Polyvinyl chloride reinforced soft silicone curvature sensor with optical fiber implantation

Soft curvature sensors have huge demand in the emerging field of soft robots, rehabilitative robots and morphing flight vehicles. However, the current soft sensors have limitations in sensitivity, repeatability, and fabrication cost, which hinder their practical applications. To address these issues, we propose a soft curvature sensor with soft silicone-polyvinyl chloride mixed substrate and fiber Bragg gratings (FBGs). The major contribution is obtaining a soft curvature sensor with extraordinary high sensitivity and repeatability. Using the pure bending model, the nonlinear relationship between the bending curvature and Bragg wavelength shift is analyzed. The reflection spectrums of the FBGs in the mixed substrate are measured, and the effect of the horizontal position and embedded depth of the FBG is analyzed experimentally. The optimal embedded position of the FBG and the sensitivity and repeatability of the soft curvature sensor is obtained. The results proved that the proposed sensor is soft enough to follow the contour of the object for real time measurement, the maximum sensitivity is up to 328.67pm/m−1 in the measurement range of 0m−1∼15m−1, and the fluctuation coefficient of repeated measurement is less than 0.07. The sensor is simple in structure, easy to fabricate and low cost. All these make it to be a promising approach for practical applications in the industrial and medical field.