Advances in fiber optic shape sensing developed at NASA's Armstrong Flight Research Center are enabling the development of next-generation flexible aircraft wings that maximize structural efficiency and reduce weight, improving fuel efficiency. These same advances will help engineers design stronger bridges, buildings, ocean vessels, and more.
Armstrong's technologies provide a convenient way to calculate distributed deformed orientation angles — that is, roll, pitch, and yaw — as well as determine the deformed shape of an object in 3D space. Developed to facilitate monitoring and control of flexible aircraft designs when used in conjunction with Armstrong's multi-patented FOSS technology, these new tools improve shape-sensing accuracy for highly deformable structures such as bridges, wind turbines, robotic instruments, and much more. These tools also can be integrated into commercial fiber optic sensing systems.
Fast algorithms use distributed fiber optic wavelength data to determine shape deformation of large curved and flexible structures. Dramatically improving upon earlier two- and three-dimensional (2D and 3D) shape-sensing tools by tracking multiple orientation angles — displacement, twist, and rotation — at the same time, Armstrong's technology converts distributed surface strain data into deformed shapes that can be displayed and analyzed in real time.
Researchers developed a technology that uses curved displacement transfer functions to determine 3D shape and calculate the operational load of a structure. It works by dividing the structure into multiple small domains, whose junctures match sensing stations, so that data is collected in a piecewise, nonlinear fashion. The innovation calculates structural stiffness (bending and torsion) and operational loads (bending moments, shear loads, and torques) in near real time.
The method tracks rotations and orientation by employing quaternion mathematical operations, a faster process than rotation matrices used in previous shape-sensing algorithms. The result is an algorithm that can track multiple angles — displacement, twist, and rotation — at the same time to enable curvilinear shaping sensing. Armstrong researchers have validated the method on the large-scale passive aeroelastic tailored (PAT) wing.
These new technologies advance the ability of fiber optic sensing systems to determine the shape and operational loads of nonlinear flexible surfaces. They can improve the structural integrity of a range of large structures and provide highly accurate critical information in real time, enabling corrective action to avert disasters.