Execution Condition Switching; Tracking - Mitsubishi Electric MELSEC iQ-R Series Programming Manual

Execution condition switching

Loop RUN/STOP
If any loop component such as a detector or operation terminal other than the programmable controller fails, each loop can be
run and stopped independently for the purpose of maintenance. SPA of the alarm detection (ALM) is used to run/stop the
applicable loop.
■Basic operation to stop a loop
• Output status is retained. (Example: Output of S.2PID instruction = 0)
• No alarm is detected.
• The control mode is MAN.

Tracking

Tracking refers to making a certain signal follow and match another signal.
Tracking function
The tracking function used by process control instructions includes the bumpless function and output limiter processing
function.
■Bumpless function
The bumpless function prevents manipulated value (MV) output stepping changes when switching from the automatic mode
to manual mode, and continuously and smoothly controls MV output.
■Output limiter processing function
The output limiter processing function limits the upper or lower limit of the manipulated value (MV) output by the PID operation
in automatic mode. This output limiter processing function is only valid in automatic mode and is not executed in manual
mode. The output limiter processing function is not executed either even in automatic mode if the tracking bit (TRK) is set to 0
(Disable tracking).
Cascade loop tracking
The process control loops making up 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 a sudden change in the set value (SV) when the
control mode of the secondary loop (Loop1) is changed.
Cascade loop tracking processing is outlined below.
PID
PV1
Loop 0
PV2
In cascade operation, the manipulated value (MV) of Loop 0 is transferred to the set value (SV) of Loop 1. 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)
Tracking is performed when the control mode is switched to one other than CAS, CSV, or CCB.
11 PROCESS CONTROL INSTRUCTIONS
1194
11.1 Overview
SV
MV
SV
PID
Loop 1
Transferring data
Tracking bit (TRK: 1)
MV