Fast disturbance rejection for inertial stabilization platforms based on a nonlinear adaptive sliding-mode-assisted disturbance observer.

The inherent dynamic mechanism of existing disturbance observer (DOB)-based methods usually leads to non-negligible transient residual errors when abrupt and fast-varying disturbances occur. In particular, the insufficiently fast suppression of DOB residual effects remains a key issue in inertial stabilization platforms under abrupt disturbances. To address this issue, this paper proposes a nonlinear adaptive sliding-mode-assisted disturbance observer (NASMADO) for abrupt-disturbance rejection in inertial stabilization platforms. In the proposed framework, a tracking-differentiator-based disturbance observer is used to estimate the dominant lumped disturbance, while an adaptive sliding-mode-assisted term is introduced to compensate for the residual estimation error of the observer. A specially designed adaptive law enables the switching gain to increase rapidly in response to abrupt residual variations without requiring prior knowledge of the disturbance bound. Lyapunov-based stability analysis is conducted to verify the stability of the proposed method. Comparative experiments on an inertial stabilization platform demonstrate that the proposed NASMADO provides stronger abrupt-disturbance rejection and better transient performance than conventional DOB- and ASMDO-based anti-disturbance methods.