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Robotic Design Studio is a chance to build with
LEGO Technic, and program with Handy and Blue Dot Cricket LOGO.
The goal of this course is to put together a robot or robots
that can perform specific functions. Each group is free to
design any type of project that interests them. Our goal was to
design and build a project that has small components which are
easy to modify and manipulate. At the same time we wanted to
incorporate music, since the MIDI music programming appeals to
members of our group. From there we developed our Dancing
Crickets.
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We want to simulate a ballroom where there are
three couples dancing to music. Each couple, or pair of
dancers, dances to a different song that is played by the DJ.
We wrote a Strauss Waltz, Twist and Shout and the Macarena as
the three songs and dances. When the DJ chooses a particular
song, he signals the couple to come forward and dance while the
other two couples watch.
- Building with LEGO!
- DJ
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The DJ is responsible for choosing the
songs and communicating with the dancers. He is composed
of a Handy Board, a LEGO arm driven by a motor, a light,
and a decorative record that spins. The DJ operates as
follows after the start button is pushed on the Handy
Board:
- If the program is set to "dance-in-sequence", the songs will be played in the order of "Waltz", "Twist and Shout", and "Macarena"; if it is set to "dance-randomly", the above three songs will be played randomly.
- The arm of the DJ comes down to hit the touch sensor. When the touch sensor is hit, an infrared "ready" signal is sent to a particular pair of dancers instructing them to move forward; at the same time, the light is turned on.
- The DJ waits until the dancers have moved into position. His arm then comes down for the second time to hit the touch sensor, whereupon an infrared "start" signal is sent to the same pair. The record spins as the music starts to play.
- When the song and the dance are finished, the record and the light are turned off. The DJ waits for the first pair to go back before it starts this process again with the next pair.
For the arm we use 16- and 40-tooth gears to increase the torque and decrease the rotation rate by a factor of 2.5. The DJ arm is built so that it moves up and down when the direction of the motoris changed. The arm comes down to hit a touch sensor which is connected to the Handy Board.
For the record, we attach a wheel directly to the motor. It spins horizontally. The light is turned on when the arm comes down the first time and turned off when the music stops.
- Strauss
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Each dancer is an independent
two-wheel-and-one-pole vehicle built so that a Blue Dot
Cricket can be carried. Two motors which are connected to
the Cricket each drive a back wheel. This makes it
possible for the dancers to turn left and right.
- Twist-and-Shout
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These vehicles have basically the same
structure as the Strauss pair except that the distance
between the pole and the wheels is shorter. This makes
the "twist" movement more obvious.
- Macarena
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One motor is used to rotate the "arms",
while the second powers the wheels. We wanted each wheel
to have its own motor so that the dancers could turn. But
since the Cricket only has two motor ports, we had to
sacrifice the turning of the dancers for movable
arms.
- DJ
- Coding
The difficult part was to coordinate the music and the dance. Since the DJ and dancers communicate through infrareds only twice (the DJ sending "ready" and "start" signals before the dance) throughout the entire dance, they can be out of synch. quite easily. This is caused by a number of factors such as a flat battery of the Handy Board or Cricket, or the different texture of the surface of the ground.
An alternative method that would make the program more robust is to have a "synchronization barrier" in both the Handy Board and the Cricket, as suggested by Professor Franklyn Turbak. This forbids the flow of control in one of them to go forward until the same spot is reached by the other. Click here for more explanation. Unfortunately, we didn't have the time to test out this approach on our robots.
- DJ
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A note about the music: when we wrote the
music programs, we referred to a MIDI handbook for
correspondance between the actual piano key board and the
numerical representation of notes in Handy Logo: Middle C
is 60 and each half step higher or lower in a musical
scale increase or decrease the number by one. For
example, C# is 61, D is 62, etc.
- Strauss
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Music is stored in the DJ. This program is loaded into the pair of Blue Dot
Crickets that dance the Strauss Waltz.
- Twist-and-Shout
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Music is stored in the DJ. This program is loaded into the pair of Blue Dot
Crickets that dance the Twist and Shout.
- Macarena
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Music is stored in the DJ. This program is loaded into the pair of Blue Dot
Crickets that dance the Macarena.
- DJ
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Since a key part of this project is
presentation, we constructed costumes out of felt, pipe
cleaners, and sequins for the six robots and the DJ so that
they were dressed-up according to their roles.
Strauss Pair
Twist and Shout Pair
Macarena Pair
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We were pretty satisfied with the outcome of
this project. The morning of the presentation we had a final
struggle with flat batteries, and bugs in the programming.
However, they were worked out to the point that the Dancing
Crickets were finally presentable. Many members of the
Wellesley community came to see what had been built. In Sage
Lounge, where most groups were set up, there was so much noise
that people suggested we find a way to increase the volume on
the music. Looking around, we were also impressed by
our
classmates' projects.
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As a group, we learned that the process of
building robots requires not only creativity and foresight, but
also patience and team work. This class was fun in lots of
ways. Playing with LEGO again was very nostalgic. More
importantly, it was exciting to explore its construction
possibilities in a new light.