Unmanned Systems Technology 016 | Hydromea Vertex AUV | Power management systems | Unmanned Space Vehicles | Continental CD-155 turbodiesel | Swift 020 UAV | ECUs | DSEI 2017 Show report

“Now we have a universal device. We would not have had the space for an acoustic modem and an altimeter.” Collision avoidance is another possibility, as Bahr explains. “We did some experiments last year with our acoustic system to see if we could pick up echoes from other vehicles and objects, because we send out pings all the time anyway.” The tests involved the acoustic system, including a four-channel receiver, mounted on an autonomous surface vessel. With this, Hydromea was able to determine the range and bearing of large obstacles such as a lake bottom and harbour walls by analysing the returns from the ranging pulses sent out for inter- vehicle localisation. Vertex is not limited to acoustics for underwater comms. Schill points out that Hydromea has also investigated low-frequency radio as well as optical devices, pointing out that both have their strengths and weaknesses in terms of range and data rates. Normally, at short range it is possible to achieve high data rates, while at longer ranges the rates drop significantly in all these technologies, Schill explains, so the company uses a combination of optical and acoustic comms technologies for different purposes. By operating vehicles in fairly close proximity, Hydromea seeks to avoid the range limitations associated with acoustic comms under water. By building in a lot of processing power they also aim to avoid the bandwidth limits inherent in underwater comms technologies. Eking out bandwidth “The bandwidth we have under water is so low that even with ten vehicles we run into these limits very quickly,” Schill says. “That’s why you really need to minimise the amount of information you want to exchange, so you want to have An aperture in the outer ‘wet’ hull allows a glimpse of one of the lithium-ion batteries in the pack inside the transparent pressure hull (Photo by the author)