Level Control Experiment
Pre-Experimental Questions
Below are a number of pre-experimental questions. It is suggested that you
run the experiment in the following order.
- Think about the questions before running a particular part of the Level
Control Experiment.
- Run the experiment, trying the various suggested parameter values.
- Answer the questions and then read the various solutions and thoughts
after running the experiment!
Click here if you wish to have a picture of the
flowsheet for reference while you run the simulation.
No Control
Try Running the experiment with no control :
- What do you think will be the effect of altering the control valve
position on the level in the tank?
- What do you think will be the effect of altering the flowrate to the system?
- What are the implications of altering the flowrate to the tank on the
required control valve size and range of control?
Remember to introduce a disturbance by making a change to at least one of the parameters below
On/Off Control
Try running the experiment with On/Off control
- When do you think this sort of control could prove useful and when (and
why) would you consider it impractical?
- What is the effect of altering the dead zone on the on/off controller?
- What is the effect of altering the flowrate to the tank?
Remember to introduce a disturbance by making a change to at least one of the parameters below
Proportional Only Control
Now try running the experiment with Proportional Only control
- What is the effect of changing the proportional band of the controller?
- Under what circumstances does the process oscillate?
- Does the process return to its setpoint?
- What would you recommend as being the best setting for the proportional
controller?
Remember to introduce a disturbance by making a change to at least one of the parameters below
Proportional Integral Control
You should have noticed that using proportional only control has a number of
disadvantages. Using your chosen optimal value of proportional band found from
the previous experiment (or altering it if you think you got it wrong!), try
running the experiment with the full Proportional and Integral (P+I)
control and think about the following questions :
- What problems associated with Proportional control are eliminated by
using P+I control?
- What is the effect of changing the Proportional Band now?
- What is the effect of changing the Integral (reset) time?
- What would you recommend as being the best settings for the PI controller?
Remember to introduce a disturbance by making a change to at least one of the parameters below
Conclusion
- What do you conclude as being the best method and the best controller
settings for controlling the level in a vessel? Have a think and then
click here!
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Virtual Control Laboratory
