Emeka Akpaka
Kayla Cole
Lindsay Johnson
Justin LaMar
Christine Lochner
Nick Stewart
11/13/2014
Preliminary Detailed Design Review
1
Engineering Requirements
Importance Source
9
CR1
9
CR1
3
3
3
3
3
3
9
3
3
9
Function
System
Operation
Engr. Requirement (metric)
Provide 90 degree detection range in front of user
Unit of Ideal
Measure Value
Degrees
90
Binary
Pass
Lbs.
1
System
Operation
System
CR2
Portability
Signal detection of obstacles via haptic feedback (motion in
handle)
System
Assembly
Decrease amount of visible hardware by 50% compared to
P14043
Pieces
10
8 hour rechargeable battery (minimum battery life)
Hours
8
Collapsible into 8-10" sections
Inches
8
USD
125
Minutes
1
Feet
10
psi
5
Binary
Pass
in
1.3
CR3
CR4, System
CR5 Operation
System
CR6
Portability
System
CR7
Cost
System
CR9
Usability
System
CR10
Operation
System
CR12
Operation
System
CR12
Structure
System
CR12
Structure
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Adds no more than 1 lb. to standard white cane
Manufacturing cost $125 or less
Keep cane collapse/re-open time less than 1 minute
Horizontal detection range
Maximum pressure
Handle contents fit within handle mock up envelope
Maximum handle grip diameter
Preliminary Detailed Design Review
Comments/Status
Will be achieved by a combination
of the user's sweeping motion and
2, 25 degree range sensors
Less small parts would improve the
manufacturability of the product
Didn’t want to stall motor
Research on typical cane diameters
2
Critical Design Parameters
Number
Parameter
Unit of Measure
Ideal Value
Marginal Value
Owner
Involved
CDP1
Cane handle outer diameter
in
1.3
1.5
ME
ME
CDP2
CDP3
CDP4
CDP5
CDP6
CDP7
CDP8
CDP9
CDP10
CDP11
CDP12
CDP13
CDP14
CDP19
CDP20
CDP21
CDP22
CDP23
CDP24
CDP25
CDP26
CDP27
CDP28
CDP29
CDP30
Handle length
Lag time between detection of an obstacle and feedback to the user
Handle grip stress
battery size
Total cane weight
Small number of pieces in handle assembly
Hollow space volume within handle
Input voltage of linear actuator
Voltage input type of motor
OD of rollers
Number of buttons
Dimensions of motor
Stall current of motor
Power for micro controller
Voltage input for the sensor
Sensor location in handle
Total horizontal detection range
Angle to mount the sensors
Total power draw
Size of battery
Weight of battery
Output of battery
Handle material
Lateral detection range
Wall thickness of handle
in
s
psi
mA-hr
lb
Number
in³
V
Binary
mm
Number
mm
A
V
V
Binary
Meters
Degrees
W
in
N
V
Binary
degrees
in
11
0.343
5
8 times the total current draw
11.5
<10
8.08
6
DC
6
2
10 x 12 x 35.27
1.6
5
5
<15
7.6
--------7
-------------
ME
EE
ME
EE
All
ISE
ME
ME
ME
ME
All
ME
ME
EE
EE
All
EE
EE
EE
EE
EE
EE
ME
EE
ME
ME
EE
ME
EE
All
ISE/ME
ME/EE
ME/EE
ME
ME/ISE
All
ME
ME/EE
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Preliminary Detailed Design Review
3
10 ft from user
78.45
>= 5
Bridge Nylon
134 < x < 178
0.1
ABS
0.08
All
All
3
System Level Proposal: Actuated
Buttons In Handle
Pros:
 Easy learning curve
 Feedback awareness
 Potential to have versatile
cane handling
Concerns:
 Handle must be designed
carefully to ensure versatile
cane handling
 More moving parts
P15043 Systems Design Review
4
10/2/2014
Subsystems
Motor
 Buttons
 Microcontroller

