A Reduced-Order Nonlinear Clutch Pressure Observer for Automatic Transmission

For a novel type of automatic transmissions adopting clutch-to-clutch shift control technology with electro-hydraulic actuators, a clutch pressure observer method based on input-to-state stability (ISS) is proposed. Model uncertainties including steady state error and unmodelled dynamics are considered as additional disturbance inputs and the observer is designed in order that the error dynamics is input-to-state stable. Lookup tables, which are widely used to represent complex nonlinear characteristics of engine systems, appear in their original form in the designed reduced-order observer. The designed pressure observer is tested on an AMESim powertrain simulation model. Comparing with the sliding mode method, the designed pressure observer has the better performance.