The document provides information about designing a prosthetic arm for a classmate who recently lost part of her arm below the elbow. It outlines the design challenge which is to create a low-cost prosthetic device that allows her to perform daily tasks. The device must meet criteria such as costing less than $40 and weighing less than 3kg. It also describes the performance tasks the device will be evaluated on, including tossing balls into targets at various distances and placing objects in a container. Background research activities are suggested to inform the design such as patent searches, reverse engineering, and user interviews.

1. Design Projects

2. Assistive Technology
Technology to assist people with disabilities.

3. Design Challenge – Prosthetic Hand
Scenario
• You are working with a team of engineers from a biomedical engineering
company that specializes in the design and manufacturing of prosthetic
devices. Your team’s challenge is to design a prosthetic hand that can
perform ONE function to help improve the quality of life of the amputee
who uses the prosthesis.
• Example functions to design for:
• holding a pen or pencil
• brushing teeth
• clasping
• picking up an object
• using sign language
• holding a utensil
• throwing
• eating something

4. • Design Constraints
• Time: 1 week!
– Therefore, it is important to agree on a design that is
functional, yet not overly complex.
• Materials: The materials available to you are listed
below:
– foam core, balsa wood, Plexiglas
– wooden dowels, metal rods
– springs, rubber bands, adhesives, such as epoxy, super
glue, hot glue
– sander, saw, drill fasteners, such as eye hooks
– wire, string, laser cutter

5. • Project Deliverables:
– Background research
– Preliminary sketches and materials list
– Progress report
– Design portfolio
– Final prototype
– Class/expo presentations

6. Background research

7. Research the Problem Activity — Patent
Search Worksheet
• Patent Search Worksheet
• Names________________________________
• Date _________________________________
• Work with your partner to conduct research to answer the following questions.
What is the design challenge that you are working on?
• What are some possible products that relate to the design challenge?
• Give at least three examples of existing patents that relate to your design
challenge.
• Suggested websites to use: US patent and Trademark Office:
http://www.uspto.gov
• Google patent search: http://www.google.com/patents
• Patent name:
• Website:
• Brief description:
• How this relates to your design challenge:

8. Research the Problem Activity — Reverse
Engineering Worksheet
• Names_______________________________________
• Date ________________________________________
• Work with your partner to reverse engineer an existing
product. Describe the product that you will reverse engineer.
Where is it typically used? Who might use it?
• What is the function of this product?
• What are the major components of this product?
• List the detailed procedures you used to reverse engineer
this product.
• What are the results and recommendations you have after
reverse engineering this product?

9. Research the Problem Activity — Standards and
Codes Search Worksheet
• Names________________________________
• Date _________________________________
• Standards and Codes Search Worksheet
• Work with your partner to conduct research to answer the following
questions. What is the design challenge that you are working on?
• Suggested websites to use:
• Standards.gov: http://standards.gov/standards_gov/standards.cfm
• US government regulations: http://www.regulations.gov/
• List three possible standards that relate to the design challenge.
(Example: size of fasteners, footprint, etc.)
• List three possible safety issues that relate to the design challenge. What
existing codes relate to those issues?
• List three possible environmental issues that relate to the design
challenge. What existing codes relate to those issues?

10. Research the Problem Activity — User
Interview Worksheet
Question Customer Statement Interpretation
Rank Customer Need
1
Work with your partner to conduct user interviews. This information helps you
determine if your design will meet customer needs and also may help you find hidden
customer needs.
•Gather raw data from your user using video, audio or notes. Here are some possible
questions:
When do you use this product?
Why do you use this product?
What do you like about existing products?
What do you dislike about existing products?
What improvements would you make to the product?
•Fill in the following chart to document user feedback.
•Look at the chart above and look for any repeating comments. Group these comments
together by using a descriptive word (Such as “casing” or “function”). These are
indications of your customer needs.
•Rank the needs in the chart below in order of importance for the user.

