INTERPOLATION-BASED CONDENSATION OF ALGEBRAIC SEMIDISCRETE MODELS WITH FREQUENCY-RESPONSE APPLICATION

Condensation model reduction theory, a method of degree-of-freedom-eli mination for semi-discrete system models with response-prediction fide lity in the retained degrees-of-freedom (DOF), is applied to algebraic semi-discrete models. The condensation process makes use of an interp olation over a user-chosen subset, denoted as a ''window,'' of the set of continuous-independent-variable values. The window's ''size'' and ''location,'' as well as the accuracy of the method within the window, are hence controllable by the user. (There is a computational-cost ve rsus accuracy/window-size tradeoff for a given DOF reduction, as would be expected.) One target of this capability is the DOF reduction of s patially-discrete, continuous-time-transformed (Fourier, Laplace, etc. ) linear system models, for which the resulting semi-discrete model ha s frequency as the continuous independent variable. The window would t hen correspond to a selected frequency range, (a region of the complex frequency plane in the most general case). Another target of this cap ability is the DOF reduction of nonlinear, path-independent static or quasistatic models, for which the window corresponds to a region of th e reduced-DOF-model solution space itself. As a demonstration, the met hod is applied to the frequency response of a non-periodic linear elas tic laminate over a rectangular window in the complex frequency plane. It is seen that the frequency-response predicted by the reduced-DOF m odel at each of various values within the window, as well as the eigen values predicted by the reduced-DOF model within the window, agree wel l with the corresponding predictions of the original, full-DOF model.