User`s manual

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MELSEC-Q
5 EXECUTION CONDITION SWITCHING AND FUNCTIONS
5.2 Functions
5.2.1 Tracking function
The tracking function includes the "bump-less function" and "output limiter processing".
(1) Bump-less function
The bump-less function prevents manipulated value (MV) output stepping changes when
switching from the automatic mode to manual mode and continuously controls MV output.
(2) Output limiter processing function
The output limiter processing function limits the upper limit and lower limit of the manipulated
value (MV) output by the PID operation during the automatic mode. This output limiter
processing function is only valid in the automatic mode and is not executed for manual data. In
addition, when the parameter tracking function execution validity is set to not valid when in the
automatic mode the output limiter processing function will not execute.
5.2.2 Cascade loop tracking
The process control loops that comprise a cascade loop use the manipulated value (MV) of a
primary loop (Loop 0) as the set value (SV) of a secondary loop (Loop 1).
Tracking is performed to prevent the sudden variation of the set value (SV) when the operation
mode of the secondary loop (Loop 1) is changed.
(1) The cascade PID loop Tracking processing is shown in the diagram below.
[Processing concept diagram]
PID
Loop 0
PID
Loop 1
SV
SV
Trucking data transmission
MV
Trucking bit (TRK: 1)
MV
PV1
PV2
(a) In cascade operation, the manipulated value (MV) of Loop 0 is transferred to the set value
(SV) of Loop 1.
(b) When cascade operation is not performed, the set value (SV) of Loop 1 is transferred to the
manipulated value (MV) of Loop 0.
(Tracking to the source specified as the input terminal of the set value (SV) of Loop 1)
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