Design of PID controllers for Critically Damped SOPTD systems

In this paper two methods are proposed to design a Proportional-Integral-Derivative (PID) controller for critically damped second order plus time delay systems (CDSOPTD). The standard Multiple Dominant Pole method (MDP) is extended to CDSOPTD processes. The Direct Synthesis method is formulated for CDSOPTD processes. Simulations are carried out for three CDSOPTD processes. The performances are compared with the earlier proposed methods in the literature. Significant improvement has been achieved in the disturbance rejection problem. The performance criteria such as Integral Square Error (ISE), Gain margin, Phase margin, Maximum sensitivity are used to evaluate the effectiveness of the proposed method.