Custom Test Systems for the Aerospace / Defense IndustryDavid LaVine2019-10-07T09:11:15-04:00
Aerospace Test Systems | Defense Test Systems
Custom Test Equipment for the Aerospace / Defense Industry
Over 300 aero-def test solutions delivered
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You’re risk averse and your customers expect a high level of rigor because your products are mission-critical.
With hundreds (>300) of aero-def test solutions delivered, our aero-def expertise focuses on test system development (both manufacturing test & product/design validation) for mission-critical components and sub-systems.
How we can help: our capabilities & expertise
Manufacturing test system development
Product validation system development (including endurance/reliability/durability testers)
HIL (Hardware-In-the-Loop) modeling using real-time, FPGA, and Simulink models
PID control loop development
Signal acquisition – e.g. pressure, vibration, load, temperature, force, distance, strain
Replacing Wire-wrap Boards with Software, FPGAs, and Custom Signal Conditioning
Electronic components of fielded systems were aging out Reverse engineering effort converted wire wrap boards to FPGA-based I/O
Client – Amentum – A supplier for Military Range System Support
Amentum (www.amentum.com) supports a decades-old system deployed in the early 1980s. While the mechanical subsystems were still functioning, the wire-wrapped discrete logic and analog circuitry was having intermittent problems.
Systems designed and built decades ago can sometimes have wonderful documentation packets. Nevertheless, we’ve been burned too often when the docs don’t incorporate the latest redlines, last-minute changes, or other updates.
The replacement system needed to be a form-fit-function replacement to land in the same mounting locations as the original equipment with the same behavior and connections. Below is an image of the existing wire-wrap boards and their enclosure. We had to fit the new equipment in this same spot.
Figure 1 – Original wire-wrap boards
Finally, Amentum wanted to work with Viewpoint in a joint development approach. While our joint capabilities looked complementary, we didn’t know at the start how well we would mesh with our technical expertise and work culture – it turns out we worked extremely well together as a team and neither one alone could have easily delivered the solution.
Since the team treated the existing documentation package with suspicion, we adopted a “trust but verify” approach. We would use the documents to give overall direction, but we would need details from the signals to verify operation.
Leveraging Amentum’s experience with the fielded systems, the team decided early on to record actual signals to understand the real I/O behavior. We used the system’s “test verification” unit to run the system through some check out procedures normally run prior to system usage. This verification unit enabled us to use a logic analyzer for the I/O to and from the discrete logic digital signals and an oscilloscope and DMM for the analog signals. The available schematics were reviewed to assure that the signals made sense.
With a trustable understanding of system operation, Amentum created a requirements document. We jointly worked on the design of the new system. There were both an “inside” system (in a control shelter) and an “outside” system (in the unit’s pedestal).
Some overall tasks were:
Viewpoint recommended an architecture for the inside application running on PXIe LabVIEW RT and FPGA layers.
Amentum created the system control software on a Linux PC.
Viewpoint developed the more intricate parts of the inside application and mentored Amentum on other parts they developed. This work recreated the existing discrete logic and analog I/O using PXIe NI FPGA boards.
Viewpoint designed custom interposer boards to connect harnesses to the NI PXIe equipment, including a test point and backplane boards.
Amentum designed and developed the cRIO-based outside system application and Viewpoint created a set of custom interposer boards to connect harnesses to the cSeries modules.
The PXIe FPGA boards handled the required 60 MHz clock-derived signals with correct phases, polarity, and so on. Furthermore, the wire-wrap boards were register-based so the PXIe had to decode “bus signals” sent over a Thunderbolt bus to emulate the programming and readouts from the various wire-wrap boards.
Figure 2 – PXIe replacement to wire-wrap boards
Amentum wanted to be able to support the LabVIEW FPGA VIs used to replace the functionality of the discrete logic. So, Viewpoint acted as mentor and code reviewer with Amentum to ramp them up on using LabVIEW FPGA effectively. Neither one of us alone would have been successful coding the applications in the allotted time. Joint knowledge and experience from both Viewpoint and Amentum were required.
