Marine applications of the fast marching method

Path planning is general problem of mobile robots, which has special characteristics when applied to marine applications. In addition to avoid colliding with obstacles, in marine scenarios, environment conditions such as water currents or wind need to be taken into account in the path planning process. In this paper, several solutions based on the Fast Marching Method are proposed. The basic method focus on collision avoidance and optimal planning and, later on, using the same underlying method, the influence of marine currents in the optimal path planning is detailed. Finally, the application of these methods to consider marine robot formations is presented.The research leading to these results has received funding from HEROITEA-Sistema Inteligente Heterogéneo Multirobot para la Asistencia de Personas Mayores-RTI2018-095599-BC21 and from RoboCity2030-DIH-CM, Madrid Robotics Digital Innovation Hub, S2018/NMT-4331), funded by Programas de Actividades I+D en la Comunidad de Madrid and cofunded by Structural Funds of the EU

Fast marching subjected to a vector field-path planning method for mars rovers

Path planning is an essential tool for the robots that explore the surface of Mars or other celestial bodies such as dwarf planets, asteroids, or moons. These vehicles require expert and intelligent systems to adopt the best decisions in order to survive in a hostile environment. The planning module has to take into account multiple factors such as the obstacles, the slope of the terrain, the surface roughness, the type of ground (presence of sand), or the information uncertainty. This paper presents a path planning system for rovers based on an improved version of the Fast Marching (FM) method. Scalar and vectorial properties are considered when computing the potential field which is the basis of the proposed technique. Each position in the map of the environment has a cost value (potential) that is used to include different types of variables. The scalar properties can be introduced in a component of the cost function that can represent characteristics such as difficulty, slowness, viscosity, refraction index, or incertitude. The cost value can be computed in different ways depending on the information extracted from the surface and the sensor data of the rover. In this paper, the surface roughness, the slope of the terrain, and the changes in height have been chosen according to the available information. When the robot is navigating sandy terrain with a certain slope, there is a landslide that has to be considered and corrected in the path calculation. This landslide is similar to a lateral current or vector field in the direction of the negative gradient of the surface. Our technique is able to compensate this vector field by introducing the influence of this variable in the cost function. Because of this modification, the new method has been called Fast Marching (subjected to a) vector field (FMVF). Different experiments have been carried out in simulated and real maps to test the method performance.Publicad

An anisotropic fast marching method applied to path planning for Mars rovers

This paper presents the application of the Anisotropic Fast Marching Method to the path planning problem of mobile robots moving in outdoors environments, such as Mars. Considering that at any point on a 3D surface there are two main slopes: the maximum, which is the slope of the gradient, and the minimum, the height map of a terrain can be considered as a tensor filed. Using the Anisotropic Fast Marching Method, the resulting trajectory of the path planning takes the tensor field into account so that the slopes in the trajectory are minimized. Numerical simulations are presented to show the advantage of this method over its isotropic version. Besides, the influence of the anisotropic index and the traversability of the resultant paths are analyzed.This work was supported in part by the projects: "RoboCity2030-III-CM project (Robótica aplicada a la mejora de la calidad de vida de los ciudadanos. fase III; S2013/MIT-2748), in part by Programas de Actividades I+D en la Comunidad de Madrid and cofunded by Structural Funds of the EU" and in part by "Investigación para la mejora competitiva del ciclo de perforación y voladura en minería y obras subterráneas, mediante la concepción de nuevas técnicas de ingeniería, explosivos, prototipos y herramientas avanzadas (TUÑEL)"

Fast Marching-based globally stable motion learning

In this paper, a novel motion learning method is introduced: Fast Marching Learning (FML). While other learning methods are focused on optimising probabilistic functions or fitting dynamical systems, the proposed method consists on the modification of the Fast Marching Square (FM2) path planning algorithm. Concretely, FM2 consists of expanding a wave through the environment with a velocity directly proportional to the distance to the closest obstacle. FML modifies these velocities in order to generalise the taught motions and reproduce them. The result is a deterministic, asymptotically globally stable learning method free of spurious attractors and unpredictable behaviours. Along the paper, detailed analysis of the method, its properties and parameters are carried out. Comparison against a state-of-the-art method and experiments with real data is also included.This work is supported by the Spanish Ministry of Science and Innovation under the projects DPI2010-17772 and CSD2009-00067.Publicad

