NASA EPSCoR: Attitude Control of Satellites using Noncommutative Rotations

The objective of this proposal is to develop an orientation controller for satellites that use reaction beams. A reaction beam is a new type of orientation actuator, which is being considered by NASA to replace conventional orientation actuators for small satellites (e.g., CubeSats). A reaction beam is a bimorph actuator that is mounted within the satellite and controlled to produce small amplitude vibrations. The vibrations produce internal moments, which can be used to control the satellite's orientation. Specifically, when two reaction beams are mounted on orthogonal body-fixed axes and vibrate with different amplitude, phase, or frequency, the satellite will rotate about the third orthogonal body-fixed axis. This effect is due to the noncommutative property of body-fixed rotation sequences. This research will develop control techniques that can be used to asymptotically track orientation commands. Experiments will be performed to demonstrate the effectiveness of these control techniques. For these experiments, reaction beams will mounted to two body-fixed axes, and the orientation of the third axis will be controlled.