Signal conditioning and harnesses needed to be reworked or replaced as well, of course, since the landing points for the wires were different in the new system. Viewpoint suggested a technique, which we’ve used frequently in past obsolescence upgrade projects, to create PCB boards that accepted existing connectors.
For the cRIO, these interposer “connection” PCBs plugged directly into the cRIO cSeries module. For the PXIe, these interposer PCBs accepted the field wiring connectors and converted them to COTS cables that connected to the PXIe modules. These interposer PCBs could have signal conditioning incorporated as needed. This approach significantly reduced the need for custom harnesses. All told, about 200 signals were passed between the PXIe and various other subsystems, and about 100 for the cRIO. This approach saved significant wiring labor and cost.
Figure 3 – cRIO with interposer boards between cSeries and field harnesses
The work to design and build the signal conditioning custom electronics was split between Viewpoint and Amentum. Viewpoint did more design than build and handed over the schematics and Gerber files to Amentum so they could manage the builds while also being able to make modifications to the boards as needed.
Amentum wanted an engineering firm that was willing to work along side them as a partner. Joint discussions about architecture and design led to a collaborative development effort where Amentum benefited from Viewpoint’s extensive expertise and guidance on LabVIEW architectural implementation and FPGA coding style.
The main outcomes were:
As a partner of the team, Viewpoint acted as staff augmentation by providing experienced engineers with technical capabilities that Amentum initially lacked.
This team approach delivered a stronger product to the end-customer more quickly than either of us could do alone.
The combination of Viewpoint’s and Amentum’s experience reduced the amount of reverse engineering needed due to the lack of firm requirements.
Reduction of electronics obsolescence by using software-centric FPGA-based functionality. Recompiled LabVIEW FPGA could target future boards models.
Increased software-based functionality simplifies future updates and modifications.
Decrease in number of parts leading to simpler maintenance.
Lower wattage consumed eliminated need for an anticipated HVAC upgrade.
Cybersecurity concerns were reduced by using Linux-based systems and FPGA coding.
Using software to emulate the old hardware was a critical success factor. Since the requirements were not 100% solid at the start of the project, some field-testing was required for final verification and validation. The flexibility of the software approach eased modifications and tweaks as development progressed. A hardware-only solution would have necessitated difficult and costly changes. For example, some of the changes occurred very near the final deployment after the system was finally connected to an actual unit in the field.
Emulate original discrete logic functions via FPGAs
Emulate original analog signal I/O
Overall system control via Linux PC
Maintain the same user experience as existed before
Modern application architecture for simpler maintenance
NI cRIO chassis with various cSeries modules
NI PXIe chassis with FPGA modules to handle all the analog and digital I/O via a combination of multifunction and digital-only cards
Custom PCBs for signal conditioning and connectivity
Custom FlexRIO Adaptor Module supports HIL Test Upgrade
A custom-COTS approach reduces cost and delivery time.
Client – Major National Research Lab
Our client has a client (the end-user) for which they developed an HIL test system several years prior. Parts were obsolete and the system needed an upgrade. The prior system had many custom-designed electronic components which could not be replaced without a complete redesign.
Consequently, our client wanted to use COTS. However, one device needed 28 VDC digital I/O, a couple of lines which carried significant current (amp, not milliamp, levels) and at switching rates much higher than a COTS solid state relay could provide.
Viewpoint reviewed the requirements and created a hybrid COTS-custom solution. We combined an NI FlexRIO module with a custom FlexRIO Adapter Module (FAM) for the front end to satisfy the 28 VDC signals levels and required current drive.
COTS FlexRIO integrates into the remainder of our client’s PXI-based test system.
The Custom I/O was designed for flexibility. Our client can use this FAM for both their initial end-user and other programs / clients too.
Reduced cost relative to a completely custom solution.
