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
PV
n-1
)
CT
T
D
}
B
n-1
Bn
When reverse operation
(PN
0)
B
n-1
M
D
T
D
M
D
CT T
D
{PV
n-1
)
CT
T
D
}
B
n-1
(PV
n
In
DV
n
CT
T
I
I
n-1
TKp(DVn In Bn)
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
B
n
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 error occurred
0DV
n
CT
T
I
3. When ML error occurred
0DV
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 (BB2) of the block memory.
Condition Result
DVL |DV|
DVLA
BB2 1
*1
(DVL DVLS) |DV| DVL
DVLA
BB2 Last value status hold
*1
|DV| (DVL DVLS) DVLA BB2 0
*1:
When DVLI or ERRI in the alarm detection inhibition (INH) is set to 1, DVLA and BB2 show
0 since the alarm is prohibited
(6) Mode judgment
Either of the following processings is performed depending on the operation mode (MODE)
setting.
(a) When the operation mode (MODE) is any of MAN, CMB, CMV and LCM (alarm clear
processing)
1) MHA, MLA and DMLA of the alarm detection (ALM) are turned to 0.
2) BB3 to BB5 of BB are turned to 0.
3) Data of BB2 is transferred to BB1 of BB. (BB1
BB2)
4) "(8) Output conversion processing" is performed and the S.PIDP instruction is
terminated.
(b) When the operation mode (MODE) is any of AUT, CAB, CAS, CCB, CSV, LCA and LCC,
"(7) Change rate, upper/lower limiter" is executed.