JabRef References output

Author	Title	Year	Journal/Proceedings	Reftype
Barker, A., Sayed, M. & Timco, G.	Numerical Simulations of Broken Ice Interaction with Structures [Abstract] [BibTeX]	2000		techreport
Abstract: The interaction of moving broken ice with a structure is an important problem in ice mechanics. Ice-induced loads and pile-ups can result due to this type of interaction, for example, on a bridge pier during spring break-up or on a vessel stationkeeping in pack ice conditions. Numerical techniques can be developed and applied to investigate this type of problem. In this report, a numerical model of ice interaction with both slender and wide structures in varying ice conditions is presented. The model is based on a Particle-In-Cell (PIC) approach, combined with a viscous plastic ice rheology. The plastic yield follows a Mohr-Coulomb criterion. The Zhang-Hibler (1997) numerical scheme is used to solve the momentum equations. The model is used to examine the role of ice thickness, ice properties and velocity on the resulting forces on two different structures. The results show good agreement with the field measurements.
BibTeX: @techreport{Bar00, author = {Anne Barker and Mohamed Sayed and Garry Timco}, title = {Numerical Simulations of Broken Ice Interaction with Structures}, year = {2000} }
Croasdale, K.R., Bruce, J.R. & Liferov, P.	Sea Ice Loads Due To Managed Ice [Abstract] [BibTeX]	2009	20th International Conference on Port and Ocean Engineering under Arctic Conditions	inproceedings
Abstract: Managed ice is the term given to ice that has been broken ahead of a platform or anchored vessel in order to reduce the ice loads or other effects of ice interaction such as rubble build up. Ice features which would create loads greater than the mooring loads of the stationary platform or vessel are broken into small pieces to reduce the ice loads. This is usually done with several icebreakers; one or more breaking ice in the far field and one or more breaking ice in the near field. Although there is some experience on how much management is required to reduce mooring loads, the present methods for managed ice loads rely on expert judgment and are empirical. In this paper, simple concepts for managed ice loads have been developed and quantified. Ice load concepts and equations are presented based on piece size of the managed ice, ice and rubble thickness, and whether there is any ice pressure in the ice field. These concepts can be used to specify piece sizes to be achieved and operational tactics in various ice management scenarios for a given floating platform and mooring system. Comparisons are made with the Kulluk experience and loads in the Canadian Beaufort Sea in order to help verify the equations and calibrate the inputs.
BibTeX: @inproceedings{Croasdale2009, author = {K. R. Croasdale and J. R. Bruce and P. Liferov}, title = {Sea Ice Loads Due To Managed Ice}, booktitle = {20th International Conference on Port and Ocean Engineering under Arctic Conditions}, year = {2009} }
Delius, A. & Kuehnlein, W.L.	Multi-functional advanced research vessel - Oil & gas exploration - Ice loading monitoring - Neumayer Station III inaugurated [BibTeX]	2009	(2)Ship & Port	conference
BibTeX: @conference{del09, author = {Albrecht Delius and Walter L. Kuehnlein}, title = {Multi-functional advanced research vessel - Oil & gas exploration - Ice loading monitoring - Neumayer Station III inaugurated}, booktitle = {Ship & Port}, year = {2009}, number = {2} }
Dunderdale, P. & Wright, B.	Pack ice management on the Southern Grand Banks offshore Newfoundland, Canada [Abstract] [BibTeX]	2005	(PERD/CHC Report: 20-76)	techreport
Abstract: Pack ice management is a matter of considerable importance, particularly for floating development systems working on the Grand Banks, which lies several hundred kilometers southeast of Newfoundland on Canada�s East Coast. Although pack ice is not experienced annually across the more southerly parts of this area, where the Terra Nova and Hibernia oil fields are located, it is of real concern when it does occur and is therefore a significant operational issue. Additionally, the likelihood of more frequent and persistent pack ice occurrences that can constrain floating system operations will increase as activities on the Grand Banks move further towards the north and east, for example, at the Whiterose location. Future exploration and development activities that are now being considered for more distant areas like the Orphan Basin and Flemish Cap will be even more susceptible to pack ice. This report presents the results of a brief scoping study regarding pack ice management considerations on the Grand Banks, and on suitable ice management vessels in particular. The work was carried out as a PERD study for the National Research Council of Canada, by Noble Denton Canada Ltd., with input from B. Wright & Associates Ltd.
BibTeX: @techreport{Dunderdale2005, author = {Peter Dunderdale and Brian Wright}, title = {Pack ice management on the Southern Grand Banks offshore Newfoundland, Canada}, year = {2005}, number = {PERD/CHC Report: 20-76} }
Eik, K.J.	Ice Management in Arctic Offshore Operations and Field Developments [Abstract] [BibTeX]	2010	School: NTNU	phdthesis
Abstract: The subject ice management has been studied with the main objective to deduce a methodology that incorporates the effect of ice management on the structural reliability of offshore installations. This was done by first studying Arctic projects in the past and summarizes the learning�s. All available reports were unanimous and highlighted ice management as a key for the successes in the projects. Based on the reported experiences, an unambiguous definition of ice management was made: �Ice management is the sum of all activities where the objective is to reduce or avoid actions from any kind of ice features� Despite the number of similarities between sea ice management and iceberg management, it was decided to study each of the fields individually. The motivation for doing so was that iceberg management in general focus on reducing the frequency of impacts between icebergs and installations while sea ice management generally focus on reducing the sizes in the ice floe distributions and thereby reduces the severity of the ice actions. One methodology for including iceberg management and one for including sea ice management in the offshore installation design process has been proposed. In order to develop the models for ice management efficiency a number of studies of the various elements were conducted. Individual papers regarding subsurface ice intelligence, iceberg drift modelling, iceberg deterioration, iceberg deflection in ice and ice load variability has been published and are included in this thesis. Each of these papers is of importance for the proposed models for ice management efficiency. The possibility to disconnect an installation and escape the site has been considered both in the methodologies for iceberg management and sea ice management. When considering the number and magnitude of uncertainties both with respect to load calculations from icebergs and sea ice, it is concluded that disconnection capabilities should be considered in all Arctic projects. It was shown that icebreakers not necessarily are sufficient to reduce extreme or abnormal loads on a structure. However, there may still be a number of reasons for why icebreakers also should be considered in Arctic projects. The methodologies presented in this work provide adequate tools for evaluating the effect of various icebreaker fleets and iceberg management systems. However, the approaches rely on a number of tools and formulations with inherent weaknesses and advantages. The weaknesses are discussed and recommendations for further work in order to improve the models have been proposed.