Delivery time reduced by months relative to a custom solution
The custom FAM interfaced with the NI FlexRIO module, which offered low-level digital I/O (3.3 V logic), to digital signal conditioning hardware that provided the 28 VDC signal levels and required current drive.
Each I/O pin was configurable as input or output (source or sink). Each bank of 4 channels had an adjustable threshold level set via an adjustable DAC output. Some of the channels are designed for amp-level current drive, while the remainder were 250 mA. All I/O was fused appropriately.
Viewpoint also developed LabVIEW FPGA and VHDL to enable our client and the end-user to:
Configure the I/O as in or out.
Communicate to the DAC to allow custom input threshold trigger levels.
At maximum throughput, the Aedis systems needed to consume and produce more than about 800 MB/s/slot.
A large company involved in C4ISR was developing a system for a new high-speed digital sensor device. Viewpoint was contracted to build a test system used in design validation and ultimately endurance testing of the sensor. Since the sensor was a component of a larger system which was being developed at the same time, another test system was created to simulate the sensor by feeding signals into the system.
Both the amount of data and the frequencies of the various digital signals were nearly at the limit of hardware capabilities. At maximum throughput, the systems needed to consume during record and produce during playback about 800 MB/s/slot. The FPGA clock on the FlexRIO had to run up to 300 MHz. The skew between triggers for data transmission needed to be less than 5 ns even between multiple FlexRIO cards even when the parallel data paths has inherent skews associated with the sensor. Finally, the systems needed to handle clocks that might be out-of-phase.
Achieving these requirements required significant engineering design in the face of multiple possible roadblocks, any one of which could have eliminated a successful outcome.
Furthermore, as usual, the development timeline was tight. In this case, it was a very tight 3 months.
To meet the timeline, we had to work in parallel across several fronts:
LabVIEW-based application development for both record and playback
LabVIEW FPGA development for marshalling data between the controller and DRAM
Custom FAM circuit board design and build
FlexRIO FPGA CLIP nodes and code for low-level data handling
This sensor had several parallel data paths of clock and data lines with clock speeds up to 300 MHz on each path requiring exacting design and build of a custom FlexRIO Adapter Module (FAM) and unique custom CLIP nodes for extending the FlexRIO FPGA capabilities. The FAM also had a special connector for interfacing to the customer’s hardware.
Additional NI hardware and software completed the system components.
The choice to base the Aedis emulators on NI hardware and software was critical to completing this project. The open architecture in both hardware (custom FAM) and software (CLIP Nodes) enabled us to include some very creative extensions to the base toolset without which the project would not have succeeded in the allotted pressured schedule and on a predetermined budget. We were able to stretch the capabilities of the hardware and software very close to their maximum specifications by combining COTS and custom much more cost effectively than a purely custom design.
The host application, written in LabVIEW, managed the configuration of the data acquisition and the control of the LabVIEW RT-based FlexRIO systems. The configuration primarily dealt with the number of sensor channels in use, skew settings between digital lines, and other parameters that dealt with the organization of the data passed between the sensor and the FlexRIO.
Two FlexRIO applications were written, one for record and one for playback. Each FlexRIO application was written in LabVIEW, and managed the configuration of the FlexRIO cards and the movement of data between the FlexRIO cards and the RAID drives. Note that Windows supported for the RAID driver. Between 10 and 32 DMA channels were used for streaming, depending on the number of sensor channels being used.
And, each FlexRIO application had an FPGA layer, written in LabVIEW FPGA enhanced with custom CLIP nodes. For the record application, we developed a custom DRAM FIFO on the FPGA to assist with the latencies on the PXIe bus. For the playback application, we were able to stream directly from DRAM.
The FlexRIO and stock FAMs from NI were initially considered as candidates for this project. Clearly, working with commercial-off-the-shelf (COTS) components would be most effective. Three options were available at the project start which could accommodate the required clock frequencies, but none offered both the required channel counts and skew/routing limitations. Hence, we had to design a custom FAM. This decision, made before the start of the project, turned out to be wise in hindsight because the parallel development path resulted in some shifts of sensor requirements which could be accommodated with the custom FAM but might have led to a dead-end with a COTS FAM.
