Pub Date : 2010-05-24DOI: 10.1109/OCEANSSYD.2010.5603819
N. Nowsheen, C. Benson, M. Frater
Contemporary underwater acoustic networks use low frequency modems. While these modems can provide long range communication, their low operating frequencies mean that only low channel bandwidth is available, which results in slow data rates. This motivates our development of a high frequency modem which offers the potential for large channel bandwidth, and hence greater link capacity. There is a range-frequency trade-off because absorption becomes very high at high frequency. Our intended operating frequencies from 100 kHz to 1 MHz would only support link ranges perhaps from 1 km down to under 100m, with communication ranges longer than this requiring forwarding over a network. Reconfigurable computing based Field Programmable Gate Arrays (FPGAs) are used to accelerate product development and support evolution of fielded systems. Given the immaturity of the field of underwater communication, a reconfigurable modem is a valuable tool for development and testing modem techniques. We present a design idea to implement an acoustic modem solely in FPGA, whereas most existing modems are implemented as a combination of FPGA and DSP processors. Aside from simple anti-aliasing filters, which could be incorporated in the preamplifier stage, the modem does all of its processing in the digital domain - maximising flexibility. In this work, we describe the initial design and architecture of our software based acoustic modem that avoids the monetary cost or time investment required to design a commercial modem or custom hardware for many applications. Our demodulator is implemented using a Costas loop which performs both suppressed carrier reconstruction and synchronous data detection within the loop. Results from initial implementation are also reported in this paper.
{"title":"Design of a high frequency FPGA acoustic modem for underwater communication","authors":"N. Nowsheen, C. Benson, M. Frater","doi":"10.1109/OCEANSSYD.2010.5603819","DOIUrl":"https://doi.org/10.1109/OCEANSSYD.2010.5603819","url":null,"abstract":"Contemporary underwater acoustic networks use low frequency modems. While these modems can provide long range communication, their low operating frequencies mean that only low channel bandwidth is available, which results in slow data rates. This motivates our development of a high frequency modem which offers the potential for large channel bandwidth, and hence greater link capacity. There is a range-frequency trade-off because absorption becomes very high at high frequency. Our intended operating frequencies from 100 kHz to 1 MHz would only support link ranges perhaps from 1 km down to under 100m, with communication ranges longer than this requiring forwarding over a network. Reconfigurable computing based Field Programmable Gate Arrays (FPGAs) are used to accelerate product development and support evolution of fielded systems. Given the immaturity of the field of underwater communication, a reconfigurable modem is a valuable tool for development and testing modem techniques. We present a design idea to implement an acoustic modem solely in FPGA, whereas most existing modems are implemented as a combination of FPGA and DSP processors. Aside from simple anti-aliasing filters, which could be incorporated in the preamplifier stage, the modem does all of its processing in the digital domain - maximising flexibility. In this work, we describe the initial design and architecture of our software based acoustic modem that avoids the monetary cost or time investment required to design a commercial modem or custom hardware for many applications. Our demodulator is implemented using a Costas loop which performs both suppressed carrier reconstruction and synchronous data detection within the loop. Results from initial implementation are also reported in this paper.","PeriodicalId":129808,"journal":{"name":"OCEANS'10 IEEE SYDNEY","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134294335","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 : 2010-05-24DOI: 10.1109/OCEANSSYD.2010.5603859
Tjasa Boh, J. Billingsley, R. Bradbeer, P. Hodgson
The Bekker Theory of Locomotion has long been the leading applied theory when it comes to calculating and predicting soil-tyre interaction for terrestrial wheeled and tracked vehicles. Whilst the theory is applicable for terrestrial systems, there is no evidence to suggest it also applies under water. Furthermore, the complications of measuring the required soil parameters in marine substratum makes it difficult to apply. This paper explores the slip-based approach to the Bekker theorem and suggests an experiment designed to validate this theorem for underwater applications.
