MIMO PID Control Retuning Using the Closed-Loop Frequency Response

Proportional integral derivative (PID) controllers are the most used in practice for regulatory control. This is due to the good performance achieved by this controller for a variety of processes. However, about 60% have performance issue. This problem can be more evident in multivariable processes, due to the coupling between the loops. One way to improve performance is to retune the parameters. Thus, in this article, a PID control retune technique is presented. Frequency domain data are used to compute gain increments. Identification of the parametric model of the process is not necessary. The method can be applied to multivariable processes with time delay, integrative dynamics, and nonminimum phase zeros. Simulation results and the effectiveness of the method are discussed