In LabVIEW FPGA, a CLIP Node is a method to import custom FPGA IP (i.e., code) into a LabVIEW FPGA application. CLIP stands for Component-Level Intellectual Property. We needed to use special Socketed CLIP Nodes (i.e., VHDL that can access FPGA pins) for this project because we could expose additional features of the Xilinx Virtex-5 not exposed in LabVIEW FPGA by accessing Xilinx primitives. Some specific features were:
Faster FPGA clocking
Additional clocking options
Individual clock and skew control
Custom PLL de-jitter nodes
Essentially, the FPGA design had a majority of FPGA code developed in LabVIEW FPGA and we used CLIP Nodes for interfacing the signals between the FlexRIO and the FAM.
FlexRIO Adapter Module
As mentioned earlier, we had to create a custom FAM because of the need to route high speed signals from customer-specific high density connectors while synchronizing signals across multiple data channels and FPGA modules to within one (300 MHz) clock cycle.
At these high-speeds, the FAM needed careful buffering and impedance matching both on the signals as well internal components on the FAM PCB. At the start of the design, we utilized Mentor Graphics HyperLynx High Speed DDR signaling Simulation software to minimize signal reflections prior to building actual hardware. This step saved countless hours in spinning physical hardware designs.
We designed the FAM to allow channel routing and access to additional clock and trigger pins on the Xilinx chip and PXIe backplane.
An automated system permits faster validation, unattended test, an increase in throughput, and can free up resources for other tasks during the weeks long endurance test.
Client – A manufacturer of aircraft components in the mil-aero industry
New product development drove the need for a new endurance test system for product validation. The old systems were not designed to test the newly designed part (aircraft actuators), and the company didn’t have the time or resources to reconfigure existing systems to perform the testing required.
The new PXI-based endurance test system provides automated electromechanical testing, full data recording, report generation and a diagnostic panel for intelligent debug. Viewpoint selected the NI equipment, while the test consoles, and other components were selected and fabricated by the customer.
An automated system permits faster validation, unattended test, an increase in throughput, and can free up resources for other tasks during the weeks long endurance test.
Full data recording with a data viewer enables post analysis, which provides the ability to review and analyze raw signals captured during execution. Channel examples are actuator LVDT position, load, current, and encoder actuator position.
Summary report capability allows the customer to document the amount of testing completed against the full endurance test schedules.
A manual diagnostic operational panel provides the ability to verify particular DUT functionality or components without running an entire schedule.
Systems can be paused and restarted to allow for “scheduled maintenance” of the DUT such as inspections, lubrication, etc.
The PXI-based endurance test system enables data collection, deterministic PID Loop Control, emergency shutdown and a diagnostic panel for manual test and debug operation. The system runs endurance test schedules, that are defined as a recipe for test execution. These schedules, which are customer-defined and DUT-specific, are designed to simulate the actual conditions the DUT would see in real world application as closely as possible. LabVIEW-RT was used for the deterministic looping for Closed Loop Control of Actuator Position and Load Control. LVDT demodulation was performed on a PXI FPGA card programmed with LabVIEW FPGA.
Full Data Collection for Real-Time and Post Analysis
Deterministic PID Loop Control
Diagnostics Panel for Manual Test and Debug
Endurance Test Schedule Execution
Hydraulic Control Panel for Source & Load PSI Control
Ability to run tests unattended and overnight reduces operator labor and compresses test schedules
Client – Major Aerospace Component Supplier / Manufacturer
The client had an older VB & PLC-based test system in place already, but it was obsolete. A new endurance test system needed to be developed to validate prototyped components (in this case, aircraft & aerospace bearings). Many of the prototypes are one-off, so it was important that the test system not destroy the component.
