| 1. |
- Bhat, Sriharsha, 1991-, et al.
(författare)
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Real-Time Flight Simulation of Hydrobatic AUVs Over the Full 0 degrees-360 degrees Envelope
- 2021
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Ingår i: IEEE Journal of Oceanic Engineering. - : Institute of Electrical and Electronics Engineers (IEEE). - 0364-9059 .- 1558-1691. ; 46:4, s. 1114-1131
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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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| 2. |
- Bishop, Adrian N., et al.
(författare)
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Optimal Range-Difference-Based Localization Considering Geometrical Constraints
- 2008
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Ingår i: IEEE Journal of Oceanic Engineering. - 0364-9059 .- 1558-1691. ; 33:3, s. 289-301
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Tidskriftsartikel (refereegranskat)abstract
- This paper proposes a new type of algorithm aimed at finding the traditional maximum-likelihood (TML) estimate of the position of a target given time-difference-of-arrival (TDOA) information, contaminated by noise. The novelty lies in the fact that a performance index, akin to but not identical with that in maximum likelihood (ML), is a minimized subject to a number of constraints, which flow from geometric constraints inherent in the underlying problem. The minimization is in a higher dimensional space than for TML, and has the advantage that the algorithm can be very straightforwardly and systematically initialized. Simulation evidence shows that failure to converge to a solution of the localization problem near the true value is less likely to occur with this new algorithm than with TML. This makes it attractive to use in adverse geometric situations.
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| 3. |
- Bore, Nils, et al.
(författare)
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Modeling and Simulation of Sidescan Using Conditional Generative Adversarial Network
- 2020
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Ingår i: IEEE Journal of Oceanic Engineering. - : IEEE Oceanic Engineering Society. - 0364-9059 .- 1558-1691. ; , s. 1-11
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Tidskriftsartikel (refereegranskat)abstract
- Sidescan sonar has been used for maritime surveys since the mid-20th century. Due to its wide swath coverage and the sharpness of the produced images, it is an invaluable tool still to this day. When simulating sidescan data, there is a tradeoff between the quality of the produced images, the fidelity of the environment simulation, and the complexity of the sidescan model. In this article, we propose data-driven models as a way of removing some of this tradeoff. Using recently proposed conditional generative adversarial nets, we create a generative model that takes the environment as input, and produces realistic sidescan measurements. We show that end-to-end learning of flexible models allows simulating more complex sidescan data than would otherwise be possible given only geometric bathymetry.
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| 4. |
- Bore, Nils, et al.
(författare)
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Neural Shape-From-Shading for Survey-Scale Self-Consistent Bathymetry From Sidescan
- 2023
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Ingår i: IEEE Journal of Oceanic Engineering. - : Institute of Electrical and Electronics Engineers (IEEE). - 0364-9059 .- 1558-1691. ; 48:2, s. 416-430
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Tidskriftsartikel (refereegranskat)abstract
- Sidescan sonar is a small and cost-effective sensing solution that can be easily mounted on most vessels. Historically, it has been used to produce high-definition acoustical images that experts may use to identify targets on the seafloor or in the water column. While solutions have been proposed to produce bathymetry solely from sidescan, or in conjunction with multibeam, they have had limited impact. This is partly a result of mostly being limited to single survey lines. In this article, we propose a modern, scalable solution to create high quality survey-scale bathymetry from many sidescan survey lines. By incorporating multiple observations of the same place, results can be improved as the estimates reinforce each other. Our method is based on sinusoidal representation networks, a recent advance in neural representation learning. We demonstrate the scalability of the approach by producing bathymetry from a large sidescan survey. The resulting quality is demonstrated by comparing to data collected with a high-precision multibeam sensor.
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| 5. |
- Boström, Cecilia, et al.
(författare)
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Linear Generator Connected to a Resonance-Rectifier Circuit
- 2013
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Ingår i: IEEE Journal of Oceanic Engineering. - 0364-9059 .- 1558-1691. ; 38:2, s. 255-262
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes a linear direct driven generator used for wave energy utilization. The generator is placed on the seabed and connected to a buoy on the ocean surface. Due to the reciprocating motion of the translator, an electrical conversion system is needed between the wave energy converter (WEC) and the grid. Depending on how the conversion system is designed, the generator will be subjected to different loads. A novel conversion system is presented in this paper where the voltage from the WEC is rectified in a resonance circuit. Both simulations and experiments are performed on the circuit. The results from the simulations show that a higher power absorption and power production can be achieved with the resonance circuit compared to a WEC connected to a passive rectifier. A WEC, L9, developed by Uppsala University (Uppsala, Sweden) was used in the experiment. Significantly higher power absorption was obtained for L9 compared to power data from the first installed WEC, L1, at the Lysekil research site.
