The document proposes building a robotic arm that mimics human motion and is controlled by human movement. It describes the initial design of the arm in Autodesk Inventor with an elbow joint. Diagrams show how gear ratios and motors will allow the forearm to move up and down. The document also discusses a prototype ball and socket joint, omni-wheels, and potential applications for robotics.

1. Serif Mark II Proposal
Paso Robles High School Engineering Department

2. We Have an Idea
Build an arm that:
● mimics human motion
● is controlled by
human motion
● is programmable

3. Welcome to the Drawing
Board
● Designed in Autodesk
Inventor
● Functioning elbow joint
● Improvements easily
applied

4. Forearm

5. Upper-Arm

6. ● Motor rotates
● Rotates gear fixed on axel
● Moves forearm up/down
Designing the Elbow

7. We (Could) Have the
Power

8. Building Something New
● Prototype for ball and
socket joint
● Omni-Wheels
● Can be robotic

9. Intro
Gear ratios use different sizes and
types of gears to change the speed and
torque.

10. Speed
With the same input speed
● Gears with more teeth (bigger) rotates proportionally slower because it takes more
teeth/rotation
● Gears with less teeth (smaller)rotates proportionally faster because it takes less
teeth/rotation
Therefore
● Speed in*Teeth in=Speed out*Teeth out or
● Speed in*(Teeth in/Teeth out)=Speed out or
● Speed in/(Teeth out/Teeth in)=Speed out or
● Speed in/Gear reduction=Speed out
(“Teeth out/Teeth in” is gear reduction)

11. Torque
Torque=Force*Distance so Torque in=Force in*Distance in or
Force in=Torque
in/Distance in
Force in is exerted on the gear out teeth so
Torque out=Force in*Distance out or
Torque out=(Torque in/Distance in)*Distance out or
Torque out =Torque in*(Distance out/Distance in) or
Torque out =Torque in*(Teeth out/Teeth in) or
Torque out =Torque in*Gear reduction
(distance is radius)
(radius is proportional to teeth)

12. Torque Pics

13. More

14. What is a motor?
A machine, especially one powered by electricity or internal combustion, that
supplies motive power to a vehicle or a device with moving parts.

15. How do electric motors work?

16. Motor Strength
● Motor strength comes from the motor’s rotation speed and
torque
● Depending on operating voltage, the stall torque can either be
25.5 kg x cm or 31.6kg x cm
● What this shows is how much weight a motor can hold when
it isn’t rotating

17. Our Motors
● The motor we selected has the strongest stall
torque within our budget.
● The resolution will help the arm mimic actions
precisely
● The motors will be light enough to attach to
the arm without weighing it down

18. Introducing the Omni Wheel
● Rotate like normal wheels
● Smaller wheels roll
perpendicular to rotational
axis
● Two degrees of freedom

19. It’s Alive!
This is the prototype
of a ball and socket
joint

20. The Advantages
● More degrees of freedom with less joints
● Can rotate a ball
● Robotic

21. Cy’s Creative Corner
Imagine if our
elbows were ball
and socket joints
similar to a
shoulder...

22. Real World Applications
Manufacturing would be more efficient if they had less moving joints.