Experimental study on Modified Linear Quadratic Gaussian Control for   Adaptive Optics
  To achieve high resolution imaging the standard control algorithm used for classical adaptive optics (AO) is the simple but efficient proportional-integral (PI) controller. The goal is to minimize the root mean square (RMS) error of the residual wave front. However, with the PI controller one does not reach this minimum. A possibility to achieve is to use Linear Quadratic Gaussian Control (LQG). In practice, however this control algorithm still encounters one unexpected problem, leading to the divergence of control in AO. In this paper we propose a Modified LQG (MLQG) to solve this issue. The controller is analyzed explicitly. Test in the lab shows strong stability and high precision compared to the classical control. 
Qiang Fu, J\"org-Uwe Pott, Peter Dethard, Feng Shen, Changhui Rao,   Xinyang Li
astro-ph.IM