| 摘要 |
<p>A method and apparatus for sensing the current position of a movable element in a position control system which includes first and second control devices (101, 102) each having command pulse generating means (101 d, 307) and error storage means (101e, 102m) for computing and storing an error between a number of command pulses and a number of feedback pulses indicative of an amount of motor movement, a speed control circuit (not shown) for driving and controlling the motor on the basis of the error in the storage means (101 e, 102m) and a switching circuit (103a) for selectively connecting the first and second control devices (101, 102) to the speed control circuit, the current position of the movable element being sensed by one control device (101) when the other control device (102) is connected to the speed control circuit. The method includes steps of storing the errors which prevail in the respective storage means (101 e, 102m) just prior to switching from the first control device (101) to the second control device (102), returning the movable element to the position which prevailed just prior to the switching operation by supplying the speed control circuit with an offset voltage corresponding to an arithmetic difference found by substracting the stored error from the error storage means (102m) of said second control devide (102), from the error in the error storage means (102m) of the second control device (102) after the switching operation when the movable element has stabiiised, updating the data in a current position register (202) of the first control device (101) on the basis of an arithmetic difference found by subtracting the stored error from the error storage means (101 e) of the first control device (101), from the data in the error storage means (101 e) of the first control device (101) while the motor is controlled by the second control device (102), and revising the data in the error storage means (101 d) of the first control device (101) on the basis of the arithmetic difference.</p> |
