Importance

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Abstract

Apparatus is disclosed for controlling the movement of a movable element to bring the movable element to rest at a desired stopping position. The apparatus comprises a multi-phase drive motor having a drive shaft coupled to the movable element for driving same, four electrically conductive coils mounted in position-displaced relationship about the shaft, and means coupled to the drive shaft and responsive to the selective energization of the coils by respective motor drive signals for causing the corresponding rotation of said drive shaft and movement of said movable element. A sensor is coupled to the drive shaft and is responsive to the rotation thereof for generating an electrical signal containing information indicative of the direction, speed and distance of movement of said movable element. Further, means are included for detecting from the distance information indicated by the electrical signal whether the movable element is within a predetermined distance of said desired stopping position. When it is, a controller controls the levels of the motor drive signals in dependence upon the direction information indicated by the electrical signal such that the motor and thus the movable element are brought to a final stop with only a single one of the motor drive signals and thus corresponding single motor coil on. The controller selectively turns on and off or reverses either the two coils displaced counterclockwise of the single motor coil about the shaft or the two coils displaced clockwise of the single motor coil about the shaft in dependence upon the direction information indicated by the electrical signal.

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First Claim