DRAG-FREE CONTROL CONCEPTS FOR THE STEP MISSION

摘要

The Satellite Test of the Equivalence Principle (STEP) is a space-based fundamental physics experiment designed to test the Equivalence Principle with greatly increased precision. The accuracy of the measurements needed to reach this goal demands a very low disturbance environment for the satellite. The only way to reach the disturbance rejection quality needed for the experiment is to apply a so called Drag-Free and Attitude Control System (DFACS). This paper focuses on the investigation of applicable control concepts and the development of controller algorithms for such a DFACS for STEP, keeping in mind the applicability of the general concepts to similar missions. As a first step a simple one-dimensional case is considered in order to test different control concepts for their applicability to the problem. This paper will focus mainly on modern controller design methods. The classical design is considered for completeness only. The performance of each controller is tested with respect to the STEP requirements and the different control concepts considered are compared. The baseline concept for STEP is selected and then used to design a controller for the more complex six degree-of-freedom control when one differential accelerometer is considered. The performance of this controller is tested with respect to the STEP requirements.