11. Prosthetic Arm Challenge Introduction
• A classmate has recently lost part of her arm below
the elbow. She now needs a prosthesis that is low-
cost and easily maintained that will allow her to
complete daily tasks in school and at play.

12. What is a Prosthesis?
• A prosthesis is an artificial limb (an artificial
substitute) that replaces a missing leg or arm
due to disease, accidents, or congenital
defects.
• Main types of artificial limbs:
– Transtibial prosthesis
– Transfemoral prosthesis
– Transradial prosthesis (MESA Prosthetic Arm Challenge)
– Transhumeral prosthesis

13. A U.S. soldier demonstrates
table football with two
transradial prosthetic limbs
i-limb ultra, by Touch
Bionics, has five
individually powered
digits and went on sale in
2007 for $17,454

14. The Jaipur foot, a transtibial
prosthesis, is readily available to
impoverished nations and costs
$35. In contrast, prosthetics in
the U.S. cost from $5,000 to
over $100,000.
 Prostheses in the United States are made
from materials such as plastic, metal
(aluminum, steel, titanium), silicon, latex,
and carbon fiber. These devices can also
have robotics components.

15. Man builds himself bionic hands
• Sun Jifa lost both his hands when a
homemade blast fishing bomb exploded
prematurely. Unable to afford the prosthetic
limbs offered by a hospital, he created his
own.
– Source: http://news.yahoo.com/photos/man-builds-
himself-bionic-hands-
slideshow/#crsl=%252Fphotos%252Fman-builds-himself-
bionic-hands-slideshow%252Fbionic-hands-photo-
1345045308.html

16. “I survived, but I had no
hands,” he explained.
After the accident, Sun Jifa, 51, of Guanmashan,
Jilin province in northern China desperately
needed to work on his family farm, according to
the Daily Mail.

17. Jifa spent eight years
handcrafting prototypes
before finally creating
metal hands that could
grip and hold.
“I couldn’t afford to buy the false hand the hospital wanted
me to have, so I decided to make my own,” Jifa says.

18. The devices depend on
a series of wires and
pulleys inside, and are
controlled by
movements in his
elbows.
“I made this from scrap metal for virtually nothing,” Jifa
says.

19. Jifa says he will further
develop the design for
other disable people.
“There is no need to pay hospitals a fortune,” Jifa says.

20. Prosthetic Arm Challenge Overview
The MESA USA Prosthetic Arm Challenge involves the
development of a low-cost prosthetic device to complete
pre-defined tasks. The challenge has four components:
Performance, Technical Paper, Academic Display and
Oral Presentation.
Objective:
Teams will build a low-cost prosthetic arm for use by a
classmate who recently lost part of her arm below the
elbow. The device should be designed to be low-cost and
easily maintained and allow her to complete daily tasks in
school and at play. The device must meet the criteria
outlined in the rules and be designed to perform the pre-
defined tasks.

21. • Device Performance – 150 points
– Distance Accuracy Relay
– Object Relocation
– Dexterity (high school only)
• Device Efficiency – 50 points
• Technical Paper – 100 points
• Academic Display – 100 points
• Oral Presentation – 100 points

22. Challenge Performance Tasks
1. Distance Accuracy Relay: greatest distance and
accuracy achieved by tossing balls of different
sizes into target containers at different distances
2. Object Relocation Task: greatest mass-to-time
ratio achieved by placing objects of varying
weights into a container
3. Dexterity Task: greatest number of bolts and
nuts correctly placed and secured onto testing
device

23. General Rules
• Device must attach halfway between elbow and wrist, and
extend beyond real hand.
• Device must include hand mechanism (at least 2 fingers) and
must open and close w/o assistance from opposite elbow,
forearm or hand.
– Hand mechanism must open at least 10 cm.
– Objects in each task MUST be grasped, taken hold of, or grabbed on
part of device that extends beyond hand (i.e. the “fingers” of device).
Can NOT use any other part of device or parts of own hand, wrist, or
arm to grasp, take hold of, or grab objects.
• Device, including all parts of all configurations, cannot weigh
more than 3 kg.

