project p12016 magy yasin | dave taubman | curt beard | oliver wing | aalyia shaukat | stu burgess |...
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Project P12016
Magy Yasin |Dave Taubman |
Curt Beard |Oliver Wing |
Aalyia Shaukat |Stu Burgess |
Jeff Chiappone |
Multi-Disciplinary Senior Design 1
Project Manager Lead CE/EE Project Engineer Project Engineer Project Engineer Project Engineer Lead ME/IE
Systems-Level Design Review | Oct. 7, 2011
Agenda• Meeting Goals • Project Background
o Objectiveso Customer Needso Spec Overviewo Team Overview
• Functional Analysis
• Concept Development
• Physical System Architecture
o Arriving at this System • Risk Assessment
• Schedule
Goals
• Gain Feedback: positive or negative specific feedback on design
• Identify Problem Areas: based on feedback, develop a
road map of problem areas and how to solve them • Discover Ways to Improve: our models, our
assumptions, our methods
• Answer the Question: does our design do what our customer needs?
• Acknowledge Readiness: to move onto detail design
10/6/11
"Design and Fabricate a Navigation Aid for the Visually Impaired/Blind"
• Navigates a person from any point on the second floor of the
Gleason Building to any other point on the floor• Map is based on RFID tags which define rooms and landmarks• Utilizes Dijkstra's Routing Algorithm to determine optimal route• Device does not rely on auditory cues• Does not impair use of cane or guide dog
Project Objective
Customer Needs
Customer Need #
Importance Description
CN1 1 Navigates blind person from any location to any other location on a single floor within a building, where destination has a room number.
CN2 1 Navigates efficiently
CN3 1Operates successfully under conditions that the user is likely to encounter, such as: destination change while en-route, user goes "off the map," user stops using the device while en-route, device fails, ect.
CN4 1 Portable and untethered
CN5 1 Gives non-visual, non-Braille instructions/feedback
CN6 1 Easy to use
CN7 2 Easy to train user
CN8 1 Comfortable and safe to use
CN9 1 Operates for an entire day without recharging
CN10 1 Battery is easy to replace
CN11 2 Doesn't distract the user or others near the device
CN12 2 Doesn’t draw attention to the user
CN13 1 Hands are not needed to carry device
CN14 1 Parts cost < 700 dollars
CN15 2 Navigate blind person to drinking fountain, restroom, or other Important location that may not have a (known) room number
CN16 3 Work independently of system of units (SI vs English)
Device Specifications
Specification Unit of Measurement Ideal Value
Size Inches <= 4x2x1
Weight Pounds <= 0.025
System Cost Dollars < 700
No. of 20-min Navigation Intervals per Charge # >= 10
Charge Time Hours <= 8
Battery Replacement Time Minutes < 1
Map Read/Load Time Minutes < 1
Wrong Command Provided to User Frequency < 1/1000
Commands are Non-Visual Y/N Yes
Distinct and Distinguishable Commands # >= 5
Distinct Inputs From User # >= 4
Verification of User Input Provided Y/N Yes
Size of user input Digits 6
Duration Between Commands Seconds <=2
Device Specifications
Specification Unit of Measurement Ideal Value
Operating Conditions: Temperature Degrees (Celsius) 0-40
Operating Conditions: Relative Humidity Percentage 0-100
Noise Generated By Device at 3 ft Decibels < 50Impact Resistance: Fully Functional After Drop From
Set Height Feet 3
Hands Required to Carry System # 0
Hands Required to Position/Use System # 0,1
Attachment Time (by user) Minutes < 1
Removal Time (by user) Minutes < 1
Training Time (1st time) Hours < 1
Wear Time Without Discomfort Hours > 8
Device is Untethered Y/N Yes
Enclosure Temperature Degrees (Celsius) < 48.8
Tag Interrogation Frequency Seconds < 1
Minimum Tag Read Distance Feet 4
Team Roles
Magy Yasin ISEProject Manager, Ergonomics, Usability/Human Interface, Design
of Experiments, Maintenance and Manufacturing
Dave Taubman EELead EE/CE, RFID Reader Characterization, RFID Reader
Interface to MCU, RFID Antenna Interface
Curt Beard EEImpedance matching, Analog-to-Digital and Digital-to-Analog
Interface, Drive Circuitry, Device Characterization, Board Layout
Oliver Wing CEMCU Selection, Programming, Algorithm Implementation,
Memory Allocation, MCU Development Board Interface and Usage
Aalyia Shaukat EEVoltage and Current sense circuitry, Power Budget Analysis,
