| 摘要 |
PURPOSE:To detect the present position of the operating part of a machine immediately when a power source is turned ON after power failure or cut off of the power source, by providing a first detector, which detects the absolute position within one rotation of a main shaft, and providing a second detector, which detects the absolute position within one rotation of a speed reduced shaft. CONSTITUTION:An increasing increment in rotation of a second detector 114 per one rotation of a main shaft 101, i.e., one rotation of a first detector 105 is made to be alpha0. A rotary angle of the second detector 114 is made to be alpha. A rotary angle of the first detector 105 is made to be beta (carry when rotation is performed more than once cannot be detected). Then the angle alpha can be expressed by alpha= (m+x)alpha0, where (m) is an integer part and (x) is a decimal part. Since x.alpha0= B/N (N is a speed reducing ratio, e.g., 1/100), m=(alpha-B/N)/alpha0 can be expressed. Therefore, by detecting alpha and beta how many times the main shaft is rotated can be judged. Namely, the absolute rotary angle theta of the main shaft is expressed by theta=2pim+beta. The precise rotary angle can be obtained by the angle detected by a resolver, which is directly coupled to the main shaft.
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