Fuzzy Disturbance Observer-Based Modified Variable Gains Super-Twisting Sliding Mode Composite Control for a Two-Axis Airborne Optoelectronic Stabilized Platform

Abstract In order to enhance the tracking performance of a two-axis airborne optoelectronic stabilized platform with external disturbances, a novel composite control strategy is proposed based on a modified variable gains super-twisting sliding mode control and an adaptive fuzzy-based disturbance observer (MVGSTSMC-FDO), which highlights advantages of both two strategies. The adaptive FDO is designed to observe and compensate time-varying lump external disturbances of the closed stabilizing loop, which strengthens the robustness of the system. Under the counteraction of the external disturbances, the modified super-twisting sliding mode control law is designed with variable gains to achieve the excellent control performance including strong robustness, weak chattering, low steady-state errors, fast convergence, and high adaptability. Moreover, the uniform stability of the adaptive control system is rigorously proved by the Lyapunov theory analysis method. Simulations on the stabilization loop system of a two-axis stabilized platform with cross-coupling disturbances and are carried out to show the effectiveness of the proposed control strategy. Compared with other different control methods, the results illustrate that the proposed control strategy not only obtains high tracking precision with fast convergence, but also provides a stronger robustness against external disturbances.