| Popis: |
Methods of human detection utilizing low-frequency (typically below a few hundred Hertz) seismic signals from footsteps are well known. Human footsteps generate broadband frequency vibration and sound signals from a few Hertz up to ultrasonic frequencies. The authors investigated the physical mechanisms involved in the generation of high frequency signals and the possibility of their application for human footstep detection. Striking and sliding contacts between a foot and the ground/floor produce the high frequency responses. The present paper introduces an approach for human motion detection using passive and active ultrasonic methods. The passive method employs an ultrasonic sensor that is sensitive to the sound from sliding contacts. The active method utilizes continuous wave ultrasonic Doppler sonar. Human motions have unique Doppler signatures and their combination with footstep vibration and sound signatures increases the probability of human presence detection and reduces false alarms. Test results for the detection of a walking person by the two methods, both indoors and outdoors, are presented and discussed. This work is supported by the Army Research Office under Grant W911NF-04-1-0190. |
