A Three-Phase Hybrid Stepping Motor Drive System Combined with Position-Sensorless Closed-Loop Control

This paper proposes a drive system for a three-phase hybrid (HB) stepping motor, combining sensorless closed-loop control with conventional open-loop control. It is characterized by the sophisticated control providing both prevention of pulling out from synchronism and suppression of rotor natural oscillation, without any position sensor attached to the motor shaft. Switching technique in chopper control is described, which can enlarge a speed range controllable in the sensorless closedloop control. Moreover, starting and stopping sequences are developed to reduce mechanical natural oscillation caused in transient state. Finally, the proposed drive system is compared with a conventional constant-current open-loop drive system experimentally. It is shown that the proposed drive system can perform a switchover from the starting to the sensorless closed-loop operation within 20ms, and can reduce the natural oscillation caused just after positioning.