BibTeX: @phdthesis{Eik2010, author = {Kenneth J. Eik}, title = {Ice Management in Arctic Offshore Operations and Field Developments}, school = {NTNU}, year = {2010} }
Evensen, G.	The Ensemble Kalman Filter: theoretical formulation and practical implementation [Abstract] [BibTeX]	2003	Ocean Dynamics Vol. 53(4), pp. 343-367	article
Abstract: The purpose of this paper is to provide a comprehensive presentation and interpretation of the Ensemble Kalman Filter (EnKF) and its numerical implementation. The EnKF has a large user group, and numerous publications have discussed applications and theoretical aspects of it. This paper reviews the important results from these studies and also presents new ideas and alternative interpretations which further explain the success of the EnKF. In addition to pro- viding the theoretical framework needed for using the EnKF, there is also a focus on the algorithmic for- mulation and optimal numerical implementation. A program listing is given for some of the key subrou- tines. The paper also touches upon specific issues such as the use of nonlinear measurements, in situ profiles of temperature and salinity, and data which are available with high frequency in time. An ensem- ble based optimal interpolation (EnOI) scheme is presented as a cost-effective approach which may serve as an alternative to the EnKF in some applications. A fairly extensive discussion is devoted to the use of time correlated model errors and the estimation of model bias.
BibTeX: @article{Evensen2003, author = {Evensen, G.}, title = {The Ensemble Kalman Filter: theoretical formulation and practical implementation}, journal = {Ocean Dynamics}, year = {2003}, volume = {53}, number = {4}, pages = {343--367} }
Fossen, T.I. & Str, J.P.	Nonlinear passive weather optimal positioning control (WOPC) system for ships and rigs: experimental results [Abstract] [BibTeX]	2001	Automatica Vol. 37, pp. 701-715	article
Abstract: Nonlinear weather optimal control of ships exposed to environmental disturbances is discussed. Emphasis is placed on weather vaning, that is the ship should be orientated such that the moment in yaw due to mean current, wind and wave forces is zero and at the same time maintain a "xed position and heading. The main problem in doing this is that the environmental forces acting on the ship are impossible to measure with su$cient accuracy. A new concept for weather optimal position control (WOPC) based on nonlinear control theory is invented and presented for the "rst time in this paper. Experiments with a model ship are used to document the performance of the controller. The proposed controller and the concept of WOPC were patented by the authors in cooperation with ABB Industri AS, Oslo in December 1998 under patent no. NO308.334. _ 2001 Elsevier Science Ltd. All rights reserved.
BibTeX: @article{Fossen2001, author = {Thor I. Fossen and Jann Peter Str}, title = {Nonlinear passive weather optimal positioning control (WOPC) system for ships and rigs: experimental results}, journal = {Automatica}, year = {2001}, volume = {37}, pages = {701-715} }
Frederkin, R.	Ice Loading on a Ship in Discontinuous Ice [Abstract] [BibTeX]	2010	20th International Offshore and Polar Engineering Conference	inproceedings
Abstract: Field data from operations of the CCGS Louis S. St-Laurent during a period of icebreaking escort operations in the Gulf of St. Lawrence in March 1985 were analysed for ice loads in discontinuous ice. The bow of the ship was strain-gauged to measure ice impact loads. Forces, operational conditions (ship speed and power), and ice conditions (ice concentration, ice thickness and floe size) were recorded. From these data, time series of measured loads were used to obtain the maximum force of each measured impact, as well as the impulse associated with it. The ship speed and a best estimate of ice concentration, floe size,and ice thickness were associated with each impact. Ice impact forces The were related to floe mass, ice concentration and ship speed. duration of an ice impact was directly related to the magnitude of the maximum force.
BibTeX: @inproceedings{Frederkin2010, author = {R. Frederkin}, title = {Ice Loading on a Ship in Discontinuous Ice}, booktitle = {20th International Offshore and Polar Engineering Conference}, year = {2010} }
Gignac, C., Gauthier, Y., B�dard, J.S., Bernier, M. & Clausi, D.A.	High resolution radarsat-2 sar data for sea-ice classification in the neighborhood of Nunavik's marine infrastructures [Abstract] [BibTeX]	2011	International Conference on Port and Ocean Engineering under Arctic Conditions	inproceedings
Abstract: Marine infrastructures are a key component for arctic communities. During the past decades, climate change effects have been observed throughout the Arctic and may be linked with marine infrastructure physical deterioration. Changes in the wind and water regimes and in the ice conditions are major factors explaining this observed phenomenon. Satellite radar images are often used to monitor sea ice conditions on a large scale. This study focuses on the use of high resolution radar images to assess the ice conditions during the freeze-up and break-up periods of 2009-2011 near the marine infrastructures of villages in Nunavik: Quaqtaq and Umiujaq. The data used in this study are RADARSAT-2 fine (9m) and ultra-fine (3m) images. They were processed using the MIRGS algorithm (Multivariate Iterative Region Growing using Semantics) developed in the Department of Systems Engineering at the University of Waterloo. Using MIRGS, sea ice maps are generated for the immediate neighbourhood of the marine infrastructures. Validation is made using air photos and ground photos taken at the infrastructures. Spatial statistics such as first ice appearance and different concentration thresholds are calculated for various buffers (0.1 to 10 km) around the infrastructure using spatial analysis methods in ArcGIS. The study is part of a larger project assessing the vulnerability of Nunavik�s marine infrastructures to climate change, led by Transport Quebec and the Ouranos Consortium. The ice maps and statistics will be used to document ice behaviour near the infrastructures and to validate a 3D oceanic sea ice model.