24. • All parts and materials of the device cannot exceed $40 pre-tax
price limit
• Must complete and submit provided itemized budget sheet and
attach receipts and/or online retail price print-outs to support
prices listed.
• Device cannot utilize team member’s wrist, hand, or fingers in any
way.
• Team will determine their method of immobilization and must
demonstrate this for judges.
• In addition, a latex glove will be placed over member’s CLOSED FIST
before attaching device.
• Parts may NOT be added, removed, replaced, or readjusted during
trial; between trials is allowed.

25. Distance Accuracy Relay Highlights
• Target containers at three different distances
– Containers are Home Depot’s “Homer’s All-Purpose Buckets
• 2 meters from launch line
• 3.5 meters from launch line
• 5 meters from launch line
• Relay objects are three different size balls
• 5 standard size tennis balls (≈ 2.5 inches)
• 5 vinyl kick balls (2 inches)
• 5 standard size ping pong balls (≈ 1.5 inches)
Diagram 2
 Relay objects
randomly placed in
cardboard box
 Top lid of an Office Depot
Copy Paper 10 reams box

26. • 1 minute to prepare and demonstrate device, and to place
device and box with Relay Objects anywhere on table.
• When given start order, first designated team member enters
Working Area, attaches device, and tosses as many of the
SAME TYPE of balls.
• Teams MUST toss all types of same balls before tossing
subsequent types of same balls.
• At least two team members MUST participate in the relay.
One member must not toss more than two types of balls.

27. • Only ONE of the balls may be grabbed at a time.
• Only balls inside designated box may be used for
tossing.
• Trial will conclude:
– At end of 90 seconds
– When a member grabs more than one ball
– When a member tosses wrong type of ball
– When any part of member’s body including arm and device
crosses launch line when tossing ball
– When target container is knocked over
Score Matrix 2m
Target
3.5m
Target
5m Target
Tennis Ball 10 15 25
Kick Ball 15 20 30
Ping Pong Ball 25 30 40

28. Object Relocation Task Highlights
• Objects
1. Two – 20 ounce Dasani bottles of water
2. Two – 1 liter Dasani bottles of water
3. Two – 1 lb boxes of Crayola Modeling Clay
4. Two – Master Lock 1500D 1 ⅞” Combination Locks
5. Two – Quart size Ziploc bags with 200 Pennies
6. Two – Spindle of 30 CD’s
7. Two – 2 inch by 20 yard Rolls of Duct Tape
8. Two – 4 oz. bottles of Elmer’s Glue All (white school glue)
9. Two – Packages of 12 AA Energizer Batteries
10. Two – Composition Notebooks, 100 pages, page size 7.5” L x 9.5” W
11. Two – 1 lb Box of Grip-Rite Nails any size, box dimensions approximately 2” H x 4.75” W x 3.5” L
12. Two – Packs of 100 3” x 5” Index Cards
13. Two – Spiral Bound 3 Subject Notebooks, 120 pages, size 10.5” L x 8” W
14. Two – Rolls of 1” x 60 yards masking tape
15. Two – 1 pound bags of pony beads (approximately 2000 beads)
• 10 of the 15 item groups will be selected on day of
competition

29.  1 minute to prepare, attach, and
demonstrate device, and to place
container in one “Container
Area”.
76
cm
50 cm50 cm
Diagram 3
83 cm
 At end of 1 minute or when device is prepared, attached and
ready, designated team member will stand outside of Working
Area.
 1 ½ minutes (90 seconds) to complete task.
 At least 5 different item types MUST be place in container or trial
will be declared a mistrial.
 Team may call end of trial before 1 ½ minutes have passed by
calling out “done”.
 Any item held by device when time is called will not be counted
towards total mass of container.