 Accelerometer
Battery
 Sensor

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Preliminary Detailed Design Review
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Subsystem Risk Breakdown
Subsystem
Risk
Motor
Medium
Buttons
Medium-high
Microcontroller
High
Battery
Medium
Sensor
Low
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Preliminary Detailed Design Review
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Handle Repair Feasibility

Goal: Make handle repair simple and easy for user or technician

Analysis: Main parts of system: Sensor, Battery, Microcontroller and Motor
Instead of replacing the entire cane, small sections of
the cane can be replaced instead

Solution: Design parts of the cane to be detachable or easily
accessible. One of the main parts that could break due to
weathering is the sensor. The current design was made with that in
mind making sure that it could be easily accessed for repair or
replacement
**Examples of these design considerations will be shown in later
slides**
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Preliminary Detailed Design Review
7
Linear Motor Research
 A solenoid motor turned out to be the only type of linear motor we
could find within our price range and close to our dimension
specifications.
Pros:
• Cost Effective
• Enables us to use original button design
Concerns:
• Constant current draw (will drain battery)
• Excessive heat build-up
• Solenoid housing is slightly larger than or preferences, so the
handle design would need to be slightly modified.
Conclusion:
Using a linear motor is not feasible, and the motor type and button
motion must be re-designed.
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Preliminary Detailed Design Review
8
Motor Selection & Design Change
Original
Button oscillation is in and out of the cane
(pressing motion)
Change
Button Oscillation is side to side (sliding motion)
Linear Actuator
Gear Motor (From P14043’s Design)
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Preliminary Detailed Design Review
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More on Design Change
This new button motion will be similar to P14043’s cane during the middle
sensor feedback simulation:
IMG_1598.MOV
Click above for
video of feedback
Motor Selected:
298:1 Micro Metal Gearmotor HP
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Preliminary Detailed Design Review
10
Button Placement Feasibility
Goal: Place buttons in a way to maximize tactile feedback feeling transmitted to the user
Background:
How the Blind Hold Their Cane
The blind hold their cane with their pointer finger extended down the flat side of the handle
with the rest of their fingers curled around it.
Mechanoreceptors
Mechanoreceptors specialize in sending tactile information to the brain.
Meissner’s Corpuscles:
 Directly beneath epidermis of fingers and palms
 Have rapidly adapting action potentials for shallow skin depression
 Suited for detecting low frequency vibrations and detecting textures moving
across skin
 Accounts for 40% of sensory nerves in human hand
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Preliminary Detailed Design Review
11
Button Placement Feasibility Continued
Figure 2: Two Point Discrimination
Chart. Image taken from source 3.
Figure 1: Distribution of Meissner’s
Corpuscles in the human hand. Image
Figure 3: Indentation threshold
for different areas of the hand.
Image taken from source 3.
taken from source 3.
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Preliminary Detailed Design Review
12
Button Placement Feasibility Continued
Information Learned to Help Guide Design:

Meissner’s Corpuscles make up 40% of sensory nerves on hand.

Meissner’s Corpuscles have a high density in finger tips and an even distribution on other areas
of the hand.

Meissner’s Corpuscles are good at detecting moving textured surfaces (consider textured buttons)

Two point discrimination for the human palm is around10mm.

Two point discrimination for human fingers is around 5mm.

