Tracewell Systems

December 2, 2003

Military Automatic Test System (ATS) designers must address the issues of obsolescence, portability, scalability, configurability, cost/performance, and software transportability while allowing the flexibility to add new technologies without full-scale system replacement. ManTech Test Systems, developer of Automatic Test Equipment and related technologies, has teamed with Tracewell Systems, a mechanical system design, fabrication, and manufacturing house, to develop a more mobile, lightweight, adaptable field test unit for the military. Using innovative approaches to old problems, ManTech and Tracewell were able to create a unique test system that eliminates the military’s challenges and allows for customization. Figure 1 depicts this pioneering ATE design.

ATE manufacturers traditionally start with existing designs that have post design add-ons to satisfy new requirements. The result produces inefficient designs with built-in obsolescence. The enhancements are generally designed for a specific purpose and therefore not readily adaptable for different applications. ManTech and Tracewell have taken a fresh approach to ATS design with the goal of creating an innovative, portable, deployable test system that was modular, multi-purpose, and easily customizable. Developed using a series of new technologies and focusing on power system interconnects, management systems, and control systems, this new breed of ATE addresses each of the challenges that cannot be easily overcome with legacy systems. The system design supports future test needs and permits flexible insertion of updates and new technology with a minimum impact on existing components, all while promoting transportability. Commercially supported specifications and standards were selected for system interfaces (logical and physical), products, practices, and tools. Key considerations of interfaces, architecture, risks, and supportability are based on adopted industry consensus-based standards bodies or de facto standards:

• Evaluation of the short- and long-term availability of products.
• Disciplined systems engineering process that examines tradeoffs of performance, supportability, and upgrade potential.
• Allowance for continued access to technological innovation.

ATS designs have been traditionally built on a single bus structure that is chosen as the best fit for the particular application. IEEE-488 instruments yield large systems that can be accommodated on factory floors, but are ill suited for portable applications. The advent of VXI, an extension of the VMEbus, allows smaller systems that are transportable, however it stops short of allowing lightweight highly portable systems. PXI, based on CompactPCI affords the highest levels of portability but may not offer the range of instrument options necessary to meet all performance requirements.

ManTech and Tracewell have created a flexible architecture that is multi-platform and scalable using IEEE-488, VME/VXI, and CompactPCI/PXI. The result is a core system design that provides the integrator with a much broader choice of instrumentation options. Large, medium, and small format modules may be mixed in a single system, creating an environment that exploits the benefits of the various architectures without sacrificing performance, size, or limiting future expansion.

At the heart of this fresh approach is a universal Inner Chassis built as a self-contained unit that performs as either a rigid VXI/PXI card cage, a System Power Chassis, a DC UUT Power Chassis, or a 19-inch subframe for IEEE-488 equipment. It is integrated within the operating enclosure for shock and vibration performance only, but does not rely on the enclosure for EMI shielding. The revolutionary chassis design uses laminated side panels for high structural integrity without adding weight, and EMI/EMC considerations were part of the initial design strategy, rather than post design stopgaps. VME and CompactPCI sub chassis are incorporated within a single lightweight structure using the latest in backplane technology. Figure 2 shows the integrated components in the chassis package.

Borrowing on the design consequences of the telecom industry, backplane power supplies developed to be modular so that power can be matched to the requirements of the instrument compliment each other. The redundant 1600W VXI/PXI power supplies are front pluggable for ease of maintenance. Distributed throughout the system is a 48VDC rail that simplifies the local power design issues, reduces system noise, and improves the overall safety of the system operator and maintenance personnel. Distribution of signal wiring is accomplished via an Intra-System Connector Block. All intra-system wiring is routed through fixed position, blind-mateable connectors.

Fixed system interconnects, found in traditional Automatic Test Systems make relocation of the system difficult without extensive teardown and setup times. ManTech Test Systems and Tracewell have created an innovative System Interface Frame Assembly (SIFA) that provides the mechanical and electrical interconnection between enclosures. The SIFA is supported with four legs that are constructed using laser-welded corrugated aluminum. These legs attach to the SIFA to create a rigid, freestanding structure providing support for transit/operating enclosures. Interconnects and cooling methods are shown in Figure 3.

An Interface Connection Block is used to electrically connect each of the six enclosures. The ICB uses connectors that float within the SIFA, while complementary connectors within the enclosures are fixed. This connection system is integral to the Inner Chassis within each enclosure and is capable of carrying power, LF signals, RF signals, and fiber optic signals. Tracewell mechanical engineers placed all affected mechanical components on a dimensional coordinate system and calculated the extremes of movement of the ICB. The result was an ATE design built from the ground up to use a reliable connection system incorporating several important features:

• The system is contained within the Inner Chassis and is immune to dimensional changes in the transit case.
• The connector block is a rigid folded-steel structure that maintains accurate alignment within the manufacturer’s specifications for misalignment radii.
• Mechanical connections are made between a single Inner Chassis and the SIFA. Individual enclosures and Inner Chassis are not connected to each other in any fashion, but rather connect to a single surface within the SIFA, eliminating tolerance stack-ups.
• The dimensions of the SIFA are tightly controlled using laser-welded honeycombed material.
• Large guide pins eliminate connector stresses and expand the capture range of the connection system.

The idea was to design a modular, hierarchical, and layered architecture based on open standards at its interfaces.

This led to the use of the following components to create an open, flexible architecture that served the military’s needs:

• Open systems standards and platform
• COTS hardware and software
• Cost-effective, low-risk, high payoff technology
• Inter- and intra-operability
• Improved instrument interchange
• Scalability and adaptability
• Common look and feel
• Simplicity, user-friendly, and flexibility

The result of these innovations is a tester that is highly expandable, and has the ability to deploy in transit cases (mobile) or rack (depot) configuration. The next generation software approach also addresses the need to transport TPSs from legacy systems as well as support future requirements.