| With the challenges of energy and environment issues, battery electric vehicle isconsidered to be one of the solutions in the transportation field due to its advantages inhigh efficiency and zero emissions. Four in-wheel motors drive electric vehiclesimplifies the transmission system, increases the interior space and makes the vehicledynamics control flexible, which will be well accepted by the market. The permanentmagnet brushless hub motor and its control are the critical power units of the microelectric vehicle. The power, economy, security and comfort characteristics of the electricvehicle are directly related to the electric drive system. Therefore, it is of importanttheoretical and practical significance to study the permanent magnet brushless hubmotor and its control. Based on the characteristics of the back EMF in the PM brushlesshub motor, this dissertation focuses on the field oriented control, multi-mode controlstrategy and the energy optimal control for the EV.Firstly, three hall-effect position sensors were installed in the main magnetic circuitof the hub motor and the rotor position detected by the hall-effect position sensors isinfluenced by the armature reaction magnetic field. The analytical technique is used topredict the instantaneous magnetic field distribution in the air-gap region. Experimentsare also designed to verify the sensor detection phase offset, and a valid compensationmethod is developed. Accordingly, the influence of phase offset on the electromagnetictorque and its application value in detecting permanent magnet state are presented.Secondly, as the back EMF of the permanent magnet brushless hub motor is nearlysinusoidal, the field oriented control method is studied to minimize the torque ripple. Afeedforward controller is developed to eliminate the instantaneous great torque changeof the motor and the dead time compensation is added to reduce the torque ripple. Thenoise in the driving cab is also reduced to meet the comfort requirements of the EV.Combined with the traditional six-step block commutation control characteristics, theswitching between the six-step block commutation open-loop or closed-loop control andfield oriented control is studied and then a multi-mode control strategy for the EV isproposed to meet the complex automotive conditions. The proposed methodology isverified by vehicle tests. Finally, the efficiency model of the hub motor in FOC, the efficiency model of theinverter in SVPWM and the equivalent circuit model of the battery are studied.Combined with the kinetic parameters of the EV, the global optimal regenerativebraking control in coasting mode and the instantaneous optimal regenerative brakingcontrol under three different braking force distribution strategies in normal brakingmode are investigated. Then, the energy optimal acceleration control and the optimalmileage are studied, which were defined as the minimum battery output energy for unitkinetic energy and the minimum battery output energy for unit mileage, respectively.The analytical and dynamic programming methods are used to solve the two problems,respectively. The bench and real road tests have verified the analysis. |
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