Abstract: This paper deals with the dynamic model and analysis of sliding mode autopilot system for an Autonomous underwater vehicle to control the motion of the AUV in 3D plane. Autonomous underwater vehicles modelling are tedious task due to its nonlinear behaviour and complex nonlinear equations. To simplify, these equations a reduced order decoupled system is considered in each plane and individual control law has been designed for each plane. The designed autopilot has been applied to AUV dynamic model and the simulations results have been presented.

Keywords: Autonomous Underwater Vehicle (AUV), Sliding Mode Control, Autopilot, MATLAB.