Speed Ratio Control On Metal-Belt CVT System In Power Off

The best match of the engine and the vehicle load can be implemented bycontinuously variable transmission (CVT) over a large area, and then the fuelconsumption was reduced. There is no shift shock, and then the driving comfort can beimproved. Therefore, CVT is considered to be the ideal transmission for a vehicle, inwhich the metal-belt CVT has been proven to be the most promising form.Control strategy is an important research area of the CVT technology study. Interms of working conditions, current research focuses on the driving conditions toachieve optimal performance. Control strategy for zero throttle opening is less involved,sporadic, unsystematic and not practical. In this paper, the CVT speed ratio controlstrategy was developed based on the analysis of the intention of the driver. The researchcarried out mainly from the following aspects.①The industry history of CVT was summarized both at home and aboard. Thebasic structure and working principle of CVT system was introduced. And the presentresearch status of CVT technology was described.②The modeling process of CVT vehicle components and the entire vehicle wasintroduced. The method to find the optimal operating point of the engine was provided.The control strateyg of mechanical throttle vehicle and electronic throttle vehicle weredescribed, under the driving condition of steady state and transient.③Engine braking characteristics was obtained according to the experimental data.The CVT speed ratio control strateyg to using engine braking under the downhillconditions was analysed. The velocity maintains range was analysed considering thespeed ratio limit of CVT and restrictions of engine speed.④The working condition of power off was subdivided according to the drivingoperations and road conditions. And the corresponding control strategies for eachsubdivision conditions were developed considering the driving intention. The method ofconditions identifies and control strategies selection was developed in accordance withthe control program execution process. The implementation of the system was testedand verifed by simulation using MATLAB/Simulink.