The L9P_PI control structure is displayed in the structure diagram. Setting parameters for the function block takes place first for the elemental PI parameters: the proportional rate kp and reset time tn.
The limits YAO and YAU limit the output within the prescribed range. Therefore
YMIN ≤ Y ≤ YMAX.
The markers output word 1, status bit 3 (high limit marker) and output word 1, status bit 2 (low limit marker) signal that the defined limits have been reached or the output signal is being limited.
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output word 1, status bit 3 = 1 if Y ≥ YMAX
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output word 1, status bit 2 = 1 if Y ≤ YMIN
Manipulated Variable Limiting
After summation of the components manipulated variable limiting takes place, so that: YAU ≤ Y ≤ YAO
When limiting of the manipulated variable takes place, the anti-windup reset helps to ensure that the integral component integral component cannot exceed the defined limits.
The anti-windup measure is only implemented if the I component of the controller is not disabled. Anti-windup limits are identical to those for the manipulated variable.
The anti-windup-reset measure corrects the I component such that:
(YAU + YP) ≤ YI ≤ (YAO - YP).
