iMagiMat Smart Carpet: POF Layer to Detect Gait and Mobility

The iMagiMat smart carpet uses a grid of plastic optical fibers to image footsteps and measure gait and mobility. The paper was presented at the 2015 POF conference in Nuremberg.

Presented at the 24th International Conference on Plastic Optical Fibres (POF 2015) in Nuremberg, Germany, in September 2015, the paper describes the iMagiMat Smart Carpet, a tomography-based sensor system built from polymer, or plastic, optical fiber (POF) that images the real-time deformation exerted by human footsteps to assess the gait and mobility of individual walkers. It was written by a team from the University of Manchester, with Patricia Scully as first author and Krikor Ozanyan as last; Dr. Costilla Reyes was in his first year of doctoral research.

Light travels along each optical fiber, and a small bend or squeeze changes how much of it is transmitted. In iMagiMat, a sensing grid of thin Toray POF elements is embedded within the carpet surface, so a footstep alters the transmission of the fibers it presses on. Tomography is the technique of reconstructing an image from many such line-by-line measurements; here an inverse tomography solver turns the grid’s changes in transmission into an image of the deformation the foot produces. Because the fibers are embedded in the floor, the person being measured does not have to wear or carry anything, which suits the study of mobility in everyday settings.

The paper reports progress on several fronts: a fast calculation of each footprint’s center of mass, which is related to the center of pressure and to ground reaction force; the suitability of machine-learning techniques for extracting gait parameters, the strand Dr. Costilla Reyes developed; and an evaluation of iMagiMat against more conventional instruments, namely the GAITRite walkway, force plates, and inertial motion sensors. Comparisons of this kind are how a new sensor is shown to agree with established instruments before it is used in practice.

The work continued in the group’s 2016 paper on the POF sensing grid’s signal analysis, in Dr. Costilla Reyes’s IEEE SENSORS 2015 paper on temporal pattern recognition for gait analysis with an “intelligent carpet,” and in his University of Manchester PhD thesis.