BibTeX: @inproceedings{Gignac2011, author = {C. Gignac and Y. Gauthier and J. S. B�dard and M. Bernier and D. A. Clausi}, title = {High resolution radarsat-2 sar data for sea-ice classification in the neighborhood of Nunavik's marine infrastructures}, booktitle = {International Conference on Port and Ocean Engineering under Arctic Conditions}, year = {2011} }
Government of Canada, E.C.	MANICE: Manual of Standard Procedures for Observing and Reporting Ice Conditions [Abstract] [BibTeX]	2005		manual
Abstract: MANICE is the Manual of Standard Procedures for Observing and Reporting Ice Conditions. MANICE is the authoritative document for observing all forms of ice: Sea Ice, Lake and River Ice, and Ice of Land Origin The most recent version of MANICE (date of revision: June 2005) contains the following sections: Introduction Table of Content Chapter 1: General Terminology Chapter 2: Ice observations Chapter 3: Observed Ice charts Chapter 4: Iceberg Messages Chapter 5: Ice Analysis Charts Chapter 6: Ice Thickness Measurements and Reports Conversion Table Key to Ice Symbols
BibTeX: @manual{manice05, author = {Government of Canada, Environment Canada}, title = {MANICE: Manual of Standard Procedures for Observing and Reporting Ice Conditions}, year = {2005} }
Hamilton, J.M., Holub, C.J. & Blunt, J.	Simulation of ice management fleet operations using two decades of Beaufort sea ice drift and thickness time histories [Abstract] [BibTeX]	2011	Twenty-first International Offshore and Polar Engineering Conference, pp. 1100-1107	inproceedings
Abstract: Ice management using icebreakers to reduce floe size ahead of a stationary drilling vessel will be a key component of offshore Arctic exploration and development drilling. Selection of the management vessels and fleet deployment configuration is critical to insure the ability to (1) maintain the drilling vessel within the managed ice channel as ice drift direction continuously changes, and (2) produce sufficiently small floe sizes during periods of high ice drift velocity. This paper describes the key considerations for accomplishing the complex task of ice management and demonstrates a field-calibrated, simulation-based means for testing the efficacy of various tactics against actual measured Beaufort Sea ice drift and thickness time histories collected by the Fisheries and Oceans Canada since 1990. The results provide valuable insight into ice management fleet composition and fleet deployment; for instance, it is shown more efficient to use a racetrack versus circular icebreaker track to maintain an ice channel for the stationary drillship.
BibTeX: @inproceedings{Hamilton2011, author = {Jed M. Hamilton and Curtis J. Holub and Joshua Blunt}, title = {Simulation of ice management fleet operations using two decades of Beaufort sea ice drift and thickness time histories}, booktitle = {Twenty-first International Offshore and Polar Engineering Conference}, year = {2011}, pages = {1100-1107} }
Hansen, E.	A discrete element model to study marginal ice zone dynamics and the behaviour of vessels moored in broken ice [Abstract] [BibTeX]	1998	School: NTNU	phdthesis
Abstract: A numerical simulation model that simulates the behaviour of a vessel moored in broken ice has been used to compare results from numerical simulations with ice tank tests. In the simulations a tanker moored on an eight legged catenary mooring of the Submerged Turret Loading (STL) concept was towed through a broken ice field. The setup of this situation was as similar to the ice tank setup as possible. The results predicted by the model are in qualitative agreement with the experimental results, but the amplitudes tend to be overpredicted. The predicted frequency of oscillation in surge is slightly lower than what was measured. The deviations between predicted and measured results may in part be explained by the differences in model and ice tank setup, and in part by poor representation of various load limiting mechanisms. However, with the qualitative agreement achieved, and the differences between model and experimental setup in mind, it is reasonable to believe that the numerical model may yield realistic results in further full-scale simulations.
BibTeX: @phdthesis{Hansen1998, author = {E. Hansen}, title = {A discrete element model to study marginal ice zone dynamics and the behaviour of vessels moored in broken ice}, school = {NTNU}, year = {1998} }
Haugen, J., Imsland, L., Løset, S. & Skjetne, R.	Ice Observer System for Ice Management Operations [Abstract] [BibTeX]	2011	21st Int. Offshore (Ocean) and Polar Eng. Conf., pp. 1120-1127	inproceedings
Abstract: This article describes the structure of an ice observer system, which is in- tended to aid decisions regarding risk assessment of the ice environment, as well as control performance of dynamic positioning systems, in off- shore operations. An ice observer system collects, analyses and employs ice intelligence during operations in ice. Furthermore, Unmanned Aerial Vehicles (UAVs) are presented as a viable sensor platform for close and far field ice monitoring.
BibTeX: @inproceedings{Haugen2011, author = {Haugen, J. and Imsland, L. and Løset, S. and Skjetne, R.}, title = {Ice Observer System for Ice Management Operations}, booktitle = {21st Int. Offshore (Ocean) and Polar Eng. Conf.}, year = {2011}, pages = {1120-1127} }
Innocenti, G. & Paoletti, P.	Traveling waves propogation on networks of dynamical systems [Abstract] [BibTeX]	2011	International Federation of Automatic Control (IFAC)	inproceedings
Abstract: Conditions for traveling wave propagation in networks of dynamical systems are investigated by suitably defining a family of ordinary differential equations (ODEs) whose solutions approximate the wave itself with increasing degree of accuracy. A reduced order ODE is considered for computing reference solutions, which are then exploited to prove via implicit function theorem the existence of similar solutions in the original network. A numerical example is included to illustrate the effectiveness of the proposed approach.
BibTeX: @inproceedings{Innocebti2011, author = {Giacomo Innocenti and Paolo Paoletti}, title = {Traveling waves propogation on networks of dynamical systems}, booktitle = {International Federation of Automatic Control (IFAC)}, year = {2011} }
Ioannou, P.A. & Sun, J.	Robust Adaptive Control [Abstract] [BibTeX]	1996		book
Abstract: The most comprehensive guide in the area of adaptive control of continuous-time systems. Presents most of the existing techniques for designing and analyzing adaptive systems, in a tutorial manner. Covers models for dynamic systems, stability, on-line parameter estimation, parameter identifiers, model reference adaptive control, adaptive pole placement control, and robust adaptive laws. For engineers working in the areas of identification, neural networks, fuzzy logic, and controls.
BibTeX: @book{Ioannou1996, author = {Petros A. Ioannou and Jing Sun}, title = {Robust Adaptive Control}, publisher = {Prentice-Hall}, year = {1996} }
Jenssen, N.A., Muddesitti, S., Phillips, D. & Backstrom, K.	DP In Ice Conditions [Abstract] [BibTeX]	2009	Dynamic Positioning Conference	conference
Abstract: The paper discusses the topic of DP operations in arctic ice conditions. Different from open water DP, qualification of DP control in such environments is difficult since there are no well established methods for doing so. The paper shows that there is a need to make a DP control system more reactive to cope with the highly varying ice loads acting on a DP vessel. Assuming such a measure is taken DP operations should be feasible. However, it will require well planned and executed ice management.
BibTeX: @conference{jen09, author = {Nils Albert Jenssen and Suman Muddesitti and Doug Phillips and Klaus Backstrom}, title = {DP In Ice Conditions}, booktitle = {Dynamic Positioning Conference}, year = {2009} }
Ji, S., Li, H., Wang, A. & Yue, Q.	Digital image techniques of sea ice field observation in the Bohai sea [Abstract] [BibTeX]	2011	International Conference on Port and Ocean Engineering under Arctic Conditions	inproceedings
Abstract: In this study, digital image techniques are adopted to process the sea ice parameters based on the dynamic characteristics and distribution conditions of sea ice in the Bohai Sea. A precise algorithm and effective software system are developed to determine the ice thickness, ice velocity and ice concentration, respectively. In the winter of 2009-2010, the developed sea ice digital image collection and processing system was utilized to monitor the ice parameters in the JZ20-2 oil-gas field of the Liaodong Bay. It shows that the developed system has the advantages of convenient operation, high accuracy and reliability.
