An Automated Method For Identification of Efficient Measurement Degrees-of-Freedom For Mode Survey Testing

An automated method has been developed for identifying mode survey test measurement degrees-of-freedom (DOFs). The method has been shown to be an effective tool for identifying efficient sets of test measurement locations. The automated approach is based upon two established methods for measurement DOF identification, Residual Kinetic Energy (RKE) and Effective Independence (EI). The RKE method is here extended to an iterative application, called Iterative Residual Kinetic Energy (IRKE), that can generate a candidate measurement set with little input beyond the analytical structural model. The IRKE method requires an initial measurement set, which can be as small as a single DOF. By requiring only a single DOF to seed the IRKE method, the effort to create an initial set based on engineering judgment, or other methods, is eliminated. This paper proposes the use of the IRKE algorithm for the development of relatively large candidate measurement sets of sizes, which are themselves impractical for test instrumentation purposes, but can then be reduced to a manageable number by utilizing a variation of the EI method designated the MassWeighted Effective Independence (MWEI) method. MWEI improves upon the EI method by application of mass-weighting to the modal matrix and using the EI method on the product of the reduced mass matrix and the modal matrix. The use of the IRKE and MWEI methods jointly affords analysts an automated tool for identification of efficient mode survey test measurement DOF sets.