| 1. |
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| 2. |
- Allen, T., et al.
(författare)
-
Structural responses of high performance sailing yachts to slamming loads
- 2011
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Ingår i: 11th International Conference on Fast Sea Transportation, FAST 2011 - Proceedings. - 9780985066000 ; , s. 585-592
-
Konferensbidrag (refereegranskat)abstract
- Experimental measurements of transient strains, local accelerations and pressure were undertaken on the IMOCA Open 60' class sailing yacht Paprec-Virbac III, and on a replica hull panel section tested in a laboratory slam testing facility. The approximately 1m x 0.7m panel for laboratory testing was manufactured on a mould taken from the plug used for the vessel construction, ensuring that the panel had identical curved geometry to the vessel. The laboratory panel included two stringers as on the same region of the vessel. An instrumentation layout including arrays of resistance strain gauges, accelerometers and a transient pressure transducer was used. Linear displacement transducers were used to measure panel deformations during the laboratory tests. The laboratory testing was undertaken at a range of constant impact velocities from 0.5 to 3m/s using a Servohydraulic Slam Testing System. Sea-trials were undertaken in the Hauraki Gulf, Auckland New Zealand. There was good qualitative agreement between the field and laboratory measurements in regard to timing and relative magnitudes of strains at different positions on the structure. Results demonstrate that the hull structure undergoes very complex transient deformations during the slamming events.
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| 3. |
- Battley, Mark A., et al.
(författare)
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Effects of Panel Stiffness on Slamming Responses of Composite Hull Panels
- 2009
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Ingår i: 17th International Conference on Composite Materials, ICCM17. ; , s. 1-11
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Konferensbidrag (refereegranskat)abstract
- Controlled water slam testing of composite hull panels was conducted to study the effect of hydroelasticity for three panels with different stiffnesses. The experimental methodology successfully characterised the hydroelastic behaviour, which included kinematic as well as inertial effects. Hydroelastic effects included changes in panel geometry, local velocity, fluid pressures, and panel structural responses.
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| 4. |
- Battley, Mark, et al.
(författare)
-
Dynamic Characterization of Marine Sandwich Structures
- 2005
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Ingår i: 7th International Conference on Sandwich Structures. - Berlin/Heidelberg : Springer-Verlag. - 140203444X ; , s. 537-546
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Dynamic experimental and theoretical methods for sandwich panel structures subjected to water slamming are described, including a unique servo-hydraulic controlled slam test system and a pressure based transient finite element technique. The pressure simulation method accurately represents the pressures observed in slamming tests, and the transient dynamic finite element modelling can simulate sandwich panel responses to a slamming load.
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| 5. |
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| 6. |
- Bhat, Sriharsha, 1991-, et al.
(författare)
-
A Cyber-Physical System for Hydrobatic AUVs : System Integration and Field Demonstration
- 2020
-
Ingår i: 2020 IEEE/OES Autonomous Underwater Vehicles Symposium, AUV 2020. - : Institute of Electrical and Electronics Engineers (IEEE).
-
Konferensbidrag (refereegranskat)abstract
- Cyber-physical systems (CPSs) comprise a network of sensors and actuators that are integrated with a computing and communication core. Hydrobatic Autonomous Underwater Vehicles (AUVs) can be efficient and agile, offering new use cases in ocean production, environmental sensing and security. In this paper, a CPS concept for hydrobatic AUVs is validated in real-world field trials with the hydrobatic AUV SAM developed at the Swedish Maritime Robotics Center (SMaRC). We present system integration of hardware systems, software subsystems for mission planning using Neptus, mission execution using behavior trees, flight and trim control, navigation and dead reckoning. Together with the software systems, we show simulation environments in Simulink and Stonefish for virtual validation of the entire CPS. Extensive field validation of the different components of the CPS has been performed. Results of a field demonstration scenario involving the search and inspection of a submerged Mini Cooper using payload cameras on SAM in the Baltic Sea are presented. The full system including the mission planning interface, behavior tree, controllers, dead-reckoning and object detection algorithm is validated. The submerged target is successfully detected both in simulation and reality, and simulation tools show tight integration with target hardware.
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| 7. |
- Bhat, Sriharsha, et al.
(författare)
-
A Cyber-Physical System for Hydrobatic AUVs: System Integration and Field Demonstration
- 2020
-
Konferensbidrag (refereegranskat)abstract
- Cyber-physical systems (CPSs) comprise a network of sensors and actuators that are integrated with a computing and communication core. Hydrobatic Autonomous Underwater Vehicles (AUVs) can be efficient and agile, offering new use cases in ocean production, environmental sensing and security. In this paper, a CPS concept for hydrobatic AUVs is validated in real-world field trials with the hydrobatic AUV SAM developed at the Swedish Maritime Robotics Center (SMaRC). We present system integration of hardware systems, software subsystems for mission planning using Neptus, mission execution using behavior trees, flight and trim control, navigation and dead reckoning. Together with the software systems, we show simulation environments in Simulink and Stonefish for virtual validation of the entire CPS. Extensive field validation of the different components of the CPS has been performed. Results of a field demonstration scenario involving the search and inspection of a submerged Mini Cooper using payload cameras on SAM in the Baltic Sea are presented. The full system including the mission planning interface, behavior tree, controllers, dead-reckoning and object detection algorithm is validated. The submerged target is successfully detected both in simulation and reality, and simulation tools show tight integration with target hardware.
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| 8. |
- Bhat, Sriharsha, 1991-, et al.
(författare)
-
Controlling an Underactuated AUV as an Inverted Pendulum using Nonlinear Model Predictive Control and Behavior Trees
- 2023
-
Ingår i: Proceedings. - : Institute of Electrical and Electronics Engineers (IEEE).
-
Konferensbidrag (refereegranskat)abstract
- Agile and hydrobatic maneuvering capabilities can enhance AUV operations in increasingly challenging scenarios. In this paper, we explore the ability of an underactuated AUV to transition to and hold a pitch angle close to 90 degrees at a particular depth, like an inverted pendulum. Holding such an orientation can be valuable in observing a calving glacier, under-ice launch and recovery, underwater docking, inspecting vertical structures, and observing targets above the water surface. However, such control is challenging because of underactuation, rapid response times and varying stability in different configurations. To address this, a control policy is derived offline using nonlinear MPC in a high-fidelity simulation environment in Simulink. For real-time control, a hybrid controller using a behavior tree (BT) is developed based on the optimal MPC policy and applied on the AUV system. The BT controller considers Safety, Transit and Stabilize behaviors. The control algorithm is validated with simulations in Simulink and Stonefish-ROS as well as field experiments with the hydrobatic SAM AUV, showing repeatable performance in the inverted pendulum maneuver.
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| 9. |
- Bhat, Sriharsha, et al.
(författare)
-
Hydrobatics : A Review of Trends, Challenges and Opportunities for Efficient and Agile Underactuated AUVs
- 2018
-
Ingår i: AUV 2018 - 2018 IEEE/OES Autonomous Underwater Vehicle Workshop, Proceedings. - : Institute of Electrical and Electronics Engineers Inc.. - 9781728102535
-
Konferensbidrag (refereegranskat)abstract
- Hydrobatics refers to agile maneuvering of under-water vehicles just like aerobatics represents agile maneuvering of aerial vehicles. Performance trade-offs between flight and hover style autonomous underwater vehicles (AUVs) means that either maneuverability or range is compromised. Hydrobatic capabilities in flight style AUVs can bridge this gap and lead to more efficient and agile vehicles; thereby encouraging disruptive designs. As this is a relatively new area of research with very limited published research work, the focus of this paper is to present a multidisciplinary literature review to provide a path forward for further research. Relevant impact areas in ocean production, environmental sensing and security are discussed. Technical challenges are described in underactuated control and flight dynamics modeling. Synergies and opportunities are explored with aerospace engineering, robotics and artificial intelligence. As a part of this study, a simulation and verification framework is suggested and ongoing work is presented.
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| 10. |
- Bhat, Sriharsha, 1991-
(författare)
-
Hydrobatics: Efficient and Agile Underwater Robots
- 2020
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The term hydrobatics refers to the agile maneuvering of underwater vehicles. Hydrobatic capabilities in autonomous underwater vehicles (AUVs) can enable increased maneuverability without a sacrifice in efficiency and speed. This means innovative robot designs and new use case scenarios are possible. Benefits and technical challenges related to hydrobatic AUVs are explored in this thesis. The dissertation contributes to new knowledge in simulation, control and field applications, and provides a structured approach to realize hydrobatic capabilities in real world impact areas.Three impact areas are considered - environmental monitoring, ocean production and security. A combination of agility in maneuvering and efficiency in performance is crucial for successful AUV applications. To achieve such performance, two technical challenges must be solved. First, these AUVs have fewer control inputs than degrees of freedom, which leads to the challenge of underactuation. The challenge is described in detail and solution strategies that use optimal control and model predictive control (MPC) are highlighted. Second, the flow around an AUV during hydrobatic maneuvers transitions from laminar to turbulent flow at high angles of attack. This renders flight dynamics modelling difficult. A full 0-360 degree envelope flight dynamics model is therefore derived, which combines a multi-fidelity hydrodynamic database with a generalized component-buildup approach. Such a model enables real-time (or near real-time) simulations of hydrobatic maneuvers including loops, helices and tight turns.Next, a cyber-physical system (CPS) is presented -- it safely transforms capabilities derived in simulation to real-world use cases in the impact areas described. The simulator environment is closely integrated with the robotic system, enabling pre-validation of controllers and software before hardware deployment. The small and hydrobatic SAM AUV (developed in-house at KTH as part of the Swedish Maritime Robotics Center) is used as a test platform. The CPS concept is validated by using the SAM AUV for the search and detection of a submerged target in field operating conditions.Current research focuses on further exploring underactuated control and motion planning. This includes development of real-time nonlinear MPC implementations running on AUV hardware, as well as intelligent control through feedback motion planning, system identification and reinforcement learning. Such strategies can enable real-time robust and adaptive control of underactuated systems. These ideas will be applied to demonstrate new capabilities in the three impact areas.
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| 11. |
- Bhat, Sriharsha, 1991-
(författare)
-
Hydrobatics: Real-time Control, Simulation and Learning for Underactuated AUVs in Agile Maneuvers
- 2023
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The term hydrobatics refers to the agile maneuvering of underwater vehicles. Underwater robots such as autonomous underwater vehicles (AUVs) and remotely operated vehicles (ROVs) are either designed as flight style, optimized for range and speed, or hover style, optimized for precise maneuverability. Hydrobatic capabilities can help balance efficiency and maneuverability in these platforms, enabling innovative robot designs for impact areas in environmental monitoring, ocean production and security. This dissertation addresses technical challenges related to hydrobatic AUVs and contributes to new knowledge in real-time control, simulation, learning and planning. Hydrobatic AUVs are underactuated systems --- new strategies using nonlinear model predictive control (MPC) and behavior trees (BTs) are presented for efficient and safe real-time control of underactuated AUVs in agile maneuvers. Further, the flow around an AUV during such maneuvers transitions from laminar to turbulent flow at high angles of attack, rendering flight dynamics modelling difficult. A full 0-360 degree envelope flight dynamics model is therefore derived, which combines a multi-fidelity hydrodynamic database with a generalized component-buildup approach. Such a model enables real-time (or near real-time) simulations of hydrobatic maneuvers including loops, helices and tight turns. To increase the intelligence and robustness of such systems, data driven methods including physics-informed learning, Gaussian processes, sparse regression and reinforcement learning are utilized to rapidly identify models of the system's dynamics and perform online adaptive control. To further enhance autonomy, informative path planning is also studied, where an adaptive sampling strategy combines AUV measurements and satellite data to track ocean fronts.These hydrobatic capabilities are safely brought to the real world through a cyber-physical system (CPS). Simulator environments are closely integrated with the robotic system, enabling pre-validation of controllers and software before hardware deployment. The small and hydrobatic SAM AUV (SAM: Small and Affordable Maritime robot) developed in-house at KTH as part of the Swedish Maritime Robotics Centre (SMaRC) is used as a test platform. The CPS concept is demonstrated with the SAM AUV in applications including detecting underwater targets, inspecting seaweed farm infrastructure and tracking algal blooms using the presented simulation, planning and control strategies.
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| 12. |
- Bhat, Sriharsha, 1991-, et al.
(författare)
-
Nonlinear model predictive control for hydrobatics : Experiments with an underactuated AUV
- 2023
-
Ingår i: Journal of Field Robotics. - : Wiley. - 1556-4959 .- 1556-4967. ; 40:7, s. 1840-1859
-
Tidskriftsartikel (refereegranskat)abstract
- Hydrobatic autonomous underwater vehicles (AUVs) can be efficient in range and speed, as well as agile in maneuvering. They can be beneficial in scenarios such as obstacle avoidance, inspections, docking, and under-ice operations. However, such AUVs are underactuated systems—this means exploiting the system dynamics is key to achieving elegant hydrobatic maneuvers with minimum controls. This paper explores the use of model predictive control (MPC) techniques to control underactuated AUVs in hydrobatic maneuvers and presents new simulation and experimental results with the small and hydrobatic SAM AUV. Simulations are performed using nonlinear model predictive control (NMPC) on the full AUV system to provide optimal control policies for several hydrobatic maneuvers in Matlab/Simulink. For implementation on AUV hardware in robot operating system, a linear time varying MPC (LTV-MPC) is derived from the nonlinear model to enable real-time control. In simulations, NMPC and LTV-MPC shows promising results to offer much more efficient control strategies than what can be obtained with PID and linear quadratic regulator based controllers in terms of rise-time, overshoot, steady-state error, and robustness. The LTV-MPC shows satisfactory real-time performance in experimental validation. The paper further also demonstrates experimentally that LTV-MPC can be run real-time on the AUV in performing hydrobatic maneouvers.
