Showing papers on "Model order reduction published in 1981"

Modal Truncation for Flexible Spacecraft

Abstract: A hierarchy of dynamical models is identified for large nonspinning flexible spacecraft. At each level, techniques are explained for reducing the order of the model before proceeding to the next level. These techniques have in common the presupposition that the model has at each stage been expressed in terms of its natural modes, some of which can, if necessary, be deleted based on the evaluation of one or more of the quantitative criteria proposed. These criteria are based on insights from several different perspectives, including inertial completeness, frequency relationships, controllability and observability considerations, and the contributions of individual modes to a mission-dependent cost functional (modal cost analysis). With the aid of these criteria, many of the engineering judgments related to model order reduction can be made on a rigorous quantitative basis.

Geometric structures in systems theory

Abstract: The predominance of linear models in systems theory has tended to obscure the natural structure possessed by given nonlinear physical systems, either through linearisation, model order reduction, or choice of co-ordinates. The purpose of the paper is to motivate the reintroduction of geometric structure into systems theory. First, a brief introduction to the more common geometric structures is given, also showing their linear counterparts. It is then shown how these structures arise in systems theory by introducing the nonlinear control problems involved with mechanical manipulators, electrical networks, rotating electrical machinery and attitude control of spacecraft. The paper is concluded by considering the application of some of the geometric structures to nonlinear Hamiltonian and potential input/output systems.