Abstract
This study presents a radar-based remote measurement system for classification of human behaviors and falls in restrooms without privacy invasion. Our system uses a dual Doppler radar mounted onto a restroom ceiling and wall. Machine learning methods, including the convolutional neural network (CNN), long short-term memory, support vector machine, and random forest methods, are applied to the Doppler radar data to verify the model’s efficiency and features. Experimental results from 21 participants demonstrated the accurate classification of eight realistic behaviors, including falling. Using the Doppler spectrograms (time–velocity distribution) as the inputs, CNN showed the best results with an overall classification accuracy of 95.6% and 100% fall classification accuracy. We confirmed that these accuracies were better than those achieved by conventional restroom monitoring techniques using thermal sensors and radars. Furthermore, the comparison results of various machine learning methods and cases using each radar’s data show that the higher-order derivative parameters of acceleration and jerk, and the motion information in the horizontal direction are the efficient features for behavior classification in a restroom. These findings indicate that daily restroom monitoring using the proposed radar system accurately recognizes human behaviors and allows early detection of fall accidents.
Highlights
IntroductionThe comparison results of various machine learning methods and cases using each radar’s data show that the higherorder derivative parameters of acceleration and jerk, and the motion information in the horizontal direction are the efficient features for behavior classification in a restroom
The convolutional neural network (CNN) method achieved the best accuracy of 95.6%, indicating that the spectrogram images were more effective than the spectrogram envelope [16] or motion parameter-based approach for human behavior and fall classification in restrooms
This study used Doppler radar technology to classify the behaviors and falls in a restroom based on machine learning approaches
Summary
The comparison results of various machine learning methods and cases using each radar’s data show that the higherorder derivative parameters of acceleration and jerk, and the motion information in the horizontal direction are the efficient features for behavior classification in a restroom These findings indicate that daily restroom monitoring using the proposed radar system accurately recognizes human behaviors and allows early detection of fall accidents. Monitoring systems for early detection of accidents and abnormal behaviors in elderly adults, such as falling, have recently been developed based on sensors and Internet-of-Things technologies [2]. Such systems are not used inside restrooms due to privacy concerns.
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