Experimental parameters estimation of satellite attitude control simulator

Abstract

Placing a satellite or any other spacecraft in orbit is a risky and expensive process; years of research and a lot of money are transformed into equipments that will be beyond any possibility of maintenance in case something goes wrong. Therefore, space projects must be carried on as carefully as possible in order to guarantee that satellite equipments perform its mission properly. In that context, experimental validation of new equipment and/or control techniques through prototypes is the way to increase system confidence. The Space Mechanics and Control Division (DMC) of INPE is constructing a 1D simulator, with rotation around the vertical axis and a 3D simulator, with rotation in three axes, to implement and test satellite Attitude Control System (ACS). However, to perform experimental test it is necessary to estimate the platform inertia parameters in order to balance the platform accurately, so it behaves similar to space torque free conditions. This paper presents the equations of motion and control law design for a 3 D attitude control system simulator. This 3 D model is simplified to 1D simulator from which the inertia moment is estimated by a recursive least squares that uses experimental data. The platform data are obtained in a simple experiment where a reaction wheel is used to apply torques and a gyroscope is used to measure the platform angular velocity. The inertia moment estimated by this approach is very close to the platform inertia moment value obtained by other method.