Vehicle Occupant Detection and Vital Sign Monitoring Based on Random Body Movement Correction Using Millimeter-Wave Radar

In this work, a combined system for vehicle occupant detection and noncontact vital sign monitoring is proposed, which can be used in the automotive industry. First, occupant detection and radial range-azimuth positioning method based on frequency-modulated continuous wave (FMCW) radar is applied. By separating the radar echoes of multiple life targets, the intermediate frequency (IF) signals containing vital sign micromovement information of each passenger’s chest are extracted. Then, the successive variational mode decomposition (SVMD) algorithm is used to decompose and reconstruct the breathing and heartbeat signals of each passenger. Furthermore, we propose an IF signal speed compensation method to eliminate the impact of random body movement (RBM) on vital signal extraction. Our system can successfully extract the breathing and heartbeat signals of multiple passengers in the cabin. The average estimation accuracy of the breathing rate (BR) and heart rate (HR) of a single target in different physical states at a distance of 1.5 m can reach 91.6% and 91.9%, respectively, and the proposed RBM correction algorithm can significantly improve the distortion of vital signals caused by radial RBM.