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Ultrasonic Lateral Displacement Sensor for Health Monitoring in Seismically Isolated Buildings.

Matsuya I, Matsumoto F, Ihara I - Sensors (Basel) (2015)

Bottom Line: The transmitters are immobilized at a fixed point, whereas the receiver set-up is separately arranged on the opposite side.In order to improve measurement accuracy, a correction method that utilizes polynomial approximation is introduced.When five transmitters are arranged, their measurement range is easily extended up to ±60 mm with an accuracy of 0.7 mm.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical Engineering, Nagaoka University of Technology, Kamitomioka 1603-1, Nagaoka 940-2188, Niigata, Japan. matsuya@mech.nagaokaut.ac.jp.

ABSTRACT
An ultrasonic lateral displacement sensor utilizing air-coupled ultrasound transducers is proposed. The normally-distributed far field of an ultrasound transducer in a lateral direction is taken advantage of for measuring lateral displacement. The measurement system is composed of several air-coupled ultrasound transducers as a receiver and several transmitters. The transmitters are immobilized at a fixed point, whereas the receiver set-up is separately arranged on the opposite side. In order to improve measurement accuracy, a correction method that utilizes polynomial approximation is introduced. The difference between the corrected lateral displacement and the reference displacement is estimated to be 0.2 mm at maximum for the two transmitters system. A good responsiveness is demonstrated by conducting a dynamic response experiment. When five transmitters are arranged, their measurement range is easily extended up to ±60 mm with an accuracy of 0.7 mm. In both cases, the fluctuations to the measurement ranges show less than 1%. These results indicate that the developed sensor system is useful for measuring relative lateral displacement of a seismically isolated building in the field of structural health monitoring.

No MeSH data available.


Related in: MedlinePlus

(a) Experimental setup for measuring ultrasound intensity distribution of air-coupled ultrasound transducer; (b) Front view of the receiver.
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sensors-15-17000-f002: (a) Experimental setup for measuring ultrasound intensity distribution of air-coupled ultrasound transducer; (b) Front view of the receiver.

Mentions: In order to measure the relative lateral displacement over a wide range, the characteristics of the air-coupled ultrasound are utilized. The intensity of the propagating ultrasound waves in the far field follows a Gaussian distribution in a lateral direction [19,20]. Before measuring lateral displacement, the ultrasound intensity distribution of the air-coupled ultrasound transducer must be characterized. Figure 2 shows the experimental setup for measuring the intensity distribution using the relative lateral displacement of a pair of transducers. As shown in Figure 2a, a transmitter and a receiver of air-coupled ultrasound transducers (UT/UR1612MPR, ϕ16 mm in diameter, 40 kHz for central frequency, SPL Limited, Hong Kong) are arranged at a distance of 60 mm and face each other. The installation space is usually very narrow in seismically isolated buildings, it is essential to show capability of measuring lateral displacement over shorter distances. The distance between transducers is determined by the power of the ultrasonic transducer. So if another ultrasonic transducer is utilized, the distance will be spread more easily. However, we have selected an ultrasonic transducer with lower power in order to measure the displacement over as short of a distance as possible. Because the intensity of the ultrasound beam fluctuates extremely in the near field, which is approximately 14.2 mm, the far field of the transducer is utilized in this experiment [20]. A mask with a central hole is attached to the receiver as shown in Figure 2b. The receiver should receive ultrasound waves only in its central part, which makes the shape of the ultrasound intensity distribution more clear. This mask is made of heavy paper and blocks ultrasound waves at the outer edges of the receiver. The diameter of the mask aperture is designed to be 6 mm, so it can obtain a normally-distributed ultrasound intensity. The origin corresponds to the center of the transmitter. The transmitter is driven by a pulse signal from a square-wave pulsar with a repetition rate of 40 kHz. When the ultrasonic waves are received, the ultrasonic signals are converted into voltage signals inside the receiver. The voltage signals are captured using a 12 bit serial acquisition board at a sampling rate of 100 MHz. The bit level of the sampling is approximately 2.4 mV. In order to reduce the background noise of the signals, the bandpass filter from 30 to 50 kHz is utilized and the average values are calculated from thirty acquired signals. The maximum voltage value is extracted and recorded as the ultrasound intensity. When the receiver is displaced parallel to the x direction from the origin, the ultrasound intensity plots of propagating ultrasound waves are measured according to the x position of the transmitter.