Battery Selection, Regulation Circuitry, Sensor Interface Circuitry
Stu Burgess MEAnalysis and Design of Enclosure: CAD, Heat Dissipation, Drop
Test, Manufacturing Enclosure, Cables & Connectors, User Input Device Selection, Attachment Ergonomics
Jeff Chiappone MELead ME/IE, Analysis and Design of Tactile Feedback:
Dynamics, Power, User Perception of Feedback, Cable Routing
Functional Decomposition
What How How How
Input Alternatives
Trackball-style Click wheel Touch screen
Keypad Knob
Input Alternatives – Pros/Cons
Pros Cons
Trackball Less moving parts, higher reliablity Too many “positions”, less intuitive
Click wheel Less moving parts, clicks become memorizableComplex design, may require rebuild or reverse engineering
Touch screen Out-of-the-box functionality, can be made to order, re-programmable
May rely too heavily on “visualization” of gestures,etc.
Keypad Out-of-the-box functionality, can be made to order, waterproof, re-programmable
Some limit on size
Knob Simple to operate, higher reliability Very limited on size, less intuitive
Feedback Alternatives
ElectromagneticLevitation
Hobby Servo with Bracket
Temperature Linear Actuator
Vibrational Motor
Feedback Alternatives – Pros/Cons
Pros ConsElectromagnetic
LevitationIncredibly precise feedback, one moving part
Tech requires extensive research, parts not readily available, very expensive and labor-intensive
Hobby Servo Precise, steady motion Larger, heavier, expensive
Vibrational MotorOut-of-the-box functionality, inexpensive, tinyRequires damping to prevent housing from also vibrating
Temperature A unique experience, no moving parts May require steep learning curve
Linear Actuator PrecisionTend to come in larger sizes, higher weights, expensive
Power Supply/Charging
• What is the easiest way to charge the device?
• What is the most efficient way to power the device?
• Charging:o Wall adapter, Solar Cells, Kinetic Motion, USB
• Powering the Device:o Batteries, Other forms of stored energy
Charging – Wall Adapter
Pros• Dedicated port for charging• Not direction specific• Quick rate of charging
Cons• Additional Port needed to
charge device.o More holes in casing
• Need external wall adaptero Easy to misplace, bulky
Charging – Solar Cells
Pros• Would not need any external
power bricks• Can charge in any location
Cons• Needs to be sunny outside
o Unable to charge at night• Expensive to implement• Not enough current to power
the microcontroller
Charging – Kinetic Motion
Pros• Charge while you move• No external power brick
needed• Can charge in any location
Cons• Need to be moving to ensure
a charge on the deviceo Difficult to charge
• Bulky components needed to implement
Charging – USB
Pros• Fast charging• Uses existing port on device• Simple to implement• Can charge with computer or
with additional adapter• Universal, Inexpensive cable
Cons• Uni-Directional input• Need to be plugged into the
wall or computer
Powering the Device
• Must be easily rechargeable• Batteries have a large advantage over other
forms of power storage.o weight/size to storage density
• Several different types of batteries available
Batteries Available
• Li-Ion – Lithium Ion (80-90%)o Pros: Small, Light, No memory effect, low self dischargeo Cons: High internal resistance, Cell rupture if mishandled
• Ni-Cd – Nickel Cadmium (70-90%)
o Pros: Can be fully discharged, high # Charge cycleso Cons: Expensive, Low energy density, Use of cadmium
• Ni-MH – Nickel Metal Hydroxide (66%)
o Pros: High current drain, low resistanceo Cons: High output voltage, low capacity, long charge time
RFID Interfaces
• Skyetek-SkyeModule™ M9 RFID Reader • Available Interfaces:
o TTL (RS-232) – Requires Host Boardo SPIo I²Co USB – Requires Host Board
SPI – Serial Peripheral Interface
Pros• Simple• Can achieve high data rates• Simpler and more efficient in
point to point communicationo Lack of device addressing =
less overhead• Well documented interface
libraries
Cons• No flow control• Supports only one master
device• No hardware slave
acknowledgment
http://www.eetimes.com/discussion/beginner-s-corner/4023908/Introduction-to-Serial-Peripheral-Interface
I²C - Inter-Integrated Circuit
Pros• Two wire connection• Good for >1 Slave device
Cons• Previous team was unable to
successfully implement design.
