Simple pressure sensor for a vehicle seat using a woven polymer optical-fiber sheet

We developed a textile pressure sensor sheet for a vehicle seat by weaving polymer optical fibers (POFs). The vehicle-seat pressure sensor was fabricated in the form of a sheet by weaving POFs and fiber yarns. The weaving was performed in the form of a mesh structure so that intersections occurred between the woven POFs. When incident light from a light source passes through the inner POF sections of the textile pressure sensor, it suffers optical losses owing to bending at the intersection regions, and these losses linearly increase with increasing applied pressure. The curvature and the deformation occurring in the intersection regions were analyzed by using a multiphysics tool, and the results were optically analyzed by using a 2D Beam propagation method. The analysis results indicated that a curvature of approximately 135 mm occurred, assuming that a pressure of 4 kPa occurred when a maximum load of 100 kg was applied to the vehicle seat. The areas for analyzing were selected on the basis of the results from the curvature analysis. The results from analyzing the curvatures, which ranged from 200 to 1000 mm, indicated that a maximum loss of approximately 1.2 dB occurred. A linear increase in the optical losses with increasing pressure was experimentally confirmed for the woven textile pressure sensor, and a vehicle textile sensor with a low-cost Photodiode (PD) was developed by considering the soft characteristics of the vehicle seat and analyzing the multiple POF intersection regions.