A quaternion sensor based controller for homing of underactuated AUVs

A new quaternion sensor based homing integrated guidance and control law is presented to drive an underactuated autonomous underwater vehicle (AUV) towards a fixed target, in 3D, using the information provided by an Ultra-Short Baseline (USBL) positioning system. The guidance and control law is firstly derived using quaternions to express the vehicle's attitude kinematics, which are directly obtained from the time differences of arrival (TDOA) measured by the USBL sensor. The dynamics are then included resorting to backstepping techniques. The proposed Lyapunov based control law yields global asymptotic stability (GAS) in the absence of external disturbances and is further extended, keeping the same properties, to the case where constant known ocean currents affect the vehicle's dynamics. Finally, a globally exponentially stable (GES) TDOA and range based nonlinear observer is introduced to estimate the ocean current and uniform asymptotic stability is obtained for the overall closed loop system. Simulations are presented illustrating the performance of the proposed solutions.