Rotor Blade Displacement and Load Estimation with Fiber-Optical Sensors for a Future Health and Usage Monitoring System

Fiber-optical sensors have great potential in rotorcraft applications since they are small and robust in corrosive and electromagnetic environments. In addition, redundant configurations are easily realizable. Recent advances in the size and maturity of measurement equipment enables fiber-optical sensors and the interrogator to be placed even in the rotating system itself. For future Health and Usage Monitoring Systems, they can collect important data in locations where other types of sensors would not be feasible. In this paper, a method is presented for using fiber-optical sensors to identify elastic blade movements based on surface-strain measurements. With this method, it is possible to calculate the displacement and bending moment of the structure with great accuracy. Furthermore, blade properties like the neutral axis and bending stiffness can be determined at cross sections where fiber-optical sensors are located. Test campaigns were conducted on a non-rotating rotor blade test bench and Monte-Carlo simulations were performed to assess the model's sensitivity to its inputs. One of the advantages of the method is that only the location and orientation of the sensors need to be provided and no further input, such as an FE model, is needed.