Compensation method of Moiré fringe sinusoidal deviation in satellite optical communication coarse pointing system

In order to ensure that optical communication terminal points at target precisely, a method is put forward to compensate the sinusoidal deviation of Moiré fringe in photoelectrical encoder, which is the position sensor of the coarse pointing system. First, the structure and operational principle of the satellite optical communication terminal are introduced. Then the subdividing error of the encoder caused by sinusoidal deviation is analyzed, and the threshold of sinusoidal deviation that could satisfy engineering needs is given. Based on the principle of empirical mode decomposition (EMD), a compensating algorithm is put forward, in which the fundamental frequency of moiré fringe is decided according to the rotating speed calculated by the coarse coder. With empirical mode decomposition, the fundamental wave component is extracted. Simulation results indicate that this method works well at different rotating speeds. When the method is applied in a photoelectrical encoder in which the optical filtering lens is removed, the experiment result shows that the sinusoidal deviations are less than 0.85% at different speeds, the precision of the encoder maintains in 1″, and the encoder can satisfy the need of pointing precision.