Infrared for Estimation of Relative Foot Distance

Instrumented Force Shoes™ (Xsens) was used in the INTERACTION project, to monitor gait and balance measures in stroke subjects [1]. The issue of drift in foot position estimation by Inertial Measurement Units (IMUs) is corrected by Ultrasound (US), which offers relative feet distance estimation [2]. However, the US system suffers from some limitations such as synchronization between transmitter and receiver module placed on either foot, and ambience temperature. Other sensor systems including Stereo-photogrammetry, LIDAR, and magnets have been studied for relative feet distance estimation [3], [4]. However they suffer from limitations such as portability, and need for reference systems. Reflective methods using Infrared (IR) systems for distance sensing does not suffer from the above limitations and is also portable. However, studies using them either incorporate heavy systems or show large mean errors [5]. Therefore, a better distance estimation model for IR systems is required. In this study, an IR system - ZX Distance Sensor, is used. The sensor provides the location of the reflecting surface in 2-D. The sensor is placed on one foot and a reflective tape is used on the other. Simultaneously, distance is estimated using an US system. These distances and the outputs of the IR system are used to obtain a model that relates these quantities. The study is performed for stationary and walking cases, and the accuracy of the models will be studied. The study is a part of project 7 of NeuroCIMT, funded by the Dutch National foundation STW. REFERENCES [1] B. Klaassen, B.-J. F. van Beijnum, M. Weusthof, D. Hof, F. B. van Meulen, Ed Droog, H. Luinge, L. Slot, A. Tognetti, F. Lorussi, R. Paradiso, J. Held, A. Luft, J. Reenalda, C. Nikamp, J. H. Buurke, H. J. Hermens, and P. H. Veltink, “A Full Body Sensing System for Monitoring Stroke Patients in a Home Environment,” Commun. Comput. Inf. Sci., vol. 511, pp. 378–393, 2016. [2] D. Weenk, D. Roetenberg, B.-J. F. van Beijnum, H. Hermens, and P. H. Veltink, “Ambulatory Estimation of Relative Foot Positions by Fusing Ultrasound and Inertial Sensor Data.,” IEEE Trans. Neural Syst. Rehabil. Eng., vol. 4320, no. c, pp. 1–10, 2014. [3] D. Roetenberg, P. Slycke, A. Ventevogel, and P. H. Veltink, “A portable magnetic position and orientation tracker,” vol. 135, no. 2, pp. 426–432, 2007. [4] M. Teixido, T. Palleja, M. Tresanchez, M. Nogues, and J. Palacin, “Measuring oscillating walking paths with a LIDAR,” Sensors, vol. 11, no. 5, pp. 5071–5086, 2011. [5] T. N. Hung and Y. S. Suh, “Inertial sensor-based two feet motion tracking for gait analysis.,” Sensors (Basel)., vol. 13, no. 5, pp. 5614–5629, 2013.