Mitsubishi Electric MELSEC iQ-R Series Programming Manual page 1161

• Operational expressions
Action Operational expression
Direct action
EV = PV
n
ΔMV = K
D
=
n
T
MV = ΣΔMV
n
Reverse action
EV = SV
n
ΔMV = K
D =
n
T
MV = ΣΔMV
n
The meaning of the symbols in the operational expressions is as follows.
Symbol
EV
n
EV
n-1
SV
PV
fn
PV
fn-1
PV
fn-2
MV
MV
n
D
n
D
n-1
T
S
K
P
T
I
T
D
K
D
The PV is calculated by using the following operational expression. If the filter coefficient is not set to the input data, the PV
fn
will be same as the process value of the input data.
+ (PV
PV = PV - PV )
fn n fn-1 n
: Process value for the sampling period this time, : Filter coefficient, PV
PV
n
time (after filtering)
PV is stored in the I/O data area. ( Page 1155 I/O data)
fn
- SV
fn
T
S
{(EV - EV ) +
∙ EV + D }
p n n-1
n n
T
I
T
D
(PV - 2PV + PV ) +
T fn fn-1 fn-2
D
+ T
S S
K
D
- PV
fn
T
S
{(EV - EV ) +
∙ EV + D }
p n n-1
n n
T
I
T
D
( - PV + 2PV - PV ) +
T fn fn-1 fn-2
D
+
S
K
D
Meaning
Deviation in the sampling period this time
Deviation in the sampling period last time
Set value
Process value of the sampling period this time (after filtering)
Process value of the sampling period last time (after filtering)
Process value of the sampling period two times before (after filtering)
Output variation amount
Manipulated value this time
Derivative term this time
Derivative term of the sampling period last time
Sampling period
Proportional constant
Integral constant
Derivative constant
Derivative gain
T
D
K
D
∙ D
T n-1
D
+
K
D
T
D
K
D
∙ D
n-1
T
D
T +
S
K
D
: Process value for the sampling period last
fn-1
10.2 PID Control Instructions (Inexact Differential)
10 PID CONTROL INSTRUCTIONS
10
fn
1159