Functions; Tracking Function; Cascade Loop Tracking - Mitsubishi MELSEC-Q series Programming Manual

5.2

Functions

5.2.1

Tracking function

The tracking function includes the "bumpless function" and "output limiter processing".
(1) Bumpless function
The bumpless 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]
(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)
36
SV
PID
PV1
Loop 0
PV2
Trucking data transmission
MV
SV
Trucking bit (TRK: 1)
PID
MV
Loop 1