor andfinal drive nowadays, which meets the basic requirements, but there are some weaknesses likeclimbing capability, accelerating performance and range of application which are not reach ourrespects, so the electric vehicle still needs variable-speed power-driven system. Based on theseweaknesses, the present paper comes up with an automatic transmission with two gears suitablefor the electric vehicle, which the first gear is applied to the climbing and accelerating operationconditions, while the second gear is applied to the high-speed operation condition. To reach theoptimization of economic and dynamic performance, we control the automatic conversionbetween two gears by electric control system. The main content of this article contain thefollowing aspects:1、We chose a kind of low-speed electric vehicle as the original vehicle model and madethe analysis and research on the vehicle power-driven system. We did the bench test to obtainthe parameters of the motor. We got the economic and dynamic indexes by the simulation withthe CRUISE software according to the bench test data. We compared the indexes which gotfrom simulation results with the original vehicle’s to verify the validity of the simulation.2、We added an automatic transmission with two gears between the motor and final drivein original vehicle model, and we did the optimization of the transmission ration, research onthe automatic transmission shift schedule, the simulation about the economic and dynamicperformance based on the CRUISE software platform, and compared with the original vehicleeconomic and dynamic indexes to verify the rationality of the automatic transmission.3、We got the sample of the automatic transmission by structure designing and processingaccording to the transmission ratio got by simulation. We chose the Freescale MC9S12XDP512as the main control chip and designed and debugged the control system of the automatictransmission.4、The power-driven system consists of the motor and automatic transmission wasinstalled on the bench, and tested the indexes of the economic and dynamic performance which compared with the original vehicle’s.According to the experiment results, the power-driven system can improve the EVdynamic and enlarge application range, so it is worth to promote.