Homography-based Visual Servoing for Autonomous Underwater Vehicles

Abstract: A nonlinear visual servoing approach is proposed for the stabilisation of fully-actuated autonomous underwater vehicles (AUVs) by exploiting the homography matrix between the two images of a planar scene. In a cascade manner, an outer-loop control defines a reference setpoint based on the homography matrix, and an inner-loop control ensures the stabilisation of the setpoint by assigning thrust and torque controls. In contrast with conventional kinematic solution, the proposed controller deals with the high nonlinearity and coupling of the system dynamics and ensures almost-global asymptotical stability. In addition, the interactions of the AUV with the surrounding fluid (e.g., added mass and drag effects) are often difficult to model precisely whereas they may significantly perturb its motion. The proposed controller –augmented with an effective integral action – allows for the compensation of model uncertainties and for robust performance against such perturbations. Simulation results illustrating these properties on a realistic AUV model subject to sea current are reported. 1