SECANT-METHOD ADJUSTMENT FOR STRUCTURAL MODELS

On-orbit testing will be required for final tuning and validation of any mathematical model of large space structures. Identification methods using limited response data to produce optimally adjusted property matrices seem ideal for this purpose, but difficulties exist in the application previously published methods to large space truss structures. This article presents new stiffness matrix adjustment methods that generalize optimal-update secant methods found in quasi-Newton approaches for nonlinear optimization. Many aspects of previously published methods of stiffness matrix adjustment may be better understood within this new framework of secant methods. One of the new methods preserves realistic structural connectivity with minimal storage requirements and computational effort. A method for systematic compensation for errors in measured data is introduced that also preserves structural connectivity. Two demonstrations are presented to compare the new methods' results to those of previously published techniques.