A new endurance test system was developed to validate prototyped components. The test system can be configured for automatic shutdowns so as not to destroy the component under test in the event of unexpected performance of electro-mechanical subsystem components. The updated endurance tester supports product validation by allowing the product to run under various test conditions (e.g. speed, load, oil flow, temperature) and collecting data for analysis.
Viewpoint developed the software and selected the NI hardware (other hardware was selected by the client).
Ability to run tests unattended and overnight eases operator labor and compresses test schedules
Data collection allows for offline engineering analysis
Automatic shutdowns reduce destruction of the prototype component under test
The updated cRIO-based endurance tester incorporates configurable profiles, data logging, and automatic shutdown to allow for safer extended validation testing. LabVIEW FPGA and LabVIEW RT were used together to interface with the test hardware sensors and controls. LabVIEW as used create the HMI for the test system.
Closed loop control of bearing test oil flow
Axial load control
Driver for Emerson VFD
E-Stop and safety management (shutdowns based on alarm limits)
Data collection – temperature, pressure, flow, vibration, frequency
It did not provide ability for unattended operation
The thermal control had to be set manually
They wanted to do less manual review of the data
The client develops mission-critical products, so there’s a desire to reduce manual operations because they have to explain any anomalies, and manual operations are typically more error-prone. They needed repeatable results that they could trust.
Viewpoint developed a new test system that utilized new hardware and software, augmented by existing low level hardware and firmware. The test system was developed to perform both functional test for production and environmental testing, and was designed to handle up to 4 DUTs at once. The test system utilizes the StepWise test executive software with custom test steps, which allowed the client to create their own highly configurable test sequences. The system was developed in two phases, with the second phase adding support for a FPGA expansion backplane (NI CompactRIO chassis) in order to provide future capability for bringing some of the microcontroller sequence activity into the NI space. In addition, the previous version had a mix of serial, TTL, and USB instrumentation, which was not as robust as Ethernet based instrumentation. Phase II involved upgrading to all Ethernet based instrumentation, and did away with the original test system’s many manual toggle switches that could be used instead of the programmable mode through the SW.
~40% test time reduction per unit
~25% reduction in anomalies that needed to be justified
Sharing Business and Test Data Enables Efficiency Improvements
Reduce Production Costs by Coordinating Business and Test Data
Client: A major manufacturer of aerospace components
Many companies operate in a high-mix, low-volume manufacturing environment. In these situations, production of such parts is often complex, with long assembly and test procedures describing the process to make and verify the part. Discussions of automating any part of these processes are often dismissed because an automated test system is thought to be expensive, especially when each part is thought to need a unique test system.
Our client wanted to improve their capability to manage the assembly procedures and get clarity on the status of any parts, whether partially or fully assembled. The existing situation had data manually-entered into a database form or even handwritten data that needed to be transcribed into a database. Often the database was local to the assembly cell. The chance for error was significant and the lag between data collection and updating the database was often days. When questions arose about the status of a particular unit, many hours could be spent in locating and evaluating the associated forms and paperwork.
The steps needed to achieve these goals were clear: automate the collection data on each part while being assembled so that those results would appear in a business-level database which would give a plant-wide view of the status of all the parts in progress.
Thus, this project needed to allow read/write access to sections of the Manufacturing Enterprise System (MES) database so that information about a part being assembled could be obtained automatically and results could be submitted to that MES database automatically.
We designed the PXI-based system based on the StepWise test executive platform to automate the assembly and testing. This platform enables two significant changes. These changes were made at each assembly cell by having the operator use a test PC and perhaps some measurement equipment as appropriate for the part(s) being assembled at that cell.
First, we replaced all the printed assembly procedures with electronic records so that any operator could review the latest version of the work instructions on a computer screen. This approach helped with version control, especially important since the client had various model revisions that came through the factor for rework, each with slightly different versions of assembly instructions.
