System Design Flashcards
Atomic Elements
The smallest USEFUL elements into which the system can be decomposed
Usually these are the elements that would be represented on a purchase order or a bill of materials
Definition of a “System Design”
System design is an evolutionary process, progressing from an abstract notion to something that has form and function, is fixed, and can be reproduced in specified quantities to satisfy a designated consumer need
The focus of system design are the phases preceding the production phase of the life cycle
Product Breakdown Structure
A full decomposition of a system into the atomic elements that make it up
Leveraging Precedence in System Design
Part of having a realistic set of requirements means that you are looking for technological precidence. While the architecture itself can be novel/unprecedented, the technological elements that make it up must have some level of technological precedence
“Architecture”
System Architecture
Architecture is defined as a graphical
model or representation that:
1. Expresses the structural framework of a system or entity’s components, their relationships, and operational, behavioral, and physical interactions internally and externally with its Operating environment;
2. Incorporates the views and viewpoints of its stakeholders;
3. Alleviates their concerns.
- An architecture exposes key features of
a system, product, or service
*System Architecture is always based on the design of previous systems (concept of precedence)
*Requires cross-domain collaboration
Importance of “Precedence” when developing a system architecture
Mission Elements v. Enabling Elements
– Mission system elements exist to directly accomplish the mission objectives.
– Enabling systems exist to support the mission system in accomplishment of the mission objectives. Roles include deployment, training, maintenance, resupply, etc.
Architecting
Architecting formulates and conceptualizes a viable set of candidate structures. Focus is on
the system form
Engineering
Engineering applies mathematical & scientific methods to evaluate architectures and select compatible and interoperable components for the design solution.
Designing
Designing translates the system design solution into drawings, models, algorithms, etc. suitable for code development and system fabrication, assembly, integration, & test.
Block Definition Diagrams (BDDs)
The most commonly used SysML diagram, a BDD describes the relationship among blocks (e.g., composition, association, specialization) and block properties
* The BDD can depict structural relationships among blocks. The relationships are as important as the blocks themselves.
* BDDs are used throughout the system life cycle
– stakeholder needs analysis,
– requirements definition
– architectural design
– performance analysis,
– test case development
– and integration
Architecting v. Engineering v. Designing
Architecting, Engineering, and Designing have an iterative, sequential workflow that is highly
collaborative and interdependent
Top-Down Design
Refers to the preliminary design of a system. Starting with the top-level goals and working down to lower-level behaviors and components
*System design progresses from high levels of abstraction to lower levels of abstraction in an
iterative (vs. linear/sequential) fashion.
– Most initial system designs will have varying granularities for different portions of the architecture as some component designs will be known (or dictated)
System Specification
Interfaces
Represents the
External Interfaces
Represent connections between the internal components of the SOI
Internal Interfaces
Represent connections between the internal components of the SOI
Four types of ‘exchanges’ over interfaces
1) Power (energy flowing from one system to another)
2) Space (two systems physically in contact with one another: 2D/3D static supports)
3) Data (two systems communicating with one another: requests, prompts, displays, acknowledgments, PII, uploads, downloads)
4) Mass (two systems passing material, usually fluid: fuel, coolant, air)
Rule of Thumb when it comes to interfaces
1) The fewer the better
2) Keep the interfaces simple
Interface Matrix
Parts Tree
A Parts Tree details all the physical components of a system, from the largest assembly to the smallest part. Its purpose is to provide a complete inventory of each individual component necessary to assemble the system, supporting tasks like manufacturing, quality assurance, and supply chain management
Organized by physical hierarchy, the Parts Tree arranges components in descending order, from large assemblies to smaller parts. This structure supports physical assembly and maintenance since each part’s relationship to the system is clearly documented.
Typically goes into high detail, including every physical part down to small fasteners and individual components. This makes it suitable for tasks that require exact physical specifications.
Used in inventory control, procurement, and assembly operations, where each part’s presence, quality, and specification are crucial.
Product Breakdown Structure (PBS)
The PBS, on the other hand, focuses on the system’s functional and operational elements, dividing the product by subsystem rather than individual parts. It helps teams understand how each subsystem contributes to the product’s functionality, making it especially valuable in design, system integration, and functional analysis
The PBS is organized by functional hierarchy, detailing major subsystems or elements and their contributions to the overall system function. This structure helps ensure each functional aspect is designed and integrated, rather than focusing purely on physical components
Generally stops at the subsystem level and doesn’t specify every physical component, focusing instead on ensuring functional completeness. Lower levels of physical detail are less relevant here unless they impact overall system function.
Used in early design and functional analysis, ensuring each subsystem or functional area meets overall product requirements and contributes to the system’s intended purpose.