Ultrasonic Lateral Displacement Sensor for Health Monitoring in Seismically Isolated Buildings.

Matsuya I, Matsumoto F, Ihara I - Sensors (Basel) (2015)

(a) Experimental setup for measuring ultrasound intensity distribution of air-coupled ultrasound transducer; (b) Front view of the receiver.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4541918&req=5

sensors-15-17000-f002: (a) Experimental setup for measuring ultrasound intensity distribution of air-coupled ultrasound transducer; (b) Front view of the receiver.
Mentions: In order to measure the relative lateral displacement over a wide range, the characteristics of the air-coupled ultrasound are utilized. The intensity of the propagating ultrasound waves in the far field follows a Gaussian distribution in a lateral direction [19,20]. Before measuring lateral displacement, the ultrasound intensity distribution of the air-coupled ultrasound transducer must be characterized. Figure 2 shows the experimental setup for measuring the intensity distribution using the relative lateral displacement of a pair of transducers. As shown in Figure 2a, a transmitter and a receiver of air-coupled ultrasound transducers (UT/UR1612MPR, ϕ16 mm in diameter, 40 kHz for central frequency, SPL Limited, Hong Kong) are arranged at a distance of 60 mm and face each other. The installation space is usually very narrow in seismically isolated buildings, it is essential to show capability of measuring lateral displacement over shorter distances. The distance between transducers is determined by the power of the ultrasonic transducer. So if another ultrasonic transducer is utilized, the distance will be spread more easily. However, we have selected an ultrasonic transducer with lower power in order to measure the displacement over as short of a distance as possible. Because the intensity of the ultrasound beam fluctuates extremely in the near field, which is approximately 14.2 mm, the far field of the transducer is utilized in this experiment [20]. A mask with a central hole is attached to the receiver as shown in Figure 2b. The receiver should receive ultrasound waves only in its central part, which makes the shape of the ultrasound intensity distribution more clear. This mask is made of heavy paper and blocks ultrasound waves at the outer edges of the receiver. The diameter of the mask aperture is designed to be 6 mm, so it can obtain a normally-distributed ultrasound intensity. The origin corresponds to the center of the transmitter. The transmitter is driven by a pulse signal from a square-wave pulsar with a repetition rate of 40 kHz. When the ultrasonic waves are received, the ultrasonic signals are converted into voltage signals inside the receiver. The voltage signals are captured using a 12 bit serial acquisition board at a sampling rate of 100 MHz. The bit level of the sampling is approximately 2.4 mV. In order to reduce the background noise of the signals, the bandpass filter from 30 to 50 kHz is utilized and the average values are calculated from thirty acquired signals. The maximum voltage value is extracted and recorded as the ultrasound intensity. When the receiver is displaced parallel to the x direction from the origin, the ultrasound intensity plots of propagating ultrasound waves are measured according to the x position of the transmitter.

Bottom Line: The transmitters are immobilized at a fixed point, whereas the receiver set-up is separately arranged on the opposite side.In order to improve measurement accuracy, a correction method that utilizes polynomial approximation is introduced.When five transmitters are arranged, their measurement range is easily extended up to ±60 mm with an accuracy of 0.7 mm.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical Engineering, Nagaoka University of Technology, Kamitomioka 1603-1, Nagaoka 940-2188, Niigata, Japan. matsuya@mech.nagaokaut.ac.jp.

ABSTRACT
An ultrasonic lateral displacement sensor utilizing air-coupled ultrasound transducers is proposed. The normally-distributed far field of an ultrasound transducer in a lateral direction is taken advantage of for measuring lateral displacement. The measurement system is composed of several air-coupled ultrasound transducers as a receiver and several transmitters. The transmitters are immobilized at a fixed point, whereas the receiver set-up is separately arranged on the opposite side. In order to improve measurement accuracy, a correction method that utilizes polynomial approximation is introduced. The difference between the corrected lateral displacement and the reference displacement is estimated to be 0.2 mm at maximum for the two transmitters system. A good responsiveness is demonstrated by conducting a dynamic response experiment. When five transmitters are arranged, their measurement range is easily extended up to ±60 mm with an accuracy of 0.7 mm. In both cases, the fluctuations to the measurement ranges show less than 1%. These results indicate that the developed sensor system is useful for measuring relative lateral displacement of a seismically isolated building in the field of structural health monitoring.

No MeSH data available.


Related in: MedlinePlus