Sensorless control of single-inverter dual-motor ac brushless drives

The paper deals with the vector control of two surface-mounted permanent-magnet (PM) synchronous-motors in configuration “single-inverter dual-motor”, operating also with unbalanced loads. Since this structure is justified by the objective of obtaining low cost drives, a low computation burden sensorless method is proposed in order to further reduce the system complexity. A very simple algorithm for position/speed estimation coupled with a hybrid adaptive Phase-Locked Loop is indeed sufficient to achieve satisfactory results also in heavy transient operations. Furthermore, a novel control strategy is conceived with reference to an “equivalent” motor, whose rotor position is the average of the separately evaluated positions of the two PM motors. The proposed control technique is validated by an extensive numerical campaign.