Modeling, control, and adaptation for shift quality control of automatic transmissions 2019-01-1129

The parameters determining shift quality control in automatic transmissions are determined as part of the calibration of the transmission control. The resulting control system typically has three levels of control: first, feedforward control, where the controller output is determined before a gearshift, second, feedback control, where the controller output is determined during the gearshift based on sensed feedback, and third, learning control (adaptation), where feedforward or feedback controller parameters are modified after the current gearshift (of low shift quality) has ended and before the next similar gearshift begins. Gearshifts involving the same ratio change are referred to here as similar gearshifts, though such gearshifts may involve differences in other variables such as vehicle speed or engine torque. For automatic transmissions, these gearshifts are primarily controlled by hydraulic clutches, and operating conditions for these clutches may vary widely, requiring a dedicated learning controller. In this investigation, model-based methods are used to accomplish feedforward, feedback, and learning control of hydraulic clutches in automatic transmissions. Towards this end, physics-based models of hydraulic clutches involved in a 2-3 upshift of a production automatic transmission were developed and experimentally validated against test bench experiments for a wide variety of inputs and operating conditions. The resulting model is used to generate a feed-forward controller, a feedback controller, and a learning controller, which uses speed information from the previous similar gearshift to correct the feed-forward control for the next similar gearshift. In particular, parameters of the feedforward controller affecting clutch-fill of the oncoming clutch and load transfer during the torque phase are adjusted by learning control after a low quality gearshift is detected. The effectiveness of the resulting controller is validated by simulation studies using the experimentally validated transmission hydraulic system model.