Attitude Controller Design for Micro-satellites

The increasing interest of private companies in the aerospace sector has produced a growth of space missions oriented to exploration and colonization. Among the various markets, miniature satellites turns out to be the fastest-growing one. This paper aims to evaluate the control torques needed to ensure the attitude control of a micro-satellite. The orbital mechanics and the motion equations are presented in the first part of the paper. Furthermore, the primary disturbance torques, which act on the satellite varying its attitude and the interaction between the satellite and Earth, will be considered. Thanks to a 3D Solidworks micro-satellite model, several simulations have been conducted in the multibody simulator Simscape. The attitude controller considered for this activity is composed of four reaction wheels. By using a Lagrange multipliers optimization method, a controller based on a PID control system is designed. Such a procedure allows evaluating minimized control torques in order to guarantee several satellite attitudes. The results obtained prove that reaction wheels represent an excellent compromise between reliability and performance at low expense for micro-satellites.