Yaskawa MP900 Series Ladder Programming Manual - Manual (Page 230)

5.8 DDC Instructions
5.8.7 First-order Lag (LAG)
5-161
Instructions
5
5.8.7 First-order Lag (LAG)
( 1 ) Operation
The LAG instruction calculates the first-order lag according to predefined parameters in a parameter table.
The input value to the LAG instruction can be an integer or a real number. Double-length integers cannot be used.
The structure of the parameter table is different for integers and real numbers.
The LAG operation in the figure shown above can be expressed by the formula shown below.
The following operation is performed internally by the LAG instruction, where dt = Ts and dY = Y – Y’.
In the formula shown below, Y’ is the previous output value, Ts is the scan time set value,* and REM is the remainder.
∗ The unit for Ts is the same as the unit for T.
ΠWhen IRST (LAG reset) is closed, Y outputs 0 and REM outputs 0.
ΠThe symbols in the figure correspond to those in the parameter table.
Output value Y for
LAG instruction
Input value X for
LAG instruction
Time (t)
Time constant T
Approx. 63% →
=
1
1 + T × s
Y(s)
X(s)
T × + Y = X
dY
dt
Therefore,
Y =
T × Y' + Ts × X + REM
T + Ts