CHAPTER 5
Principles for Formulating Dynamic System Models

The questions to be answered precede model design. The closed-loop system structure must be reflected in a model. Time delays, amplification, and information distortion must be adequately represented. All constants and variables of the model can and should be counterparts of corresponding quantities and concepts in the actual system. Dimensional units of measure of model quantities must be meticulously consistent. The preferred practice is to begin with the continuous (nonstochastic) structure of system decisions and later add randomness and periodic influences. Model formulation methods should not presuppose system linearity or stability.

BEFORE proceeding with the specific details of equations and a suitable mathematical structure for a dynamic model, we shall discuss some general principles that should guide the construction of a model of an industrial system.


5.1 What to Include in a Model

In practice there will be no such thing as the model of a social system, any more than there is the model of an aircraft. An airplane is represented by several aerodynamic wind-tunnel models for various purposes, plus cockpit arrangement mock-ups, models for maximum stress loading, etc. In designing a dynamic simulation model of a company or economy, the factors that must be included arise directly from the questions that are to be answered.

In the absence of an all-inclusive model, which we are unlikely to achieve, there may well be different models for different classes of questions about a particular system. And a particular model will be altered and extended as each new question is explored.

The skill of the person who undertakes to use a model is tested immediately -- his first decision is to ask pertinent questions having important answers. Trivial questions can but lead to trivial answers. Questions that are too general -- such as how to be more successful -- fail to define an area of attack. Questions that are too restrictive may confine the investigation to an area that does not contain the answer. Questions that are impossible to answer can lead only to disappointment.

Questions to be answered control the content of a model. But how? Again the perception and judgment of the investigator are taxed. He must select, on the basis of his knowledge of the situation, the factors that he believes are pertinent. Here skill and practice in working with the dynamic behavior of systems are important. What the novice often considers paramount may prove to be insignificant. Some factors that are stressed in static analysis may not even exist as essential concepts in a dynamic model. Factors that are omitted, both in static analysis and in ordinary descriptive debates about a problem, may prove to be crucial.

-60-

Notes for this page

Add a new note
If you are trying to select text to create highlights or citations, remember that you must now click or tap on the first word, and then click or tap on the last word.
One moment ...
Default project is now your active project.
Project items
Notes
Cite this page

Cited page

Style
Citations are available only to our active members.
Buy instant access to cite pages or passages in MLA 8, MLA 7, APA and Chicago citation styles.

(Einhorn, 1992, p. 25)

(Einhorn 25)

(Einhorn 25)

1. Lois J. Einhorn, Abraham Lincoln, the Orator: Penetrating the Lincoln Legend (Westport, CT: Greenwood Press, 1992), 25, http://www.questia.com/read/27419298.

Note: primary sources have slightly different requirements for citation. Please see these guidelines for more information.

Cited page

Bookmark this page
Industrial Dynamics
Table of contents

Table of contents

Settings

Settings

Typeface
Text size Smaller Larger Reset View mode
Search within

Search within this book

Look up

Look up a word

  • Dictionary
  • Thesaurus
Please submit a word or phrase above.
Print this page

Print this page

Why can't I print more than one page at a time?

Help
Full screen
Items saved from this book
  • Bookmarks
  • Highlights & Notes
  • Citations
/ 466

matching results for page

    Questia reader help

    How to highlight and cite specific passages

    1. Click or tap the first word you want to select.
    2. Click or tap the last word you want to select, and you’ll see everything in between get selected.
    3. You’ll then get a menu of options like creating a highlight or a citation from that passage of text.

    OK, got it!

    Cited passage

    Style
    Citations are available only to our active members.
    Buy instant access to cite pages or passages in MLA 8, MLA 7, APA and Chicago citation styles.

    "Portraying himself as an honest, ordinary person helped Lincoln identify with his audiences." (Einhorn, 1992, p. 25).

    "Portraying himself as an honest, ordinary person helped Lincoln identify with his audiences." (Einhorn 25)

    "Portraying himself as an honest, ordinary person helped Lincoln identify with his audiences." (Einhorn 25)

    "Portraying himself as an honest, ordinary person helped Lincoln identify with his audiences."1

    1. Lois J. Einhorn, Abraham Lincoln, the Orator: Penetrating the Lincoln Legend (Westport, CT: Greenwood Press, 1992), 25, http://www.questia.com/read/27419298.

    Cited passage

    Thanks for trying Questia!

    Please continue trying out our research tools, but please note, full functionality is available only to our active members.

    Your work will be lost once you leave this Web page.

    Buy instant access to save your work.

    Already a member? Log in now.

    Search by... Author
    Show... All Results Primary Sources Peer-reviewed

    Oops!

    An unknown error has occurred. Please click the button below to reload the page. If the problem persists, please try again in a little while.