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| 13. |
- Bhat, Sriharsha, 1991-, et al.
(författare)
-
Online Learning for Agile Underwater Maneuvering : Gaussian Processes and Sparse Regression for Data-driven Model Predictive Control
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Autonomous underwater vehicles (AUVs) show much promise in applications in environmental sensing, aquacultures, and security. Robust and adaptive control strategies can benefit these scenarios immensely by increasing the autonomy and en- durance. However, AUVs are nonlinear systems whose dynamics are challenging to model, and in several cases, also underactu- ated. Data-driven methods such as the Sparse Identification of Nonlinear Dynamics (SINDy), nonlinear least squares regression and Gaussian processes (GPs) can be beneficial to learn the AUV dynamics from measured data. Further, such data-driven models can be integrated into an adaptive model predictive control (MPC) scheme that drives the system to a setpoint while updating the prediction model when new measurements are available. This paper evaluates the performance of such data-driven methods for nonlinear system identification of two 6-DOF AUV systems, and implements them in an adaptive MPC scheme. Real experimental data from the SAM AUV and the MOLA AUV are used for performance evaluation.
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| 14. |
- Bhat, Sriharsha, 1991-, et al.
(författare)
-
Real-Time Flight Simulation of Hydrobatic AUVs Over the Full 0 degrees-360 degrees Envelope
- 2021
-
Ingår i: IEEE Journal of Oceanic Engineering. - : Institute of Electrical and Electronics Engineers (IEEE). - 0364-9059 .- 1558-1691. ; 46:4, s. 1114-1131
-
Tidskriftsartikel (refereegranskat)abstract
- Hydrobatic AUVsare very agile, and can perform challenging maneuvers that encompass the full 0 degrees-360 degrees flight envelope. Such AUVs can be beneficial in novel use cases in ocean production, environmental sensing, and security, by enabling new capabilities for docking, inspection, or under-ice operations. To further explore their capabilities in such scenarios, it is crucial to be able to model their flight dynamics over the full envelope, which includes strong nonlinear effects and turbulence at high angles of attack. With accurate and efficient simulation models, new hydrobatic maneuvers can be generated and control strategies can be developed. Therefore, this article contributes with a strategy to perform efficient and accurate simulations of hydrobatic maneuvers in real time. A multifidelity hydrodynamic database is synthesized by combining analytical, semiempirical, and numerical methods, thereby capturing fluid forces and moments over the full envelope. A component buildup workflow is used to assemble a nonlinear flight dynamics model using lookup tables generated from the database. This simulation model is used to perform real-time simulations of advanced hydrobatic maneuvers. Simulation results show agreement with literature and experiment, and the simulator shows utility as a development tool in designing new maneuvers and control strategies.
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| 15. |
- Bhat, Sriharsha, 1991-, et al.
(författare)
-
Real-time flight simulation of hydrobatic AUVs over the full 0 to 360 degree envelope
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Hydrobatic AUVs are very agile, and can perform challenging maneuvers that encompass the full 0-360° flight envelope. Such AUVs can be beneficial in novel use cases in ocean production, environmental sensing and security, by enabling new capabilities for docking, inspection or under-ice operations. In order to further explore their capabilities in such scenarios, it is crucial to be able to model their flight dynamics over the full envelope, which includes strong nonlinear effects and turbulence at high angles of attack. With accurate and efficient simulation models, new hydrobatic maneuvers can be generated and control strategies can be developed. This paper therefore contributes with a strategy to perform efficient and accurate simulations of hydrobatic maneuvers in real-time. A multi-fidelity hydrodynamic database is synthesized by combining analytical, semi-empirical and numerical methods, thereby capturing fluid forces and moments over the full envelope. A component buildup workflow is used to assemble a nonlinear flight dynamics model using look-up tables generated from the database. This simulation model is used to perform real-time simulations of advanced hydrobatic maneuvers. Simulation results show agreement with literature and experiment, and the simulator shows utility as a development tool in designing new maneuvers and control strategies.
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| 16. |
- Bhat, Sriharsha, et al.
(författare)
-
Towards a Cyber-Physical System for Hydrobatic AUVs
- 2019
-
Ingår i: OCEANS 2019 - Marseille.
-
Konferensbidrag (refereegranskat)abstract
- Cyber-physical systems (CPSs) encompass a network of sensors and actuators that are monitored, controlled and integrated by a computing and communication core. As autonomous underwater vehicles (AUVs) become more intelligent and connected, new use cases in ocean production, security and environmental monitoring become feasible. Swarms of small, affordable and hydrobatic AUVs can be beneficial in substance cloud tracking and algae farming, and a CPS linking the AUVs with multi-fidelity simulations can improve performance while reducing risks and costs. In this paper, we present a CPS concept tightly linking the AUV network in ROS to virtual validation using Simulink and Gazebo. A robust hardware-software interface using the open-source UAVCAN-ROS bridge is described for enabling hardware-in-the-loop validation. Hardware features of the hydrobatic SAM AUV are described, with a focus on subsystem integration. Results presented include pre-tuning of controllers, validation of mission plans in simulation and real time subsystem performance in tank tests. These first results demonstrate the interconnection between different system elements and offer a proof of concept.
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| 17. |
- Burman, Magnus, et al.
(författare)
-
Comparative Life Cycle Assessment of the hull of a high-speed craft
- 2016
-
Ingår i: Journal of Engineering for the Maritime Environment (Part M). - : Sage Publications. - 1475-0902 .- 2041-3084. ; 230:2, s. 378-387
-
Tidskriftsartikel (refereegranskat)abstract
- A comparative Life Cycle Assessment is performed for different structural material concepts on a 24-m-long high-speed patrol craft. The study is comparative and determines the differences in and sensitivities to environmental impact, especially in relation to the total impact of fuel burn for the different material concepts. The material concepts are aluminium and various composite combinations consisting of glass fibre and carbon fibre with vinyl ester resin both as single skins and as sandwich with a Divinycell foam core. Commercially available standard Life Cycle Assessment software is used for the Life Cycle Assessment calculations. The study shows that regardless of hull material concept, the environmental impact is dominated by the operational phase due to relatively large fuel consumption. In the operational phase, the lightest carbon-fibre concept is shown to have least environmental impact. Considering the manufacturing phase exclusively for the different hull concepts, it is concluded that the manufacturing of the aluminium hull has a somewhat larger environment impact for the majority of Life Cycle Assessment impact categories in comparison to the different composite hulls. The significant impact on the marine and the fresh water aquatic ecotoxicity originates from the aluminium raw material excavation and manufacturing processes. It is shown that the lightest hull, the carbon-fibre sandwich concept, with a 50% structural weight reduction compared to the aluminium design, can be utilized to reduce the fuel consumption by 20% (775 ton of diesel) over the lifetime with significant impact on the dominating environmental aspects considered herein, abiotic depletion, global warming and acidification.
