Time domain-based identification of mechanical characteristics of supporting elements

Resumo

This paper addresses the problem of identifying the mechanical characteristics - inertia, stiffness and damping - of supporting elements of vibrating structures using dynamic responses. A feasibility study is presented on a method operating in the time domain, whose implementation comprises two basic steps: in the first step, the effect of the supports is represented as external forces applied to the dismounted configuration. These forces are identified by inversion of the time domain multi-input-multi-output transfer relation. The force identification method requires, as experimental data, the acceleration time responses measured at a given set of coordinates of the mounted configuration, including the support locations, and a set of impulse response functions relating measurement and excitation coordinates. In the second step, the equations of motion of the supports, which are modeled as SDOF systems, are used for estimating the values of the unknown physical parameters. The paper is organized as follows: the basic formulation related to the two steps mentioned above is first presented. Then, ill-conditioning of the force identification computations is discussed and the conjugate gradient algorithm, which is used for obtaining stable force estimates, is described. Finally, an application to a simple numerically simulated structure is presented to illustrate the main features of the method.