Generalized Dynamic Inversion based Attitude Control of Autonomous Underwater Vehicles

:A novel Generalized Dynamic Inversion (GDI) based two-loops structured control system is proposed for position and attitude control of Autonomous Underwater Vehicles (AUVs). The outer (position) loop utilizes Proportional-Derivative (PD) control of the sway and heave position error variables and provides the reference roll and pitch attitude angles to the inner loop. The inner (attitude) loop utilizes GDI control of a prescribed asymptotically stable dynamics of the attitude angles errors from their desired values, and provides the required control surface deflections such that the desired path of the vehicle is tracked. The GDI singularity avoidance is achieved by augmenting a dynamic scaling factor in the Moore-Penrose generalized inverse. The involved null control vector is constructed to be linear in the roll and pitch angular velocities, and the proportionality gain matrix is designed via a control Lyapunov function such that global closed loop stability of the internal dynamics is guaranteed. A detailed six degrees of freedom mathematical model of the Monterey Bay Aquarium Research Institute (MBARI) AUV is used to evaluate performance of the proposed control design, and numerical simulations are conducted to demonstrate its effectiveness and robustness under nominal conditions and in the presence of disturbances and parametric variations.