Clarifying the Problem: Deriving Functional Models

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Clarifying the Problem Deriving Functional Models

• BE20-Engineering Design w/ Computer Applications
• Week 5 11-February-2004

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Todays Administrivia

• Due today
• Team Memo 3 on Objectives Tree
• Individual HW probs. 3.7 3.8
• Functional models of products
• Professional skills refresher
• Project management
• Communication
• Assignments (Due 18-Feb-2004)
• Team memo 4 Derive a functional model for your
  self-propelled vehicle
• Individual assignment 4.3

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Objectives Trees vs. Functional Models

• In our last lesson, we created Objectives Trees
• Objectives are be words, they are qualities
  the object should have
• Clients tend to speak in terms of objectives
• In this lesson, we will create Functional Models
• Engineers tend to speak in terms of functions
• The functions of a product are what the product
  does without considering any particular solution
• Identifying the basic functions an object does,
  and then determining solutions for these
  functions separately, leads to better solutions
  for the overall problem
• Two levels of functions Overall functions and
  sub-functions
• We document the product function with a block
  diagram known as a Functional Model

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Why Create and use Functional Models?

• Places the emphasis on what has to be
  accomplished rather than how
• It makes clear the various sub-systems or
  functions that need to be solved in order to
  solve the entire problem
• Enhances the creativity of the design team by
  allowing them to focus on one sub-function at a
  time
• Sub-functions may be derived from objectives tree
  (or customer needs)

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Functional Model Definitions

• Functional model
• It is a picture, a graphical representation
• The overall function of a product is sub-divided
  into smaller, more elemental (i.e. atomic)
  sub-functions
• The sub-functions are connected by the flows on
  which they operate
• Sub-functions
• Simpler expressions of part of the products
  overall function
• Expressed in verb-object form at a consistent
  level of detail

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Functional Model Definitions (Visual)
A functional model is a graphical representation
of the functions a product performs on its inputs
and outputs
Overall function of a product is sub-divided into
smaller, sub-functions
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Functional Model Basics

• A functional description is a combination of a
  function (verb) acting on a flow (object)
• Function - the operation that the product
  performs on a flow or a set of flows to transform
  it from its input state to its output state
• Flow - a material, energy or signal that is used
  by or affects the product
• Think of a flow as anything that is input to the
  product or an output of the product
• For more information
• Chapter 4, particularly section 4.1

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Functional Model Basics (2)

• Functional description form Function (Verb)Flow
  (Object)
• Examples of functional descriptions

The overall function of a bumble ball
The overall function of a student
The overall function of a mechanical pencil
Function
Flow
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Functional Model Simple Example

• Think about designing a better mouse trap
• What functions must it accomplish?
• Take a few minutes as a team and brainstorm about
  mousetrap functions
• View the diagram below
• Does it match your ideas? Note the verb noun
  construction.
• Can you see that solving these functions
  separately can lead to a wider range of potential
  designs?

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Functional Modeling Procedure

• Step 1 Create a black box model of the product
• State overall function of product
• Use your objective tree high level objectives to
  help determine the overall function
• Identify input and output flows
• Possibly related to lowest level objectives

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Functional Modeling Procedure (2)

• Step 2 Break down overall function into
  sub-functions
• Follow each input flow through the product and
  imagine what function the product performs on the
  flow
• The Zen approach BE the flow
• For example, for the flow of disc, the associated
  sub-functions might look like

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Functional Modeling Procedure (3)

• For the flow of electrical energy, what is its
  associated sub-functions?

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Functional Modeling Procedure (4)

• For the flow of human energy, what is its
  associated sub-functions?

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Functional Modeling Procedure (5)

• Step 3 Connect the sub-function chains together
• This may require additional sub-functions or
  connecting flows

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Functional Modeling Procedure (5.1)

• Step 3 Connect the sub-function chains together
• This may require additional sub-functions or
  connecting flows

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Functional Modeling Procedure (5.2)

• Step 3 Connect the sub-function chains together
• This may require additional sub-functions or
  connecting flows

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Functional Modeling Procedure (6)
Skip ahead

• Step 4 Define the system boundary
• This ensures that only product sub-functions are
  considered for future design work

aim disc
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Four Steps to a Functional Model
Additional Explanation

• Step 1 Create a black box model
• Identify overall function
• Express overall function in verb-object form
• e.g. learn material, pass course, obtain degree,
  etc.
• Identify input/output flows

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Four Steps to a Functional Model (2)
Additional Explanation

• Create function chains
• Follow Zen approach - BE the flow
• Think of every operation that the product does to
  the flow
• List all the operations as sub-functions
• Express sub-functions in a common language, i.e.
  the functional basis
• Order sub-functions temporally (with respect to
  time)

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Functional Model Example
Additional Explanation

• Dustbuster function chains

Objective Powerful Related to input flow of
electricity
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Four Steps to a Functional Model (3)
Additional Explanation

• Step 3 Connect the function chains together
• Connect function chains for each flow
• Add/remove sub-functions as necessary
• Step 4 Define the system boundary
• Differentiate between user and device functions
• Final check
• Check if all objectives are covered
• Make sure each objective is met by at least one
  sub-function
• If not, sub-functions (or chains) must be added

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Functional Model Example (2)
Additional Explanation

• Aggregating the Dustbuster function chains

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Functional Modeling Summary

• Whats the difference between objectives and
  functions?
• Objectives tell us what the final product will
  be, what qualities it will have
• Functions tell us what the object will do,
  without regard to any particular form
• Functions will always relate input to output
• Functions capture the transformation that takes
  place between input and output
• Though the difference may seem subtle, it is a
  very important distinction

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Assignments

• Team
• Prepare a functional model for the tennis ball
  server
• As a guideline, your functional model should have
  approximately 15-20 device sub-functions
• Differentiate between user and device
  sub-functions
• Attach the functional model (drawn on a computer
  application) to a cover memo describing the
  important functions of your project
• Update your teams Gantt chart, showing your
  status on the project
• Individual
• Problem 4.3

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Professional Skills Segment

• Refresher on team professional skills
• Project management
• Communication

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Project Expectations
Project Management Skills

• Identify appropriate project expectations for
  your team

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Planning Meetings
Project Management Skills

• Place the following meeting activities in the
  appropriate category

Identify important issues and prepare an agenda
Actively listen and ask questions if confused
Set time and location of next meeting so everyone
knows
Adhere to the agenda and avoid side conversations
Prepare to contribute and participate
Accept follow-up assignments
Summarize meeting outcomes and identify next steps
Know all team members schedule
Clarify misunderstandings and avoid personal
conflicts
Plan to arrive ON TIME and stay until the end of
the meeting
Support and encourage contributions from team
members
Self assess how your team is doing suggest ways
to improve
Complete any assignments from last meeting
Share ideas and information and participate fully
Before meetings
During meetings
End of meetings
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Active Listening
Communication Skills

• Decide if the following actions make you an
  active listener