Yunis, I. | Search NASA

NASA NTRS1991

Simulation of Space Station loads with active control systems

A methodology for calculating dynamic loads for the Space Station Freedom is presented. The methodology minimizes the repeated calculation of duplicate structural elements, while analyzing a large number of different Space Station configurations with different alpha and beta joint angles. Particular attention is paid to the issue of model reduction using a combination of component mode synthesis (superelements) and component mode selection to generate accurate system level models with a minimum of modal degrees of freedom. The modeling of the control systems during simulation of the structural response is discussed.

Blelloch, P. A.↗

NASA NTRS1990

Control/structure interactions of Freedom's solar dynamic modules

The purpose of this paper is to address potential control/structures interaction (CSI) problems of large flexible multibody structures in the presence of pointing and tracking requirements. A control approach is introduced for the simultaneous tracking and vibration control of multibody space structures. The application that is discussed is Space Station Freedom configured with solar dynamic (SD) modules. The SD fine-pointing and tracking requirements may necessitate controller frequencies above the structural natural frequencies of Freedom and the SD modules. It is well known that this can give rise to CSI problems if the controller is designed without due consideration given to the structural dynamics of the system. In this paper, possible CSI problems of Freedom's solar dynamic power systems are demonstrated using a simple lumped mass model. A NASTRAN model of Freedom developed at NASA Lewis is used to demonstrate potential CSI problems and the proposed tracking and vibration control approach.

Quinn, R. D.↗