Pub Date : 2019-06-17DOI: 10.1109/OCEANSE.2019.8867392
Sriharsha Bhat, Ivan Stenius, Nils Bore, Josefine Severholt, Carl Ljung, Ignacio Torroba Balmori
Cyber-physical systems (CPSs) encompass a network of sensors and actuators that are monitored, controlled and integrated by a computing and communication core. As autonomous underwater vehicles (AUVs) become more intelligent and connected, new use cases in ocean production, security and environmental monitoring become feasible. Swarms of small, affordable and hydrobatic AUVs can be beneficial in substance cloud tracking and algae farming, and a CPS linking the AUVs with multi-fidelity simulations can improve performance while reducing risks and costs. In this paper, we present a CPS concept tightly linking the AUV network in ROS to virtual validation using Simulink and Gazebo. A robust hardware-software interface using the open-source UAVCAN-ROS bridge is described for enabling hardware-in-the-loop validation. Hardware features of the hydrobatic SAM AUV are described, with a focus on subsystem integration. Results presented include pre-tuning of controllers, validation of mission plans in simulation and real time subsystem performance in tank tests. These first results demonstrate the interconnection between different system elements and offer a proof of concept.
{"title":"Towards a Cyber-Physical System for Hydrobatic AUVs","authors":"Sriharsha Bhat, Ivan Stenius, Nils Bore, Josefine Severholt, Carl Ljung, Ignacio Torroba Balmori","doi":"10.1109/OCEANSE.2019.8867392","DOIUrl":"https://doi.org/10.1109/OCEANSE.2019.8867392","url":null,"abstract":"Cyber-physical systems (CPSs) encompass a network of sensors and actuators that are monitored, controlled and integrated by a computing and communication core. As autonomous underwater vehicles (AUVs) become more intelligent and connected, new use cases in ocean production, security and environmental monitoring become feasible. Swarms of small, affordable and hydrobatic AUVs can be beneficial in substance cloud tracking and algae farming, and a CPS linking the AUVs with multi-fidelity simulations can improve performance while reducing risks and costs. In this paper, we present a CPS concept tightly linking the AUV network in ROS to virtual validation using Simulink and Gazebo. A robust hardware-software interface using the open-source UAVCAN-ROS bridge is described for enabling hardware-in-the-loop validation. Hardware features of the hydrobatic SAM AUV are described, with a focus on subsystem integration. Results presented include pre-tuning of controllers, validation of mission plans in simulation and real time subsystem performance in tank tests. These first results demonstrate the interconnection between different system elements and offer a proof of concept.","PeriodicalId":375793,"journal":{"name":"OCEANS 2019 - Marseille","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121745403","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-06-17DOI: 10.1109/OCEANSE.2019.8867277
I. Masmitja, S. Gomáriz, Joaquín Del-Río, B. Kieft, T. O'Reilly, J. Aguzzi, P. Bouvet, C. Fannjiang, K. Katija
The use of autonomous underwater vehicles for ocean research has increased as they have a better cost-to-performance ratio than crewed oceanographic vessels. For example, autonomous surface vehicles (e.g. a Wave Glider) can be used to localise and track targets even in the deep-sea. While other researchers have focused on target tracking using acoustic modems, none explored up to date the area-only target tracking methodology. Here we present such a novel method with commercially available acoustic tags, thereby reducing the costs and complexity over other tracking systems. Moreover, this method can be used to track small targets (e.g., jellyfish) due to the tag’s small size. The methodology behind the area-only technique is shown, and results from field tests conducted in Monterey Bay are also presented.
