Deploying ruggedized platforms for unmanned vehiclesStory
June 20, 2011
COTS-based technologies and associated thermal management wares are helping to arm modern UAVs/UASs with built-in harsh environment survivability and reliability, in addition to facilitating effective implementation of video and storage needs.
The evolution of Unmanned Aerial Vehicles and Systems (UAVs/UASs) for Intelligence, Surveillance, and Reconnaissance (ISR) has proven a fundamental game changer for the military. Capable of remote operation, these unmanned vehicles also present some of the most difficult design challenges. This is because of the need to package a high level of computing power and data collection/distribution elements within minimal Size, Weight, and Power (SWaP) constraints, while maintaining ruggedized capabilities to operate in very demanding environments.
Furthermore, the capabilities of UAVs have moved dramatically beyond their original “drones” purpose to now feature advanced onboard intelligence, capable of highly autonomous flight with the ability to make real-time mission adjustments. The complexities of these new UAV/UAS-based systems necessitate high-performance, high-bandwidth computing technologies that just add effective thermal management to the list of design challenges.
According to the unclassified USAF Flight Plan 2009-2047, “standards and interoperability are keys to the Joint Forces gaining informational superiority in today’s network-enabled environment.” As a result, UAV development goals mandate a common set of airframes based on standard interfaces and interoperable “plug and play” payloads. This mandate for interoperability calls for an open architecture COTS approach. However, the range of airframes deployed along with their accompanying ground command and control systems demands that designers develop a deep understanding of application- and system-level options.
New embedded computing COTS-based technologies and their associated thermal management solutions are helping to advance UAV/UAS design. Two considerations are paramount: building in harsh environment survivability and reliability and designing for video and storage needs. COTS-based options can help overcome developmental challenges to achieve tightly integrated systems that match the military’s unified network-enabled objectives and its ISR mission goals.
Technology drives enhanced UAV/UAS capabilities
One of the first important considerations in UAS/UAV development is evaluating the broad range of new platforms and system-level technologies that provides increased computing and communications capabilities and greater real-time operational control. UASs include ground stations and other elements besides the actual UAV aircraft, so embedded platforms must be able to support multiple tasks, as opposed to military designers having to develop multiple systems dedicated to separate tasks. As an example, UAS reconnaissance programs must include multiple functions such as vision systems, heat sensors, electromagnetic spectrum sensors, biological sensors, and chemical sensors.
Feature-packed, high-performance and high-bandwidth embedded computing solutions combined with high-density storage capacity can handle the computationally intensive demands of massive and ever-increasing amounts of sensor data. Military system designers are continually turning to proven, standards-based platforms such as Computer-on-Modules (COMs), CompactPCI, and VPX to reach their ISR interoperability program objectives. However, each must also be weighed for its ability to meet SWaP and thermal management requirements of the airframe and its mission.
For instance, smaller airframes with high performance requirements are ideal candidates for COMs-based solutions. There is a range of new Intel Core i7 processing-based COMs that offers increased processor efficiencies and delivers better signal integrity and increased performance for these space-constrained UAV designs. Providing a significant breakthrough for compute- and graphics-intensive imaging or surveillance UAV/UAS applications, these new COMs have improved data flow performance due to a new integrated chipset and advanced display interfaces.
Key UAV application requirements
Each defined airframe has specific requirements that will vary with its unique operational objectives; however, there are certain key requirements that are critical to successful deployment of embedded computing systems for ISR programs.
Harsh environment survivability and reliability
The benefits of new sophisticated features in UAVs in ISR applications will be eliminated if the system is not able to operate continuously and reliably within its target environment. The design approach that has proven most effective over time is to place the embedded computing technology in a chassis or enclosure manufactured to MIL-901D shock and MIL-167-1 vibration. That way, it can withstand specified vibration, shock, salt spray, sand, and chemical exposure in harsh environments.
