Abstract: The key for the shifting control of the dual clutch transmission (DCT) lies in the coordination control between the engine and the double clutch, and the accurate closed-loop control of torque transmitted by each clutch as well as the output torque of the engine, and the implementation and the control precision of the clutch torque closed-loop control is completely dependent on the effectively real-time estimation of the clutch torque. As for the six-speed dry dual clutch transmission (DDCT), the shifting control strategy is made based on the dynamical model of the DCT, and the vehicle drag torque is estimated on the basis of the recursive least square with dual forgetting factors accounts for different rates of change for different parameters, and the angular acceleration of the engine and the output shaft is refactored utilizing the high order sliding mode observer algorithm. The clutch transmitted torque is estimated using the unknown input observer. The shifting process of the DCT vehicle is simulated on the basis of the self-designed DCT dynamical test bench, and the clutch torque estimation algorithm is validated based on the sliding mode observer as well as the unknown input observer. The simulation and the experiment results show that the proposed sliding mode observer and the unknown input observer could estimate the clutch torque effectively, and lays the foundation for subsequent real vehicle control strategy development.

Key words: clutch transmitted torque estimation, hardware in the loop test, high order sliding mode observer, six-speed dry dual clutch transmission