Design and Analysis of a Small Unmanned Aerial System (UAS) Power Distribution System

February 1, 2023

Army Research Laboratory, Aberdeen Proving Ground, MD

All electrically powered autonomous vehicles possess a system that distributes power to all the vital components of the vehicle. At the U.S. Army Combat Capabilities Development Command (DEVCOM) Army Research Laboratory (ARL), several projects are using unmanned aerial systems (UASs) as a vehicle platform. Some UAS being used are classified as group 1, meaning they weigh under 20 lb. The group 1 UASs that ARL conducts research with are very fast and agile quadrotors. Such quadrotors typically have four rotors and light payloads and can very quickly accelerate and effortlessly reach speeds over 100 kph. To do this, these quadrotors can draw upward of 400 A at 30 VDC in bursts. To meet those requirements, the motor/ propeller combination requires large amounts of power relative to the size of the UAS. Up until this point, ARL’s UASs have been using commercial off-the-shelf power distribution boards (PDBs) to meet the power distribution demands. A custom PDB would satisfy the DOD’s desire to source more UAS components domestically, as it would be designed and made in the U.S., which is unique for this type of UAS component.

This report considers all aspects of design of a PDB to include shape, size, components, cost, voltage regulators, peripherals, and so on. This report explores these issues in the context of a custom designed PDB needed for a specific ARL project, but can be used as a starting point for ARL engineers who are working on semiautonomous and fully autonomous vehicle projects. For the custom PDB to succeed, the board needs to perform just as well, if not better, than the current PDBs used on the UAS. The two PDBs this project currently uses are the following: Advanced Power Drives’ (APD’s) 500X (Fig. 1) and Matek Systems’ FCHUB-12S PDB (Fig. 2).

The manufacturer-claimed specifications of the APD 500X are the following:

• 4S–12S battery input

• 500-A continuous current

• 1000-A burst current

The manufacturer-claimed specifications of the Matek FCHUB-12S are the following:

• 3S–12S battery input

• 280-A continuous current

• 440-A burst current

Both designs use the standard M3 × 0.5 mm with 30.5- × 30.5-mm mounting holes,and they both have the ability to provide ESC telemetry, battery voltage readings,current readings, and 5-V and 12-V outputs.

To be a suitable replacement for either of these PDBs, the custom PDB must beable to do the following:

• Accept up to 6S batteries.

• Handle continuous current draw of over 500 A.

• Handle burst current draws over 1000 A.

• Provide ESC telemetry.

• Provide voltage and current readings from the PDB.

The program used to design and create the custom PDB is a free PCB/schematic application called KiCad. The main competitors to KiCad are Eagle and Altium. The reasons for using KiCad over the other two applications was because KiCad is compatible with the Windows, OSX, and Linux operating systems. Thus, projects can easily be transferred between workstations with little difficulty. The other reason is because KiCad is supported by popular electronics vendors, such as DigiKey and Mouser, which offer free KiCad models for components that one might plan to use in a design.

This work was performed by Darren R Webb for the Army Research Laboratory. For more information, download the Technical Support Package (free white paper) at mobilityengineeringtech.com/tsp under the Power category. ARL-9606.

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This Brief includes a Technical Support Package (TSP).

Design and Analysis of a Small Unmanned Aerial System (UAS) Power Distribution System

(reference ARL-9606) is currently available for download from the TSP library.

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