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

31 ANYbotics ANYmal D | Dossier automated systems in mind. Also, as it is based on Ethernet, it can be transmitted over shielded COTS Ethernet cables to prevent EMI issues. Similar Ethernet connections are used for unloading the live visual data from the onboard cameras to the main computer, with USB 3.0 connections selected for high-speed, high-bandwidth data connections as well as for the customer- end data output. The USB 2.0 protocol and USB Type-A and Type-C connectors are available as well, as are RS-232 and 485 for systems using serial comms. “On our PCBs we have devices communicating over everything from I2C to SPI buses, designed to adhere to EMI standards of course,” Dr Mauerer adds. “The shielding concept really has to be thought through from the ground up in a robot like this to make sure every sensor and cable shield is terminated properly to prevent EM emissions. “And of course we also have high- frequency coaxial cables running into the networking system from the antennas. As standard, we keep the ANYmal connected to the customer’s wi-fi over 2.4 or 5 GHz for live streaming of data, via a COTS antenna that supports both frequencies.” He notes that each antenna needs its own coaxial cable, and with each additional cable he and his colleagues must ensure that the potential risks of EMI, mechanical shock, vibration and tearing must all be accounted for; they also work with their EMI lab to ensure onboard radios and antennas do not interfere with each other. A close eye must also be kept on the collective ‘creep’ of cost, volume and weight that can build up incrementally with added devices, wires and connectors. ANYbotics also knows that some customers might want to integrate additional computation systems, such as a GPU or SoC for running further AI or computer vision functions, in addition to those already being run on the UGV’s second PC. Dr Mauerer says the I/Os, data bandwidth and power bus have been designed with that in mind. “We’ve worked hard to optimise our PCBs and cable harnesses to reduce the volume and weight taken up by all these comms, and keep the internal network as simple and coherent as possible,” he says. Power and energy systems ANYbotics does not, however, use Power-over-Ethernet, as this approach was judged as excessively prone to creating EMI. The easier method has been to use dedicated DC-DC converters where needed to power subsystems over low-voltage cables. “That might sound complex, but it gives you fine control over granularity,” Dr Mauerer explains. “That means you can power each sensor up or down individually, and they’re all designed with smart fuses, so if one sensor has an issue you can disconnect or power cycle just that one and keep running the mission.” The ANYmal D’s lithium-ion battery has been designed entirely in-house; it can store up to 907 Wh, and provides a 44 V nominal main power bus, which the ANYdrives connect to via their inverters. The onboard system of power electronics serves to ensure the drives can be powered down whenever necessary by including an emergency stop button atop the robot, which can be activated manually or using an additional back-up data link, as per CE requirements. A pair of DC-DC converters steps the 44 V input down to 12 V for the cameras and onboard computers, while the inspection payload’s servo actuators run directly off the battery bus. The drives also contain 5 V DC-DC converters for the embedded computers and sensors in them. All these power converters are described as small systems that need minimal thermal management. Forced convection cooling is used in the form of fans to directly cool the internal PCs and motor drives to keep them within the 40 C ambient Unmanned Systems Technology | October/November 2021 Although minimising the amount of cabling was a key engineering target, Power-over-Ethernet is not used as it would increase EM emissions – and reducing EMI was a critical requirement