Dynamic simulation of mechanical systems

Dynamic simulation has become a necessary tool in the design and analysis process of mechanical systems. This study is concerned with improving on the current technologies associated with the simulation of mechanical systems. One issue considered deals with the modeling of flexible components. Dynamic simulation packages often utilize the assumed modes approach for the modeling of flexible components. A relatively new idea in reduced component modeling is to generate reduced components based on the projection of system level modes onto the components. This approach yields component models that incorporate effects of the inboard and outboard boundary conditions. This methodology is extended to use Krylov system level modes in lieu of the conventional normal modes as a projection basis. Numerical results indicate that the reduced Krylov system provides an excellent alternative since it does not require the solution of the full-order eigenvalue problem.; This work also introduces a switched system to achieve order reduction for linear structural systems. The switched system model is derived based on modal participation factors calculated from an input forcing function and initial conditions at each switch step. Stability issues for switched systems are considered followed by the necessary conditions of stability for the proposed switched model. Numerical simulations demonstrate that an error indicator based on modal participation factors provides an effective switching strategy.; A second issue addressed is concerned with the numerical solution procedures for the governing equations of some mechanical systems. Resulting governing equations can be defined in a differential algebraic form and their solutions are often subject to constraint violation drift. In this work, constraint violation formulations are derived within the framework of nonlinear control theory. Using Lie algebraic methods, it is possible to interpret many constraint stabilization methods as nonlinear controllers. Alternatively, somewhat simpler constraint stabilization methods can be derived using energy integrals associated with the dynamical system. These interpretations present a framework that allows for the development of alternative stabilization methods that are simple and effective. A non-trivial numerical example is provided that considers constraint stabilization between two subassemblies: a highly maneuverable multiwheeled vehicle (HMMWV) and a weapon assembly.