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| 18. |
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| 19. |
- Chiche, Ariel, et al.
(författare)
-
Design of experiment to predict the time between hydrogen purges for an air-breathing PEM fuel cell in dead-end mode in a closed environment
- 2021
-
Ingår i: International journal of hydrogen energy. - : Elsevier BV. - 0360-3199 .- 1879-3487. ; 46:26, s. 13806-13817
-
Tidskriftsartikel (refereegranskat)abstract
- Fuel cells are promising technologies for zero-emission energy conversion. They are used in several applications such as power plants, cars and even submarines. Hydrogen supply is crucial for such systems and using Proton Exchange Membrane Fuel Cell in dead-end mode is a solution to save hydrogen. Since water and impurities accumulate inside the stack, purging is necessary. However, the importance of operating parameters is not well known for fuel cells working in closed environments. A Design of Experiment approach, studying time between two purges and cell performance, was conducted on an air-breathing stack in a closed environment. The most influential parameters on the time between two purges are the relative humidity and the current load. Convection in the closed environment can decrease the stability of the fuel cell. A linear model with interactions between these last three parameters was found to accurately describe the studied responses.
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| 20. |
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| 21. |
- Chiche, Ariel, et al.
(författare)
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Including Heat Balance When Designing the Energy System of Fuel Cell-Powered AUVs
- 2021
-
Ingår i: Energies. - : MDPI. - 1996-1073. ; 14:16, s. 4920-4920
-
Tidskriftsartikel (refereegranskat)abstract
- Fuel cell-powered Autonomous Underwater Vehicles (AUVs) represent a growing area of research as fuel cells can increase their endurance. Fuel cells consume hydrogen and oxygen to generate electricity. Typically, the fuel cell generates as much heat as electrical energy, and heat management becomes a crucial parameter when designing AUVs. For underwater applications, there is a need to store both gases and several types of storage units with different characteristics exist which have impacts on the energy density and heat behavior. This study aims at including the heat properties of the storage units in the design process of fuel cell-powered AUVs. A heat balance over the energy system of an AUV is calculated for each combination of hydrogen and oxygen storage units. In addition, a multi-criteria decision-making analysis is conducted, considering the calculated total heat, the specific energy, the energy density and the volumetric mass of each combination of storage units as criteria, enabling a comparison and ranking them using two objective criteria weighting methods. Results show that the fuel cell is the major contributor to the heat balance, and that the combinations of liquid oxygen with liquid or compressed hydrogen can be relevant and suitable for underwater applications.
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| 22. |
- Chiche, Ariel
(författare)
-
On Hybrid Fuel Cell and Battery Systems for Maritime Applications
- 2022
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Hydrogen is seen as a key player in leading to a sustainable energy sector and decarbonizing the transport sector. Proton Exchange Membrane Fuel Cells (PEMFCs) consume hydrogen and oxygen to generate water, heat and electricity. If designed properly, a hydrogen-fuelled system can significantly increase the endurance of vehicles without increasing the weight or volume of the energy system, which makes it a promising solution for maritime applications. To take advantage of the high density of energy in hydrogen and of power in batteries, a sizing strategy for hybrid systems was developed and implemented for an underwater vessel and a rescue boat, considering various constraints, e.g. neutral buoyancy for underwater vehicles. Several types of storage for reactants were compared and their thermal properties were included in the sizing strategy. To understand the behaviour of fuel cells in an underwater environment, i.e. a closed environment without presence of oxygen, an experimental lab-scale setup was built, and various hydrogen supply methods were tested. Finally, modelling of the hybrid system was used to compare different energy management strategies (EMSs). The developed sizing strategy, tested through real power profiles, demonstrates that an optimized hybrid system becomes more compact and lighter than a battery system when the length of the mission increases. Such a system can also compete in terms of weight and volume with a diesel engine and help reduce the environmental impact of a vehicle. The heat balance analysis shows that the fuel cell is the major heat contributor, regardless of the combination of reactants storage units. The experimental work highlights that the fuel cell should deliver a low current density at a high relative humidity in order to limit the waste of hydrogen and increase the performance of the stack. The symmetric purging strategy appears to increase the stability of the stack over time. It is also shown that it is crucial to select an adapted EMS for each mission in order to fulfil it. Some EMSs tend to limit the hydrogen consumption while others deplete more battery power. To conclude, it is relevant to use fuel cell systems for maritime applications, and has the potential to increase the length of the missions performed.
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| 23. |
- Chiche, Ariel, et al.
(författare)
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Sizing the energy system on long-range AUV
- 2018
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Ingår i: AUV 2018 - 2018 IEEE/OES Autonomous Underwater Vehicle Workshop, Proceedings. - : Institute of Electrical and Electronics Engineers Inc.. - 9781728102535
-
Konferensbidrag (refereegranskat)abstract
- Autonomous Underwater Vehicles (AUVs) can be used for various types of unmanned missions. Currently, the most common energy storage technique is rechargeable batteries. In order to increase the range and endurance of these vehicles, where volume is a limiting factor, fuel cell systems could offer a very attractive solution. Fuel cell systems can have a drastically increased specific energy compared to batteries and are now starting to become well developed technologies. However, in an underwater environment, both hydrogen and oxygen needs to be stored for the fuel cell. This study presents a sizing tool that compares the weight and volume to balance fuel cell and battery energy storage solutions for some selected AUV missions. The main result is the shifting point between batteries and hybrid battery/fuel cell system in terms of volume efficiency, where longer missions favor the latter.
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| 24. |
- Fonseca, Joana, et al.
(författare)
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Adaptive Sampling of Algal Blooms Using Autonomous Underwater Vehicle and Satellite Imagery : Experimental Validation in the Baltic Sea
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- This paper investigates using satellite data to improve adaptive sampling missions, particularly for front tracking scenarios such as with algal blooms. Our proposed solution to find and track algal bloom fronts uses an Autonomous Underwater Vehicle (AUV) equipped with a sensor that measures the concentration of chlorophyll a and satellite data. The proposed method learns the kernel parameters for a Gaussian process (GP) model using satellite images of chlorophyll a from the previous days. Then, using the data collected by the AUV, it models chlorophyll a concentration online. We take the gradient of this model to obtain the direction of the algal bloom front and feed it to our control algorithm. The performance of this method is evaluated through realistic simulations for an algal bloom front in the Baltic sea, using the models of the AUV and the chlorophyll a sensor. We compare the performance of different estimation methods, from GP to curve interpolation using least squares. Sensitivity analysis is performed to evaluate the impact of sensor noise on the methods’ performance. We implement our method on an AUV and run experiments in the Stockholm archipelago in the summer of 2022.
