YOKOGAWA UT130, Техническая информация

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<Toc> <Ind>
6-5
TI 05C01E02-01E 1st Edition : Oct. 31, 2001-00
6.4 Derivative (D) Action
6.4.1 Derivative Time (D)
•
If the control object has a large time
constant or dead time the corrective
action will be too slow with proportional
action or proportional-plus-integral action
alone, causing overshoot. However,
even just sensing whether the deviation
is on an increasing or a decreasing trend
and adding some early corrective action
can improve the controllability. Thus the
derivative action ("D" action) is action
that changes the output in proportion to
the deviation derivative value (rate-of-
change). The parameter that sets how
the derivative action will operate is the
derivative time (D).
•
The derivative time (D) is defined as
the time required with "PD" action to
develop, when a constant-slope-change
in deviation is imposed, an output
change due to derivative action that is
exactly equal to the change due to
proportional action.
•
Derivative time (D)
P=100%
Output =
P
100
e + e
T
D
e : Deviation
T
D
: Integral time
Deviation
Deviation Output (%)
(On-time ratio)
Output change
due to P action
Output change
due to D action
Derivative
time
Time
dt
d
Large
derivative time
Small
derivative time
6.4.2 Tuning the Derivative Time
•
The longer the derivative time is set,
the stronger the corrective action is, and
the more likely the output will become
oscillatory. Oscillations due to derivative
action are characterized by a short
period.
•
When the derivative time (D) is set to
OFF, the derivative action does not
function. D=OFF should always be used
when controlling fast-responding inputs
such as pressure and flow, or inputs
characterized by rapid fluctuation, such
as optical sensors.
•
To manually adjust the derivative time parameter
•
Adjust from shorter time to longer time.
•
If you see a short-period oscillation, the time is too long.
D
Parameter Range
PV
Time
SP
•
If D is too large, short-period oscillation appears
in the measured temperature.
UT130:
1 to 999 sec or OFF
UT150/UT152/UT155:
1 to 3600 sec or OFF