Uncrewed Systems Technology 046

110 Digest | IM Solutions Monodrone IM 3000 Mk2 feedback on the Mk1, and we took that into account when designing the Mk2. The first version was a semi-rigid vessel with an outboard motor, and lacked a winch for SVS or CTD sensors; battery charging was tricky as well,” he says. “The Mk2 is completely waterproof and includes an onboard charger, so there is no need to open a hatch and therefore no risk of water ingress during charging. That is particularly useful during charging on the survey vessel’s deck.” Mounting the motors inboard allowed IM Solutions to put a winch at the stern, along with a new aluminium A-frame, to ease deployment and recovery of cable-mounted sensors. “We also fitted ruggedised fenders that allow it to stand up to harsh contact or rough handling, so the Mk2 version is designed for real-world survey operations.” The hull structure is moulded from glass fibre-reinforced plastic (GRP), while the fenders are made from tough closed- cell foam and the mast from inox (French for stainless steel). For the electric powertrain, IM Solutions chose a single solution including batteries, power management, motors and propellers from Torqeedo, Manigot says, citing their reliability and ease of integration. With a boat that has to work well in shallow inshore waters as well as the open sea, hull design was one of the key challenges, he explains, because both stability and manoeuvrability are crucial and conflict with one another. “For open water work, having a stable platform – particularly in heave – is very important for data quality. The IM 3000 has excellent sea-keeping capabilities thanks to its length-to-width ratio.” Manoeuvrability is the most crucial aspect of shallow water operations, so in these environments USVs have to be able to avoid beaching and to complete surveys in confined areas. One of the keys to this is the pair of independently controllable electric motors, he says. The motors are housed in pods, and drive high-efficiency, fixed-pitch, three-blade propellers through planetary gearsets. The launch of the Mk2 in March this year followed a trials programme, and the vehicle went into commercial service in the summer. Since then it has been working mainly in debris and bathymetric survey missions, using Norbit, EdgeTech and Kongsberg sensors. Multiple sensor options The vessel displayed at Oceanology International was fitted with an EdgeTech 6205 S2 wide-swathe bathymetry and dual-frequency sidescan sonar. EdgeTech says the 6205 S2 overcomes the limitations of MBES and interferometric sensors in shallow water through the use of the company’s multi- phase echo sounder (MPES) technology. IM Solutions describes MPES as a hybrid approach that uses multiple receive arrays and combines beam-forming and phase-differencing techniques in each sounding. That, it says, results in a clean 200 º swathe as well as faster and safer surveys. It also uses EdgeTech’s version of compressed high-intensity radiated pulse technology that transmits pulses which change in frequency with time, exploiting the returns from multiple frequencies within the pulse to generate more October/November 2022 | Uncrewed Systems Technology The USV’s stainless steel mast supports a variety of cameras, navigation and comms sensors, lights and two emergency stop buttons (Courtesy IM Solutions/Christophe Le Potier)