Program Examples For Pid Control When Switching Modes - Mitsubishi Electric MELSEC iQ-R Series Programming Manual

Program examples for PID control when switching modes

The program performs PID operation by switching an automatic mode and a manual mode.
The program conditions are as follows:
Item
Number of loops that performs PID operation
Sampling period
Device where PID control data are set
Device where I/O data are set
Set value (SV) set by external digital
switches and manipulated value (MV)
in manual mode
Device used to start/stop PID control
Device used to switch the mode
Digital value of the R60AD4 and R60DA4
SM792, SM794
In manual mode, the set value (SV) is automatically rewritten to the process value (PV) when PID operation is
performed. Therefore, when the manual mode is returned to the automatic mode, the set value (SV) must be
rewritten to the one used before the mode was switched.
The set value (SV) is rewritten in 10 steps as shown below:
SV in manual mode
SV in automatic mode
The following formula is used to rewritten the set value (SV).
SV
m
SV : SV in automatic mode
a
The value obtained with the above operational expression is subtracted from the set value (SV) every second.
The remainder is subtracted in the first subtraction.
APPX
2070
Appendix 5 PID Control Program Examples
Common data
Loop 1 data
Common data
Loop 1 data
SV
MV in manual mode
PID control start command
PID control stop command
SV set command
MV (in manual mode) set
command
Automatic/manual switch
command
Mode change
command
1s
SV SV
-
m a
10
: SV in manual mode
Inexact differential
1
1 second
D500, D501
D502 to D515
D600 to D609
D610 to D630
X30 to X3F
X20 to X2F
X0
X1
X3
X4
X6 (Off: Automatic mode, On: Manual mode)
0 to 2000
Off
1s
1s 1s
10s
Subtraction
.........
=
value
Exact differential
D502 to D511
D610 to D627
Remainder