Underwater robots operating in the Arctic could soon be able to communicate through ice for the first time thanks to work by a British firm. West-Lothian-based WFS Technologies has developed a radio-frequency system that allows autonomous underwater vehicles (AUVs) to send distress signals through seawater and ice. The company plans to commercially deploy its technology next spring following successful trials in April 2010 with Norwegian AUV manufacturer Kongsberg Maritime.
AUVs are increasingly used by companies surveying the Arctic for environmental, energy and security purposes, in environments that are too harsh for manned operations. Because radiowaves don’t travel well through saltwater, robots that run into trouble have to surface to send out satellite distress calls but cannot do this when they are underneath sea ice.
WFS’s technology allows a robot to transmit a location signal up to 1km in distance that can be picked up by a helicopter once the AUV fails to return to base.
Saltwater acts as a barrier to radiowaves because its conductivity attenuates or weakens the signal, said Ian Crowther, senior vice president and general manager for WFS Energy and Environment. ‘The higher the radio frequency, the greater the level of attenuation,’ he told The Engineer. ‘The way to mitigate that is to drop the carrier
frequency so you’re operating at very low frequencies.’
Building on the company’s existing technology for transmitting through seawater, WFS had to address the problem that low frequencies reduce the signal bandwidth and so the amount of data the AUV can send. ‘WFS has innovated in a number of areas,’ added Crowther. ‘One is digital signal processing so that we optimise the bandwidth when we occupy very low frequencies. The second area of technical innovation is in antenna design.’
Specifically, the antennae had to be reshaped so that they could be installed internally while fitting the elongated design of most AUVs. The company also had to develop algorithms to determine from signal strength where the radio signals were being received from in order to locate the device.
The technology took several years to develop and was self-financed by WFS, which is working on commercial deals to deploy the system early next year.