| 摘要 |
A control apparatus controls retraction of a device carried on a moveable member actuated by an electric motor after a sudden power loss. The control apparatus includes a measuring circuit for measuring a back electromotive force (back EMF) from the electric motor during a measuring phase. The control apparatus also includes a controller which receives the actual velocity and provides a command signal for controlling a magnitude of the drive current based on a commanded velocity and the actual velocity of the moveable member. The control apparatus further comprises a current control loop for providing a command current signal based on the current provided to the electric motor and the command signal, and for providing the electric motor with the drive current during a driving phase based on the command current signal.
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