PI CONTROLLER DESIGN FOR TIME DELAY SYSTEMS

The paper presents an approach to PI controller design for systems with varying time delay, which can be interpreted as systems with interval parametric uncertainty. The transfer function of the controlled system is modified by approximation of the time delay term by its Pade expansion or Taylor expansion in the numerator. PI controllers, that are able to assure robust stability of the feedback closed loop with the modified controlled system are found by the graphical method. Then the pole-placement method is used to specify those controller parameters, which assure certain quality of the control performance. Designed PI controllers are implemented using PLC SIMATIC S7-300 and tested by experiments on a laboratory electronic equipment with varying time delay.