This document describes using both active and passive sensors for structural health monitoring. Passive accelerometers continuously collect data and trigger active piezo sensors when vibrations are detected. The piezo sensors then generate and receive guided waves to be analyzed for changes in travel time that could indicate damage. Both sensor types are embedded in a flexible PCB and smart polymer composite to monitor the structure. The goal is to detect potential failures by monitoring variations in wave travel times before damage occurs.

1. Active and Passive sensing for
structural health monitoring

2. Sensors employed
Accelerometers:
12 Bit resolution
188 ksps (dual channel)
I2C communication protocol
Piezo sensors:
1MHz frequency to excite guided waves
16 Bit resolution DAQ needed
Analog signals
Passive Sensors:
Active Sensors

3. Flexible PCB
Active and Passive sensors will be embedded in a flexible PCB
Embedded components
-> Sensors
->ADC
->Amplifier
->Conditioner

4. Smart Polymer
Flexible PCB will be embedded in a composite during
fabrication
Smart layer
Ordinary
Polymer
Accelerometers
PZT
Composite

5. Functional Unit
Passive Accelerometers
Piezo Transmitter
PiezoReceivers
Passive Accelerometers:
• Continuous operation.
• Data collected in a text file.
• Triggers the piezo sensors
when an event is detected.
Active Piezo Sensors:
• Data collection starts after
receiving the trigger.
• High speed data acquisition.
• Noise filtered and pulse
amplified before data
acquisition.

6. Working Methodology
Impact Vibration
Piezo
transmitter
triggered
Accelerometers
activated
Pulse
received by
piezo
receivers
Accelerometer data logging:
adc DAQ
Final data in a text file
Piezo sensor data logging:
Sensor Filter Amplifier
Final data collected by
DAQ in tabular format
Signal Processing

7. Aim of the experiment
Collected data will be used to calculate the travel time of material waves from transmitter piezo to
receiver piezo. As the material gets damaged, the variation in travel times will change and will alert
the user beforehand about a possible failure in the structure.
Damage in the polymer
T1
T2
T3
T4
T1 = T2 = T3 < T4

8. Combined application
Accelerometers:
->Passive sensors
->continuously sense for out of plane
accelerating due to impact
-> Moment the acceleration time signal cross
some outset provided by use
a) It will log the data in DAQ
b) Trigger a active piezo sensors
Piezo sensors:
->Based on input trigger from
acceleration sensor, Piezo will be
fired.
->Guided will be generated and
received by neighboring grid piezo
sensors.
-> High freq. data logging, signal
conditioning and amplifiers will be
designed and use to acquire high
SNR data
Both active and passive sensors are embedded as well as surface mounted