Fingers have a lower indentation threshold compared to the palm.
Sources:
[1] Dario, 2012, “O&M – Orientation and Mobility. Lesson #1: The long white cane.” From URL: http://www.noisyvision.com/2012/03/27/om-orientamento-e-mobilit%C3%A0-lezione-1-il-bastone-biancolungo-2/?lang=en
[2] Purves D, Augustine GJ, Fitzpatrick D, et al., editors. Neuroscience. 2nd edition. Sunderland (MA): Sinauer Associates; 2001. Mechanoreceptors Specialized to Receive Tactile Information.Available from:
http://www.ncbi.nlm.nih.gov/books/NBK10895/
[3] Gardner, E.P., Martin, J.M., Jessell, T.M., “The Bodily Senses.” From URL: http://fisica.cab.cnea.gov.ar/escuelaib2014-neurociencias/restricted/BOOKS/Principles%20of%20Neural%20Science%20%20Kandel/gateway.ut.ovid.com/gw2/ovidweb.cgisidnjhkoalgmeho00dbookimagebookdb_7c_2fc~28.htm
[4] Johansson, R.S., Vallbo, A.B., “Detection of tactile stimuli. Thresholds of afferent units related to psychophysical thresholds in the human hand.” The Journal of Physiology. 1979 Dec. 297: 405-422.
[PubMed]
[5] Tustumi, F., Nakamoto H.A., Tuma Junior. P., Milcheski D.A., Ferreira, M.C., “Prospective study on tactile sensitivity in the hands of a Brazilian population using the pressure-specified sensory device.”
Revista Brasileira de Ortopedia, 2012, 47(3). From URL: http://www.scielo.br/scielo.php?pid=S0102-36162012000300011&script=sci_arttext&tlng=en
11/13/2014
Preliminary Detailed Design Review
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Handle Button Mock-Up and
Demonstration
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Preliminary Detailed Design Review
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New Design Diagram
Bearing
chosen for
rollers
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Preliminary Detailed Design Review
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Spatial Considerations
Handle Motors
Battery
Micro controller
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Preliminary Detailed Design Review
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Material Considerations and
Selection
Filament
Density (lb/in^3) Weight per Pack (lb) in^3 per Pack
PLA
Polyactic Acid
0.043714
2
45.75193302
ABS
Acrylonitrile butadiene styrene
0.0376
2.2
58.5106383
Bridge Nylon Nylon
0.041546
1
24.06970587
Before Drawing Estimation
Maximum Handle
Volume w/ extra
20.90431281
in^3
After Drawing Estimation
Creo Drawing
Handle Volume
11.1094
in^3
11/13/2014
Preliminary Detailed Design Review
Price per Pack Distribution Company
$
48.00
Maker Bot
$
48.00
Maker Bot
$
24.99
taulman 3D
**Can print up to 5 handles with one
spool of filament
17
Proposed Design
Back View of
Cane Handle
Front View of
Cane Handle
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Preliminary Detailed Design Review
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Bottom View of
Wire Housing
Wire Housing
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Preliminary Detailed Design Review
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Front View of
Sensor Cover
Back View of
Sensor Cover
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Preliminary Detailed Design Review
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Going Forward
Add pilot holes and stand-offs for
hardware
 Remove material in certain spaces to
reduce material cost and weight
 Discuss with SME about our final
detailed design

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Preliminary Detailed Design Review
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Sensor Selection Analysis

Based on rough measurements, the max sensor range length must be
at least 8.75 ft.


Based on rough measurements of cane sweeping, the maximum
angular displacement during a cane sweep was determined to be about
45°.





Thus, EZ3 and EZ4 were immediately ruled out.
Thus, the sensor range angle can be no more than 45°.
The angles of the sensors’ ranges were determined, using half of the
max range width and the length at which said width is reached.
Using one sensor on the cane, EZ0 provides a sensor range angle of
25°, which is desirable for the lateral detection range. However, the
height of the sensor range is about 7.5 ft., which provides a range that
is much too tall. Thus, EZ0 was ruled out.
EZ2 provides a sensor range angle of 22°, and a sensor range height
of about 4 ft. This is a desirable height.
Using two sensors, the EZ2 allows the sensor range angle to vary
between φmin = 22°; φmax = 44°. The optimal sensor range angle is
assumed to lie within those values.
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Preliminary Detailed Design Review
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Sensor Test Plan

Read data from sensors using a
development board
 Compare results using an oscilloscope
 Vary the detection object width/height and
distance

Testing of implemented algorithm using
a cane (MSD II)
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Preliminary Detailed Design Review
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Essential Microcontroller
Functionality
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Preliminary Detailed Design Review
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High-Level Circuit Schematic
High level design
 Emphasis on the input/output of the
uController

