| Summary: | The tethered TSAR (tomographic synthetic aperture radar) system is a group of tethered SAR satellites that can be rapidly deployed and provide a stable baseline for 3-dimensional topographic mapping and moving target detection. Successful deployment is critical for TSAR tethered system. This paper discusses the deployment strategy for a 3-body chain-type tethered satellite system in a low-eccentric elliptical orbit. Two deployment strategies are discussed. Then, the tension on the tether is used to deploy it to the desired length and suppress its sway motion, resulting in an underactuated and input-constrained system. Hierarchical sliding mode control (HSMC) with anti-windup technology is employed to overcome the above challenges. In addition, the proposed approach includes the use of a disturbance observer to estimate the second derivative signal and a robust differentiator to estimate the sliding surfaces of the unacted subsystem. Finally, the effectiveness of the proposed deployment strategy is verified by MATLAB/Simulink.
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