Patent ID: 7876092
Filing Date: 2011-01-25
Classification: G01D

Abstract:
1. A multiple-rotation absolute encoder attached to an actuator, the actuator being provided with a motor and a reduction gear for reducing and outputting rotation of the motor, the multiple-rotation absolute encoder comprising: single-rotation absolute-value detecting means for detecting an absolute position within a single rotation of a rotating shaft of the motor along with the rotation thereof; a multiple-rotation value counter for representing a number of rotations of the rotating shaft from a predetermined origin, the multiple-rotation value counter incrementing or decrementing a count value according to the rotational direction of the rotating shaft at a predetermined switch point during each of the rotations of the rotating shaft on the basis of the position detected by the single-rotation absolute-value detecting means; a memory part for storing a reduction ratio R of the reduction gear; and a counter-controlling part for setting a range of the count value of the multiple-rotation value counter from zero rotations to (R−1) rotations on the basis of the reduction ratio R stored and maintained in the memory part, resetting the count value to zero when the rotating shaft makes a single rotation in a forward direction from a state in which the count value is (R−1), and setting the count value to (R−1) when the rotating shaft makes a single rotation in a reverse direction from a state in which the count value is zero.