Embedded Linux Journal Competition 2001 submission

This page contains the entry that was originally submitted to Embedded Linux Journal for the 2001 competition. As one of the finalists , we were very pleased to receive a donated NIC unit. This CanDetect project web site presents the current state of our work, with the NIC page being especially relevant.

At time of submission, the NIC was believed to have half-duplex sound, which is insufficient for our needs. Thus, we proposed adding an external microcontroller (on the USB bus) that essentially provides a second sound card with the required capabilities. Fortunately, the NIC has full-duplex sound, so the USB device was eliminated.

1. Title and Summary

Non-destructive evaluation of aircraft components for corrosion

A simple and low cost eddy current probe will be interfaced to the NIC, such that a special CD version allows the system to be used to search for hidden corrosion on aircraft during their mandated annual inspections. The user benefit is that the CD can be replaced with a word processing package, or some other specialized vertically integrated application, whenever the eddy current system is not required.

2. Identification of the Opportunity

Every aircraft under US registry is required to have an annual inspection, involving a partial disassembly to find hidden damage, worn parts and components that may be close to failure. The search for corrosion requires extensive disassembly or paint removal, either of which accumulates minor damage to the aircraft itself.

The work is labor intensive and most facilities complete a relatively small number of inspections per year, making the purchase of purpose-specific instrumentation prohibitively expensive.

No low-cost and effective system exists, because the data processing requires an embedded computer system and a clear visual display is needed to communicate the results to technicians. The volumes are low, so that systems that contain embedded computers are extremely expensive. If a general purpose computer is used, both the purchase cost and the subsequent maintenance effort dominate the cost of the corrosion system. If a generic computer is shared with other purposes, the applications often interact and over-all reliability suffers.

The FAA has identified a safety need for an extremely low cost and multi-purpose system and is searching for projects to provide it. A key concern is that the analysis algorithms must be easy to update when new ideas and techniques are developed. It is also desired that the same hardware be able to make measurements based on proprietary algorithms that would be developed by competing companies, in order to avoid the need for the end-user to purchase multiple systems.

We propose that a NIC-based solution can meet all the requirements.

Over 5000 repair stations nationwide perform maintenance on the 163000 small aircraft under the watchful eyes of 36000 experienced aviation repairmen and 340000 (yes, a third of a million) aircraft mechanics.

3. Qualifications

Alex works in research and development programs at Quantum Magnetics on magnetic sensing and imaging technologies and their applications. He holds a PhD in electronic engineering from Cambridge (England), is a senior member of the IEEE, a commercially rated pilot and ground instructor, an Aviation Safety Counselor for the San Diego area and one of the developers for the open source flight simulator FlightGear. Linux-based techniques feature heavily throughout those activities.

4. Additional hardware

A generic multi-frequency eddy current probe. A small ciruit board with the few dollars of components needed to interface it to the computer. I expect to use the little microcontrollers with built-in USB 1.1 support.

5. Technical Approach

Add the USB driver for the eddy current probe to the operating system. The reference design will simply make time domain and frequency domain measurements and show the results on the screen. A simple public domain algorithm will be used to estimate metal thickness (and thus the amount of material lost due to corrosion). The calculations can easily be implemented using a combination of Octave and GnuPlot, both of which are stable Open Source projects and popular for R&D.

6. Related Work


The research community is still developing appropriate techniques to optimize the analysis of data to detect microcracks and the dozens of different kinds of corrosion. The SPIE, for example, has an entire annual conference stream dedicated to this work. Therefore, it is essential that the end-user can combine a single computer chassis with a proprietary software image. By building an open source reference design for that software image, the competing groups can offer many different approaches to the end-user community.

7. Submitted by

Alexander Perry