Applications Of System Modeling For Vlt Instruments - Art. No. 62701a

This work presents the use of system modeling with the aim of maintaining and improving instrument performances. The complexity and cryogenic nature of infrared systems prevent continuous hardware upgrades, so that the advantages of modeling are of high value. Two applications of modeling and basic control theory are shown. The first example concerns the performance monitoring of the ISAAC cryogenic system. The measured and simulated cold structure temperatures are compared in real time, allowing for anticipation of possible failures of the cooling system and therefore for reduction of operational downtime. The second case is about the position control of the duo-echelle grating of the VISIR spectrometer. The controlled system was identified and simulated to select controller parameters that improve the image stability. Preliminary results show the possibility to get better compensation of the disturbances induced by the telescope movements, leading to an enhancement of the data quality.