| 摘要 |
PROBLEM TO BE SOLVED: To change a card on-line by making it possible to reset a lock not through manual operation without abruptly varying the opening extent of an operation end. SOLUTION: A comparator 21 finds the difference between a measured value and a control set value of a plant and a PI computing element 23 calculates an opening extent command for the operation end 56 so that the deviation becomes zero. This opening extent command is stored in the memory 31 on a card 30 and inputted to an I/P converter 53. The I/P converter 53 operates so that air pressure applied to the operation end 56 reaches the command value. If abnormality such as an air pressure drop occurs, a computer 20 locks the operation end 56 and holds the opening extent command right before that in a memory 24. When the card 30 is replaced, the opening extent command held in the memory 24 is set in the memory 31 and then the operation signal of a switch 19 for lock resetting is received to reset a set/reset circuit 32, thereby releasing the operation end 56 from being locked. |
