Old gate. Motor moves back and forth, causing the lego pieces to move up and down.

New gate. Motor continuously turns, and the grey axle piece moves up and down, acting as the stopper.

MichelangeloJamie Chang, Mason Hargrave, Laura Mudge, Smiti Narayanan

https://sites.google.com/a/eng.ucsd.edu/2014-team-1/

Resources and AcknowledgmentsThanks to: Dr. Nathan Delson, Prof. Raymond de Callafon, Bryn Bishop, Ngoc (Naomi) Diep, Sze W (Edwin) Wong.

Team 6 (Cosmos 2014 Cluster 2) for the light sensor mount designDr. Nathan Delson for the four bar linkage design, used in the gates

David

OverviewThe goal of this sculpture is to sort black and yellow

balls into two separate baskets, with a secondary goal of demonstrating fundamental physics concepts and maintaining visual appeal throughout the process. This concept has gone through a plethora of redesigns in order to better showcase the capabilities of the sensors, motors, and track pieces provided. The final result utilizes parts from Lego Mindstorm kits, Chaos Balls kits, and some custom designed acrylic pieces to accomplish the aforementioned goal.

Mini-SculptureThe mini sculpture is a ball sorter operated by two

servo powered gates and a light sensor. Depending on the ball’s color, the gates open in a specific order. For a black ball, both gates open at the same time, allowing the ball to travel the full length of the track and fall into the second basket. For a yellow ball, the first gate opens, and the second gate stops the ball at a lower height before allowing the ball through. This decreases the kinetic energy of the ball back to zero before allowing gravity to provide energy to drop the ball into the second basket.

The human interface is a button that causes both gates to open, allowing all balls to fall into the second basket, regardless of color.

Physical Simulation with Working ModelWe used Working Model 2D to simulate the components

of our sculpture.

Overview of Complete SculptureIn our final sculpture, the NXT plays music if the light

sensor detects a ball going by. The sculpture also includes a loop, a trampoline, and a basket that flips to transport balls over a break in the track.

Sculpture Physics & AnalysisTo building the ball sorter, we placed two basket 11.5 cm

and 25.5 cm from the end of the track, and 18 cm below the track. We then calculated the necessary drop heights for each basket. To do this, we used the equation

Δy = Vot + ½ gt 2

to find that if the baskets were 18 cm below the track, the balls would have 0.1917 s to fall to the basket. We then used the same equation to find the launch velocities necessary to reach each basket in that time, and then used the equation

V = √10/7 gh to find the drop heights for each basket.

Controller Programming: Ball Sorter

Design Challenges: GatesThe original concept for the gates was to attach lego pieces

to a motor. The lego pieces would be perpendicular to the track, and the motor would rotate the gate up to allow balls through. However, the force of the impact with the gate was such that the ball would at times fall off the track. We decided to use a four bar linkage instead, with a somewhat flexible perpendicular stick piece, which would stop the ball with a little bit of “give,” softening the impulse of the impact.

Design Challenges: StructureThe original structure we built to house the ball catcher

was unstable (shown under the “Mini-sculpture” section). We used a mixture of short and long shafts as well as various connector pieces, which caused the structure to bend and twist, producing inconsistent results. We solved this problem by building the base with long shafts, only using short shafts as supports. The newer structure (shown under the “Overview of Complete Sculpture” section) allowed for more stability even as we added new components for the final sculpture.

Working Model vs. Mini-Sculpture

ConclusionFor further analysis of this sculpture, we could

measure the balls’ energy loss on the trampoline or along the track. We could do this by finding the differences between the calculated and measured speeds at a certain point on a slope.

What we learned from this assignment: - Ball/energy physics - How to use working model to simulate real-life physics - Programming with RobotC - Presentation skills - Teamwork in problem solving - Risk analysis in engineering design

The ball sorter: For black balls, gates 1 and 2 open at the same time. For yellow balls, gate 1 opens before gate 2 does, allowing the ball to stop at gate 2 before continuing on.

Gate and light sensor.

Gates. We ended up removing one of these.

Baskets. We only used two in the end.

Lift

Gate

Gate with light sensor

Baskets

Lift

Above: Old mini-sculpture design, with three gates and three baskets. The final sculpture only used two gates and two baskets.

Below: AutoCAD drawing of the final mini-sculpture.

Poll button sensor

pressed?

open gates 1 & 2

wait 1 sec

close gates 1 & 2

reading? black

yellow

Poll light sensor

yes

no

nothing

open gate 1

wait 1 sec

open gate 2 wait 1 sec close gates 1 & 2

This code determines the order in which the gates open, and incorporate the human interface.

move basket motor -180o

4 bar linkage mechanism, used as gates. An axle piece is used as the stopper on the actual gate. The motor’s movement timing is programmed as needed.

The first working model simulation accurately depicts how the four-bar linkage works to convert rotational motion to one-dimensional motion. The second simulation accurately shows the 2D path of the ball as it is launched off the track.

Motor

Controller Programming: Speed Randomizer, Speed sensor, Container flip

ball passed?

yes

Initiate light sensor

no

play music

wait 1 sec

move basket motor 180o

wait 1 sec

This code plays musicif a ball passes the light sensor, and gets the ball over a break in the track using a basket.

Stopper

First basket Second basketDistance from track 11.5 cm 25.5 cmVelocity at launch 0.6 m/s 1.33 m/s

Drop height .0257 m 0.1262 m

For our actual track, we needed to account for friction and small errors, so we rounded up the drop heights to 5 and 18 cm.

Gate

Baskets

Gate with light sensor

Trampoline

Lift

Funnel