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7 APPLICATION INSTRUCTIONS
7.18 PID Instruction
Operation method of PID operation instruction (reference)
The instruction performs the PID operation using the speed type or process value differential type operational expression.
The operational expression of direct action or reverse action is performed according to the data in bit 0 of (S3)+1 (operation
setting (ACT))
Each value required in the operation calculates using parameters specified (S3) or later.
■Symbol
■Calculation formula of PV
nf
Process value after the filter (PV
nf
) = PV
n
+ L(PV
nf-1
- PVn)
Bit 0 of (S3)+1 PID operation method
Direct action (OFF)
Reverse action (ON)
•EV
n
: Deviation at current sample
•EV
n-1
: Deviation before one cycle
• SV: Set value
•PV
nf
: Process value at current sample (after filter)
•PV
nf-1
: Process value before one cycle (after filter)
•PV
nf-2
: Process value before two cycles (after filter)
• MV: Rate of output change
•MV
n
: Current manipulated value
•D
n
: Current derivative term
•D
n-1
: Derivative term before one cycle
•K
P
: Proportional gain
•T
S
: Sampling period
•T
I
: Integral constant
•T
D
: Derivative constant
•K
D
: Derivative gain
•PV
nf
: Process value at current sample
• L: Filter coefficient
•PV
nf-1
: Process value before one cycle (after filter)
()
∑
∆=
+
+++
+
=
−=
⎭
⎬
⎫
⎩
⎨
⎧
+=∆
MVMV
D
TKT
TK
PVPV2PV-
TKT
T
D
SVPVEV
DEV
T
T
EV-EVKMV
n
1-n
DDS
DD
2-nfnf1-nf
DDS
D
n
nfn
nn
I
S
1-nnP
•
•
•
)(
•
+
()
∑
∆=
+
+−−
+
=
−=
⎭
⎬
⎫
⎩
⎨
⎧
+=∆
MVMV
D
TKT
TK
PVPV2PV
TKT
T
D
PVSVEV
DEV
T
T
EV-EVKMV
n
1-n
DDS
DD
2-nfnf1-nf
DDS
D
n
nfn
nn
I
S
1-nnP
•
•
•
)(
•
+
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