A Study of autonomous navigation system for unmanned surface & underwater vehicle

Abstract

In this study, we developed a combined unmanned ocean vehicle for real-time marine exploration and designed a guidance law and controller for autonomous navigation of the platform. The developed unmanned ocean vehicle is a combination of unmanned surface vehicle, underwater vehicle and underwater cable to overcome disadvantages such as position accumulation error, limit of battery capacity, and inability to secure real-time data of existing unmanned underwater vehicle. The combined unmanned ocean vehicle, Global Positioning System(GPS) and Ultra Short Base Line(USBL) sensors mounted on unmanned surface vehicle, unmanned underwater vehicle can be used to know the location of current exploration area and power supply for a long time on unmanned submarine using high capacity battery. It is also possible to check the terrain information of the exploration area, the status of unmanned underwater vehicle, and camera information in real-time using underwater cable. However, such combined unmanned ocean vehicle, in which the surface and underwater vehicles are connected by underwater cables, will encounter disturbances such as current, waves, and other disturbances due to dynamic movement of underwater cables. In this study, equations are derived for the motion of a combined unmanned ocean vehicle. Simulation was carried out using the developed equations of motion and the motion of the combined unmanned ocean vehicle was confirmed. Movement of the unmanned underwater vehicle was also observed according to disturbance generated in the underwater cable. In addition, autonomous navigation system required to perform a given task was studied, The unmanned surface vehicle follows a given way-point through the Pure-Pursuit method which is a geometric path-following method. The unmanned underwater vehicle is geometrically defined by the relative position and the relative orientation angle of each platform so that it can maintain a certain distance and direction angle. Combined unmanned ocean vehicle was designed to take lead-follower control from defined geometric definition. Therefore, anti-windup PID controller and backstepping controller based on disturbance robust Lyapunov function were designed in this study. Dynamics simulation was performed to verify the designed induction law and the performance of the controller. Finally, to verify the proposed algorithm, we constructed a rubber boat hull and a torpedo type unmanned underwater vehicle and constructed a hardware system for autonomous navigation of the platform. We investigated the performance of a combined unmanned ocean vehicle and controller by performing field tests and performed tests for sensors mounted on the platform.