Although AUVs (autonomous underwater vehicles) are invaluable for collecting oceanographic data, they also tend to be quite large and very expensive. The Hydrus offers a much smaller and less expensive alternative, which still packs a lot of punch.
Most AUVs are torpedo-shaped robotic craft that can autonomously explore the underwater world for days at a time, using a suite of sensors to record video and other forms of data while they’re doing it. They are usually large enough to be launched and retrieved using cranes from relatively large surface vessels.
Renting or buying such a boat – as well as paying its crew – can be quite expensive. Additionally, depending on the make and model, the AUVs themselves can cost several million dollars. This is where the Hydrus is designed to come in.
Manufactured by Australian company Advanced Navigation, it measures just 470 by 260 by 260 mm (18.5 by 10.2 by 10.2 inches), weighs 6.7 kg (14.8 lb) and is expected to sell for around 50 US$000. Its small size means it can be carried on a commercial airliner as luggage and deployed by one person from a small boat.
Using seven electric hubless thrusters, it can travel at a maximum speed of 4 knots (7 km/h or 4.6 mph), dive to a maximum depth of 3,000 m (9,843 ft) and travel up to 9 km (5.6 mi) from its launch point. One charge of its lithium battery should be enough for about three hours of battery life. Its camera shoots 4K/60fps video, aided by eight LED projectors that put out a combined 20,000 lumens.
Users begin by programming a route for the Hydrus to follow. The AUV tracks where it is to this way, via several technologies.
First, while the Hydrus is still on the surface and able to access GPS satellites, it notes the GPS coordinates of its launch point. Once submerged, it uses onboard accelerometers and gyroscopes to track the speed and direction in which it is moving from this location. The AUV is aided in this by a sonar system, which it uses to monitor the speed and direction in which it is moving across the seabed.
Additionally, the Hydrus uses what is known as an Ultra-Short Base Positioning (USBL) system.
In this configuration, an underwater acoustic transducer on the surface vessel sends acoustic “pings” through the water, which the AUV receives and sends pings/responses to using its own transponder. By analyzing the time that elapsed between sending the first ping and receiving the reply ping – and the direction where the answer came from – it is possible to determine the current position of Hydrus. This data is sent back to the AUV in subsequent pings, letting it know where it is in relation to pre-programmed waypoints on its route.
It should be noted that if the USBL system can be used to change the route of the Hydrus if necessary, the craft cannot be remotely piloted in real time.
Video and other data – including conductivity, temperature and water depth – are recorded on an onboard hard drive for retrieval after the mission. That said, the Hydrus can also use a built-in optical modem to transmit real-time data across the water to a receiver on its host ship, in the form of fast pulses of light – the maximum range for this type of communication. is about 10 m (33 ft).
Possible applications for the Hydrus include ecological surveys, 3D mapping of the seabed (via sonar system), as well as underwater inspection of aquaculture facilities and offshore wind farms.
“The fact that it has acoustics, that it has a camera, that it has inertias, that it has in-flight safety batteries…all of this technology in one is a very big achievement,” said Peter Baker, Underwater Product Manager for Advanced Navigations. “It has all the technology you would expect in a much, much bigger and more complex system.”
The Hydrus should be commercially available by the fourth quarter of this year. In the meantime, you can see it in action in the video below.
Hydrus, the underwater drone revolution
Source: advanced navigation