Prototype design and mission analysis for a small satellite exploiting environmental disturbances for attitude stabilization

Abstract

In order to accomplish complex and sophisticated missions, small satellites, particularly CubeSat, need a robust and accurate attitude control system. Due to the mass- and volume-constrained design environment of CubeSat, conventional methods are sometimes inadequate to provide needed performance at low altitudes where environmental disturbances are high. This thesis studies exploitation of the most dominant disturbance torque at low altitudes (i.e., the residual aerodynamic torque) for stabilization and attitude control. By shifting internal masses, the distance between the center of pressure and the center of mass is adjusted so that the aerodynamic torque can be modulated as the control torque. To establish a realistic simulation environment, all launched CubeSat missions were analyzed in terms of their attitude control methodologies, sizes, altitudes and mission types. In light of the mission analysis, a prototype 3U CubeSat was designed with only commercial off-the-shelf components to check the practicality and feasibility of the method. The Linear Quadratic Regulator control method with gain scheduling was used to stabilize and control the attitude in a high-fidelity simulation environment. In simulations, the method stabilized the CubeSat and maintained the desired attitude under varying conditions such as initial angular velocity and displacement, orbit altitude and inclination, shifting mass fraction and CubeSat alignment and size.