 UART serial communication for Sensors
 GPIO pins for Motors and Accelerometer
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Preliminary Detailed Design Review
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Decision to design a Printed
Circuit Board (PCB)
Meeting with Carlos cemented the preproduction prototype idea
 Advantages:

 Cheaper in the long run
 Easy to modify/control all aspects of the
uController functionality

Disadvantages:
 Timely
 No previous experience
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Preliminary Detailed Design Review
26
MicroController Selection

Key Selection Criteria:
 Low Cost
 Minimum of 8-bit core size
 5 V input voltage
 Analog-to-Digital Converters
Manufacturer
Unit Price(USD) Core Processor Core Size Speed (MHz) Number of I/O Program Memory Type Voltage Supply (V) Data Converters
Microchip Technology
4.34
PIC
16-Bit
32
65
FLASH
2 - 3.6
A/D 16x10b
Texas Instruments
0.64
MSP430
16-Bit
16
10
FLASH
1.8 - 3.6
Slope A/D
Atmel
0.59
AVR
8-Bit
12
28
FLASH
1.8 - 5.5
A/D 8x10b
Atmel
0.86
AVR
8-Bit
20
16
FLASH
1.8-5.5
A/D 11x10b
Atmel
2.1
AVR
8-Bit
16
23
FLASH
4.5-5.5
A/D 8x10b
Selection: #5 – Atmel’s ATMEGA8
 Meets all of the selection criteria
 Chip commonly used for popular Arduino boards
 Troubleshooting resources readily available
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Preliminary Detailed Design Review
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Microcontroller Schematic
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Battery Selection
Inheriting P14043’s TENERGY Lithium Ion
batteries, Li-18650 3.7V 2600mAh,
recharging circuitry built-in
 Reducing the number of batteries from two
to one; using a boost converter to meet
voltage requirements.
 This solution should have the system
running for around 10 hours.

 2600 mAh/ 300 mA ~ 9 h
○ 200 ma is the maximum predicted current draw,
also at full operating power
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Preliminary Detailed Design Review
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Power Management

Powering:
 Two Motors, two Sensors, uController, and
an Accelerometer
Output of 5V and 150 - 200 mA for ~ 8
hours
 Choice of

 One battery with a boost converter
 Two batteries with a buck converter
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Preliminary Detailed Design Review
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Buck/Boost Decision

Buck Converter (decreases input voltage)
 Has large parts and takes up space on a PCB
 Having two batteries is not ideal (due to handle
space)

Boost Converter (increases input voltage)
 Also takes up room on a PCB
 Only needs one battery to operate

Both provided the necessary power to
components.
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Preliminary Detailed Design Review
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Boost converter it is!
Condensing the real estate in the cane to as
little as possible is invaluable
 Having one less battery also decreases the
manufacturing cost

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Preliminary Detailed Design Review
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Power Management Test Plan

Plug 3.7 V power supply into converter
 Monitor the current draw from power supply
(multimeter)
 Monitor the voltage output (oscilloscope)
 Monitor the current output (multimeter)
 Verify outputs match nominal
values/simulations
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Accelerometer Selection
Kionix KXD94
•
•
•
•
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Preliminary Detailed Design Review
Small package
Low Noise
Low Power
Consumption
Analog voltage output
34
Accelerometer Test Plan

Read data from accelerometer using a
developmental board
 Compare the data using an oscilloscope
 Vary the acceleration of the cane to
determine the accuracy
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Preliminary Detailed Design Review
35
Proposed Design
One battery with a Boost converter to
power all of the devices
 Two EZ2 sensors to acquire data from
the environment
 Accelerometer to determine cane
position relative to user’s direction
 Using an AtmegA8 embedded system to
implement our algorithm and automate
the entire system

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Preliminary Detailed Design Review
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Tentative PCB Layout
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Preliminary Detailed Design Review
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Going Forward

