Slew Control of Prolate Spinners Using Single Magnetorquer

摘要

This note has introduced a novel low-cost slew algorithm for prolate spinners' attitude maneuver using single magnetorquer. The algorithm builds on the half-cone control method's philosophy, and it uses a single magnetorquer mounted along the spin axis to initiate and cancel the spin axis precession using two periods of actuations. During the first actuation, the total angular momentum change is measured by magnetic torque integration. It also uses the spacecraft attitude feedback to calculate the timing of the second actuation and introduces a timing adjustment coefficient to ensure the accuracy of precession cancellation. Simulations based on STRaND-1, a 3U cubesat launched by Surrey Space Centre and Surrey Satellite Technology Limited, was chosen as a use case to simulate 90 deg attitude maneuvers parallel with Earth equatorial plane. These maneuvers were carried out at different orbital positions. Based on the test results, the proposed slew algorithm provides slew performance with angular momentum error and residual nutation angles both less than 5 deg in equatorial and geomagnetic polar regions, though with different magnetorquer current directions. Further analysis on the slew performance indicates that the single-magnetorquer slew algorithm requires the major component of the geomagnetic field to be perpendicular to the direction of the attitude maneuver. In conclusion, the single magnetorquer slew algorithm opens up the possibility for nanosatellites to perform a large-angle spin axis maneuver using a single magnetorquer based on the half-cone method concept. Future work can include further robustness analysis of the slew algorithms and investigation of tuning method for ξ (second actuation time adjustment coefficient). Furthermore, for medium-latitude locations in orbit, a combined control scheme of single-magnetorquer slew algorithm with alterable magnetic torque directions can be investigated.