After some non-robot delays (got to pay the bills), intellectual work resumes. Here is a top-level state machine for Nematon, showing the various modes of operation. Driving around occurs during “Surface” mode, while diving operations happen during “Dive” mode. “Remote” mode is intended for real-time control, akin to an RC car or airplane.
More software planning updates to come…
PDF Version: nematon-state-machine-july2015
The Federal Communications Commission recently sent two letters indicating that the celebrations regarding Nematon I receiving an official ship station license were premature (the letters will be posted shortly). The license has been withdrawn until further data can be provided.
In response to the FCC’s requests for additional information, the enclosed report was prepared. It includes some of the Sketchup drawings mentioned in the last post, reference listings of the sources of various components, plus an extended (amateur) analysis of the regulatory status of watercraft like Nematon I.
- Nematon I Design Report (PDF)
Due to a documentation requirement (which will be explained in the next post), some detailed drawings of Nematon I had to be generated in a hurry.
Using Sketchup and its associated Engineering Toolbox, a pretty detailed drawing in 3D was created. A couple of images are shown below. Some work is underway to embed a 3D image in this site for viewing, but until that’s done, these will have to do.
Note the exploded XBee antenna, courtesy of ERobishaw on 3D Warehouse.
As promised, here is an explanation for the Nematon I‘s unusual name. It’s a portmanteau of “nematode” and “automaton”.
- Nematode – a tubular roundworm with openings at both ends (http://en.wikipedia.org/wiki/Nematode)
- Automaton – a self-operating machine (http://en.wikipedia.org/wiki/Automaton)
Why the change? Poolbot Mk III was increasingly inaccurate. The shape of Poolb… Nematon I is still based on tubes and, though an automaton, is about as sophisticated as a roundworm.
After some study, a tough decision, filling out of forms, and payment of an application fee, the Federal Communications Commission (FCC) has approved a Ship Radio Station License, Recreational or Voluntarily-Equipped (SA) for Poolbot. Poolbot now has an identifiably-American MMSI (see below) and a callsign: WDH7858.
This was tricky. Poolbot is intended to eventually operate internationally, and US treaties apparently require a special radio license for such craft. However, a lot of the laws and regulations are for “vessels”, which carry passengers or cargo, and are usually of a certain length or gross tonnage far larger than Poolbot will ever get.
A letter was filed with the FCC stating that Poolbot is a “drone”, explaining that passengers and cargo are impossible, and specifying that no search-and-rescue craft would ever be required if Poolbot were to get into trouble.
No questions asked, they took the money and issued the license. Poolbot is now government classified as a “Pleasure Ship”, specifically a “Research or Survey Ship”
What remains unknown is whether Poolbot is operating legally if the Restricted Radiotelephone Operator (required for the radio license) is physically miles away from the craft. The law really hasn’t caught up to the drone age yet.
Why do any of this? To get an MMSI number for an AIS unit – in essence, a unique ID that would allow live tracking of Poolbot via the web (see marinetraffic.com or vesseltracker.com) or using appropriate equipment on other ships and Vessel Traffic Services. This lets Poolbot be “seen” in waterways and prevents it from becoming a hazard to navigation.
One last point: the FCC form requires the craft in question to have either a registration number from the US Coast Guard or the state of California… or a name. US Coast Guard and California state regulations still only apply to cargo- and passenger-carrying vessels “used or capable of being used as a means of transportation on water” or engaged in fishing or towing operations. So Poolbot now has a new name:
An explanation of the name will be the subject for the next post. Thanks for your patience.
Congratulations to the lads at Blue Robotics, who met their Kickstarter funding goal… twice over, with a little help from Poolbot. This means that 3 T100 thrusters, with electronic speed controllers (ESCs), will arrive here within 2-3 months.
With the thrusters being an integral part of the Mk III design, it’s time to consider the actual total costs of Poolbot’s makeover. Presenting the bill of materials (BOM)…
As seen below, the low-cost MIT SeaPerch design is now firmly in the rear-view mirror. Fortunately, many of these items were already on-hand. The costs of the larger PVC and sealing the solar panels against water are not shown.
Poolbot is evolving. The original prototype successfully floated and dove, while the addition of the ComPod credibly turned it into Poolbot Mk II.
Mk III is now taking shape.
The technical details for the Mk III will be posted soon. However, the basics design involves the same core electronics as before plus new physical features:
- separate compartments for the thruster batteries
- solar panel mounts
- new thrusters
- solid frame for the electronics
- hollow posts for communications antennas and the GPS module
The last two can be seen below. Thanks to Open Beam, some standoffs and a sheet of acrylic, the electronics will have a solid mounting and cleaner wiring. The Mega and two separate dummy shields should suffice to connect everything.
Using a blank perfboard, PVC, epoxy, a plastic I-beam, and a Dremel, a pretty smart-looking GPS post has taken shape. The SUP 500 was removed from its old shield and soldered directly, with backup battery, to the perfboard. Tested with SkyTraq, it works like a champ.
After a fairly long dormant period, in which Poolbot took a local vacation, work has resumed. Much of this consists of research and planning improvements. Some highlights:
- The GPS has suddenly become spotty, which may drive finding a replacement.
- The MSI depth sensor has been lost, despite the shop now having small PCBs and an air-soldering station to attach them. Fortunately, the good folks at OpenROV have a combination depth sensor, gyroscope, and accelerometer board that works over I2C.
- Just stuffing wires, batteries, and boards into the central tube isn’t reasonable. OpenBeam allows a more rigid structure to be used, supporting sliding in of PCBs or acrylic plates.
- The wax-potted motors are, at best, unreliable and inconsistent in their speeds. Low-cost thrusters are hard to find… except the Blue Robotics team now has the T100, which will explode onto Kickstarter in a few days.
- Speaking of which, their solar-powered autonomous surf board has some common design elements with Poolbot, including solar panels, an Arduino Mega-based microcontroller system, and a RockBLOCK satellite communications unit.
- Finally, The Economist has a story on a system of Arctic environmental measurement paid for by the US Navy, involving autonomous robots called Seagliders and Wave Gliders. The Wave Glider image bears a strong resemblance to Poolbot’s intended surface profile.
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