Robust tracking control for dynamic positioning ships subject to dynamic safety constraints

Abstract

This paper addresses the dynamic safety constraint problem for the Dynamic Positioning (DP) ship subject to model uncertainties and unknown environmental disturbances. To guarantee the dynamic safety constraints, a new constraint technique based on the unified barrier function (UBF) is used to convert the original constrained DP system into an equivalent “non-constrained” one. By blending the new coordinate transformation into backstepping design, the position and velocity of the DP ship keep within the given constraints. In addition, a bioinspired neurodynamics model (BNDM) is developed to solve the traditional differential explosion problem of the virtual control law and limit the output in a certain range. Further, a sliding mode disturbance observer (SMDO) is introduced to estimate the model uncertainties and unknown environmental disturbances with minor chattering and rapid convergence. Finally, the effectiveness of the proposed controller and observer of the DP ship is illustrated by numerical simulations.