{"title":"Area-only method for underwater object tracking using autonomous vehicles","authors":"I. Masmitja, S. Gomáriz, Joaquín Del-Río, B. Kieft, T. O'Reilly, J. Aguzzi, P. Bouvet, C. Fannjiang, K. Katija","doi":"10.1109/OCEANSE.2019.8867277","DOIUrl":"https://doi.org/10.1109/OCEANSE.2019.8867277","url":null,"abstract":"The use of autonomous underwater vehicles for ocean research has increased as they have a better cost-to-performance ratio than crewed oceanographic vessels. For example, autonomous surface vehicles (e.g. a Wave Glider) can be used to localise and track targets even in the deep-sea. While other researchers have focused on target tracking using acoustic modems, none explored up to date the area-only target tracking methodology. Here we present such a novel method with commercially available acoustic tags, thereby reducing the costs and complexity over other tracking systems. Moreover, this method can be used to track small targets (e.g., jellyfish) due to the tag’s small size. The methodology behind the area-only technique is shown, and results from field tests conducted in Monterey Bay are also presented.","PeriodicalId":375793,"journal":{"name":"OCEANS 2019 - Marseille","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126064117","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-06-17DOI: 10.1109/OCEANSE.2019.8867158
Fankai Kong, Weiming Su, Hua-qiu Ding
As the kernel part of the vertical-axis tidal turbine, variable-pitch mechanism determines the self-startup ability and energy capture efficiency of the turbine. In order to improve the energy capture efficiency, a variable-pitch mechanism of tidal turbine based on the principle of space lever is proposed. The motion simulation is carried out by using PRO/E. The rationality and correctness of variable-pitch mechanism design are verified by comparing the motion simulation curve with the theoretical diagram. The forces acting on the blades at every position in a rotating cycle with different eccentricity are analyzed by using FLUENT, and the torque of each blade to the center of rotation and its synthetic torque are obtained which provides date for the dynamic analysis of the variable-pitch mechanism. The power bond graph method is used to analyze the dynamic characteristics. It’s proved that the turbine with variable-pitch mechanism has higher energy capture efficiency. The first ten natural frequencies are obtained by model analysis of the key components of the variable-pitch mechanism. By comparing with the tidal load frequency and the impeller rotation frequency, it is proved that there is no danger of resonance in the variable-pitch mechanism of the tidal turbine.
{"title":"Design and Analysis of Variable-pitch Mechanism of Vertical-axis Tidal turbine","authors":"Fankai Kong, Weiming Su, Hua-qiu Ding","doi":"10.1109/OCEANSE.2019.8867158","DOIUrl":"https://doi.org/10.1109/OCEANSE.2019.8867158","url":null,"abstract":"As the kernel part of the vertical-axis tidal turbine, variable-pitch mechanism determines the self-startup ability and energy capture efficiency of the turbine. In order to improve the energy capture efficiency, a variable-pitch mechanism of tidal turbine based on the principle of space lever is proposed. The motion simulation is carried out by using PRO/E. The rationality and correctness of variable-pitch mechanism design are verified by comparing the motion simulation curve with the theoretical diagram. The forces acting on the blades at every position in a rotating cycle with different eccentricity are analyzed by using FLUENT, and the torque of each blade to the center of rotation and its synthetic torque are obtained which provides date for the dynamic analysis of the variable-pitch mechanism. The power bond graph method is used to analyze the dynamic characteristics. It’s proved that the turbine with variable-pitch mechanism has higher energy capture efficiency. The first ten natural frequencies are obtained by model analysis of the key components of the variable-pitch mechanism. By comparing with the tidal load frequency and the impeller rotation frequency, it is proved that there is no danger of resonance in the variable-pitch mechanism of the tidal turbine.","PeriodicalId":375793,"journal":{"name":"OCEANS 2019 - Marseille","volume":"04 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127345209","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-06-17DOI: 10.1109/OCEANSE.2019.8867230
Song Yang, Sartaj Khan, Xing Chuanxi, Zhang Yifeng, Piao Shengchun
This paper presents the design and realization of a buoy for coastal ocean acoustic tomography based on the narrowband-internet of things (NB-IoT) technology. The body of the buoy is made of unplasticised polyvinyl chloride (PVCU) pipe material. The buoy consists of two main parts: surface pharos and buoy body. The surface pharos part further consists of NB-IoT and global positioning system (GPS) modules which realize buoys networking, distributed time synchronization, and remote real-time monitoring and control. Whereas, the built-in data reception system, signal transmission, and power amplifier are inserted in the buoy body. The system uses 1pulse per second GPS (1PPSGPS) to trigger signal for synchronizing transmission and reception. The buoys are tested in the acoustic tomography experiment conducted at the coast of east China sea (ECS) in 2014. From the experiment, the results show that the self-organizing network (SON) with this kind of buoys can work well and achieve better signals which are successfully applied to the inversion of sound speed profile (SSP). The accuracy of the SSP inversion indicates system reliability and stability. The average power for the whole system is 1W. With lower power consumption and cost, the system is able to be widely and equally applied to ocean acoustic tomography, marine monitoring, and other fields.
