MAE3 Robot Presentation

Team Trebuchet

Steve Wilson

Stewart Kerr

Phillip Hodgson

Chen-Hsien Chan

0 to 6 pts in 0.8 seconds

One long arm can reach a large amount of the contest table.

Goal: Grab the center bonus balls before anyone else

Giant Arm -> Giant Rubber Bands

A large moment is needed to deploy the large arm quickly

Side image of folded arm, showing rubber bands

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Grabbing the Balls

Force created by swinging arm extends all sections of the arm

Defending Our Balls

Release Mechanism

Secondary Arm Analysis

Problem: how fast does the primary arm need to accelerate to cause the secondary arm section to swing out?

Secondary Arm Mathematical Model

Simplifies to - (θ’’)L = ( X’’ ) cos(θ) + ( Y’’ + g) sin(θ)

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Assumptions:

• no friction
• all arm mass is at the center of gravity
• the arm it is attached to has a uniform angular acceleration for the first 90 degrees it spins

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T

mg

FBD:

acceleration of mass =

[X’’ - L * sin(θ) (θ’)² + L * cos(θ) * θ’’,

Y’’ - L * cos(θ) (θ’)² + L * sin(θ) * θ’’]

X’’

Y’’

θ

θ

Comparison to Actual Results

• Primary Arm takes 0.26 seconds to rotate 90 degrees
• Average angular acceleration: 46.4 rad/s^2
• Twice as fast as it needs to just barely flip arm over

Minimum

Actual

Design Process

• Prioritized speed and simplicity
• speed takes other robot out of equation
• simplicity means getting more out of less
• Avoided parts that needed to be driven with skill
• driver controls aren’t precise
• driver is inconsistent

The Final Product

• Scores 6 points in 0.8 seconds
• Prevents opponent from getting bonus balls or going to our side of field
• All with only 1 motor

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Video: