Feasibility study of a novel load detection system for train doors based on the acoustic characteristics of elastic tubes

Abstract

Pinching accidents involving thin bags, canes used by the blind, or stroller wheels are a serious problem. To date, only a few studies have investigated the anti-pinch system of train doors. Hence, this paper proposes a novel pinching sensor that utilizes the acoustic characteristics inside an elastic tube. To investigate whether a highly sensitive sensor can be realized, the sensitivity was experimentally measured. In particular, we investigated whether a displacement of 1 mm can be detected along door rubber tubes, with a length of 2200 mm. First, we conducted load detection experiments for a conventional door rubber tube with an inner diameter of 15 mm. The sensor system comprises an earphone, a microphone, and an elastic tube. By adopting sweep signals of 0.5–4.5 kHz, power spectra inside the rubber were obtained, and the position responses were calculated via Fourier transform. Subsequently, we determined the applied loads based on the peak ratios. The subtraction method was adopted to detect small displacements (=1 mm). The obtained results indicated that displacements of 1 mm could be detected from 100 to 1400 mm. Next, load sensing experiments were conducted using five different types of door rubber tubes, and the obtained results indicated that the proposed method can be applied to both the widely used rubber tube, as well as in other types of door rubber tubes. Based on these results, we verified that the proposed system can be adopted as a highly sensitive pinching sensor system.