Uncrewed Systems Technology 049 - April/May 2023

36 vessel. In most cases, one computer is used by an operator for in-the-loop monitoring as well as command & control where necessary, and a second computer is used by an analyst for real- time scrutiny of payload data. The GCS software has been developed in-house, and can be separated into two interfaces. One is a pre-mission planning chart system that can be customised using interface configuration tools or importingmission plans prepared previously usingMAR’s software. The other is an in-mission live telemetry display UI, where parameters such as vehicle speed, GNSS quality, engine health and actuator diagnostics can be viewed. “Naturally you can also use the planning chart to change your mission’s waypoints or payload usage on the fly, and check live telemetry before launching the WAM-V to confirm the health and correct performance of all your subsystems, as well as seeing your camera, sonar and inertial data in real time,” Mehlman adds. GNSS To prevent excessive chatter from the control system affecting the performance of the payloads, and to maximise control system reliability, the payload is decoupled from the command & control and run on a separate computer. That means for instance that two GNSSs are usually installed on the WAM-V: one for the navigation system and the other for geostamping the payload data. Mehlman says, “We go with one large and powerful GNSS to get very precise data from the latter, and then for the main computer’s navigation functions we actually get away with using a smaller, more right-sized system.” The larger GNSS can also be used for navigation if more precision is required. This tends to be a POSMV from Trimble Applanix, chosen for its reliability although it will often be disengaged during transit to save energy. The smaller navigation system is from VectorNav, SWaP-optimised and ruggedised as it is for various defence and industrial tasks. “We have also performed missions where the smaller VectorNav GNSS-IMU provided readings for both navigation and sensor referencing,” Mehlman says. “We try to be flexible, so we’ve used navigation systems that are serial-based, Ethernet-based, the list goes on; there’s no real limit.” Power Unlike the 16 and 8 versions, which are fully electric, the WAM-V 22 is typically fuel-powered. As indicated, the propulsion system is as modular as the rest of the craft: MAR uses Torqeedo gasoline outboards on the WAM-V 8 and 16, while systems from Honda and Suzuki have been used on the WAM-V 22. The target is for two 20 or 30 bhp thrusters – one for each pontoon – integrated at the back of the USV. “The computer system itself is agnostic. No matter the thruster pod, it’s running the same comms protocol,” Mehlman says. “On the 22, we tend to install the fuel tank on the skis, its size depending on the size of the payload. The USV has a flotation budget, so if you want to carry say a heavy April/May 2023 | Uncrewed Systems Technology The GCS software can be separated into a pre-mission planning chart system and an in-mission live telemetry display interface The standard propulsion arrangement on the WAM-V 22 is two gasoline outboards, typically from Honda or Suzuki and rated to 20 or 30 bhp