Damage assessment using hyperchaotic excitation and state-space geometry changes

The current study explores the use of a steady-state hyperchaotic signal to probe a system for state-space geometry changes used for structural health monitoring applications. This is an extension of a previous chaotic interrogation technique approach that exploited the intrinsic high sensitivity of chaotic systems to subtle changes of the parameters. The enhanced technique proposed in this paper explores a novel structural excitation, namely a hyperchaotic excitation, which exhibits a chaotic behavior wherein at least two Lyapunov exponents are positive due to stretching of the phase space in multiple directions. A feature called average local attractor variance ratio (ALAVR), which is based on attractor geometry, is used to compare the geometry of a baseline attractor to a test attractor. The enhanced technique is applied to analytically and experimentally analyze the response of an 8-degree-of-freedom system to the hyperchaotic excitation for the sake of damage assessment. A comparison between the results obtained from current hyperchaotic excitation vs. a chaotic excitation highlights the higher sensitivity of the hyperchaotic excitation. Thus, hyperchaotic interrogation can be used as an alternative damage assessment technique when increased sensitivity to small amounts of damage is required.