Shift focus towards programming
 Acquire development board to test the
functionality of our concepts in both
programming and hardware
Include a USB interface to charge the
batteries
 Test components, verifying
functionality/quality
 Discuss with SME to finalize PCB design

 Minimization of physical size main priority
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Preliminary Detailed Design Review
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Manufacturing Costing
Requirement: Manufacturing Costs < $125
Manufacturing Cost=
Materials + Labor+ Overhead + Misc.
(fixtures, G&A)
Manufacturing “Elements”:
• Electronics (PCB, sensors)
• Handle (Handle production, motor and
electronics assembly)
• Entire cane
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Preliminary Detailed Design Review
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ABVI Manufacturing Costing
Standard Labor Rate=$10.50/hr
 Manufacturing Cost =

(Material Cost + Labor*) + 11%
• *Time required as determined by time studies
• 11% is the assumed general and administrative rate
• Excludes fixtures, overhead and waste factors
• Materials from an ABVI standpoint would be:
• Handle assembly
• Collapsible Cane
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Collapsible Cane Research
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Tentative Bill of Materials
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Risk Mitigation and Analysis
Importance
Cause
Severity
Effect
Likelihood
Risk Item
Actions to Minimize Risk
General
R1
Battery contact is compromised
Loss of power
Deflection of wire connection
2
3
6
Make sure all components that house wires are
rigid and secure wires sufficiently for cane
movement
R2
User Muscle Fatigue
Pain/discomfort to user
•How hand grips on handle
•Weight distribution of cane
2
2
4
Ergonomics considered in design
R3
Over heating
Damage to system
Harm to user
Insufficient heat dissipation
1
3
3
Perform thermal analysis
R4
Cane malfunction
No feedback delivered to user
Component malfunction or damage
1
3
3
Design for redundancy
R5
Misplaced parts
User frustration
Multiple unconnected in the system
2
1
2
•Make system all one piece
•Create a way separate components can be
stored together when not in use
Sensors
R6
Sensors relay incorrect information to feedback
Confusion and/or danger to user
•Sensor malfunction
•Broken connection
•Problem with program
1
3
3
Test prototype extensively
R7
Sensors hit obstacles when cane is sweeping
•Damage to sensor
•Shift in sensor position
•Sensor falls off
Location of sensors on the cane
2
2
4
Attach sensors in the top region of the cane
R8
Sensors get dusty/dirty
Malfunction
Environment encountered
1
2
2
State in user manual that sensors should be
cleaned frequently
Handle
R9
Water damage
Ruined components
Not waterproof
2
3
6
•Minimize openings
•Put waterproof cover over feedback
R10
Loss haptic motion (when signal is send from
sensors, feedback does not respond with motion)
Feedback not given to user
•Disconnection of feedback mechanism
and motor
•Burnout of motor
2
3
6
•Sufficiently secure roller to motor
•Do analysis to make sure torque is not too high
for motor
R11
Haptic motion is unclear and not intuitive
•User confusion
•Learning curve to use cane
Haptic motion design
2
2
4
Do thorough testing to make sure haptic feedback
relays information clearly to users
R12
Feedback is obstructed by clothing or jewelry (ex.
Gloves)
Decreased feeling of feedback
Location where feedback comes in
contact with the user
1
2
2
Brainstorm ways to minimize clothing/jewelry
obstruction
R13
Motor vibrations harm user
Nerve damage
Magnitude of motor vibration (mm/s)
1
2
2
Do research on effects of vibration magnitude
versus time of exposure. Ensure the motor
ordered is below the limit.
6
•Design handle with an easily removable insert
that contains an organized array of all handle
components
•Use commercially available parts so that they
can be ordered separately
R14
Defines if the handle can be fixed if •Lack of access to inside components
Degree of serviceability and ease part replacement a part breaks or if the user needs to
•Can not remove/replace one part
go out and buy a whole new cane
without removing/replacing another
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3
43
Budget Breakdown
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Schedule
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Next Steps
Detailed design completion
 Systems level test plan
 Finalized BOM
 Prepare for parts procurement

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Questions?
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