BibTeX: @inproceedings{Ji2011, author = {Shunying Ji and Hai Li and Anliang Wang and Qianjin Yue}, title = {Digital image techniques of sea ice field observation in the Bohai sea}, booktitle = {International Conference on Port and Ocean Engineering under Arctic Conditions}, year = {2011} }
J�rgensen, U. & Skjetne, R.	Autonomous Estimation of Drifting Ice Topography Using Continuous Steepest Descent Gradient Minimization [Abstract] [BibTeX]	2012	American Control Conference (submitted)	inproceedings
Abstract: In this paper we present an estimation design for a drifting two dimensional ice topography. Under the assumption that the topography can be accurately represented by a truncated Fourier series, and given a set of measurements distributed discretely along the topography, the steepest descent method is proposed to solve the problem. The chosen method allows different weighting on the various measurements and coefficients such that the weight on possible faulty measurements can be reduced, while important coefficients can be prioritized. In cases where measurements of the ice topography are available only periodically, an observer is proposed such that non-measured nodes can be dynamically updated. In both cases the effectiveness of the estimation algorithm are simulated in a constructed ideal scenario, as well as a scenario where a set of real ice measurements are taken from the underside of an ice sheet off the cost of Greenland.
BibTeX: @inproceedings{Joergensen2012, author = {J�rgensen, U. and Skjetne, R.}, title = {Autonomous Estimation of Drifting Ice Topography Using Continuous Steepest Descent Gradient Minimization}, booktitle = {American Control Conference (submitted)}, year = {2012} }
Keinonen, A., Wells, H., Dunderdale, P., Pilkington, R., Miller, G. & Brovin, A.	Dynamic Positioning Operation in Ice, Offshore Sakhalin, May - June 1999 [BibTeX]	2000	Proceedings of the Tenth (2000) International Offshore and Polar Engineering Conference, pp. 683-690	inproceedings
BibTeX: @inproceedings{kei00, author = {Arno Keinonen and Hal Wells and Peter Dunderdale and Roger Pilkington and Gordon Miller and Alexander Brovin}, title = {Dynamic Positioning Operation in Ice, Offshore Sakhalin, May - June 1999}, booktitle = {Proceedings of the Tenth (2000) International Offshore and Polar Engineering Conference}, year = {2000}, pages = {683-690} }
Kjerstad, Ø. & Breivik, M.	Weather Optimal Positioning Control for Marine Surface Vessels [Abstract] [BibTeX]	2010	IFAC CAMS	inproceedings
Abstract: This paper addresses the problem of energy-efficient dynamic positioning (DP) for marine surface vessels by means of a weather optimal control scheme. Fundamental geometric relations associated with a pendulum in a force field are utilized to obtain fuelefficient DP functionality. First, weather optimal heading control (WOHC) is achieved through the use of specific surge and yaw controllers which make a vessel behave like a force-field pendulum, employing a virtual suspension point and an associated pendulum length. This design is particularly suitable for sway-unactuated vessels. Second, an intuitive and geometricallymotivated update law is assigned to the virtual suspension point to facilitate weather optimal positioning control (WOPC), which enables a vessel to be positioned at a particular location with a weather optimal heading. Computer simulations incorporating realistic environmental disturbances are used to illustrate the performance of the suggestedWOHC andWOPC systems.
BibTeX: @inproceedings{Kjerstad2010, author = {Ø. Kjerstad and M. Breivik}, title = {Weather Optimal Positioning Control for Marine Surface Vessels}, booktitle = {IFAC CAMS}, year = {2010} }
Kjerstad, Ø., Skjetne, R. & Jenssen, N.A.	Disturbance rejection by acceleration feedforward: Application to dynamic positioning [Abstract] [BibTeX]	2011	IFAC World Congress	inproceedings
Abstract: This paper addresses environmental disturbance rejection in dynamic systems by means of acceleration feedforward. A feedforward structure calculates the environmental force and magnitude by comparing the filtered acceleration measurement with the acceleration due to actuation and known forces. Direct compensation of the environment by feedforward will alleviate the position and velocity feedback terms. The presented scheme compensates environmental disturbances affecting the system in addition to model uncertainties. First, the design is used for a mechanical system and illustrated for an inverted pendulum. Then, the main application, being a dynamic positioning system affected by ice forces in an Arctic operation, is controlled by acceleration feedforward to give enhanced performance.
BibTeX: @inproceedings{Kjerstad2011, author = {Ø. Kjerstad and R. Skjetne and N. A. Jenssen}, title = {Disturbance rejection by acceleration feedforward: Application to dynamic positioning}, booktitle = {IFAC World Congress}, year = {2011} }
Kotovirta, V., Jalonen, R., Axell, L., Riska, K. & Berglund, R.	A system for route optimization in ice-covered waters [Abstract] [BibTeX]	2009	Cold Regions Science and Technology Vol. 55, pp. 52-62	article
Abstract: Information about ice is indispensable to navigation in ice-covered sea areas. For vessels traveling long distances in ice, it is worth planning routes that will reduce fuel consumption and travel time, as well as the risk of ending up in hazardous areas or getting stuck in the ice. In addition to observations on board, there is a multitude of data sources available for seafarers like satellite images, ice model data, weather observations and forecasts. However, it is difficult for a human to take into consideration all the time-varying data parameters when planning a route. In this paper, a prototype system for optimizing routes through the ice field is presented. The system integrates state-of-the-art ice modeling, ship transit modeling, and an end- user system as a route optimization tool for vessels navigating in ice-covered waters. The system has recently been validated on board merchant vessels in the Baltic Sea, and the system's performance has been analyzed statistically using AIS data. Based on the AIS data analysis the mean relative error of the estimated transit time was 0.144 [s/s] with a standard deviation of 0.147 [s/s] for long routes (90-650 km), and 0.018 [s/s] with standard deviation of 0.193 [s/s] for 50 km route segments.
