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| 2. |
- Allen, T., et al.
(författare)
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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
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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)
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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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| 6. |
- Bhat, Sriharsha, 1991-, et al.
(författare)
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A Cyber-Physical System for Hydrobatic AUVs : System Integration and Field Demonstration
- 2020
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Ingår i: 2020 IEEE/OES Autonomous Underwater Vehicles Symposium, AUV 2020. - : Institute of Electrical and Electronics Engineers (IEEE).
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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)
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A Cyber-Physical System for Hydrobatic AUVs: System Integration and Field Demonstration
- 2020
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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)
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Controlling an Underactuated AUV as an Inverted Pendulum using Nonlinear Model Predictive Control and Behavior Trees
- 2023
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Ingår i: Proceedings. - : Institute of Electrical and Electronics Engineers (IEEE).
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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)
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Hydrobatics : A Review of Trends, Challenges and Opportunities for Efficient and Agile Underactuated AUVs
- 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
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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)
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Hydrobatics: Efficient and Agile Underwater Robots
- 2020
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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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