| 摘要 |
PURPOSE:To avoid the shift of position due to the variance of the working position of a limit switch and to perform the position control with high accuracy in a simple way, by switching automatically the position which is shifted by an extent equal to a half cycle of a zero marker signal to an original point confirming position in case the position where the limit switch is turned on is set close to the original point confirming position of the zero marker signal. CONSTITUTION:The position pulse signals (c) are counted by a computing element 1 of a position controller for a period during which a zero marker control signal (b) is set at '1' after a limit switch 7 is turned on and also calculates a distance (d) moved in said period. At the same time, a setting device 2 sets an optional distance A that can cover the variance range of the working position of the switch 7 in a distance shorter than that moved in a single cycle of the signal (b). Both distance A and (d) are compared with each other by a comparator 3. Then an FF 5 is set with d<A and then reset with d>A respectively. The signal valid and invalid states are switched by a switch 4 between the set and reset modes.
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