BibTeX: @article{Kotovirta2009, author = {Ville Kotovirta and Risto Jalonen and Lars Axell and Kaj Riska and Robin Berglund}, title = {A system for route optimization in ice-covered waters}, journal = {Cold Regions Science and Technology}, year = {2009}, volume = {55}, pages = {52-62} }
Krstić, M., Kanellakopoulos, I. & Kokotović, P.V.	Nonlinear and Adaptive Control Design [Abstract] [BibTeX]	1995		book
Abstract: The book: -Introduces the basic design tools and demonstrates their effectiveness through worked examples -Provides detailed proofs and application examples (active suspension, jet engine, induction motor, ...) -Develops adaptive backstepping, tuning functions, and modular designs with full state feedback -Generalizes the methodology to systems with output feedback -Describes the advantages of the new adaptive nonlinear techniques over traditional methods -Offers a systematic methodology for performance improvement -Provides new designs for linear systems which can be used independently from the rest of the book -Is self-contained with an extensive summary of stability and passivity prerequisites -Includes sixty illustrations and tables with design algorithms
BibTeX: @book{Krstic1995, author = {Miroslav Krstić and Ioannis Kanellakopoulos and Petar V. Kokotović}, title = {Nonlinear and Adaptive Control Design}, publisher = {John Wiley & Sons, Inc}, year = {1995} }
Kuehnlein, W.L.	Philosophies for dynamic positioning in ice-covered waters [Abstract] [BibTeX]	2009	Offshore Technology Conference	conference
Abstract: Approximately one third of the world�s known and not yet exploited reserves of hydro carbons are in Arctic and Subarctic areas. Consequently, the offshore technology is going towards Arctic. New developments for operation in ice are generating new exiting challenges for offshore and ship building industries all over the world. The paper describes the major challenges of dynamic positioned vessels in ice-covered waters. As the forces acting on vessels in ice and also their response are substantial different from the behavior in open waters, new philosophies and strategies have to be developed: How to keep vessels or offshore structures at a given position. Based on model test results from HSVA the paper explains the main challenges of dynamic station keeping in ice and describes the consequences on station keeping philosophies and strategies for ships and offshore structures in ice. As up to now no dynamic positioning system exists for ice covered waters the paper illustrates a new approach in order to reach this goal. The paper gives by far not a complete description of dynamic positioning of vessels in ice. But it summarizes where we are and what needs still to be done.
BibTeX: @conference{Kuehnlein2009, author = {Walter L. Kuehnlein}, title = {Philosophies for dynamic positioning in ice-covered waters}, booktitle = {Offshore Technology Conference}, year = {2009} }
Kukulya, A., Plueddemann, A., Austin, T., Stokey, R., Purcell, M., Allen, B., Littlefield, R., Freitag, L., Koski, P., Gallimore, E., Kemp, J., Newhall, K. & Pietro, J.	Under-ice Operations with a REMUS-100 AUV in the Arctic [Abstract] [BibTeX]	2010	2010 IEEE/OES Autonomous Underwater Vehicles	inproceedings
Abstract: Use of a REMUS-100 AUV to obtain hydrographic observations beneath coastal sea ice offshore of Barrow, Alaska is described. The work is motivated by the desire to obtain cross- shore hydrographic transects that would provide estimates of the transport of relatively dense, salty water from the Chukchi Sea to the Arctic Ocean in winter. The horizontal scales (~10 km), maximum water depths (~100 m) and desired measurements (temperature, salinity and velocity vs. depth) in the study region match the capabilities of a small AUV such as the REMUS-100. It was recognized that achieving the science goals would require increasing the range of acoustic navigation and communication as well as developing a robust approach to through-ice deployment and recovery. These needs drove three modifications to the AUV: 1) Incorporation of a lower frequency (10 kHz) transducer and associated hardware for navigation and communication, 2) Addition of special-purpose sensors and hardware in a hull extension module, 3) Development of a homing algorithm utilizing an Ultra-Short Base Line (USBL) array in the AUV nose cap. In March 2010, eight days of field work offshore of Barrow provided successful demonstration of the system. A total of 14 km of track lines beneath a coastal ice floe were obtained from four missions, each successfully terminated by net-capture recovery.
BibTeX: @inproceedings{kuk10, author = {A. Kukulya and A. Plueddemann and T. Austin and R. Stokey and M. Purcell and B. Allen and R. Littlefield and L. Freitag and P. Koski and E. Gallimore and J. Kemp and K. Newhall and J. Pietro}, title = {Under-ice Operations with a REMUS-100 AUV in the Arctic}, booktitle = {2010 IEEE/OES Autonomous Underwater Vehicles}, year = {2010} }
Leppeäranta, M.	The Drift of Sea Ice [Abstract] [BibTeX]	2011		book
Abstract: This book presents the fundamental laws of sea ice drift, as derived from the material properties of sea ice, the basic laws of mechanics, and the latest modeling techniques. Topics covered include the science of sea ice drift, forecasting velocity based on volume, size and shape, sea ice ridging and remote sensing, modelling of ice conditions, and the role of sea ice drift in oceanography, marine ecology and engineering.
BibTeX: @book{Leppearanta2011, author = {Matti Leppeäranta}, title = {The Drift of Sea Ice}, publisher = {Springer}, year = {2011}, edition = {2} }
Lindegaard, K.-P.W.	Acceleration Feedback in Dynamic Positioning [Abstract] [BibTeX]	2004	School: NTNU	phdthesis
Abstract: This dissertation contains new results on the design of dynamic positioning (DP) systems for marine surface vessels. A positioned ship is continuously exposed to environmental disturbances, and the objective of the DP system is to maintain the desired position and heading by applying adequate propeller thrust. The disturbances can be categorized into three classes. First, there are stationary forces mainly due to wind, ocean currents, and static wave drift. Secondly, there are slowly-varying forces mainly due to wave drift, a phenomenon experienced in irregular seas. Finally there are rapid, zero mean linear wave loads causing oscillatory motion with the same frequency as the incoming wave train. The main contribution of this dissertation is a method for better compensation of the second type of disturbances, slowly-varying forces, by introducing feedback from measured acceleration. It is shown theoretically and through model experiments that positioning performance can be improved without compromising on thruster usage.
BibTeX: @phdthesis{Lindegaard2004, author = {Karl-Petter W. Lindegaard}, title = {Acceleration Feedback in Dynamic Positioning}, school = {NTNU}, year = {2004} }
Lubbad, R. & L�set, S.	A numerical model for real-time simulation of ship�ice interaction [Abstract] [BibTeX]	2011	Cold Regions Science and Technology Vol. 65, pp. 111-127	article
Abstract: A ship advancing in level ice will introduce several failure processes to the ice sheet, such as localised crushing and breaking due to bending stresses. The resulting ice fragments will interact with each other, with water and with the hull of the ship. They may rotate, collide, or slide along ship's hull, and eventually they will be cleared away. The situation is different in a broken ice field, i.e., large ice floes may behave similar to level ice while smaller floes will mostly be pushed aside, rotated or submerged. Modelling of such a complex system is very demanding and often computationally expensive which would typically hinder the chances for real-time simulations. This kind of simulations can be very useful for training personnel for Arctic offshore operations and procedures, for analysing the efficiency of various ice management concepts and as a part of the onboard support systems for station keeping. The challenge of meeting the real-time criterion is overcome in the present paper. The paper describes a numerical model to simulate the process of ship�ice interaction in real- time. New analytical closed form solutions are established and used to represent the ice breaking process. PhysX is used for the first time to solve the equations of rigid body motions in 6 degrees of freedom for all ice floes in the calculation domain. The results of the simulator are validated against experimental data from model-scale and full-scale tests. The validation tests exhibited a satisfactory agreement between the model calculations and experimental measurements.
