Abstract
Estimating state of health of machines using vibration signals analyzed with complex deep-learning models poses memory and processing speed constraints for edge implementation, while cloud-based computing poses high latency, high cost of data transmission and storage and privacy threats. Moreover, in most practical settings, a large amount of data may be available or easily obtainable for machines in healthy/normal operating condition, and not in anomalous conditions. Thus, there exists a need to develop lightweight unsupervised learning based algorithms that can be implemented on an embedded platform for data processing and estimating state of health. In this work, we present a lightweight convolutional autoencoder (CAE) implemented on a low-cost FPGA platform (PYNQ-Z2, Xilinx Zynq 7020 SoC) to discern anomalies in vibration data sets. We present extensive performance analysis of various encoding methods to represent 1D time series as images, and feasibility analysis of FPGA-implementation of CAE. The optimized model has less than 10000 trainable parameters and shows highest accuracy (>88% on CPU, >85% with fixed point arithmetic on FPGA) using scalogram encoding when trained and tested on the Airbus SAS helicopter accelerometer data set.