Estimation of Forward Tilt Angle during Wheelchair Use Considering Back Curvature

This study proposes a method of estimating the forward tilt angle using an illuminance sensor, focusing on changes in the illuminance value of the seat surface due to changes in the posture during wheelchair use, for the purpose of preventing wheelchair accidents. The effectiveness of the proposed method was tested by fixing the position of the wheelchair and installing an illuminance sensor at the center of the rearmost part of the seat surface. The proposed equation was proposed by measuring illuminance values using a board as a preliminary experiment, and then three healthy subjects measured illuminance values five times per person as in the preliminary experiment and compared them with the proposed equation. The comparison showed that the proposed equation and the measured values had errors due to the curvature of the back, so a correction method that takes into account the curvature of the back during forward tilt was studied and the results were discussed. The results showed that the proposed correction method reduced the error of the forward tilt angle on average, and the error accuracy of the forward tilt angle estimation was within 3 °, with an average error reduction rate of approximately 23.5%.