Automated Test Equipment – Flight Control System

Author(s):
Justin Thomas - Captronic Systems Pvt. Ltd.

Industry:
Aerospace/Avionics, ATE/Instrumentation

Products:
PXI/CompactPCI, LabVIEW

The Challenge:
Developing automated test equipment (ATE) for complete flight control system (FCS) functionality testing by providing an integrated, configurable, and reliable test system in limited time.

The Solution:
Using National Instruments LabVIEW, the NI PXI platform, and NI-DAQmx driver software, along with other third-party hardware, to create a highly flexible, scalable, and powerful test system.

Our client, a leading R&D organization, specializes in developing flight control systems for aircrafts. The FCS is one of the critical components of an aircraft, performing the following important functions:

• Notifying ground stations of aircraft health and position during the entire duration of flight
• Guiding the aircraft to its destination by following flight plans given by ground stations
• Taking recovery actions and landing aircraft safely in case of critical systems failure

These systems require extensive ground testing before they can be integrated into an aircraft. Ground testing involves complete functionality testing of the FCS on the ground by simulating various flight conditions and measuring the FCS responses.

We decided to build the test system based on the open, industry-standard PXI architecture. The NI range of PXI products provided us with hardware for most of our signal types. LabVIEW was the language of choice for programming the system due to its excellent graphical capabilities and tight integration with NI PXI products using NI-DAQmx. LabVIEW drivers were also available for the third-party hardware used.

System Design

Testing the FCS required all possible flight conditions to be simulated on the ground. The FCS received information about parameters like pitch, roll, and throttle from sensors giving analog outputs. These sensors were simulated using analog outputs from the NI PXI-6713. Some onboard sensors generated waveform outputs, which were simulated in the ATE using the NI PXI-6733. The FCS controlled actuators through analog output lines acquired and measured using the NI PXI-6071E.

The FCS uses dual-port memory onboard to store flight parameters and computation results. These were accessed using the NI PXI-6534 high-speed digital I/O (DIO) board. High-voltage relay I/O to the FCS was simulated with the NI PXI-6527 isolated DIO board. GPS data was simulated to the FCS using the NI PXI-8422 serial link.

The synchro link was established using the digital-to-synchro card from North Atlantic, Inc.

Software Features

The software developed in LabVIEW provided two modes of testing for the user:

• Auto Mode – In this mode, the user generates a test list using a wizard. The ATE then conducts the various tests in sequence without manual intervention. Appropriate reports are generated at the end of each test, including measured as well as computed values.
• Batch Mode – In this mode, the user can test the FCS manually. The user can control step-by-step execution of each test. This was mainly used to debug a faulty FCS.

A self -test feature was also provided in the ATE whereby the ATE checks its hardware integrity before connecting to the FCS.

Even though we had to acquire data from a wide range of interfaces, the hardware we used along with NI-DAQmx helped us easily blend all these data together. Toolkits like the LabVIEW Database Connectivity Toolkit and Report Generation Toolkit helped us significantly reduce development time. The great graphical user interface features provided by LabVIEW helped us create a user-friendly human-machine interface.

PCM Commutator-Based on the NI PXI-7831R

An important requirement for the test system was to communicate with the FCS using PCM telemetry. We used a third-party PXI card from Lumistar to decommutate data received from the FCS. We used the NI PXI-7831R for PCM commutation, with a commutation algorithm written in LabVIEW and downloaded onto the PXI-7831R using the LabVIEW FPGA Module. Developing the FPGA-based PCM commutator greatly reduced system costs and provided an easily customizable solution for future expansion. This was a major achievement in this project.

Some of the features of the custom-developed PCM commutator include:

• NRZ-L output format (can be customized for other formats)
• Up to 2 Mbps output data rates
• Up to 16 bits per word (can be customized for 32 bits per word)
• Up to 15,872 words per minor frame
• Up to 1,024 major frames
• Up to 32 bit frame sync pattern   (any series of 0s and 1s can be used)
• Real-time display of transmitted data
• Facility to save configured PCM formats for later use

Conclusion

We were able to design and develop a test system that enabled our client to efficiently test their FCS and provided the flexibility to configure it for various kinds of test setups. The NI LabVIEW graphical development platform and the modularity extended by the PXI architecture equipped us by providing a flexible and reliable solution in record time. Also the analyzed test reports were now ready within minutes of completing a test, saving the customer a few days in manual testing, collating, analyzing, and preparing reports.

For more information, contact:

Justin Thomas

Captronic Systems Pvt. Ltd.

Kormangala, Bangalore, India

Tel: 91-80-25535046

E-mail: Justin@captronicsystems.com

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