• Slaves need a unique address
Routing Algorithm
System Level Diagram
Sensor data
• The RFID reader can determine which tags are within range, but not their distances
• The RFID reader has a sleep mode that consumes less than 2% of the active power requirement
• Data from the compass and the accelerometer can be collected over time to determine a change in position
• Goal: use the accelerometers and the compass to provide most of the feedback, and use the RFID tags occasionally to verify the location
Map representation
• Major considerations include the size of the map file (limited memory space on the board), the ASCII character set requirement spec, and the 1000 maximum tags spec
• Maps consist of:o tags, each with an ID (12 bytes) and X and Y coordinates in
inches or centimeters (range: 0~4000);o map vertices (e.g., rooms, water fountains, bathrooms, hall
intersections), each with X and Y coordinates;o walking paths between vertices, which include the start and
end verticeso assumption that the device is currently only being used to
navigate one floor of one building
Map representation (continued)
• Possible solution: use base64 notation (ASCII-safe but still small)o Tags, with their large ID fields, will likely comprise the largest
part of the fileo With base64 notation, tag IDs require 16 'digits' and the
coordinates will use 2+2 'digits' = total of 20 bytes per tago The MCU memory must be able to accommodate up to 1000
tags = 20KB minimum per map (restricts MCU choice!)• Store the graph underlying the map of destinations and paths
densely (low connectedness)
Microcontroller selection
Selection: Arduino Nano (weak in clock speed, but sufficient in memory and I/O options, and can start programming quickly) with TI MSP430F5529 as a backup choice
Figure 1. Flowchart representing the Dijkstra algorithm. To convert to A*, changethe step that selects the vertex with the lowest distance value to instead pick
the lowest distance value/heuristic combination.
Morph Chart
Functions Options
Attach to user: location
Waist Neck Wrist Arm Hand Back Head Leg/ankle
Attach to user: method
Velcro Belt Watch band Spandex/sleeve Headband Backpack Glove
Send output to user Lorentz Mag-LevVibrational motorPressure wristband
Servo spineCombo of
vibration & touch
Receive user input Keypad KnobRetro-style
telephone dialTouch screen Scanner
Power all components: charge
methodWall adapter Solar cells USB Kinetic motion
Power all components: battery
Lithium Ion NiCad NiMH
Microcontroller Arduino PIC TI OMAP
Pugh Chart
Specs and Customer needs System I System II System III System IV
Datum
Charge time 0 - 0 -Non-visual commands 0 0 0 0Verification of user input provided 0 0 0 0Hands to carry system 0 0 0 0Hands to position/use system 0 0 0 0Attachment time 0 + + +Removal time 0 + + +Training time (input) 0 - + +Tag interrogation freq. 0 0 0 0Distinct inputs from user - - - -Noise at 3 ft. - 0 0 -Training time (output) - 0 0 +Size + + + -Weight + + + -Cost + - - -Device is untethered + + + +Number of 20' nav intervals on full charge + + + -Time to read map from electronic source + 0 + +Wrong command (direction) provided + + + +Distinct & distinguishable + 0 0 +Time between commands + 0 0 +Impact resistance + + - -Wear time without discomfort + - + -Doesn't draw attention + - + -
