Issue 40 Unmanned Systems Technology October/November 2021 ANYbotics ANYmal D l AI systems focus l Aquatic Drones Phoenix 5 l Space vehicles insight l Sky Eye Rapier X-25 l FlyingBasket FB3 l GCS focus l AUVSI Xponential 2021

26 against shocks – from accidental falls or collisions that might mean having to recalibrate the sensors, for example – and is used around the joints to block any exposed spaces that people might trap their fingers in. A rollover bar is also installed over the Lidar so that if the robot should fall onto its back it is not damaged or torn off. Additional foam padding is installed on either side of the inspection payload. As a final layer of physical protection, an outer skin composed of a thermoplastic is vacuum-formed and mounted directly over all the foam and aluminium structures. The shell is not load-bearing, but serves to protect the foam and electronics from sharp edges. The thermoplastic and foam (as well as their shapes and thicknesses) have been selected to cover the anticipated load cases based on the maximum speed and acceleration of the robot and the environments it will be working in. “We analysed the foams extensively across many impact simulations, because the force-absorbing behaviour across environments is very important regarding the kind of foam we chose in the end,” Dr Mauerer explains. “For instance, some foams stop absorbing shocks at 0 or 50 C, but our robots have to work across a wide range of temperatures and seasons, and we don’t want them to lose their protection when walking near furnaces or inspecting outdoor areas during winter for example.” Fankhauser adds, “The robot is officially certified to operate continuously from 0 to 40 C without any derating of its power, but technically it can weather much higher or lower temperatures for short amounts of time without problems. We have test versions of it walking in circles inside thermal chambers to try to see how it’s going to break from heat, cold, humidity and other environmental effects, so that we can patch those weak points before they become a problem. “The ANYmal D is IP67-rated, but systems with that certification can still accumulate humidity inside their main body, meaning fluids will condense internally over time because they can’t physically escape if you don’t take the necessary precautions, “ he says. “That is the sort of thing you need to keep in mind if you want to claim your system is safe for industrial applications.” As perhaps the biggest test of their IP67 rating, the robots are often set to walking in circles inside a swimming pool, to test the limits and ensure the quality of their water ingress protection. A range of shock and vibration tests have also been run to certify that the ANYmal D can be used in harsh industrial environments. Early on, these consisted of dynamic FEA simulations for predicting where critical resonances might occur in the structure, and non- linear dynamics modelling of the springs and feet along with low- and high-cycle fatigue simulations. Extensive real-world cycling to test the fatigue of the robot and its parts was carried out for validation and verification testing. In addition to complying with industry standards, such as those used in the automotive world, many internal testing profiles for frequency ranges and amplitudes for shock and vibration had to be defined from scratch in order to accurately emulate what a quadrupedal robot might be subjected to over its recommended service life of 3 years. A test facility near ANYbotics’ headquarters that is typically used for investigating the ruggedness of satellites has been employed for its large shaker tables, through which the aforementioned profiles were run with the full robot standing atop them for 2-3 days at a time. The results from these tests allowed the team to identify points of weakness such as where resonances might change, where fasteners would come loose first, or how long the ANYdrives can last, given that they are subjected to the most stress from constantly walking around and bearing the weight of most of the system. In its own in-house testing facilities, ANYbotics runs continuous tests of the technology to find ways of improving future designs. Here can be found robotic legs hopping 24/7, simulating entire lifetimes of use as different loads and forces are applied to them to see how their subsystems interact, respond and age according to different forces. “Obtaining CE certification also meant putting in every form of protection we could think of against EMI across our cable harnesses, PCBs and connectors,” Dr Mauerer says. “There is an EM test lab October/November 2021 | Unmanned Systems Technology Each leg contains multiple ANYdrives, which consist of custom- designed and electric motors, motor controllers and springs