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Electronic Design

Embedded COTS UAV Subsystem Design Trends

The military’s rapid move toward network-centric, IP-based (intellectual property) architectures is driving a number of design considerations for current and next-generation embedded commercial off-the-shelf (COTS) subsystems deployed on unmanned aerial vehicles (UAVs). The push toward network-centric architectures is speeding the adoption of these platforms and of newer data communications interfaces such as Gigabit Ethernet (GE) and serial rapid IO (SRIO). There’s also growing discussion about migrating over to 10 GE in the future.

At the same time, practical budgetary reasons for supporting slower legacy interfaces such as 1553 on the protocol level to protect software application development investment encourages continued but transitional support of earlier, slower aerospace interface standards.

During this period of transition away from legacy interfaces, UAV system integrators have taken a “best of both worlds” approach by, for example, supporting the simulation of 1553 over GE and other highspeed interfaces. This encapsulation approach enables the system to utilize the entire 1553 structure and retain the software hooks that have already been built, tested, and qualified in flight applications.

In anticipation of future requirements related to network-centric architectures, next-generation UAV subsystems are being built today that incorporate the hardware piping that will support IP packetization in the upcoming future. This anticipatory step, essentially laying down high-speed “cables” while retaining support for application code written in legacy protocols, will ease the transition into adopting complete network-centric communications methodologies, including support for IPv6, when budgets allow and requirements demand the evolution.

As an example, Curtiss-Wright’s System Sensor Management Unit (SMU) subsystem deployed aboard the Global Hawk UAV provides a fully modern platform that can support GE and Fibre Channel links while interfacing with legacy interfaces such as 1553. In this way, the SMU works essentially as an interface fusion box, routing various interfaces and fusing them together.

The SMU’s aluminum chassis has also evolved, adding significant capacity for system expansion, as it has grown from the original (utilized in Global Hawk Block 20) 44-lb box to its current 75-lb size (planned for the BAMS Global Hawk). Helping to drive this evolution has been an increased demand for modularity and scalability.

UAV system integrators are being called on to enable both the scaling up and scaling down of particular subsystems as required by the mission. This trend has driven designs that enable system elements, such as solid-state hard drives, to be easily ejected to protect proprietary data in case of damage or threat to the aircraft. Subsystems for the BAMS variant of Global Hawk, for example, will likely include these features.

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