Research On Slipping Control Of Torque Converter Clutch At Launching Conditions

With the advantages of mature technology and smooth shifting, Automatic Transmissionoccupies a dominant position in the transmission family, but the low transmission efficiencyis its main drawback because of torque converter. In order to improve the transmissionefficiency, torque converter clutch is installed between the pump and turbine of torqueconverter, and then the transmission efficiency was improved effectively through thechanging power transmission mode. Slipping control of torque converter clutch at launchingconditions was proposed based on the characteristics of launching conditions, and problemsof feasibility, working zone division, control objectives optimization and control algorithmswere solved. The main contents are as follows:1) Vehicle dynamics model: The vehicle dynamics model of POLO car with AT wasestablished, especially the torque converter and lockup clutch coupling power transmissionmodels and lockup clutch torsional vibration model were built.2) Predictions of torque converter dynamics characteristic: Based on Hrovat andTobler’s description equations of the torque converter, the dynamic characteristic of torqueconverter was predicted at launching conditions. The perdition results provided a basis fortorque prediction when the implementation of slip control.3) The temperature characteristic of torque converter clutch friction plate: Variation ofthe temperature characteristic of torque converter clutch friction plate was simulated withchanges of slipping speed; the feasibility of torque converter clutch slip control because offriction plate bearing temperature was verified. Based on temperature prediction model, thetorque converter clutch model was amended.4) Torsional vibration of transmission system: The torsional vibration modelof transmission system was established and the torsional vibration characteristicof vehicle under the existing torsion damper was researched. Using regression toestablish natural frequency recursive equation of transmission system and make slipping control demand of torque converter clutch through the optimization of torsional vibrationdamper stiffness.5) Slipping control region selection and slipping speed optimization: According tothe different power requirements when starting, the slipping control region was determined.The zero slipping speed was detected and the corresponding slipping speed recovery strategywas proposed. The slipping speed was optimized taking the Torque fluctuation andtransmission efficiency as evaluation target.6) Research on slipping control algorithm: The control oil pressure at different stages ofslipping control was optimized based on fuzzy control. The characteristics of shock responseand vibration was analyzed at the first stage, also called oil filling stage. In order to validatethe effect of slipping control of torque converter clutch at launching conditions, realcar benchmarking was done.