Energy-Oriented Torque Allocation Strategy Design of 4WID Electric Vehicle Using Slope Information 2019-01-0461
Abstract: The paper proposes an energy-oriented torque allocation strategy to reduce the energy consumption of four-wheel independent driving (4WID) electric vehicle (EV). The dynamic model of this 4WID EV is built up firstly. The chassis structure of the 4WID EV is studied. The EV uses four identical in-wheel motors as the driving mechanism, which are located in the wheels and electrically connected to the inverter and DC-DC converter. The whole vehicle system is powered by the battery. To compute its energy efficiency accurately, the measured efficiency map is fitted by the cubic spline interpolation method. The energy-oriented torque allocation strategy is designed by minimizing the energy consumption during vehicle driving and braking. According to the change of torque and speed required, the torque of front and rear axle cab be allocated dynamically by using the torque allocation coefficients. To ensure the high efficiency of motors and reduce the energy consumption caused by current shock, the torque allocation coefficients are obtained from two kinds of sub strategies. A fuzzy logic controller is designed to combine the derived torque allocation coefficient above, by adopting Mamdani structure with 2 inputs and 1 output. It is validated by simulating under driving cycles and the roads with up-down slopes. Simulation results of driving cycles show that the proposed strategy can dynamically distribute the front and rear axle torque at different velocities, reducing the energy consumption compared to the strategy with average torque distribution. By using the road elevation information and driving cycles, the energy-efficient optimal torque allocation strategy can reduce the vehicle energy consumption by 4% compared to the strategy with average torque distribution.
Key Words: 4WID electric vehicles, torque allocation, motor efficiency, function fitting.