Serif Mark II ProposalPaso Robles High School Engineering Department

We Have an Idea

Build an arm that:

● mimics human motion

● is controlled by human motion

● is programmable

Welcome to the Drawing Board

● Designed in Autodesk Inventor

● Functioning elbow joint

● Improvements easily applied

Forearm

Upper-Arm

● Motor rotates

● Rotates gear fixed on axel

● Moves forearm up/down

Designing the Elbow

We (Could) Have the Power

Building Something New

● Prototype for ball and socket joint

● Omni-Wheels

● Can be robotic

Intro

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

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)

Torque

Torque=Force*Distance so Torque in=Force in*Distance in orForce in=Torque

in/Distance inForce in is exerted on the gear out teeth soTorque out=Force in*Distance out orTorque out=(Torque in/Distance in)*Distance out orTorque out =Torque in*(Distance out/Distance in) orTorque out =Torque in*(Teeth out/Teeth in) orTorque out =Torque in*Gear reduction

(distance is radius)(radius is proportional to teeth)

Torque Pics

More

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.

How do electric motors work?

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

Our Motors

● The motor we selected has the strongest stalltorque 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

Introducing the Omni Wheel

● Rotate like normal wheels● Smaller wheels roll

perpendicular to rotational axis

● Two degrees of freedom

It’s Alive!

This is the prototype of a ball and socket joint

The Advantages

● More degrees of freedom with less joints

● Can rotate a ball

● Robotic

Cy’s Creative Corner

Imagine if our elbows were ball and socket joints similar to a shoulder...

Real World Applications

Manufacturing would be more efficient if they had less moving joints.