Abstract
In this paper, in order to overcome certain limitations of previously commercialized platforms, a new integrated unmanned surface vehicle (USV) and unmanned underwater vehicle (UUV) platform connected via underwater cable capable of acquiring real-time underwater data and long-time operation are studied. A catamaran-type USV was designed to overcome the limitations of an ocean environment and to play the role as the hub of power supply and communication for the integrated platform. Meanwhile, the UUV was designed as torpedo-shaped to minimize hydrodynamic resistance and its hardware design was focused on processing and sending the underwater camera and sonar data. The underwater cable driven by a winch system was installed to supply power from the USV to the UUV and to transmit acquired data form underwater sonar sensor or camera. Different from other previously studied cooperation system of USVs and autonomous underwater vehicles (AUVs), the merit of the proposed system is real-time motion coordination control between the USV and UUV while transmitting large amount of data using the tether cable. The main focus of the study is coordination of the UUV with respect to the global positioning system (GPS) attached at USV and verification of its performance throughout field tests. Waypoint tracking control algorithm was designed and implemented on USV and relative heading, distance control for USV–UUV coordination was implemented to UUV. To ensure the integrity of the coordination control of the integrated platform, a study on accurate measurement system of the relative position between the USV and the UUV by using the GPS and the ultrashort baseline (USBL) device was performed. Individual tests were conducted to verify the performance of USBL and AHRS, which provide the position and heading data of UUV among the sensors mounted on the actual platform, and the effectiveness of the obtained sensor data is presented. Using the accurate measurement system, a number of field tests were conducted to verify the performance of the integrated platform.
Highlights
There has been a global increase in the scale of research on developing and operating ocean platforms for ocean surveys and underwater structure management, owing to geopolitical reasons such as importance of maritime transportation routes and safety of navigation, as well as energy-related reasons such as securing underwater resources [1]
The unmanned surface vehicle (USV) performs three major roles in the integrated platform: (1) it serves as a communication hub for transmitting the sensor data of the USV as well as the sonar and image data acquired from the unmanned underwater vehicle (UUV) of the integrated platform; (2) it manages the power supply of the entire system for operating the devices and actuators mounted on the platform and distributes power as required; and (3) it receives position information of the UUV in real time and provides control commands using the attached ultrashort baseline (USBL), while performing waypoint tracking of the UUV
The control commands of the platform are sent and received in packets, and in the case of single command of USV, the control command packet sent from the operation console is input to the micro processing units (MCUs) of USV via the communication hub of USV to execute the control of USV
Summary
There has been a global increase in the scale of research on developing and operating ocean platforms for ocean surveys and underwater structure management, owing to geopolitical reasons such as importance of maritime transportation routes and safety of navigation, as well as energy-related reasons such as securing underwater resources [1]. In these types of platform, USV and AUV are combined to explore a wide range of the water and the position of the USV and the relative position of the AUV can be determined using GPS and hydroacoustic device These platforms were associated with limitations in terms of real-time power supply and large underwater data transmission. The integrated platform developed in this study was aimed at achieving long hours of operation in the seacoast; acquiring a large amount of data and controlling the platform in real time; and accurately measuring the relative position between a USV and UUV using GPS and USBL, even after long hours of operation. By the winch and underwater cable, UUV can approach to inspection targets and receive sonar and video data in real time
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