A. Pomerleau and É. Poulin (Canada)
A new method, based on the interpretation of the manipulated variable is developed to tune PID controllers and the detection of poor settings. This variable is used to set the specifications and tune the controllers for set-point changes. Here, these specifications are to have a closed loop time response that is similar to the open-loop time response and a no static error to non zero mean disturbance acting at the process input. The method is applicable to self-regulating first and second order models having stable or unstable zeros as well as delays and to integrating first order processes. For second order process, an approximation of equal time constant is used in order to facilitate the identification with step changes and the tuning with PI controller. Results show that the tuning is near optimal even when the time constant are very different. The method can be taught to people with different backgrounds: process engineers, maintenance technicians, production operators as well as the management. Results have shown better understanding of the possibilities and limitations of process control and the improvement of the understanding and communication between the different groups.
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