PROJECT P12016Multi-Disciplinary Senior Design I

Detail Design Review

November 11, 2011

AGENDA

Meeting Goals Project Background

Objectives Specification Functional Analysis

Final Design Analysis Risk Assessment Bill of Materials Preliminary Test Plan MSD II Proposed Schedule

MEETING GOALS

Is attachment method feasible? What thickness of housing snaps is

necessary? Will they fail?

Is the design truly inconspicuous? Will bottom of housing hold up to fastener

loads? Where do we stand on our specifications?

Creating a navigation system aid for blind and deaf people walking in an unfamiliar building.

Need to allow the user to continue to use a cane or guide dog.

Navigate a person from any point on the 2nd floor of the Gleason Building (09)

Without the use of Braille. No hands should be used to carry system

REQUIREMENTS

PROJECT BACKGROUND

SIZE ≤ 4X2X1 INCHES WEIGHT ≤ .25 LBS COST < $700 ATTACHMENT TIME < 1 MIN DETACHMENT TIME < 1 MIN TRAINING TIME < 1 HOUR WEAR TIME WITHOUT DISCOMFORT > 8 HOURS INTERNAL TEMPERATURE < 120 DEG F

SUMMARY OF MAJOR SPECIFICATIONS (PAGE 4)

PROJECT BACKGROUND

FINAL DESIGNEXTERNAL OVERVIEW (PAGE 6)

Housing TopKeypad

Mini-USB Charging Port

Elastic SleeveFront Vibrational Motor (Right)

Thumb Hole

Tie-Downs to Housing/Elastic

Rear Vibrational Motor

Front Vibrational Motor (Left)

Battery Door

Foam Padding

(Approximation of Actual Use)

On/Off Slide Switch

Highlighted numbers indicate BOM designation

3

8

4

4

4

8

17

19

Housing Bottom

Wiring Feed Hole

FINAL DESIGNEXTERNAL DIMENSIONS, INCHES [MM]

7.8 [200]

3.7 [93]

2.4 [60]

0.9 [24]

2.2 [56]

2.4 [60]

1.4 [35]

(vib motors)

(thumb hole)

FINAL DESIGNEXPLODED VIEW

Housing Components

Electronic Components

Fasteners & Spacers

Ergonomic Attachment

FINAL DESIGNPLASTIC SNAPS & FASTENERS

Front Section:

M3 Cap Screw, 12mm Long

Shim + Adhesive

4.5mm Hex Nut

6mm Nylon Spacer

2mm Nylon Spacer 4X Connections

14.4mm

4X Snaps

4X Holes

2X Snaps

2X Holes

5X Snaps

20, 21

16

12

13

15

FINAL DESIGNELECTRONICS AND INTERNALS

Antenna Connection

PCB Bottom:

Connections for Front Vibrational Motors

Connections for Front Vibrational Motors

PCB Bottom:

RFID Reader

Printed Circuit Board (PCB)

Right Side Section:RFID/PCB Connection

Battery

6

5

Mini USB Charging Port

Engineering Specifications

Max Volume: 8 in3

Max Weight: 4 oz

WEIGHT & VOLUME VS SPECIFICATIONS (PAGE 8)

ANALYSIS

Component Weight (oz)

Battery 1.04

RFID Reader 0.60

Keypad 0.26

PCB* 0.21

Misc. Components 0.20

Vibration Motors 0.04 x 3

Compass/Accelerometer

0.03

Housing** 1.02

Total 3.48* PCB weight based on anticipated volume times material density

** Housing weight based on volume taken from CAD model times material density

Section Volume (in^3)

Main housing 7.63

Battery Section 0.61

Total 8.24

1. What: 3D Printer

2. Where: RIT Brinkman Machine Labs

3. How Much Material: Approximately 1.5 cubic inches total

4. What Kind of Material: ABS Plus (industrial thermoplastic polymer)

5. How Much Money: $10/inch^3 -- roughly $15 total

6. How Long: About 8-15 hours per part

Method: Geometry imported to 3D printer

3D Printer builds model layer-by-layer with resin

2. Cantilevered, floating parts supported by soluble secondary material, washed away in ultrasonic bath

MANUFACTURING METHOD

ANALYSIS

ASSEMBLY METHOD

ANALYSIS

1 2

3 4

5

1. Insert cap screws through holes in bottom housing. Place 2mm spacers on screws.

2. Insert RFID Reader, place 6mm spacers on top of reader. Snap power switch in place.

3. Insert PCB. Bond shims to top of hex nuts and tighten components in place.

4. Bond Foam Padding to bottom of housing

5. Snap keypad in place on top half of housing

ASSEMBLY METHOD

ANALYSIS

6

7

8

9

6. Loop elastic straps through slits in bottom half of housing. Attach external motors to PCB.

7. Loop elastic straps through top half of housing and snap together the two halves of the housing.

8. Connect battery to PCB and insert in to enclosure.

9. Snap battery door in to place.

1. Battery door is removed via pressing snaps into housing until they clear mating holes:

2. Battery (still wired) is removed from cradle:

3. Disconnect battery from connections on PCB:

4. Insert connectors from new battery:

5. Place new battery in cradle:

6. Snap battery door back into place:

BATTERY REPLACEMENT

ANALYSIS

1 2

3 4

(Cradle)

5 6

(Connectors)

1. Elastic creates tight fit, fits broad range of sizes

2. Thumb holes orient device, prevent rotation

3. Elastic is inexpensive, can be found locally

4. Elastic is reinforced near housing, stabilizes interface there

5. User slides arm through elastic sleeve, inserts thumb through hole

6. Vibrational motors align with two sides of wrist, rear motor rests on upper-middle arm

7. Vibrational motors are sewn into pockets on elastic sleeve, wiring is routed through pockets to prevent tangling

ATTACHMENT METHOD

ANALYSIS

1.4 [35]

*Inches [mm]

5.9 [115]

2.0 [50]

After visiting the Brinkman Lab we determined a wall thickness of 1.5mm (~0.06”) should provide an adequate balance of strength, weight and flexibility

Testing will be necessary to confirm durability of housing and snaps. We have room in the weight budget to add material if necessary.

