A sensorless initial rotor position estimation method for two-phase hybrid stepping motors

Stepping motors are used for high precision and low cost positioning motor which can be controlled with no feedback control. So it is used in OA (Office Automation) and FA (Factory Automation) applications. However, because of open-loop control, the motor may rotate in the wrong direction temporarily when it starts. This problem can be resolved through using initial rotor position estimation. To estimate the rotor position, a sequence of voltage pulses is applied to the motor windings when the motor is at standstill, and then the information of rotor position is obtained from a combination of measured peak values of current. In this paper, experimental results of the initial rotor position estimation are presented, and the effectiveness of the proposed method is shown.