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

Min Zhang,Bo Li,Shoufeng Tong

doi:10.1109/jphot.2020.3031260

Abstract

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.

Highlights

The beaconless spatial acquisition algorithm and dynamic tracking have received increasing attention mainly due to the system miniaturization design and the platform vibration of communication terminal [1]–[3]
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
We concentrate on beaconless acquisition with a spiral scanning method combining two actuators for improving the coverage of a large uncertainty cone with a narrow communication beam, and the appropriate mathematical models and the corresponding analysis are presented to describe this scan pattern

Summary

Introduction

The beaconless spatial acquisition algorithm and dynamic tracking have received increasing attention mainly due to the system miniaturization design and the platform vibration of communication terminal [1]–[3]. For the optical transmission system, before the communication begins, a communication beam has to scan over the whole uncertainty region, the terminal corrects the optical axis according to the position offset of the detected spot [4]–[7]. Such as the typical beacon acquisition process for laser communication system, which involves scanning a high power and high divergence angle light over the uncertainty area until the target spot is detected on the sensor and locked on, and starting a tracking process for a low power and low divergence communication light [8], [9]. We concentrate on beaconless acquisition with a spiral scanning method combining two actuators for improving the coverage of a large uncertainty cone with a narrow communication beam, and the appropriate mathematical models and the corresponding analysis are presented to describe this scan pattern

Objectives

Methods

Conclusion