An Improved DTC for In-wheel BLDC motors in Micro All-electric Vehicles

The micro all-electric vehicle pertaining to this study is rear-driven, with motors in the left and right rear wheels. The motors are brushless dc (BLDC) using Hall effect sensors with a trapezoidal back-electromotive force. The control system is developed by using a digital signal processor. To thoroughly utilize the fast torque generation feature of BLDC motors, direct torque control (DTC) is preferable, but with conventional DTC, dead-time must be added. This paper proposes an improved DTC, where the switching device operating principle is equivalent to that of a unipolar pulse width modulation (PWM) technique named PWM-ON. Dead-time is not required, and switching losses are reduced. Further analysis showed that under the improved DTC the dc supply took up only the load current, confirming that there was no return of load energy to the dc supply, which protects the batteries. Experimental results are given to confirm validity.