BibTeX: @article{lub11, author = {Raed Lubbad and Sveinung L�set}, title = {A numerical model for real-time simulation of ship�ice interaction}, journal = {Cold Regions Science and Technology}, year = {2011}, volume = {65}, pages = {111-127} }
Moran, K., Backman, J. & Farrell, J.W.	Deepwater drilling in the Arctic Ocean�s permanent sea ice [Abstract] [BibTeX]	2006	Vol. 302Proceedings of the Integrated Ocean Drilling Program	inproceedings
Abstract: A fundamentally new multiple-vessel approach was developed under the auspices of the Ocean Drilling Program and the Inte- grated Ocean Drilling Program (IODP) to drill and recover deeply buried sediments in the Arctic Ocean. This approach overcame the difficulty of maintaining position over a drill site and recover- ing sediments in waters that are covered in moving ice floes. In August 2004, a convoy of three icebreakers met at the ice edge, northwest of Franz Josef Land, and headed north to begin the Arc- tic Coring Expedition, IODP Expedition 302. This expedition suc- cessfully recovered core at depths >400 meters below seafloor in 9/ 10 ice-covered water depths ranging from 1100 to 1300 m. Expe- dition 302 involved >200 people, including scientists, technical staff, icebreaker experts, ice management experts, ships� crew, and educators. At the drill site, temperatures hovered near 0�C and oc- casionally dropped to �12�C. Ice floes 1�3 m thick blanketed 90% (i.e., >9/10 ice cover) of the ocean surface, and ice ridges, several meters high, were encountered where floes converged. The ice drifted at speeds of up to 0.3 kt and changed direction over short time periods, sometimes within 1 h. A Swedish diesel-electric ice- breaker, the Vidar Viking was converted to a drill ship for this ex- pedition by adding a moonpool and a geotechnical drilling sys- tem capable of suspending >2000 m of drill pipe through the water column and into the underlying sediments. Two other ice- breakers, a Russian nuclear vessel, the Sovetskiy Soyuz, and a Swed- ish diesel-electric vessel, the Oden protected the Vidar Viking by circling �upstream� in the flowing sea ice, breaking the floes into smaller pieces that wouldn�t dislodge the drilling vessel >75 m from a fixed position. Despite thick and pervasive ice cover, the fleet and ice management teams successfully enabled the drilling team to recover cores from three sites. Ice conditions became un- manageable only twice, forcing the fleet to retrieve the pipe and move away until conditions improved. The scientific results from this drilling will significantly advance our understanding of Arctic and global climate.
BibTeX: @inproceedings{Moran2006, author = {Kathryn Moran and Jan Backman and John W. Farrell}, title = {Deepwater drilling in the Arctic Ocean�s permanent sea ice}, booktitle = {Proceedings of the Integrated Ocean Drilling Program}, year = {2006}, volume = {302} }
Morrison, J.	New DP-Capable Icebreaker for the Great Lakes [Abstract] [BibTeX]	2005	Dynamic Positioning Conference	conference
Abstract: The United States Coast Guard�s construction of a new heavy icebreaker for the U.S. Great Lakes is a major acquisition program (over $100 million) that will field a state-of-the-market, multi- mission cutter capable of effectively replacing two World War II vintage cutters, a single mission heavy icebreaker and a buoy tender with limited multi-mission capability. The new cutter�s extensive dynamic positioning capability will be integral to her aids to navigation mission and the Coast Guard plans to test the DP system�s ability to assist with the icebreaking mission as well.
BibTeX: @conference{Mor05, author = {James Morrison}, title = {New DP-Capable Icebreaker for the Great Lakes}, booktitle = {Dynamic Positioning Conference}, year = {2005} }
Nguyen, D.H., Nguyen, D.T., Quek, S.T. & S�rensen, A.J.	Position-moored drilling vessel in level ice by control of riser end angles [Abstract] [BibTeX]	2011	Cold Regions Science and Technology Vol. 66, pp. 65-74	article
Abstract: This paper focuses on the control of marine riser of a position-moored drilling vessel operating under level ice regime with different ice thicknesses. The strategy is to ensure that the riser end angles (REAs) are within the safe limits for drilling and work-over operations by keeping the vessel at an appropriate position. Using a control criterion based on REAs, the desired vessel position is computed to counteract the environmental disturbances. An optimal set-point chasing algorithm is used to control the mooring lines by adjusting their lengths to bring the vessel to the desired position. The ice load model of Nguyen et al. (2009) was used to simulate the vessel�ice interaction. Numerical simulation results of a moored drilling vessel first exposed to open water and then to level ice of different thicknesses indicated that the proposed control strategy performs satisfactorily in level ice regime. The riser end angles and bending stresses along the riser are reduced considerably when in automatic control mode.
BibTeX: @article{ngu11, author = {Dat H. Nguyen and Dong T. Nguyen and Ser T. Quek and Asgeir J. S�rensen}, title = {Position-moored drilling vessel in level ice by control of riser end angles}, journal = {Cold Regions Science and Technology}, year = {2011}, volume = {66}, pages = {65-74} }
Nguyen, D.T., S�rb�, A.H. & S�rensen, A.J.	Modelling and Control for Dynamic Positioned Vessels in Level Ice [Abstract] [BibTeX]	2009	Proceedings of 8th Conference on Manoeuvring and Control of Marine Craft, pp. 229-236	inproceedings
Abstract: The aim of this paper is to propose a mathematical model for simulating the behaviour of a dynamic positioned (DP) vessel operating in level ice. The process of ice-vessel interaction is assumed to be a sequence of breaking events of the ice plate. Each breaking event is a cycle of crushing and bending. The form of the edge of the broken ice floe due to bending is assumed to be circular. The ice load due to bending, submersion, and velocity dependence is constant and is calculated from the ice resistance. The simulated ice load will be validated and compared to the empirical ice resistance. Based on the level ice model, a new output feedback controller for DP will be proposed. Furthermore, a supervisory switching mechanism is proposed to cope with the in-and-out of ice regime scenario. The proposed controller is validated through the simulations which showed that the proposed controller performed better in level ice than the conventional one for open water. The study confirms the importance of the ice-load model for DP control design.
