Automatic Control Systems for Adaptive Optical Systems: Analytical Review. Part 1: Adaptive Optical System Control of Onboard Laser Installations

Abstract

The first part of the analytical review presents an introduction to automatic control systems (ACS) for the adaptive optical systems (AOS) and control of tip-tilt correctors to eliminate a laser beam jitter. Considers a composition and a purpose of the AOS basic components. Also gives the AOS schemes to be used to form the sharper object images and focus radiation on a target when propagating a laser beam in a turbulent atmosphere. Briefly discusses the general issues of the AOS control, namely single-channel and multichannel linear control, bandwidth limitations of the control system, and possible signal paths in ACS of AOS.The article in-detail describes a path of the harmonic signal through the units of the feedback control loop as applied to the plane mirror of a two-channel corrector of the wave front tip-tilt. Provides guidelines to select the minimum quantization time for a propagating digital signal.Considers the certain problems of constructing ACS to be applied to AOS of the on-board laser installations. A simulated installation model where light passes through a turbulent atmosphere allowed us to develop a linear quadratic Gaussian controller (LQG-controller). Using this controller the optimal control (i.e. minimizing the dispersion of the output signal measured) with good robustness of the tip-tilt corrector is carried out.The concluding part of the review presents the certain research results of the AOS control when compensating the laser radiation wave front perturbations caused both by an aero-optical problem, arising when radiation propagates near the walls of an aircraft and by an atmospheric turbulence of free airflow. The influence of a small time delay (within one sampling step), when transmitting a control signal, on the control system operability was under special consideration.