A sub-region priority reaching control scheme with a fuzzy-logic algorithm for an underwater vehicle subject to uncertain restoring forces

This paper presents an adaptive sub-region priority reaching controller with a fuzzy logic algorithm for an underwater vehicle. In this method, the sub-region priority reaching control law is merged with a fuzzy technique to manage the generalization of the underwater vehicle set-point control problem. The fuzzy technique is used to handle multiple sub-region criteria. These criteria are: depth constraint, avoiding the region with an obstacle inside it, ensuring visibility of the feature during visual servoing and region shape constraint. Due to the unknown gravitational and buoyancy forces, an adaptive term is adopted in the proposed controller. Moreover, the unit quaternion representation is used in order to achieve a singularity-free attitude representation. The stability analysis is carried out using the Lyapunov type approach. Simulation results are presented to demonstrate the effectiveness of the proposed control technique.