A highly flexible automated prognostics and diagnostics sensor module (PDSM) prototype is presently under development to be incorporated for data acquisition in a Prognostics and Diagnostics Health Monitoring System (PDHMS). PDHMS acquires, stores, and communicates data gathered from sensors that monitor essential platform components to determine its current diagnostic status. This diagnostic data is used to make reliable prognostications of remaining operational life expectancy based on a platform usage profile.

The overall design concept for a Full PDHMS incorporates one or more prognostics and diagnostics sensor modules (PDSMs) that independently measure test points of interest.
The PDSM has the capabilities to monitor fielded electronic systems and perform data acquisition functions on key test points of both legacy platforms and new platforms for PD analysis. The general functionality of the PDSM is to measure system current draws, surface temperatures, voltages of interest, and shock and vibration behavior of various test points. Due to the low-voltage microcontrollers (MCUs), all sensors have circuit protection hardware inline with the sensor test pins to minimize the possibility of damage to the MCU. The PDSM also keeps historical records of when measured parameters cross known thresholds that can lead to system failures. Threshold and usage data can be used strictly as a precursor or also to develop more sophisticated prognostics algorithms for the platform in question.

Currently, the prototype PDSM is being developed to monitor fuse temperatures, component surface temperatures, component voltage and current levels, and system vibration and shock behavior. The temperature, current, and voltage sensors will continuously monitor the fuses and surrounding circuitry to collect data on system behavior leading up to the provoked electronic fault. This data will be used to develop monitoring techniques and algorithms to detect and prevent possible fuse failure in other military systems.

The PDHMS is composed of one or more PDSMs designed to independently take measurements on test points of interest and the Prognostics and Diagnostics Control Station (PDCS) (see figure). The PDSM is programmed through the use of the standard JTAG interface, and can be programmed to have its wireless IEEE 802.15.4 hardware enabled or disabled depending on the application.

The PDSM stores data acquired from the test points until it can be transferred to the PDCS. A PDCS running the wireless protocol can remotely request and retrieve all acquired data from the PDSM, and perform a more extensive data analysis. A flexible design means any number of PDSMs can be incorporated into a PDHMS to monitor a system of interest. They can communicate with the PDCS either via wireless communications, or through the I2C hardwired serial interface. The PDSM is fabricated on a custom printed circuit board (PCB) using commercial off-the-shelf components. The heart of the design is the use of the Texas Instruments low-power MSP430 MCU and the CC2420 ZIGBEE low-power transceiver. The PCB dimensions are 2 × 4". The MSP430 can operate from either a 6-MHz clock or a slower 32-KHz clock. Because measurements will be made from multiple sensors, and the aggregate data rates are anticipated to be higher than can be supported by the 32-KHz clock, the 6-MHz clock will be required.

This work was done by Gregory Mitchell, Marvin Conn, Russell Harris, and Andrew Bayba of the Army Research Laboratory. ARL-0060

This Brief includes a Technical Support Package (TSP).
Automated Data Acquisition for a Prognostics and Diagnostics Health Monitoring System

(reference ARL-0060) is currently available for download from the TSP library.

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This article first appeared in the August, 2009 issue of Defense Tech Briefs Magazine.

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