BibTeX: @inproceedings{ngu09, author = {Dong T. Nguyen and Arild H. S�rb� and Asgeir J. S�rensen}, title = {Modelling and Control for Dynamic Positioned Vessels in Level Ice}, booktitle = {Proceedings of 8th Conference on Manoeuvring and Control of Marine Craft}, year = {2009}, pages = {229-236} }
Obert, K.M. & Brown, T.G.	Ice Ridge Keel Characteristics and Distribution in the Northumberland Strait [Abstract] [BibTeX]	2011	Cold Regions Science and Technology Vol. 66, pp. 53-64	article
Abstract: Ice ridges impacts are a major design consideration for offshore structures in the Arctic. Consequently, field programs on the frequency and characteristics of ridges can provide valuable empirical information for the design of future offshore structures. The Confederation Bridge ice force monitoring program monitors ice ridge keels through sonar instrumentation at the bridge. A total of 3199 keel cross-sections were identified during the 2007 and 2008 ice seasons using a new processing method. Of the 3199 keels identified, 137 keels caused loads over 1MN. The shape of each keel was visually identified and classified as one of four shapes: triangular, trapezoidal, w-shaped, and multiple peak keels. Triangular and trapezoidal keels made up more than 60% of the keels that cause loads over 1MN. Four of the five largest loads had keels that were trapezoidal. For the 3199 keel cross-sections, the depth, width, leading and trailing keel angles, bottom width and area were identified and distributions of these keel properties were developed. The distribution was then compared to the design keel depth distribution from the Confederation Bridge. The observed 2007 and 2008 keel depth distribution was slightly lower than the design distribution likely due to the significant number of multiple peak and w-shaped keels. Additionally, the maximum keel depth suggested by the observed distribution was shallower than the maximum predicted keel depth.
BibTeX: @article{obe11, author = {Keely M. Obert and Thomas G. Brown}, title = {Ice Ridge Keel Characteristics and Distribution in the Northumberland Strait}, journal = {Cold Regions Science and Technology}, year = {2011}, volume = {66}, pages = {53-64} }
Proakis, J.G. & Manolakis, D.K.	Digital Signal Processing. Principles, Algorithms, and Applications [Abstract] [BibTeX]	2007		book
Abstract: Presents the fundamentals of discrete-time signals, systems, and modern digital processing algorithms and applications for students in electrical engineering, computer engineering, and computer science. Textbook. DLC: Signal processing - Digital techniques.
BibTeX: @book{Proakis2007, author = {John G. Proakis and Dimitris K Manolakis}, title = {Digital Signal Processing. Principles, Algorithms, and Applications}, publisher = {Prentice Hall}, year = {2007}, edition = {4th} }
Rao, C.V., Rawlings, J.B. & Mayne, D.Q.	Constrained State Estimation for Nonlinear Discrete-Time Systems: Stability and Moving Horizon Approximations [Abstract] [BibTeX]	2003	IEEE Transactions on Automatic Control Vol. 48(2), pp. 246-258	article
Abstract: State estimator design for a nonlinear discrete-time system is a challenging problem, further complicated when addi- tional physical insight is available in the form of inequality con- straints on the state variables and disturbances. One strategy for constrained state estimation is to employ online optimization using a moving horizon approximation. In this article we propose a gen- eral theory for constrained moving horizon estimation. Sufficient conditions for asymptotic and bounded stability are established. We apply these results to develop a practical algorithm for con- strained linear and nonlinear state estimation. Examples are used to illustrate the benefits of constrained state estimation. Our frame- work is deterministic.
BibTeX: @article{Rao2003, author = {Rao, C. V. and Rawlings, J. B. and Mayne, D. Q.}, title = {Constrained State Estimation for Nonlinear Discrete-Time Systems: Stability and Moving Horizon Approximations}, journal = {IEEE Transactions on Automatic Control}, year = {2003}, volume = {48}, number = {2}, pages = {246--258} }
Sheykin, I.B.	Icebreaker Reconnaissance for Ice Management: offshore experience [Abstract] [BibTeX]	2010	20th IAHR International Symposium on Ice	conference
Abstract: A significant experience and innovations are accumulated during past decade in the area of ice management (IM). As for example Arctic Coring Expedition - 2004 of Swedish Polar Research Secretariat for Int. Ocean Drilling Program, as well as IM Program 1999 - 2008 of AKAC Inc. for operational support of Sakhalin-II offshore project. Usually few icebreakers participate in the full scale IM operations. Depending of ice conditions the frontal icebreaker combined the functions of IM vessel and of ice reconnaissance (IR) vessel. This paper presents a description of new technologies of ice observation and mapping onboard of IR vessel. There are applications of digital camera, Bridge Master radar and Ice Radar for the visual and radar ice observations, mapping and measurements as well as of onboard navigation system for the physical estimates of ice conditions. A detail information from IR vessel together with helicopter and satellite information produce the optimum conditions for the work of risk analysis and alarm system.
BibTeX: @conference{she10, author = {Igor B. Sheykin}, title = {Icebreaker Reconnaissance for Ice Management: offshore experience}, booktitle = {20th IAHR International Symposium on Ice}, year = {2010} }
Su, B., Riska, K. & Moan, T.	A numerical method for the prediction of ship performance in level ice [Abstract] [BibTeX]	2010	Cold Regions Science and Technology Vol. 60, pp. 177-188	article
Abstract: A numerical method is introduced to simulate ship maneuvers in level ice. The coupling between continuous ice forces and ship motions is considered, and the three degree-of-freedom rigid body equations of surge, sway and yaw are solved by numerical integration. The numerical analysis is validated by comparison with the ship performance data from the ice trails of icebreaker AHTS/IB Tor Viking II. A good agreement is achieved.
BibTeX: @article{bsu10, author = {Biao Su and Kaj Riska and Torgeir Moan}, title = {A numerical method for the prediction of ship performance in level ice}, journal = {Cold Regions Science and Technology}, year = {2010}, volume = {60}, pages = {177-188} }
Timco, G.W. & Burden, R.P.	An analysis of the shapes of sea ice ridges [Abstract] [BibTeX]	1997	Cold Regions Science and Technology Vol. 25, pp. 65-77	article
Abstract: An analysis has been made of the salient features of 112 first-year and 64 multi-year sea ice ridges. Based on this information, the important characteristics of the ridges have been related through simple equations. In particular, the ratio of the keel-depth to sail-height was found to be 4.4 for first-year ridges, and 3.3 for multi-year ridges; the ratio of the keel-area to sail-area was 8.0 for first-year ridges and 8.8 for multi-year ridges. Also, for first-year ridges, the ratio of the keel-width to sail-height was approximately 15, and the ratio of the keel-width to keel-depth was 3.9. An analysis of the sail and keel angles indicates a distribution of values with an average sail angle of 21� for temperate ridges, and 33� for ridges in the Beaufort Sea. In this paper, the results of this analysis are described, and the important ridge characteristics are discussed.
BibTeX: @article{tim97, author = {G. W. Timco and R. P. Burden}, title = {An analysis of the shapes of sea ice ridges}, journal = {Cold Regions Science and Technology}, year = {1997}, volume = {25}, pages = {65-77} }
Timco, G.W. & Weeks, W.F.	A review of the engineering properties of sea ice [Abstract] [BibTeX]	2010	Cold Regions Science and Technology Vol. 60, pp. 107-129	article
Abstract: Operations in ice-covered waters require good engineering to ensure the safety of personnel and the environment. In polar regions, the presence of sea ice is the main factor hindering the operations. It affects shipping, and oil and gas exploration and development. This paper looks at the stage of knowledge and applications of the engineering properties of sea ice. The physical properties (microstructure, thickness, salinity, porosity, and density) and the mechanical properties (tensile, flexural, shear, uni-axial compression and multi-axial compression strength, borehole strength, failure envelope, creep, elastic and strain modulus, Poisson's ratio, fracture toughness and friction) are explored. The paper outlines these properties for both first-year sea ice and Old Ice (i.e. second-year and multi-year sea ice). Although some properties are reasonably well understood (microstructure, salinity, flexural strength, compressive strength, and elastic modulus), others are not. Knowledge of Old Ice is particularly limited.
BibTeX: @article{tim10, author = {G. W. Timco and W. F. Weeks}, title = {A review of the engineering properties of sea ice}, journal = {Cold Regions Science and Technology}, year = {2010}, volume = {60}, pages = {107-129} }
Weissling, B., Ackley, S., Wagner, P. & Xie, H.	EISCAM � Digital image acquisition and processing for sea ice parameters from ships [Abstract] [BibTeX]	2009	Cold Regions Science and Technology Vol. 57(1), pp. 49-60	article
Abstract: Human observations and records of sea ice conditions from ships of opportunity in polar regions have been formalized under ASPeCt (Antarctic Sea Ice Processes and Climate) protocols as part of the Scientific Committee on Antarctic Research (SCAR) initiative, Global Change in Antarctica. Human observations, however, are subject to both bias and level of expertise. In support of ASPeCt observations, a ship-based, ice condition imagery acquisition, processing and analysis system is developed and presented in this paper. Digital images captured from recorded oblique-view video of sea ice during the inbound and outbound transits of the icebreaker NB Palmer, during the 2007 SIMBA (Sea Ice Mass Balance in Antarctic) cruise, were used to demonstrate the method. The resultant orthorectified and spatially registered images can thus be used to derive ice concentration, ice types, floe sizes, and area of deformed ice, parameters recorded by an ASPeCt observer based on experience. An assessment of total ice concentration, utilizing a digital number threshold method, for a 30 image sequence spanning 10 min, was compared to the corresponding ASPeCt observation and found good agreement. A k-means unsupervised classification technique was employed to evaluate the spectral separability of pixels associated with differing ice types. A significant source of visual perspective bias was discovered in associated with uneven spatial distribution of open-water leads. Convolution spatial filtering was employed to assess area of deformed ice during night-time conditions, when ship's floodlights illuminate the ice field. Transformation of individual image elements, such as floes, to vector-based polygons enabled accurate measurement of dimension, thus providing a frequency distribution of floe sizes, currently not possible with existing ASPeCt protocols. Limitations of this acquisition and analysis technique, future improvements, and coordination with the ASPeCt program were discussed.
BibTeX: @article{Weissling2009, author = {B. Weissling and S. Ackley and P. Wagner and H. Xie}, title = {EISCAM � Digital image acquisition and processing for sea ice parameters from ships}, journal = {Cold Regions Science and Technology}, year = {2009}, volume = {57}, number = {1}, pages = {49-60} }
Wright, B.D. & Timco, G.W.	First-year ridge interaction with the Molikpaq in the Beaufort Sea [Abstract] [BibTeX]	2001	Cold Regions Science and Technology Vol. 32, pp. 27-44	article
Abstract: This paper presents details of the failure behaviour and loads associated with the interaction of first-year ridges with the offshore structure Molikpaq. An analysis was made of ridge interactions during 2 years of deployment of the Molikpaq in the Canadian Beaufort Sea. The first-year ridge interactions were complex and characterized by a complicated sequence of ice failures that are largely dependent on the particulars of the ridge and the interaction event. Typical ridge failure modes included spine failures, failing behind the ridge, shearing, stopping and mixed modal. Typical load levels ranged from 30 to 100 MN for first-year ridges with sail heights up to 2.5 m. For these ridges, the ridge line load [PLL in MN/m] was related to the ridge sail height wHs in mx by PLL=0.36Hs+0.25.
BibTeX: @article{wri01, author = {B. D. Wright and G. W. Timco}, title = {First-year ridge interaction with the Molikpaq in the Beaufort Sea}, journal = {Cold Regions Science and Technology}, year = {2001}, volume = {32}, pages = {27-44} }
Zhao, B., B.M. & Skjetne, R.	Particle Filter ROV Navigation using Hydroacoustic Position and Speed Log Measurements [Abstract] [BibTeX]	2012	American Control Conference (submitted)	inproceedings
Abstract: An integrated navigation system design is presented for an underwater remotely operated vehicle (ROV). The available navigation information is an acoustic position measurement and a Doppler log speed measurement. Both measurements are studied in detail and modeled statistically. A kinematic model is assigned to the ROV with its driving noise from a Gaussian mixture, and a particle filter is suggested to estimate ROV position and velocity. The advantages of using a particle filter in this ROV navigation scheme are: 1) to make full use of all available information to improve the estimation performance, such as the speed measurement that is a nonlinear function of the states; 2) the particle filter makes good use of a Gaussian mixture as the driving noise, which makes the ROV kinematic model more realistic in both high and low frequency ranges; 3) a good estimate of the ROV velocity vector is achieved. The algorithm of the particle filter is presented and verified through a simulation based on real data. This shows that the estimation performance of the particle filter is clearly better than that of a Kalman filter.
BibTeX: @inproceedings{Zhao2012, author = {Zhao, B., Blanke, M., and Skjetne, R.}, title = {Particle Filter ROV Navigation using Hydroacoustic Position and Speed Log Measurements}, booktitle = {American Control Conference (submitted)}, year = {2012} }

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