Dynamic Compensation Strategy for Beam Pointing Based on Cascaded Liquid Crystal Polarization Gratings Using Liquid Crystal Optical Phased Array

The cascaded liquid crystal polarization grating (CLCPG), a core non-mechanical beam scanning device, suffers from insufficient pointing accuracy due to inherent manu-facturing/assembly errors, which requires compensation by the liquid crystal optical phased array (LCOPA). Yet LCOPA is vulnerable to internal/external disturbance cou-pling and inherent time delay in practical conditions, hindering accurate compensation and limiting integrated system performance. This paper proposes a fractional-order com-posite control strategy: a fractional-order dynamic model of LCOPA is established first to characterize its response and viscoelastic memory effect; then a fractional-order mod-el-assisted extended state observer is designed for total disturbance estimation, combined with an improved Smith predictor for time-delay compensation and a phase margin method for fractional-order PID parameter tuning. Comparative experiments on a CLCPG-LCOPA experimental platform validate the strategy’s effectiveness: it suppresses disturbances, compensates CLCPG errors, reduces the overall pointing error by over 30%, improves dynamic response speed by 25%, and exhibits excellent robustness and stability, providing theoretical and technical support for high-precision CLCPG scanning system engineering.