# of +'s 12 8 11 9 N/A# of -'s 3 5 3 9 N/A# of 0's 8 10 9 5 N/A
Total Score 9 3 8 0 N/A
System I System II Sytem III Sytem IV End configuration.:
Keypad Knob Touchscreen Scanner Keypad
Arduino PIC TI OMAP Arduino Arduino
Vib. Motor Pressure Wristband Pressure Points Vib. Motor/Touch Combo Vib. Motor
Li-Ion NiMH Li-Ion NiMH Li-Ion
Ankleband Headband Glove/arm Necklace Glove/Arm/Wrist
USB Power Solar Cell Wall Adapter Kinetic Motion USB Power
Input Decision: Keypad
• Size: LxWxD: 2” x 1.58” x .5” (smallest)• Weight .016 lbs/7.5g (smallest)• Manufacturer/Source: Sparkfun Electronics, adafruit.com,
futurlec.com, • Cost: $3.95 (cheapest) • Material: aluminum, plastic, silicone• Connection: 7 output pins • Meets Requirements: can be programmed to suit, some models
come with Arduino microcontroller support, requires only one hand to use
• Reliability: Low actuation force, waterproof, millions of actuations per life of unit
Pre-made vs. Build to Suit:
• Pre-made keypads: o May allow for design-specific layout, more intuitive to usero May be able to design a smaller keypad than most pre-made
models, but:o They may also have long lead times for manufacturers to
produce• Built to suit keypads:
o Require less time incorporating into team’s specific designo Have built-in Arduino support
Custom Keypads May Be:
Radial Directional
Functional and Ergonomic Slim and Compact
Custom Keypads Manufacturers:
• Top Bound USA• Baran• Miller Dial• Gray Hill – *very thin rubber keypads (.2”), also
sells individual keys with switches
Feedback Decision: Vibrating Motor• Size: 0.5” long• Weight .004 lbs/2 g (lightest)• Manufacturer/Source: Amazon, TrueSupplier, futurlec.com, • Cost: $2.99 (cheapest) • Material: aluminum, copper, synthetic foam• Connection: 2 copper leads• Meets Requirements: provides distinguishable output to user,
voltage allows for change in intensity, can be placed in multiple locations for diverse feedback communication
• Reliability: only one moving part, compact, suppliers guarantee millions of revolutions per life of unit
Decision - Charging Using USB
• The user will already have to be familiar with programming the device via USB
• Existing USB charging controllers are well documented and special IC’s already exist.
Decision - Li-ion Battery
• High capacity• Best size to weight ratio• Fast charging and long battery life• Charge lasts a long time
Example USB Li+ Charger
• Uses existing IC’s to implement and control charge and output voltageo Source: http://www.maxim-ic.com/app-notes/index.mvp/id/3241
Decision - SPI
• Pre-made functions and well documented library by Arduino
• Simple and easy to use for single Master-Slave configuration
• Previous team unable to implement I²C successfully
Questions?