{"title":"Terramechanics based traction control of underwater wheeled robot","authors":"Tjasa Boh, J. Billingsley, R. Bradbeer, P. Hodgson","doi":"10.1109/OCEANSSYD.2010.5603859","DOIUrl":"https://doi.org/10.1109/OCEANSSYD.2010.5603859","url":null,"abstract":"The Bekker Theory of Locomotion has long been the leading applied theory when it comes to calculating and predicting soil-tyre interaction for terrestrial wheeled and tracked vehicles. Whilst the theory is applicable for terrestrial systems, there is no evidence to suggest it also applies under water. Furthermore, the complications of measuring the required soil parameters in marine substratum makes it difficult to apply. This paper explores the slip-based approach to the Bekker theorem and suggests an experiment designed to validate this theorem for underwater applications.","PeriodicalId":129808,"journal":{"name":"OCEANS'10 IEEE SYDNEY","volume":"37 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134269096","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 : 2010-05-24DOI: 10.1109/OCEANSSYD.2010.5603512
T. Horiuchi, F. Wolk, P. Macoun
The stability of the conductivity sensor is a key consideration for the long-term deployments of the instruments on mooring and observatories, because the conductivity measurement is very sensitive to the accumulation of organisms (bio-fouling) inside the sensor. We tested the performance of a conductivity sensor, the ALEC CTW, which features a simple but effective wiper mechanism to keep the sensing cavity of the conductivity cell free of bio-fouling. The sensor was deployed for a period of 12 months on the Victoria Experimental Network Under the Sea (VENUS) observatory, operated by the University of Victoria in British Columbia, Canada. The VENUS observatory provided power and data telemetry to monitor the sensor's performance in real time. A post recovery calibration of the conductivity sensor showed that the wiper mechanism was effective in maintaining the sensors calibration.
{"title":"Long-term stability of a new conductivity-temperature sensor tested on the VENUS cabled observatory","authors":"T. Horiuchi, F. Wolk, P. Macoun","doi":"10.1109/OCEANSSYD.2010.5603512","DOIUrl":"https://doi.org/10.1109/OCEANSSYD.2010.5603512","url":null,"abstract":"The stability of the conductivity sensor is a key consideration for the long-term deployments of the instruments on mooring and observatories, because the conductivity measurement is very sensitive to the accumulation of organisms (bio-fouling) inside the sensor. We tested the performance of a conductivity sensor, the ALEC CTW, which features a simple but effective wiper mechanism to keep the sensing cavity of the conductivity cell free of bio-fouling. The sensor was deployed for a period of 12 months on the Victoria Experimental Network Under the Sea (VENUS) observatory, operated by the University of Victoria in British Columbia, Canada. The VENUS observatory provided power and data telemetry to monitor the sensor's performance in real time. A post recovery calibration of the conductivity sensor showed that the wiper mechanism was effective in maintaining the sensors calibration.","PeriodicalId":129808,"journal":{"name":"OCEANS'10 IEEE SYDNEY","volume":"69 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130311660","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 : 2010-05-24DOI: 10.1109/OCEANSSYD.2010.5603968
K. Reichert, J. Dannenberg, Henk J. J. van den Boom
Nautical X-Band radars used for navigation can also be used to determine spectral and individual wave properties. The sea surface reflects the incident radar beams and wave fronts become visible as stripe like pattern of high back scatter on the radar screen. When connected to a conventional nautical X-Band radar, the Wave Monitoring System WaMoS II exploits this imaging of waves to detect full directional wave spectra and to derive statistical sea state parameters as well as surface currents. WaMoS II is continuously improved with new features being developed. In particular, the sea surface elevation maps derived by WaMoS II allow to investigate and describe the spatial and temporal development of 3D ocean surface waves. The European Joint Industry Project ‘On board Wave and Motion Estimator (OWME)’ used this measurement technique to provide the wave information that is required to predict periods of quiescent vessel motions. A task that offers valuable support for various offshore operations like e.g. the tensioning of a tanker or the landing of a helicopter. This contribution gives an overview of the overall OWME system design showing first validation results, focusing on the method to derive wave trains using the WaMoS II system.
