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- Objective: To build a long,
multi-jointed, tentacle-like robot arm with
a wand as the end effector. When the program
is executing, the robotic arm dips its wand
into a bowl of bubble solution and with gentle
acceleration, it sweeps out a pair of large
bubbles. The arm then continues and repeats
the action.
- Parts:
-
Robix
Rascal Robot Kit/Construction Set
- The Bubble wand: made of malleable wire
from craft store or florist. Wires are 1/16"
(1.6 mm) and 1/32" (.8 mm).
- Plastic Bubble solution bowl: approximately
9" (23 cm) in diameter by 5" (13 cm) deep.
- Bubble solution: 1 gallon / 4 liters
large-bubble solution is found at toy stores.
- Electrical tape to hold wand to link.
- Weight to keep base from tipping.
- To learn: This project
can be messy but it is worthwhile as it demonstrates
the superior repeatability of the robot when
compare to human. The robot makes 2 sweeps in
each direction, 4 in all. Each sweep makes two
bubbles with the second bubble floating to the
backdrop and breaking in nearly the same place
each time. The robot can do this many times
accurately in succession.
Please follow the manual of the Robix Rascal
Robot kit when you build your own bubbler robot.
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- As a simple hoop does not hold enough bubble
solution at the edge to make good bubbles, thus,
when making the wand, make sure that the smaller
wire is spiraled around the larger. These spirals
imitate the "fringes" found on bubble wands.
- Try the wand out by hand with the bubble
solution. We found that stirring the solution
to make it froth a bit helped to produce more
consistent bubbles.
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- Assemble the bubbler robot and servo motors
as per drawing (with one less link shown).
- You will need to clear and mark off a large
safety area to accommodate the reach of this
robot, which is about 20" (about 50 cm).
- You may need weight to hold down the base
so it does not tip when the arm extends fully.
Don't use a book, as it will get water- and
soap-damaged.
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- Avoid overstraining the servos with quick
stops of this arm, by doing so, we can reduce
servo gear life or can break a gear outright.
- To minimize splashing of soap solution,
program the dipping and sweeping actions with
an empty bowl.
- The dipping action of this robot, as built,
involves not just a single axis but several
at the same time. This dipping position is not
necessarily the same as the starting position
for the sweeping motion that produces the bubbles.
- Since the extended arm has considerable
momentum, use the lowest values of accel/decel
which will give good performance. Start with
these accel/decel and maxspd settings, then
experiment for better bubbles.
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