Robust Speed Synchronization Control for an Integrated Motor-Transmission Powertrain System with Feedback Delay

Motor speed synchronization is important in gear shifting of emerging clutchless automated manual transmissions for battery electric vehicles (BEV) and other kinds of parallel shaft-based powertrains for hybrid electric vehicles (HEV). Difficulties of the problem mainly come from random delay induced by network communication and unknown load torques from air drag, oil drag, and friction torques, etc. To deal with these two factors, this paper proposes a robust speed synchronization controller based on act-and-wait control and disturbance observer. The former is a kind of periodical controller specially for regulating problems with feedback delay while the latter is a technique for active disturbance rejection. Firstly, the dynamic model of the motor shaft is formulated, and the system parameters are offline identified. The speed tracking problem is then transformed into a regulating one. The act-and-wait control law for the nominal model is proposed regarding the new model after transformation. Determination of controller parameters and their relationship with the speed synchronizing process are discussed. After derivation of the nominal controller, a time-domain disturbance observer is integrated to enhance robustness. Effects of different controller parameters are studied through simulations. Experiments are carried out on a test bench with the motor-transmission powertrain system. Comparisons with the conventional PI controller are performed regarding transient responses and robustness. Results show that the proposed controller is able to achieve a fast and smooth synchronization process, while the PI controller is faced with the dilemma between overshoot and settling time which cannot be simply solved through parameter calibration. In conclusion, the proposed controller is suitable for motor speed synchronization control in parallel shaft-based powertrains in BEV and HEV.