30. Dexterity Task Highlights
• For high school teams ONLY
• Testing device made from two
1 foot x 6 inch x 1 inch boards
attached perpendicular to
each other.
1’ Length
6” Height
A B C
3”
FRONT VIEW
Diagram 6
 Vertical board with three pre-drilled holes
 3 inches from edge and 3 inches from top
 Hole “A” = 6.9mm Metric Drill (US-17/64)
 Hole “B” = 10.0mm Metric Drill (US-27/64)
 Hole “C” = 14.2mm Metric Drill (US-35/64)
 Dexterity Materials include:
 Hole “A” = 8mm x 1.25mm hex bolt and nut, and 13 mm wrench
 Hole “B” = 12mm x 1.5mm hex bolt and nut, and 19mm wrench
 Hole “C” = 16mm x 2.0mm hex bolt and nut, and 24mm wrench

32. • 1 minute to prepare, attach, and demonstrate device, and to
prepare “Testing Area” and dexterity materials.
– Testing Device can be placed in either Testing Area (50 cm square).
– Dexterity materials placed outside of Testing Area.
• At end of 1 minute or when device is prepared, attached and
ready, designated team member will stand outside of Working
Area.
• 2 minutes to complete task.
• Member may sit or stand and may move chair and/or stand
anywhere in Working Area.

33. • Task is as follows:
– Grab and place hex bolt into corresponding pre-drilled holes.
• May hold head of hex bolt with non-prosthetic hand ONLY. May NOT twist or screw
in any way or trial will stop and be declared a mistrial.
– Grab corresponding hex nut and place onto bolt.
– Grab corresponding wrench and screw hex nut onto bolt.
– Repeat for all three hex bolt and nut sets.
• May choose in what order each bolt/nut set is secured but
must place a nut on a bolt before attempting another. Once
all three nuts have been placed on bolts, may re-visit any
bolt/nut set to score more points.
• Each hex bolt will have a marking every 0.5 cm from base of
bolt head.

34. Reminders
• Safety first: Since transradial prosthesis will
be attached to student’s arm, please keep
safety in mind at all times.
• Stay within all the parameters of the project.
• Research, brainstorm, build, test, record,
revise, build, test, record, revise, build, test,…
– Use the Engineering Design Process
• READ ALL THE RULES!!!

35. Activity 1 – Relocating Objects
• Objective
– Design, build and operate a transradial prosthesis from given
supplies to grab various size objects one a time and release
them into a container
• Supplies per group
– 2 sheets of card stock paper
– 5 feet of string
– 9 straws
– 14 craft sticks
– 3 beads
– Activity Sheet

36. Activity 1 Instructions
• Using the given supplies, design and build a transradial prosthesis. The prosthetic arm should
be attached half way between the elbow and wrist and should extend beyond the real hand.
– Device MUST have hand mechanism and MUST open and close.
– Can NOT use opposite elbow, forearm or hand OR real hand to operate or control the
prosthetic arm.
Creating One Finger with Two Joints
• Cut one craft stick into three equal pieces.
• Cut two pieces of straw slightly shorter than the pieces of sticks.
• Glue one piece of straw to one piece of stick. Put the glue on the stick and not the straw or
the straw may melt. Do this for a total of TWO straw/stick segments.
• Glue the two stick segments onto a full straw. The sticks should be sandwiched between the
straws now. Leave a small space in between each segment, so that bending is possible at the
joint.
• Glue full straw’s excess onto a full length craft stick. Leave a small space between the full
length craft stick and the first segment, so that bending is possible at the joint.

37. Activity 1 Instructions continued
• Glue one more straw segment onto the top of the full length craft stick in line with the other
two segments.
• Tie a bead onto the end of piece of string. Use the bamboo skewer to thread the other end
of the string through the first short straw segment and through the two other short straw
segments.
• Wrap each segment with tape to reinforce the glue. Pre-bend the finger at each joint.
Creating Arm and Operation
• Using the remaining supplies, create two more fingers, the arm and the operation of the
fingers.
Testing
• Attach the transradial prosthesis and pick up the different objects from a table one at a time
and release them into the container/box.

