Issue 39 Unmanned Systems Technology August/September 2021 Maritime Robotics Mariner l Simulation tools focus l MRS MR-10 and MR-20 l UAVs insight l HFE International GenPod l Exotec Skypod l Autopilots focus l Aquaai Mazu

74 In operation | Exotec Skypod U3DV increase retail e-commerce that much,” Lueg points out. “On top of that, it’s getting harder to find logistics workers, either because of lockdowns or the fact that it’s not seen as the most rewarding work.” System and infrastructure The Skypod robot forms the heart of Exotec’s solution, so its engineering is of paramount importance to the company, to the point that every new Exotec employee is expected to assemble one, to prove at least a baseline knowledge of the robot’s anatomy. This is made easier through the Skypod’s modular architecture. The square-shaped robot is effectively composed of several modules, corresponding to the CPU, battery, propulsion, sense & avoid, localisation and enclosure. These plug directly into each other via connectors, without the need for wiring harnesses that might shake loose in time. Movement along a warehouse floor is achieved via four wheels, each located at the middle of the robot’s four sides (rather than at the corners). It traverses horizontally at speeds of up to 4 m/s (14.4 kph), which is relatively high for such vehicles. Traction and turning are provided by a single, centrally mounted electric motor that engages with the two side wheels via a differential gearbox, which adjusts automatically to switch between linear and rotational motion. “The reason we place the wheels in this unusual configuration is to prevent the robot tilting at an angle when going round corners. A car for example will tilt onto two wheels when cornering with enough force, but we don’t want our robots to lose control or cause any spillage or shaking of goods they’re carrying. The bins used to carry goods fit tightly into a tray built into the top of each Skypod. When the robot is moving, pins extend upwards from the tray and engage with the bin to hold it in place; the maximum carrying capacity per robot is 30 kg. “The floor of any warehouse using our system will be completely clear of people, as the area where the robots operate in is fenced off, unlike the mixture of robots and humans on the floors of Amazon’s fulfilment centres,” Lueg says. “As a result, we get better worker safety, and it gives the Skypods much more freedom to move as fast and efficiently as they can.” Onboard navigation systems consist largely of IMUs for dead reckoning, with path-planning and guidance commands performed via edge computing and transmitted to the robots over wi-fi. No rails, tape or stickers are used anywhere on the floor. “The path-following isn’t pinpoint- accurate; there’s maybe plus or minus a few millimetres while in transit, but for obstacle avoidance and fitting into the narrow spaces between the racks, each Skypod has a Lidar on its front to see rack corners and objects ahead with 1 cm accuracy,” Lueg says. “We’ve written its onboard navigation algorithm to get it to focus on staying in the middle of an aisle: it measures the approximate distance between itself and the racks on its left and right sides, and adjusts its movement as needed to keep the two distances roughly equal to each other. Doing it this way rather than relying on rails or tapes saves the end-user so many headaches in terms of having to perfectly place and maintain the position of floor-based guidance components. “Some new customers ask us where the 30-page guidebook on floor requirements is, because that’s what often comes with conventional GTP- based systems. With Skypod, you just clean the floor occasionally to prevent accidents and that’s it.” Each Skypod is engineered with a system of proprietary machinery for securely climbing the racks, and it’s driven by a series of electric motors. They work independently of the floor wheels’ propulsion system and each other. Preparing a warehouse When configuring a client’s warehouse for the system, Exotec needs a few key details. First is the maximum useable ceiling height, to ensure efficient use of all dimensions of space inside the building, followed by horizontal dimensions. August/September 2021 | Unmanned Systems Technology As GNSS is unavailable indoors, the Skypods use their front Lidars to count pins and rack struts to localise themselves and avoid collisions