Another rugged consideration is that a standardized COTS chassis can be adapted to meet specific cooling needs in mobile applications. Because of SWaP and environmental constraints, many UAV designers opt for conduction-cooling methodologies (with or without fan assist), but other methodologies are available. Accordingly, Table 1 gives a general set of guidelines indicating how many watts per inch of pitch are dissipated with each cooling method. But because each application has its own unique thermal equation, an important consideration is the ability to leverage pre-qualified MIL-E-5400 COTS platforms that can also be customized and tailored to fit specific airframe or program requirements.
Table 1: General guidelines for the approximate power dissipation of various cooling methodologies. Ambient temperature, altitude, generated power, and other environmental factors can create notable variations to these approximate values.
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The choice of cooling method is primarily driven by the total power dissipation; however, in airborne applications, ambient pressure is important because air density plays a major role in system thermal efficiencies of forced-air or passive convection-cooled enclosures. Liquid cooling is used only for situations that either operate at very high power levels or have no air or cold plates available. However, the increased system cost and lower overall MTBF of liquid-cooled systems are important considerations and need to be analyzed against simpler solutions.
Designing for video and storage needs
The sheer amount of visual content and other data routinely collected by UAVs would have been unthinkable just a few years ago. Plus, the demand for real-time remote monitoring as well as the integration of attack capabilities require a much higher level of computational performance. Besides collecting and storing data, onboard systems must be able to stream visual information in real time. Thus, the computational performance needed to support these massive data rates must be exceptional.
For these real-time imaging applications, VPX offers higher bandwidth processing using serial switched fabrics that enable significant improvements to subsystem application performance. VPX-based platforms offer higher-performance processing per slot and higher-speed interconnects between processing and I/O elements using PCI Express, 10 GbE, or Serial RapidIO. These interconnects provide 10 Gbps between elements or several hundred GBps in aggregate, depending on the system implementation. VPX also can be integrated with codecs such as ITU-T H.263, H.264 (MPEG-4 part 10), and JPEG2000 to provide very efficient image compression. Considering the variety and availability of COTS products, some applications might best be designed using more than one bus structure. For example, a CompactPCI switch can be used with a VPX-based board by utilizing a hybrid backplane.
Modular, high-density SSD-based storage subsystems are also being deployed to effectively handle large amounts of data and support quick-swap exchanges for rapid mission debriefing and/or mission turnaround – versus waiting to download the data through the I/O connection. It is important to note, however, that specific airframe configuration requirements might arise and necessitate a custom backplane design with I/O routing options. For example, the positioning within the system is critical for heat-generating VPX boards and power supplies to effectively manage the heat loading requirements, and might require a customized cooling solution or demand the chassis is cooled and mounted in a specific manner.
Finding the optimal COTS solution
Whether a designer integrates a COTS-based platform or uses one as the basis for a custom UAV/UAS design, both offer future scalability. More importantly, COTS technology advancements provided by COMs, CompactPCI, and VPX-based COTS platforms and the evolution of viable cooling methods and enclosures ensure that the expanded ruggedization, network-enabled, real-time imaging expectations for today’s UAV/UAS designs are ready to be deployed in ISR programs. An example of a COTS-leveraged platform suitable for UAS/UAV development is the module-based Kontron COBALT (Figure 1), which allows designers to scale computing performance from a 5 W Intel Atom processor-based COMs implementation to an Intel Core 2 Duo system at 25 W.
Figure 1: Designers can configure the COBALT for either 28 VDC or 115 VAC input power for compatibility with a broad range of UAV/UAS ISR applications.
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Reusing proven technology enables faster development and higher reliability, and facilitates greater design flexibility while continually feeding future design innovation.
David O’Mara is Product Manager, Conduction Cooled Products at Kontron. He has a diverse engineering background that includes extensive experience with military and aerospace electronics packaging, pressure and accelerometer sensor design, and high-pressure solid-state physics. David earned his Bachelor of Science degree in Physics from UCLA. Contact him at [email protected]
Kontron 858-677-0877 www.kontron.com