Adaptive Control of Shifts in Automatic Transmissions

Abstract To compensate for the effects of life-cycle and build-to-build variations on transmission shift quality, the base shift controls in a transmission must be augmented with adaptive controls. This paper describes the development of adaptive control strategies for power-on upshifts and downshifts in electronically controlled automatic transmissions. These control strategies are applicable to both clutch-to-clutch and freewheeler-to-clutch shift technologies. In the case of upshifts, oncoming clutch fill-time, oncoming and offgoing clutch pressures are adapted from one shift to the next, while in the case of downshifts, only the clutch pressures are adapted. The model reference adaptive control approach is used in developing the adaptive logic with the parameter adjustment made using the gradient method. Experimental results are presented to show that these adaptive algorithms are effective in adapting the shift parameters to maintain shift quality at acceptable levels.