{"title":"Design and Realization of a Buoy for Ocean Acoustic Tomography in Coastal Sea based on NB-IoT Technology","authors":"Song Yang, Sartaj Khan, Xing Chuanxi, Zhang Yifeng, Piao Shengchun","doi":"10.1109/OCEANSE.2019.8867230","DOIUrl":"https://doi.org/10.1109/OCEANSE.2019.8867230","url":null,"abstract":"This paper presents the design and realization of a buoy for coastal ocean acoustic tomography based on the narrowband-internet of things (NB-IoT) technology. The body of the buoy is made of unplasticised polyvinyl chloride (PVCU) pipe material. The buoy consists of two main parts: surface pharos and buoy body. The surface pharos part further consists of NB-IoT and global positioning system (GPS) modules which realize buoys networking, distributed time synchronization, and remote real-time monitoring and control. Whereas, the built-in data reception system, signal transmission, and power amplifier are inserted in the buoy body. The system uses 1pulse per second GPS (1PPSGPS) to trigger signal for synchronizing transmission and reception. The buoys are tested in the acoustic tomography experiment conducted at the coast of east China sea (ECS) in 2014. From the experiment, the results show that the self-organizing network (SON) with this kind of buoys can work well and achieve better signals which are successfully applied to the inversion of sound speed profile (SSP). The accuracy of the SSP inversion indicates system reliability and stability. The average power for the whole system is 1W. With lower power consumption and cost, the system is able to be widely and equally applied to ocean acoustic tomography, marine monitoring, and other fields.","PeriodicalId":375793,"journal":{"name":"OCEANS 2019 - Marseille","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125100642","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-06-17DOI: 10.1109/OCEANSE.2019.8867529
Keyao Fu, Peng Wang, Bin Sun, Liang Zhao, Chuang Liu
Most of Unmanned Underwater Vehicles (UUVs) can only perform single-locomotion mode, such as propeller- driven, gliding, paddling and so on. So it is difficult for these vehicles to deal with complicated missions at a fixed-point or in some limited and dangerous spaces. Additionally, energy supply is one of the important factors that seriously affects the detection range and endurance of the UUVs which are not capable to obtain power-importing from outside. As a result of these concerns, we propose a new solar-powered bionic underwater glider with multi-locomotion modes (SBUG). Based on the sea turtles hydrofoil motion and the fish body and /or caudal fin (BCF) locomotion, the bionic structure design of the SBUG includes basically two main parts, a pectoral fin actuation and a caudal actuation. The three-degree-of-freedom (3DOF) pectoral fin actuation and the 2DOF caudal actuation ensure that the SBUG can easily change locomotion modes between gliding, paddling, flapping, tail wagging and walking for various tasks. The flexible solar arrays are attached on the upper curved surface shell and wings of the SBUG so as to provide energy support to increase the voyage time. The basic concept, mechanical design and development of the SBUG are presented in this paper. Moreover, the movement performance of the mechanical prototype is confirmed through in-water trials.
