Modeling, Simulation, and Analyses of Attitude Control for the Crew/Equipment Retriever (CER) Proposed for Space Station

摘要

The Crew/Equipment Retrieval System (CERS) is proposed for space station to provide the capability to rescue an EVA crewman or to retrieve equipment inadvertently detached from the station. This research is directed to model, simulate, and analyze attitude control for the Crew/Equipment Retriever (CER) with and without a target during autonomous attitude hold. Time-optimal and weighted-time-fuel optimal control laws are derived using Pontryagin's Minimum Principle. The CER baseline configuration is analyzed to accomplish some of the attitude control trade-off analyses planned for the CER preliminary design phase. Optimal thruster size and placement are evaluated for three-axis stabilization. Control stability when the moment of inertia tensor changes during target capture is evaluated for several worst-case scenarios. Attitude control performance results are computed through computer simulation. Simulation of the CER baseline configuration shows it does not provide effective control during capture of a worst-case 850 pound target. A new CER configuration scheme is proposed, evaluated to the baseline configuration. Fuel optimal and end-of-mission performance for the new CER configuration is evaluated. Simulation of the CER proposed configuration shows it provides effective control during target capture for modified locations in the capture net. Keywords: Attitude control systems; Optimal control; Force flyer; Space crews; Theses. (SDW)