Monthly Archives: March 2014

Cross-section of Changes

The cross-section of the carrier should look similar to the diagram below.  Note that the critical dimensions are:

  • the distance from the underside of the main hull to the waterline: this prevents Poolbot from dragging in the water
  • the width between the pontoons at the water line: this ensures enough room for Poolbot and the “lifting claw”
  • the main hull’s height must be sufficient to allow for batteries and control electronics
  • the width of the main hull should be sufficient for another solar panel

The actual length of the carrier will be somewhat less, scaled, then its experimental Navy cousin, making It squarish when in the water.

The chief problems now:

  • the lifting claw – how to get Poolbot out of the water and how to maneuver the two in close enough proximity to make this happen reliably
  • how to charge Poolbot without physical, wired connections
  • how to perform data exchange with Poolbot without physical, wired connections
SWATH cross-section
Carrier SWATH cross-section


Cutting a Wide SWATH

Impractical.  Inefficient.  Just plain difficult.

A lot of these terms came to mind when staring at the current state of Poolbot, and imagining trying to get it to cross a body of water larger than… well, a pool.  The most recent problems with getting long-range communications equipment mounted just compounded the negativity.

Then, an epiphany: why not have Poolbot carried by some other vehicle.  It could be simply dropped into position by a surface “carrier”, which needn’t submerge.  All the GPS, communications, solar charging, etc. equipment can be kept on the carrier, which would be more visible and more stable, with much more reliable communications. 

Having seen recent stories on the late, engineer-lamented Lockheed-designed US Navy experimental ship, Sea Shadow (IX-529, torn up for scrap in 2012), using a SWATH design for the carrier makes good sense.  Poolbot could be suspended under the main hull during surface transport, above the waterline.

This idea is brilliant.  So brilliant, in fact, that a NATO research group at Italy’s University of Genoa outlined a highly similar design… in 2010.

Nevertheless, despite a total lack of originality, a SWATH-based carrier for Poolbot is the new plan.  The NATO ASV design does not cover certain key details about deploying and recovering its AUV.  Nor are charging and comms covered.  To that end, here are a few specifics for Poolbot’s carrier:

  • solar panels mounted to the top and sides
  • “claw” under main hull for Poolbot, to keep AUV above the surface during transport
  • GPS, XBee, cellular antennas on carrier hull
  • at least one main-hull-mounted camera
  • batteries in main hull body
  • wireless communication (XBee) only with Poolbot – no wires for data!
  • wireless charging, if possible, for Poolbot (inductive charging pad under claw?)

All of this should allow both Poolbot and the carrier to carry out operations autonomously, indefinitely, without having to be opened up for anything other than serious drydock maintenance.  Even better, almost all of the original Poolbot plans and code can be kept unchanged.

Next post: dimensions and a mock-up…

While Building One, A Fleet Takes to the Water

Returning to the blog after a long stretch of work and personal exertion…

The UK’s Telegraph newspaper reports that Rutgers University has deployed a fleet of 16 autonomous underwater vehicles for ocean mapping.

Technical details are sketchy in the article (what exactly are “sustainable optic sensors”?), but the use of Iridium satellite communications is confirmation that it’s a viable approach for long-range control.