AbstractsAstronomy & Space Science

This research investigates the application of advanced control algorithms to rotatable mirrors inside scientific astronomical telescopes. This does not apply to the typically large and heavy main mirror of the telescope but concerns a much smaller mirror in the optical path to the detector. Rotation of this mirror makes it possible to quickly alter the observation direction of the telescope without the need to rotate the complete instrument. During astronomical observations, very high positional stability and repeatability under the influence of different noise sources and disturbances, is absolutely necessary. This requires a lot of the control of these mechanisms. For example, for the Mid-Infrared E-ELT Imager and Spectrograph (METIS) Cold Chopper mechanism (MCC), which is the considered application, a positional stability requirement of 36 nanometer is specified. During this research a new hybrid control strategy has been developed. The application of this method to the chopper mechanism for the Heterodyne Instrument for the Far Infrared (HIFI), resulted in a significant performance improvement and shows the potential of this strategy. The hybrid control strategy forms an addition to the field of high performance motion control. The applicability of the hybrid controller to the MCC is however limited because of the unexpected presence of hysteresis in the mechanism. The use of a repetitive (self-learning) controller did result in the required performance and will be applied to the MCC mechanism. Advisors/Committee Members: Peletier, Reynier (assessment_committee), De Persis, Claudio (assessment_committee), Steinbuch, M. (assessment_committee).