{"title":"X-Band radar derived sea surface elevation maps as input to ship motion forecasting","authors":"K. Reichert, J. Dannenberg, Henk J. J. van den Boom","doi":"10.1109/OCEANSSYD.2010.5603968","DOIUrl":"https://doi.org/10.1109/OCEANSSYD.2010.5603968","url":null,"abstract":"Nautical X-Band radars used for navigation can also be used to determine spectral and individual wave properties. The sea surface reflects the incident radar beams and wave fronts become visible as stripe like pattern of high back scatter on the radar screen. When connected to a conventional nautical X-Band radar, the Wave Monitoring System WaMoS II exploits this imaging of waves to detect full directional wave spectra and to derive statistical sea state parameters as well as surface currents. WaMoS II is continuously improved with new features being developed. In particular, the sea surface elevation maps derived by WaMoS II allow to investigate and describe the spatial and temporal development of 3D ocean surface waves. The European Joint Industry Project ‘On board Wave and Motion Estimator (OWME)’ used this measurement technique to provide the wave information that is required to predict periods of quiescent vessel motions. A task that offers valuable support for various offshore operations like e.g. the tensioning of a tanker or the landing of a helicopter. This contribution gives an overview of the overall OWME system design showing first validation results, focusing on the method to derive wave trains using the WaMoS II system.","PeriodicalId":129808,"journal":{"name":"OCEANS'10 IEEE SYDNEY","volume":"258 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114479346","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 : 2010-05-24DOI: 10.1109/OCEANSSYD.2010.5603618
S. Shankar, M. Chitre, Melani Jayasuria
The design of a communication system is closely linked to assumptions about the nature of the channel. A vast majority of the components of a modern communication system are implemented in software, affording us the ability to fine tune their parameters during operation. The objective for tuning the parameters could be to optimize data rates, protect against errors, minimize power, and so on. If the physics of the channel is completely known, it is possible to determine the values of these parameters for a given objective. However in practice, it is quite difficult to know the state of the channel completely. The parameters usually interact with each other, so tuning them in isolation is often not possible. We present a data driven approach for tuning the physical layer parameters of a communication link to optimize data rates, assuming the channel remains static over the course of a file transfer. Our approach does not need any knowledge of the physics of the channel. We illustrate the application of our approach in the context of an underwater communication link.
{"title":"Data driven algorithms to tune physical layer parameters of an underwater communication link","authors":"S. Shankar, M. Chitre, Melani Jayasuria","doi":"10.1109/OCEANSSYD.2010.5603618","DOIUrl":"https://doi.org/10.1109/OCEANSSYD.2010.5603618","url":null,"abstract":"The design of a communication system is closely linked to assumptions about the nature of the channel. A vast majority of the components of a modern communication system are implemented in software, affording us the ability to fine tune their parameters during operation. The objective for tuning the parameters could be to optimize data rates, protect against errors, minimize power, and so on. If the physics of the channel is completely known, it is possible to determine the values of these parameters for a given objective. However in practice, it is quite difficult to know the state of the channel completely. The parameters usually interact with each other, so tuning them in isolation is often not possible. We present a data driven approach for tuning the physical layer parameters of a communication link to optimize data rates, assuming the channel remains static over the course of a file transfer. Our approach does not need any knowledge of the physics of the channel. We illustrate the application of our approach in the context of an underwater communication link.","PeriodicalId":129808,"journal":{"name":"OCEANS'10 IEEE SYDNEY","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116976456","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 : 2010-05-24DOI: 10.1109/OCEANSSYD.2010.5603944
D. Ogburn, Thomas Q. Zeng
