Pure Disturbance Sliding-Mode Feedback Control Based on Disturbance Observation for CCD-Assisted Line-of-Sight Stabilization

Excellent disturbance rejection ability is essential for a photoelectric tracking system (PTS) based on the Charge-Couple Device (CCD) sensor, which is a premise guarantee for obtaining highly accurate tracking, especially under the condition of moving carriers with intense disturbances. The feedforward control method based on disturbance estimated from the system model output and sensor output is currently a commonly used strategy for disturbance compensation due to its ability to directly counteract the disturbances. This disturbance feedforward compensation method behaves sensitively in case of model mismatch caused by internal disturbances, which may lead to a significant reduction in the disturbance compensation effect or even cause system instability. In this paper, unlike disturbance feedforward compensation, a pure disturbance sliding-mode feedback control (DSMFBC) based on disturbance observation without additional sensors is proposed, ensuring faster and precise compensation for disturbance. In case of model mismatch, the observed disturbance is used to build the disturbance feedback control to maintain a more efficient disturbance compensation through the robustness that feedback naturally possesses. To achieve a stronger anti-disturbance capability, a sliding-mode nonlinear control method is used to design the control law. The experimental setup of PTS based on the fast-steering mirror (FSM) demonstrates that the method has better dynamic performance and disturbance rejection ratio.