Current Material Volume of ~1.7in3. A total cost of about $17 for the housing leaves room in the budget for multiple iterations if necessary.

Design considerations to strengthen housing include: increased wall thickness, adding ribs or adding patches of extra material at weak points

Shims at the top of internal screw columns will contact the bottom of the keypad to provide structural support as buttons are pressed.

STRUCTURAL DURABILITY

ANALYSIS

Shim

Force of user input

STRUCTURAL ANALYSIS – HOUSING STRESS

ANALYSIS

ABS Plus Properties Value

Density [kg/m^3] 1040

Young’s Modulus [MPa]

2250

Tensile Strength [MPa] 37

Simulation Parameters Value

Loading 2N Force

Location of load front

Location of fixed support

bottom, fasteners

Results: Largest stress is 2.09e5 Pa; < rated Tensile Strength of 3.7e7 Pa Educated assumption that plastic will survive shock (i.e. heavily simplified drop condition) Largest stresses occur in corners of opening where keypad will actually add support

Fixed Load

STRUCTURAL ANALYSIS – STRESS IN SNAPS

ANALYSIS

σ max = 257 Pa

1- Keypad side

σ max = 428 Pa

2- Keypad rear

σ max = 1661 Pa

3- Top body

σ max = 397 Pa

4- Battery door

1

3

2

4

Setup

Results: All stresses in snaps < rated Tensile Strength of 3.7e7 Pa

Assumptions•Bottom surface is well insulated•Housing is rectangular•All electronics lumped as a single heat source the size of the RFID Reader•Heat source is a plate floating in the box•Free convection on a vertical plate outside the housing•Free convection in an enclosure inside housing•Halve calculated values for convective coefficients•RFID Reader running on high 100% of the time (worst case)•RFID Reader running on high 100% of the time (average case)

HEAT DISSIPATION

ANALYSIS

QSideQTop

QSide

QSide

QSide

Specifications•Max air temperature inside: 120°F•Max RFID Reader Operating Temp: 158°F

HEAT DISSIPATION

ANALYSIS

Calculations•Used equations and tables from Heat Transfer text to calculate convective coefficients inside and outside of the housing•Modeled problem as steady state 2D heat transfer through 5 walls•Using known values for the power source and ambient temperature, solved equations for temperature throughout the housing•Calculated results using MatLab

Tcomp Tair,i Twall,i Twall,o Tair,o

Qsource

Results•Worst Case:

1. Inside Air Temp: 107.2°F2. RFID Reader Temp: 181.5°F

Average Case1. Inside Air Temp: 80.7°F2. RFID Reader Temp: 99.8°F

HUMAN FACTORS

ANALYSIS

KeypadRotate keypad to ease pressure on wristTactile feedback “Bump-Dots” on KeypadInput data twice

Correct OrientationAsymmetrical housingThumb hole

1 2 3

4 5 6

7 8 9 0

*

#

MOTOR PLACEMENT

ANALYSIS

92% 98% 100%98%90% 100%

OUTPUT TESTING

ANALYSIS

Testing concluded that it was very difficult to distinguish between different pulse lengths.

Based on test results, altering the time between vibrational pulses will result in distinguishable outputs.

RISK CAUSES EFFECTS L S I ACTIONOWNE

R

Snaps Fail Physical damage

Forced to redesign 1 3 3

ANSYS analysis before manufacturing housing to ensure that the snaps will

work

Jeff, Stu Improper design

Device orientation shifts

Device straps are not secure enough around

users arm

The user will misunderstand

output, resulting in incorrect navigation

2 3 6

Design housing to ensure device will not rotate

(straps are tight enough; housing shape design)

Magy

Vibrational indicators difficult to distinguish

Vibration patterns are too similar

User will not understand device feedback; will

not know which direction to navigate.

1 3 3

Testing Analysis on: motor placement, vibration

pattern distinguishing, and voltage necessary to

feel vibrations

Magy Motors are placed too

close to each other

Vibration response is hard to detect

MAJOR RISKS (PAGE 9)

RISK ASSESSMENT

BILL OF MATERIALS (PAGE 10)

ONE TIME TESTS (PAGE 12)

PRELIMINARY TEST PLAN

Number of hands needed to place/carry device (S20, S21): No hands should be used to carry device One hand should be used to place and use device

Impact resistance (S19) Device is functional after 3 ft. drop

Internal housing Temperature (S27) Less than 120 degree F

Device Attention Test Noise Generated (S18)

Noise generated from the device should be < 50 db.

STATISTICAL ANALYSIS NEEDED 95% CONFIDENCE INTERVAL

PRELIMINARY TEST PLAN

Input Reliability (S17) Number of input mistakes made by user H0: μInput ≤ 1/100

Output Reliability (S10, S11, S26) Number of outputs not properly understood H0: μOutput ≤ 1/100

Training Time (S24) H0: μTraining ≤ 60 min

Attachment/detachment time (S22, S23) H0: μAttachment ≤ 60 sec

H0: μdetachment ≤ 60 sec

Change battery time (S7) H0: μChange Battery ≤ 60 sec

User Comfort (S25) Wear time without user discomfort H0: μComfort > 8 hrs

Go to Schedule

GANTT CHART (PAGE 14)

MSD II PROPOSED SCHEDULE

QUESTIONS