ch3-system development processmercury.hangkong.ac.kr/rsplab/data/system... · engineering...

1 Copyright@Young K. KwagSystem Engineering

Ch 3System Development Process

Lecture Series #3

SYSTEMS ENGINEERINGGraduate Course


Introduction

Modern engineered systems come into being in response to social needs or because of new opportunities offered by advancing technology, or both

system development characteristics

- Complex effort

- Meets an important user need

- Usually requires several years to complete

- Made up of many interrelated tasks

- Involves several different disciplines

- Usually performed by several organizations

- Specific schedule and budget


System Life Cycle

System Life Cycle: Development → Production → Operation → Disposal

Development of a systems engineering life cycle model- Life cycle models subdivide the system life into half dozen or

so steps that separate major decision milestones.

• System Development Life Cycle Model:

- Department of Defense Model (DoD 5000)

- International Model ISO/IEC 15288

- National Society of Professional Engineers Model


System Development Process

• System Development Characteristics:

- Complex Efforts, Important User’s need

- Development Duration, Many Interrelated Tasks

- Involve different discipline, perform by several organizations

- Specific schedule and budget

• System Development Life Cycle Model:

- Department of Defense Model (DoD 5000)

- International Model ISO/IEC 15288

- National Society of Professional Engineers Model


• Department of Defense Model (DoD 5000) : Military- Four Phases model including Mission Need Determination in 2000

- Concept and Technology Development (Concept/Component Dev.)

- System Development and Demonstration (Integration/Demo)

- Production and Deployment, - Operation and Support

• International Model ISO/IEC 15288 : Commercial- International Org. for Standardization and Int’l Electro-technical Commission

- Six stages: Concept, Development, Production, Utilization, Support

and Retirement

• National Society of Professional Engineers Model- Six stages: Conceptual, Technical Feasibility, Development, Product

Preparation, Full-Scale Production, Production Support

• System Engineering Model:- 3 stage, 6 phases: Concept, Engineering, Post development

System Development Life Cycle Model


Comparison of System Life Cycle Model


System Life Cycle Stages• Concept Development Stage- Establish the system need

- Explore feasible concepts

- Select preferred system concept

• Engineering Development Stage- Validate new technology

- Transform concept into hardware and software designs

- Build and test production model

• Post Development Stage- Produce and deploy the system

- Supports system operation and maintenance

- Each stage may be further divided two or three phases

- Life cycle of software-intensive systems ( in Ch 13)


Principal Stages in System Life Cycle


Concept Development Stage – 3 phases

• Needs Analysis Phase -- Define and validate the need for a new system

- Demonstrate its feasibility and defines system operational requirement

• Concept Exploration Phase -- Explore feasible concepts

- Define functional performance requirements

• Concept Definition Phase -- Examine alternative concepts

- Select preferred concept on basis of performance, cost, schedule, and risk

- Define system functional (A) specifications


Concept Development Stage - Diagram


Engineering Development Stage – 3 phases

• Advanced Development Phase -- Identify areas of risk

- Reduce risks through analysis, development, and test

- Define system development (B) specification

• Engineering Design Phase -- Perform preliminary and final design

- Build and test hardware and software components (ICs)

• Integration and Evaluation Phase- Integrate components into production prototype

- Evaluate prototype system and rectifies deviations


Engineering Dev. Stage - Diagram


Post Development Stage & Phases

• Production Phase -- Develop tooling and manufactures system product

- Provide system to user and facilities initial operations

• Operation and Support Phases -- Support system operation and maintenance

- Develop and support in-service updates

• Integration and Evaluation- Integrate components into production prototype

- Evaluate prototype system and rectifies deviations


Evolution of System Life Cycle


Principal Participants in System Eng.

Aerospace System Dev. Example


Evolution of System Representation


System Engineering Method

• Requirement Analysis -- Identify why requirement are needed

• Functional definition -- Translate requirements into functions

• Physical Definition -- Synthesize alternative physical implementation

• Design Validation -- Models the system environment


System Engineering – Top-Level Flow

• Four basic activities:

- Requirements analysis

(Problem Definition)

- Functional definition

(Functional Analysis and Allocation)

- Physical definition

(Synthesis of Physical Analysis and Allocation)

- Design validation

(Verification, Evaluation)


System Engineering Method Flow


Requirements Analysis (1) 보조자료

• Organization and interpretation- The system model , which identifies and describes all design choices made

and validated in the preceding phases.

- Requirements (or specifications) that define the design, performance, and interface compatibility features of the system or system elements to be developed during the next phase.

