Estimation of the clutch pressure basing on reduced order model of the hydraulic actuator system

The precise control of corresponding clutch pressures is essential to the gearshift quality of vehicle transmissions. The electro-hydraulic clutch-actuator system is widely utilized by vehicle transmissions because of the character of fast response and accurate pressure regulating capability. However, due to the structure of vehicle transmissions, pressure sensors are hard to be mounted to measure the clutch pressure during the shifting process directly. An observer method basing on the reduced order dynamic model of the hydraulic clutch actuator system and the Unscented Kalman Filter (UKF) method is proposed in this paper to ensure a stable and precise control of the clutch actuator system. The reduced order non-linear dynamic model of the clutch actuator system is established basing on the flow distribution character and coupling motion of the valve spool in the system. A state observer is proposed to estimate the clutch pressure online using the output pressure signal of the pressure control valve based on the UKF method. Simulations and experiments are carried out to verify the proposed clutch pressure observe method. The results reveal that the reduced order dynamic model can predict the pressure dynamics inside the hydraulic system accurately and the observer can ensure the estimate accuracy of clutch pressure during the shifting process.