METHOD AND AN APPARATUS FOR PID CONTROLLER TUNING

A method for tuning P-, I- and D-type controller which is used in combination or individually to control a variable y of a process in a feedback system, which comprises making the integrating (I) and derivative (D) unit of the controller inoperative; increasing the proportional control gain K until a desired oscillation is obtained; calculating the ultimate gain Ku and ultimate period Tu in accordance with the amplitude and period measured from the oscillation; and setting the parameters of the PID controller in dependence upon the Ku and Tu values, wherein the control signal U resulting from the controller gain K is restricted to a range from a lower limit Umin to an upper limit Umax to avoid the system being operated in an unstable condition. An apparatus suitable for performing the present method is also disclosed.