An underwater glider can move forward with very low power consumption compared with conventional AUVs(Autonomous Underwater Vehicles) which are usually propelled by electrical motordriven thrusters. Due to the particular propulsion mechanism utilizing the change in buoyancy, the turning of the glider is fully coupled with vertical-plane motions. Therefore, dynamic simulation methods for general underwater vehicles are not appropriate for the glider. In this paper, the 6-dof (degrees of freedom) equations of motion for an underwater glider are described in the quaternions and the corresponding simulation code is developed. Using the simulation code, the required range and depth for direction change can be estimated at the initial design stage. Finally, the turning simulation in the presence of current with a simple profile is exemplified to demonstrate the effectiveness of the simulation code.
An underwater glider can move forward with low power consumption using a buoyancy-driven propulsion system (Stommel, 1989). The glider is a small, smart and inexpensive ocean sampling device which has a long operational time. However, due to the particular propulsion mechanism, the maneuverability of the glider is inferior compared to that of general AUVs. In order to design an efficient glider which meets the operational time and desired maneuverability, its dynamic behavior has to be examined carefully at the initial design stage. However, most simulation methods for underwater vehicles have been developed intensively for the conventional vehicle driven by electric thrusters. In case of underwater gliders, the research for the dynamic behavior and control method began not long before. The motion characteristics are similar to those of the aerial glider. The driving force depends on hydrodynamic forces such as drag and lift, which are a function of the advance speed and the angle of attack (Sherman, 2001). Besides, the attitude of the glider is controlled normally by a movable weight such as the battery pack.
