Dual-layer orthogonal fiber Bragg grating mesh based soft sensor for 3-dimensional shape sensing

A soft shape sensor for 3-dimensional object shape measurement is demonstrated. The proposed sensor is based on dual-layer fiber Bragg grating arrays with an orthogonal mesh structure, which enables multi-point bi-directional shape sensing. The 3D shape reconstruction is based on a bi-directional curvature measurement at each sensing point, which is achieved through measuring the direction and amount of wavelength shift of each off-center embedded FBG. The conversion coefficient between the wavelength shift and bending curvatures is acquired and is used to convert the change in FBG to the corresponding bending curvatures and bending direction. The measurement error on the bending radius of each sensing point is about 2.7%. A 3D shape of the object surface is reconstructed with the help of a curve fitting method based on the curvature information across the whole FBG mesh. This design successfully achieved visualized 3D shape sensing, which has great practical value in soft robotics and biomedical applications.