Testing of a Fiber-Optical Sensor System for Rotor Blade HUMS

As a prerequisite for the development of HUMS (health and usage monitoring systems) using blade displacement and sectional force estimation in forward fiight, rotor blades are instrumented with FBG (fiber Bragg grating) sensors at the Institute for Helicopter Technologies & VTOL at the Technical University of Munich. Utilizing 60 directional strain measurements, it is possible to reproduce the strain field of five sections along the uniform airfoil. Thermographic scan methods and CT (computed tomography) scans are investigated to determine the precise sensor locations and to reproduce a three-dimensional model. Improvements can be seen when comparing results obtained from static deformation tests. In addition, sectional stiffness terms are derived, and an experimental modal analysis is carried out. With the scope of state observation on the MERIT (Munich Experimental Rotor Investigation Testbed) test rig at the TU Munich a measurement environment is established using an optical data transmission to extract strain signals from the rotating system. The first investigations show the potential of optical strain measurements in the rotating systems for various applications.