A Disturbance-Observer-Based Feedforward-Feedback Control Strategy for Driveline Launch Oscillation of Hybrid Electric Vehicles Considering Nonlinear Backlash

Sudden torque change caused by the TM (traction motor) of HEV (hybrid electric vehicle) can lead to severe driveline oscillation, furthermore the backlash between engaging components in the driveline could increase the vibration amplitude. This paper focuses on the driveline oscillation of a series-parallel hybrid vehicle on launch condition. An analytic model of driveline torsional vibration considering disturbance brought by nonlinear backlash is established and simplified for the convenience of controller design. Based on the simplified model, a feedforward control strategy is proposed to suppress HEV launch vibration. However, the control effect will deteriorate sharply with the increase of equivalent backlash in the driveline system. To improve vibration attenuation performance, a feedback compensator is established and incorporated into the control system, with a robust sliding mode observer which is designed to estimate unknown disturbances as feedback signal. Numerical simulation is applied to validate vibration attenuation performance of the feedforward-feedback hybrid control strategy. Simulation results demonstrate that the feedforward-feedback control strategy has better robustness to cancel the unwanted effects of disturbance brought by nonlinear backlash compared with other control methods, which can be regarded as an effective approach to attenuate driveline oscillation and thus improve ride comfort on launch condition.