It is a common understanding that coastal wetland plays an important role in marine fisheries recruitment. However, mechanistic detail of the processes that link the two ecosystems is not well defined. This study aims to describe and map ecological landscape features of a saltmarsh-estuary ecotone at the entrance to Mambo Creek in Salamander Bay, at Port Stephens, on the southeast coast of Australia. The creek drains from 175 ha of estuarine-freshwater area which forms part of the Tomaree Wetland complex. Based on field surveyed data and GIS analysis, a dynamical system is depicted of a tidal salt-wedge that results from the interaction of the wetland and estuary water. The creek entrance lies inside the extensive Posidonia seagrass beds of Salamander Bay. It is constricted by a shallow sandbar at the entrance and is fringed by mangroves that stabilize the creek channel. Analysis of the ebb-tide outflow from the wetland shows it contains micro-particles (10–100 µm diameter) at densities >20,000 particles ml−1, high levels of H2S, low pH, lows-alinity and low dissolved oxygen and is thus adverse for most fish fry. In the vicinity of the entrance channel to the creek: i) the outflow from the wetland forms a tidal salt wedge and disperses across the water surface where it meets denser saline estuary water; ii) the micro-particles sink out of the surface layer at the tip of the salt wedge in a sharp, readily observable boundary, due to flocculation effects. At this boundary or ecotone, the continuous presence of a “feeding prism” which contains very large numbers of at least three species of marine fish fry <20 mm total length, particularly in warmer months, was observed. The fry remain only within this creek area and feed on the ad-libitum supply of outwelling wetland micro-food particles while swimming in near oceanic condition water below the salt wedge; iii) the seston material varies with season; in warmer months it is principally a mixture of purple and green bacteria coated micro-particles and in cooler months detritus predominates; iv) the location of the halocline is dynamic and is related to the morphology of the creek and tide; and, v) the creek entrance also contains a deeper area in which small numbers of large apparently gravid fish were regularly observed. The fish fry aggregations are mapped in relation to the halocline in space and time during summer and winter seasons and linked to tidal sea-level and the morphology of the creek. The authors suggest the “feeding prism” ecotone is an important link between wetland process functions and marine fish recruitment for at least three commercially and recreationally important coastal fish species and perhaps others. It is this ecotone that needs to be considered as a focus of management measures and environmental impact assessment associated with adjoining developments and landscape modifications that may affect coastal processes in the vicinity of the creek. For example, the sand-dune syst
{"title":"Mapping the fish fry feeding prism in a saltmarsh-estuary ecotone","authors":"D. Ogburn, Thomas Q. Zeng","doi":"10.1109/OCEANSSYD.2010.5603944","DOIUrl":"https://doi.org/10.1109/OCEANSSYD.2010.5603944","url":null,"abstract":"It is a common understanding that coastal wetland plays an important role in marine fisheries recruitment. However, mechanistic detail of the processes that link the two ecosystems is not well defined. This study aims to describe and map ecological landscape features of a saltmarsh-estuary ecotone at the entrance to Mambo Creek in Salamander Bay, at Port Stephens, on the southeast coast of Australia. The creek drains from 175 ha of estuarine-freshwater area which forms part of the Tomaree Wetland complex. Based on field surveyed data and GIS analysis, a dynamical system is depicted of a tidal salt-wedge that results from the interaction of the wetland and estuary water. The creek entrance lies inside the extensive Posidonia seagrass beds of Salamander Bay. It is constricted by a shallow sandbar at the entrance and is fringed by mangroves that stabilize the creek channel. Analysis of the ebb-tide outflow from the wetland shows it contains micro-particles (10–100 µm diameter) at densities >20,000 particles ml−1, high levels of H2S, low pH, lows-alinity and low dissolved oxygen and is thus adverse for most fish fry. In the vicinity of the entrance channel to the creek: i) the outflow from the wetland forms a tidal salt wedge and disperses across the water surface where it meets denser saline estuary water; ii) the micro-particles sink out of the surface layer at the tip of the salt wedge in a sharp, readily observable boundary, due to flocculation effects. At this boundary or ecotone, the continuous presence of a “feeding prism” which contains very large numbers of at least three species of marine fish fry <20 mm total length, particularly in warmer months, was observed. The fry remain only within this creek area and feed on the ad-libitum supply of outwelling wetland micro-food particles while swimming in near oceanic condition water below the salt wedge; iii) the seston material varies with season; in warmer months it is principally a mixture of purple and green bacteria coated micro-particles and in cooler months detritus predominates; iv) the location of the halocline is dynamic and is related to the morphology of the creek and tide; and, v) the creek entrance also contains a deeper area in which small numbers of large apparently gravid fish were regularly observed. The fish fry aggregations are mapped in relation to the halocline in space and time during summer and winter seasons and linked to tidal sea-level and the morphology of the creek. The authors suggest the “feeding prism” ecotone is an important link between wetland process functions and marine fish recruitment for at least three commercially and recreationally important coastal fish species and perhaps others. It is this ecotone that needs to be considered as a focus of management measures and environmental impact assessment associated with adjoining developments and landscape modifications that may affect coastal processes in the vicinity of the creek. For example, the sand-dune syst","PeriodicalId":129808,"journal":{"name":"OCEANS'10 IEEE SYDNEY","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115469877","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 : 2010-05-24DOI: 10.1109/OCEANSSYD.2010.5603958
L. Freitag, K. Ball, P. Koski, Sandipa Singh, E. Gallimore
A prototype system for connecting remote instruments to a cabled observatory is described. The system consists of base-station modems and a data acquisition system attached to the MBARI MARS observatory in 900 m water off Monterey, California, plus remote modems used for link testing. The objective of the system is to provide a drop-in capability to connect sensors on the sea-floor or on sub-sea moorings to a cabled node that would otherwise require an ROV to make a hard-wired connection. While ROV installations of sensor-to-node cables are practical for many instruments, the acoustic connection is a way of lowering the barrier to general access of cabled nodes.
{"title":"Acoustic communications for deep-ocean observatories: Results of initial testing at the MBARI MARS node","authors":"L. Freitag, K. Ball, P. Koski, Sandipa Singh, E. Gallimore","doi":"10.1109/OCEANSSYD.2010.5603958","DOIUrl":"https://doi.org/10.1109/OCEANSSYD.2010.5603958","url":null,"abstract":"A prototype system for connecting remote instruments to a cabled observatory is described. The system consists of base-station modems and a data acquisition system attached to the MBARI MARS observatory in 900 m water off Monterey, California, plus remote modems used for link testing. The objective of the system is to provide a drop-in capability to connect sensors on the sea-floor or on sub-sea moorings to a cabled node that would otherwise require an ROV to make a hard-wired connection. While ROV installations of sensor-to-node cables are practical for many instruments, the acoustic connection is a way of lowering the barrier to general access of cabled nodes.","PeriodicalId":129808,"journal":{"name":"OCEANS'10 IEEE SYDNEY","volume":"88 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123010595","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 : 2010-05-24DOI: 10.1109/OCEANSSYD.2010.5603584
J. Thredgold, M. Fewell, S. Lourey, H. Vu
This paper describes a study of the effect of networking active sonars on tracking performance in a scenario with explicit inclusion of false detections, using two false-detection models and detection-probability curves with two levels of tailing. We compare the tracking performance when sonars share detections (centralized tracking) with the performance when sonars share tracks (distributed tracking). Provided that the sonar layout and detection probabilities are such that multiple sonars have a reasonable probability of obtaining detections from a target, we show that centralized tracking decreases the time to confirm a track on a target and improves the continuity of the target track, but increases the false track rate. Results for other metrics are also presented.
{"title":"Performance assessment of sonar-system networks for anti-submarine warfare","authors":"J. Thredgold, M. Fewell, S. Lourey, H. Vu","doi":"10.1109/OCEANSSYD.2010.5603584","DOIUrl":"https://doi.org/10.1109/OCEANSSYD.2010.5603584","url":null,"abstract":"This paper describes a study of the effect of networking active sonars on tracking performance in a scenario with explicit inclusion of false detections, using two false-detection models and detection-probability curves with two levels of tailing. We compare the tracking performance when sonars share detections (centralized tracking) with the performance when sonars share tracks (distributed tracking). Provided that the sonar layout and detection probabilities are such that multiple sonars have a reasonable probability of obtaining detections from a target, we show that centralized tracking decreases the time to confirm a track on a target and improves the continuity of the target track, but increases the false track rate. Results for other metrics are also presented.","PeriodicalId":129808,"journal":{"name":"OCEANS'10 IEEE SYDNEY","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123546664","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 : 2010-05-24DOI: 10.1109/OCEANSSYD.2010.5603966
K. Lo, B. Ferguson
Acoustic sensors deployed on the sea floor can be localized using a broadband sound source travelling along a linear trajectory at a constant velocity and a constant depth below the sea surface. The absolute positions (X- and Y-coordinates) of the sensors are estimated in two steps, assuming that the XY-plane coincides with the (flat) sea surface. First, a local Cartesian x-y coordinate system is set up in such a way that, when the sensors and the moving source are projected onto the local xy-plane, its origin coincides with the projection of one of the sensors (called the reference sensor) and the x-axis is parallel to the projection of the source's linear trajectory which intersects the positive y-axis. The projection of the source trajectory onto the xy-plane is described by three motion parameters: the source speed together with the time and horizontal range at which the source is at the closest point of approach (CPA) to the reference sensor. The relative positions (x- and y-coordinates) of all other sensors, along with the three motion parameters, are estimated by measuring the temporal variation of the differential time-of-arrival (DTOA) of the signal emitted by the moving source at each pair of sensors and then minimizing the sum of the squared deviations of the noisy DTOA estimates from their predicted values over a sufficiently long period of time for all pairs of sensors. This relative position estimation assumes a priori knowledge of the source depth, the sensor depths and the side (either left or right) on which the source transits past the reference sensor. In the second step, the relative position estimate of each sensor is converted into an absolute position estimate by rotating the x- and y-axes by an angle equal to the source bearing at CPA, followed by a translational displacement determined by the absolute position of the reference sensor. The source bearing at CPA can be estimated if either the direction of travel of the source or the absolute position of another sensor is known. It can also be derived together with the absolute position of the reference sensor if the absolute position of the moving source is known as a function of time (e.g. from a GPS receiver attached to the source). The proposed sensor localization method is applied to real acoustic data recorded in a shallow water experiment where a small vessel travelled at a constant speed (at zero depth) past a wide-aperture linear horizontal array of eight hydrophones mounted 1 m above the sea bed. Assuming that the absolute positions of two of the sensors are known, the effectiveness of the method is verified by comparing the estimated absolute positions of the other six sensors with their nominal values.
{"title":"Underwater acoustic sensor localization using a broadband sound source in uniform linear motion","authors":"K. Lo, B. Ferguson","doi":"10.1109/OCEANSSYD.2010.5603966","DOIUrl":"https://doi.org/10.1109/OCEANSSYD.2010.5603966","url":null,"abstract":"Acoustic sensors deployed on the sea floor can be localized using a broadband sound source travelling along a linear trajectory at a constant velocity and a constant depth below the sea surface. The absolute positions (X- and Y-coordinates) of the sensors are estimated in two steps, assuming that the XY-plane coincides with the (flat) sea surface. First, a local Cartesian x-y coordinate system is set up in such a way that, when the sensors and the moving source are projected onto the local xy-plane, its origin coincides with the projection of one of the sensors (called the reference sensor) and the x-axis is parallel to the projection of the source's linear trajectory which intersects the positive y-axis. The projection of the source trajectory onto the xy-plane is described by three motion parameters: the source speed together with the time and horizontal range at which the source is at the closest point of approach (CPA) to the