Hemispherical Space Constrained Velocity Free Control of UUVs via a Coupled Funnel Scheme

This article studies the hemispherical space constrained velocity free tracking control problem of unmanned underwater vehicles with unknown hydrodynamics and external underwater perturbations. Distinct from prior research on uncoupled output constraints in each single dimension, this work considers the practical coupled hemispherical constraints related to multiple dimensions. First, to solve the problem of unmeasurable velocities, a dynamic gain compensator is developed, which obviates the need for precise knowledge of the system dynamics, especially the inertia matrix. Second, an output feedback control approach is introduced by utilizing an innovative hemispherical coupled funnel and a state transformation, which is characterized by its straightforward design and independence from estimating unknown nonlinearities. Finally, the practicality and feasibility of the control scheme are verified by an experiment employing an open-frame underwater vehicle.