A Control Strategy for Four-Switch Three-Phase Brushless DC Motor Using Single Current Sensor

A control strategy based on single current sensor is proposed for a four-switch three-phase brushless DC (BLDC) motor system to lower cost and improve performance. The system´s whole working process is divided into two groups. In modes 2, 3, 5, and 6, where phase c works, phase-c current is sensed to control phases a and b, and phase-c current is consequently regulated. In modes 1 and 4, the combination of four suboperating modes for controlling phase-c current is proposed based on detailed analysis on the different rules that these operating modes have on phase-c current. Phase-c current is maintained at nearly zero level first, and phase- a and phase-b currents are regulated by speed circle. To improve control performance, a single-neuron adaptive proportional-integral (PI) algorithm is adopted to realize the speed regulator. Simulation and experimental systems are set up to verify the proposed strategy. According to simulation and experimental results, the proposed strategy shows good self-adapted track ability with low current ripple and strong robustness to the given speed reference model. Also, the structure of the drive is simplified.