Silver Seiko Ltd.

Yasushi Ema

Shigeo Kamikura

A driving device for a stepping motor wherein detection of a position of the rotor of a stepping motor can be effected accurately without the necessity of adjustments of various elements. The device detects a current flow in a field winding of an energized phase and compares it with a simulated saturation curve to detect a back EMF induced in the winding to find a current position of the rotor of the motor. The simulated saturation curve is produced by energizing the winding with a low voltage, measuring current flows in the winding as voltage signals at three different points of time, and calculating several data indicating a saturation curve from the voltage signals. The data are stored in memory and recalled one after another to produce a corresponding voltage when the field winding is energized.

Driving device for a stepping motor

A step motor control system which can control a step motor to rotate at a variable high speed like a brushless motor. A position signal indicating a position of a rotor of a step motor relative to a specific one of field windings is detected as a voltage signal which is successively compared with a reference voltage in order to detect a specific angular position of the rotor at which selective energization and deenergization of the field windings are started for a next stepping operation of the motor. The position signal may be extracted as a voltage signal from an electric current flowing through a last energized field winding by a resistor connected thereto. From the voltage signal, a back EMF induced in the field winding due to its self inductance is subtracted to detect a voltage position signal or EMF induced in the field winding by a permanent magnet of the rotor. The back EMF is produced by an electronic simulation means including an integrating circuit having a same time constant with the field winding.

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Kadaira, Japan

Yasushi Ema