Modelling and Control of an Underwater Laboratory Glider

Underwater gliders are Autonomous Underwater Vehicles(AUV) which use change in buoyancy and moving internal masses to generate lift and drag forces necessary for gliding through the water column. This paper discusses the mathematical modelling and MATLAB based control simulations of an underwater laboratory glider [3] developed at IIT Madras. The external geometry of the laboratory glider comprises of fixed wings having NACA 0012 profile and a fixed rudder on an ellipsoidal hull. The variable buoyancy arrangement includes a piston cylinder module along with two internal masses designed to operate longitudinally using linear actuators. Force and moment coefficients have been derived using Computational Fluid Dynamics (CFD) study. The equations of motion of the glider have been taken from literature and modified as per the laboratory glider design, ignoring the effect of environmental disturbances. A model validation study has been performed on a reference glider [1] to benchmark the model and has been extrapolated on the laboratory glider to confirm its stability at desired equilibrium states.