IDENTIFICATION, APPLICATIONS, AND DYNAMIC ANALYSIS OF NONLINEAR SPACECRAFT COMPONENTS

摘要

Spacecraft structures are generally linear, but some structural components and mechanisms reveal nonlinear characteristics; They are either unwillingly present, like nonlinear stiffness and damping in joints, play in bearings, f.i., or they are specially designed for damping and shock absorbing purposes, For systems that can be reasonably reduced to only few degrees of freedom (local nonlinearities) methods which can be applied with reasonable effort are explained to identify the force/displacement and damping characteristic by static and sine sweep tests. The analytical treatment is based on Fourier expansions that include quasi-static accelerations and higher harmonics to cover shifts in the point of operation and subharmonic resonances. Conclusions are drawn for the design of nonlinear components and applied to actual spacecraft hardware, such like micro-g-isolators and shock absorbing elements. Problem areas like the determination of the damping and spring coefificients, f.i., will be treated. Reservations and limitations of traditional test philosophies and methods will be shown, some contributions to improved concepts will be made.