Hierarchical Robust Path Following Control of Fully Submerged Hydrofoil Vessels

This paper investigates the hierarchical path following control of a fully submerged hydrofoil vessel (FSHV) in the presence of additive disturbances. Roll dynamics is particularly considered for planar path following in both kinematics and rigid-body dynamics. A coordinated turn aided line-of-sight (LOS) guidance methodology is proposed for the guidance system design. In this approach, an adaptive LOS guidance algorithm is presented to calculate the command course angle. An adaptive estimator is designed to estimate the sideslip angle caused by the drift forces of ocean currents. The command bank angle is calculated based on the dynamics of the cross-track error and the coordinated turn constraint, which highly improves the maneuverability of the FSHV. A robust integral of the sign of the error feedback control is proposed as the autopilot to cope with attitude tracking of the lateral dynamics. The cascade characteristics of the guidance system and the autopilot are discussed; uniform asymptotic stability of the overall closed-loop system is achieved via cascade system theory. Simulation results validate the effectiveness of the hierarchical control strategy, and disturbance attenuation can be guaranteed for the composite guidance and control of the FSHV.