Magnetic-based Attitude Control Scheme for CubeSat

Nowadays, the development of low-cost CubeSats is very active. As the cheapest satellites are commonly used to demonstrate some novel technologies and dedicated to science researches, the requirements of Attitude Determination and Control System (ADCS) have been not very severe. Magnetic-based attitude control scheme is widely adopted by CubeSats for damping and stabilizing with several magnetic torquers employed. STU-2A, developed by Shanghai Engineering Center for Microsatellites, adopts such scheme with 3 reaction wheels equipped. However, the magnetic-based attitude control scheme, employing three magnetic torquers with or without a biased momentum wheel, is the basic attitude control strategy. Once being ejected into the orbit, the satellite would employ magnetic torquers to damp itself, and then, be controlled to Sun-pointing or Nadir-pointing. After the wheel is started up, rotation of the wheel would provide gyroscopic stiffness, while the attitude would still be controlled by the magnetic torquers. During the design of the corresponding attitude control laws, Quasi-Euler Angles, which are derived from quaternions and have similar characteristics with the classic Euler angles, are adopted to describe the attitude. Simulation results indicate that the designed attitude control schemes are effective and the pointing accuracy corresponding to nadir-pointing mode and biased-momentum mode are 15deg and 3deg respectively.