{"title":"Design, Development and Testing of a New Solar-powered Bionic Underwater Glider with Multi-locomotion Modes","authors":"Keyao Fu, Peng Wang, Bin Sun, Liang Zhao, Chuang Liu","doi":"10.1109/OCEANSE.2019.8867529","DOIUrl":"https://doi.org/10.1109/OCEANSE.2019.8867529","url":null,"abstract":"Most of Unmanned Underwater Vehicles (UUVs) can only perform single-locomotion mode, such as propeller- driven, gliding, paddling and so on. So it is difficult for these vehicles to deal with complicated missions at a fixed-point or in some limited and dangerous spaces. Additionally, energy supply is one of the important factors that seriously affects the detection range and endurance of the UUVs which are not capable to obtain power-importing from outside. As a result of these concerns, we propose a new solar-powered bionic underwater glider with multi-locomotion modes (SBUG). Based on the sea turtles hydrofoil motion and the fish body and /or caudal fin (BCF) locomotion, the bionic structure design of the SBUG includes basically two main parts, a pectoral fin actuation and a caudal actuation. The three-degree-of-freedom (3DOF) pectoral fin actuation and the 2DOF caudal actuation ensure that the SBUG can easily change locomotion modes between gliding, paddling, flapping, tail wagging and walking for various tasks. The flexible solar arrays are attached on the upper curved surface shell and wings of the SBUG so as to provide energy support to increase the voyage time. The basic concept, mechanical design and development of the SBUG are presented in this paper. Moreover, the movement performance of the mechanical prototype is confirmed through in-water trials.","PeriodicalId":375793,"journal":{"name":"OCEANS 2019 - Marseille","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131351964","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-06-17DOI: 10.1109/OCEANSE.2019.8867565
Manchun Lei, Audrey Minghelli, A. Fiandrino
This study concerns the spectral behavior of remote sensing reflectance Rrs of Thau lagoon water during the anoxic crisis in the summer of 2003 and 2006. The proliferation of photosynthetic sulfur-oxidizing bacteria (SOB) in anoxic water make the water color becomes opaque and turbid until milky. An identification method using 665 nm, 709 nm and 754 nm bands of Medium Resolution Imaging Spectrometer (MERIS) sensor is proposed to identify the total anoxic water filled by SOB. The reflectance of the SOB layer is described as a specific reflectance relating to the SOB concentration. The results show that SOB contaminated water during the anoxic crisis can be quantitatively remote sensed by multispectral sensor.
{"title":"Analysis and modelling of remote sensing reflectance during anoxic crisis in the Thau lagoon using satellite images","authors":"Manchun Lei, Audrey Minghelli, A. Fiandrino","doi":"10.1109/OCEANSE.2019.8867565","DOIUrl":"https://doi.org/10.1109/OCEANSE.2019.8867565","url":null,"abstract":"This study concerns the spectral behavior of remote sensing reflectance Rrs of Thau lagoon water during the anoxic crisis in the summer of 2003 and 2006. The proliferation of photosynthetic sulfur-oxidizing bacteria (SOB) in anoxic water make the water color becomes opaque and turbid until milky. An identification method using 665 nm, 709 nm and 754 nm bands of Medium Resolution Imaging Spectrometer (MERIS) sensor is proposed to identify the total anoxic water filled by SOB. The reflectance of the SOB layer is described as a specific reflectance relating to the SOB concentration. The results show that SOB contaminated water during the anoxic crisis can be quantitatively remote sensed by multispectral sensor.","PeriodicalId":375793,"journal":{"name":"OCEANS 2019 - Marseille","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123908320","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-06-17DOI: 10.1109/OCEANSE.2019.8867135
S. H. Huang, T.C. Yang
Direction of arrival (DOA) is estimated for a small circular array with six elements and a radius of 0.0875 m using superdirective beamforming. It is well known that such an array has a wide beam width using conventional beamforming (CBF). CBF yields high sidelobe levels which cause the signal from one direction to leak into another direction. A superdirective beamforming method based on deconvolution (T. C. Yang, IEEE J. Oceanic Eng., 44, 156-166, 2019) has been shown to yield high bearing resolution, high directivity index or array gain, and strong interference rejection compared with CBF for an array of 16 elements, for which the beam pattern is shift-invariant. For a circular array of 6 element, the beam pattern is shift variant, a modified Richardson-Lucy deconvolution method is used.This paper presents the simulation results, and experimental test results in a tank. A small circular array can be used in principle to estimate the positions of neighboring node, and differentiate signals from different sources to avoid signal collisions in an underwater communication network.