Heat Dissipation
Assumptions• Housing is a rectangular box with four
equal sides• Bottom surface is well insulated• Uniform air temperature inside housing• Uniform temperature gradient on walls• Heat generated by all electrical
components lumped in to a single Qsource
QSideQTop
QSide
QSide
QSide
Qsource = 4*Qside + QTop
Conduction: Q = (k*A*∆T) / t
Convection: Q = (h*A*∆T)
Basic Equations
Additional Assumption• Qsource is floating within the box
Heat Dissipation – Initial Analysis
Calculations• Using a known ambient temperature and known Qsource temperatures can be
calculated by analyzing and summing up heat flow through each individual wall• Heat transfer through each wall is a simple 2D analysis• Convective coefficients will need to be estimated• Equations can be put in MatLab to quickly recalculate for different geometry/materials• Very conservative and simple analysis• If calculated temperatures are excessive a secondary analysis will be done
Tcomp Tair,i Twall,i Twall,o Tair,o
Qsource
Heat Dissipation – Secondary AnalysisAdditional Assumption• Qsource is attached to one of the walls• Designate sections of wall to only conductive or convective heat transfer
Calculations• Similar to previous analysis with addition of direct conduction of heat from the
components to the wall• If temperatures are still found to be excessive will need to consider use of more
conductive materials and/or incorporate heat sinks to reduce resistances in the thermal circuit
Tcomp Tair,i Twall,i Twall,o Tair,o
QsourceQwalls
Qcomponent conduction
Housing Material
Material Density(g/cm3)
Elastic Modulus(GPa)
Thermal Conductivity (W/(m*K))
Steel 7.8 200 52
Aluminum 2.7 69 210
Carbon / Epoxy 1.6 142, 10 ~1.5
E-Glass / Epoxy 2.1 45, 12 ~1.5
Polyester 1.4 3 ~0.2
• Results of thermal analysis, drop tests and projected budget will help determine whether to use metals, polymers, composites or a mix of materials
Human Factors•Interaction between user and product. •Quick Response •Constraints: to prevent mistakes being made –Input •Different sizes and textures•Input data twice –Output•Feedback should be differentiable. –Device shape: should help determine placement•Asymmetrical Shape
Adjustability
•Ensure product is secure–Position–Elastic material•Spandex–Adjust product first time to user–Release button •Ensure button is not easily pressed.
Testing - Types
• Drop Test (ME)• Thermal (ME)• Noise (ME)• Usability (ISE)• Comfort (ISE)• Attachment/Detachment (ISE)• Training Time (ISE)• Software Functionality (CE)• Battery (EE)• Amount of power used (EE)
Testing - User Interface
•Feedback Capability: Determine distance between vibrational motors–Order feedback parts–Determine minimum distance needed to sense different feedbacks•Input Error: Determine input error rate–Collect data on the number input error observed from sample
Testing - Methodology
Drop Test• Obtain sample sheets of possible materials
• Cut sample to approximate size of one side of housing
• Attach weight equal to projected weight of device to samples
• Perform drop tests
Thermal Testing• Obtain thermocouples and heater capable of outputting power
equal to that of the device • Place heater inside manufactured housing unit and monitor
temperatures until steady state is achieved
Testing - Program
• Unit testing• Self-testing (power-on self test)• Algorithm correctness• Application testing
o Cooperation with sensor and feedback interfaceso Testing directional feedback on-site without mechanical parts
Use log files or USB communication to check resultso Comprehensive error cases – user input, sensor input, map
data
Risk AssessmentRisk Causes Effects L S I Preventative Action Owner
Losing saved work
Not using version control systems
Not creating backups in a separate location
Fall behind schedulePossibly forced to re-design 1.5 3 4.5 Use version control continuously
Make backups on other media Team members
Algorithm fails during user trial
Poor programmingNot enough consideration
for error cases
Device malfunctionsIncorrect signals cause discomfort
through directional feedback2 2 4
Test a wide range of plausible error cases, including hardware failure and disallowed user inputDocument program design and
code thoroughlyRedesign with simpler or more
deterministic algorithm
Oliver
Housing Breakage Material too weakMachining/Assembly errors
Re-evaluate material choicePartial/Full rebuild of housing 2 2 4
Order extra materialSimulate drop test with sample
materials before buildStu
Interfaces don't work as planned
Poor planningInadequate research
Inadequate programming ability
Forced to redesignFall behind schedule
More work during weeks 6-10Unhappy customer
2 2 4
Research thoroughly during design phase
Look for alternative interfaces in the same parts
Lead engineers
Hardware fails
OverheatingPhysical damage
Improper testing and handling
Replacement of parts shrinking budget 2 2 4
Order extras of fail-prone piecesKnow the parts' operating limits
Be nice to the deviceLead engineers
Parts arriving lateFaulty shipping method,
shipping scheduleloss of time, schedule 1 3 3 order early
each team member, according to duty
Risk Assessment
Schedule
Schedule Continued
Questions?