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| 25. |
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| 26. |
- Garme, Karl, et al.
(författare)
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Rough water performance of lightweight high-speed craft
- 2014
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Ingår i: Journal of Engineering for the Maritime Environment (Part M). - : SAGE Publications. - 1475-0902 .- 2041-3084. ; 228:3, s. 293-301
-
Tidskriftsartikel (refereegranskat)abstract
- Previous studies have shown how the use of composite materials and application of sophisticated design methods can give significantly lighter high-speed craft structures than what is normally achieved for traditional aluminium designs. A reduction in structural mass and a corresponding reduction in displacement improve the craft calm water performance but can be unfavourable regarding the rough water performance. Here, the rough water performance of two versions of a fast patrol vessel, one in aluminium and the other in carbon fibre sandwich, is studied with simplified semi-empirical methods and more advanced non-linear time domain simulations. In speeds up to 30 knots, the rough water performance of the two craft versions is found to be practically equal. At higher speeds, the lighter composite craft experiences higher vertical accelerations than the heavier aluminium craft, which implies less operational availability. Using trim ballast tanks, the rough water performance of the lighter craft is improved, and it is shown that the acceleration levels can be reduced and even lowered relative to the heavier aluminium craft. This means that the calm water advantages of a lighter composite vessel can be utilized with the same ride comfort and operational availability as for a heavier aluminium vessel.
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| 27. |
- Huldt, Tomas, et al.
(författare)
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State-of-practice survey of model-based systems engineering
- 2019
-
Ingår i: Systems Engineering. - : Wiley. - 1098-1241 .- 1520-6858. ; 22:2, s. 134-145
-
Tidskriftsartikel (refereegranskat)abstract
- This paper aims to examine and document the current state of practice of model-based systems engineering (MBSE), and how organizations look toward the future. The paper is based on a survey of how MBSE has been applied and factors that influenced the perceived benefits and results. The survey was designed to evaluate the maturity and status of the implementation of MBSE (also called model-centric systems engineering), within industry, academia, and governments. The approach to the survey development is described along with the survey results. The study indicates that one of the main hurdles to introducing a model-based approach is the lack of clear and adopted organizational structures and an understanding of required conditions and needs at a management level. The survey also indicates that 50-75% of the respondents noted some improvement or a significant improvement across almost all systems engineering tasks.
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| 28. |
- Marimon Giovannetti, Laura, et al.
(författare)
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Review of undewater fluid-structure interaction measuring techniques
- 2021
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Ingår i: 7th High Performance Yacht Design Conference, HPYD 2021. - : The Royal Institution of Naval Architects.
-
Konferensbidrag (refereegranskat)abstract
- This research aims to provide a feasibility study for an underwater Fluid Structure Interaction (FSI) experimental methodology. The possibility of measuring a structural deflection under fluid load and the flow behaviour around the structure is particularly interesting with the rise of composite materials, due to their inherent flexibility that permits them to be designed to a range of loading conditions. A review study on the experimental methodology available is carried out so that, in the future, a FSI measurement system can be installed in an underwater environment such as a towing tank or a marine basin. A robust and repeatable experimental methodology will also provide researchers with a validation case for numerical FSI simulations. The feasibility study starts with a thorough investigation of the existing measuring systems with an assessment of what could be used in SSPA Sweden underwater facilities (i.e. towing tank and marine dynamics laboratory). Currently there is a lack of FSI experimental methods, especially for underwater environment. The large majority of the current studies does not account for the complexity of the FSI coupled problems, where the structural response affects the flow behaviour and vice-versa. Bringing different techniques together will allow simultaneous measurements to be taken in a dynamic underwater environment. This would be especially important for performance prediction and numerical codes validations of foiling structures to assess the effects of deflections and twist when phenomena like cavitation and ventilation occur.
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| 29. |
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| 30. |
-
SMaRC Swedish Maritime Robotics Centre : Mid-Term Evaluation Report 2020
- 2020
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This is the midterm report of the project SMaRC (Swedish Maritime Robotics Centre), which is one of four industrial research centres (IRC) funded by the Swedish Foundation for Strategic Research (SSF). SMaRC is a unique collaborative research environment consisting of key industry, academia, and governmental partners in Sweden. The focus of the centre is to enable a transformational/disruptive shift towards the next generation of marine robots.The aim of this report is to describe how SMaRC will provide industrial outcomes that deliver into societal benefit areas, by linking user-defined scenarios with capabilities. This will strengthen the research focus as well as create a transparent mapping from scientific activities to end-user needs. The SMaRC project has now reached its midpoint and is running according to plan. The initial start-up process is now passed and key milestones of the project have been reached and demonstrated at the joint workshop and demonstration periods. SMaRC has already participated in very challenging Antarctic expeditions, developed and tested its own underwater robots, and demonstrated new capabilities for perception, navigation, endurance and autonomy in both simulator environments and in field experiments. For the upcoming second half of the project period, the focus will be on integration and demonstration to move closer to the industrial and end-user needs. The future research plan is connected to six targeted scenarios highlighting key capabilities to reach within the research projects. The demonstration of these scenarios also supports enhanced cooperation with both national and international partners.
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| 31. |
- Sprague, Christopher
(författare)
-
Efficient and Trustworthy Artificial Intelligence for Critical Robotic Systems
- 2022
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Critical robotic systems are systems whose functioning is critical to both ensuring the accomplishment of a given mission and preventing the endangerment of life and the surrounding environment. These critical aspects can be formally captured by convergence, in the sense that the system's state goes to a desired region of the statespace, and safety, in the sense that the system's state avoids unsafe regions of the statespace. Data-driven control policies, found through e.g. imitation learning or reinforcement learning, can outperform model-based methods in achieving convergence and safety efficiently; however, they often only do so by encouraging them, thus, they can be difficult to trust. Model-based control policies, on the other hand, are often well-suited to admitting formal guarantees of convergence and safety, thus they are often easier to trust. The main question asked in this thesis is: how can we compose data-driven and model-based control policies together to encourage efficiency while, at the same time, formally guaranteeing convergence and safety?We answer this question with behaviour trees, a framework to represent hybrid control systems in a modular way. We present the first formal definition of behaviour trees as a hybrid system and present the conditions under which the execution of any behaviour tree as a hybrid control system will formally guarantee convergence and safety. Moreover, we present the conditions under which such formal guarantees can be maintained when including unguaranteed data-driven control policies, such as those coming from imitation learning or reinforcement learning. We also present an approach to synthesise such data-driven control policies in such a way that they encourage convergence and safety by adapting to unforeseen events. Alongside the above, we also explore an ancillary aspect of robot autonomy by improving the efficiency of simultaneous localisation and mapping through imitation learning. Lastly, we validate the advantages of behaviour trees' modularity in a real-world autonomous underwater vehicle's control system, and argue that this modularity contributes to efficiency, in terms of ease of use, and trust, in terms of facilitating human understanding.
