Uncrewed Systems Technology 046

23 you don’t know what compensation you have to make until you see where you are going,” he says. “So you sense motion and then act to compensate.” The robot takes several cycles to recover, but Wilson argues that this is a good thing as it reduces the loads on the legs. “By no means is it a good thing to correct within a stride, because that means you apply forces that might exceed mechanical limits. Say you just push harder; that’s great until the leg breaks or the foot slides.” Many legged robots use hydraulics because of the need to apply a wide range of force levels responsively to legs moving at low cyclic frequencies, such as 1 Hz, for which electric motors are not so good. “Hydraulics are lovely things, they deliver remarkable amounts of energy very quickly and with quite exquisite control. The downside is that you throw away a lot of energy in doing so. “Take a hydraulic ring main at 3000 psi. You are probably going to dump a quarter of the energy in the control valves, and much of the rest in the actuator. Any hydraulic system spends a lot of energy making oil hot, but you get some work out of it in the end!” Actuator technology is an area of robotics where there is a lot of room for improvement. “The perfect actuator is certainly a long way away from existing,” Wilson says. Airborne science Much of the science he does involves tracking animals in the wild, particularly in the open spaces of Africa where the use of aircraft is essential, along with aerial survey work. It encompasses creating instrumentation packages placed on animals (miniaturised to record without affecting their locomotion or behaviour) and sensor suites for various multi-copter UAVs and a Groppo Trail manned light aircraft. He has also used quadcopters for PIX4D survey work, which combines photogrammetry and CAD. That makes computer reconstruction of the environment – “anything from game trails to trees and other obstacles” – much easier. UAV pros and cons He says using quadcopters for his work has limitations such as licencing issues, noise, lack of range and the cost of the higher-end systems. “Where I work in Africa, turning up with a UAV is instant trouble for a variety of reasons, from natural government concerns about security issues to the general public being a nuisance with them and the fact that they could substantially disturb wildlife,” he says. “If you film elephants with a UAV, a quadcopter 100 m away will disturb them, probably because it sounds like a swarm of bees.” For these reasons, he and his colleagues built the Groppo Trail from a kit, equipped it with a sensor suite including a Lidar that can be operated by the pilot, and he flies it himself on surveys and tracking missions. One area where UAVs shine in his animal tracking work though is as platforms to relay the signals from GPS- equipped collars, which are typically fitted with LoRa radio modules that transmit very small volumes of data. “I only need the last bit of the GPS position because I know it’s in the southern hemisphere, and I know it’s within 100 km of where it was yesterday,” he says. “So I can transmit 40 to 60 km over LoRa from an aircraft or a UAV.” He reports that a growing number of masts are being built to carry LoRa WAN services in support of anti-poaching operations. “Using a bunch of UAVs is easier than setting up masts, so as radio platforms they have a lot going for them, and they are especially useful in the low- infrastructure environments where I work, which are utterly vast.” Wilson was made a Fellow of the Royal Society of London in April 2020 for his outstanding contributions to science. “In career terms, that’s probably the biggest box you can tick from a science point of view,” he says. “I am very fortunate to have a job I enjoy very much, and hope to continue my research for a long while yet.” He comments that instrumentation is becoming a “well-grazed field” but adds that there is still novel work to be done, particularly in understanding legged robot control. “Control is a very broad term, from control through structure to control through active instrumentation. “I will carry on with the aviation side of things, with the flight research that’s going on in the lab. “The term ‘legacy’ sounds a bit over the top, but an important part of my role is to mentor and develop the next generation so they can deal with all the things we couldn’t do.” Uncrewed Systems Technology | October/November 2022 Born in 1964, Alan Wilson attended the Glasgow Academy in his native city, going on to study veterinary medicine and physiology at Glasgow University, graduating in 1987. A PhD in anatomy from Bristol University followed, focusing on the mechanical basis of tendon injury. Remaining at Bristol University, he worked as a post- doctoral research associate and then as a lecturer, moving to the Royal Veterinary College in 1996. He is a director of the Company of Biologists, a non-profit publisher that supports and inspires the scientists. Professor Alan Wilson