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Abstract

The gyroless attitude control method and kalman algorithm procedures presented in this paper are applicable to asymmetrical microsatellites of any shape with large mass variation and without angular rate sensors. The attitude sensors include a three-axis magnetometer, a horizon sensor, and a coarse sun sensor (CSS), which together serve as an analytic platform and help in ensuring the stability of attitude controls. The attitude control problem of microsatellites has become a focal point because microsatellite fabrication processes are short, costless, and can be flexibly used for various purposes. The center of mass of the microsatellite can be offset because of fuel consumption during propulsion, irrespective of the existence of interference from the external orbital environment, such as gravity gradient torque and solar radiation torque. For a microsatellite with a discoid and asymmetrical shape, attitude control is difficult. One of the solutions to overcome the difficulty is to design a robust controller that assists the attitude pointing of the satellite to satisfy requirements in the presence of internal parameter perturbations and external disturbances. The robust nonlinear state feedback used in the design of the propulsion mode attitude control for FORMOSAT-3 was applied in this study, and the feasibility of the controller was cross-validated through time and frequency domain stability analyses. The time-domain performance indexes (e.g., rise time, maximum overshoot, and stabilization time) of the designed state feedback gain were consistent with a robust stability margin of the stable performance index in the frequency domain. Furthermore, to reduce the weight and manufacturing cost of the satellite, an extended Kalman filter algorithm was used to obtain the gyroless satellite attitude rate. Other sensors, such as the CSS and earth horizon sensor were adopted to help sense satellite attitude controls

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