Station-Keeping Trials in Ice: Dynamic Positioning in Ice — Results and Learnings

2018 ◽  
Author(s):  
Sofien Kerkeni ◽  
Pavel Liferov ◽  
Nicolas Serré ◽  
Robert Bridges ◽  
Finn Jorgensen
Keyword(s):  
Full Scale ◽  
Control Algorithms ◽  
Dynamic Positioning ◽  
Station Keeping ◽  
Positioning Systems ◽  
Ice Conditions ◽  
Drifting Ice ◽  
External Loads

Dynamic Positioning Systems are used in numerous types of marine operations. Due to the important differences in the external loads acting on the vessel, standard DP systems may fail to perform in ice conditions. Moreover, specific principles and position keeping philosophies should be applied in ice covered waters. The objective of the paper is to elaborate on these aspects by presenting and analyzing full scale DP tests. These tests were a part of the station-keeping trials performed in March 2017 in drifting ice in the Bay of Bothnia. Control algorithms limitations of Standard DP Systems are presented, showing the necessity of new control principles. The importance of crew training is also demonstrated along with the approaches to keep position in ice.

Aspects of Importance Related to Arctic DP Operations

2012 ◽  
Author(s):  
Arne Gürtner ◽  
Bror Henrik Heier Baardson ◽  
Glenn-Ole Kaasa ◽  
Erik Lundin
Keyword(s):  
Boundary Conditions ◽  
New Technology ◽  
Open Water ◽  
The Arctic ◽  
Dynamic Positioning ◽  
Positioning Systems ◽  
Business Opportunities ◽  
New Business ◽  
Drifting Ice

International operators are seeking, investigating and pursuing new business opportunities in the Arctic. While operating in the Arctic, there will be a considerable need for vessels to keep their position during various operations which may include lifting, installation, crew change, evacuation, and maybe drilling. Opposed to open water, the drifting ice poses severe limitations as to how stationkeeping operations may be carried out. Dynamic positioning systems are currently developed aiding stationkeeping without mooring systems. There is a considerable need to enhance the open water DP systems for use in a new forcing environment. Essentially a new technology has to be developed with time. For that reason, considerable knowledge is required concerning current limitations and boundary conditions. This paper addresses some of the generic challenges related to DP operations in ice together with relevant learnings which are employed in mentioned DP enhancements.

AMOS DP Research Cruise 2016: Academic Full-Scale Testing of Experimental Dynamic Positioning Control Algorithms Onboard R/V Gunnerus

2017 ◽  
Author(s):  
Roger Skjetne ◽  
Mikkel E. N. Sørensen ◽  
Morten Breivik ◽  
Svenn A. T. Værnø ◽  
Astrid H. Brodtkorb ◽  
...  
Keyword(s):  
Feedback Control ◽  
Performance Monitoring ◽  
Academic Research ◽  
Output Feedback Control ◽  
Time Instant ◽  
Feedback Mechanism ◽  
Full Scale ◽  
Control Algorithms ◽  
Control Law ◽  
Dynamic Positioning

In order to validate relevant dynamic positioning (DP) control algorithms in a realistic environment, a full-scale DP test campaign, the AMOS DP Research Cruise 2016 (ADPRC’16), was organized in a collaboration between the NTNU Centre for Autonomous Marine Operations and Systems (NTNU AMOS) and the company Kongsberg Maritime onboard the research vessel (R/V) Gunnerus. To the authors’ best knowledge, closed-loop DP feedback control algorithms have never been tested full-scale on a ship in an academic research experiment before. However, we have now achieved this by coding our algorithms into a test-module of the DP system, as prepared by Kongsberg Maritime. Among the tested algorithms is an output feedback control law with both good transient and steady-state performance. In another experiment, different adaptive backstepping control laws for DP were tested to compare and contrast their performance and properties. A hybrid state observer with a performance monitoring function proposed to switch between two observers, choosing the best one at any time instant, was also part of the test scope. For this, necessary measurements (including acceleration measurements) were logged to be able to rerun and validate the observer algorithms in post-processing. Finally, several experiments were done to test a pseudo-derivative feedback control law for DP. The feedback mechanism was tested with and without a feedforward disturbance rejection term, called acceleration feedforward. This paper reports the experimental setup, test program, and an overview of results from the ADPRC’16 campaign.

