Inside Unmanned Systems

OCT-NOV 2017

Inside Unmanned Systems provides actionable business intelligence to decision-makers and influencers operating within the global UAS community. Features include analysis of key technologies, policy/regulatory developments and new product design.

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61 unmanned systems inside October/November 2017 ENGINEERING. PRACTICE. POLICY. Their prototype, Ichthus, is about a half-meter long and weighs roughly 4.7 kilograms. The re- searchers said it could swim up to 50 percent more efficiently than traditional propeller-driv- en submersibles. Moreover, its turning radius is just one-tenth of its body length, making it about five times more maneuverable than convention- al unmanned underwater robots, Yang said. Control Hub Ichthus uses GPS to localize its position on the surface of the water and gyroscopes and accel- erometers to help it determine its attitude and heading. When it goes underwater, it uses infra- red and ultrasound range sensors to keep track of nearby obstacles, a water pressure sensor for depth detection, and an inertial navigation sys- tem to help keep track of its location. A floating docking buoy also has an ultrasound modem that transmits USBL (ultra-short baseline) acoustic pulses to help Ichthus localize itself. This buoy also serves as a control hub that can communicate with multiple robotic fish, relay instructions from onshore operators to the ro- bots, and transmit back data the robots collect. "It can autonomously travel along a fixed trajectory and can be remotely controlled if necessary," Yang said. Ichthus uses temperature, electrical con- ductivity, pH, turbidity and dissolved oxygen sensors to monitor the water, and its lithium- ion battery enables it to operate for about four hours. It can currently swim at up to 6.85 km/ hour and dive up to 30 meters, but Yang sug- gested that a larger robot could swim up to 30 km/hour and dive up to 1,000 meters. When Ichthus runs low on energy, it can au- tonomously return to its f loating docking buoy to recharge, much like a cleaning robot, Yang said. "The most difficult part was that all the sensors, actuators, communication, batteries and waterproof design had to be applied to a relatively small robot size," Yang said. Ichthus has undergone field tests in South Korea in the Han River and in a lake near the area of Suin-Ro. Yang suggested it could now not only help patrol fish farms, but the fact that it is agile and looks like a fish instead of a robot suggests that it could be used for military applications as well. Robot Swarms Instead of designing singular sw imming robots that mimic fish, Hydromea, a start- up spun off in 2014 from the Swiss Federal Institute of Technology in Lausanne, seeks to develop swarms of pollution-detecting aquatic robots. "If people take water-quality measurements they usually measure just one or a few points in space and time, but if you want a 2-D or 3-D map of a spill or an outf low plume, one measurement is not going to tell you much— and if you go to another spot to collect data, the conditions may have already changed by the time you get there," Hydromea co-founder Felix Schill said. "If you want to get a lot of measurements quickly for a high-resolution snapshot of what is going on, then you need 10 or 20 robots to measure an area simultaneously," Schill said. "Ideally, they'll also be coordinating with each other to focus on the places that are interesting and not spend so much time on the parts that are not interesting." The main problem with coordinating a swarm of underwater robots "is that radio waves don't propagate through water very well—neither radio communications nor GPS nor mobile phone signals—so you can't use those as you would with airborne drones," Schill said. "Underwater is the most challenging en- vironment of them all, even more so than space in some sense," Hydromea co-founder A lexander Bahr said. The fact that radio waves do not penetrate well through water means "a lot of the things that aerial, surface water, ground and space drones can easily do are much more difficult underwater," he said. "IF YOU WANT TO GET A LOT of measurements quickly for a high- resolution snapshot of what is going on, then you need 10 or 20 robots to measure an area simultaneously." Felix Schill, co-founder, Hydromea

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