| 摘要 |
Apparatus controls the torque applied by a motor to a reel, such as the supply reel of a video tape recorder, so that the tape drawn from such supply reel by a tape transport system is transported with a substantially constant tape tension. The apparatus includes a device for detecting the rotational speed of the supply reel and for generating an output signal, for example, in the form of a voltage the value of which varies with a change in the rotational speed and which has a rate of change corresponding to the rate of the change of the rotational speed. A device receives the output signal from the rotational speed detecting device and generates a motor control signal which varies in response to changes in the output signal, with the relationship of the variation of the motor control signal to the variation of the output signal being dependent upon the rate of change of the output signal. For example, slow changes in the output signal, which correspond to increases in the rotational speed of the supply reel caused by decreases in the radius of the tape wound upon that reel, cause the motor control signal to decrease the torque applied by the motor to the supply reel, while rapid changes in the output signal, which correspond to rapid increases in the rate of rotation of the supply reel caused by motion and mechanical vibration, cause the motor control signal to increase the torque applied by the motor to said supply reel so as to resist such rapid increases in reel speed.
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