Multibody dynamics: Modeling component flexibility with fixed, free, loaded, constraint, and residual modes

The assumed-modes method in multibody dynamics allows the elastic deformation of each component in the system to be approximated by a sum of products of spatial and temporal functions commonly known as modes and modal coordinates respectively. The choice of component modes used to model articulating and non-articulating flexible multibody systems is examined. Attention is directed toward three classical Component Mode Synthesis (CMS) methods whereby component normal modes are generated by treating the component interface (I/F) as either fixed, free, or loaded with mass and stiffness contributions from the remaining components. The fixed and free I/F normal modes are augmented by static shape functions termed constraint and residual modes respectively. A mode selection procedure is outlined whereby component modes are selected from the Craig-Bampton (fixed I/F plus constraint), MacNeal-Rubin (free I/F plus residual), or Benfield-Hruda (loaded I/F) mode sets in accordance with a modal ordering scheme derived from balance realization theory. The success of the approach is judged by comparing the actuator-to-sensor frequency response of the reduced order system with that of the full order system over the frequency range of interest. A finite element model of the Galileo spacecraft serves as an example in demonstrating the effectiveness of the proposed mode selection method

Optical pathlength control on the JPL Phase B interferometer testbed

Design and implementation of a controller for optical pathlength compensation on a flexible structure is presented. Nanometer level pathlength control is demonstrated in the laboratory. The experimental results are in close agreement with performance predictions

Driftwoodsman

Driftwoodsman A robot with musclesestablished his thresholdsand balanced his mesh molds.His thoughts and his lights bulged. He was young again,new with friends,learning thingsbeyond his ken,a fast frontiersman,the first to fear Them,but last to leave Them,those solid steersmen, piersmen

There Is an Unformed World in the Sky of My Heart

“There is an Unformed World in the Sky of My Heart” contains works of poetry, fiction, and non-fiction. All the pieces were written after my conversion to Christ in December 2012 and before my graduation from Cedarville University in May 2015. Though my spiritually-themed poems are the pulse of this portfolio, the title refers to the fantasy world of Sembercron, which I am discovering and creating through my writing. The title also refers to heaven growing in my heart, or Christ’s image supplanting my own, or God sanctifying me for his purposes. This portfolio observes, explores, and delights in this sanctification