Research On Torque Coordination Control Strategies Of HEV Based On Sliding Mode Control

Increasingly serious problems caused by energy crisis and environmental pollution have drawn more and more attention to vehicle fuel consumption and emissions.Hybrid electric vehicles,having the advantages of conventional fuel vehicles and electric vehicles,have shown a good development prospect.The driven system control is one of the key technologies of HEV and has a significant impact on comfortableness and dynamic performances.Fuzzy sliding mode control and model reference sliding mode control are studied to solve the engine and motor torque coordination control problems during mode transition of the single-shaft parallel hybrid electric vehicle.The joint simulation of AVL Cruise and Matlab/Simulink is used to verify the control effect.As the complexity of the hybrid system,the professional simulation software AVL Cruise is used to build the vehicle model.In order to ensure the continuity of the control process,a torque management strategy based on logic rules is established in this paper to solve the problem of when to switch mode and how to allocate the target torque of each power source.The vehicle dynamics model,clutch torque model and vehicle state equations under different driving modes are analyzed,which lays a theoretical foundation for dynamic torque coordination control.In order to reduce the jerk during mode transition,sliding mode control strategies are adopted in this paper.Fuzzy sliding mode control strategy makes the engine side clutch speed follow the motor side clutch speed by controlling the torque of ISG,which has a rapid response,to realize smooth engagement of the clutch.This strategy regards the engine torque error as disturbance and compensates it with the ISG torque.The proposed strategy is compared with conventional methods and the joint simulation results show that fuzzy sliding mode control can achieve smaller vehicle jerk and less clutch frictional losses.The robustness of the proposed strategy is also studied in this paper.The model reference sliding mode control is adopted to control the engine torque and motor torque.This strategy considers the torque coordination problems in the aspect of state equations before and after mode switching.First of all,drawing on the idea of model reference control,the reference model from pure electric mode to hybrid driving mode is built to generate reference speed.Then the desired motor torque and engine torque are obtained by model reference sliding mode control to make the speed of both sides of the clutch follow the reference speed.Therefore,the engagement of the clutch can be more stable.Simulation results show that the model reference sliding mode control strategy can effectively reduce the clutch frictional losses and vehicle jerk,and has good robustness.Besides,the results show that the model reference sliding mode control can achieve less clutch frictional losses and smaller vehicle jerk than the fuzzy sliding mode control.