Vibration, position sensors offer benefits to infrastructure

Aug. 5, 2019
From bridges to buildings and trains, vibration and position sensors strut their stuff 

One of the goals of the Off-Site Insights blog was to explore how common process automation tools and technologies are being implemented in other industries. Lately, sensors integrated into infrastructure have been among the technologies I’ve noticed getting a lot of attention.

Whether in buildings or on trains, vibration and position sensors, in particular, are offering a plethora of benefits to civil engineers, and are helping to identify needed maintenance and prevent catastrophic damage.

One example comes from The Hong Kong Polytechnic University, which recently developed fiber-optic sensors that measure acceleration and vibration on trains. When integrated with artificial intelligence, the sensors could help in monitoring the health and maintenance needs of railways to prevent accidents and train derailments, according to an article from The Optical Society.

The accelerometer/vibration sensors are described in Optics Express. They monitor wheel-rail interactions via the detection of frequencies more than twice that of tradition fiber-optic accelerometers.

“In addition to railway monitoring, these new accelerometers can be utilized in other vibration-monitoring applications, for example, structural health monitoring for buildings and bridges, and vibration measurements of aircraft wings,” Zhengyong Liu, Photonics Research Center, Department of Electrical Engineering, The Hong Kong Polytechnic University, said in the article.

Another example follows the news of the series of earthquakes in California earlier this month. In order to help evaluate structures for safety after an earthquake, the Lawrence Berkeley National Laboratory developed a Discrete Diode Position Sensor (DDPS). The sensor autonomously captures and transmits data about the relative displacement between two adjacent stories of a building, according to a news release from Berkeley Lab.  

Work began in 2015 with other scientists and engineers at Lawrence Livermore National Laboratory and the University of Nevada-Reno. After four years in development, the DDPS system will be deployed for the first time in a Berkeley Lab building near the Hayward Fault.

“Until now, there’s been no way to accurately and directly measure drift between building stories, which is a key parameter for assessing earthquake demand in a building,” said David McCallen, a senior scientist in the Energy Geosciences Division at Berkeley Lab and faculty member at the University of Nevada, who leads the research collaboration, in a statement.

The traditional method to measure damage used motion earthquake accelerometers that acquired data on the back-and-forth and side-to-side motion of a building. However, the data obtained by these accelerometers was difficult to process due to frequency limitations, especially for buildings which had incurred permanent damage, the news release reports.

Instead, the DDPS combines laser beams with optical sensors. A laser light is positioned to strike a detector on an adjacent floor to measure structural drift, thus the senor can track the position of the moving laser beam.

“Previous generations of DDPS were quite a bit larger than the system we are now able to deploy,” McCallen said in a statement. “Based on design advancements and lessons learned, the sensor is a quarter of the size of our original sensor design, but features 92 diodes staggered in a rectangular array so that the laser beam is always on one or more diodes.”

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