Second, we displayed those electronically documented work procedures as steps in a test executive, allowing the results of each step in the assembly procedure to be captured electronically. When an assembly step was purely manual with no measurements, the fact that step was completed would be recorded, along with information such as the name of the operator performing the step, the duration that the step took, and so on. When a step required a measurement to be made, such as a functionality verification or a calibration result, the measurement would be collected. If the equipment making that measurement could be automated, we would collect that data automatically, and not require the operator to type the result into a computer form.
The outcome of this effort has enabled the client to get a snapshot of the status of parts in assembly, i.e., Works in Progress (WIP), quickly and accurately.
After these changes were made, many additional capabilities are now available with the advent of purpose-built queries into the appropriate MES database tables. The table below shows the overall efficiency gains achieved.
The key is the combination of the electronic test results obtained at the test equipment with information on work orders and manufacturing flow held in the various tables in the business MES database. This improvement happens even with manual or semi-automated test systems, and does not require a completely automated assembly and test system. Thus, the cost of the test system is much less than usually expected and, hence, the benefits are more easily cost-justified.
Client: A major manufacturer of aircraft landing systems
A major manufacturer of aircraft landing equipment needed to develop a means of endurance and fatigue testing new designs for aircraft steering. The actuators involved in steering the nose landing gear (NLG) required precise and reliable control through thousands of steering cycles.
Control loops needed to be closed at faster than 1 ms.
Prior systems were handled manually without real-time control and monitoring.
Our customer designed and built a test rig to provide the hydraulics and environmental conditions for the endurance testing on the NLG. Viewpoint Systems supplied the electronic data acquisition and control hardware coupled with real-time software to provide the required fast control loops. The configuration and execution of the 1000s of steering cycles were managed by the same data acquisition and control system through a set of configuration screens that allowed specification of turn rates, min/max angles, drive and resistive torque settings, and so on.
The various PID control loop configurations were also configurable along with gain scheduling required under different operating conditions.
The environmental conditions were supported by controlling a temperature chamber through ramp and soak settings occurring during the steering tests.
Measurements on the steering performance were collected from commanded setpoints, sensor readings, and controller outputs during the entire test run.
Alarm and fault conditions, such as force exceedance, were monitored continuously during operation so that the system could safely run unattended.
The entire system underwent an extremely rigorous acceptance testing procedure to verify proper and safe operation.
Arbitrary Load and Position Profiles
Flight Position Control
Load Position/Force Control
Endurance/Flight Schedule Execution
Deterministic RT for DAQ and PID Control
PXI/SCXI Hybrid RT Chassis
Discrete Pump Skid Interface
Custom Control Panel/Console
Prior to deployment of our system, setup of a test was much more manual and operators needed to be around to monitor operation.
With our new system, complete endurance testing could be specified and executed with minimal supervision. Furthermore, the tight integration of real-time control and coordinated data collection made report creation much simpler than before.
The rigorous acceptance test gave trustworthiness to the data and allowed the design engineers to validate performance more quickly than the prior semi-automatic and manual methods of operation.
Setup of tests has been improved from prior operations. The endurance testing itself operated over a huge number of cycles lasting weeks to months between scheduled lubrication and maintenance.
The deployed system measures performance during the entire testing, even between the scheduled downtime.
If you need a custom test system for your mission-critical aero-def component, reach out here.
Designs need to be extensively validated, and manufactured products require comprehensive testing. In contrast to aero-def products from the early 2000s, an increasing number of products now use embedded controllers. Such products require interfacing to electronic components in order to test the combined mechanical and electrical performance of the entire system. Products often need the test system to simulate the surrounding subsystems and/or environment in order to assess performance in as realistic a situation as possible. These simulations are usually handled by either Hardware-In-the-Loop (HIL) or Software-In-the-Loop (SIL) subsystems. Depending on the levels of allowed latency and jitter levels, the HIL simulation may run on either or both of an FPGA or an RTOS that supports hardware I/O. The SIL simulation will almost always need an RTOS.
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