Baby AUV is a low cost, open source micro AUV (autonomous underwater vehicle) intended for environmental monitoring applications. Currently it has completed basic manoeuvring and navigation tasks, and the payload sensors (CTD) is functioning.
To move forward, the project needs a real-world problem and a domain expert to guide further development and to take the AUV operational. Contact me htarold@gmail.com if you think Baby AUV can be useful for you, or if you are interested in working on the project. Ideally a community can be grown to handle the development and operational issues.
At least initially, Baby AUV should be deployed in inland waters free of current. Ultimately, Baby AUV will be useable in coastal waters.
You can see a clip of Baby AUV here.
Length: 0.6m (1m including antenna) Displacement: 3.5kg Cost: BOM cost can probably be held down to USD500. Depth: the thruster gland has been tested to 40m; the EC probe is rated to 50m; the hull is probably good to a few hundred metres. Endurance: 48 hours Speed: 2kt (this implies range is about 100 miles) Vehicle sensors: GPS, compass, accelerometer, depth, odometer (via propeller) Payload sensors: electrical conductivity, temperature. Other payloads can be added. Communications: RF modem (434MHz).
Unlike most AUVs, Baby AUV has no fins, and has only 1 thruster, and a moving mass actuator (2 degrees of freedom). But by keeping it mechanically simple and therefore cheap, it has to employ novel methods to turn. Gross changes of direction are achieved by stopping, pitching nose up (by moving its internals to the rear), then slowly reversing the thruster. While the vehicle slowly descends, it also rolls about a vertical axis as it reacts to the thruster torque. At the appropriate point, the thruster is stopped and the AUV is pitched horizontal, pointing in a new direction.
While under way, small changes in heading are achieved by modulating the torque to the propeller which has only one blade. This tends to walk the rear of the AUV slowly one way or the other. Another way to think about this is the asymmetry of the single bladed prop causes the AUV to wobble slightly in normal use. By appropriately modulating it, the wobble can be biased more one way than the other.
It should also be clear that Baby AUV is capable of hovering.
Baby AUV depends on GPS for localisation. This means that the AUV must surface frequently in order to get a fix. Conveniently, for most missions the surface is very close by.
Most AUV projects are first and foremost robotics projects. By keeping this AUV simple, I hope to de-emphasise the robotics aspect in order to let the data sampling take centre stage. In a sense, Baby AUV can be regarded as a self-propelled multiparameter probe, where one of the sensors s replaced by a thruster.
The relatively high endurance and long range makes it suitable for prolonged monitoring missions. The AUV visits the waypoints indicated in a mission script, collecting data along the way. There data are stored on the SD card, and are also opportunistically broadcast when surfaced. If out of radio range of "home base", any other AUV or aerial drone in the area can copy this data to return to the user. (A fountain code will be used to reduce the amount of redundant data transmitted.) Use of such data mules make data available sooner, as well as extending the AUV's sampling domain.
Apart from using the CTD or other payload sensor, one novel use is to employ the AUV itself as a hydrometric pendulum. To do this, the AUV is trimmed slightly negative (tending to sink instead of float), and is parked on the bottom balancing on its nose. Any current near the bottom (not powerful enough to dislodge the AUV) will cause the AUV to change pitch and heading like an upside down windsock; these are picked up by the vehicle's compass and accelerometer. This can provide a simple way to measure the bottom shear (e.g. for sediment transport studies), which is otherwise expensive to measure.
Baby AUV's hovering capability can be used to turn it into a self-deploying and self-recovering fixed depth Lagrangean drifter.
Baby AUV can be used in a high surface traffic area. The small size, low speed, and low cost means that the AUV will sacrificially lose in any collision with another vessel. Conveniently, when surfaced the AUV will be vertical, which pose softens impacts.