Design And Research On The Positioning System Scheme Of Ship Hull Cleaning Robot

As ships sail in the sea for long periods of time,a large number of marine organisms will adhere to the surface of the hull,resulting in reduced sailing speed and increased fuel consumption,which needs to be cleaned regularly.The traditional cleaning method is manual cleaning,which is inefficient and poses safety risks.The emergence of Remotely Operated Vehicles(ROVs)has made it possible to replace manual cleaning with machine cleaning.When using ROVs for hull cleaning,it is difficult to locate the ROV due to the complex underwater acoustic environment and poor visibility of the ship’s docking location,making cleaning difficult.The underwater positioning problem is one of the urgent issues to be solved.In this article,the design of a positioning solution for this scenario is investigated.The main research includes the following parts.The relative positioning of the ROV and the ship being cleaned is designed,i.e.the position of the ROV and the ship being cleaned is measured simultaneously by the robot mother ship to obtain the relative position of the ROV and the ship being cleaned.Positioning accuracy targets are proposed according to the positioning requirements for hull cleaning.The design and analysis of the hardware and software implementation of the system is carried out.The parameters of the sensors that will be used are analyzed and selected according to the positioning solution.The key technologies for the combination of the Strapdown Inertial Navigation System(SINS)and the Doppler Velocity Log(DVL)are analyzed.Firstly,different methods for determining the initial attitude are compared,including dual-vector attitude,multi-vector attitude,and a combination of coarse and fine alignment,and a multi-vector attitude coarse alignment and then fine alignment scheme is determined.Next,the mounting errors of the combination were calibrated and compensated for.Then,a solution is proposed based on the DVL failure problem that arises when cleaning the hull sidewalls.Finally,an accuracy analysis of the combined SINS/DVL positioning is presented.The problems associated with the Ultra Short Baseline Positioning System(USBL)are analyzed.Firstly,a solution is proposed for the problem of hydroacoustic positioning failure due to hull occlusion during bottom cleaning.Secondly,a detailed design of the relative positioning system between the ROV and the ship being cleaned based on the proposed solution is presented.The main installation errors in the system are compensated for through static testing,resulting in a significant improvement in positioning accuracy.Finally,a simulation of the SINS/USBL combination was carried out based on the errors measured in the static tests.The accuracy and stability of the SINS/DVL combination was verified by changing the measurement frequency of the USBL to test the failure mechanism.The combined SINS/DVL/USBL underwater positioning system was investigated.Firstly,the fusion of multi-sensor data using a sequential filtering algorithm was used to analyze the accuracy improvement effect of multi-sensor fusion positioning relative to combined SINS/USBL positioning from different perspectives and to verify the effectiveness of the scheme.Then,post-processing of the multi-sensor data with forward and reverse filtering and data fusion was carried out to further improve the positioning accuracy.Finally,the overall positioning accuracy meets the design requirements and has some anti-interference capability.