Regenerative braking provided by an electric powertrain is far different from conventional friction braking with respect to the system dynamics. During regenerative decelerations, the nonlinear powertrain backlash would excite driveline oscillations, deteriorating vehicle drivability and blended brake performance. Therefore, backlash compensation is worthwhile researching for an advanced powertrain control of electrified vehicles during regenerative deceleration.
In this study, a nonlinear powertrain of an electric passenger car equipped with a central motor is modeled using hybrid system approach. The effect of powertrain backlash gap on vehicle drivability during regenerative deceleration is analyzed. To further improve an electric vehicle's drivability and blended braking performance, an active control algorithm with a hierarchical architecture is studied for powertrain backlash compensation. Since the backlash in driveline is unable to be measured by a sensor, a high-level hybrid observer for backlash identification is designed at first. Then, based on the observation of the backlash traverse, a low-level switching-based active controller for powertrain backlash compensation is synthesized.
The proposed control algorithm is simulated and compared with a non-active baseline strategy under regeneration deceleration. The simulation results show that the nonlinear powertrain backlash is well compensated by the developed active control algorithm, and the vehicle drivability and blended braking performance are also significantly enhanced.
