Real-Time Stress Detection via Photoplethysmogram Signals: Implementation of a Combined Continuous Wavelet Transform and Convolutional Neural Network on Resource-Constrained Microcontrollers

TL;DR

This paper presents a real-time stress detection system using PPG signals, combining CWT and CNN on microcontrollers, achieving high accuracy while fitting resource constraints for wearable devices.

Contribution

It introduces a novel approach integrating CWT and CNN for stress detection on microcontrollers, with significant model size reduction techniques.

Findings

Achieved 93.7% accuracy in stress detection

Reduced model size to 1.6 MB for microcontroller deployment

Outperformed traditional signal processing methods

Abstract

This paper introduces a robust stress detection system utilizing a Convolutional Neural Network (CNN) designed for the analysis of Photoplethysmogram (PPG) signals. Employing the WESAD dataset, we applied Continuous Wavelet Transform (CWT) to extract informative features from wrist PPG signals, demonstrating enhanced stress detection and learning compared to conventional techniques. Notably, the CNN achieved an impressive accuracy of 93.7% after five epochs, post-implementation on a resource-constrained microcontroller. The optimization process, including pruning and Post-Train Quantization, was crucial to reduce the model size to 1.6 megabytes, overcoming the microcontroller's limited resources of 2 megabytes of Flash memory and 512 kilobytes of RAM. This optimized model not only addresses resource constraints but also outperforms traditional signal processing methods, positioning it as a promising solution for real-time stress monitoring on wearable devices.