Historically, the price of non-commercial hardware has been astronomical due to the engineering required for it to perform specific functions and to operate reliably in harsh conditions, with ambient temperatures from -55° to +125°C, in high and low humidity, while withstanding extreme vibration and shock. It became apparent that if commercially available components, boards, and systems could be adapted, larger suppliers could benefit from both the advanced technology and the economies of scale enjoyed by commercial industries.
Using commercial off-the-shelf (COTS) technology in harsh environments is not a simple task, but a building-block approach to COTS can make it easier. Suppliers buy a basic COTS system and then adapt the configuration to meet application-specific requirements. A typical building-block COTS system would include a chassis based on standard bus architecture such as VME or CompactPCI (cPCI), a single-board computer (SBC), data bus interface, and one of a number of real-time operating systems (RTOS).
A cPCI COTS-based system would integrate easily with other cPCI and PCI mezzanine cards (PMC), and would contain spare cPCI card slots, a power supply, and connections for external I/O. Designers can use such a system as a starting point, adding a graphics board, discrete I/O, networking, or high-speed serial interfaces to enable the system to become, for example, a mission computer, a display processor, or the underpinnings of an aircraft communications system.
Using readily available COTS modules from a competitive marketplace helps developers build systems that meet application requirements at substantially reduced costs. System designers can choose from a wide variety of SBC and I/O interfaces from an ever-widening selection of vendors. Adding functionality to a COTS system can often be done without paying for the design of new modules as long as the module and associated software conform to industry standard bus interfaces, form factors, operating systems, and application programming interfaces (APIs).
In addition, by using cards based on open standards, designers get reduced non-recurring engineering (NRE) costs at the initial design phase. When the time comes for technology insertion or refreshment, NRE costs are significantly lower than they would be if proprietary hardware interfaces were used. Often, this approach enables system upgrades and performance increases without re-engineering.
Several COTS vendors design boards as commercial products and offer a ruggedization option for the harsh environments found in military applications. To make a system rugged and increase reliability, various features are utilized in the system such as wedgelocks to securely hold the module in the card slot, stiffeners to allow them to be used in high-vibration environments, and the use of a PC board to route external I/O signals from the backplane to the D38999 series front panel connectors.
Experienced COTS vendors also take care to understand the thermal and mechanical characteristics of their boards. Cooling is often accomplished through thermal conduction. This cooling method transfers heat from the components to the PCB, from the PCB through the wedgelocks to the chassis, and from the chassis to the ambient atmosphere through the use of heat-radiating surfaces. By carefully selecting components, optimizing component placement and mounting, and providing thermal conductivity between the modules and the chassis, a well-engineered, rugged COTS system can operate at temperatures of up to +85°C.
Today, COTS products can be utilized in systems that meet the stringent requirements for rugged applications. By using a building-block approach, contractors can purchase a basic COTS system and adapt it to meet application requirements, saving time and money.
This article was contributed by William C. Ripley, Director of Business Development for SBS Technologies' Government Group. For more information, contact Mr. Ripley at 505-875-0600, ext. 845; fax: 505-875-0400; or e-mail: