{"title":"Integrated approach to maximise deepwater asset value with subsea fluid samplings","authors":"N. Abili, F. Kara","doi":"10.3723/UT.32.245","DOIUrl":"https://doi.org/10.3723/UT.32.245","url":null,"abstract":"","PeriodicalId":44271,"journal":{"name":"UNDERWATER TECHNOLOGY","volume":"70 1","pages":"245-253"},"PeriodicalIF":0.4,"publicationDate":"2015-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74688713","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}
R. Venkatesan, V. R. Shamji, N. Vedachalam, G. Latha, R. Sundar, Simi Mathew, R. R. Rao, M. Muthiah, P. Prasad, M. Atmanand
{"title":"Assessment of the reliability of the Indian tsunami buoy system","authors":"R. Venkatesan, V. R. Shamji, N. Vedachalam, G. Latha, R. Sundar, Simi Mathew, R. R. Rao, M. Muthiah, P. Prasad, M. Atmanand","doi":"10.3723/UT.32.255","DOIUrl":"https://doi.org/10.3723/UT.32.255","url":null,"abstract":"","PeriodicalId":44271,"journal":{"name":"UNDERWATER TECHNOLOGY","volume":"82 1","pages":"255-270"},"PeriodicalIF":0.4,"publicationDate":"2015-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89846976","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}
C. D. Makavita, H. Nguyen, D. Ranmuthugala, S. Jayasinghe
The control of unmanned underwater vehicles (UUVs) is challenging due to the non-linear and time-varying nature of the hydrodynamic forces from the surrounding fluid. In addition, the presence of external disturbances makes the control even more difficult. Model reference adaptive control (MRAC) is an adaptive control technique that performs well in such situations, while the improved composite/combined model reference adaptive control (CMRAC) is capable of better transient performance. However, the latter is yet to be used in UUV controls. Thus, this paper tests the suitability of CMRAC in UUV applications using validated simulation models and compares its performance against the standard MRAC. Several test scenarios have been considered including initial operation, external disturbance and thruster failure. Simulation results show that CMRAC offers better tracking, faster disturbance rejection and quick recovery from thruster failure compared to MRAC. In addition, CMRAC is more robust against parameter uncertainties and thus the control signal shows fewer oscillations, which in turn reduces the probability of actuator damage.
{"title":"Composite model reference adaptive control for an unmanned underwater vehicle","authors":"C. D. Makavita, H. Nguyen, D. Ranmuthugala, S. Jayasinghe","doi":"10.3723/ut.33.081","DOIUrl":"https://doi.org/10.3723/ut.33.081","url":null,"abstract":"The control of unmanned underwater vehicles (UUVs) is challenging due to the non-linear and time-varying nature of the hydrodynamic forces from the surrounding fluid. In addition, the presence of external disturbances makes the control even more difficult. Model reference adaptive control (MRAC) is an adaptive control technique that performs well in such situations, while the improved composite/combined model reference adaptive control (CMRAC) is capable of better transient performance. However, the latter is yet to be used in UUV controls. Thus, this paper tests the suitability of CMRAC in UUV applications using validated simulation models and compares its performance against the standard MRAC. Several test scenarios have been considered including initial operation, external disturbance and thruster failure. Simulation results show that CMRAC offers better tracking, faster disturbance rejection and quick recovery from thruster failure compared to MRAC. In addition, CMRAC is more robust against parameter uncertainties and thus the control signal shows fewer oscillations, which in turn reduces the probability of actuator damage.","PeriodicalId":44271,"journal":{"name":"UNDERWATER TECHNOLOGY","volume":"20 1","pages":"81-93"},"PeriodicalIF":0.4,"publicationDate":"2015-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73365393","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}
T. Szyrowski, A. Motwani, Sanjay K. Sharma, R. Sutton, G. Kennedy
{"title":"Subsea cable tracking by an unmanned surface vehicle","authors":"T. Szyrowski, A. Motwani, Sanjay K. Sharma, R. Sutton, G. Kennedy","doi":"10.3723/UT.32.217","DOIUrl":"https://doi.org/10.3723/UT.32.217","url":null,"abstract":"","PeriodicalId":44271,"journal":{"name":"UNDERWATER TECHNOLOGY","volume":"83 1","pages":"217-229"},"PeriodicalIF":0.4,"publicationDate":"2015-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83814535","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}
The average shape of large waves in the open ocean made up of linear waves with random phase is given by ‘NewWave’ defined by the auto-correlation function of the wave spectrum. In this note we confirm this result for realistic directionally spread sea-states but show that there is a considerable variation in shape of rogue waves. Practical implications are discussed.
{"title":"A note on the variation in shape of linear rogue waves in the ocean","authors":"T. Adcock, S. Draper","doi":"10.3723/UT.33.075","DOIUrl":"https://doi.org/10.3723/UT.33.075","url":null,"abstract":"The average shape of large waves in the open ocean made up of linear waves with random phase is given by ‘NewWave’ defined by the auto-correlation function of the wave spectrum. In this note we confirm this result for realistic directionally spread sea-states but show that there is a considerable variation in shape of rogue waves. Practical implications are discussed.","PeriodicalId":44271,"journal":{"name":"UNDERWATER TECHNOLOGY","volume":"94 1","pages":"75-80"},"PeriodicalIF":0.4,"publicationDate":"2015-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83910984","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}
The use of unmanned underwater vehicles (UUVs) to enhance the military capabilities of submarines and to reduce their operational risk is being considered by navies around the world. However, a major difficulty with the operations of UUVs is their recovery back to the submarine at the end of the mission. Various schemes have been proposed by a number of organisations working in this field; however, they all have major drawbacks. A simple concept is proposed based on a warp from the submarine to a low aspect ratio wing, similar to an otter board used by fishing trawlers. This approach allows the submarine to recover the UUV by slowly overtaking it. This is done at a sufficiently large transverse distance between the vessels where hydrodynamic interaction between the two is minimal, with the submarine travelling at a speed at which it can be safely controlled.
{"title":"A simplified concept for recovering a UUV to a submarine","authors":"M. Renilson","doi":"10.3723/UT.32.193","DOIUrl":"https://doi.org/10.3723/UT.32.193","url":null,"abstract":"The use of unmanned underwater vehicles (UUVs) to enhance the military capabilities of submarines and to reduce their operational risk is being considered by navies around the world. However, a major difficulty with the operations of UUVs is their recovery back to the submarine at the end of the mission. Various schemes have been proposed by a number of organisations working in this field; however, they all have major drawbacks. \u0000 \u0000A simple concept is proposed based on a warp from the submarine to a low aspect ratio wing, similar to an otter board used by fishing trawlers. This approach allows the submarine to recover the UUV by slowly overtaking it. This is done at a sufficiently large transverse distance between the vessels where hydrodynamic interaction between the two is minimal, with the submarine travelling at a speed at which it can be safely controlled.","PeriodicalId":44271,"journal":{"name":"UNDERWATER TECHNOLOGY","volume":"31 1","pages":"193-197"},"PeriodicalIF":0.4,"publicationDate":"2014-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84720109","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}
A. Schuster, P. Buzzacott, S. Reif, B. Kuch, Amir Gerges, E. Azzopardi, M. Sayer, A. Sieber
{"title":"Function selection among popular dive computer models: A review and proposed improvements","authors":"A. Schuster, P. Buzzacott, S. Reif, B. Kuch, Amir Gerges, E. Azzopardi, M. Sayer, A. Sieber","doi":"10.3723/UT.32.159","DOIUrl":"https://doi.org/10.3723/UT.32.159","url":null,"abstract":"","PeriodicalId":44271,"journal":{"name":"UNDERWATER TECHNOLOGY","volume":"22 1","pages":"159-165"},"PeriodicalIF":0.4,"publicationDate":"2014-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85695691","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}
Abstract Optical wireless communications (OWC) are being consid-ered for use under water because sea water exhibits a win-dow of reduced absorption in the visible spectrum, particularly between 400–550nm. Recent technology has demonstrated the ability to support mid-range links (<200m) and at high bandwidths (<1Gbps) in clear oceans. The present paper outlines the governing transmission characteristics and reviews current experimental research in underwater OWC, highlighting the importance of the local chlorophyll concen -tration, particulate concentration and the resultant wave-length selection. Ideal wavelengths are found to be from 430nm, which represents a deep blue colour, to beyond 550nm in areas where the chlorophyll concentration is high. Keywords: underwater communications, visible-light com-munications, ocean optics 1. Introduction Acoustic systems have enjoyed great success under water owing to their ability to communicate over many kilometres, despite low bandwidth capacity (Chitre et al., 2008). However, in recent times, some underwater applications such as the new generation of autonomous underwater vehicles (AUVs) have called for a complementary technology, capable of high bandwidths over short- to mid-range distances. Optical wireless communications are being consid-ered as a possible solution to this. The use of visible light was first suggested as a viable technology under water over 30 years ago (Wiener and Karp, 1980) because the electromag-netic absorption of sea water presents a window of reduced attenuation in the visible spectrum, particu -larly within the blue-green region. However, it was not until the recent advances in terrestrial visible-light technology that research into underwater optical wireless communications (OWC) began to gather significant momentum. Applying OWC to the underwater environment is not a trivial matter. Not only does light in sea water undergo higher channel attenuation compared to that in clear air, but also the optical properties of the medium itself vary significantly (Stramski et al., 2001) and there are more sources of link disruption. Natural oceans are rich in dissolved and particulate matter, leading to a wide range of circumstances with which an underwater communication system must cope. However, biochemical and optical prop-erties are linked, which is evident when comparing the colour of open ocean with coastal waters. This implies that optical constants can be deduced from the local seawater composition. The present paper introduces the factors that affect light propagation in the ocean and how they might impact on the configuration of underwater OWC sys-tems. It concludes by reviewing experimental achieve-ments in this subject and discussing how these projects are paving a path towards commercialisation.
由于海水在可见光谱中表现出一个吸收减少的窗口，特别是在400-550nm之间，因此人们正在考虑在水下使用光无线通信(OWC)。最近的技术已经证明了在清澈的海洋中支持中距离链路(<200米)和高带宽(<1Gbps)的能力。本文概述了水下光波导的控制传输特性，综述了目前的实验研究，强调了局部叶绿素浓度、颗粒浓度和由此产生的波长选择的重要性。理想的波长从430纳米(深蓝色)到550纳米(叶绿素浓度高的地区)。关键词:水下通信，可见光通信，海洋光学声学系统在水下取得了巨大的成功，尽管带宽容量很低，但由于它们能够在许多公里内进行通信(Chitre等人，2008年)。然而，近年来，一些水下应用，如新一代自主水下航行器(auv)，需要一种能够在中短距离上实现高带宽的互补技术。人们正在考虑将无线光通信作为一种可能的解决方案。30多年前，可见光的使用首次被认为是一种可行的水下技术(Wiener和Karp, 1980)，因为海水的电磁吸收在可见光谱中呈现出衰减减少的窗口，特别是在蓝绿色区域内。然而，直到近年来陆地可见光技术的进步，水下光学无线通信(OWC)的研究才开始有了长足的发展。将OWC应用于水下环境并不是一件小事。与清澈空气中的光相比，海水中的光不仅有更高的信道衰减，而且介质本身的光学特性也有很大的变化(Stramski et al.， 2001)，并且存在更多的链路中断源。天然海洋中含有丰富的溶解物质和微粒物质，这导致水下通信系统必须应对各种各样的情况。然而，生物化学和光学性质是联系在一起的，当比较开放海洋和沿海水域的颜色时，这一点很明显。这意味着光学常数可以由当地海水组成推断出来。本文介绍了影响光在海洋中传播的因素，以及这些因素如何影响水下光控系统的配置。最后回顾了这方面的实验成果，并讨论了这些项目如何为商业化铺平道路。
{"title":"Recent advances in underwater optical wireless communications","authors":"Laura J. Johnson, F. Jasman, R. Green, M. Leeson","doi":"10.3723/UT.32.167","DOIUrl":"https://doi.org/10.3723/UT.32.167","url":null,"abstract":"Abstract Optical wireless communications (OWC) are being consid-ered for use under water because sea water exhibits a win-dow of reduced absorption in the visible spectrum, particularly between 400–550nm. Recent technology has demonstrated the ability to support mid-range links (<200m) and at high bandwidths (<1Gbps) in clear oceans. The present paper outlines the governing transmission characteristics and reviews current experimental research in underwater OWC, highlighting the importance of the local chlorophyll concen -tration, particulate concentration and the resultant wave-length selection. Ideal wavelengths are found to be from 430nm, which represents a deep blue colour, to beyond 550nm in areas where the chlorophyll concentration is high. Keywords: underwater communications, visible-light com-munications, ocean optics 1. Introduction Acoustic systems have enjoyed great success under water owing to their ability to communicate over many kilometres, despite low bandwidth capacity (Chitre et al., 2008). However, in recent times, some underwater applications such as the new generation of autonomous underwater vehicles (AUVs) have called for a complementary technology, capable of high bandwidths over short- to mid-range distances. Optical wireless communications are being consid-ered as a possible solution to this. The use of visible light was first suggested as a viable technology under water over 30 years ago (Wiener and Karp, 1980) because the electromag-netic absorption of sea water presents a window of reduced attenuation in the visible spectrum, particu -larly within the blue-green region. However, it was not until the recent advances in terrestrial visible-light technology that research into underwater optical wireless communications (OWC) began to gather significant momentum. Applying OWC to the underwater environment is not a trivial matter. Not only does light in sea water undergo higher channel attenuation compared to that in clear air, but also the optical properties of the medium itself vary significantly (Stramski et al., 2001) and there are more sources of link disruption. Natural oceans are rich in dissolved and particulate matter, leading to a wide range of circumstances with which an underwater communication system must cope. However, biochemical and optical prop-erties are linked, which is evident when comparing the colour of open ocean with coastal waters. This implies that optical constants can be deduced from the local seawater composition. The present paper introduces the factors that affect light propagation in the ocean and how they might impact on the configuration of underwater OWC sys-tems. It concludes by reviewing experimental achieve-ments in this subject and discussing how these projects are paving a path towards commercialisation.","PeriodicalId":44271,"journal":{"name":"UNDERWATER TECHNOLOGY","volume":"44 1","pages":"167-175"},"PeriodicalIF":0.4,"publicationDate":"2014-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84336655","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：