The anti-windup measure ensures that the Integral component does not grow too much causing the controller to lock if it has been limited at a control limit too long. Anti-windup measures are only performed for an active I component of the controller.
Limits for the anti-windup measure are by default the manipulated variables of the controller (delt_aw = 0). The parameter delt_aw can be used to either increase (delt_aw > 0) or decrease (delt_aw < 0) the limits with regard to the control limits (ymax, ymin).
Therefore, the limits used for the anti-windup measure are:
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AWMAX = ymax + delt_aw
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AWMIN = ymin - delt_aw.
Through displacement of the anti windup limits in relation to the control limits (in particular with very noisy signals), the manipulated variable Y can be stopped from repeatedly 'jumping away' from the control limit (D component effect to disturbances) and subsequently returning to the limiting position (I component effect with system deviation ERR ≠ 0). If the control limits are to be simultaneously effective for the anti-windup measure, select the parameter delt_aw = 0.
By utilizing negative delt_aw values, anti-windup limits can be kept smaller than control limits (useful for anti-windup halt).
Anti-windup reset (
halt_aw = 0)
The anti-windup measure disregards the D component, to avoid the capping of the D component peaks through the anti-windup measure. The anti-windup-reset measure corrects the I component such that: AWMIN ≤ YP + FEED_FWD + YI ≤ AWMAX.
Anti-windup halt (
halt_aw = 1)
The anti-windup measure only considers the I component. When anti-windup halt and I component are enabled, the anti-windup halt measure corrects the I component such that: AWMIN ≤ YI ≤ AWMAX.
The parameters rate_sp and rate_man represent velocity limiters for the manual values SP and YMAN (see also function block VLIM). A 0 value disables the functionality of the corresponding velocity limiter (rate_sp = 0 or rate_man = 0, respectively). The SP and YMAN values are then utilized without delay.
