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89 Ocean Business 2021 | Show report turns, in which they have to take care not to hit each other.” There are two operating modes that allow the Quadroin to do this, one that relies on Evologics’ own USBL positioning network, which is up and running, and another based on internal sensors that is still under development. “With the current system, you drop two or three of our USBL buoys into the water without any calibration,” Bannasch explained. “They connect to each other automatically and create an underwater positioning network. The AUVs then maintain their position, depth, formation and speed with reference to the network.” The core of this capability is a comms scheme in which each individual Quadroin reports key data such as its identity, position, course and speed to the network. The network then relays that information to the whole formation. “In the first tenth of a second, the first robot shouts to the network and the network shouts back to everybody,” Bannasch said. “In the third tenth of a second, the second robot shouts to the network, and in the fifth tenth of a second the third one does. “So at least every half a second, each member of the formation receives the information it needs to correct its position and avoid its swarm mates.” The second mode does not require an external positioning network but does require each Quadroin to have additional sensors. “Currently, we have an omnidirectional modem in each AUV so that they can all shout out, but not all of them can measure the direction of the incoming signals,” Bannasch explained. “In order to have them positioned with respect to each other they also need directional hearing, for which we need to add three or four more transducers.” Conceived as part of a scientific water monitoring project, the Quadroin was first intended to map vortices in salt water by swimming through them in formation repeatedly and at speed. The data resulting from this would enable the creation of a 3D matrix of each vortex, containing information such as salinity and temperature distribution. Subsequent discussions with customers have identified more tasks that the Quadroin could undertake. “There are applications in seafloor mapping and object search & location missions, where you need sensors such as sidescan sonar, cameras, collision avoidance, multi-beam sonar, object detection, magnetometers and more,” Bannasch said. “So we have redesigned the vehicle internally to integrate automatic object recognition cameras, collision avoidance and sidescan functionality.” Current work is focused on sensor and payload integration for various customers, he added. UAVs that can take off and land on water are rare birds, but an example was on display at the show on the Plymouth Rock Technologies stand in the form of the XW-L (formerly the TD7) hexacopter on floats. Ben Pickard said he sees a future in amphibious multi-copters to serve as platforms for a variety of water monitoring instruments, their unique capabilities allowing them to land and take measurements then fly to a new position, repeating the process to cover larger areas more quickly than would be feasible by other means. The XW-L is the first of a family that now includes derivatives with payload capacities ranging from 0.5 to 2.5 kg. It is made predominantly from carbon fibre reinforced plastic. A transparent Perspex dome on the front is an option for customers who want to mount a camera system. Most prominent is the pair of large foam floats that provide the buoyancy, suspending the UAV just off the water’s surface. The payload bay is typically used for mounting winches for deploying sensors or pumping equipment for collecting samples of water, for example. Pickard said it is also possible to make the dome submersible if the customer wants the ability to look into the upper layers of a water column, although that would require some customisation in the build. Several universities are operating XW-L systems for monitoring microplastics, acoustic monitoring and sea bird migration, he added. Unmanned Systems Technology | February/March 2022 Plymouth Rock Technology’s XW-L