Station-Keeping Trials in Ice: Ice and Metocean Conditions

2018 ◽  
Author(s):  
Sigurd Henrik Teigen ◽  
Joakim K. Lindvall ◽  
Ilija Samardzija ◽  
Roar I. Hansen
Keyword(s):  
Spatial Data ◽  
Ice Core ◽  
Ocean Current ◽  
Ice Thickness ◽  
Physical Parameters ◽  
Station Keeping ◽  
Sea Bed ◽  
Ice Drift ◽  
Ice Conditions ◽  
Drifting Ice

In March 2017, Statoil performed station-keeping trials in drifting ice in the Bay of Bothnia with the two anchor handling tug supply vessels Magne Viking and Tor Viking. During the trials observations of ice and metocean conditions were performed via a range of platforms and techniques. The purpose of the observations was to document the main physical parameters affecting the station-keeping vessel and ice management vessel, as well as giving tactical information on ice conditions and input to simultaneous numerical simulations. Measurements of meteorological parameters (wind speed, wind direction, air temperature, etc.) were done from the two vessels and supplemented with manual observations. Ice drift was independently measured by drifting ice trackers and ADCPs (also measuring ocean current) moored on the sea bed. Measurements of ice thickness were carried out with moored Ice Profiling Sensors (IPSs) and manual ice core samples, which were also analyzed for salinity and temperature profiles. The IPS ice thickness data was later processed together with the ice drift to provide 2D spatial data. The deepest ice ridge keels ranged from 5.4 m at the site with the most benign ice conditions to 10.9 m at the most severe site. Ridge frequency also increased from 2 ridges km−1 to 16 ridges km−1 at the most severe site (given a keel threshold of 3 m). In the present study, statistical summaries of the different time series collected at the sites of the station-keeping trials are presented, highlighting the variability in the ice conditions. Using the vessel tracks and overall drift of the broken channels, ice thickness and drift measurements are classified as being inside or outside the managed ice zone.

Station-Keeping Trials in Ice: Overview of Ice Management Support

2018 ◽  
Author(s):  
Mike Neville ◽  
Erik Almkvist ◽  
Francesco Scibilia ◽  
Joakim K. Lindvall ◽  
Pavel Liferov
Keyword(s):  
Management Support ◽  
Station Keeping ◽  
Target Condition ◽  
Management Software ◽  
Sole Purpose ◽  
Planning Phase ◽  
Ice Conditions ◽  
Drifting Ice

In March 2017, Statoil performed station-keeping trials in drifting ice in the Bay of Bothnia. The anchor handling tug supply vessel Magne Viking, performed station keeping operations in various ice conditions, including managed and non-managed ice. Physical ice management was used to manage the approaching ice to a target condition suitable for the station keeping tests, and to enable other essential operations including deployment and retrieval of the mooring spread and other equipment. Given the objective of the trials, physical ice management activities were performed in such a way to allow investigation of various relevant parameters that influence the managed ice condition. Additional tests were also performed for the sole purpose to assist with validation of Aker Arctic’s ice management software “AIMS”, including tests designed to estimate the performance of the vessels under different ice conditions. This paper focuses on the physical ice management operations performed by the ice management vessel Tor Viking (TV) during the Station Keeping Trials in ice (SKT). Also included is a discussion on how AIMS was used in the planning phase and how simulations compared with actual observations.

Station-Keeping Trials in Ice: Numerical Modelling

2018 ◽  
Author(s):  
Nicolas Serre ◽  
Sofien Kerkeni ◽  
Dmitry Sapelnikov ◽  
Cyrille Akuetevi ◽  
Sergiy Sukhorukov ◽  
...  
Keyword(s):  
Data Collection ◽  
Numerical Modelling ◽  
Numerical Simulations ◽  
Single Point ◽  
Station Keeping ◽  
Broken Ice ◽  
Ice Conditions ◽  
Drifting Ice

In March 2017, Statoil performed station-keeping trials in drifting ice in the Bay of Bothnia with two anchor handling supply vessels; Magne Viking and Tor Viking. The data collection included monitoring of ice conditions and response of Magne Viking during ice interaction events. The present paper describes numerical simulations of broken ice and intact ice interaction events with single point moored Magne Viking.

Station-Keeping Trials in Ice: Project Overview

2018 ◽  
Author(s):  
Pavel Liferov ◽  
Thomas McKeever ◽  
Francesco Scibilia ◽  
Sigurd Henrik Teigen ◽  
Andreas Kjøl ◽  
...  
Keyword(s):  
Primary Objective ◽  
Project Planning ◽  
Maximum Amount ◽  
Full Scale ◽  
Physical Models ◽  
Station Keeping ◽  
Floating Structure ◽  
Quality Requirements ◽  
Drifting Ice ◽  
Scale Data

In March 2017, Statoil performed station-keeping trials in drifting ice in the Bay of Bothnia with two anchor handling tug supply vessels, Magne Viking and Tor Viking. The primary objective of the Station-keeping Trials in Ice project (SKT) was to gather full-scale data on a stationary floating structure in ice. The data will be used for validation of numerical and physical models, that will in turn increase confidence in modelling tools for design and operation in ice-covered waters. The principal requirement of the project was to safely collect the maximum amount of data meeting the quality requirements within the available budget and timeframe. This paper presents the overall project planning and execution, while more details are provided in the companion papers.

