Control of Tethered Satellite Systems in presence of Tether Failures

Paper number

IAC-07-C1.2.04

Author

Dr. Krishna Kumar, Ryerson University, Canada

Coauthor

Coauthor

Bo Tan, Ryerson University, Canada

Coauthor

G Godard, Ryerson University, Canada

Year

2007

Abstract

The advent of tethered satellite systems (TSS) marks the beginning of a new era in space research [1]. Several interesting space applications of tethers have been proposed and several missions have been flown; some missions were successful while others were unsuccessful. The major successful missions include: the Canadian Space Agency’s Observation of Electric-Field Distributions on the Ionospheric Plasma – a Unique Strategy (OEDIPUS) missions: OEDIPUS–A in 1989 and OEDIPUS-C  in 1995, NASA’s Small Expendable Deployer System (SEDS) missions: SEDS-1 in 1993 and SEDS-2 in 1994,  NASA’s Plasma Motor Generator (PMG) experiment in 1993, and the U.S. Naval Research Laboratory’s tether physics and survivability (TiPS) in 1996. The unsuccessful missions were NASA and ASI’s TSS-1 in 1992 and TSS-1R in 1996, and NASA’ Advanced tether experiment (ATEx) in 1998.  Some of the major causes of failure were found to be associated with tether deployment and tether breakage.  Researchers have tried to solve these problems using high performance tether deployer system and multi-strand tethers; however, the problems of tether deployment and breakage still exist. In this paper, we propose strategies to control the TSS in presence of these problems to achieve desired mission performance. 

The attitude stabilization of a satellite represents one of the important applications of tethers.  We consider this application and examine cases when tether deployment suddenly stops and tether breakage occurs. The TSS model considered in this study comprises of two identical tethers of equal length connecting the downward-deployed-auxiliary mass to two distinct points symmetrically offset from the satellite mass center. The Lagrangian formulation procedure is utilized to obtain the governing equations of motion of the TSS moving in an elliptic orbit. Due to the relatively short tether length considered in this study, it is assumed that the tether dynamics does not affect the orbital dynamics.  Next, a linear optimal controller as well as a nonlinear controller based on feedback linearization are developed for the tether offset variations, that ensure desired attitude control of the satellite.  Finally, for a detailed assessment of the proposed controllers, the set of governing TSS equations of motion is numerically integrated. The effects of various system parameters on system response are then examined.  The robustness of the controllers is tested against various initial conditions and disturbances. The proposed control strategies may be useful for future tether missions.

[1] Kumar, K.D., “A Review on Dynamics and Control of Non-Electrodynamic Tethered Satellite Systems,”  Journal of Spacecraft and Rockets, Vol.43, No.4, 2006,pp.705-720.

Abstract document

IAC-07-C1.2.04.pdf

Manuscript document

IAC-07-C1.2.04.pdf (🔒 authorized access only).

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