{"title":"Direction of Arrival Estimation Using a Small Circular Array","authors":"S. H. Huang, T.C. Yang","doi":"10.1109/OCEANSE.2019.8867135","DOIUrl":"https://doi.org/10.1109/OCEANSE.2019.8867135","url":null,"abstract":"Direction of arrival (DOA) is estimated for a small circular array with six elements and a radius of 0.0875 m using superdirective beamforming. It is well known that such an array has a wide beam width using conventional beamforming (CBF). CBF yields high sidelobe levels which cause the signal from one direction to leak into another direction. A superdirective beamforming method based on deconvolution (T. C. Yang, IEEE J. Oceanic Eng., 44, 156-166, 2019) has been shown to yield high bearing resolution, high directivity index or array gain, and strong interference rejection compared with CBF for an array of 16 elements, for which the beam pattern is shift-invariant. For a circular array of 6 element, the beam pattern is shift variant, a modified Richardson-Lucy deconvolution method is used.This paper presents the simulation results, and experimental test results in a tank. A small circular array can be used in principle to estimate the positions of neighboring node, and differentiate signals from different sources to avoid signal collisions in an underwater communication network.","PeriodicalId":375793,"journal":{"name":"OCEANS 2019 - Marseille","volume":"121 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116163570","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-06-17DOI: 10.1109/OCEANSE.2019.8867282
C. Richards, Alan Barrett, I. Maguire, Sandra Kwiatkowska, F. Regan
Biofouling on deployed in-situ sensors without regular removal or cleaning can disrupt sensor data collected. The current replacement antifouling (AF) materials under development are largely unsuited to sensor technologies as they have been developed with large scale applications in mind, such as those required by the shipping industry. Therefore, a strategy for the development of novel, sustainable, antifouling materials for sensor applications is required. Bio-inspiration refers to adapting strategies already developed in the natural world to problems encountered in modern science and technology. Engineered surfaces capable of controlling cellular behaviour under natural conditions are challenging to design due to the diversity of attaching cell types in environments such as marine waters, where many variations in cell shape, size and adhesion strategy exist. Nevertheless, understanding interactions between a cell and a potential substrate for adhesion, including topographically driven settlement cues, offers a route to designing surfaces capable of controlling cell settlement. Biomimetic design of artificial surfaces, based upon microscale features from natural surfaces, can be utilized as model surfaces to understand cell-surface interactions. In this study it was hypothesized that an AF effect could be induced through the replication of a synthetic surface. In this paper, the potential of biomimetic antifouling materials for application in the environment is discussed. We outline strategies for the identification and production of novel biomimetic antifouling approaches and discuss the pitfalls of developing antifouling materials based on biomimetic design.
{"title":"Marine inspired textured materials for reduction of biofouling on surfaces","authors":"C. Richards, Alan Barrett, I. Maguire, Sandra Kwiatkowska, F. Regan","doi":"10.1109/OCEANSE.2019.8867282","DOIUrl":"https://doi.org/10.1109/OCEANSE.2019.8867282","url":null,"abstract":"Biofouling on deployed in-situ sensors without regular removal or cleaning can disrupt sensor data collected. The current replacement antifouling (AF) materials under development are largely unsuited to sensor technologies as they have been developed with large scale applications in mind, such as those required by the shipping industry. Therefore, a strategy for the development of novel, sustainable, antifouling materials for sensor applications is required. Bio-inspiration refers to adapting strategies already developed in the natural world to problems encountered in modern science and technology. Engineered surfaces capable of controlling cellular behaviour under natural conditions are challenging to design due to the diversity of attaching cell types in environments such as marine waters, where many variations in cell shape, size and adhesion strategy exist. Nevertheless, understanding interactions between a cell and a potential substrate for adhesion, including topographically driven settlement cues, offers a route to designing surfaces capable of controlling cell settlement. Biomimetic design of artificial surfaces, based upon microscale features from natural surfaces, can be utilized as model surfaces to understand cell-surface interactions. In this study it was hypothesized that an AF effect could be induced through the replication of a synthetic surface. In this paper, the potential of biomimetic antifouling materials for application in the environment is discussed. We outline strategies for the identification and production of novel biomimetic antifouling approaches and discuss the pitfalls of developing antifouling materials based on biomimetic design.","PeriodicalId":375793,"journal":{"name":"OCEANS 2019 - Marseille","volume":"56 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123414321","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-06-17DOI: 10.1109/OCEANSE.2019.8867326
P. B. Garcia‐Rosa, Astrid H. Brodtkorb, A. Sørensen, M. Molinas
For dynamic positioning operations, high-frequency wave induced motions cause excessive control action, and consequently additional power consumption and wear of actuators in the propulsion system. Thus, such operations require the control of only low-frequency motions, which is achieved by proper filtering of high-frequency motions. This study investigates the use of the empirical mode decomposition (EMD) method for wave filtering purposes. EMD is a data-driven method that decomposes an oscillatory waveform into a number of modes from the highest to the lowest frequency. The decomposition process in the standard EMD algorithm relies on repetitive iterations through the entire data span, which is impractical for wave filtering in real-time applications. Thus, an online EMD algorithm is also considered. The online decomposition process features a time lag, and measurements of the ship motions have to be taken at a point ahead of the center of gravity so that high-frequency motions are estimated in advance. In this study, the performance of both standard and online EMD algorithms, in terms of wave filtering and control efforts, is evaluated through a comparison with a nonlinear passive observer (NPO). Furthermore, the time lag of the online EMD is also of interest, as it indicates the required prediction time window. Simulation results with a simple maneuver of a vessel in moderate, and calm seas, show that the control action with wave filtering from the online EMD can be up to 40% lower than with wave filtering from NPO.