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| 32. |
- Stenius, Ivan, 1972-, et al.
(författare)
-
A system for autonomous seaweed farm inspection with an underwater robot
- 2022
-
Ingår i: Sensors. - : MDPI AG. - 1424-8220. ; 22:13
-
Tidskriftsartikel (refereegranskat)abstract
- This paper outlines challenges and opportunities in operating underwater robots (so-called AUVs) on a seaweed farm. The need is driven by an emerging aquaculture industry on the Swedish west coast where large-scale seaweed farms are being developed. In this paper, the operational challenges are described and key technologies in using autonomous systems as a core part of the operation are developed and demonstrated. The paper presents a system and methods for operating an AUV in the seaweed farm, including initial localization of the farm based on a prior estimate and dead-reckoning navigation, and the subsequent scanning of the entire farm. Critical data from sidescan sonars for algorithm development are collected from real environments at a test site in the ocean, and the results are demonstrated in a simulated seaweed farm setup.
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| 33. |
- Stenius, Ivan, et al.
(författare)
-
Experimental eigenfrequency study of dry and fully wetted rectangular composite and metallic plates by forced vibrations
- 2016
-
Ingår i: Ocean Engineering. - : Elsevier. - 0029-8018 .- 1873-5258. ; 111, s. 95-103
-
Tidskriftsartikel (refereegranskat)abstract
- This paper deals with the shortcomings in current design methods for dynamically loaded composite structures in underwater applications. This is done through an experimental study to evaluate the eigenfrequencies of rectangular plates made from metals as well as composites that are tested in air (dry) and completely submerged under water (fully wetted). The eigenfrequencies are studied using forced vibrations. The test series comprises 19 specimens that are made from various materials including aluminium, steel, glass-fibre, and carbon-fibre with aspect ratios varying from 3.7 to 11.2 and breadth to thickness ratios ranging from 2.7 to 20.5. The test method is based on electro-mechanical excitation by random vibrations as well as stepped sine refinements in the vicinity of the identified eigenfrequency. The results clearly show how differently the specimens are affected by the "added mass" from the water when fully wetted compared to the dry condition. Slender and more lightweight configurations are more profoundly affected by water than heavier and more rigid specimens. The results clearly show that for advanced composite materials and more complex geometries the current rule-of-thumb methods used by the industry today are inadequate in predicting the shift in natural frequency due to the effect of the surrounding water.
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| 34. |
- Stenius, Ivan, et al.
(författare)
-
Experimental hydroelastic characterization of slamming loaded marine panels
- 2013
-
Ingår i: Ocean Engineering. - : Elsevier BV. - 0029-8018 .- 1873-5258. ; 74, s. 1-15
-
Tidskriftsartikel (refereegranskat)abstract
- The paper presents a method to experimentally characterize the significance of hydroelasticity for slamming loaded marine panels. The methodology is based on a large number of systematical experiments of slamming loaded panels from which semi-empiric expressions for the pressure distributions are derived. Finite element simulations are used to obtain rigid/quasi-static reference solutions. Hydroelastic effects are quantified by comparing deflections and strains from experiments with the corresponding non-hydroelastic reference solutions. The study shows that the largest hydro-elastic effects appear to be a time-lag effect, which however does not seem to affect the structural response magnitudes dramatically. The most significant hydroelastic effects can be expected to be close to the panel supports for very flexible structures or sandwich constructions. The results are also discussed with reference to classification rules which indicate that hydroelastic effects are small in the design of conventional ship hull structures.
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| 35. |
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| 36. |
- Stenius, Ivan, et al.
(författare)
-
Explicit FE-modelling of fluid-structure interaction in hull-water impacts
- 2006
-
Ingår i: International Shipbuilding Progress. - 0020-868X .- 1566-2829. ; 53:2, s. 103-121
-
Tidskriftsartikel (refereegranskat)abstract
- The paper considers explicit FE-modelling of fluid-structure interaction in hull-water impacts. To minimize the variables studied and to enable comparison with analytical methods, the problem is here idealised as a two-dimensional rigid wedge impacting on a calm water surface. A parameter study is performed, where the sensitivity in the mesh resolution and the contact parameter selection is investigated. It is concluded that a numerically stable non-leaking solution to the hull-water impact problem, with good correlation to analytical results, is achievable. It is however also concluded that application of this modelling technique can be costly and far from trivial. The solution is for example highly dependent on the relation between mesh-density and contact-stiffness. Successful modelling hence requires rational approaches for determination of fluid discretization and contact parameters. By making reference to an analytical solution of the hull-water impact problem, the results from the parameter study are generalised, and a rational approach for determination of fluid discretization and contact parameters in the modelling of arbitrary hull-water impact situations is presented. The generality of the approach is favourably demonstrated for different impact angles and velocities.
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| 37. |
- Stenius, Ivan, et al.
(författare)
-
Explicit FE-modelling of hydroelasticity in panel-water impacts
- 2007
-
Ingår i: International Shipbuilding Progress. - 0020-868X .- 1566-2829. ; 54:2-3, s. 111-127
-
Tidskriftsartikel (refereegranskat)abstract
- This paper considers modelling of hydroelasticity in water impacts of ship-hull bottom-panels by use of explicit finite element methods. The finite element analysis is based on a multi-material arbitrary Lagrangian-Eulerian formulation and a penalty contact algorithm. This modelling technique enables the modelling of the instantaneous fluid-structure interaction. The FE-modelling of elastic panel-water impacts is evaluated by a convergence study and by comparison with experiments. Hydroelastic effects on the panel response are systematically studied for different impact velocities, boundary conditions and structural mass. It is concluded that hydroelastic effects can result in a significant reduction of the structural response for certain combinations of panel deadrise, impact velocity and boundary conditions. Inertia effects are shown to be dominated by added water mass. The present study is compared with other published work concerning hydroelasticity in panel-water impacts.
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| 38. |
- Stenius, Ivan, et al.
(författare)
-
FE-Modelling of Hydrodynamic Hull-Water Impact Loads
- 2007
-
Ingår i: Proceedings of The 6th European LS-DYNA Users' Conference.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This paper considers finite element modelling of the hydrodynamic loads in hull-waterimpacts. The commercial FE-code LS-DYNA is used with a multi-material arbitraryLagrangian-Eulerian formulation and a penalty contact algorithm. The great advantageof this modelling technique is that it enables the modelling of the instantaneous fluidstructureinteraction. A difficulty is however the selection of appropriate modellingparameters. A method to rationally select appropriate modelling parameters is discussedand briefly described. Convergence of the pressure distribution is presented anddiscussed. Pressure distributions and loads are favourably compared with othertheoretical methods and with experiments.
