Marine Autonomous Exploration Using a Lidar and SLAM

Ueland, Einar Skiftestad; Skjetne, Roger; Dahl, Andreas Reason

doi:10.1115/omae2017-61880

Cited by 12 publications

(6 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…As a result, only the channels connecting NCC to the epiphyseal compartment of the tibia were used in the analyses. TMR was calculated as an average roughness from 600 slices from the VOI by finding the shortest route through an automatically segmented surface using an A-star search algorithm (v1.0) 40 and fitting a simple linear regression to each route. The generated regression lines were used as reference lengths for each shortest route through the tidemark surface.…”

Section: Mct Data Analysismentioning

confidence: 99%

3D morphometric analysis of calcified cartilage properties using micro-computed tomography

Kauppinen

Karhula

Thevenot

et al. 2019

Osteoarthritis and Cartilage

View full text Add to dashboard Cite

s u m m a r yObjective: Our aim is to establish methods for quantifying morphometric properties of calcified cartilage (CC) from micro-computed tomography (mCT). Furthermore, we evaluated the feasibility of these methods in investigating relationships between osteoarthritis (OA), tidemark surface morphology and open subchondral channels (OSCCs). Method: Samples (n ¼ 15) used in this study were harvested from human lateral tibial plateau (n ¼ 8). Conventional roughness and parameters assessing local 3-dimensional (3D) surface variations were used to quantify the surface morphology of the CC. Subchondral channel properties (percentage, density, size) were also calculated. As a reference, histological sections were evaluated using Histopathological osteoarthritis grading (OARSI) and thickness of CC and subchondral bone (SCB) was quantified. Results: OARSI grade correlated with a decrease in local 3D variations of the tidemark surface (amount of different surface patterns (r s ¼ À0.600, P ¼ 0.018), entropy of patterns (EP) (r s ¼ À0.648, P ¼ 0.018), homogeneity index (HI) (r s ¼ 0.555, P ¼ 0.032)) and tidemark roughness (TMR) (r s ¼ À0.579, P ¼ 0.024). Amount of different patterns (ADP) and EP associated with channel area fraction (CAF) (r p ¼ 0.876, P < 0.0001; r p ¼ 0.665, P ¼ 0.007, respectively) and channel density (CD) (r p ¼ 0.680, P ¼ 0.011; r p ¼ 0.582, P ¼ 0.023, respectively). TMR was associated with CAF (r p ¼ 0.926, P < 0.0001) and average channel size (r p ¼ 0.574, P ¼ 0.025). CC topography differed statistically significantly in early OA vs healthy samples. Conclusion:We introduced a m-CT image method to quantify 3D CC topography and perforations through CC. CC topography was associated with OARSI grade and OSCC properties; this suggests that the established methods can detect topographical changes in tidemark and CC perforations associated with OA.

show abstract

Section: Mct Data Analysismentioning

confidence: 99%

3D morphometric analysis of calcified cartilage properties using micro-computed tomography

Kauppinen

Karhula

Thevenot

et al. 2019

Osteoarthritis and Cartilage

View full text Add to dashboard Cite

show abstract

“…The start and end points of the planned trajectory inside the ROI are fixed and cannot be altered during this phase. Using the A* algorithm implemented in the project presented in Ueland et al (2017), three paths were planned: from the unloading zone to a ROI, from this ROI to the next ROI, and from this last ROI back to the unloading zone. The sums of the path lengths are evaluated to select the lowest value.…”

Section: Resultsmentioning

confidence: 99%

An automated heterogeneous robotic system for radiation surveys: Design and field testing

Gábrlík

Lázna

Jílek

et al. 2021

Journal of Field Robotics

View full text Add to dashboard Cite

During missions involving radiation exposure, unmanned robotic platforms may embody a valuable tool, especially thanks to their capability of replacing human operators in certain tasks to eliminate the health risks associated with such an environment. Moreover, rapid development of the technology allows us to increase the automation rate, making the human operator generally less important within the entire process. This article presents a multirobotic system designed for highly automated radiation mapping and source localization. Our approach includes a three‐phase procedure comprising sequential deployment of two diverse platforms, namely, an unmanned aircraft system (UAS) and an unmanned ground vehicle (UGV), to perform aerial photogrammetry, aerial radiation mapping, and terrestrial radiation mapping. The central idea is to produce a sparse dose rate map of the entire study site via the UAS and, subsequently, to perform detailed UGV‐based mapping in limited radiation‐contaminated regions. To accomplish these tasks, we designed numerous methods and data processing algorithms to facilitate, for example, digital elevation model‐based terrain following for the UAS, automatic selection of the regions of interest, obstacle map‐based UGV trajectory planning, and source localization. The overall usability of the multirobotic system was demonstrated by means of a 1‐day, authentic experiment, namely, a fictitious car accident including the loss of several radiation sources. The ability of the system to localize radiation hotspots and individual sources has been verified.

show abstract

“…Images were binarised setting a threshold equal to the roughness height λ. Then, an A * path detection algorithm from a starting node SN to a target node TN was implemented 32 . The basic principles of the code are resumed by the schematic in Fig.…”

Section: A Randomly Distributed Roughness Elementsmentioning

confidence: 99%

Prediction of resistance induced by surface complexity in lubricating layers: Application to super-hydrophobic surfaces

Bettaieb¹,

Castagana²,

Passaggia³

et al. 2022

Preprint

View full text Add to dashboard Cite

Super Hydrophobic (SH) coatings are widely used to mitigate drag in various applications. Numerous studies have demonstrated that the beneficial wall-slip effect produced by these materials disappears in laminar flow regimes. The main mechanisms considered to be behind the decrease in performance are Marangoni-induced stresses and air/liquid interface deformation. In the present study, a new mechanism is proposed to explain the loss of performances of SH-surfaces in laminar flow regimes. Here we consider the flow of air inside the plastron and the associated momentum loses induced by roughness elements with different geometric characteristics. The effects of air motion within the plastron is coupled to the outer fluid with a homogenised boundary condition approach. To this end, numerical simulations at the scale of the roughness element were conducted as a function of the porosity and the tortuosity of the domain to determine the slip velocity at the air-liquid interface. The homogenised boundary condition is then implemented in a theoretical model for the outer flow to compute drag on SH-spheres at low Re numbers. Experiments of laminar SH falling spheres indicate that high values of the tortuosity and low values of porosity lead to a loss of performances when considering drag reduction. As anticipated, a 3D printed sphere with low tortuosity and similar porosity demonstrated near-optimal drag reductions. A comparative study between the predicted values and experiments shows that the homogenised model is able to accurately predict the drag on SH surfaces for values of the porosity and tortuosity estimated from microscopy images of the SH textured surface.

show abstract

Marine Autonomous Exploration Using a Lidar and SLAM

Cited by 12 publications

References 0 publications

3D morphometric analysis of calcified cartilage properties using micro-computed tomography

3D morphometric analysis of calcified cartilage properties using micro-computed tomography

An automated heterogeneous robotic system for radiation surveys: Design and field testing

Prediction of resistance induced by surface complexity in lubricating layers: Application to super-hydrophobic surfaces

Contact Info

Product

Resources

About