A COMPARISON OF MODAL TEST PLANNING TECHNIQUES: EXCITATION AND SENSOR PLACEMENT USING THE NASA 8-BAY TRUSS

摘要

A comparative study of several pre-modal-test planning techniques is presented using the NASA 8-bay truss as a test bed. Kinetic energy, average kinetic energy, eigenvector product, and driving point residue techniques are used to place excitation devices on the 8-bay truss. A numerical simulation is performed to evaluate the effectiveness of each technique to excite the first five target modes of the structure. A cross-orthogonality check between the identified and finite element modes is performed in addition to a frequency match comparison. Effective independence, kinetic energy, average kinetic energy, and eigenvector product techniques will be used to place sensors on the 8-bay truss, which will best identify the first five modes of vibration. The structural response of the truss will be numerically simulated and measured at those degrees of freedom (DOFs) corresponding to the sensor locations obtained using the various techniques. The eigensystem realization algorithm (ERA) will then be used to evaluate the effectiveness of each sensor set with respect to modal parameter identification. A set of three hundred random sensor locations is generated and evaluated to give a basis of comparison for the four sensor location techniques evaluated. The cost effectiveness of each of the excitation and sensor selection techniques will be evaluated.