An autoencoder-based deep-learning method for augmenting the sensing
capability of piezoelectric MEMS sensors in a fluid-dynamic system
Abstract
In this work, we present a deep-learning architecture to augment the
sensing capabilities of a micro electro mechanical system (MEMS) for
fluid mechanical applications. The MEMS sensor is composed of a
polyvinylidene fluoride flexible piezoelectric flag and a bluff body,
converting three-dimensional fluid mechanical energy flow into a
timedependent voltage signals. The developed deep learning method allows
for extracting accurate wind speed and classifying turbulences. The
bluff body generates vortexes which are not only the functions of the
bluff body’s geometry but also related to the fluid speed. These
vortexes induce a mechanical vibration into the attached piezoelectric
flag and hence generate charge displacement and an electrical voltage
signal. By placing the mentioned setup in a wind tunnel, we excited the
structure with various wind speeds while different combinations and
geometries of the bluff body and piezoelectric flag were considered. An
unsupervised autoencoder was used to extract the continuous manifold in
Fourier spectra of time domain voltage generated by the piezoelectric
sensor when the wind speed is continuously changed from 0 to 33 meters
per second. We found that this manifold is highly correlated with wind
speed. By adding another feed-forward network in parallel to the decoder
network of the autoencoder we also incorporated the measured wind speed
as the data’s label and could successfully use the system to extract the
wind speed, despite the sensor was placed under the strong turbulence
generated by the bluff body. We also investigated the ability of our
deep learning method to classify different bluff bodies from the voltage
harvested from the piezoelectric flag, finding that this unique cability
is resilient to the wind speed in the range. Such a system can be turned
into a system that fingerprints different turbulence and uniquely
differs them for various applications.