38. Activity 2 – Tossing Balls into Targets
• Objective
– Design, build and operate a transradial prosthesis from any of
given supplies to toss various balls one a time into cups at
different distances.
• Supplies per group
o 5 – sheets of 9” x 12”
construction paper
o 3 feet of masking tape
o 5 index cards
o 1 pair of scissors
o 2 plastic spoons
o 3 feet of string
o 5 straws
o 10 craft sticks
o 5 – 3 ½” rubber bands
o 10 small paper clips
o 10 large paper clips
o 10 fasteners
o Activity Sheet

39. Activity 2 Instructions
1. Using any of the given supplies, design and build a
transradial prosthesis. The prosthetic arm should be
attached half way between the elbow and wrist and
should extend beyond the real hand.
 Device MUST have hand mechanism and MUST open and close.
 Can NOT use opposite elbow, forearm or hand OR real hand to operate
or control prosthetic arm.
2. Place cups 1 foot, 2 feet, and 3 feet from launch line. No
part of team member or device may cross launch line.
3. Arrange different balls from smallest to largest.
4. Attach transradial prosthesis and grab and toss one ball
at a time; toss same type of ball before tossing
subsequent type of same ball.

44. Designs and constructs a
simple, autonomous robot
• Motors
• Sensors
• Computer controller

45. Mobile Robots
Why do robots need to move?

46. What defines a robot?
• Sense – a robot has to take in information
about its environment
• Plan – a robot has to use that information to
make a decision
• Act – a robot needs moving parts
to carry out commands

47. What ways do robots move?
• Rotate
• Convey
• Walk
• Swim
• Fly
• Reach
• Bend
• Poke
• Roll
Snake Robot

48. Manipulative Movement
• Robots that use an arm, belt
or other means to grab and
maneuver objects

49. Mobile Movement
• Robots that can move
from place to place

50. Why go from place to place?
• Transport goods and materials
• Carry messages
• Get there faster
• Do a task while you’re getting there
or when you get there
• Collect information about what’s there
• Get away from something
• See if you can!

51. Most robots get
around by rolling
• Walking is hard –
it requires balancing
• Swimming only works in
water
• Flying requires a lot
of speed and energy
• Wheels and treads make
moving over ground
easier
• They provide stability
with multiple points that
touch the ground

52. How do rolling robots work?
• Sensors
• Motors
• Wheels
• Programming!

53. Main Components of Robotics
• Build – Mechanics, Mathematics, Physics
• Program – Building behaviors
• Test – Multiple trials
• Communicate – What did you work on
or accomplish? What conclusions did you
come to?

54. Run your program. What
happens? Did your robot perform
as you expect? If not, adjust your
robot or your program and try
again!
Program your robot using
the LEGO MINDSTORMS
Education NXT Software.
Download your program to
the NXT brick with the
wireless Bluetooth
connection or the USB cable.
Build your robot.

55. Overview
NXT Brick
An intelligent, computer-
controlled LEGO® brick, the NXT
is the brain of the LEGO
MINDSTORMS® Education
robot.
Touch Sensors
Enable the robot to
respond to
obstacles in the
environment.
Sound Sensor
Enables the robot to
respond to
sound levels.
Light Sensor
Enables the robot to
respond to variations in
Ultrasonic
Sensor
Enables the robot to
measure distance to an
object and to
respond to movement.

56. Lamps & Converter Cables
Add lamps and then program flashing
lights, or use them to activate the Light
Sensor,. Three Lamps
and three Converter cables are
included in the Base Set.
Interactive
Servo Motors
Ensure that robots
move smoothly and
precisely
Rechargeable
battery
Provides power to the
NXT so the robot can
move
and respond.