reference sensor. The relative positions (x- and y-coordinates) of all other sensors, along with the three motion parameters, are estimated by measuring the temporal variation of the differential time-of-arrival (DTOA) of the signal emitted by the moving source at each pair of sensors and then minimizing the sum of the squared deviations of the noisy DTOA estimates from their predicted values over a sufficiently long period of time for all pairs of sensors. This relative position estimation assumes a priori knowledge of the source depth, the sensor depths and the side (either left or right) on which the source transits past the reference sensor. In the second step, the relative position estimate of each sensor is converted into an absolute position estimate by rotating the x- and y-axes by an angle equal to the source bearing at CPA, followed by a translational displacement determined by the absolute position of the reference sensor. The source bearing at CPA can be estimated if either the direction of travel of the source or the absolute position of another sensor is known. It can also be derived together with the absolute position of the reference sensor if the absolute position of the moving source is known as a function of time (e.g. from a GPS receiver attached to the source). The proposed sensor localization method is applied to real acoustic data recorded in a shallow water experiment where a small vessel travelled at a constant speed (at zero depth) past a wide-aperture linear horizontal array of eight hydrophones mounted 1 m above the sea bed. Assuming that the absolute positions of two of the sensors are known, the effectiveness of the method is verified by comparing the estimated absolute positions of the other six sensors with their nominal values.","PeriodicalId":129808,"journal":{"name":"OCEANS'10 IEEE SYDNEY","volume":"48 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122080950","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 : 2010-05-24DOI: 10.1109/OCEANSSYD.2010.5603896
Arjuna Balasuriya, S. Petillo, H. Schmidt, M. Benjamin
This paper discusses the autonomy framework proposed for the mobile instruments such as Autonomous Underwater Vehicles (AUVs) and gliders. Paper focuses on the challenges faced by these clusters of mobile platform in executive tasks such as adaptive sampling in the hostile underwater environment. Collaborations between these mobile instruments are essential to capture the environmental changes and track them for time-series analysis. This paper looks into the challenges imposed by the underwater communication infrastructure and presents the nested autonomy architecture as a solution to overcome these challenges. The autonomy architecture is separated from the low-level control architecture of these instruments, which is called the ‘backseat driver’. The back-seat driver paradigm is implemented on the Mission Oriented Object Suite (MOOS) developed at MIT. The autonomy is achieved by generating multiple behaviors (multiple objective functions) linked to the internal state of the platform as well as the environment. Optimization engine called the MOOS-IvP is used to pick the best action for the given instance based on the mission at hand. At sea operational scenarios and results are presented to demonstrate the proposed autonomy architecture for Ocean Observatory Initiative (OOI).
{"title":"Behavior-based planning and prosecution architecture for Autonomous Underwater Vehicles in Ocean Observatories","authors":"Arjuna Balasuriya, S. Petillo, H. Schmidt, M. Benjamin","doi":"10.1109/OCEANSSYD.2010.5603896","DOIUrl":"https://doi.org/10.1109/OCEANSSYD.2010.5603896","url":null,"abstract":"This paper discusses the autonomy framework proposed for the mobile instruments such as Autonomous Underwater Vehicles (AUVs) and gliders. Paper focuses on the challenges faced by these clusters of mobile platform in executive tasks such as adaptive sampling in the hostile underwater environment. Collaborations between these mobile instruments are essential to capture the environmental changes and track them for time-series analysis. This paper looks into the challenges imposed by the underwater communication infrastructure and presents the nested autonomy architecture as a solution to overcome these challenges. The autonomy architecture is separated from the low-level control architecture of these instruments, which is called the ‘backseat driver’. The back-seat driver paradigm is implemented on the Mission Oriented Object Suite (MOOS) developed at MIT. The autonomy is achieved by generating multiple behaviors (multiple objective functions) linked to the internal state of the platform as well as the environment. Optimization engine called the MOOS-IvP is used to pick the best action for the given instance based on the mission at hand. At sea operational scenarios and results are presented to demonstrate the proposed autonomy architecture for Ocean Observatory Initiative (OOI).","PeriodicalId":129808,"journal":{"name":"OCEANS'10 IEEE SYDNEY","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121572785","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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：