Study On The Optimization Of Control Strategy For Continuously Variable Transmission

As an ideal transmission variable speed drives for automobile, CVT can make the carachieve the best match of the engine and the transmission in any driving conditions,so canimprove vehicle fuel economy and power performance, reducing emission and has broadprospects for development and market space in China. This paper comes from Jiangsu Provincescientific and technological project, relying on the NAC Institute and test conditions of theentrusted enterprise. This paper involves followed contents:Firstly introduces the development and classification of automatic transmission. Bycontrasting with other transmission technology characteristics, it shows that metal belt CVT is anideal transmission device. So it can meet the current demand for automobile environmentalprotection, energy saving, comfortable and has a broad prospects for development. In this wayelaborates the research significance and the necessity of this project.The overall structure of the metal belt CVT is introduced; the working principle andtransmission line are also expounded. Subsequently，the characteristic of proportional reliefvalve and proportional reducing valve are analyzed which is the core component of hydrauliccontrol system, and lay a foundation for the algorithm design. Under the premise of consideringthe rotating components of CVT and the rotational inertia of the drive shaft and the main reducergear which have effect on the system performance, mathematical model of the drive system isestablished, providing the theory basis for optimizing control strategy in the next chapter.Metal belt CVT control mainly includes the clamping force control, ratio control and clutchcontrol. In the traditional ratio control, the method of determining the target speed ratio is simplybased on the best power performance or optimal economy curve of engine but not both. In viewof this, this article is based on the weighted comprehensive evaluation method to determine targetspeed ratio, which give attention to both economy and power performance of the vehicle.In the clamping force control, first test slip, then through fuzzy controller, realize thereal-time tracking of actual slip rate to optimal slip rate, in order to complete the clamping forcecontrol indirectly. Simulation results show that the clamping force control method which basedon slip can reduce the pulley clamping force imposed from the hydraulic system effectively,relative to the traditional clamping force control method. Besides, the energy loss in thetransmission can be reduced, improve the drive efficiency of transmission, fuel economy and theacceleration performance, and conducive to the more extensive application of CVT.During the realization of the clutch control, to make the vehicle start smoothly, the jerk and dissipated energy are considered comprehensively. Based on quadratic performance, the processof the slipping and friction of the clutch is realized.Combining with this topic, the V model development process of CVT control system isintroduced focused on the RCP platform test, the development of vehicle controller and road test.With the input and output interfaces of ControlBase_D in the MATLAB environment, integratemodel with control strategy, generate automatic code, so as to realize rapid control prototype. Thecontrol system is implemented on the Zotye and road tests are carried out. The results show thatthe designed control strategy can meet the requirements of ratio control and clamping forcecontrol for CVT. The performance of the car was very good. The test result can meet the aim well.Overall, the power performance and fuel economy is better than the traditional control, and thesimulation model can be better fit.