From Wired Design:
A year ago, Greg Holloway set out to build an ocean drone, based on the tiny Raspberry Pi $35 computer.
Wired covered the start of the project, called FishPi, last summer, as Holloway was working on a Proof of Concept Vehicle (POCV), which at that time was essentially an upturned lunch container on the hull of a model ship. Now that he’s approaching the one-year anniversary, the initial testing and research is paying off, and with collaborator Al Gray he’s revealing plans for the final design to the FishPi community.
“When I began the project I had the optimistic expectation of being on the high seas by now,” says Holloway. “FishPi will cross the Atlantic, it might just take a bit longer than I expected!”
What the FishPi looks like now.
“The Proof-Of-Concept Vehicle (POCV) is finished, just about,” says Holloway. “I began the project with little to no experience of robotic control so even the smallest of details has taken, in some cases, weeks of investigation before a decision was made and a part purchased.”
In fact, Holloway says, research has ended up being the bulk of his time on the project, to which he’s devoting ten to twenty hours a week.
Perhaps the biggest change is the addition of software engineer Al Gray to the team.
Gray has taken on responsibility for incorporating the device’s various bits of hardware into a functioning system. “Having begun with almost nothing, Al Gray has done a fantastic job integrating the Compass, GPS, Temperature Sensor, Rudder, Webcam, and the Electronic Speed Controller into the C & C [command and control] software,” says Holloway. “We can drive the POCV remotely using the Webcam as a visual guide, but it has only been done in the bath so far.”
“Since seeing Stanley (the car that won the DARPA grand challenge) at the Smithsonian a few years back, I’ve been inspired to get involved in an autonomous robotics project,” says Gray, revealing his enthusiasm for the project.
Now that they have managed to get the POCV to drive, the next big challenge is getting it to drive itself. “The starting points for this are well established but calibrating for the particular craft and motion model will be fun,” says Gray.
What the FishPi looked like in June.
Meanwhile, Holloway has been working towards a design for the prototype. Gone will be the clunky plastic box. The sleek new design is built around the requirements of the solar panel that will ensure the vehicle remains powered. Though Holloway was hoping to avoid the need for a keel, the shape of the panel has ended up demanding one.
“Given that the vehicle is likely to capsize in rough seas it would be silly not to have a self-righting mechanism,” says Holloway. The keel will serve double duty as protection for the trolling motor and the weight bulb may be used to house certain instruments as well.
After ensuring power with the panel, the biggest concern for the hull is keeping the electronics dry. They’ll be stored in cases from Pelican, with packs of silica gel in case of small leaks. The space in the hull between the cases will then be filled with high density self-expanding foam.
If you want to build a POCV of your own, Holloway has released WIP information on Instructables. And don’t worry about getting your stuff wet. “The beauty of the Raspberry Pi and most parts is their relatively low price, if something goes wrong, you can always get another one!” says Holloway.
Comments
I was doing research for a UAV submersible and like was mentioned before I was planning on pressurizing the electronics bay. You could epoxy the pelican cases closed and might be able to get a small co2 bottle regulated down to 5-10 psi. You would obviously have to test this but its one of many options.
For cooling I was planning on mounting all of the electronics onto a aluminum heatsink and epoxy it to the case. Plastic is not a good conductor but over a large enough area with water crashing over it the plastic can be kept cool.
I know in my research i came up with a more elongated shape that would almost pierce through waves with minimal buoyancy. You may be able to ask a naval architect for opinions if your current vessel design is not set in stone.
One area i wasn't sure about was how to keep alge from growing on the vesel. I was looking into making the hull from polycarbonate or acrylic and housing a UV light inside that would possibly kill anything that tried to grow on the outside. This light would only need to turn on maybe once a day for a few seconds from what i read. There was alot i still had to research at this point.
I really look forward to updates, This project is very neat!
@ Michael Water turbine for power for the electric propulsion motor? Excellent idea ! Perpetual motion! wind turbines would work if they are all direction vertical cages It could carry a ASIS ship identification system so ships would know where it was .It would really freak the guys on the ship out especially at night it would show up on their electronic chart and riding low in the water they would not be able to see it from the bridge not even if they were right on top of it . Yes there is a ship on the screen look out nothing there ? a "Ghost ship!"some one mentioned pressurization maby 2 atmospheres. If a ship runs it down it could go down 30 feet or more before it pops back up . there is stuff washing into the shore every day in British Columbia from the big wave in Japan a while ago with no Guidance system or means of propulsion so it is possible Good Luck!
There might be a difference between the atlantic ocean and your bathtub. I think such a toy boat will be ballistic in the ocean for most of the time. It will be a bottle message with a microcontroller ..
I am going to state the obvious - this things does not require a Raspberry PI to operate and it is impractical to use it (at least 5W power consumption)
Along with a solar panel could go a water turbine with could kick out a lot of power. For the motor, heat won't be a problem, but the electronics like the pi and esc may get hot after months of running. A water cooling system would work well, but has high power requirements. Maybe small wind turbines on top to harvest electric from storms?
There are so many superior options besides the raspberry pi, he must be getting a lot of publicity from calling it the fishpi. Powering that 700Mhz multimedia CPU from a solar panel is about as impractical as possible.
A few thoughts:
If your really serious about having this thing motor along (at least during the day) and cross the Atlantic, at least use a brushless trolling motor or better still make your own like the ROV people do.
Brushes suck for this kind of use and any leak means instant failure.
If you design your own brushless, the (properly insulated) motor coils and armature can actually be directly exposed to the Sea water without negative consequence.
If you use an exposed motor, shaft seals won't be important or necessary, but bearings designed for submerged use in salt water will be very important.
For exposed steel, use Stainless or coat it with Epoxy.
You might want to consider weighting it such that it is completely self righting and allowing it to operate low enough in the water so that it is frequently washed over completely by waves (removing occasional Sea Gull poop.)
Obviously it needs to be 100% water tight so some thought might need to be given to internal air pressure equalization.
As far as Great Whites, try real hard not to look like a seal and as far as Humboldt Squid, make it fairly strong; once they figure out that you aren't food or a mate they will probably let go.
Try and avoid the main shipping lanes, I suspect that's one thing you can't really compensate for although if you had some reasonable way of tracking it, you could possibly put out a notice to "ships at sea" of its current location.
You may have already thought of all of this stuff, just thought I'd mention it in case you hadn't.
Good Luck!
You might want to slope the decks some what or run a wire across the top suspended on 2 poles An object floating at sea 1.71 m by 0.87 m with a flat top seabirds are going to land on it and crap all over the solar panels it looks like bait and might get bitten by a Great White and if the motor is making a humming sound in the water attacked by Humboldt Squid That is the first hundred miles ! Good Luck