57. Building
• Gears and axles
• Beams and connectors
• Motors and wheels
• Sensors and wires
• NXT programmable brick
We will be using LEGO® pieces
to build our robots

58. Building
LEGO® Pieces

59. Building LEGO® Motors and Sensors
Motors
Sound
Sensor
Touch
Sensor
Light
Sensor
Ultrasonic
Sensor

60. Building LEGO® NXT
Sensor
Input
Ports
Motor
Output
Ports
Navigation
Buttons
LCD
Display
Screen
USB connection socket

61. Connections
Connecting Motors
To connect a Motor to the NXT,
plug one end of a black wire
to the Motor. Plug the other end
into one of the output ports
(A, B, C).
Connecting sensors
To connect a Sensor to the NXT, plug
one end of a black wire
into the Sensor. Plug the other end into
one of the input ports
(1, 2, 3, 4).

62. Downloading and uploading
The USB port and wireless Bluetooth
connection are used for downloading
and uploading data between your computer
and the NXT.
If your computer has Bluetooth, you can
download programs to the NXT
without using the USB cable.
If your computer does not have Bluetooth, you
must use the USB cable

63. Programming Behaviors
• Giving the robot behaviors
• Complex behaviors are built from simple ones
The basic behavior… is used in the simple behavior:

64. Programming
…which is used in the complex behavior:

65. Programming Screen Interface
Programming Area
Properties Area
Blocks

66. Programming Blocks and Functions
Program by dragging blocks
from the menu
on the left
Place them on the grid,
and wire them together
Can create your own
blocks called My Blocks

67. Touch Sensor
• The Touch Sensor is a switch: it
can be pressed or released.
• You can add the Touch Sensor
to an NXT model and then
program the model behavior to
change when the Touch Sensor
is pressed or released.

68. Sound Sensor
• The Sound Sensor detects
the decibel level: the
softness or loudness of a
sound. The Sound Sensor
detects both dB and dBA.
• dBA: the sounds human
ears are able to hear.
• dB: all actual sound,
including sounds too high or
low for the human ear to
hear.

69. • The Sound Sensor can measure sound pressure levels up to 90 dB
– about the level of a lawnmower.
• Sound sensor readings on the LEGO® MINDSTORMS® NXT
are displayed in the percentage [%] of sound the sensor is
capable of reading.
• For comparison, 4-5% is like a silent living room and 5-10% is
about the level of someone talking some distance away.
• From 10-30% is normal conversation close to the sensor or music
played at a normal level and 30-100% represents a range from
people shouting to music playing at high volumes.
• These ranges are assuming a distance of about 1 meter between
the sound source and the Sound Sensor.

70. Light Sensor
• The Light Sensor enables the robot to
distinguish between light and darkness, to
read the light intensity in a room, and to
measure the light intensity on colored
surfaces.

71. Ultrasonic Sensor
• The Ultrasonic Sensor enables the robot to see and recognize
objects, avoid obstacles, measure distances, and detect
movement.
• The Ultrasonic Sensor uses the same scientific principle as
bats: it measures distance by calculating the time it takes for a
sound wave to hit an object and come back – just like an echo.
• The Ultrasonic Sensor measures distance in centimetres and
inches. It is able to measure distances from 0 to 2.5 meters
with a precision of +/-3 cm.
• Large-sized objects with hard surfaces provide the best
readings. Objects made from soft fabrics, from curved objects
(e.g. a ball), or from very thin and small objects can be
difficult for the sensor to read.

72. • Two Ultrasonic
Sensors in the
same room may
interfere with
each other’s
readings.

74. Testing Why do we test?
• Make sure it works!
• Understand what it can do
• Test everything multiple times to determine
the repeatability
• Use the robot to test other phenomena

75. Testing
• When we test, we take data (numbers)
• We write our numbers down in organized
charts
• We write down everything we can about the
experiment
• Look at our data after we’re finished

76. Communicate
Why is communicating your design so important?
• If no one knows what it is, how it works, or
why it’s cool, why would they want to buy it?
• When it is well-documented, other people can build
on what you have started and create even cooler
technologies!

