High-dynamic tracking control technology for the fast-steering mirror in a laser communication system

A laser communication system requires high-dynamic and high-precision tracking capabilities to avoid beam deviation from the target. Therefore, this paper designs the active disturbance rejection control strategy based on a reduced-order extended state observer to ensure a large bandwidth of the fast-steering mirror (FSM) while reducing the difficulty of parameter tuning and improving system accuracy. Additionally, the differential adjustment factor is introduced to balance the delay caused by the tracking differentiator, simultaneously addressing overshoot suppression and rapid response. Experimental results show that in a 1 mrad step response, reduced-order linear active disturbance rejection control (RLADRC) reduces the rise time by 8.49% and 17.99% compared to proportional-integral-derivative control (PID) and linear active disturbance rejection control (LADRC), respectively. Under a 300 Hz sinusoidal input, RLADRC exhibits an amplitude attenuation of 28.5%, which is 24% and 21% lower than PID (37.7%) and LADRC (36.3%), respectively. In terms of comprehensive phase lag, RLADRC demonstrates superior tracking performance. In a 30 Hz frame-rate imaging system, the fast-steering mirror employing the proposed algorithm shows excellent tracking performance under external disturbances, meeting the requirements of practical engineering applications.