Uncrewed Systems Technology 044 l Xer Technolgies X12 and X8 l Lidar sensors l Stan UGV l USVs insight l AUVSI Xponential 2022 l Cobra Aero A99H l Accession Class USV l Connectors I Oceanology International 2022

54 Digest | Stanley Robotics Stan UGV Comms and fleet management In addition to the RTK base stations, Stanley Robotics typically installs a server to interface with the end-user’s IT network, along with some wi-fi relays to ensure the on-site Stans can in turn interface with the latter. Surveys are conducted before each installation to ensure the appropriate placement of server and relay antennas amid the layouts of buildings and other potential disruptions that airports and other transport hubs can pose. That said, most customers’ car parks are largely open areas, so objects blocking or reflecting RF signals tend to be rare. “That end-to-end interfacing ensures that key business data is recorded for the end-user, such as in-and-out timings of their customers’ vehicle bookings,” Trouble says. “Our choice of wi-fi modems and relays, from Acksys, means that even if the end-user’s IT network drops out momentarily, the Stans are still connected to our server, so they can keep operating. We might just refresh the orders and requests from the end-user to the robots after their network comes back up. “That said, if the wi-fi link to a Stan cuts out, the robot itself will stop immediately, for safety’s sake. The loss of RTK corrections alone is enough to trigger an emergency stop.” When a request for an autonomous valet comes in from the parking lot, the order is transmitted through the on-site IT network to the fleet management server, which then assesses which Stans are available and suitable for fetching the car in question. All the data links are encrypted through AES-256 over SSL, while the exact frequency depends on local regulations. For EU customers for example, Stanley technicians have to install a 5 GHz link, while for Japanese customers, 2.4 GHz links have to be used. With localisation data being constantly assimilated by the fleet management software, appropriate waypoints and trajectories are calculated to optimise tasks and routes. The software arbitrates which UGVs should go for recharging, which should go to pick up a parked car, and which routes should be taken to drop off cars at appropriate spaces and prevent traffic. Driving and braking To execute the navigation orders received from the fleet management system, two asynchronous electric motors are installed: one for steering and one for traction. The traction motor is capable of up to 3.6 kW of power, while the much smaller steering motor outputs up to 800 W. A single-speed gearing system with a 17:1 reduction ratio is integrated between the wheels and each side of the traction motor. Traction power is delivered and adjusted by an inverter from Curtis Instruments, selected for the levels of high power throughput critical for energy-efficient acceleration as well as regenerative braking. Energy comes from a 48 V battery composed of two packs, which together contain close to 20 kWh of energy when fully charged. It is supplied by E4V, which notably uses lithium iron phosphate (LiFePo 4 ) cathodes in its cells, as it says they are very stable in terms of raw material prices and operational safety compared with other options. It also says they last far longer and are safer than NMC cells, albeit with a lower specific energy. “The availability of our fleets is not primarily constrained by the UGVs’ battery energy divided by power consumption, because we can do opportunity charging all day long, sending them to recharge depending on the workload,” Trouble says. June/July 2022 | Uncrewed Systems Technology Ultrasonic and contact sensors about the platform help guide it between each car’s tyres for a secure hold GNSS information is combined with SLAM models and wheel odometry in real time on board the main PC to navigate car parks safely