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Lab 2: Air heater model adaption
Aim
of the lab
To get knowledge about process
dynamics and adaption of a dynamic model to a physical process.
Equipment
- PC with LabVIEW
- I/O-device
- Air heater
- For air heaters #1-17: [1V, 5V] = [20C, 50C], linearly.
- For air heaters #18-32: [1V, 5V] = [0C, 50C], linearly.
Organization
The lab assignment is accomplished in student groups.
Duration:
Responsible for the lab: Teacher F. Haugen (finn.haugen@hit.no).
Assistance: The teaching assistant and the course instructor.
Assessment
Each group will write a lab journal according to the following guidelines:- Language: English.
- The structure of the journal is the same as in the assignment text. A good start is to copy the assignment text into journal and then add your own contents which consists of screenshots of plots (it is ok to include snapshots of the entire screen) and your short comments in red below the screenshots. Results of setup and configuration of hardware and software should not be included in the journal.
- The journal should not contain summary, preface, introduction or discussion.
- The journal should be written during the lab.
- The journal is uploaded as a PDF file to Fronter before 18.00 the same day.
- The file name should contain the family names of the students in the group, for example. Lab2_Hansen_Pedersen.pdf.
Tasks
Before the start of the lab work, the instructor gives an introduction to the lab. Thereafter, each group fetches an air heater in the storage room next to room C-222.
Note: During the experiments, the fan of the air heater can be set to its maximum speed.
- This subtask is only about simulation (no experiments on
the air heater). The VI' Template_Lab_Model_Adaption_Air_Heater.vi
in the LLB-file (LabVIEW Library) Template_Lab_Model_Adaption_Air_Heater.llb
implements a simulator based on the model of the air heater shown on
the home page of the air
heater, although variables on the home page may differ from those
used in the VI. (The teacher will explain the model at the beginning of
the lab.) The different parts of the model are implemented
using SubVIs (which are like user-developed functions). Open these
SubVIs, and try to understand their contents. Verify, using
pertinent simulations, that the simulator behaves correctly (you will
save a lot of time here by increasing the simulation speed). In other
words: Verify the influence on the simulated responses that the various
model parameters have (these parameters are gain K, time-constant T,
time-delay tau, and environmental temperature Temp_env.
- Implement functions for AI (analog input) and convertion
from V to degree C of the Temp1 measurement (tube outlet temperature)
[degrees
C], and AO (analog output) for the heater control signal u [V].
Plot measured Temp_out and simulated Temp_out in the same chart. Plot u
in its own chart.
- Manually, using experiments, adjust the values of the model
parameters K, T, tau, and Temp_env to the real air heater. You
must plan these experiments so that one experiment can be used to
estimate one parameter only. For example, one experiment is used to
estimate the value of the time-delay.
When you (the group) are content with the parameter estimates, the accuracy of the model should be checked by comparing the simulated and the real temperature responses due to a more or less randomly adjusted control signal.
- Theoretical question: Suppose that you are going to find
the best among a number of model parameter set candidates. Suggest some
mathematical criterion (a number) which can be used to measure how well
the different models fit to the real air heater. (It is not required
that you implement this criterion in your program.)
In the next lecture, the teacher will demonstrate both a LabVIEW program and a Matlab program which automatically finds the best model parameter set from one experiment using "brute force" optimization!
Updated 29 Sept 2015 by Finn Haugen, teacher. E-mail: Finn.Haugen@hit.no.