| 摘要 |
A speed control circuit and position control circuit are connected to a spindle drive motor in a machine tool or the like in order to drive the spindle at a predetermined speed and stop the spindle at a predetermined angular position. When an orientation command is issued while the spindle is being rotated at the predetermined speed by a speed control loop, a speed command signal from a speed command circuit is interrupted, the speed reduced to zero, and an initially set voltage is then employed as a speed command to rotate the spindle by a predetermined amount. Next, a integral value of the actual spindle speed is employed as the speed command to further rotate the spindle by a predetermined amount. When this has been accomplished, a constant bias voltage of a low level replaces the speed command, thereby to rotate the spindle still further by a predetermined amount until a specified portion of the spindle approaches extremely close to the predetermined angular position. At this point a signal, sensed by a magnetic body provided on the specified portion of the spindle and a sensing circuit confronting the magnetic body, is employed as the speed command signal of the speed control circuit, the sensed signal having a gradually decreasing waveform which attains a value of zero when the specified portion of the spindle is stopped at the predetermined angular position. Using this signal gradually decelerates the spindle motor to stop the spindle accurately at the desired angular position.
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