System Identification of Space Manipulator Systems and Its Implications on Robust Control Performance

Space manipulator system (SMS) maneuvers can excite flexible appendages, while fuel sloshing effects impact its dynamics and performance. To predict this behavior and control such systems, sloshing and flexible appendages are modeled. A novel system identification scheme is developed, which identifies all parameters required for the reconstruction of system dynamics despite unmeasurable sloshing and modal states. This is achieved by two identification experiments. In Exp.1 all unmeasurable states are eliminated, while in Exp.2 the unmeasurable sloshing states are eliminated, and a novel estimator is used for the unmeasurable modal states. The significance of accurate SYSID in controller design and performance is demonstrated by simulating a 3D SMS controlled by model-based and robust controllers. In both cases, using the identified parameters results in significant robust control performance enhancement.