Adaptive control in the presence of quantization and saturation: Application to laser beam steering by a liquid crystal device

This paper presents an investigation of adaptive control for a system with control quantization and magnitude and rate saturations. The application is laser beam steering by a liquid crystal device. The effects of using a linear time-invariant feedback loop along with the adaptive controller are discussed, as well as the effects of using nonlinear and linear plant models in the adaptive controller. In contrast to conventional fast steering mirrors, the liquid crystal device optically redirects the laser beam and has no moving parts or structural resonance, which often requires a stabilizing feedback controller prior to the adaptive controller. Simulation and experimental results demonstrate the effects on the adaptive control performance of choices of linear or nonlinear, and open or closed-loop plant models, and show which choices yield best performance.