IFM Ecomat 100 Mobile CR0301, Руководство по программированию

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149
ifm Programming Manual ecomatmobile CabinetController (CR0301) Runtime System V05 2016-04-21
ifm function elements ifm function elements for the device CR0301
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5.2.12 Function elements: controllers
Setting rule for a controller ................................................................................................................ 149
DELAY ............................................................................................................................................... 150
GLR ................................................................................................................................................... 151
PID1 ................................................................................................................................................... 153
PID2 ................................................................................................................................................... 155
PT1 .................................................................................................................................................... 157
1634
The section below describes in detail the units that are provided for set-up by software controllers in
the
ecomatmobile device. The units can also be used as basis for the development of your own
control functions.
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Setting rule for a controller
1627
For controlled systems, whose time constants are unknown the setting procedure to Ziegler and
Nickols in a closed control loop is of advantage.
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Setting control
1628
At the beginning the controlling system is operated as a purely P-controlling system. In this respect the
derivative time T
V
is set to 0 and the reset time T
N
to a very high value (ideally to
∞
) for a slow system.
For a fast controlled system a small T
N
should be selected.
Afterwards the gain KP is increased until the control deviation and the adjustment deviation perform
steady oscillation at a constant amplitude at KP = KP
critical
. Then the stability limit has been reached.
Then the time period T
critical
of the steady oscillation has to be determined.
Add a differential component only if necessary.
T
V
should be approx. 2...10 times smaller than T
N
.
KP should be equal to KD.
Idealised setting of the controlled system:
Control unit KP = KD TN TV
P 2.0 • KP
critical
–– ––
PI 2.2 • KP
critical
0.83 • T
critical
––
PID 1.7 • KP
critical
0.50 • T
critical
0.125 • T
critical
For this setting process it has to be noted that the controlled system is not harmed by the
oscillation generated. For sensitive controlled systems KP must only be increased to a value at which
no oscillation occurs.
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Damping of overshoot
1629
To dampen overshoot
PT1
(
→ page
157 ) (low pass) can be used. In this respect the preset value XS is
damped by the PT1 link before it is supplied to the controller function.
The setting variable T1 should be approx. 4...5 times greater than TN of the controller.