Fuzzy Logic Sliding Mode Control for Large Optical Telescopes

The global tendency to increase the diameter of the main mirror of the telescope leads to a corresponding increase in the size and mass of the elements of the telescope mount assembly, which are controlled by gearless drives of the corresponding axes. Such drives are characterized by high tracking and positioning accuracy with errors not exceeding angular seconds at ultra-low rotation speeds. Additionally, such control objects are characterized by the nonlinear function of the friction torque and external disturbances, which primarily include a significant wind torque. Also, in the control algorithms, it is necessary to take into account the elastic and damping properties of the links between elements of the controlled axes. These factors require the use of so-called robust controllers that can compensate for these undesirable factors. This article proposes a controller synthesized on the basis of a sliding mode with an observer for parallel estimation of system states. To estimate the speed of the system, a classical optimal observer is used, which provides high accuracy in estimating the speed of the system and ensures the convergence of the estimation error into a small zone.