Unmanned Systems Technology 023 I Milrem Multiscope I Wireless charging I Logistics insight I InterGeo, CUAV London & USA show reports I VideoRay Defender I OS Engines GR400U-FI I Ultrabeam Hydrographic Ultra-2 I IMUs

Milrem Multiscope | Dossier components from blocks of raw material because that is expensive. Some Multiscope variants might have plastic or composite covers and fenders, he says, to reduce costs, while some military THeMIS variants will need armour, and the company is working with partners on that. Everything other than the metalwork is procured from outside Estonia. Once the right number of each component for the number of vehicles in a given production batch has been delivered, assembly is a matter of attaching them and the subsystems to the frames. Most of the components are line-replaceable units that can be exchanged in the field and, as the vehicle ages, upgraded using later versions, which one THeMIS customer is doing now, Jurgen says. “We build the vehicle in a way that makes it easy to maintain,” he says. “It’s very easy to remove the diesel generator, for example to change the oil. It’s also easy to clean, as it is watertight, so you can use a pressure washer on it. We are using as many off-the-shelf parts as possible so it will be easy to find replacements from the local car spares shop, for example, for regular maintenance of the diesel generator.” The generator’s oil-change interval is 200 hours. “You don’t need to maintain the electric motors; bearing lifetime is something like 20,000-30,000 hours,” Jurgen says. Some maintenance will be done by customers themselves after training from Milrem, while more complex tasks such as overhauling the generator will be carried out by certified field service representatives or third parties. Electrical power The main requirements for the propulsion system are derived from physical and mathematical models of the vehicle’s movement, explains power electronics engineer Rait Karri. “First we create physical models to evaluate how much power we need, how much thrust and torque we need to climb, descend, accelerate and run at constant speed and so on. Then we know the required power characteristics,” he says. This feeds into the selection of components and subsystems that can handle the driving profiles and environmental conditions the vehicle is likely to encounter. Then the engineers work out how high the ingress protection (IP), vibration and temperature ratings of key components need to be, taking into account factors including the location of the propulsion system. When power consumption is constant, for example, if the vehicle is required to drive at 10 kph for a given time, the drain from the battery is balanced by the charge from the diesel generator, Karri explains, as the average power consumption is known. If there