Multibin Breathing Pattern Estimation by Radar Fusion for Enhanced Driver Monitoring

Monitoring the status of the driver is a crucial aspect of health monitoring inside vehicles as it helps to identify potential health or safety risks that could affect a driver's ability to operate a vehicle safely. This includes monitoring for fatigue, distraction, or impairment, among other things, which can potentially cause car crashes. Although many solutions for health monitoring in private vehicles have been proposed, most of them are inconvenient to use or have the risk of leaking private information. Radars have the potential to address the above drawbacks by their inherent privacy protection and contactless operation in addition to their high accuracy, convenience, affordable price, and resilience to environmental factors. Among many possible radar configurations, millimeter Frequency Modulated Continuous Wave (FMCW) radars can accurately detect range and monitor displacements that are essential in breathing pattern monitoring. Breathing pattern monitoring is one of the key signatures of the driver's health. An accurate estimation of the breathing pattern enables the detection of breathing abnormalities, including Tachypnea, Bradypnea, Biot, Cheyne-Stokes, and Apnea. The breathing pattern can be estimated from both the chest and abdomen. For this purpose, we employed two 60-GHz FMCW radars. The proposed algorithm is capable of detecting the mentioned breathing abnormalities through breathing rate (BR) estimation and breath-hold period detection. In addition, the proposed method in this article estimates BR based on the multiple range bins. We conducted a study on the human radar geometry problem inside a vehicle to determine the accurate number of range bins for BR estimation. The experimental results demonstrate a maximum BR error of 1.9 breaths/min using the proposed multibin technique. In addition, the dual radar fusion system can detect breath-hold periods with minimal false detections.