Derivative Control (Pre-Act Or Rate), D; Feed Forward Control, F - Siemens Milltronics BW500 Operating Lnstructions

Derivative Control (Pre-Act or Rate),
D
The term on the BW500 influences the control output based on changes in the
magnitude and direction of the change in error. If there is a constant error, the
no effect. As the error gets larger, the
BW500 control output respond faster. When the error is getting smaller, the
reduce the amount of control output to help prevent overshooting the set point. In
general, a higher
+
Error
-
Decreasing
Error
Direction of
Proportional
Action
Direction of
Derivative
Action
• allowable input range:
• typical operating range:
• default value:
The result of the derivative action is that it can make a system more responsive and more
stable at the same time.
Feed Forward Control,
On the BW500, the
The use of this term can make the system reach the new setpoint faster. If the term is not
used, the system responds using the
new setpoint and the process variable is the error and the control algorithm responds to
eliminate this new error.
F
When the term is used and a new setpoint is entered, a proportion of the difference
between the new setpoint and the process variable is automatically added on to the
control output. This shifts the process variable closer to the new setpoint faster than
P,
using the I and
• allowable input range:
• typical operating range:
• default value:
Page 76 Milltronics BW500 and BW500/L - OPERATING INSTRUCTIONS 7ML19985DK05
D
P
term will require a larger
Increasing
Error
0.000 to 1.000
0.010 to 0.100
0.050
F
F
term is used to adjust the control output based on a setpoint change.
P
, I and
D
terms alone. This is done on a one time basis.
0.000 to 1.000
0.250 to 0.550
0.300
D
term combines with the
D
term.
Decreasing Increasing
Error Error
D
terms only. The difference between the
D
term has
P
term to make the
D
term acts to
Setpoint