Aerospace Systems Engineering Chapter 3 Modeling and Process

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 1

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 2

Taxonomy of Models Model Categories Model Subcategories Typical Systems Engineering Questions Physical Full-scale mock-up Subscale mock-up Breadboard How much? How often? How good? Do they match? Quantitative Analytic Simulation Judgmental How much? How often? How good? Qualitative Symbolic Textual Graphic What needs to be done? How well? By what? Mental Explanation All of the above! Table 3. 1 Chapter 3 - Modeling and Process Modeling 3

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 4

CORE System & Process Models • • • ER --> Relationship FFBD/EFFBD --> Functional N 2 --> Interface, Data Flow Hierarchical --> Physical, Tracebility IDEF 0 --> Functional, Organizational Chapter 3 - Modeling and Process Modeling 5

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) Chapter 3 - Modeling and Process Modeling Analogy with System Development Process 6

IDEF 0 • Genesis: Air Force’s Integrated Computer. Aided Manufacturing (ICAM) program • Variation of Structured Analysis & Design Technique (SADT), Sof. Tech - David Ross • ICAM Definition • Integrated Definition for Function Modeling (by: Air Force Wright Aeronautical Lab) Chapter 3 - Modeling and Process Modeling 7

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

IDEF 0 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 ICOM – – 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 Figure 3. 1, 2 Chapter 3 - Modeling and Process Modeling 9

IDEF 0 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 10

IDEF 0 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 11

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

Feedback Semantics of Functions Figure 3. 4 Chapter 3 - Modeling and Process Modeling 13

IDEF 0 Page Structure Page Number(s) A-1 A-0 A 1, A 2, . . . A 11, A 12, . . . , A 21, . . . Figure 3. 5; Table 3. 2 Page Content Ancestor or external system diagram Context or system function diagram (contains A 0) Level 0 diagram with first tier functions specified Level 1 diagrams with second tier functions specified Level 2 diagrams with third tier functions specified … Chapter 3 - Modeling and Process Modeling 14

IDEF 0 Functional Decomposition Figure 3. 6 Chapter 3 - Modeling and Process Modeling 15