Download File - Joshua Harling

Robotic Skateboard
Rachel Dittemore, Joshua Harling, Jonathan Ladner, Ryan Meeks, David Quintanilla
Department of Mechanical and Aerospace Engineering at the University of California, San Diego
Sponsored by the UCSD MAE Department, Spawar, and BAE Systems
Project Managed by Dr. Raymond de Callafon
Overview
Physics is often viewed as a boring and difficult
subject, and because of this, many high school
students show little interest in it. However, physics is
fundamental to all engineering, and engineering is
incredibly important for developing technology in
today’s world. Teachers have looked for countless
ways to make physics more appealing to students
with little success, but this can be changed by
incorporating the popular sport of skateboarding.
The UCSD Robotic Skateboard project was created
to infuse fundamental principles in physics with
skateboarding by designing and fabricating a selfjumping robotic skateboard.
The first phase of activation consists of the
transfer of energy between the loaded springs and
the sliding mass referred to as mass 1, m1.
Fig. 2: Conservation of Energy in the First Phase
The conservation of energy can be viewed in
between two states. State 1 has all of the potential
energy because the springs are fully compressed and
mass 1 is at rest. State 2 consists of all of the energy
being converted into kinetic energy, as mass 1 is now
traveling at a velocity U, and the springs are now at
their equilibrium points.
The second phase is the collision of mass 1 and
the skateboard contraption, referred to as mass 2,
m2.
Figure 5: Bunny Hop Prototype
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Fig. 3: Conservation of Momentum in Second Phase
The final velocity of the system is dependent
on mass 1, mass 2, and velocity, U, from phase 1.
The third and final phase of jump is the point at
which the wheels of the skateboard are no longer
touching the ground and the whole contraption, that
is mass 1 and mass 2, are moving together with a
final velocity, V. The system can now be modeled as
a single particle following a projectile motion.
Fig. 8: Mini Bunny Hop
Impact on Society
Fig. 4: Single Point Model Projectile Motion in phase 3
How It Works:
The jump will occur due to the collision of a
sliding mass and a contraption rigidly constrained to
the skateboard. The sliding mass will gain its
velocity from the release of the potential energy of
the compressed springs. The collision will transfer
momentum from the sliding mass to the skateboard,
which is at rest, and will propel the skateboard
upward, causing the entire system to jump. The
jump can be broken down into the physics behind
three phases.
• 12 x 4 inch2 Delrin deck with maximum height of
9 inches
• All components and body made out of Delrin
• Single tower shaft as guide rail
• Two 20 lb/in compression springs in series for a
10 lb/in equivalent and 40 pounds maximum load
• Small load and safe use for students
• Mechanical latch and release, string pulled
The mini bunny hop skateboard is a safe, easy
to use model of the full scale bunny hop. The latch
hooks are moved to the side, allowing room for the
mass to be compressed down, and then the hooks are
moved back to latch onto the mass. The latch is
released by the pull of the string that pulls both
hooks off.
Four threaded rods for strength and adjustability
Two Steel poles as guide rails
One 42 lb/in spring on each pole, 84 lb/in total
Total compression of 6 inches in springs
PVC piping used as linear sliders
Hairpin latching mechanism
Steel plates used for weight within mass 1
Fig. 6: Bunny Hop Skateboard
Fig. 1: Deliverables: Bunny Hop Skateboard, Mini Hop
Skateboard, and Ramp. Team (starting at left): Josh,
Rachel, David, Ryan, Jonny
Mini Bunny Hop Skateboard
Final Bunny Hop Design
Project Requirements and Deliverables
• A full scale robotic skateboard that is able to jump
a minimum of 12 inches
• A mini robotic skateboard that is safe for student
operation and is simple enough to be reproduced
• A ramp that will be used to give the robotic
skateboard an initial velocity
• Incorporate physics principles into designs
• Demonstration of robotic skateboards at the San
Diego Science Festival on March 18, 2013
The prototype was a successful design and
matched the model equations very well. With a
projected 5.1 inch jump and an actual jump of 4.9
inches, this 4% error is understandable due to the
unaccounted friction within the system.
The initial velocity given in the x-direction will
be provided by the skateboard starting its run at the
top of the ramp. The final equation of the height
achieved in the jump is dependent on four
parameters: mass 1, mass 2, spring constant k, and
the compression of the springs x.
Prototype
The prototype consists of a center shaft made
from a copper pipe which holds an aluminum slider
with two brass weights attached. When pushed
down, two 34 lbs/in springs in series resist the slider,
causing the mass to crash back up into an aluminum
stopper. When the stopper is hit, the rigidly attached
base underneath jumps off of the ground.
The main goal of this project is to encourage
young students to become interested in science and
engineering. This project ties the popular activity of
skateboarding and science together by experimenting
with springs and their ability to create large amounts
of energy. Through demonstration and interaction at
the San Diego Science Festival, students are able see
how exciting science can be.
Latching Mechanism
This mechanism takes advantage of an over-deadcenter crank which, when loaded requires only six
pounds of force to release a 500 pound load. When the
latch is locked, as shown in the figure below on the left,
the load travels up the center and a solenoid prevents it
from unloading. When the solenoid is actuated the latch
can freely and safely unload the mass-spring carriage.
Fig. 7: Latch Mechanism
BEFORE RELEASE AFTER RELEASE
Acknowledgements
We would like to thank the following people,
without whom this project would not have been
possible or successful:
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Dr. Raymond de Callafon
Dr. Nathan Delson
Paul Schmitt
Pedro Navarro
Tom Chalfant, Isaiah Freerksen, and Mark
Steinborne
• Alejandro Valencia