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Feb
24

Opportunity for Minimizing Loop Interaction

Aggressive action by one loop can upset another loop while attempting fast tight control. The most common example involves loops sharing a common utility or raw material resource, often in piping branches off of a header. The enhanced PID for wireless (PIDPlus) can eliminate the limit cycles that would spread throughout the system. The addition of a velocity limit and the dynamic reset limit PID option would also prevent overly aggressive tuning of the resource user PID from upsetting the pressure or temperature controller for the resource. The PID does not need to be retuned. These PID limits can perform a role similar to the “move suppression” in model predictive control used to determine the degree of transfer of variability from the controlled variable to the manipulated variable.