This paper describes the development of a sliding mode controller for the test bed autonomous underwater vehicle (AUV) named by SNUUV I (Seoul National University Underwater Vehicle I). A 6 DOF dynamic model for the SNUUV I is derived with hydrodynamic coefficients, which are estimated with the help of the Extended Kalman Filter (EKF) and a potential code. Based on the mathematical model, a nonlinear sliding mode controller is designed for diving and steering maneuvers of SNUUV I. It is demonstrated that the controller guides the vehicle to follow the desired depth and path with a sufficient accuracy.
In recent years, there have been intensive efforts for the development of AUVs. To control an AUV precisely, its maneuverability and controllability must be clarified based on a mathematical model. The mathematical model contains hydrodynamic forces and moments expressed in terms of a set of hydrodynamic coefficients. Therefore, it is important to know the true values of these coefficients to control the AUV accurately. The hydrodynamic coefficients may be classified into 3 types: linear damping, linear inertial force and nonlinear damping coefficients. Among these, it is known that the linear damping coefficients mostly affect the maneuverability of AUVs (Sen, 2000). The hydrodynamic coefficients for the SNUUV I are estimated based on the EKF and potential calculation. By using these coefficients, the sliding mode controller and the PID controller are designed for the depth and heading control of SNUUV I. The sliding mode controller design is well documented by many researchers. To name a few, Yoerger and Slotine (1985) developed the sliding mode controller for the motion control of remotly operated vehicle (ROV), Cristi et al. (1990) controlled the vertical plane motion of an AUV with sliding mode controller. Marco and Healey (2001) executed velocity,