FLOW CONTROL DEMONSTRATION PANEL
1.0
Experiment
Response
of the control system
This experiment is to
intended to ascertain the properties and response of the control system underlying the model.
For this purpose , steps in control value are applied successively to the system in the non- regulated mode and system’s responce in observed.
For this purpose , steps in control value are applied successively to the system in the non- regulated mode and system’s responce in observed.
Procedure
§ The
main switch for the demonstration model
were turn on.
§ At
setting:00, the adjustment cock(6) are fully open.
§ The
controller were set to manual operation and the manipulated variable y to 10% (=2.5ltr/min).
§ The pump were turn on. After a certain time , the
flow rate assumes a constant value. Read
and this value is taken
§ Increment
the manipulated variable successively by 10% ,until the flow rate has attained a constant value wait briefly
each time. The reading werwe taken to record.
|
Manipulated variable y in %
|
10
|
20
|
30
|
40
|
50
|
60
|
70
|
80
|
90
|
100
|
|
Flow rate in ltr/min
|
0.25
|
0.27
|
0.51
|
0.78
|
1.47
|
2.0
|
3.5
|
5.8
|
7.1
|
7.65
|
Example
of a system’s step responce
Result:
·
The system evidently response very
quickly to changes in the valv e setting, much faster than temperature,
filling-level and the pressure control systems.
·
The system is of a compensatory nature, resulting in constant
final values each time.
·
This characteristic was expected ,
because every pipe system possesses an eintrisic resistence to flow . thus
preventing flow rates from rising
indefinitely.
·
The characteristic of the control variable x
clearly indicates the equa-
percentages response of the control valve.
1.1
Flow Control with a PI- controller
In this experiment, z
controller with proportional and integral components is
used for flow control, accompanied by variation in paremeters.
The controller’s differential components remains inactive.
The control circuit’s response to changes in the reference variable w is observed.
used for flow control, accompanied by variation in paremeters.
The controller’s differential components remains inactive.
The control circuit’s response to changes in the reference variable w is observed.
1.1.1
Slow
PI-control
Procedure:
·
Via main switch the demonstration model were
turn on.
·
The controller and demonstration model
are set as shown in the following table
|
Controller type
|
PI- controller
|
|
Controller Mode
|
Automatic
|
|
P-component >> Pb.1
|
0.1
|
|
I-component >> rt
|
4 seconds
|
|
D-component >> dt
|
0.0 seconds
|
|
Controller Start value:
Setting Step value: |
6 ltr/min (30%)
12 ltr/min (60%)
|
|
Adjustment cock
|
Half open, 450
|
·
The flow rate were observed by using the
readings indicated by the controller and rotameter. After a certain tim e , the floe rate assumes a constant value
of 6 ltr/min.
·
Increment the reference variable w by setting the controller to
12
ltr/min . The flow
rate increaseses and assumes a constant value of 12 ltr/min after a certain time.
Example of PI-
controller with integration time too long
Result
:
The input signal y
reveals that although the controller
responds immediately to changes in the
reference variable , it takes a long time to archieve a constant target value. The desired flow rate of 12 ltr/min is
attained very slowly (t >1 minute).
The controller’s
P-component achieves fast response, while the I- component eliminates persistent deviations. However , the selected
integration time is still too long.
1.1.2 Fast
PI Controller
In this experiment, too, a controller with proportional ang integral components is used for flow control.
The controller differential component remains inactive.
compared with experiment 1.1.1 , the integration time –i.e. the controller I-component- is set to a notably lower value.
The control circuit response in the reference variable w is observed.
In this experiment, too, a controller with proportional ang integral components is used for flow control.
The controller differential component remains inactive.
compared with experiment 1.1.1 , the integration time –i.e. the controller I-component- is set to a notably lower value.
The control circuit response in the reference variable w is observed.
Procedure:
§ Via
the main switch the demonstration model were turn on.
§ The
controller and demonstration model are set as shown in following table
|
Controller type
|
PI- controller
|
|
Controller Mode
|
Automatic
|
|
P-component >> Pb.1
|
0.1
|
|
I-component >> rt
|
0.5 seconds
|
|
D-component >> dt
|
0.0 seconds
|
|
Controller Start value:
Setting Step value: |
6 ltr/min (30%)
12 ltr/min (60%)
|
|
Adjustment cock
|
Half open, 450
|
§ The
flow rate are observed using the reading indicated by the controller and
rotameter. After a certain time, the flow rate assumes a constant value of 6 ltr/min .
§ Increment
of the referenc e variable w by setting the controller to 12 ltr/min . The flow rate increases and assumes a
constant value of 12 ltr/min
after a certain time.
Example of an
a PI –controller with integration time too short
Result:
The input signal y
reveals that the controller quickly generates value s which are notably higher than in the previous
experiment. In fact , the control variable now
distinctly overshoots the targets
value of 12 ltr/min
and start to ascillate about it. The oscillations decay in -30 seconds
to a permanents level of roughly +/- 5%
about target value. The parameter selected here do not result in satisfactory control performance. The selected
integration tim e is obviously too short.
1.1.3 PI-
controller with improved parameters
In
this experiments , too , a
controller with proportional and
integral components is used for flow control.
The controller differential compenent remain inactive.
The controller differential compenent remain inactive.
The
result obtained in experiment 1.1.1, 1.1.2
are used as a basis for adapting the controller’s integration time here.
The
control circuit’s response to changes in the reference variable w is observed.
Procedure:
§ Via
main switch the demonstration model are turn on.
§ The
controller and demonstration model are set as shown in the following table:
|
Controller type
|
PI- controller
|
|
Controller Mode
|
Automatic
|
|
P-component >> Pb.1
|
0.1
|
|
I-component >> rt
|
0.75 seconds
|
|
D-component >> dt
|
0.0 seconds
|
|
Controller Start value:
Setting Step value: |
6 ltr/min (30%)
12 ltr/min (60%)
|
|
Adjustment cock
|
Half open, 450
|
§ The
flow rate are observed using the reading indicated by the controller and
rotameter. After a certain time, the floe rate assumes a constant value of 6ltr/min .
Increment the
reference variable w
by setting the controller to
12 ltr/min . The
flow rate increases and § assumes
a constants value of 12 ltr/min after a certain time.
Example of a PI –controller with improved
parameters.
Result:
The input signal y
rises immediately after the steps in the reference variable to achieve a nearly
constant value in just ~ 5 seconds.
The control variable initially overshoots the targets value by ~5% and never becomes completely stable, insteads ascillating irregularly about the target value.
However , the control perfomanc e is acceptable for a fast system such as this one.
The control parameters in this operarating mode are nearly ideal for responding to changes in the reference variable. This configuration is a compromise between response and control performance.
The control variable initially overshoots the targets value by ~5% and never becomes completely stable, insteads ascillating irregularly about the target value.
However , the control perfomanc e is acceptable for a fast system such as this one.
The control parameters in this operarating mode are nearly ideal for responding to changes in the reference variable. This configuration is a compromise between response and control performance.
