A new operability and predictability enhanced riser control system for deepwater marine operation: an integrated riser hybrid tensioning system

This dissertation presents a novel riser hybrid tensioning system by integrating an electrically powered riser tensioning system into existing hydro-pneumatic tensioners. Compared to current passive hydro-pneumatic tensioners, this new riser hybrid tensioning system provides the capability of dynamically controlling the tension in the riser string. This feature opens a wide horizon of different active riser control strategies to achieve the systematic riser control solution. The objective of this study is to increase the predictability and safety of the whole riser system, and to extend the operability of the riser tensioning system into other operations. An overall structure framework of this novel hybrid riser tensioning system is proposed, comprising a direct driven electrical tensioners, hydro-pneumatic tensioners, a super-capacitor based energy storage system, power dissipaters, an overall tension controller and a power management controller. Hardware configurations are suggested. A riser data logging system is introduced, providing more comprehensive riser status data. A power management control strategy and overall coordination architecture to integrate the whole system are proposed. As the main functionality of the riser tensioning system, a new active heave compensation control strategy is analyzed in detail, by using this new riser hybrid tensioning system. A LQG controller and a H [subscript infinity symbol] controller are designed. The position chasing technique produces predictive and accurate tension commands for the electrical tensioners. Both Matlab simulation and hardware implementation confirm the feasibility of this concept, and further verifies that a more accurate control performance could be achieved by the electrical tensioners 180° compensating the tension fluctuation caused by the hydro-pneumatic tensioners. A novel testability and predictability enhanced anti-recoil control algorithm is implemented in the electrical tensioners. A position control strategy is proposed with the objective of moving the riser body to a desired elevation height in a predictive manner. A system model and a Kalman estimator are built, and a LQG controller is designed. The simulation demonstrates that the riser lifting height can adjust to any reasonable value for different test environment. This anti-recoil control concept reduces the risk of catastrophic damage, and allows us to perform maintenance tests much more frequently to bring back operator’s confidence. During harsh sea state, the VIV can be suppressed by using the dynamic control of the hybrid tensioning system, at frequencies and magnitudes made available by the electrical tensioning system. The objective is to achieve the VIV suppression by avoiding the excitation of the oscillation locking into the resonance conditions, and by reducing oscillation energy to be built in riser. A modal analysis of a tensioned Euler-Bernoulli beam is studied. Two control methods are proposed. Simulations results demonstrate that the oscillation is effectively reduced at the dominant lock-in frequency. Finally, this riser hybrid tensioning system opens the possibility to extend the tensioning system operability into other drilling operations. A motion stabilizer supporting the heave compensation of the drill pipes and the DST tools can be eliminated by connecting the drill pipes onto the telescopic joint. Another application would be that the electrical tensioners can run under position control mode after the riser is recoiled and soft hang-off on tensioners. The riser string position with respect to the seabed can still be controlled, during the vessel moving among different well heads.Electrical and Computer Engineerin