Fast methods for Eikonal equations: An experimental survey

Fast methods are very popular algorithms to compute time-of-arrival maps (distance maps measured in time units) solving the Eikonal equation. Since fast marching was proposed in 1995, it has been applied to many different applications, such as robotics, medical computer vision, fluid simulation, and so on. From then on, many alternatives to the original method have been proposed with two main objectives: reducing its computational time and improving its accuracy. In this paper, we collect the main single-threaded approaches, which improve the computational time of the standard fast marching method and study them within a common mathematical framework. Then, they are evaluated using isotropic environments, which are representative of their possible applications. The studied methods are the fast marching method with the binary heap, the fast marching method with Fibonacci heap, the simplified fast marching method, the untidy fast marching method, the fast iterative method, the group marching method, the fast sweeping method, the locking sweeping method, and the double dynamic queue method.This work is funded by the projects: "RoboCity2030-DIH-CM Madrid Robotics Digital Innovation Hub (Robtica aplicada a la mejora de la calidad de vida de los ciudadanos. Fase IV; S2018/NMT-4331), funded by Programas de Actividades I+D en la Comunidad de Madrid and cofunded by Structural Funds of the EU,'' and "Investigacion para la mejora competitiva del ciclo de perforacion y voladura en mineriai y obras subterraneas, mediante la concepcion de nuevas tecnicas de ingenieriai, explosivos, prototipos y herramientas avanzadas (TUNEL).'

Nonholonomic motion planning using the fast marching square method

This research presents two novel approaches to nonholonomic motion planning. The methodologies presented are based on the standard fast marching square path planning method and its application to car-like robots. Under the first method, the environment is considered as a three-dimensional C-space, with the first two dimensions given by the position of the robot and the third dimension by its orientation. This means that we operate over the configuration space instead of the bi-dimensional environment map. Moreover, the trajectory is computed along the C-space taking into account the dimensions of the vehicle, and thus guaranteeing the absence of collisions. The second method uses the standard fast marching square, and takes advantage of the vector field of the velocities computed during the first step of the method in order to adapt the motion plan to the control inputs that a car-like robot is able to execute. Both methods ensure the smoothness and safety of the calculated paths in addition to providing the control actions to perform the trajectory.This work is funded by project number DPI2010-17772, by the Spanish Ministry of Science and Innovation, and also by the RoboCity2030-II-CM project (S2009/DPI-1559), funded by Programas de Actividades I+D en la Comunidad de Madrid, and co-funded by the Structural Funds of the EU

3D robot formations path planning with fast marching square

This work presents a path planning algorithm for 3D robot formations based on the standard Fast Marching Square (FM2) path planning method. This method is enlarged in order to apply it to robot formations motion planning. The algorithm is based on a leader-followers scheme, which means that the reference pose for the follower robots is defined by geometric equations that place the goal pose of each follower as a function of the leader’s pose. Besides, the Frenet-Serret frame is used to control the orientation of the formation. The algorithm presented allows the formation to adapt its shape so that the obstacles are avoided. Additionally, an approach to model mobile obstacles in a 3D environment is described. This model modifies the information used by the FM2 algorithm in favour of the robots to be able to avoid obstacles. The shape deformation scheme allows to easily change the behaviour of the formation. Finally, simulations are performed in different scenarios and a quantitative analysis of the results has been carried out. The tests show that the proposed shape deformation method, in combination with the FM2 path planner, is robust enough to manage autonomous movements through an indoor 3D environment.Acknowledgments This work is funded by the project num ber DPI2010-17772, by the Spanish Ministry of Science and Innovation, and also by RoboCity2030-II-CM project (S2009/DPI-1559), funded by Programas de Actividades I+D en la Comunidad de Madrid and co-funded by Structural Funds of the EU.Publicad

Psychometric properties of a Spanish version of the MM-CGI-SF in caregivers of people with dementia

