Line-of-sight stabilization enhancement via band combination feedforward control in a mobile platform-mounted optical...

Maintaining stable line-of-sight (LOS) for free-space optical (FSO) communication terminals on mobile platforms is a critical challenge due to platform-induced jitter. Conventional inertial sensor-based feedforward control (FFC) employs a high-pass filter (HPF) to decouple commanded tracking motion from disturbance measurements, but this sacrifices the system's ability to reject crucial low-frequency disturbances. This paper proposes a synergistic control architecture that combines a disturbance observer (DOB) for low-frequency disturbance estimation with a gyro-based FFC for mid- and high-frequency rejection. The two signals are seamlessly fused by a complementary filter pair. This band combination strategy relaxes the conflict between wideband disturbance rejection and agile target tracking, eliminating the destructive effects of motion coupling without performance-degrading. The parameter tuning is systematically formulated as an optimization problem for the complementary filter pair, constrained by the target's maneuvering dynamics. Furthermore, the closed-loop stability and robustness are analyzed based on the sensitivity function and the small-gain theorem. Using this approach, satisfactory control performance is achieved for a telescope mounted on a 6-degree-of-freedom swing platform. Comparative simulations and experiments are conducted to validate the effectiveness of the proposed approach.