Issue 37 Unmanned Systems Technology April/May 2021 Einride next-gen Pod l Battery technology l Dive Technologies AUV-Kit l UGVs insight l Vanguard EFI/ETC vee twins l Icarus Swarms l Transponders l Sonobot 5 l IDEX 2021 report

98 PS | The Eelume snakebot D espite not having legs, snakes are arguably the most versatile animals in terms of locomotion (writes Peter Donaldson). They can move over any kind of terrain, from loose desert sand to dense jungle, they are expert climbers and swimmers, and a few can even glide as far as 100 m through the air after leaping from trees. Science is continually learning more about how snakes achieve such feats, and for decades robotics engineers have been trying to perfect machines that can reproduce their movements. So far, seven distinct methods of snake locomotion have been identified – simple undulation, lateral undulation, sidewinding, concertina motion, rectilinear movement, slide-pushing and the only recently documented lasso motion for climbing smooth, vertical cylinders. Snakebots can do most of these things well enough to make useful reconnaissance, inspection, intervention and even surgical tools to carry out tasks in places that are inaccessible to any other kind of robot. Most snakebots have modular segmented bodies with multiple joints that provide freedom around two axes at 90 º to each other, as in a universal joint, and are actuated by servos controlled by software developed with the aid of computer modelling and simulation. While evolution is limited in its capacity to innovate, because it can only work by natural selection, human engineers can add new features at will. That is evident in the Eelume snakebot. Eelume’s CTO Pal Liljeback had been researching biomimetics at the Norwegian University of Science and Technology (NTNU) and was initially looking to develop a land- based firefighting snakebot that would incorporate a water hose. However, he realised that adding thrusters along a snakebot’s body would also open up many potential applications under water. While it retains the flexibility, manoeuvrability and pose ability of the modular, segmented body, the thrusters allow the snakebot to travel further and faster than a conventional ROV or a pure snakebot. The thrusters are incorporated into dedicated modules, each of which has two external thrusters that pivot in pitch for forward and backward propulsion, and two lateral tunnel thrusters. Other modules contain batteries, sensors, tools and lights that can be combined in different ways to create multiple configurations, which Liljeback refers to as “snake Lego”. The body diameter is 20 cm, although the external thrusters add to that. Liljeback spun the Eelume company out of his NNTU work, and began working with Kongsberg (now the majority shareholder) and Norwegian national oil and gas company Equinor to develop the snakebot as a seabed- resident inspection, maintenance and intervention system. Initially the snakebot was remotely controlled using a series of cameras along its length, but an autonomous version is under development, building on research that Liljeback and colleagues have conducted into the complex, highly non-linear dynamics of snake control that nature perfected aeons ago – only now with additional human ingenuity. Now, here’s a thing “ ” April/May 2021 | Unmanned Systems Technology Evolution is limited in its capacity to innovate, because it can only work by natural selection, but human engineers can add new features at will