77. Communicate
• Experiment worksheets and log books
• Presenting our work
• Sketching and describing ideas so
teammates can understand too

78. Fork Lift

79. • This Forklift can drive around and steer on carpet or hard
floors, lift loads that are placed in the pallet bucket 7 inches
straight up, set them gently down on top of shelves or other
platforms, and take them back down.
• Color sensor is used as a "warning" light to signal different
operations.
• One can program the Forklift to do automatic tasks using the
rotations sensors in the motors and the Ultrasonic sensor on
top, or if you have a working Bluetooth connection between
computer and NXT, then you can drive it by wireless remote
control from your computer keyboard
• Or, if you have two NXTs, you can control it by Bluetooth
with the Dial Remote Control project.

80. Race Car

81. • This Race Car is designed to look and steer like a real car, with pivoting
front wheel steering.
• It is also designed for speed, with gears to increase the speed of the rear
drive wheels.
• The Color Sensor is positioned under the car so that the car do some
basic autonomous operations by sensing the color of the surface.
• The sensor can distinguish six different colors, so you can make the car
react to different colored tape lines, colored paper strips, etc.
• One can also operate the car by remote control with either a simple two
button wired remote control (requires only one NXT kit), or by wireless
Bluetooth remote control from another NXT such as the 5 Button
Remote Control or the Steering Remote Control.
• Programs are provided for all three of these remote controls.

82. What is Engineering?
• Problem solving
• Teamwork
• Time management
• Testing
• Doing it over if it doesn’t work
correctly the first time!

83. Engineering Process
Determine
the problem
What are you trying to
solve? Why do you
need it?
Research
Has anyone ever solved
this problem before?
How did they do it?
Brainstorm
Come up with as many
solutions to the problem
as you can.
Pick the
best solution
Figure out the best
solution to solve the
problem and meet
budget and time
constraints.
Build
Physically constructing
something can be
difficult. Don’t get
discouraged!
Test
Does what you built solve the
original problem? Why or why
not?Redesign
How can you change it to
meet the problem
requirements?
How did you attack the
problem? What challenges
did you encounter? What was
your final solution? What
changes would you make?
Present

84. Personal Assistant Robot

85. Personal Assistant Robot
• We will be making a mobile robot to help
out in the classroom
• We will run tests on the robot to determine
its capabilities
• Before it can do complicated behaviors,
we have to teach it simple ones
• But before we program anything, we need
to build

86. Chapter V
Shot Peening

87. History of Shot Peening
 Discovered centuries ago by sword smith’s & black smith’s.
 They found that peening the surface of sword or wagon
spring greatly increases its resistance to breaking.
 Round knob of the “ball peen” hammer was the smith’s
tool for cold working/peening.

88. What is Shot Peening
 Shot peening is a cold work process.
 Used to finish machine components to improve fatigue and stress
corrosion failures.
 Small spherical shots bombards the surface.
 Dimpling the surface and develops compressive stress.
 Shot peening can be done without changing part design.
• Media used for the shot peening include: steel, ceramics and glass.

89. Shot Peening Mechanism
 When a round part (steel ball ) strikes a part of surface at high
velocity the contact area is a point.
 This concentrates the impact energy in a very small area.
 causing a radial plastic flow at the impact point.
 This plastic flow or movement of metal leaves compressive
stresses in the part.
 Complete coverage of the with overhauling ball impacts leaves a
thin permanent compressive stress layer in the part surface.

90. Why Residual Stress?
 Metals fail under tension & not under compressive loads.
 The failure crack usually initiate at the part surface where
tension stresses are highest and a stress raiser exists.
 when part is shot peened, the failure producing tensile
stresses are thus reduced by the amount of compressive
stresses (residual).
 The lowering of the effective tensile strain will then allow
the part to accept higher loading.

