Adaptive control of hydraulic shift actuation in an automatic transmission

Abstract

A low-order dynamic model of a clutch for hydraulic control in an automatic transmission is developed by separating dynamics of the shift into four regions based on clutch piston position. The first three regions of the shift are captured by a physics-based model and the fourth region is represented by a system identification model. These models are determined using nominal values and validated against nominal and off-nominal experimental data. The model provides two lumped flow parameters to be used for tuning to the desired hydraulic clutch system. Using feedback information from the model and transmission mechanicals, a closed -loop adaptive controller is designed. The controller is structured to update at three different rates: every time instance, every shift, and every n-th number of shifts. Part of the controller is designed to operate in open-loop for the first two regions of the shift until feedback information is available. The open-loop controller adapts within the shift, thus allowing for corrections to the control design to be made in following shifts. The model tuning parameters as well as the main spring preload become the adaptive parameters, which are then adjusted so that the plant matches the model. The control design is validated against a high fidelity simulation model of the transmission hydraulics and mechanicals.