Research On Anti-rollover Control Of A Four-wheel-independent-drive Electric SUV

Equipped by in-wheel motors with quick,accurate,and flexible torque generations,Four-wheel-independent-drive electric vehicles(FWID-EVs)have obvious advantages in terms of energy optimization and driving safety,and have capacious market future.However,at present,there are some difficulties in the research of FWID-EV,such as the increase of unsprung mass and CAN Network with time-varying delays.In this paper,Firstly,for the increase of unsprung mass,a multiple degrees of freedom vehicle dynamics is established.The effects of unsprung mass on vehicle rollover stability are studied.Then a hierarchical controller is proposed based on the distribution of the four wheels driving torques with sliding mode control.Secondly,for the CAN network with time-varying delays,a control-oriented model with time-varying delays is established,a fuzzy sliding mode controller is designed to eliminate time-delay.Finally,the rollover stability of the active rollover prevention control system are analyzed in Simulink/CarSim on different roads.The main contents contributions are as follows.(1)A FWID-EV model is established.For the four-wheel independent drive characteristics of FWID-EV,the 8-DOF dynamic model including 4-DOF of body,4-DOF of wheel rotation,driver model,motor model and other subsystem models are established.The FWID-EV model is built in Simulink/CarSim.The model is verified by comparing with CarSim model.(2)The influence of the increase of unsprung mass on the rollover stability is analyzed.The rollover index for uneven roads is determined.The rollover index is verified by simulations in Simulink/CarSim.The rollover stability of FWID-EV with different unsprung mass under even and uneven roads is analyzed,the relationship between the unsprung mass and the rollover stability of the vehicle is obtained.(3)A hierarchical control strategy architecture for FWID-EV is proposed.According to the rollover stability rules of FWID-EV,the yaw rate and slip angle are chosen as control targets in the upper controller.The multi-object control strategy is designed applying the theory of sliding mode control.The lower controller includes the optimal torque distribution strategy.Through the simulation analysis of typical working conditions,the proposed controller can effectively improve the anti-rollover stability of the FWID-EV,and the multi-object control method has better anti-rollover control performance than single-objective control.(4)The anti-rollover control strategy of FWID-EV with CAN network-induced delays is studied.A 3-DOF control-oriented rollover model with time-varying delays is established,a fuzzy sliding mode controller is designed to eliminate time-delay.Through the analysis of simulation results,it is concluded that CAN network-induced delays will cause interference to the system,and the system jitter will tend to be unstable.The effects of CAN network-induced delays on rollover stability can be well avoided with the fuzzy sliding mode controller.