92. Typical Shot Peening Curves
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93. Shot Peening
(a) Mechanism for formation of residual compressive stresses in surface by cold plastic
deformation (shot peening). (b) Hardness increased in surface due to shot peening.

94. Applications of Shot Peening
 Gear Parts
 Cams and Camshafts
 Clutch Springs
 Connecting Rods
 Crankshafts
 Gearwheels
 Leaf and Suspension Springs
 Rock Drills
 Turbine Blades

95. Shot Peening vs Shot Blasting
 Shot Peening (S.P.): Shot peening is a cold working process, which
uses the mass and velocity of a shot stream to produce residual
compressive stress at the surface of the part. precisely controlled
process relying on careful selection and control of media, intensity,
coverage and equipment.
 Shot Blasting (S.B.): Shot blasting or blast cleaning is a process in
which an abrasive material is accelerated through a pressurized nozzle
or centrifugal wheel and directed at the surface of a part to clean or
otherwise prepare the part surface for further treatment.

96. Media Used in S.P. & S.B.
 Shot Blasting: Blasting media includes sand; steel shot,
cut wire shot, garnet,
a sharp hard abrasive glass beads .
 Shot Peening: Peening media must remain
predominately round and uniform in diameter to avoid
surface damage upon impact and to maintain a uniform
compressive stress layer.

97. Applications S.P. & S.B.
 Shot Blasting: Shot blasting can be used on castings,
forgings, and stampings to produce a uniform surface
texture and for descaling, deburring, and deflashing.
Shot blasting is used in a wide variety of industries
including automotive, marine, mining, and
medical applications.
 Shot Peening: connecting rods, crankshafts, compression
springs, torsion and anti-sway bars and metal implants.

98. Aircraft As a Machine

99. Human Fascination with Flight
 Passion to fly originated as early as prehistoric times.
 The freedom to fly in any direction at certain determined
height and speed is a capability that all of us view with
envy.
 Birds can fly by a variety of ways:
i. Gliding ii. Flapping Wings iii. Hovering

100. V-Formation Flight of Birds
 Large birds are often observed flying in V format.
 V-formation allows them to conserve energy.
 reduces air resistance.
 Better vision and communication in flight.
 In aircraft, V-type formation helps in avoiding heavy wing tip
vortices.

101. Main Aeronautical Clusters
 Aerodynamics and airframe.
 Propulsion and power plant.
 Materials and structures.
 Dynamics, stability and control.
 Avionics, power and flight computers.
 Maintenance, repair and overhaul.

102. Forces Acting on a Airplane
 The four forces are Thrust, drag, lift, weight.
 The four forces can be drawn oriented through the C.G.
 weight = Lift & Thrust = Drag in a level flight
LIFT
THRUST
WEIGHT
DRAG

103. Forces on A/C During Climb/Descent
 Forces remain same, lift, weight, thrust, drag.
 In a climb, A/C is still flying in a straight line with constant
velocity.
 LIFT ≠ WEIGHT & THRUST ≠ DRAG
 THRUST > DRAG
 Angle of climb is determined by excess of thrust over drag.
DRAG
WEIGHT
LIFT
THRUST

108. Directional Control and Stability

109. Aircraft Stability
 Positive stability : tends to return to original condition after a
disturbance.
 Negative stability : tends to increase the disturbance.
 Neutral stability : remains at the new condition.
 Static stability : refers to the aircraft's initial response to a
disturbance.
 Dynamic stability : refers to the aircraft response over time to a
disturbance.

110. Roll Control: Aileron

111. Pitch Control : Elevators
 Pitch stability, A/Care
designed to be nose
heavy.
 C.G. is ahead of
aerodynamics center.
 This design feature is
incorporated so that in
the event of engine
failure, A/C will assume a
normal glide.

112. Yaw Control : Rudder

113. Roll, Pitch and Yaw Control