DP Ice Model Test of Arctic Drillship and Polar Research Vessel

2012 ◽  
Author(s):  
Torbjørn Hals ◽  
Nils Albert Jenssen
Keyword(s):  
Numerical Models ◽  
Offshore Structures ◽  
Model Tests ◽  
Full Scale ◽  
The Arctic ◽  
Research Vessel ◽  
Station Keeping ◽  
Ice Drift ◽  
Ice Conditions ◽  
Ice Model

The paper presents the results from a series of ice model tests performed as part of the DYPIC (Dynamic Positioning in Ice Conditions) research program. DYPIC is a research and development project within the EU’s ERA NET MARTEC project. The major purpose of the DYPIC project is development of equipment and methods for DP Ice Model testing which allows the prediction of station keeping capability of different vessel types and offshore structures under various ice conditions. The first DYPIC model tests performed in 2011 was conducted with two significantly different vessel sizes, a 68.0000 m3 volume displacement arctic drillship and an 8.600 m3 polar research vessel. The model scale was 1/30 for the arctic drillship and 1/18.6 for the Polar Research Vessel. The model tests were performed in the ice model basin at HSVA using vessel models equipped with thruster capacity similar to full scale operation according to DP class 2 / 3 operations. The DP control system was also modified from normal open water DP operations in order to cope with the highly varying ice drift loads acting on the vessel. The test program gave data supporting the development of numerical models of ice loads from managed ice, see reference [6]. The main focus in this paper is on the station keeping performance and associated thrust utilization as a function of varying ice drift loads. The results and data collected in the first year of the DYPIC program demonstrates that DP ice model tests will be a valuable tool for evaluation of vessel performance prior to moving on to full scale arctic DP operations.

Station-Keeping Trials in Ice: Test Scenarios

2018 ◽  
Author(s):  
Pavel Liferov ◽  
Nicolas Serre ◽  
Sofien Kerkeni ◽  
Robert Bridges ◽  
Fengwei Guo
Keyword(s):  
Measurement Data ◽  
Dynamic Positioning ◽  
Station Keeping ◽  
Operational Parameters ◽  
Drifting Ice ◽  
Test Scenarios ◽  
Insight Into

Station-keeping trials were undertaken in drifting ice in the Bay of Bothnia with two anchor handling supply vessels; Magne Viking and Tor Viking. This paper describes test scenarios which were performed with Magne Viking in moored, Dynamic Positioning and transit modes. An overview of the tests performed during the trials is presented, outlining the range of environmental and operational parameters. Examples of specific ice interaction scenarios are highlighted with illustrative measurement data providing observational insight into the performance and processes.

Probabilistic Fatigue Assessment of a Mooring Line Based on Station-Keeping Trials in Ice

2021 ◽  
Author(s):  
Chana Sinsabvarodom ◽  
Bernt J. Leira ◽  
Wei Chai ◽  
Arvid Naess
Keyword(s):  
Fatigue Damage ◽  
Probabilistic Models ◽  
Full Scale ◽  
Mooring Line ◽  
Stress Range ◽  
Station Keeping ◽  
Probability Models ◽  
Line System ◽  
Fatigue Assessment ◽  
Rainflow Counting

Abstract The intention of this work is to perform a probabilistic fatigue assessment of a mooring line due to loads associated with the station-keeping of a ship in ice. In March 2017, the company Equinor (Statoil) conducted full-scale tests by means of station-keeping trials (SKT) in drifting ice in the Bay of Bothnia. The vessel Magne Viking was employed in order to represent a supply vessel equipped with a mooring line system, and the realtime loading during the full-scale measurement was recorded. The second vessel Tor Viking was serving as an ice breaker in order to maintain the physical ice management activities with different ice-breaking schemes, i.e. square updrift pattern, round circle pattern, circular updrift pattern and linear updrift pattern. The fatigue degradation corresponding to these different patterns were investigated. The peaks and valleys of the mooring tension are determined using the min peak prominence method. For the purpose of probabilistic fatigue assessment, the Rainflow-counting algorithm is applied to estimate the mooring stress range. Fatigue assessment based both on Rainflow counting and fitted probabilistic models were performed. For the latter, the stress range distributions from the observed data of mooring loads are fitted to various probability models in order to estimate the fatigue damage. It is found that the stress ranges represented by application of the Weibull distribution for the probabilistic fatigue approach provides results of the fatigue damage most similar to the Rainflow counting approach. Among the different scenarios of Ice management schemes, the circular updrift pattern provides the lowest magnitude of the fatigue degradation.

Sign in / Sign up

Export Citation Format

Share Document