One of the main problems of UAV drones stem from their principle of control: if the radio signal is lost it may compromise the success of the mission. Furthermore, under such conditions it may quickly become impossible to retrieve the equipment back, except for those scenarios when flying robotic platforms possess a capability to automatically track their way back home.
This issue is especially sensitive in the military and rescue operations where the signal may be jammed deliberately or lost due to signal attenuation behind thick walls or in under the piles of rubble. So what is the best way to overcome this apparent limitation?
Equipping drones with more powerful transceivers probably is not an option as any signal transmission requires power, and a stronger signal means quicker depletion of batteries. Also, stronger signals may cause interference with other electronic devices, while the technology itself is still not immune to even relatively simple electromagnetic jamming.
Now, a company called CyPhy Works proposed using a simple but tested and reliable alternative: tethering control signal via a fiber-optic cable. Yes, you are right – you have to store that cable somewhere inside the platform of flying robot, and you need a cable long enough to support more distant searches. But the representatives of CyPhy Works claim it is possible to use a cable thin enough to resemble a hair-like filament light enough to be carried onboard. The cable would unspool from a small bobbin in a way that doesn’t restrict the movement of the drone.
There are certain advantages of this approach. One – and probably the main one – is the reliability. Signals transmitted over optical fiber are basically immune to electromagnetic interference compared to control using radio waves. The second advantage is related to the capabilities of data transmission: the throughput of optic cables is sufficiently large to transmit a high-definition video simultaneously with control and voice communication signals. Also, in the future similar drones could be powered using another cable extending directly from the ground-based power source.
According to an article published on IEEE Spectrum, the current versions of unmanned cable-tethered aircraft include a 140-centimeter-long quadrotor UAV capable of hovering in place up to 150 meters high, and an 18-centimeter wide, 80-gram hexacopter that could be fit inside backpacks or even pockets. Developers from CyPhy mention that their creation is initially aimed at military market, but there are plans for civilian market as well.
An apparent drawback of this idea involves a somewhat limited cable length and possibility for a drone to snag while laying the cable over different obstacles. But in military and rescue fields cables could be considered as consumables (most likely including the robotic vehicle itself).
Written by Alius Noreika