Latest Technology Advances UAV Design

<b>COTS-based Mission Computer Speeds Development</b>

By Dave Garcia April 2004 COTS-based mission computer for Unmanned aerial vehicles (UAVs), offer clear advantages over manned aircraft, one being safety as take-off and landing are usually remote controlled. And once they are airborne, UAVs can stay aloft for days or weeks on end, following a predetermined path and guided by global positioning system (GPS) satellites. More robust UAVs can cruise at heights considered too low for manned craft. And with no lives at risk, UAVs can enter extreme environments. UAVs range in size from handheld to runway-operated aircraft whose payload capabilities range from a few pounds to 2000 lb. The Department of Defense (DOD) built up its arsenal of UAVs in the late 1980s and ’90s in close-range (50 km), short-range(200 km), and endurance categories (beyond 200 km). The close- and short-range categories have since been combined, and later, a shipboard category was defined. Close and short-range vehicles are now classified as tactical UAVs, which include 50- to 1000-lb deployable air vehicles, followed by the endurance category, which is capable of extended duration flights, typically 24 hours or greater. Other UAVs include: 1.) Vertical takeoff & landing (VTOL) versions, which are typically rotary wing, 2.) Man-portable, which is light enough to be backpacked by an individual and launched by a handthrowing or sling-shot mechanism, but larger than micro air vehicles, 3.) Optionally-piloted vehicle, which is capable of manned or unmanned flight operations and typically an adaptation of a general aviation aircraft, and 4.) Micro air vehicle, which is defined as having no dimension larger than 150 mm. One high-profile UAV is the General Atomics Predator, which has served the U.S. in Kosovo and Afghanistan. Another example is the Northrop Grumman Global Hawk, a high-altitude, long-endurance UAV reconnaissance system that provides military field commanders with high-resolution, near-real-time imagery of large geographic areas. A third example is the U.S. Navy’s VTOL Fire Scout, which enables real-time data sharing from ships or land-based control segments, reducing engagement timelines and minimizing exposure to enemy threats. UAVs are getting smaller and lighter, and they need to fly further and further away from the command center. On top of this, the demand for UAVs is increasing. Because time-to-market is so important, the military has begun to purchase basic commercial-off-the-shelf (COTS) systems and adapt the configurations to meet application specific requirements. This process makes good sense, as many UAVs require very similar computing platforms and highspeed I/O. A COTS-based approach facilitates a move away from legacy systems toward newer technologies that transmit and receive data much faster, are more powerful, take up less space, and weigh less. For example, a quad-redundant system, based on a legacy 6U VME bus, would require computers with a mass of 40 lb each, for a total of 160 lb. A version based on a 3U cPCI system can have a mass of as little as 9.6 lb and would require 50% less power and half the space. And because the system is based on COTS, it can be delivered to the market in half the time for much less money. Basic systems that include a single board computer (SBC), data bus, analog and discrete I/O, power supply, and ample spares to accommodate growth are a prime solution for UAVs. SBS Technologies offers the Advanced Vehicle Computer (AMC-cPCI 3000 Series), which consists of three compartments: one for the CompactPCI card slots, the second for the power supply, and the third containing the external I/O connections. It is based on a 3U cPCI COTS computing platform and comes with a 500-MHz PowerPCbased CM4 SBC, and proven real-time operating systems such as Wind River’s VxWorks and Green Hills’ Integrity. It easily integrates with other CompactPCI and PMC modules. The key to making COTS work for the military is building systems around open-standard interfaces to allow developers to capitalize on technology insertion—that is, to upgrade individual modules while maintaining backplane compatibility. That way, military designers get reduced nonrecurring engineering costs at the initial design phase. The technology insertion can usually be done without paying for the design of new modules as long as the module and associated software adhere to industry-standard bus interfaces, form factors, operating systems, and application programming interfaces. This approach enables system upgrades and performance increases without reengineering. To deal with exposure to harsh and unfriendly environments, military COTS vendors offer ruggedization versions of commercial products. They also take care to understand the thermal and mechanical characteristics of their boards. Other ways to make the system rugged include routing external I/O signals through the backplane to the printed circuit board interconnect and the D38999 series front panel connectors. For cooling, the COTS mission computer system removes heat primarily through thermal conduction. By careful component selection, placement, and thermal conductivity between the CompactPCI modules and the chassis, the system can operate at temperatures up to 85°C. Designers can use a mission computer such as the AMC-cPCI 3000 Series as a starting point for UAV development, adding a graphics board, discrete I/O, or high-speed serial interfaces as required. SBS’s engineering development unit enables software developers to write code before the ruggedized version is completed, reducing overall development time and speeding time-to-market. Integration services ranging from shock, vibration, thermal modeling and analysis, board level integration, software development, and qualification are also available to speed the development process. Dave Garcia is a Program Manager for SBS Technologies,Inc., Albuquerque, NM.