Background: Caregivers of people with dementia may experience characteristic grief linked to present and anticipated losses before the physical death of the care recipient occurs, which is related to physical and mental health problems. The Marwit-Meuser Caregiver Inventory-Short Form (MM-CGI-SF) is an instrument that assesses this type of grief. Since there are no studies on an adaptation of the MM-CGI-SF to the Spanish population, the aim of the study was to evaluate its psychometric properties in a sample of caregivers of dementia patients. Methods: A cross-sectional study was carried out. The tool was translated and adapted into Spanish, which was administered to 250 caregivers of people with dementia in the province of Huelva, together with other related instruments. Descriptive statistics and internal consistency reliability were calculated using Cronbach's alpha, for the total questionnaire and for each subscale. A confirmatory factor analysis (CFA) was performed and the Spanish version of the MM-CGI-SF was correlated with the rest of the variables by calculating Spearman's correlation coefficient. Results: 80.4% of the participants were female and had high levels of caregiver grief (x = 64.62, SD = 14.86). Cronbach's alpha for the general questionnaire was 0.927 and between 0.822-0.854 for its subscales. The fit values of the CFA were: x2 = 202.033, degrees of freedom = 121, x2 /df = 1.670, TLI = 0.954, CFI = 0.963, SRMR = 0.047, RMSEA = 0.052; and all the correlations were statistically significant. Conclusions: The Spanish version of the MM-CGI-SF shows adequate psychometric properties. Thanks to this instrument, health professionals may measure caregiver grief, get closer to the reality of dementia care, and evaluate the effectiveness of interventions to manage this grief.The Spanish Ministry of Universities has supported the first author of this research through the University Teacher Training Programme, with reference number (FPU19/04001). Funding for open access charge: Universidad de Huelva/CBUA

Intrinsic anomalous surface roughening of TiN films deposited by reactive sputtering

7 pages, 7 figures.-- PACS nrs.: 68.55.−a, 81.15.Cd, 81.15.Aa, 68.35.Ct.Final publisher version available Open Access at: http://gisc.uc3m.es/~cuerno/publ_list.htmlWe study surface kinetic roughening of TiN films grown on Si(100) substrates by dc reactive sputtering. The surface morphology of films deposited for different growth times under the same experimental conditions were analyzed by atomic force microscopy. The TiN films exhibit intrinsic anomalous scaling and multiscaling. The film kinetic roughening is characterized by a set of local exponent values α(loc)=1.0 and β(loc)=0.39, and global exponent values α=1.7 and β=0.67, with a coarsening exponent of 1/z=0.39. These properties are correlated to the local height-difference distribution function obeying power-law statistics. We associate this intrinsic anomalous scaling with the instability due to nonlocal shadowing effects that take place during thin-film growth by sputtering.Financial support is acknowledged from Spanish MCyT Grants No. MAT 2002-04037-C03-03 and No. BFM 2003-07749-C05-01, -02, and -05; Comunidad Autónoma de Madrid, Grant No. GR/MAT/0431/2004, European Community Grant No. G5RD-CT-2000-00333, Centre of Excellence CE PI SAS, Contract No. I/2/2005, and Slovak Grant Agency for Science VEGA, Grant No. 2/6030/26.Publicad

Influence of special tool geometry in drilling woven CFRPs materials

Machining processes of Carbon Fiber Reinforced Polymer (CFRP) are commonly required in order to achieve final assembly specifications. Despite the good mechanical properties of this kind of materials, they are hard to be machined due to the presence of hard particles; delamination, fiber pull-out and matrix thermal degradation are usually observed during its machining. Drilling operations are required before mechanical joining of the CFRP components. The actual interest in reducing delamination rests in the fact that it is the most serious damage found during drilling. In this work, a comparative study of three special geometries under different cutting conditions is presented. Thrust force and torque were monitoring during drilling tests and delamination extension was quantified. Results showed that a good drill tip geometry and feed rate selection is fundamental to reduce delamination damages.The funding received from the Ministry of Economy and Competitiveness of Spain under the project DPI2011-25999 and FPI subprogram with the reference BES-2012-055162 is highly appreciated