Patent ID: 7149589

Claim:
A method of adjusting a process control device in which a closed loop system comprising a control subject and an external compensator is approximated by a transfer function expressed by a first-order delay and a dead time and said approximated closed loop system is controlled by a controller, said method comprising: (1) defining said transfer function of said control subject; setting a compensation parameter of said external compensator comprising a proportional gain element and an incomplete differentiation element in a range so that a step response of said closed loop system does not diverge or oscillate; adjusting said compensation parameter in a first step in which said step response of said closed loop system is displaced as a first response; (2) setting a model transfer function of said closed loop as a model parameter of said model transfer function comprising a proportional gain element, a dead time and a first-order delay element; displaying a step response of said model transfer function as a second response superimposed on said first response; adjusting said model parameter effected as a second step so that a difference of said first response and said second response is kept within a prescribed evaluation standard range; (3) setting said controller by performing a prescribed conversion with said model parameter as said control parameter of said controller; displaying a step response of a process transfer function constituted by said control subject, said external compensator and said controller as a third response; and evaluating a response of said process control device within a prescribed evaluation standard range as a third step; if said third response exceeds said prescribed evaluation standard range, then readjustment is performed by repeating said first step to said third step so as to bring said third response within said evaluation standard range.