Using Digital Hydraulics in Secondary Control of Motor Drive

Due to the increased focus on pollution and global warming, there is a demand for energy efficient systems. This also applies to the offshore oil and gas industry. Normally used hydraulic systems tend to suffer from low energy efficiency, especially when operating with part loads. In the last decades, a new pump and motor technology has experienced increased interest due to the potential of high energy efficiency in a wide range of operation conditions. This new technology is called digital displacement machine technology. Nowadays, there is a desire from the offshore oil and gas industry to use this digital displacement machine technology to design highly efficient hydraulic winch drive systems. The main objectives of the work presented in this thesis are to design a controller for a digital displacement winch drive system and evaluate its control performance. The design of a controller is one part of the work needed to realizing a winch drive system with digital displacement machines. A winch with a lifting capacity of 20000 kg and a drum capacity of 3600 m of wire rope is used as a case study. Digital displacement machines have strict requirements for the on/off valves used to control each cylinder chamber. It is important to activate the valves at optimal times to ensure operation with high energy efficiency and low pressure and flow peaks. Only a small mistiming of the valves will affect the performance of the digital displacement machine significantly. One of the first contributions presented in this thesis is a method for defining how early or late the valves can be timed without reducing the energy efficiency significantly. The control of digital displacement machines is complicated and non-conventional. Each cylinder can be controlled individually and multiple displacement strategies can be used to achieve the same displacement. Each displacement strategy has its dynamic response characteristics and energy efficiency characteristics. The dynamic response characteristics of the drive system are highly relevant when designing control systems. Therefore, in addition to the conventional classical controller, also a suitable displacement strategy must be designed. Designing controllers for digital displacement machines are therefore more complex than designing controllers for conventional hydraulic machines. One of the main focuses of this project has been to analyze the transient and steady state response characteristics of different displacement strategies. In all, three displacement strategies are examined: full stroke displacement strategy, partial stroke displacement strategy and sequential partial stroke displacement strategy. Also, during this work, a new version of the partial stroke displacement strategy has been developed and included in the dynamic response analysis. The dynamic response analysis is a simulation study, where the simulation model is experimentally validated. The experimental work is conducted on a prototype of a single cylinder digital displacement machine. The prototype consists of a five cylinder radial piston motor where one cylinder is modified to operate with the digital displacement technology. The rest of the cylinders are not changed and not used. In addition to validating the simulation model, the prototype is used to test all of the analyzed displacement strategies in low speed operation. The results from the dynamic response analysis are used to select the displacement strategy that is most suited for use in a winch drive system. Then, controllers for the digital displacement winch drive system are developed. The main focus in the control design phase is not to design a new type of controller but to examine already developed controllers and fit them to a winch system driven by digital displacement machines. In the end, the simulation results of the designed controllers are shown and the results are discussed. The simulation results show that digital displacement machines can be used in winch drive systems and achieve both high motion control performance and wire tension control performance.publishedVersio

Relating onshore wind turbine reliability to offshore application

With the award of the latest Round 3 offshore wind farm sites around the UK coast the wind industry is moving from the operation of near inshore to truly offshore wind farms. This has two major implications, the first being that wind turbines are now being specifically designed for offshore deployment, a key feature being that the new wind turbines are likely to be two to four times the size of the largest current onshore machines. The second is that due to the limitations of access to offshore wind turbines, their availability needs to be in the order of 98% or greater if reasonable costs of energy are to be achieved. The distance of the wind turbines from shore means that more attention needs to be given to the availability, reliability and maintainability of these offshore wind turbines. The research discussed in this report set out to examine these factors in more depth, using the reliability data of Clipper Windpower’s onshore 2.5 MW Liberty machine as the practical evidence for doing so. In analysing the data the primary aim was to build a picture of typical fault type and duration and more specifically alarm type, distribution and alarm quantity. These results were then compared with an external data source to identify common trends or major divergences and the findings used to identify potential improvements in availability, reliability and maintainability for the design of Clipper Windpower’s offshore Britannia 10 MW machine. The key conclusions of the research are that: The Britannia wind turbine pitch system needs dramatic improvement on that of the Liberty wind turbine and this requires further detailed investigation. The ability to access the wind farms quickly and cost effectively will be critical to maintaining the required levels of wind turbine availability. The Britannia wind turbine needs to be designed for reliability and availability not simply for keeping the wind turbine in a safe mode. The number and classification of alarms built into the wind turbine monitoring system needs to be critically reviewed with the aim of reducing and rationalising responses where possible

Offshore Wind Farms

The coastal zone is the host to many human activities, which have significantly increased in the last decades. However, sea level rise and more frequent storm events severely affect beaches and coastal structures, with negative consequences and dramatic impacts on coastal communities. These aspects add to typical coastal problems, like flooding and beach erosion, which already leading to large economic losses and human fatalities. Modeling is thus fundamental for an exhaustive understanding of the nearshore region in the present and future environment. Innovative tools and technologies may help to better understand coastal processes in terms of hydrodynamics, sediment transport, bed morphology, and their interaction with coastal structures. This book collects several contributions focusing on nearshore dynamics, and span among several time and spatial scales using both physical and numerical approaches. The aim is to describe the most recent advances in coastal dynamics

ESSE 2017. Proceedings of the International Conference on Environmental Science and Sustainable Energy

