Yaskawa MP900 Series Ladder Programming Manual - Manual (Page 224)

5.8 DDC Instructions
5.8.5 PD Control (PD)
5-155
Instructions
5
( 4 ) Additional Information
[ a ] Transfer Functions
The transfer function of the P and D operations can be expressed by the formula shown below.
In this formula, X (s) is the input value and Y (s) is the output value.
= Kp + Kd × Td × S
[ b ] Divergence and Convergence
The following figure shows the relation between the current deviation X and previous deviation X’ on the divergence
and convergence sides.
Y(s)
X(s)
Deviation
X' = 10 X = 15
(X − X') = 5
Both are positive
(same sign).
• Example of a Diverging Deviation
X' = 15 X = 10
(X − X') = -5
The signs
are different.
• Example of a Converging Deviation
Time Time
Deviation