A Motion-Tracking Ultrasonic Sensor Array for Behavioral Monitoring

The application of Kalman filtering to track subjects' movements during a behavioral experiment is discussed. Specifically, an overhead array of wireless, ultrasound sensors automatically tracks the position of a parent, child, and stranger over a 4.45 m × 4.23 m observation area. This WiPsy (Wireless sensors for Psychology research) system provides accurate, real-time quantitative metrics for psychological evaluation in lieu of traditional qualitative manual coding. Moreover, tracking subjects using ultrasound sensors is less error-prone than existing methods that track based on human coding of video. In particular, the Kalman filter, which forms the core of this tracking system, can locate targets with a mean square error of about 1.3 m
²
. Overall, WiPsy strives to streamline data acquisition, processing, and analysis by providing previously unavailable assessment parameters.