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| 6. |
- Boström, Cecilia, et al.
(författare)
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Study of aWave Energy Converter Connected to a Nonlinear Load
- 2009
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Ingår i: IEEE Journal of Oceanic Engineering. - 0364-9059 .- 1558-1691. ; 34:2, s. 123-127
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents experimental results from a wave energy converter (WEC) that is based on a linear generator connected to a rectifier and filter components. The converter-filter system is installed onshore, while the linear wave generator operates offshore a few kilometers from the Swedish west coast. The power from the generator has been rectified with a diode bridge and then filtered using a capacitive filter. Performance of the whole conversion system was studied using resistive loads connected across the filter. The aim was to investigate the operational characteristics of the generator while supplying a nonlinear load. By changing the value of the resistive component of the load, the speed of the translator can be changed and so also the damping of the generator. The power absorbed by the generator was studied at different sea states as well. The observations presented in this paper could be beneficial for the design of efficient wave energy conversion systems.
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| 7. |
- Castellucci, Valeria, et al.
(författare)
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Influence of Sea State and Tidal Height on Wave Power Absorption
- 2017
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Ingår i: IEEE Journal of Oceanic Engineering. - 0364-9059 .- 1558-1691. ; 42:3, s. 566-573
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Tidskriftsartikel (refereegranskat)abstract
- The wave energy converter developed at Uppsala University (Uppsala, Sweden) consists of a linear generator placed on the seabed and driven by the motion of a buoy on the water surface. The buoy is connected to the moving part of the linear generator, the translator, which is made of ferrite magnets. The translator moves vertically inducing voltage in the windings of a fixed component, the so-called stator. The energy conversion of the linear generator is affected by the sea state and by variations of mean sea level. The sea state influences the speed and the stroke length of the translator, while the variation of tidal level shifts the average position of the translator with respect to the center of the stator. The aim of this study is to evaluate the energy absorption of the wave energy converter at different locations around the world. This goal is achieved by developing a hydromechanic model which analyses the optimum generator damping factor for different wave climates and the power absorbed by the generator, given a fixed geometry of the buoy and a fixed stroke length of the translator. Economic considerations regarding the optimization of the damping factor are included within the paper. The results suggest a nominal damping factor and show the power absorption losses at various locations, each of them characterized by a different wave climate and tidal range. The power losses reach up to 67% and in many locations a tidal compensation system, included in the design of the wave energy converter, is strongly motivated.
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| 8. |
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| 9. |
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| 10. |
- Engström, Jens, et al.
(författare)
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Properties of the Energy Transport for Plane-Parallel Polychromatic Surface Gravity Waves in Waters of Arbitrary Depth
- 2015
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Ingår i: IEEE Journal of Oceanic Engineering. - 0364-9059 .- 1558-1691. ; 40:2, s. 408-416
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Tidskriftsartikel (refereegranskat)abstract
- It is well known that the energy transport of ocean waves propagates with the group velocity and that the energy decreases exponentially with depth. Expanding this theory, we will derive expressions for the energy transport as a function of depth and the total instantaneous transport's development over time for waves in waters of finite depth. Solutions to the Laplace equation are found for plane-parallel polychromatic waves with linearized boundary conditions. A time series of wave elevation collected at Uppsala University's wave energy research test site is chosen to present the results. Solutions for waters of both infinite and arbitrary depths are presented and compared. The solutions are convolution-type integrals with the wave elevation where we have found efficient ways to calculate the kernels. The difference in group velocity between finite depth and infinite depth and its impact on the energy transport is clearly seen in the results. The use of the deep-water approximation gives a too low energy transport in the time averaged as well as in the total instantaneous energy transport. We further show that the total instantaneous energy transport can actually have a direction that is opposite to the direction of the waves as observed from a reference frame fixed to the seabed.
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