Aerospace Systems Engineering

1. Aerospace Systems Engineering Chapter 3 – Modeling and Process Modeling By Dr. Sartuk KARASOY Middle East Technical University skarasoy@metu.edu.tr The viewgraphs are mainly courtesy of Dr. Dennis Buede. Chapter 3 - Modeling and Process Modeling

2. Models • Incomplete representation of reality • Answers questions • Types of questions • Definitional (inputs, outputs, functions) • Descriptive, predictive • Normative (decision making mechanism) Chapter 3 - Modeling and Process Modeling

3. Taxonomy of Models Chapter 3 - Modeling and Process Modeling Table 3.1

4. Modeling Languages • Semantics: signs and symbols • Syntax: way in which signs and symbols are put together “A map is not the territory that it represents.” Chapter 3 - Modeling and Process Modeling

5. CORE System & Process Models • ER --> Relationship • FFBD/EFFBD --> Functional • N2 --> Interface, Data Flow • Hierarchical --> Physical, Tracebility • IDEF0 --> Functional, Organizational Chapter 3 - Modeling and Process Modeling

6. Model Development Process • Questions to be answered • Modeling method selection • Design, test and refinement • Validation • Conceptual (theory and assumptions) • Operational (output behavior) • Data (inputs for design, test and use) Analogy with System Development Process Chapter 3 - Modeling and Process Modeling

7. IDEF0 • Genesis: Air Force’s Integrated Computer-Aided Manufacturing (ICAM) program • Variation of Structured Analysis & Design Technique (SADT), SofTech - David Ross • ICAM Definition • Integrated Definition for Function Modeling (by: Air Force Wright Aeronautical Lab) Chapter 3 - Modeling and Process Modeling

8. IDEF Family of Methods Chapter 3 - Modeling and Process Modeling

9. IDEF0 Semantics & Syntax • Model • Semantics: Collection of pages • Syntax: Hierarchical structure • Page • Semantics: Boxes and arrows • Boxes: Functions, processes, activities • Arrows: Flow of material or data • Inputs enter from left • Controls enter from top • Outputs leave from right • Mechanisms enter from bottom • Syntax: Interaction of functions via material & data • Transforms inputs into outputs • Using guidance of controls • As performed by mechanisms ICOM Chapter 3 - Modeling and Process Modeling Figure 3.1, 2

10. IDEF0 Model • Answers definitive questions about the transformation of inputs into outputs by the system • Establishes the boundary of the system on the context page. This boundary is explicated, if needed, as a meta description. • Has one viewpoint; the viewpoint is the vantage or perspective from which the system is observed. • Is a coordinated set of diagrams, using both a graphical language and natural language. Chapter 3 - Modeling and Process Modeling

11. IDEF0 Rules & Guidelines • Rules • Conservation of inputs, controls, outputs & mechanisms • Every function has a control and output • Guidelines • 3 to 6 functions per page arranged diagonally • Control-oriented functions placed at top left • Major output functions placed on bottom right • Arcs & functions are decomposable • Feedback is defined by arcs moving from bottom right to top left Chapter 3 - Modeling and Process Modeling

12. Arrow Semantics Chapter 3 - Modeling and Process Modeling Figure 3.3

13. Feedback Semantics of Functions Chapter 3 - Modeling and Process Modeling Figure 3.4

14. Page Number(s) Page Content A - 1 Ancestor or external system diagram A - 0 Context or system function diagram (contains A0) A0 Level 0 diagram with first tier functions specified A1, A2, ... Level 1 diagrams with second tier functions specified A11, A12, ..., A21, ... Level 2 diagrams with third tier functions specified ... … IDEF0 Page Structure Chapter 3 - Modeling and Process Modeling Figure 3.5; Table 3.2

15. IDEF0 Functional Decomposition Chapter 3 - Modeling and Process Modeling Figure 3.6