Controller tuning for a slow nonlinear process

Determining the tuning constants of a classical PID (proportional-integral-derivative) controller for a slow nonlinear process, such as the temperature loops on a heat-treat of annealing furnace, can be a laborious task. Several tuning methods were considered to identify a method that could be applied easily in the field with limited resources. The method of Ziegler and Nichols (1942) proved to easy and effective. Results obtained by using the Ziegler-Nichols open-loop method to determine the tuning constants for a classical PID temperature controller for a heat-treat furnace are described. The process being controlled is described, and open-loop test data are presented.<
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