Title: Early Stages of Design
1Early Stages of Design
- CPE x350-01 F07
- Lynne Slivovsky
2Outline
- Overview of design process
- A variety of models
- Requirements Specification
- (Chapter 3 of Ford Coulston)
3Phases of Design
- Engineering Your Future, Great Lakes Press
- Stage 1 Identify the problem/product innovation
- Stage 2 Define the working criteria/goals
- Stage 3 Research and gather data
- Stage 4 Brainstorm/generate creative ideas
- Stage 5 Analyze potential solutions
- Stage 6 Develop and test models
- Stage 7 Make the decision
- Stage 8 Communicate and specify
- Stage 9 Implement and commercialize
- Stage 10 Perform post-implementation review and
assessment
4IEEE Std 1220-2005
5IEEE Std 1220-2005
6IEEE Std 1220-2005
CPE 350
CPE 450
7Ullmans Mechanical Design Process
- Phase 1 Specification development/planning
- Phase 2 Conceptual design
- Phase 3 Product design
- Phase 4 Production
- Phase 5 Service
- Phase 6 Retirement
8Phases of the Design Cycle
Specification Development
Redesign
Conceptual Design
Retirement
Disposal
Product Design
Service
Production
9Ford Coulston
Image taken from Design for Electrical and
Computer Engineers, Ford and Coulston
10Design Process Models
- MANY formal models for the design process
- IEEE Std 1220-2005 IEEE Standard for Application
and Management of the Systems Engineering Process - The Mechanical Design Process, McGraw Hill, 1997,
2003 - Design for Electrical and Computer Engineers,
Ford and Coulston, McGraw Hill, 2007 - Take Home Points
- Do not use a hobbyist/hacker approach
- Be explicit with the process model you select
- (e.g., in your documentation)
11Inside or Outside the Box?
How your problem is constrained.....
..determines the variability in its design
Many Possible Designs
Few Specifications
Many Specifications
One Design
Where do specifications comes from?
12Requirements Specification (Ch 3)
- Requirements Setting Process
- Marketing Requirements
- Engineering Requirements
- Taxonomy of Requirements
- Developing Requirement Specifications
- Example
- Criteria
13Requirements Specification
-
- The requirements specification identifies those
requirements that the design must satisfy in
order for it to be successful.
14Requirements Setting Process
- Three stakeholder groups
- Customer
- Gives raw (marketing) requirements
- Gives feedback based on usability, marketing
- Environment
- Imposes constraints and standards
- Technical Community
- Gives feedback based on engineering knowledge
15Requirements Setting Process
Customer
Marketing, Customer Feedback
Customer Representation
Develop System Requirements
Constraints and Standards
Technical Feedback
Technical Representation
Technical Community
Environment
16Marketing Requirements
- Short statements that address a user need
- The system should be small
- The positioning should be accurate
- Not specific enough to complete a design
17Engineering Requirements
- Engineering requirements are short statements
that address a technical need of the design. - The system should be able to supply 50W of power
18Engineering Requirements
- Four Properties
- Abstract
- Verifiable
- Unambiguous
- Traceable
19Engineering Requirements
- Abstract
- A requirement should specify what the system
should do, not how it will be implemented - Beware of preconceived concepts for solutions
- Example
- In getting more people from Oakland to San
Francisco, the requirement should not be to
design a bridge. - It could be transport people from one side of
the river to the other.
20Engineering Requirements
- Verifiable
- There should be a way to measure (or demonstrate)
the requirement is met - Allows us to continually answer the question
Are we building the system correctly? - Example
- One requirement might be the flying robot must
be able to hide 3.5 meters below the surface. - A better requirement could be the flying robot
must be able to determine its ground based
position with a tolerance of 2cm.
21Engineering Requirements
- Unambiguous
- Each requirements must have a single meaning,
stated with short complete sentences - Example
- Not The robot must operate with a battery life
of 1 hour. - Maybe The robot must operate for a minimum of 1
hour.
22Engineering Requirements
- Traceable
- Each requirement should be traceable to marketing
requirements - Example
- Engineering requirement
- Must be manufactured for less than 2.00
- Marketing requirement
- Must be affordable
23Engineering Requirements
- Realism
- Realistic
- Justified
- This comes from experience (e.g. technical
feedback from the technical community).
24Engineering Requirements
- Constraints
- In design, a constraint is a special type of
requirement - It is a design decision imposed by the
environment or a stakeholder that impacts or
limits the design -
- Windows platform must be used
- Note that constraints can violate the
abstractness property - Can make a design decision that adheres to the
constraint - In choosing between windows and Unix, windows is
chosen because 99999 out of the 100000 customers
use windows.
25Engineering Requirements
- Standards
- Established ways of doing things to ensure
interoperability - Ensure products work together
- Safety, testing, reliability, communications,
data formats, documentation, design methods,
programming languages, connector standards,
metastandards - Knowing details of standards is often required at
the Implementation stage of development
26Taxonomy of Requirements
- Identifying Engineering Requirements
- Structured workshops and brainstorming sessions
- Interviews, surveys, questionnaires
- Observation of processes or devices in use
- Competitive benchmarking and market analysis
- Prototyping and simulations
- Research and technical documentation review
27Taxonomy of Requirements
- Performance
- Functionality
- Economic
- Energy
- Environmental
- Health and Safety
- Legal
- Maintainability
- Manufacturing
- Operational
- Political
- Reliability and Availability
- Social and Cultural
- Usability
28Criteria
- The requirements provide an minimum set of
objectives that the design must meet. - What if you have two designs that meet all
requirements? Which one should you use?
29Criteria
- Criteria provide a method for comparing different
designs. - Example robot speed (m/s)
- They should have all the properties of
engineering requirements. - They are often confused with requirements. BUT
THEY ARE DIFFERENT!
30Criteria
- Example
- Requirement
- The dimensions of the prototype should not exceed
6 x 4 x 1.5 - Criteria
- The dimensions of the prototype (smaller is
better) in inches