Environmental science is an interdisciplinary academic field that integrates physical-, biological-, and information sciences to study and solve environmental problems. ESSE - The International Conference on Environmental Science and Sustainable Energy provides a platform for experts, professionals, and researchers to share updated information and stimulate the communication with each other. In 2017 it was held in Suzhou, China June 23-25, 2017

Backlash in slew bearings : the advantages of an all-electric drive system

Master's thesis Mechatronics MAS500 - University of Agder, 2012Konfidensiell til / confidential until 01.07.201

Improving Energy Efficiency and Motion Control in Load-Carrying Applications using Self-Contained Cylinders

Because of an increasing focus on environmental impact, including CO2 emissions and fluid spill pollution, inefficient hydraulic systems are being replaced by more environmentally friendly alternatives in several industries. For instance, in some offshore applications that have multiple diesel generators continuously running to produce electricity, all hydraulic rotating actuators supplied from a central hydraulic power unit have been replaced with AC induction motors containing a variable frequency drive and gearbox. However, hydraulic linear actuators are still needed in most load-carrying applications mainly because of their high reliability associated with external impact shocks. Moreover, their force capacity is higher than that of their linear electromechanical counterparts. Valve-controlled linear actuators (cylinders) supplied from a centralized hydraulic power unit are standard in offshore load-carrying applications. In addition to the advantages mentioned above of hydraulic linear actuators, they have, nevertheless, a number of important drawbacks, which include: 1) a high level of energy consumption due to significant power losses caused by flow throttling in both the pipelines and valves, 2) reduced motion performance due to the influence of load-holding valves, 3) high CO2 emissions and fuel costs related to the diesel generator that supplies electricity to the hydraulic power unit, 4) significant potential for hydraulic fluid leakage because of many leakage points, 5) demanding efforts with respect to installation and maintenance, as well as 6) costly piping due to the centralized hydraulic power supply. The work presented in this dissertation and the appended papers are devoted to replacing inefficient hydraulic linear actuation systems traditionally used in offshore load-carrying applications with more environmentally friendly solutions. Two alternative technologies are identified, namely electro-mechanical and electro-hydraulic self-contained cylinders. The feasibility of replacing conventional valve-controlled cylinders with self-contained cylinder concepts is investigated in two relevant case studies.publishedVersio

Volume 3 – Conference

We are pleased to present the conference proceedings for the 12th edition of the International Fluid Power Conference (IFK). The IFK is one of the world’s most significant scientific conferences on fluid power control technology and systems. It offers a common platform for the presentation and discussion of trends and innovations to manufacturers, users and scientists. The Chair of Fluid-Mechatronic Systems at the TU Dresden is organizing and hosting the IFK for the sixth time. Supporting hosts are the Fluid Power Association of the German Engineering Federation (VDMA), Dresdner Verein zur Förderung der Fluidtechnik e. V. (DVF) and GWT-TUD GmbH. The organization and the conference location alternates every two years between the Chair of Fluid-Mechatronic Systems in Dresden and the Institute for Fluid Power Drives and Systems in Aachen. The symposium on the first day is dedicated to presentations focused on methodology and fundamental research. The two following conference days offer a wide variety of application and technology orientated papers about the latest state of the art in fluid power. It is this combination that makes the IFK a unique and excellent forum for the exchange of academic research and industrial application experience. A simultaneously ongoing exhibition offers the possibility to get product information and to have individual talks with manufacturers. The theme of the 12th IFK is “Fluid Power – Future Technology”, covering topics that enable the development of 5G-ready, cost-efficient and demand-driven structures, as well as individual decentralized drives. Another topic is the real-time data exchange that allows the application of numerous predictive maintenance strategies, which will significantly increase the availability of fluid power systems and their elements and ensure their improved lifetime performance. We create an atmosphere for casual exchange by offering a vast frame and cultural program. This includes a get-together, a conference banquet, laboratory festivities and some physical activities such as jogging in Dresden’s old town.:Group 8: Pneumatics Group 9 | 11: Mobile applications Group 10: Special domains Group 12: Novel system architectures Group 13 | 15: Actuators & sensors Group 14: Safety & reliabilit