| 摘要 |
If an excessive mechanical resistance is encountered upon adjusting the control element, esp. if jamming occurs, the control element is subjected to a periodic vibration to overcome the resistance. Jamming can be detected form an increase in thedifference between a demanded and an actual value. The control element is returned to a rest position by a spring when not being driven. When being vibrated the element is driven periodically at a low frequency pref. close to its resonant ferquency. If a two-coil rotational control element is involved, it is vibrated by driving the coils alternately.
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