Unmanned Autonomous Surface Vehicle for the Shallow Water Bathymetry Applications

Abstract

Conventionally, survey lounges are engaged to carry out the bathymetric survey for the periodic nautical chart updates and quantification of the dredging requirements. Following close gird lines of hydrographic survey [6] mission by such lounges are limited and the nearshore survey is mostly not possible due to the higher draught. An autonomous Unmanned Autonomous Survey vehicle (UASV) [1] is designed to undertake autonomous surveys and provide real-time transmission of processed data for quick updating of the nautical charts and quick decision making on dredging with minimal efforts. This type of survey is essential to meet the growing demands as ships are becoming larger, with maximum loading and with under keel clearances diminishing rapidly. The navigation system acquires the data from the onboard Motion Reference Unit (MRU) and RTK based GNSS receiver and long-range RADAR sensors and shares the present position, surge velocity, heading and obstacle distance and bearing angles to the mission management system. The collision avoidance system takes over the mission management in case of any obstacle detected within the safer circle. The UASV has twin screw electric propulsion with no physical rudder installed. But the required course control achieved either by controlling the relative thrust between the screws or reversing adequately or by adjusting the azimuth angle by onboard servo controller depending on the manoeuvring requirements during the survey. The thrusters are controlled by the onboard adjustable drives powered by Photo Voltaic (PV) powered hybrid inverters and interfaced to the onboard navigation controller. The onboard batteries can be charged using PV or by AC mains depends on the climate conditions. An open-source Offline map API is used to create Graphical User Interface (GUI) to visualize the mission plan and present location of the craft and display the depth at the surveyed paths. UASV control algorithms such as mission control, navigation control, course control, collision avoidance and survey telemetry systems are implemented in a Field Programmable Gate Array (FPGA) based real-time controller programmed with LabVIEW. The echo sounder/multibeam echo sounder is connected to the survey telemetry system based on the survey requirement. The survey telemetry system is interfaced to the navigation system to obtain the precise sounding location. The telemetry system is designed to acquire the tide from nearby Automated Tide Gauge (ATG) system using marine IoT interface and real-time motion data from MRU for compensation to arrive accurate nautical depth. All the real-time survey and condition monitoring parameters acquired are logged and the file will be saved to the onboard internal storage also share to the remote-control centre using long range RF link and also uploaded to the remote FTP server. This paper details the design of electric propulsion system, sizing of onboard power storage, Mission controller, Navigation controller, Collision avoidance system, Condition monitoring system, survey telemetry system, Graphical User Interface application and long-range wireless system based remote control station.