Internal Model Control IMC Tuning Rules

A set of Internal Model Control (IMC) tuning rules were established by Rivera, Morari, and Skogestad for a first-order plus dead time (FOPDT) open-loop process response that simply involves the adjustment of the proportional gain in the controller, K, for tuning. The integral time constant, 7, is set equal to the first-order time constant, TFO, for PI controllers (Table 10.5). 

Control Action Controller Gain (KJ Integral Time (T) 

Skogesta reported a modification of the IMG rules to SIMC rules for improved disturbance rejection. The recommendation for PI control is to adjust the integral time constant to the smaller value of either 7/ = TFO or 7f = 8 ADT. The TFO of 20 min is smaller than the calculated = (8X3.6) = 28.8 min in this case. 

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