- Specific progress to be achieved by each component of the engineering organization during the next phase

• Clarification, Correction, and Quantification- Stated requirements are often incomplete, inconsistent, and vague

- To be varied with the nature of the system, its degree of departure from predecessor systems, the type of acquisition process employed, and the phase itself


Functional Definition (2) 보조자료

• Translation into Functions:- Selecting, subdividing, or aggregating functional elements

- Identification and description of all functions to be provided

- To be reflected in system functional specifications

• Trade-off Analysis:- Inductive process in which a set of postulated alternatives are examined and

the one judged to be best for the intended purpose is selected

- Trade-offs involve: the comparison of alternatives with those that aresuperior in others

- To be necessary to explore a sufficient number of alternative implementations

• Functional Interactions:- The early identification of all significant functional interactions

- “modular”

- The identification of all external interactions and the interfaces


Physical Definition (3) 보조자료

• Synthesis of Alternative System Elements- Decisions regarding the specific physical form:

include choice of implementation media, element form, arrangement, and interface design

are made by the use of trade-off analysis

• Selection of Preferred Approach- To be necessary to define a set of evaluation criteria and establish their

relative priority

- 1. All viable alternatives are considered,

- 2. A set of evaluation criteria is established, and

- 3. The criteria are prioritized and quantified where practicable

• Interface Definition- Definition and control of inter face both internal and external

- Adjustment to the parent elements will be required


Design Validation (4a) 보조자료

• Modeling the System Environment- In the concept development stage:

the model is largely functional

- In later stags of development:

various aspects of the environment may be reproduced

- Effort required to model the environment of a system to be considered at the same level of priority as the design of the system itself, and may even require a separate design effort comparable to the associated system design activity.

• Tests and Test Data Analysis:- 1. All critical system characteristics need to be stressed beyond their

specified limits to uncover incipient weak spots.

- 2. All key elements need to be instrumented to permit location of the exact sources of deviations in behavior.


Design Validation (4b) 보조자료

• Tests and Test Data Analysis (continued…)- 3. A test plan and an associated test data analysis plan must be prepared to

assure that the requisite data are properly collected and are then analyzed as necessary to assure a realistic assessment system compliance.

- 4. All limitations in the tests due to unavoidable artificialities need to be explicitly recognized, and their effect on the results compensated or corrected for, as far as possible.

- 5. A formal test report must be prepared to document the degree of compliance by the system and the source of any deficiencies.

• Preparation for the Next Phase- Each phase produces a further level of requirement or specification to serve

as a basis for the next phase.

- Documentation of the design decisions made in course of the current phase

- Establishment of the goals for the succeeding phase


System Engineering Method in Life Cycle


System Eng. – Spiral Life Cycle Model

- An iterative application of the system engineering method

- The continuing review and updating of work performed and conclusion reached in the prior phase of the effort


Testing throughout System Development• Unknowns- “Known unknowns”:

to be evident at the beginning of the project

can be resolved easily

- “Unknown unknowns”:

to be only identified later

could be serious problem

• Transforming the Unknown into the Known- Experience gathered during previous system developments and

supported by a high degree of technical insight and a “what if …” attitude

- It is unwise to wait until the design is fully implemented before determining where or not the approach is sound.

- System-level rather than a component-level decision


System Test and Evaluation

• Is it O.K ? - Design Engineer and Test Engineer

• A process to identify unknown design defects -- Verifies resolution of “ known unknowns”

- Uncover “ Unknown unknowns” (unks-unks) and their causes

. Late resolution of unknowns may be extremely costly

. Test planning and analysis is a prime systems engineering

responsibility

• Most intensive use of testing is the last phase of system development, integration and evaluation, which will be covered in Ch 8. & Ch 10.


Successful System Engineer’s Character

• Successful System Engineer:1. Enjoy learning new things and solving problems

2. Like a challenge

3. Are skeptical of unproven assertions

4. Are open minded to new ideas

5. Have a solid background in science and engineering

6. Have demonstrated technical achievement in a specialty area

7. Are knowledgeable in several engineering areas

8. Pick up new ideas and information quickly

9. Have good interpersonal and communication skill


Homework #3• Prob. 3.5

What steps can the system engineer take to help ensure that system components designed by different technical group will fit together and interact effectively when assembled to make up the total system?

Discuss in terms of mechanical, electrical, and software system elements.

• Prob. 3.7Table 3-3 illustrates the evolution of system representations during thesystem development process. Describe how the evolution of requirement documents illustrate the materialization process described in Table 3-1.

• Prob. 3.8Scientific Method vs. Engineering Method

Look up a definition of he “scientific method” and relate its steps to those postulated for the systems engineering method. Draw a functional flow diagram of scientific method parallel to that of Fig. 3-5.

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