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27 June 2006 SPHERES tethered formation flight testbed: advancements in enabling NASA's SPECS mission
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This paper reports on efforts to control a tethered formation flight spacecraft array for NASA's SPECS mission using the SPHERES test-bed developed by the MIT Space Systems Laboratory. Specifically, advances in methodology and experimental results realized since the 2005 SPIE paper are emphasized. These include a new test-bed setup with a reaction wheel assembly, a novel relative attitude measurement system using force torque sensors, and modeling of non-ideal tethers to account for tether vibration modes. The nonlinear equations of motion of multi-vehicle tethered spacecraft with elastic flexible tethers are derived from Lagrange's equations. The controllability analysis indicates that both array resizing and spin-up are fully controllable by the reaction wheels and the tether motor, thereby saving thruster fuel consumption. Based upon this analysis, linear and nonlinear controllers have been successfully implemented on the tethered SPHERES testbed, and tested at the NASA MSFC's flat floor facility using two and three SPHERES configurations.
© (2006) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Soon-Jo Chung, Danielle Adams, Alvar Saenz-Otero, Edmund Kong, David W. Miller, David Leisawitz, Enrico Lorenzini, and Steve Sell "SPHERES tethered formation flight testbed: advancements in enabling NASA's SPECS mission", Proc. SPIE 6268, Advances in Stellar Interferometry, 62680B (27 June 2006);

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