Output Feedback Tracking of Ships

TLDR

Ship dynamics are highly nonlinear, and for tracking control these nonlinearities must be incorporated into the control design. The paper investigates output‑feedback tracking of ships using only position and orientation measurements, proposing an observer‑controller scheme that incorporates full ship dynamics and achieves semi‑globally uniformly stable closed‑loop behavior. The authors design an observer‑controller that includes Coriolis, centripetal forces, and nonlinear damping, develop a gain‑tuning procedure, and implement it on a 1:70 Froude‑scaled model supply ship. Experimental data, compared with ideal simulations, confirm the semi‑global exponential stability predicted by theory.

Abstract

In this brief, we consider output feedback tracking of ships with position and orientation measurements only. Ship dynamics are highly nonlinear, and for tracking control, as opposed to dynamic positioning, these nonlinearities have to be taken into account in the control design. We propose an observer-controller scheme which takes into account the complete ship dynamics, including Coriolis and centripetal forces and nonlinear damping, and results in a semi-globally uniformly stable closed-loop system. Furthermore, a gain tuning procedure for the observer-controller scheme is developed. Experimental results are presented where the observer-controller scheme is implemented onboard a Froude scaled 1:70 model supply ship. The experimentally obtained results are compared with simulation results under ideal conditions and both support the theoretical results on semi-global exponential stability of the closed-loop system.