34 conditions are avoided. The battery is a 4s pack, much like typical UAV packs with 16 Ah of capacity, which supplies power at 14.8 V and recharges over two hours. “We can operate up to three hours on that 16 A of energy, much of which comes from optimising our powerdistribution system. It helps that the uOne is neutrally buoyant, so we’re not constantly using power to actively push it down or up when we just need it stationary,” Garcia adds. Future improvements to the BMS will enable recharging of the battery without removing it from the AUV, although battery swapping is expected to remain a popular option with users, as each swap takes around 10 minutes (divers, by comparison, need 30 minutes above water to physically recover between dives). “One survey day, we used a uOne to map a hectare of seafloor, and that took three trips with two battery swaps; hence, only 20 minutes of downtime for 10,000 m2 of real photogrammetric data, which was beyond where humans or ROVs could go alone,” Arteaga notes. Data links The RPI4 communicates with the acoustic modem via UART; the latter broadcasting high-level operations telemetry via binary frequency shift keying (BFSK) and receiving commands if necessary, also via the BFSK protocol. “That’s a very basic protocol, sending 0s and 1s, but we’ve designed the acoustic modem to be built on top of that to improve on basic BFSK little by little, with advanced algorithms for features like noise reduction, error correction, multipath mitigation and increased bandwidth, which the modem will embed in its dedicated computer for receiving and formatting information,” Garcia says. Similar in nature to a radio modem, the acoustic modem uses an analogueto-digital converter, along with an arrangement of filters and amplifiers to retrieve signals received by the acoustic transducer and deconstruct them into digital signals to be interpreted and used by the main computer via UART. “We don’t depend on constant acoustic communication between the AUV and user – it’s really just there to ease the user’s mind. If they’ve never worked with AUVs before, it can really stress them to just sit there for two hours not knowing if the robot is still operating properly,” Arteaga says. “Instead, every 30 seconds they get an update, basically reporting all systems are working okay and a very brief summary of what the robot is doing; and if something like a subsystem goes wrong or an underwater object is missing or really damaged, we want the user to be alerted immediately via a short message.” Hence the acoustic modem enables an uplink for persistently streaming small packets of rudimentary but lengthy information, as well as a downlink for very short, one-off command packets from the user (so the user’s choice of ground-control station (GCS) must have a transducer and acoustic modem connected). The comms algorithms include error-correction subroutines and encoding protocols for outgoing messages to compress the information as much as possible for further comms efficiency. “It’s an open channel, so the AUV is constantly listening – no excessive energy consumed to do so – and when specific commands from the user are received, saying maybe, ‘give me a full status update’ or ‘change your action’, the onboard modem and computer both execute the command, and answer back an acknowledgement,” Arteaga says. Shore and cloud Persistent mission monitoring is enabled via an IP68-rated topside computer offered by uWare, which links to a modem and a transducer in the water. It can stream mission and vehicle information to the user’s device via 2.4 GHz or 5 GHz wi-fi. Or it can come with a screen, keyboard and mouse if the user would rather use that computer as a GCS. As well as receiving the aforementioned updates, users can plan and monitor the mission via a GUI running locally on their device, although uWare notes that its topside computer is small enough that some missions have been launched and concluded offshore from paddleboards (eliminating the need for even a small boat). The front end of the GUI closely resembles UAV planning software, with top-down GNSS map views for creating survey routes and geofences, including heights above seafloor, approximate depths, spacings and orientations, with inbuilt wizards that make recommendations on such parameters to the user before the plan is uploaded to the uOne. Once the mission plan is uploaded, the user receives estimates of the mission length and battery energy consumption, and potential alerts of how far the uOne will February/March 2024 | Uncrewed Systems Technology As uWare enhances the uOne’s intelligence, it will be increasingly capable of taking on duties that could traditionally only be entrusted to human divers
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