Kinematic State Monitoring for Flexible 3-D Beams Based on Fiber-Optic Strain Measurement

The compactness and lightweight of fiber-optic strain sensors make it possible to develop an efficient kinematic state monitoring method for flexible 3-D beams, which should be able to obtain the deformation state of the object structure in real time, and can be effectively applied in engineering fields like load identification and active attitude control. However, most of the existing research on Fiber-Optic Shape Sensing (FOSS) for flexible 3-D slender structures is based on simple strain-curvature conversion, which does not perform well in reconstructing torsion and limits the scope of application of shape sensing technology. These curvature-based studies also underestimate the ability of existing fiber-optic strain measurement technologies such as Optical Frequency Domain Reflectometer (OFDR) to obtain a more detailed deformation state of structures through dense measurements. In this work, Absolute Nodal Coordinate Formulation (ANCF) is introduced to describe the relationship between strain information obtained from fiber-optic strain sensors and the deformation state of the measured structure, and an effective kinematic state monitoring method is derived based on it. The numerical simulation carried out with ABAQUS shows that this method can effectively reconstruct deformation in multiple deformation modes such as bending-torsional coupling. Besides, the obtained kinematic trail is also close to the result obtained by ABAQUS. The high correlation between this method and ANCF makes it have explicit potential to be applied in engineering fields such as load identification and active attitude control.