Online estimation of operating variables for stepped automatic transmissions

This paper presents the development of a model-based estimator to provide real-time information about important, but unmeasurable, operating variables in stepped automatic transmissions. Specifically, model-based estimation of the transmission output shaft torque and the clutch pressure for each clutch involved in the gear shifting process is presented. Knowledge of clutch pressures and output shaft torque can be used for online diagnostics or development of closed-loop control in order to improve shift quality. In the approach described here, only speed measurements are used, viz, transmission input and output speeds and the wheel speed. The estimation technique used in this paper is based on the sliding mode observer. The performance of the estimation scheme is evaluated by simulation. Analysis of the accuracy and robustness of the proposed schemes is also presented.