| 摘要 |
A belt driving unit includes a rotary belt on which a scale is formed, a sensor that reads the scale, a normal-position control loop that detects an actual position of the rotary belt based on information of the scale read by the sensor, and corrects a position of the rotary belt based on the actual belt position detected, an abnormal-condition control loop for a situation when an abnormality occurs in the normal-position control loop, and a loop-switchover timing controller that controls a switchover timing of a control loop between the normal-position control loop and the abnormal-condition control loop.
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