Controls-Structures Interaction (CSI) is a program dedicated to reducing vibrations in spacecraft through structure optimization coupled with active and passive vibration control. The Engineering Design Branch supports this program by maintaining the CSI Evolutionary Model (CEM). It is a truss structure that can be modified to dynamically simulate different spacecraft. The model is now configured to simulate the Earth Observing System (EOS)-AMI spacecraft. Two flexible appendages dynamically interact with the main bus structure: a high gain antenna and a solar array mast. Up to three science instruments can be simulated using two-axis gimbals mounted to the bottom of the model. The simulated instruments pointing performance is measured by an optical scoring system that detects the angle a laser beam coming from the gimbal. The model can be actuated in several ways. Reaction wheels control attitude in pitch and roll. Active piezo-electric elements close to the gimbals suppress vibrations. Passive damping struts can be added. A zero gravity environment is simulated by the use of five pneumatic- magnetic suspension machines. These machines allow the model to essentially float on a cushion of air. The low spring rate of suspension machines simulates zero gravity in the vertical direction. The pendulum motion of five 70 feet long cables approximate zero gravity in the horizontal plane.
