Feature: Avionics
Overcoming extreme design challenges DPI military- and industrial-grade Unmanned Multirotor Aerial Relay (UMAR) tethered drone is weatherproofed against rain, snow, dust and heat, and further fortified for saltwater marine environments. The system has been designed to withstand harsh temperatures, from zero to 120 degrees Fahrenheit. These drones are especially useful in that they can provide
400+ hours of non-stop uptime and operations, at altitudes to 500 feet, thanks to the continuous power supplied over the tether. Nevertheless, there are significant design challenges inherent to the tethered architecture. The power needs to be delivered from the host vessel to the drone at high voltage and low current, to allow for the thinnest and lightest possible tether, enabling greater drone mobility and larger airborne payloads. Operating at power levels of 8-10kW, the UMAR is
extremely powerful and rugged, essential when turbulent waters impact the host vessel. Therefore, the drone requires the power capacity and agility to accelerate rotor speeds to adjust and yaw in short or prolonged bursts as needed to maintain altitude and attitude – with instantaneous responsiveness. Inside the drone’s electronics, the high-voltage conversion
must be achieved in the smallest possible footprint and weight. The eight onboard independent rotors require sophisticated, interconnected circuitry, so any space savings at the power layer can be repurposed for other uses. Vicor power modules have reduced the weight of
components aboard the drone, allowing for higher altitudes whilst carrying heavier mission payloads. As an airborne antenna, the UMAR extends the ship’s radio
line-of-sight from eight to 30 miles; see Figure 5. Data transmitted and received by RF equipment mounted
on the tethered multirotor drone is relayed through the tether to the host vessel, allowing beyond-line-of- sight communication with surrounding vessels. This
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communications configuration presents EMI challenges for the power delivery architecture. Given the critical role these drones play in maritime defence and surveillance applications, the integrity of communications data is of crucial concern.
Drone power architecture For its drones, DPI used Vicor’s ultra high-voltage (UHV) BCM VIA modules, which offer efficiency of 98%, with only 2% losses in the conversion from 800V to 50V. Two sets of four UHV BCM4414 modules are co-located
within two waterproof aluminum enclosures and are board- mounted to the host PCBs in a setup that allows the low- profile, flat-sided UHV BCMs to be cooled from both sides. The compact footprint and mounting versatility of the UHV
Figure 4: Dragonfly UMAR drones can provide 400+ hours of non-stop uptime
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