Nonlinear acceleration disturbance observer to reject transient peak disturbances for an inertial stabilization-tracking platform

A high-bandwidth nonlinear acceleration disturbance observer (NOADOB) is proposed to reject transient peak disturbances mainly arising from velocity commutation of an inertial stabilization-tracking platform (ISTP). The approach is essentially based on extracting acceleration peak signals and applying a saturation function. The observer structure employs acceleration measurements and combines velocity loop input and control quantity to acquire peak signals. Differing from the general disturbance observer, the extraction of acceleration peaks is used to quickly capture the change in error and effectively reduce the impact of signal noise for the observer implementation. To trade off the observer bandwidth and the system stability, a partial compensatory scheme of limiting the filter output with a nonlinear saturation function is adopted. The relationship between the saturation threshold and the filter bandwidth is analyzed for optimal balance. It is theoretically and experimentally proved the effectiveness of NOADOB in attenuating error peaks. Moreover, the proposal accelerates the dynamic response to peak disturbances, breaks through the constraint of accurate modeling, and improves disturbance rejection performance.