Optimal Control Technologies For Astronomical Telescope Under The Atmospheric Turbulence

Adaptive Optics (AO) is becoming an indispensable technology to the unaidedoptical telescope. Due to the time delay of system control, the performance isdegraded seversely. Propoational-Integral (PI) control is usually adopted in AO as acontroller, but it is not an optimal controller in the sense of the minimum variance.Especially in the application of telescopes with large apertures, the advancedcontrollers with high precision are required urgentely. Meanwhile, the correspondingparameters of atmospheric turbulence have to be acknowledged more specifically anddetected with higher-precision methods. In addition, the performance of AO isconstrained by non-common path error. Moreover, in the interference telescope, thepiston which has been discarded in classical AO of telescopes with single aperturewill lead to the terriable effect to telescope and has to be taken in account. Thisdissertation focuses on these thesises and many endeavours are done which are listedbelow.At first, the AO systems of the first imaging camera of Extremely LargeTelescope (ELT) are introduced and the vibration of telescope which will degrade theperformance is also introduced. According to these backgrounds, the experimentalsimulation model is introduced. This setup is also the basis of the dissertation.Secondly, there are two main methods dectecting parameters of atmosphericturbulence which are described: Differential Image Motion Measurement (DIMM)and Scintillition Detection and Ranging (SCIDAR) are introduced. Based on the firstmethod, a new method with Shack-Hartmann (S-H) sensor detecting the parameters ofturbulence pahse screen is proposed. Then a phase screen with unknown parameters istested with proposed method and the feasiable resutlts are abtained.Thirdly, the psiton aberration of turbulence in the interferic telescope is studiedspecifically. A series simulation models based on different turbulence strength is builtto retrieve the piston error. The simulation results show that the piston errors can notbe negleceted in the interferic telescopes. Meanwhile, the wind speed of turbulence isalso able to be retrieved.Fourthly, a series decoupling patterns to accelerate the stochastic parallelgradient descent (SPGD) technology are proposed and analyzed therotically where anew decoupled method based on H-S sensor is proposed. The probable aspects when it is applied to the practice are analyzed specifically. In addition, the static anddynamical tuebulence models are numerically simulated to apply to test our methods.Then, a series laboratory tests are completed. Although the testing results show themore complexity of proposed methods, the higher convergence speed which istwo-three times than the normal SPGD conrol is achieved. Therefore, the higherbandwithds can be abtained.Fifthly，a new method based on SPGD control with S-H sensor to calibrate thenon-common path aberration of AO system is proposed. This method can lead to avery high precision of AO system without changing the infrastructure of initial setup.Then a labortary AO setup is calibrated precisionly with this method.Sixthly, a modern control method Linear Qradrtic Gauss (LQG) control isanalyzed specially in AO system. A corresponding simulation model is also built toanalyze this method. In addition, the divergence of this method in AO is analyzed andthe related restraints to solve this problem are also proposed. The correspondinglyexperimental tests have been done to test the modified LQG (MLQG) control. Theresults state that the MLQG can suppress the divergence effectively. Furthermore, thismethod is also compared to PI control. The root mean square (RMS) of residualwavefront after control with MLQG is10%lower than that with PI control. Thebandwidth is also increased.This dissertation will offer a great help of AO researchers and will promote themore and more advandced techniques applied in AO. It will also develop the AOtechnique to a certain extent.