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Tethered net systems are considered one of the most effective solutions for addressing the problem of space debris. However, it is crucial to study the robustness of net-based debris capture in the presence of a wide range of possible activation and environmental uncertainties. The aim of this study was to analyze the limitations and operational envelope of tethered net systems in capturing space debris, with a particular focus on robustness and safety. The success of capture in nonnominal conditions was investigated, with errors considered in the target position, angular velocity, and parameters concerning the ejection of the net. In the sensitivity study, a capture quality index and mission safety factor were used to evaluate the success or failure of capture in an automated way. The quantitative relationships between relative parameter errors and capture evaluation metrics are also presented. The results of the sensitivity studies are promising and suggest that the target capture is robust to inaccuracies in the mission parameters beyond what is expected in reality.
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Online Control and Moment of Inertia Estimation of Tethered Debris
Tethered capture of space debris is a promising method of Active Debris Removal, but has numerous well-known challenges in the post-capture phase. Control of the system in this phase is complicated by nonlinear dynamics with the potential of chaotic motion, unknown debris parameters, and debris tumbling. The inherent uncertainty present in the system and the need for control often necessitate the estimation of debris states and parameters such that the post-capture system can remain controlled. To this end, a relative distance Proportional-Integral-Derivative control and an Unscented Kalman Filter are implemented during the post-capture phase of an ADR mission. It is assumed that some debris (target) states and properties are unknown to the chaser, requiring the estimation of the attitude, angular rates, and principal moments of inertia of the target. For estimating these states, the UKF uses measurements of the tether tension magnitude and pixel coordinates of feature points on the target provided by a camera mounted on the chaser. Both estimation and control are done simultaneously, simulating online estimation and control of an ADR mission. The PID control was found to maintain safe conditions when using the estimated states in two separate Monte-Carlo simulations, differing in the measurement frequency of the pixel coordinates, while the estimation of the principal moments of inertia of the debris was satisfactory.
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- Award ID(s):
- 2105011
- PAR ID:
- 10539750
- Publisher / Repository:
- American Institute of Aeronautics and Astronautics
- Date Published:
- ISBN:
- 978-1-62410-711-5
- Format(s):
- Medium: X
- Location:
- Orlando, FL
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.2514/6.2024-1286
