"Bart" - Argonaut Jr's
Underwater ROV
If Simon Lake were building the Argonaut Jr. today he would
certainly included an ROV. ROV's are like remotely controlled submarines with video cameras
and often robotic arms that allow the operator to work underwater
for the safety and comfort of a boat above or from within a
submarine.
Putting a video camera on an ROV and flying it underwater is
actually can be done with quite easily using a joystick, some
electronics, bilge pumps, and an underwater video camera. We
have already built a simple ROV named Bob. You can see more
about Bob here: Building Bob
Argonaut Jr's ROV will be name "Bart" after Simon Lake's cousin that
help him build and test the Argonaut Jr. Bart will
be build from easy to find and relatively inexpensive parts such IP
and USB cameras, motors and servos from the Radio Controlled (RC)
hobby suppliers, a play station game controller and those parts will
be driven by RoboRealm software that makes connecting and
programming as easy as it gets.
The Parts
1) RoboRealm
-- Software suite that processes the video, and has easy to use
interface modules for the game
controller and the Pololu Micro Maestro controller that runs the servos and motor
speed controllers. The game controller will use the
joystick module
and the Pololu servo controller has a custom
Pololu
Maestro module. RoboRealm also has a web server to make the video available to the Internet
when a connection is available.
2) Pololu,
Micro Maestro 6-channel USB Servo Controller and
Documentation
and Forum
-- A very small card that controls the RC motors Electronic Speed
Controllers (ESC) and servos.
3)
Lowrance StructureScan, sonar imaging is unique in that it use
Ethernet network to transfer the signal between the the supplied
network box and the display console making to possible transmit the
transducers information up the ROVs umbilical. By slowly
rotating the transducers two side scan transducers 180 degrees with
a servo; we will be able to capture an 360 degree view of the area
around the ROV out to and beyond 100ft even in muddy water.
4) Putting a compass in the field of view of a camera works nicely,
but we'll go a step further and add a
digital
compass that provides the heading over an RS232 serial interface
with the Pololu, Micro Maestro.
5) Microseven IP camera has
an SD card on it where it can record D1 video as well as a built-in
web server enables video live anywhere over the internet.
Thrusters
We are using RC (radio controlled) hobby type motors with props
added on for Bart's thrusters. These are widely available and
relatively inexpensive, small, but powerful motors than can be run
even in salt water with the motor completely exposed to the water.
Read more here: DC
Motors and Props.
We tested a 1000 Kv Outrunner Brushless RC Motor and 30 amp and 30
amp BEC ESC (Electronic Speed Controller) $8.50 for both, plus
another $8 for shipping from China. The results were mixed.
One of the three motors caused the ESC to shutdown after a short
time of running underwater. The cause is likely due to the way the
ESC senses an overload condition in the motor, so it shut off power
to the motor even when there was not really an overload.
However the performance at just a 5 amp draw. We also learned that
we need and ESC for RC Cars that have the ability to run the motor
in reverse.
800kv D2830 RC 800g Plane
Outrunner Brushless Motor $18
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Aeolian 45Amp ESC 2A BEC
for 1/10 RC Car Brushless
Motor $27 |
Hitec HS-755HB Karbonite 1/4
Scale Servo Futaba Jr. $26 |
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Mounting a prop to this motor was fairly easy. The motor's
dimensions are 51.6mm x 23.9mm x 8.5mm. The hub of a fan
from a PC power supply is about 14mm, so we turned a piece of 1" Sch
40 PCV pipe in a lathe to fit over the motor and into the fans hub.
It would take more time, but you could do this with a drill, small
drum sander attachment to fit inside the PVC pipe so it spins the
pipe, and sand paper to cut down the outside dimension of the PCV.
We purchased 5 - 45 amp ESCs for cars because they can run the
brushless motors in forward and reverse. Add we went with 5,
even more powerful motor that runs at 800Kv or slower which is
better for turning bigger props and getting more power. Finally we
got a couple of 1/4 scale servos for tilting the camera and rotating
the sonar transducer.
Resources
www.hobbyking.com Good
selection of RC Motors and ESC.
http://www.ertyu.org/steven_nikkel/ethernetcables.html How to
wire Ethernet Cables
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