{"title":"Evaluation of wave-frequency motions extraction from dynamic positioning measurements using the empirical mode decomposition","authors":"P. B. Garcia‐Rosa, Astrid H. Brodtkorb, A. Sørensen, M. Molinas","doi":"10.1109/OCEANSE.2019.8867326","DOIUrl":"https://doi.org/10.1109/OCEANSE.2019.8867326","url":null,"abstract":"For dynamic positioning operations, high-frequency wave induced motions cause excessive control action, and consequently additional power consumption and wear of actuators in the propulsion system. Thus, such operations require the control of only low-frequency motions, which is achieved by proper filtering of high-frequency motions. This study investigates the use of the empirical mode decomposition (EMD) method for wave filtering purposes. EMD is a data-driven method that decomposes an oscillatory waveform into a number of modes from the highest to the lowest frequency. The decomposition process in the standard EMD algorithm relies on repetitive iterations through the entire data span, which is impractical for wave filtering in real-time applications. Thus, an online EMD algorithm is also considered. The online decomposition process features a time lag, and measurements of the ship motions have to be taken at a point ahead of the center of gravity so that high-frequency motions are estimated in advance. In this study, the performance of both standard and online EMD algorithms, in terms of wave filtering and control efforts, is evaluated through a comparison with a nonlinear passive observer (NPO). Furthermore, the time lag of the online EMD is also of interest, as it indicates the required prediction time window. Simulation results with a simple maneuver of a vessel in moderate, and calm seas, show that the control action with wave filtering from the online EMD can be up to 40% lower than with wave filtering from NPO.","PeriodicalId":375793,"journal":{"name":"OCEANS 2019 - Marseille","volume":"119 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126856251","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-06-17DOI: 10.1109/OCEANSE.2019.8867150
Xionghou Liu, Kun Gao, Jiansheng Tang, Chao Sun, Yixin Yang, Kuan Fan, Jiapeng Liu
The angle resolution of an imaging sonar is generally determined by the obtainable aperture of the receiving hydrophone array. When mounted onto a small underwater platform (such as an underwater unmanned vehicle, UUV and an underwater robot), the aperture of the imaging sonar is strictly constrained by the limited surface space of the platform. To improve the angle resolution of the imaging sonar without requiring a larger-size underwater platform, we propose a high resolution 2-D imaging method using multiple-input multiple-output (MIMO) sonar with Fourier integral method (FIM). This method is termed as MIMO-FIM for short in this paper. MIMO-FIM shares the same sonar array structure and the same orthogonal transmitting waveforms as the MIMO sonar. Different from the MIMO sonar imaging method where the outputs of matched filters are directly collected for multibeam processing, MIMO-FIM uses FIM to process these matched filters’ outputs to extend the aperture of the virtual array. And then, the FIM outputs are imported to beamformers to produce the high resolution 2-D image. Thus, MIMO-FIM has a two-step aperture extending effect. Firstly, the large-aperture virtual array is produced by the MIMO method where the matched filters corresponding to different orthogonal waveforms are used; and secondly an even larger aperture is obtained by FIM where the matched filters outputs are taken as the inputs. Furthermore, we use the time-domain slice window to process outputs of matched filters when using FIM. And the window width and the overlapped ratio of neighboring ones are given. Numerical simulations demonstrate that the proposed MIMO-FIM method shows a better angle resolution than the MIMO sonar and single-input multiple-output (SIMO) sonar, which share the same array physical size and the same working frequency band.
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