Mode Shape Identification and Orthogonalization
Abstract
Accurate structural dynamic models of complex spacecraft are a requirement. Unfortunately, analytical models agree closely with properly measured mode data only in the first few modes. To minimize the effects of this deficiency, two approaches are widely used. The first approach is to adjust the analytical dynamic model to improve correlation between the analytical and empirical modes. The second approach also involves adjusting the analytical model to improve correlation with the measured modes. An identification procedure to improve the mass-weighted orthogonality of measured mode shapes is introduced. The procedure takes into account the degree of mode isolation present during measurement. This is accomplished by establishing a set of new mode shapes, from the measured vectors, that satisfy cross-orthogonality constraints and are a minimum deviation from the measured data. A significant feature is that each measured mode, from which improved modes are identified, can be established using different excitation locations and force levels. This allows the procedure to improve the isolation of modes measured with multi- shaker, sine dwell testing techniques. Keywords: Dynamic models; Mode shapes; Identification, Orthogonalization, Experimental, Sine Dwell.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 29, 1988
- Accession Number
- ADA202279
Entities
People
- Alvar M. Kabe
Organizations
- The Aerospace Corporation