Control of a gravity gradient stabilised satellite using fuzzy logic

This paper describes attitude control of a small gravity gradient stabilised satellite. A gravity gradient stabilised satellite has limited stability and pointing capabilities, and magnetic coils are added in order to improve the accuracy of the attitude control. The magnetic coils are controlled using a fuzzy logic controller, based on a combination of membership functions and rules. The control of the pitch axis is separated from the roll and azimuth axes and excellent pitch angle accuracy is achieved. The roll and azimuth axes are controlled using a common magnetic coil, that has a non-linear and time-varying torque characteristic and, therefore, accurate roll and azimuth angular control become much more difficult to achieve. However, combining one roll controller and two azimuth controllers result in an acceptable roll and azimuth angular accuracy after a few orbital periods