Two feedback slew algorithms are proposed for prolate spinners with single-thruster.
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Proposed algorithms are based on open-loop Half-Cone and Sector-Arc Slew.
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Feedback contributes to H estimation, attitude prediction and a new cancellation mechanism.
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Robustness analysis proves their improvement over spin-rate perturbations.
Abstract
A number of low-cost open-loop slew control algorithms have been developed for prolate spinning spacecraft using single-thruster actuation. Robustness analysis indicates that these algorithms have high sensitiveness over thruster firing time error, spacecraft inertia error, and especially spin rate perturbations. This paper proposed two novel feedback slew algorithms, Feedback Half-Cone and Feedback Sector-Arc Slew, built on the existing open-loop algorithms and they use attitude and angular velocity feedback to compensate the errors in knowledge of spin rate, without external torques. As presented, after the first thruster actuation initiate the spin-axis precession, the feedback slew algorithms take attitude and spin-rate feedback to estimate the angular momentum and predict the spin-axis attitude during the slew. These techniques contribute to improve the cancelation thrust impulse accuracy and reduce the final nutation error. Simulations for a Penetrator mission scenario validate these feedback algorithms and show their slew performance and robustness over the perturbations mentioned above. It is proved that the attitude feedback greatly improves the slew accuracy and robustness.
