Design, Fabrication, and Model Development of a Spacecraft Test-Bed for Six-Axis Active Vibration Isolation and Precision Pointing

摘要

This thesis describes the design, fabrication, model development, and model verification for a test-bed that simulates a mechanically noisy spacecraft bus. The test-bed includes an aluminum node-and-strut truss structure, articulating solar arrays, electromagnetic shaker mounts, attachment points for fuel tanks, and a soft spring suspension system to simulate a 0-g environment. A detailed finite element model of the system was developed, and experimental modal analysis coupled with model updating techniques was used to verify and improve the finite element model for the spacecraft test-bed. Model updating reduced the average error in the first twelve flexible modes of the system from 3.7% to 1.3%. The University of Washington is currently investigating the benefits of active vibration isolation and precision pointing for the next generation of spacecraft. Research with such devices is important because the performance of multiple satellite clusters, applicable to communications and Earth and Space Science missions, requires an upgrade from RF to optical cross- links. With this upgrade comes a 10,000-fold increase in pointing requirements, which cannot be met with conventional methods. Current research utilizes multivariable control of a six-axis active vibration isolation and pointing device, or hexapod. The newly developed spacecraft test-bed can simulate realistic disturbance inputs on the noisy side of the hexapod to investigate its effectiveness in a more realistic setting. Such disturbances include reaction wheel imbalances, fluid slosh, and vibration from mechanical devices such as solar array drives.