Extreme Design: Ultra-compact embedded computer overcomes multiple design challenges

By Thomas Roberts, Mercury Computer Systems, Inc.
Planet Analog (Sep 02, 2008)

New generations of defense imaging systems, using sophisticated sensor technologies, generate invaluable information for modern warfare. On large platforms, such as ships, planes, or ground vehicles, the systems use onboard integrated-computing engines that can immediately process sensor data, communicating useful images to users rather than streams of raw data.

In recent years, the trend has been to put many of the intelligence-gathering sensors on unmanned vehicles, and now the trend is to use increasingly smaller unmanned vehicles such as UAVs. One option is to relay the raw sensor data to ground stations for processing. However, to be truly effective, these smaller sensor-based systems must be supported by a new generation of signal processing computers--powerful, rugged, and ultra-compact. Mercury Computer Systems' PowerBlock 50 computer, Figure 1, was conceived as a way to meet this need, but the design challenges were significant.

Figure 1:The PowerBlock 50 computer was designed under some tight performance and environmental constraints

A small subset of the design goals helps to understand the scope of these challenges.

Weight of less than 10 lbs: A range of weights could have been targeted. However, there is a class of tactical unmanned aerial vehicles with a total payload capacity ranging from 60 to 200 lb (27 to 90 kg). In a general sense, it is reasonable to allocate up to half of that payload capacity to computing, but not much more.
Volume of less than one-half cubic foot: New generations of unmanned vehicles are not built to fit human dimensions. As with weight, a range of sizes could have been targeted. A one-half cubic foot system (15 cm³) will fit into many unmanned platforms. It is a volume target that current standard computer form factors are not able to meet.
Maximum processing power; no fewer than 100 GFLOPS: Imaging systems can certainly be implemented with less than 100 GFLOPS of processing power, but image-exploitation algorithms, such as change detection, geo-registration, or automatic target recognition, demand at least that level of processing.
High-speed, inter-processor communication infrastructure: In distributed-processing applications, the need for a deterministic high-speed inter-processor communications fabric is paramount. Such a communications infrastructure must be scalable for varying system configurations, support any-to-any simultaneous full-duplex data flow, and provide the performance and reliability defense applications demand.
Ability to function in extremely harsh environments: Despite their technical sophistication, defense electronics systems must deliver uncompromised performance under difficult environmental conditions, including excessive heat, humidity, poor air quality, high altitude, shock, and vibration. Embedded computers must be able to keep their electronics from overheating, even when temperatures range up to 55ý°C and the air is too thin to be used for cooling. At the same time, they must possess the enhanced mechanical integrity to withstand high-shock and vibration forces at various frequencies.

The PowerBlock 50 design team recognized that current form factors for defense and aerospace computing platforms (such as 6U or 3U) would neither meet the weight nor volume targets which this project set out to achieve. At the same time, to effectively address a variety of processing-intensive applications, the platform needed to be configurable to support multiple processing engines with diverse capabilities. Ultimately, a multi-slot ultra-compact chassis specification was developed that, at roughly 4" x 5" x 6" (10 x 13 x 15 cm), would adequately address the space-constraints of UAVs and other small platforms.

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