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| 39. |
- Stenius, Ivan
(författare)
-
Finite element modelling of hydroelasticity in hull-water impacts
- 2006
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The work in this thesis focuses on the use of explicit finite element analysis (FEA) in the modelling of fluid-structure interaction of panel-water impacts. Paper A, considers modelling of a two-dimensional rigid wedge impacting a calm water surface. From analytical methods and results of a systematic parameter study a generalised approach for determination of fluid discretization and contact parameters in the modelling of arbitrary hull-water impact situations is developed and presented. In paper B the finite element modelling methodology suggested in paper A is evaluated for elastic structures by a convergence study of structural response and hydrodynamic load. The structural hydroelastic response is systematically studied by a number of FE-simulations of different impact situations concerning panel deadrise, impact velocity and boundary conditions. In paper B a tentative method for dynamic characterization is also derived. The results are compared with other published results concerning hydroelasticity in panel water impacts. The long-term goal of this work is to develop design criteria, by which it can be determined whether the loading situation of a certain vessel type should be regarded as quasi-static or dynamic, and which consequence on the design a dynamic loading has.
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| 40. |
- Stenius, Ivan, et al.
(författare)
-
Hydroelastic Effects in Slamming Loaded Panels
- 2011
-
Ingår i: 11th International Conference on Fast Sea Transportation, FAST 2011 - Proceedings. - : American Society of Naval Engineers. ; , s. 644-652
-
Konferensbidrag (refereegranskat)abstract
- The paper discusses challenges in modeling and quantification of hydroelastic effects in panel-water impacts and summarizes results from numerical and experimental studies. Kinematic and inertia related hydroelastic effects are discussed and exemplified in relation to pressure distributions and structural responses. Hydroelastic effects are quantified by comparing hydroelastic results with rigid/ quasi-static reference results where the hydrodynamic loading is treated as unaffected by the structural deformation (rigid) and the structural response is treated as unaffected by structural inertia (quasi-static). The formulation of non-coupled reference solutions in experimental studies is particularly challenging and the paper addresses this problem by outlining a semi-empirical approach to reach such solutions. For those impact situations were the hydroelastic interaction seems to have a significant effect, it is found both numerically and experimentally that the hydroelastic effects are amplifying the structural responses in comparison to the rigid/quasi-static reference solutions. Two approaches for characterization of impact situations regarding the involved hydroelastic effects in relation to panel properties and impact conditions are discussed and exemplified. These approaches can tentatively be used to evaluate the hydroelastic effects in design situations.
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| 41. |
- Stenius, Ivan, et al.
(författare)
-
Hydroelastic interaction in panel-water impacts of high-speed craft
- 2011
-
Ingår i: Ocean Engineering. - : Elsevier BV. - 0029-8018 .- 1873-5258. ; 38:2-3, s. 371-381
-
Tidskriftsartikel (refereegranskat)abstract
- The paper considers the hydroelastic interaction involved in panel-water impacts for high-speed craft. Hydroelastic panel-water impacts are simulated by using the finite element code LS-DYNA and a simplified in-house developed method. The mechanisms involved are studied through a systematic series of simulations comprising different impact velocities, deadrise angles, boundary conditions, membrane effects, and panel properties. The terms inertial hydroelastic effects and kinematic hydroelastic effects are introduced to categorize the different mechanisms involved in the hydroelastic problem. It is shown that hydroelastic effects can both increase and reduce the panel responses depending on the impact envelope considered, and it is made clear that the impact envelope has to be carefully considered when establishing the significance of hydroelasticity in a hull-water impact problem. Membrane effects are shown to have large influences on the hydroelastic effects even for moderate panel deflections. The results generated are further used to evaluate and discuss hydroelastic criterion and methods for hydroelastic characterization.
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| 42. |
- Stenius, Ivan, et al.
(författare)
-
Hydroelasticity in Marine Hull Bottom Panels
- 2009
-
Tidskriftsartikel (refereegranskat)abstract
- The paper considers the hydroelastic interaction involved in panel- water impacts of high-speed craft. Hydroelastic panel-water impacts are simulated by using the finite element code LS-DYNA and a simplified in- house developed method. The mechanisms involved in the problem are stud- ied by a systematic series of simulations regarding different impact veloc- ities, deadirse angels, boundary conditions, membrane effects, and panel properties. The significance of hydroelasticity on the problem is studied by comparing with methods addressing the problem as completely separable and quasi-static. It is shown that membrane effects can have a large influ- ence on the hydroelastic problem. The results further show that, accounting for hydroelasticity may yield larger maximum deflections and strains com- pared to completely separated and quasi-static solutions. The increase in the structural response when accounting for hydroelasticity can partly be explained by kinematic boundary condition effects, and partly by inertia related added mass effects.
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| 43. |
- Stenius, Ivan, 1972-
(författare)
-
Hydroelasticity in Marine Hull Bottom Panels - Modeling and Characterization
- 2009
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The work in this thesis is concerned with the localized problem of hydroelasticity in marine panel-water impacts with an overall aim to increase the efficiency of high-speed craft by application of more refined methods in the structural design. The work mainly focuses on numerical modeling of the hydroelastic problem and therewith related aspects in the modeling and characterization of hydroelasticity. In addition, the work also addresses aspects regarding design methods of high-speed craft and experimental analysis of hydroelasticity. Two-dimensional panel-water impacts are simulated by using the commercial finite element code LS-DYNA. For the modeling of the panel-water impact situations a generalized approach for determination of fluid discretization and contact parameters is derived and extensively used throughout this work. The hydroelastic problem is studied through systematic series of numerical simulations regarding different impact situations. The work advances the understanding of the hydroelastic problem and introduces concepts such as kinematic and inertia related hydroelastic effects. The work further presents hydroelastic effects in contrast to previously published results, in the sense that it may not be conservative to ignore hydroelasticity in the structural design. This increase in the structural response when accounting for hydroelasticity can partly be related to kinematic effects, and partly to inertia related added mass effects. The results further show that, the effects of hydroelasticity increase with increased impact velocity, increased panel width, decreased deadrise angle, decreased panel flexural and in-plane stiffness, and decreased rotational and in-plane fixation at the boundaries. A tentative method is derived to characterize the hydroelastic problem, which, despite its simplicity and limitations, is found to successfully capture the complexity of the hydroelastic interaction in the design of the experimental setup. The experimental water slam testing of composite hull panels are conducted to study the effect of hydroelasticity for panels with different stiffnesses. The observed hydroelastic effects included changes in panel geometry, local velocity and hydrodynamic pressures. These effects also correlate with the observed hydroelastic effects from the numerical simulations.
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| 44. |
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| 45. |
- Stenius, Ivan, et al.
