Integrated controller-observer system for marine surface vessels

Abstract

A robust nonlinear controller has been designed to control the surge speed and the heading angle of a marine surface vessel. The control actions are carried out through the propeller and the rudder. Moreover, a nonlinear observer has been devised to accurately estimate the surge speed and the yaw angle and their time derivatives. Both the controller and the observer are designed based on a reduced-order model of the ship. However, their performances have been assessed on a six degree-of-freedom ship model, which accounts for the wave excitation, retardation forces, nonlinear restoring forces, wind and sea-current resistive loads. Furthermore, the model accounts for the physical limitations of both the rudder and the ship propulsion system. The simulation results demonstrate the capability of the integrated controller-observer system in providing a good tracking characteristic of the ship in spite of significant modeling imprecision and environmental disturbances.

Guidance and control scheme for under-actuated marine surface vessels

“…The dynamic model for the marine surface vessel has been presented in [10], [13]. Its formulation, which closely follows the literature on ship modeling [1], [14]- [18], is briefly described herein.…”

“…Moreover, the dynamics of the rudder are formulated by accounting for both the velocity of the fluid approaching the rudder after being influenced by the propeller [18], [27] and by the velocity of the fluid induced by the sway motion of the ship [10]. The velocity components provide the overall direction with which the fluid approaches the rudder, which is crucial for determining the coefficients needed in the computation of the lift, L f , and drag, D f , forces of the rudder [28], [29].…”

“…The modified version of the two-layer robust controller [10] is discussed in Section 4. It should be stressed that the controller is designed based on a reduced-order model, which only accounts for the surge and yaw motions of the ship.…”

“…The nonlinear model for a marine surface vessel presented in [10], [13] has been used here as a test bed to assess the performance of the proposed guidance and control system. The model is briefly summarized in the next Section.…”

“…Therefore, self-organizing neural-net controllers [6], fuzzy controllers with real-time tuning algorithms [7]- [8], and sliding mode controllers [9]- [10] have been used in maritime applications. In this work, the sliding mode methodology has been adopted for the design of the controller due to its robustness to both structured and unstructured uncertainties of the system [11]- [12].…”