In week 4 we focus on project planning and concept evaluation, which is part of the conceptual design stage
In the model used by Mattson and Soreson, Concept Development is the second phase
- Opportunity development
- Concept development
- Subsystem engineering
- System refinement
- Producibility refinement
- Post-release refinement
The primary goal of concept development is to create a viable conceptual design that solves the given problem.
Documents presented during class
Reading
Review Chapter 5 in the textbook by Mattson and Sorenson. Read sections from Part 2
- Catalog search
- Controlled convergence
- Multivoting
- Prototyping
- Scoring Matrix
- Screening Matrix
Activities for Lecture 4
Review Internal Search, External Search and Functional Decomposition
- Internal search: Team uses its own experience and creativity to imagine solutions
- Brainstorming and other idea-generating activities
- External search: Team seeks ideas from external sources
- Internet search
- Catalog search
- Consulting experts
- Review applicable standards
- Window shopping
- Functional decomposition
- Identify functions necessary to achieve goals without confining functions to a particular implementation
- Alternative decompositions correspond to alternative (high level) conceptual designs
Internal and external search activities are concentrated at the start of the project. It is natural and helpful to be open to inspiration from internal and external search activities throughout the design process, e.g. even during subsystem engineering. However, the team needs to accept the outcome of the conceptual design decision-making process and avoid re-doing conceptual design once subsystem engineering has begun. Therefore, it is very important that the team makes a good choice for its conceptual design because it is very expensive to backtrack.
Outcomes of the internal and external searches are a list of candidate ideas. The process is described as tidy and sequential, but in fact the team has imagined details, discussed implementation ideas, and started with decision-making process. That's OK. It is good to anticipate.
Again:
It is very important to clearly and decisively complete prior tasks before working on future tasks. Our immediate current task is to *complete the conceptual design*.
Evaluating Ideas
Evaluating ideas is the reductive complement to generating ideas. There are many ways to evaluate concepts, both formal and informal, qualitative and quantitative.
During the Concept Development phase, the goal is to efficiently evaluate concepts without doing detailed design work. Making decisions at this point is important and consequential.
Informal methods
- Let the boss decide (by whatever method)
- Popularity contests
- Multivoting based on personal judgement or experience
Formal methods
- Customer feedback
- Testing with minimum viable product (MVP)
- Use experience with prototypes and field testing
- Focus groups
- Internal evaluation
- Concept screening
- Concept scoring
- Prototype testing
Prototype evaluation
Timing of concept evaluation can have a big impact on costs and success.
Early tests can be used to
- Evaluate feasiblity
- Expose unanticipated flaws
- Determine performance limits
- Obtain data used to calibrate analytical models
Refer to supplemental notes on prototyping
Concept Screening
To evaluate ideas the design team can use screening techniques to compare competing options based on estimates of performance. Obviously skill at estimating performance will be easier with accumulated engineering experience. For specific techniques, refer to the Controlled Convergence, Scoring Matrix, and Screening Matrix method in part 2 of the textbook by Mattson and Sorenson.
Ullman describes a multi-stage screening process for identifying the most promising concepts. Dieter and Schmidt describe these methods in greater detail.
- Absolute scale rating
- Feasibility screening: Using "gut feel" whether idea is likely to work
- Technology readiness: Is the technology for the solution easy to obtain or implement?
- Go/no-go screening: Does or can the solution meet the customer requirements
- Relative rating: Decision Matrices
Concept Scoring
The Pugh method, also known as decision matrix method, is a way to quantitatively compare concepts. The method
Simple engineering analysis can also be used at this stage. Like all activities in the concept evaluation stage, engineering analysis should be as efficient as possible. The precision of the analysis should be sufficient to decide whether an option is feasible, which is information that can be used in screening methods described above. During concept evaluation at the conceptual design phase, the team should not invest effort in optimizing any option.
Engineering analysis at the conceptual design state should also focus setting boundaries on expected performance of the system as a whole or of potential subsystems. For example, you can think about total energy budget (electrical input, motor torque, total load), weight budget (total and distributed to subsystems), cost (components, materials), time resources (build or buy, which goals need to be compromised or balanced). This information will provide concrete and rational guidance to the screening methods described above.
Prototypes, especially simple mock-ups, are helpful in evaluating ideas. The prototypes can have limited functionality, or in the case of a cardboard and tape mock-up, may have no practical function other than providing a physical embodiment of an idea. Questions at this stage could be, "Is this too big to handle?", "How do you hold this when you use it?", "Should there be a button or switch to control the operation?", "Can this be made to fit into the available space?", "Should the user be able to separate these parts or should it be a single sealed unit?", "Does this look like something else I've seen before?" "What is the first thing you think about when I hand this to you?" etc.
Although the evaluation process is aimed at vetting and reducing possibilities by eliminating unlikely paths to success, it is also very likely to be the source of new ideas.
Introduction to Project Planning
- Work breakdown structure
- Assigning and working with roles and responsibilities