Designing automatic test systems for extended duty

Developing a modular abstraction layer
While IVI provides a layer of TPS protection for the listed instruments, test stations nearly always include additional instrument types and other test assets. These other station elements also become obsolete or may need to be replaced in order to provide new capability as the ATS workload changes. Another key element in ATS design is thus the development of a comprehensive, modular abstraction layer that encompasses all of the current test station assets and is also open for further development when required later in the ATS program.

Another useful abstraction to incorporate into a system’s design is the use of modular subsystems such as synthetic instrumentation. A synthetic instrument is defined as a reconfigurable system that ties together a series of elemental software and hardware components, with standardized interfaces, for the purpose of generating signals or performing measurements using numeric processing techniques—a modular, software-defined instrument.³ This is another powerful tool for addressing the typical mismatch between instrumentation lifecycles and test system lifespans (see figure 2).

Because these instruments are software-defined, integrating them into a system will typically lead to greater cost savings and greater system flexibility because each synthetic instrument:

• Replaces multiple traditional instruments
• Can emulate obsolete instruments
• Can be more easily upgraded to address new requirements
• Is more readily customizable to specific test needs

Testing over multiple generations of electronics
The past experiences of support organizations have proven how expensive it is to operate unique testers for the maintenance of different subsystems or even for separate weapons platforms. As a result, the trend is to consolidate to common support equipment whenever possible. Although this approach can reduce cost, it also presents additional challenges to providing ATS solutions.

Combined with the forces of platform life extension, consolidation significantly increases the range of electronics technologies that platform support ATSs must be capable of testing. This creates an extremely high-mix test application environment compared to most commercial counterparts. The additional complexity and greater number of UUTs tend to increase the frequency of obsolescence events. They also heighten the impact that these obsolescence events have on the ATS programs and the missions they support. Here again, modular instrumentation platforms, abstraction layers, and software-defined instrumentation prove to be invaluable design elements, yielding differentiating capabilities for ATSs that integrate them.

In this high-mix test environment defense, maintenance organizations require ATE to support a dual role of sustaining a large number of legacy TPSs and enabling development of new ones. To leverage money already invested, an ATS must operate existing TSPs. Simultaneously, it must provide capability for efficiently developing and operating TPSs for the emerging technology UUTs and incrementally evolving supported systems. All of these devices must be tested and maintained so that their systems meet mission requirements.

Flexible, cost-effective solutions include (see table 2 and figure 3):

• Broadly supported modular, open architecture platforms like PXI
• Test environment information exchange standards like ATML⁴
• Software-defined instrumentation
• FPGA-based, flexible instrument hardware

Additional industry tools exist in the form of productivity-enhancing software tools for test development as well as for test management. Systems integrating software that enables a graphical design approach offer higher TPS development productivity, increasing the ROI of the ATS program. With graphical system design capability, UUT domain experts can design and implement the necessary tests more efficiently than if they have to iterate back and forth on test requirements and implementation with a counterpart who has software-development expertise but who lacks the domain expertise of the UUT design and functionality.

In the face of the extended TPS burden, test systems with comprehensive test management software offer significant advantage (see figure 3). A effective test management software tool:

• Supports a wide range of test development environments
• Supports a multiple versions of those environments
• Supports use of industry standards like VISA, IVI, and ATML
• Provides database connectivity
• Enhances productivity by speeding development of custom operator interfaces
• Enhances system resilience by giving system designers the ability to quickly create abstractions layers and easily add new elements

Support for multiple test development environments support increases the spectrum of legacy TPSs that can be offloaded from aging testers and consolidated to a single unit. It also provides organizations financial and schedule flexibility for spreading development workload across a wider range of manufacturer domain experts, organic TPS developers, and supporting contractors. By enabling each of these experts to work in the test development environment they know best or that delivers the best functionality for specific test applications, such systems allow faster, more economical delivery of critical TPS capability than a one-size-fits-all development structure.

Compatibility with previously released versions of a test development environment expands the scope of time over which the ATS offer an effective solution for TPS development and operation. Whereas abstraction layers provide protection when a test asset becomes obsolete, backward software compatibility from multiple-version support protects the TPS itself from becoming obsolete when test station software is upgraded.