| van den Berg M, Bjørnø J, Lu W, Skjetne R, Lubbad R and Løset S (2022), "The Value of High-Fidelity Numerical Simulations of Ice-Ship and Ice-Structure Interaction in Arctic Design with Informed Decisionmaking", In Informed Decisionmaking for Sustainability: Building Common Interests in the Arctic Ocean with Global Inclusion. Cham Vol. 2, pp. 151-177. Springer-Verlag. |
| Abstract: Long-term changes in the climate lead to an increase of activities in the Arctic. Ships and structures operating in Arctic waters may encounter sea ice and must be designed to withstand the loads resulting from ice-ship or ice-structure interactions. Traditionally, design rules for ships, structures and operations in ice-covered waters have been based on full-scale measurements and model-scale tests. Full-scale measurements and model-scale tests will remain important sources of data and knowledge in the future. Numerical simulations can give valuable additional insights into the processes and loads resulting from ice-ship and ice-structure interactions. The primary advantage of numerical modelling compared to full-scale measurements and model-scale tests is the marginal cost of testing. This enables the testing of a multitude of design options and ice conditions. Challenges in the application of numerical models are related to finding a balance between model efficiency and accuracy and model validation and calibration. |
BibTeX:
@incollection{mber22A,
author = {van den Berg, M. and Bjørnø, J. and Lu, W. and Skjetne, R. and Lubbad, R. and Løset, S.},
title = {The Value of High-Fidelity Numerical Simulations of Ice-Ship and Ice-Structure Interaction in Arctic Design with Informed Decisionmaking},
booktitle = {Informed Decisionmaking for Sustainability: Building Common Interests in the Arctic Ocean with Global Inclusion},
publisher = {Springer-Verlag},
year = {2022},
volume = {2},
pages = {151--177},
url = {https://link.springer.com/book/10.1007/978-3-030-89312-5},
doi = {10.1007/978-3-030-89312-5_10}
}
|
| Zhang Q and Skjetne R (2018), "Sea Ice Image Processing with Matlab" Boca Raton, FL, USA Taylor & Francis. |
| Abstract: The ice concentration data on a global scale are available on a daily basis due to microwave satellite sensors. Image processing for sea ice is vital to estimate the sea ice properties and understand the behavior of sea ice especially on a relatively small scale. Currently, sea ice concentration is estimated from lower-resolution passive microwave sensors. This book aims to present the most recent image processing techniques including the so-called gradient vector flow snake algorithm to identify individual ice floes from the ice images. It makes an extensive use of this powerful technique to extract or estimate the sea-ice parameters and to develop tools useful to scientists and engineers. |
| Comment: Series Editor: C.H. Chen |
BibTeX:
@book{qzha18A,
author = {Zhang, Q. and Skjetne, R.},
title = {Sea Ice Image Processing with Matlab},
publisher = {Taylor & Francis},
year = {2018},
note = {Signal and Image Processing of Earth Observations Series},
url = {https://www.crcpress.com/Sea-Ice-Image-Processing-with-MATLAB/Zhang-Skjetne/p/book/9781138032668}
}
|
| Skjetne R (2005), "The Maneuvering Problem". Thesis at: Norwegian Univ. Science & Technology. Trondheim, Norway |
| Abstract: The main contributions of this thesis is based on a new control problem statement called The Maneuvering Problem. This involves a desired path for the output of the system to follow and a speed assignment setting the desired motion along the path. This separation of tasks implies, on the one hand, that the design of the path and the desired motion along the path can be approached individually. On the other hand, this also introduces more flexibility in the development of the control law, since the desired motion along the path can be shaped by state feedback.
The main theoretical aspects are discussed in Chapters 2, 3, and 4. The Maneuvering Problem statement is presented in Chapter 2. A few application examples show how their respective control objectives can be conveniently set up as maneuvering problems by constructing a parametrized path and a speed assignment along the path. The last section of this chapter shows further that the problem statement implies the existence of a forward invariant manifold of the state space, represented by a desired noncompact set, to which all solutions must converge. Chapter 3 presents a constructive control design solving the maneuvering problem. A feedback linearizable system is, for clarity of presentation, used in this section, and most of the involved theoretical aspects concerning the control objective with design are addressed. First the static part of the control law is developed, solving essentially the geometric part of the problem. Then the loop is closed by the design of an update law that shapes the motion along the path. The last section of Chapter 3 considers further one of the proposed update laws and show that this incorporates a gradient optimization algorithm that will improve transient performance in the system. Uncertain systems are addressed in Chapter 4, and constructive designs based on ISS backstepping, adaptive backstepping, and sliding-mode are proposed for solving the maneuvering problem. In the backstepping designs, n design steps are first performed to derive the static part of the control law. Then the dynamic update law is constructed to bridge the path following objective with the speed assignment. In the sliding-mode design, a maneuvering control law is first designed for the nominal part of the plant, and then traditional techniques are used to deal with the uncertain part and develop the overall control law. Chapters 5 and 6 present applications of the theory, where the former chapter considers ships and the latter considers formation control. In Chapter 5, a fully actuated ship model is used, and specific maneuvering control laws are constructed based on adaptive backstepping, sliding-mode, and nonlinear PID techniques. Experimental results, using the model ship CyberShip II, are reported for each design. Experiments of both success and failure are discussed. Chapter 6 proposes a maneuvering setup and design for formation control of r vessels. Two formation control designs are proposed. The first develops decentralized control laws and a centralized dynamic guidance law, which includes the dynamic update law, to solve the problem. In the second design, the guidance law is further decentralized in order to reduce communication demand. Emphasis has been put on making the thesis coherent, starting with motivation and examples in the introduction, leading to the problem statement and its implications in Chapter 2, designs and analysis in Chapters 3 and 4, and finally applications with experimental results in Chapters 5 and 6. Moreover, Appendix A provides necessary background material on control theory, with emphasis on set-stability, and Appendix B reports an extensive work on modeling, system identification, and adaptive maneuvering with experiments performed for CyberShip II. |
BibTeX:
@phdthesis{rskj05B,
author = {Skjetne, R.},
title = {The Maneuvering Problem},
school = {Norwegian Univ. Science & Technology},
year = {2005},
url = {http://folk.ntnu.no/rskjetne/Publications/SkjetnePhDthesis_B5_compressed.pdf}
}
|
| Skjetne R (2002), "Maneuvering Control", In Marine Control Systems: Guidance, Navigation, and Control of Ships, Rigs, and Underwater Vehicles. Trondheim, Norway , pp. 394-416. Marine Cybernetics.
[BibTeX] |
BibTeX:
@incollection{rskj02B,
author = {Skjetne, R.},
editor = {Fossen, T.I.},
title = {Maneuvering Control},
booktitle = {Marine Control Systems: Guidance, Navigation, and Control of Ships, Rigs, and Underwater Vehicles},
publisher = {Marine Cybernetics},
year = {2002},
pages = {394--416}
}
|