Active motor damping strategy for driveline vibrations of a hybrid electric vehicle during ABS operation

Torsional drivetrain vibrations in hybrid and electric drivetrains, which occur during traction and braking control, are commonly encountered. This problem occurs mainly due to the weak damping characteristic of the hybrid/electric drivetrain and the fast time response characteristics of the electric motor. An active motor damping (AMD) control algorithm for a hybrid electric vehicle, considering ABS braking maneuvers on different road conditions, is developed in this work. The control problem is structured such that the control objective is disturbance rejection against the estimated brake torque signal received from the ABS module. Communication delay between the ABS and motor control module is handled within the control strategy. State feedback control strategy is used with the linearized version of the non-linear state-space equations together with an Extended Kalman filter. Gear backlash is taken into account without the need to estimate the mode of backlash. In the development of the controller, state feedback gains are set such that the ABS functionality on tire slip regulation is not altered. Existing studies in the literature feedback only the angle of twist and axle wrap angular speed for damping the vibrations. The structure of the controller in this study is different in that it estimates and feeds back tire slip, in addition to these two. Simulation results show the effectiveness of the controller in reducing the angle of twist without deteriorating ABS tire slip control and braking performance of the vehicle.