ULTIMATE-FREQUENCY BASED THREE-POLE DOMINANT PLACEMENT IN DELAYED PID CONTROL LOOP

Besides its original use in the state space based design the pole assignment is also applied in tuning the PID controllers where only an approximate model is considered. However, the common assumption of time delay in this model imposes the limitation that only such pole prescription which results in the dominant pole assignment can be effective in tuning the control loop with time delay. The three parameter PID controller is capable to assign just three poles and a dominance guarantee of their prescription is crucial in the pole placement. A novel method of selecting a trio of numbers p1,2,3 to make them the dominant poles of the control loop is dealt with in the paper with an additional minimizing the absolute error integral. The dominance of each of the placement trials is checked by an argument increment criterion and an optimum of relative damping of the response is assessed to minimize the control error integral. The disturbance rejection response as the critical point of view in time delay process control is taken as criterion in the controller design.