Lyapunov-based decentralized adaptive control for laser beam tracking systems

A successful controller design is crucial for establishing and maintaining an optical link between free-space communication stations engaged in a laser communication session. This task is quite difficult due to nonlinear behavior, cross-coupled dynamics, and time-varying characteristics of all known beam steering technologies. A novel adaptive control technique utilizing Lyapunov function to ensure global asymptotic stability of the system, thus resulting in a highly robust system performance, is developed. The technique applied to a piezo-electric mirror setup results in a highly efficient controller design that does not require prior knowledge of system dynamics, while providing independent access to azimuth and elevation positions of the laser beam. The basic algorithm is presented and the results of its application are demonstrated.