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Vibration sensor module for structural monitoring
The Vibration Module is a system designed for measuring acceleration on 3 axes remotely and in the absence of power sources, for a limited duration, useful for verifying the stability conditions of bridges or building structures that have been subjected to stress due to significant events that may have damaged their structure.
The device can be on the structure to be monitored manually or positioned using a drone which will pick up the object, fly up and stick it on the target to be monitored. To allow the drone to transport the Vibration Module we designed a device that is small in size and light in weight, building a plastic mechanism where it is housed inside the electronic board with the acceleration sensor in contact with the surface of the box.
Vibration module attaching procedure with drone
Sensor module design and specification
Triaxial accelerometer characteristics
Triaxial accelerometer in the ±2 g, ±4 g or ±8 g (acceleration range digitally programmable)
20-bit analog-to-digital converter (ADC) sensitivity 400 mV/g for 3.3V supply operation
Ultralow noise density (all axes): 20 μg/√Hz
Power consumption in standby mode: 21 μA (200 µA in measurement mode)
Bandwidth: 1 kHz
Input & Output data
Measurement parameters configuration:
Sampling frequency
Acceleration range (±2g, ±4g, ±8g)
Optical transmit power (up to 14 dBm)
Acceleration low pass filters cut-off frequency
Acceleration high pass filters cut-off frequency (if needed)
Transmission bandwidth
Data Outputs:
3 axes acceleration data
Acceleration amplitude spectra
Module temperature
Battery voltage
System characteristics
48-MHz Arm® Cortex® -M3 microcontroller
RX: 5.4 mA – TX at +10 dBm: 13.4 mA power consumption
Wireless M-Bus (EN 13757-4) and IEEE® 802.15.4g PHY
315-, 433-, 470-, 500-, 779-, 868-, 915-, 920-MHz ISM and SRD System
Active-Mode MCU 48 MHz Running Coremark: 2.5 mA (51 µA/MHz)
Package diameter: 50 mm. Package height: 30 mm. Overall weight: 40 g.
A small sensor network constituted by one receiver and several vibration sensors with specific addresses was developed and successfully tested.
The communication range was successfully tested up to 100 m (14 dBm transmission power).
The vibration module was tested and calibrated on a vibrometer shaker stage.
72 h battery life with continuous transmission (15 mA current consumption).
System user application
An application is available to configure all device parameters throug a window interface, where in real-time we can keep on an eyes on all acceleration data, the battery level and the RF power receive by the module and received by the receiver.
Vibration module installation with drone on bridge
The modules are attached on the concrete bridge surface by exploiting an UV curable glue. A magnate inside the vibration module package is used to easily fix and release the item from the drone.
Every vibration module communicates bidirectionally with on ground receiver. The user can set the measurement parameters (acceleration range, filter, measurement axes, etc.) and the module starts transmitting the data that are received and saved.
While the amplitude of acceleration peaks was influenced by road traffic during data acquisition, the structural vibration modes of the bridge could still be readily obtained. This was achieved through a straightforward application of the Fast Fourier Transform (FFT) on the recorded acceleration data, resulting in modes below 2 Hz. Monitoring the structural vibration modes of a bridge is a fundamental practice in civil engineering that contributes significantly to the safety, longevity, and performance of these critical infrastructure assets. By analyzing the vibration modes, engineers can assess the overall integrity of the bridge. Detecting changes in mode shapes or frequencies can indicate areas of potential weakness or degradation, prompting timely maintenance or repair.
Acceleration amplitude Z axis
FFT of Z acceleration axis
RVM drone.mp4Video of drone installation on bridge
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