(författare)
-
On Structural Design of Energy Efficient Small High-Speed Craft
- 2011
-
Ingår i: Marine Structures. - : Elsevier BV. - 0951-8339 .- 1873-4170. ; 24:1, s. 43-59
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents an integrated design procedure for determination of structural arrangement and scantlings for the complete structure of small high-speed craft. The purpose of the procedure is to serve as a tool in the preliminary design stage where it enables generation of weight minimized designs with very limited effort. The design procedure is applied in a material concept study for a high-speed patrol craft. The various concepts include single skin and sandwich composites, aluminum and steel. It is demonstrated that the mass of the aluminum hull structure can be reduced from the original 11.7 tonnes to 9.6 tonnes through application of the presented design procedure. The most weight efficient material concept is a carbon-fiber foam-cored sandwich with a structural mass of 4.8 tonnes, which is about 50% less than the refined aluminum version. Through simple hydromechanic analysis, potential for fuel and CO2 emission reductions of 8% for the refined aluminum version and 27% for the carbon-fiber sandwich version in relation to the original craft are indicated.
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| 46. |
- Stenius, Ivan, 1972-, et al.
(författare)
-
Predicting the natural frequency of submerged structures using coupled solid-acoustic finite element simulations
- 2018
-
Ingår i: Ocean Engineering. - : Elsevier. - 0029-8018 .- 1873-5258. ; 159, s. 37-46
-
Tidskriftsartikel (refereegranskat)abstract
- This study concerns fluid-structure interaction analysis by using a solid-acoustic finite element model, letting an acoustic medium represent the fluid. This is a promising methodology to obtain computationally affordable advanced models of fluid structure interaction problems were the deformations can be assumed relatively small and the added mass effects dominate the dynamic characteristics. The work presents an extensive study of 19 plate specimens with material properties corresponding to carbon-fibre reinforced plastics, glass-fibre reinforced plastics, as well as steel and aluminium, and a range of different panel aspect ratios. In particular the effects of added mass on fibre-reinforced plastic materials are highlighted in comparison to how these typically are treated in the industry today. Based on a systematic isolation of the added mass effects, this paper enables a precise evaluation of the solid-acoustic FSI modelling approach. The modelling technique is also compared with previously published experiments. The results show good agreement (less than ∼±3% difference) between numerical and experimental results for the first natural frequency. The results indicate that this is a very promising modelling technique that can serve as a refined analysis method for design work performed within the maritime industry.
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| 47. |
- Stenius, Ivan, et al.
(författare)
-
Waterway 365 : System Analysis of Challenges in Increased Urban Mobility by Utilization of the Water Ways
- 2014
-
Rapport (populärvet., debatt m.m.)abstract
- Effective transport solutions for goods and people are crucial for the economic development of a region or city. In major cities worldwide there is a lack of capacity in the road and rail network resulting in high costs, only in Stockholm the cost of the overall shortcomings of commuting has been estimated to 6.3 billion SEK annually. The current trend is further increased congestions in major existing commut- ing routes (roads, rail networks and metro networks).In coastal cities like Stockholm, Gothenburg or Copenhagen however, there are inland waterways that would enable shorter and faster commuting routes if efficient land-sea based transportation systems are implemented. In addition the waterway constitutes an opportunity to create new city space, add transport capacity, offer new communication paths, change the transport flow and level off the pres- sure on the present transport system.The waterways and parts of the road network are existing infrastructure resources that may be used to contribute to more sustainable travel patterns, reduce congestion on main commuting corridors, in- crease capacity and the traffic system's resilience through new travel relationships, travel patterns and synergies with bicycle and city logistics.The aim of this work is to identify the most relevant research topics and key performance parameters for personal transport and city logistics systems on the waterways in urban environments for year- round service. The long-term goal is to identify transport systems and technical solutions for the wa- terways that can be scaled and adapted to urban environments around the world and that complement the land-based transport systems in order to achieve an over-all sustainable urban mobility.This work focuses on a systems engineering perspective and includes identification of system bounda- ries and interfaces to other public transport, infrastructure nodes, system service and maintenance and measurement of sustainability and service improvement targets. The aim is to develop a base for a system that can be scaled and adapted to urban environments around the world - like how road or rail- based mass transit systems today are built up from more or less standard units, not to design a public transport solution for a specific city, route or line. The focus is on realistic solutions that are both achievable from a cost perspective and attractive to passengers during 365 days a year. New concepts, ranging from small single person commuters up to large public transport systems, are to be explored and evaluated and key technical challenges identified and targeted.The research initiative Waterway 365 was initiated by The Royal Institute of Technology (KTH) and Vattenbussen AB with support from the Swedish Maritime Administration (Proj. no: 15041-0).
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| 48. |
- Tärnholm, Therese, 1975-
(författare)
-
Military innovation to build military capability, the case of uncrewed maritime systems
- 2023
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- For a military organisation capability is a central concept. The definitions vary with different nations and organizations, but here the military capability is defined as the ability of a sociotechnical system to solve military tasks performed under certain circumstances in a set environment. To create new or develop existing military capability, military innovation can be a crucial piece of the puzzle. It might be innovative systems solving tasks in the existing organization or existing technology used in an innovative manner.The aim of this thesis is to create a structure for discussing technology, innovation, and capability in a relevant way, where the capability lifecycle presents an overview of the desired capability when planning for future compositions of technology and units, instead of focusing on the individual systems. Therefore, this work is governed by a thematic aim that at least requires a multidisciplinary research approach which contains different research areas to understand how the technical systems can contribute within its context.To visualise this context, different aspects of the system is here divided into three layers. The technology level represents the technology itself, in this case Maritime Uncrewed Systems, which needs to be understood with its opportunities and limitations. The system also needs to be understood in its sociotechnical layer where the technical system is interacting with people, organization, and other units. The final layer is the governance layer with both the legal and ethical considerations in the use of the technology, in this case, an uncrewed system.The overall conclusion is that capability development is not doing things the same way as before with different technology. It is about trust in the overall system and developing how the available resources, both technical and sociotechnical, can contribute to solving a task as efficiently as possible in an altered organization.
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| 49. |
- Wozniak, Grzegorz, et al.
(författare)
-
Using Reinforcement Learning for Hydrobatic Maneuvering with Autonomous Underwater Vehicles
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Hydrobatic autonomous underwater vehicles (AUVs) can be efficient in speed and range as well as agile in maneuvering, thereby enabling new use cases in ocean production, environmental sensing, and security. However, such robots are underactuated, have highly nonlinear dynamics at high angles of attack, and will be used in applications with high requirements for robustness. This paper explores the use of reinforcement learning (RL) to control hydrobatic AUVs, using the agile SAM AUV as a case study. The focus is on controlling the depth and pitch simultaneously, where there is a tight coupling between the states. This maneuver offers a simple, yet interesting test case to compare different control strategies. The twin-delay deep deterministic policy gradient (TD3) algorithm is applied to this AUV control problem. The resulting trained RL controller offers good robustness to noise and performs at a similar level as a Proportional-Integral-Derivative (PID) controller within the Stonefish simulation environment. The agent is also deployed and run on the robot hardware, with high overshoot. While the RL agent has good performance in simulation, the transfer from simulation to reality still leaves some open questions.
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