A New Composite Spiral Scanning Approach for Beaconless Spatial Acquisition and Experimental Investigation of Robust Tracking Control for Laser Communication System with Disturbance

The establishment of laser communication relies on high probability acquisition and then stably track with a high precision. However, the limitation of laser divergence and the interference may lead to unstable acquisition and tracking. In this paper, we proposed a novel beaconless acquisition approach to achieve the coverage of a large uncertainty cone with a narrow communication beam, using a composite spiral scanning method based on fast steering mirror and servomechanism system. The modeling and an analytical expression of sub-regions searching in conjunction with spiral skip overlap are described to realize the effective coverage. A detailed analysis of optimal matching for acquisition parameter is presented to quantify the design result. For the tracking procedure, an experiment is presented to investigate the performance of servo system with the combination of coarse-fine tracking consideration, and iteration learning control scheme in additional to the traditional controller based on periodic external disturbance is introduced for dynamic target tracking system. The iterative control law is taken into account to adjust deviation value and further improve the tracking performance. The obtained tracking accuracy is within ±2µrad which demonstrates the effectiveness the control characteristic in the presence of laser fluctuation.