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Assignment 4

Web-Lab Assignment #4
Modelling FOPDT systems

1. This assignment is going to be done with Excel.

2. Click on "Tutorial" for a detailed description of writing an FOPDT model in Excel.

3. Add in parameters that change the deviation variables to real variables. This is done by adding the Input baseline to the (deviation) input and the Output baseline to the (deviation) output. See how the graphs change.

4. Use that Excel spreadsheet, only add the columns Input and Output to a data file from the step experiments. Do this by highlighting Columns B & C & "Insert/Columns." Then open one of your laboratory data files, copy Columns A, B and C and then Paste them into Columns A, B & C of the Model Excel spreadsheet. Set the parameters so that the Experimental Input Function is exactly duplicated by your model. Adjust the axes so that you can see your data range effectively. Then mess with the gain, dead-time and time-constant to get the model-output to agree as much as possible with the Experimental Output Function
To adjust the parameters so that the model curves, fit the data curves as nearly as possible. Here is a suggested order of doing this:
  • Set input baseline and output baseline so the baseline parts of the model curves agree with the experimental data.
  • Set td and A so that the model input curve agrees entirely with the experimental input curve.
  • Set K, to and tau so that the model output curve agrees with the experimental input curve as close as possible. Suggested values of these come from your previous analysis.

5. Send an e-mail (report) within the next few days. (Click on "report" to get instructions.)

**** CONTINUOUS IMPROVEMENT ***

For suggestions and feedback,

contact Jim Henry - Lab-Master Send E-Mail to Jim Henry

7 August 1996; Last revised 11 February 1998

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