Active Disturbance Rejection Control for the Ranger Neutral Buoyancy Vehicle: A Delta Operator Approach

In this paper, an active disturbance rejection control (ADRC) method is investigated for the ranger neutral buoyancy vehicle (RNBV) via a delta operator approach. In order to eliminate unmodeled nonlinearities and exogenous disturbances for a neutral environment, a novel delta-domain ADRC method is put forward to achieve the tracking control performance of the RNBV. In the proposed ADRC method, an extended-state-observer (ESO) is designed in the delta domain to estimate the so-called total disturbance that reflects the aggregated impacts of the nonlinearities and disturbances. Then, by using the estimates provided by the ESO, a composite controller is developed such that the closed-loop system can be input-to-state stable. It is shown in practical experiments that the proposed delta-domain ADRC outperforms its discrete-domain counterpart in consideration of the finite-word-length effects.