Sensor system for indirect sensing of deformation of flexible structures

A sensor system for sensing deformation of a flexible structure includes a beam structure that will be coupled to a surface of the flexible structure having a natural frequency fs, an axial strain εaxialstructure, and a shear strain εxystructure associated therewith. The beam structure has an axial strain εaxialbeam and a shear strain εxybeam associated therewith. The beam structure satisfies criteria defined by minimization of a root mean square difference between εaxialstructure and εaxialbeam and minimization of a root mean square difference between εxystructure and εxybeam. Fiber optic strain sensors are coupled to and distributed in a spaced-apart fashion along the beam structure. The beam structure is more flexible than the flexible structure such that a combination of the beam structure, the fiber optic sensors, and the flexible structure has a natural frequency fc defined by (0.95)fs≤fc≤(1.05)fs.