Automatic Transmission Vehicle Research Articles

Prediction of wet band brake dynamic engagement behaviour Part 2: Experimental model validation

A wet (oil-lubricated) band brake in a vehicle automatic transmission system exhibits widely varying engagement behaviour under different operating conditions. In recent years, analytical evaluation of the band engagement behaviour has become increasingly important to improve automatic transmission shift quality. Thus, a mathematical tool which accurately captures band engagement physics is indispensable in a transmission design process. This paper describes experimental validation of the dynamic band engagement model which includes the physics of squeeze film, asperity deformation, porous oil diffusion, heat transfer and loading pressure distribution caused by a selfenergizing mechanism. The model is implemented as a stand-alone computer program to predict the band engagement behaviour on an inertia absorption type band engagement test stand. Simulation results show good agreement with experimental torque profiles over a wide range of operating conditions. The model provides an analytical interpretation of the widely varying engagement behaviour resulting from the effects of oil temperature, friction material permeability and drum speed. The successful model validation demonstrates that the dynamic band engagement model serves as a valuable tool to assist band design and shift calibration processes of automatic transmission systems.

Estimation of turbine torque using an adaptive nonlinear observer for closed-loop control of vehicle automatic transmissions

This paper presents an adaptive sliding observer-based method for the estimation of turbine torque. The estimations of turbine torque can be used in the closed-loop control of vehicle power train for better shift quality. A sliding observer structure including saturation functions and boundary layers is applied to adapt torque converter parameters. The proposed method has been investigated via simulation and laboratory experimental studies. It has been shown via simulation and experiments that the proposed methodology is promising for the estimations of turbine torque since it uses only inexpensive angular velocity measurements and is not sensitive to parametric uncertainties.

Simulation of Gear Shift Operations in Automatic Transmission

This paper deals with the dynamics and control of vehicle automatic transmissions. In order to get realistic predictions about the system behavior during the gear shift operations, the models of all drive train components are presented. Particular attention is paid to the detailed description of the electronically hydraulically controlled wet-clutches.