Autonomous modal identification of the space shuttle tail rudder

Autonomous modal identification automates the calculation from experimental data of natural vibration frequencies, damping, and mode shapes of a structure. This technology complements damage detection techniques that use continuous or periodic monitoring of vibration characteristics. The approach incorporates the Eigensystem Realization Algorithm as a data analysis engine and an autonomous supervisor to condense multiple estimates of modal parameters using the consistent-mode indicator and correlation of mode shapes. The procedure was applied to free-decay responses of a Space Shuttle tail rudder and successfully identified the first seven vibration modes of the structure. The final modal parameters are a condensed set of results for 87 individual cases requiring approximately 5 min of computer time on a Unix workstation.