| 摘要 |
A system for controlling draw on a moving web, and in particular, a system for maintaining a constant tension in a moving web to control the link of web moving past a cyclicly operating apparatus in a printing press by controlling the angular position of an upstream roll relative to the angular position of the printing units. By maintaining a constant tension, one webs exiting the two rollers of a printing press, link variations are controlled and lengthwise registration between respective webs is maintained. The tension of the web is sensed, and the angular position (as opposed to angular velocity) of the two roll is controlled in accordance with the sensed tension. A system for controlling the angular position of a shaft employing phase lock group techniques is also disclosed. A single indicative of the actual angular position of the shaft is generated by phase shifting a signal from a reference signal by an amount proportional to the angular position of the shaft. A signal of predetermined phase with respect to the reference signal is generated to indicate the desired position of the shaft. By deviation in phase of the phase shifted signal from the desired position signal is then employed to develop a control signal to effect adjustment of the angular position of the shaft. The signal indicative of the angular position of the shaft may be generated by generating a magnetic field in accordance with the reference signal, and rotating a coil in the magnetic field in correspondence to the rotation of the shaft. A control signal in which a single knob is utilized to control a large number of parameters is also disclosed.
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