Mitsubishi Electric MELSEC iQ-R Series Programming Manual page 172

■Variation rate & high/low limiter
This function block checks the variation rate and high/low limits of the input value.
• Variation rate limiter
Variation rate limiter processing result
DML
Execution cycle (ΔT)
Control cycle (CT)
Condition
|T - MV|  DML
T - MV > DML
T - MV < -DML
T: Tentative manipulated value, MV: Manipulated value, DML: Output variation rate high limit value
• High/low limiter
High/low limiter processing result
Execution cycle (ΔT)
Control cycle (CT)
Condition
Variation rate limiter processing result
> MH
Variation rate limiter processing result
< ML
ML  Variation rate limiter processing
result  MH
MH: Output high limit value, ML: Output low limit value
■Reset windup
As countermeasures against reset windup, this function block sets a manipulated value to the high/low limit value when the
manipulated value has exceeded the limit value, and quickly responds to a control target when deviation is inverted.
Condition
Variation rate limiter processing result > MH and
Variation rate limiter processing result < ML and
MH: Output high limit value
ML: Output low limit value
MVP: MV internal operation value
T: Execution cycle
T: Tentative manipulated value
Ti: Integral time
However, when Ti is 0, countermeasure processing against reset windup is not performed.
9 I/O CONTROL
170
9.6 Time Proportioning Output (M+P_DUTY)
Tentative MV value (T)
DML
DML
Control cycle (CT)
Variation rate limiter processing result
T
MV + DML
MV - DML
Variation rate limiter processing value
Control cycle (CT)
High/low limiter processing
result
MH
ML
Variation rate limiter processing value
ΔT ≤1
Ti
ΔT ≤1
Ti
DML
DML
Control cycle (CT)
Control cycle (CT)
Alarm (ALM)
Output low limit (MLA)
FALSE (Reset)
TRUE (Detected)
FALSE (Reset)
Countermeasure processing against reset windup
ΔT
MVP= ×(MH-T)+T
Ti
ΔT
MVP= ×(ML-T)+T
Ti
Variation rate limiter
processing value
DML
DML
t
Alarm (ALM)
Output variation rate limit (DMLA)
FALSE (Reset)
TRUE (Detected)
TRUE (Detected)
High/low limiter
processing value
Output high limit
(MH)
Output low limit
(ML)
t
Output high limit (MHA)
TRUE (Detected)
FALSE (Reset)
FALSE (Reset)