Issue 45 | Uncrewed Systems Technology Aug/Sept 2022 Tidewie USV Tupan | Performance monitoring | Bayonet 350 | UAVs insight | Xponential 2022 | ULPower UL350i and UL350iHPS | Elroy Air Chaparral | Gimbals | Clogworks Dark Matter

53 Bayonet 350 | Digest engineered to be assembled in the field of operations without the need for tools. “All the boxes and structural parts connect or disconnect in about 15 minutes,” Hartman says. “That’s really useful for maintenance logistics, because if you break one piece you just grab a spare one and stick it in. “It also disassembles into a form factor small enough to fit in an SUV, or it can be carried in a bag upstairs or around tight corners, that sort of thing,” he adds. “The 350’s pontoons need two people to carry them, but that’s as difficult as it gets – the military pushed for that point especially hard, as they wanted the whole Bayonet system to be operated by as few people as possible.” Navigation In essence, the Bayonet 350 has much the same navigational systems and capabilities as an AUV. Fibre-optic gyros (FOGs) are used to minimise GNSS drift during extended periods underwater, and electronic compasses help further in this regard by enabling intermittent ‘resetting’ of heading and drift information. “Of course, we have no control over altitude – we’re restricted to driving across the seabed – but because we have a depth pressure sensor that’s accurate to 10 cm, and because we know where we are in terms of latitude and longitude, we can use the waypoint pre-programming system,” Hartman says. “We can tell the UGV quite easily where to survey, such as assigning it to a 2 km 2 area, and we don’t have to worry about commanding it to go to a specific depth.” Notably, if an end-user has access to a boat or pier and wants to save the UGV time and energy in navigating to its survey area, the company says it can be dropped into the water without being damaged when it hits the seafloor. However, driving from the beach into the waves is the recommended approach to launching it. While it’s above the water, the 350 localises itself using GNSS. The GNSS and IMU are packaged and integrated in the Greensea GS4 INS, which in addition to its FOG contains a MEMS accelerometer and supports fusion with forward-looking sonar data for functions such as SLAM or feature-based localisation. It can also use other sensors such as USBL and DVLs. “Theoretically, any navigation system could plug into our mission computer,” Farinella says. “If an end-user wanted something cheaper and didn’t care much about GNSS fidelity then we could swap something else in.” Heading fidelity usually stays within 2.0 º , which resets to a 0.25 º accuracy when the compass is used, and although the compass helps to reset heading information, it cannot help with positioning. For these, USBL and DVL systems have been fitted on the 350’s hull for acoustic-based positioning, as enabled through the GS4. Hartman adds that the OpenSea navigation algorithm allows sensor inputs to be prioritised. For instance, if the GNSS signal updates deteriorate below a certain threshold, the main computer can switch to basing its estimations using the DVL’s movement readings combined with the gyro and accelerometer. “The DVL we use is an OEM design, and we get good support from them,” Farinella explains. “We can in theory select any DVL, but our selection is limited by the fact that the crawler is going to mount the DVL looking down. “Technically, you could mount it looking up, to track the rate of movement Uncrewed Systems Technology | August/September 2022 Heavy COTS rubber tracks enable highly effective movement and station-keeping in a wide range of terrains, waves and currents