The Pid Control System - Mitsubishi Electric MELSEC Q Series User Manual

1 GENERAL DESCRIPTION

1.2 The PID Control System

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(1) The PID control system
Figure 1.3 indicates the system configuration when performing PID control.
Set value data
storage
process value
data storage
(2) PID control procedure
The PID control is performed in the procedure shown in Figure 1.4 below:
Read the PV value
Perform PID
operation
Output MV
(3) PID control (simplified two-level response selection)
In general, when the P, I, and D constants to improve the "response to the
setting" are set, the "response to the disturbance" degrades by the PID control.
Conversely, when the P, I, and D constants to improve the "response to the
disturbance" are set, the "response to the setting" degrades by the PID control.
In the PID control (simplified two-level response selection) of this module, "fast",
"normal", or "slow" can be selected for the "response to the setting" while the P, I,
and D constants for better "response for the disturbance" are selected.
Set
value
(SV)
Response to the change of the set value
search engine
Q64TC
SV
PID operation
PV
Fig. 1.3 The PID control system
Import a signal from the temperature sensor and write
it to the process value storage area as a PV value.
Perform PID operation using the SV/PV values in the
set value/process value storage area.
Convert MV value obtained by the PID operation
to transistor -output on time and output it.
Fig. 1.4 PID control procedure
Fast
Normal
Slow
Fig. 1.5 simplified two-level response selection
MELSEC-Q
MV
Manipulated value
data storage
Set
value
(SV)
Response to the disturbance
Control
object
Sensor
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