Test Standardization and Interoperability

By Charlotte Adams | August 1, 2002
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In an effort to decrease the cost and increase the efficiency of automatic test systems (ATS), the military services are pushing for a greater level of standardization, not just within one service branch, but across these traditional boundaries. The emphasis also is shifting from hardware to software standards. The U.S. Navy’s ATS family, known as the Consolidated Automated Support System (CASS), also is adding parallel analog test capability to reduce test runtimes.

The Navy, which in 1994 was assigned the role of U.S. Department of Defense (DoD) Executive Agent for ATS, is coordinating the effort to further standardize and consolidate test equipment and get beyond unique hardware/software dependencies. The vision–still a long way from implementation–is to enable test program sets (TPS), the software that runs automatic test equipment (ATE), to operate on Air Force, Army and Navy testers. Test software programs now are written for the specific hardware environments on which they will run.

The interoperability problem became more evident during the Gulf War, explains Bill Ross, assistant director of the DoD Executive Agent Office (EAO) for ATS, at the Naval Air Systems Command (Navair), NAS Patuxent River, Md. In one case, F-16 maintenance personnel in Saudi Arabia contacted their surface Navy counterparts to ask whether the Navy could run an F-16 TPS on Navy ATE. "The answer was ‘no,’" he recalls. So the services are exploring commercial software technologies, such as the Extensible Markup Language (XML), to make TPS transportability a reality.

The Joint Strike Fighter (JSF) would be a perfect application for the TPS transportability concept. The airplane will be purchased by the U.S. Air Force, Navy and Marine Corps, as well as by international forces. It would make sense to develop one TPS for a radar box and be able to run it on multiple testers.

Synthetic instruments–specialized functions created by software from more general-purpose components–also are getting a hard look, as they could drive dramatic cost and space reductions. "We believe, with some of the A-to-D [analog-to-digital converters] and D-to-A [digital-to-analog converters] and fast processors, we can generate instruments synthetically," Ross says. He thinks it may be possible to reduce individual ATE system size by as much as two-thirds, resulting in "tremendous operational and support cost savings."

Boeing has a contract with the Navy under an R&D initiative funded by Navy and the Office of the Secretary of Defense (OSD), called Synthetic Instruments for DoD ATS (SIDA). The company will develop virtual, or synthetic, instrumentation kits to replace selected standard instruments-on-a-card, initially for large-format, "mainframe CASS" and the smaller-format, Reconfigurable Transportable CASS (RTCASS). Then the design would be applied to other Army, Marine Corps and possibly Air Force ATE.

Testing Policy

DoD ATE policy emphasizes the cross-service picture: a test equipment architecture, or set of standards, to reduce infrastructure costs and increase interoperability.

The move toward standards began more than 30 years ago, with the development of the first ATS equipment families. Use of standard ATS families was officially mandated in mid-1990s acquisition rules. Even now, however, major families such as CASS and the Army’s Integrated Family of Test Equipment (IFTE) cannot claim to cover all of their respective services’ aircraft types. The Air Force has numerous unique testers, as well.

The focus now is on "trying to evolve to a standard architecture, rather than specifying [which] hardware to use," Ross says. This architecture, in the works since the mid-’90s and still far from complete, comprises a "list of critical interfaces defined by standards that we will all live by."

So far, 24 critical interfaces, out of the hundreds that exist, have been defined. Seven of the 24 have been realized by commercial standards that are now mandated, such as the Internet protocol (TCP/IP) and assorted VXI Plug and Play (VPP) software specs.

"We’ve captured the VPP standards, but we’re not necessarily requiring the use of VXI hardware as the standard format," Ross says. "We’re trying to standardize at the software interface level. We want the VPP standards, but you still can use VME, VXI–any backplane–as long as you comply with specified VPP driver standards." The point is to be able to swap out an obsolete instrument for a replacement with minimal impact to the legacy TPS. VPP is not tailored to any specific hardware, he says.

EAO also is considering Interchangeable Virtual Instruments (IVI) specs, which address a software layer above the instrument drivers, Ross says. "We’re trying to control the interfaces at a level where the instruments below it don’t make any difference." EAO does not expect the services to replace legacy testers with new equipment. Standards like TCP/IP have been used for some time.

Use of TCP/IP in ATE is a natural migration, Ross says. Besides application in internal test system communications, the Internet protocol can be used to communicate externally to a remote test station. Likewise, reliability data–what failed and when it failed–could be captured through the protocol and uploaded to a master maintenance history database. The Navy in August 2002 was integrating and troubleshooting such a database application and hoped to complete the interface this summer or fall.

New equipment will be expected to meet mandated standards. But existing equipment will "evolve into this architecture, where it’s practical," Ross says. The blueprint is described in a mandated policy document called the Joint Technical Architecture.

Test Hardware

The military services have been migrating toward modular instruments-on-a-card for many years. This type of equipment is typically PC-controlled and uses hardware formats and backplanes common in the commercial test world.

The Navy plans to field RTCASS, a partly VXI-based system, developed for the Special Operations Command (SOCOM) and the Marine Corps. RTCASS probably will comprise nine man-transportable cases–five of them VXI card cages–as well as some non-VXI, bench-mounted instruments. The Navy plans to buy five RTCASS systems sole source from Lockheed Martin and then open the acquisition of an additional 135 systems to a competitive process next year.

New technology also is emerging. The Navy, for example, is inserting "multi-analog" test capability, developed by Teradyne with the Navy and Boeing, into CASS and RTCASS. Because of the limitations of existing CASS stimulus and measurement instruments, these tests had to be conducted sequentially, with one stimulus and then one measurement–a slow process.

The Teradyne Ai-7’s first application will be the Navy’s Intermediate Avionics Test Set (IATS) family, a functional tester for the F/A-18. (CASS is replacing IATS, which already employs some parallel test capability.) The fleet wanted to have CASS runtimes that were at least equivalent to what it has experienced with IATS, Ross says. Although a CASS solution without multi-analog capability would have run 22 percent slower than before, parallel test technology will make it run 11 percent faster.

The Teradyne product will be used mostly to test electromechanical interfaces on systems such as flight recorders, engine controls and flight control systems, according to the company. The cards, in low-rate initial production, now are being used for TPS development. The Army also intends to install the capability into its IFTE system and the Air Force intends to demonstrate the approach on two F-15 testers, says Ross. The C-sized VXI card has 32 independent channels, with six independent instruments per channel, says Andy Hutchinson, marketing manager for Teradyne’s military business unit. The Navy will use a three-card set, yielding the equivalent of 576 independent instruments, the company asserts. Wherever possible, analog inputs are converted to digital logic and measurements are performed digitally, leveraging digital processing density and speed.

The Ai-7 also has synthetic instrument capabilities, allowing the creation of specialized functions not typically implemented in the various instruments, Teradyne says. The digitizer and arbitrary waveform generator, for example, can be put together to form a bidirectional digital test channel for mixed-signal applications.

Additional customers for the Teradyne hardware include BAE Systems for the F-22, Raytheon for missile programs, and Boeing for satellite applications, Hutchinson says. The instrument types provided on the cards are: function generator, arbitrary waveform generator, digitizer, digital multimeter, counter-timer and peak detector.

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