Floquet-SSI Methods for Real-Time Stability Monitoring and Correlation

Improved methods for real-time stability monitoring are needed in the rotorcraft industry to support the design and testing of new aircraft rotors, as well as updates to existing rotors. Current validated approaches require significant effort on the part of the user and can only be applied to a very specific data sequence. This combination of factors can be a significant cost driver in the development cycle. In this paper we demonstrate the combined use of Floquet analysis with Stochastic Subspace Identification (SSI) methods to address these deficiencies. This novel approach allows for the use of more robust subspace identification methods and provides an effective means of removing main rotor harmonics from the measured loads. All of this leads to highly accurate, precise and real-time estimates of rotor stability and modal data. These estimates can ultimately be used to "close the loop" in efforts to correlate computational structural dynamic simulation results with flight test and whirl stand test data, improving the fidelity of existing simulation models.