The use of unobtrusive sensors for physiological monitoring is growing in popularity. With advantages such as their noncontact nature plus limited physical and cognitive load on the user, unobtrusive sensors will likely increase acceptance and usefulness in biomedical monitoring. Biomedical applications for unobtrusive pressure sensors include the analysis of bed transfer sequences and the extraction of breathing rate during long-term trend analysis and health monitoring. This paper proposes an algorithm to measure torso movement using an unobtrusive pressure-sensor array. This work makes use of the information captured by measuring the respiratory-signal delay between sensors in the array. The novel contributions are using cross-correlation to realign polarity-adjusted signals from a pressure-sensor array and to create a map of delays across the torso. Not only is the advantage in adjusting the polarity of inverted signal clearly demonstrated, but in many cases, the realignment according to the delay increases the signal amplitude and further improves the signal-to-noise ratio in many cases. The map of delays between the pressure sensors' signals reveals important information about movement timing in the torso while breathing.

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Keywords Biomedical measurements, biomedical monitoring, component, delay effects, pressure measurement, timing, unobtrusive
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Journal IEEE Transactions on Instrumentation and Measurement
Townsend, D.I. (Daphne I.), Holtzman, M. (Megan), Goubran, R, Frize, M, & Knoefel, F. (2011). Measurement of torso movement with delay mapping using an unobtrusive pressure-sensor array. In IEEE Transactions on Instrumentation and Measurement (Vol. 60, pp. 1751–1760). doi:10.1109/TIM.2010.2092872