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UMass Researcher Develops New Sensor

Photonics.com
May 2003
AMHERST, Mass., May 22 -- University of Massachusetts (UMass) Amherst researcher Robert Gao has developed a new sensor system that essentially enables machinery to alert human operators when it is overloaded, broken or wearing out. This new sensor technology, for which a patent has been filed, has the potential to bring about improved safety and productivity in the transportation and manufacturing industries. The invention was the result of Gao's research funded by the National Science Foundation.

"Sensors are playing an increasing role in science and society, " said Gao, an associate professor in the department of mechanical and industrial engineering. "An accurate measurement of how much weight a forklift, truck or airplane is carrying, and the distribution of that weight, is of great value in terms of safety. A shift in the load's distribution could indicate a mechanical malfunction or a wornout component; and of course, a machine that is overloaded may not operate safely."

For the past decade, Gao's work has focused on developing various types of tiny microsensors that can be embedded into machine parts, such as bearings, to detect if the machine is endangered by overloading or excessive vibration, which can lead to potential failure. Bearings are widely used to provide support for machinery that rotate, such as the rotor on a helicopter, or the shaft of an engine, Gao explains. A bearing with a microsensor embedded in its structure would be able to send an alarm signal to a remote computer if a problem arises, preventing severe consequences from happening.

However, using conventional sensors for machine load measurement has several constraints, said Gao. For example, strain gauges -- thin strips of a specialized plastic film -- require careful handling as well as wire hook-ups in a bridge circuitry, and need to be constantly power supplied through batteries.

Piezoceramics Revisited
The new sensing technology developed by Gao, in comparison, is based on an innovative use of a certain type of ceramic materials, called piezoceramic. Compared with the strain gauges, a piezoceramic sensor generates an electrical charge when a mechanical load is applied to it, without the need for an extra power supply. Although such materials have already been around for commercial use for decades, problems with the charge leakage have prevented them from being used for machine load measurement. Gao's work found a solution that uses an electronic feedback circuit to maintain the charge, thus presenting a new technique for machine load measurement.

Besides load sensing, Gao and his students have also developed tiny wireless sensors for vibration monitoring directly from inside the bearings, and several new algorithms for the computer to analyze the data. The goal of all this research, Gao says, is to better monitor the "health" condition of a machine. Such knowledge not only helps prevent unexpected and costly machine down time -- it also predicts how much longer a machine will last so that the machine operator can schedule the maintenance tasks in advance.

"The industry needs a new tool for preventative or 'intelligent' maintenance," Gao said, "and we are developing it for them."

For more information, visit: www.umass.edu



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