A disturbance-compensation-based sliding mode control scheme on mode switching condition for hybrid electric vehicles considering nonlinear backlash and stiffness

In this study, a coordinated control problem of power sources and actuators of a series-parallel hybrid electric vehicle on mode switching condition is addressed. There exist numerous nonlinear factors in the hybrid driveline system which induce system disturbance and will deteriorate the control performance on mode switching condition. However, coupled system nonlinearity is not taken into consideration for controller design on mode switching condition, which can lead to severe driveline oscillation and thus vehicle longitudinal jerk. For this reason, a disturbance observer and compensation method is introduced to resolve the control problem on mode switching condition. First, an analytic model of driveline torsional vibration considering disturbance brought by system nonlinearity is established and simplified for controller design. Based on the simplified model, a disturbance observer-sliding mode control strategy is proposed to suppress mode switching vibration. Numerical simulation is carried out to validate control performance of the DOB-SMC strategy. Simulation results demonstrate that DOB-SMC strategy has better ability to cancel the unwanted effects of disturbance brought by system nonlinearity compared with sliding mode control method, which can be regarded as an effective approach to attenuate vehicle longitudinal jerk and thus improve ride comfort on mode switching condition.