Control and filtering methods for causes and reduction of jitter formation on optical beam: Various applications in optical space communication

In this thesis, the control of a fast steering mirror, which is the core element of an adaptive optics system, is investigated to suppress the beam jitter.The main source of the jitter is taken as the atmospheric turbulence. The effect of the atmospheric turbulence on the beam jitter is experimentally determined with respect to the two different refractive index structure parameters. The mathematical model of the fast steering mirror based on the atmoshperic turbulence data is obtained using the system identification. In order to overcome implementation problems, the low order proportional integral-derivative (PID) type controllers, which minimize the H_∞ norm of the closed loop system, are designed in the centralized and the decentralized settings. In addition to this, the fixed order weighted H_∞ controller is based on the frequency characteristics of the atmospheric turbulence that is determined experimentally. Then, in order to show the effectiveness of the proposed low order PID type controller, the designed controllers are compared on the experimental setup. Finally, the simulation and the experimental results are presented. Comparison of advantageous and disadvantageous of centralized and decentralized controller architectures are discussed. In addition, the hysteresis nonlinearity arising from the piezo structure in FSM mirrors is discussed. It has been seen in the applications on the system that the controller performance can be increased if the nonlinearity that affects the closed loop controller performance is corrected.