Fiber optic sensors monitoring transmission ring gears

Internal components of the planetary stage of a helicopter transmission have proven difficult to diagnose due to the complex geometry of the gearbox and the inability to place sensors inside the planetary gear system. The goal of the research presented in this paper is to use fiber optic sensors to monitor the strain response of planetary gears on the surface of the ring gear. As the planetary gears traverse the locations of the fiber optic strain sensors, a local strain profile will be recorded. By synchronous data processing of the strain profiles of each planetary gear, an average response signal will be generated. Deviations from the average response profile will provide an indication to the existence of damage within the planetary stage. This paper will present results from experiments conducted on a transmission test rig at the University of Maryland. Fiber Bragg grating sensors were selected because of their multiplexing capabilities and localized strain measurement attributes. Initial test results have proven the feasibility of using FBG sensors to monitor the strain response due to the planetary stage. Research to be conducted includes the development and application of advanced damage detection algorithms that take advantage of the novel attributes of this approach.