Experimental study on improvement in the shift quality for an automatic transmission using a motor-driven wedge clutch

Abstract

Electrification technology is becoming increasingly popular in the actuation system of modern vehicles. A novel wedge-clutch-based actuation system driven by a motor is developed. The wedge clutch, which features a self-reinforcement function, can apply a large normal force on the clutch plates while requiring a small motor torque. However, the self-reinforcement feature results in a different dynamic behaviour of the vehicle driveline; therefore, careful control is needed during clutch engagement. A detailed analysis is performed to describe the different challenges of a wedge clutch in comparison with those of a conventional clutch. Based on the integrated engine and transmission control method, a new method of combined control of the motor actuation torque and the engine torque is proposed to improve the shift quality. The proposed control method is validated on a specialized transmission dynamometer by emulating the change from first-gear power to second-gear power in upshift vehicle conditions. The experimental results present how the shift quality of the wedge clutch is improved significantly by introducing the control method. Not only is the maximum transmission output torque about 25.5% smaller, but also the slipping energy is reduced by about 35.1%, which contributes to a smaller temperature rise on the clutch plates. Also, the smaller motor actuation torque has the potential to downsize the electric actuator further and to decrease its power consumption.