User`s manual
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MELSEC-Q
9 CONTROL OPERATION INSTRUCTIONS
(4) PID operation
PID operation is performed with the following operation expression.
Item Operation expression
When forward operation
(PN
1)
B
n-1
M
D
T
D
M
D
CT T
D
{(PV
n
2PV
n-1
PV
n-2
)
CT
T
D
}
B
n-1
Bn
When reverse operation
(PN
0)
B
n-1
M
D
T
D
M
D
CT
T
D
{2PV
n-1
PV
n-2
)
CT
T
D
}
B
n-1
(PV
n
BW ( MV)
}
)
K
P
B
n
DV
n
{(DV
n
DV
n-1
CT
T
I
K
P
: K Gain (P), M
D
: Derivative gain (MTD)
T
I
: Integral constant (I), T
D
: Derivative constant (D)
In the following case, however, note that special processing will be performed.
Condition Processing
In either of the following cases 1, 2
1. Derivative constant (D)
0 (T
D
0)
2. Operation mode (MODE) is any of MAN, LCM and CMV
Bn
0
(However, the loop tag past
value memory is set.)
In any of the following cases 1, 2, 3
1. Integral constant (I)
0 (T
I
0)
2. When MH or ML error occurred
(MVP
MH) and
0)DV
n
(
CT
T
I
3. When MH or ML error occurred
(MVP
ML) and
0)DV
n
(
CT
T
I
0DV
n
CT
T
I
(5) Deviation check
A deviation check is made under the following condition and the result of the check is output to
DVLA of the alarm detection (ALM) and the deviation large alarm (BB1) of the block memory.
Condition Result
DVL |DV| DVLA BB1 1
*1
(DVL DVLS) |DV|
DVL DVLA
BB1 Last value status hold
*1
|DV| (DVL DVLS) DVLA BB1 0
*1:
When DVLI or ERRI in the alarm detection inhibition (INH) is set to 1, DVLA and BB1 show
0 since the alarm is prohibited.
(6) Loop stop processing
(a) Setting 1 in SPA of the alarm detection (ALM) selects a loop stop.
A loop stop performs the following processing and terminates the S.PID instruction.
1) BW is turned to 0.
2) DVLA of the alarm detection (ALM) is turned to 0.
3) The operation mode (MODE) is changed to MAN.
4) BB1 of BB are turned to 0.
(b) Setting 0 in SPA of the alarm detection (ALM) selects a loop run.
A loop run performs "(7) Control cycle judgment".