Stepping motor controller

• US 20030057911A1
• Filed: 09/25/2002
• Published: 03/27/2003
• Est. Priority Date: 09/26/2001
• Status: Active Grant

• Current Assignee: Japan Servo Co., Ltd. (Nidec Corporation)
• Original Assignee: Japan Servo Co., Ltd. (Nidec Corporation)
• Inventors: Kuwano, Yoshifumi, Takemori, Akio, Takahashi, Yukinari
• Granted Patent: US 6,747,433 B2
• Time in Patent Office: Days
• US Class Current: 318/685
• CPC Class Codes: H02P 21/04 specially adapted for very low speeds
• CPC Class Codes: H02P 8/14 Arrangements for controlling speed or speed and torque H02P8/12, H02P8/22 take precedence

Abstract

The controller comprises current sensors for detecting motor currents, an inverter containing a current control means for feeding currents to motor windings, a coordinate transformer that transforms the motor currents in a fixed coordinates system into currents in a first rotational coordinates system, and an angle calculator that transforms a command pulse into a command angle. A second rotational coordinates system composed of a dp axis and a qp axis perpendicular to the dp axis is determined from the command angle. A command current on the dp axis is set to be a value corresponding to a motor current amplitude and another command current on the qp axis is set to be zero. The motor current is projected on the dp and qp axes and controlled so as to make the components on the dp and qp axes coincide with the respective command currents on the dp and qp axes.

Claims

1. A stepping motor controller comprising;

current sensors that detect respective motor currents of corresponding phases,

an inverter containing a current control means for feeding stepped currents to motor windings,

a coordinate transformer that transforms said motor currents in a fixed coordinates system detected by said current sensors into currents in a first rotational coordinates system composed of a d axis being in the direction of a magnetic flux direction and a q axis being perpendicular to said d axis,

an angle calculator that transforms an external command pulse for causing said motor to make a stepping rotation into a command angle,

wherein a second rotational coordinates system composed of a dp axis and a qp axis being perpendicular to said dp axis is determined from said command angle,

a command current on said dp axis is set to be a value corresponding to a motor current amplitude,

another command current on said qp axis is set to be zero,

said motor current is projected on said dp axis and said qp axis,

said motor current is controlled so as to make a component of said motor current on said dp axis coincide with said command current on said dp axis and to make a component on said qp axis coincide with said another command current on said qp axis, and

said motor is caused to make a stepping rotation by rotating said second rotational coordinates system by a predetermined angle at each time when said external command pulse is applied.

2. The stepping motor controller according to claim 1 wherein said stepping motor is a two-phase stepping motor, said fixed coordinates system is a two-phase fixed coordinates system, and said second rotational coordinates system is a two-phase rotational coordinates system.

3. The stepping motor controller according to claim 1 wherein said stepping motor is a three-phase stepping motor, said fixed coordinates system is a three-phase fixed coordinates system, and said second rotational coordinates system is a two-phase rotational coordinates system.