A waypoint-based mission planner for a farmland coverage with an aerial robot - a precision farming tool

Remote sensing (RS) with aerial robots is becoming more usual in every day time in Precision Agriculture (PA) practices, do to their advantages over conventional methods. Usually, available commercial platforms providing off-the-shelf waypoint navigation are adopted to perform visual surveys over crop fields, with the purpose to acquire specific image samples. The way in which a waypoint list is computed and dispatched to the aerial robot when mapping non empty agricultural workspaces has not been yet discussed. In this paper we propose an offline mission planner approach that computes an efficient coverage path subject to some constraints by decomposing the environment approximately into cells. Therefore, the aim of this work is contributing with a feasible waypoints-based tool to support PA practices

Atmospheric attenuation at 100 and 300 GHz estimated with radiosonde data

The study of atmospheric propagation impairments at submillimeter and THz frequencies is becoming increasingly relevant due to the strong effects caused by the composition of the troposphere and the phenomena occurring in it. The present paper is devoted to the estimation of total attenuation at 100 GHz and 300 GHz under non-rainy scenarios. With this purpose, 4 years of meteorological data from Madrid have been collected, including radiosoundings from Madrid-Barajas Airport and co-site SYNOP observations. This volume of data has been analyzed with the aim of also introducing a detection method of rain conditions, which cannot be easily identified in radiosounding profiles. Finally, the method has been used to discard several probable events which would be responsible of scattering conditions and, hence, yearly CDFs of total attenuation have been obtained. It is expected that the statistics would be closest to the ones obtained by experimental techniques under similar atmospheric conditions.

Towards the automatic generation of card games through Grammar-Guided Genetic Programming

We demonstrate generating complete and playable card games using evolutionary algorithms. Card games are represented in a previously devised card game description language, a context-free grammar. The syntax of this language allows us to use grammar-guided genetic programming. Candidate card games are evaluated through a cascading evaluation function, a multi-step process where games with undesired properties are progressively weeded out. Three representa- tive examples of generated games are analysed. We observed that these games are reasonably balanced and have skill ele- ments, they are not yet entertaining for human players. The particular shortcomings of the examples are discussed in re- gard to the generative process to be able to generate quality games

Dynamic analysis of payloads and structures with intermediate modal density

La necesidad de desarrollar técnicas para predecir la respuesta vibroacústica de estructuras espaciales lia ido ganando importancia en los últimos años. Las técnicas numéricas existentes en la actualidad son capaces de predecir de forma fiable el comportamiento vibroacústico de sistemas con altas o bajas densidades modales. Sin embargo, ambos rangos no siempre solapan lo que hace que sea necesario el desarrollo de métodos específicos para este rango, conocido como densidad modal media. Es en este rango, conocido también como media frecuencia, donde se centra la presente Tesis doctoral, debido a la carencia de métodos específicos para el cálculo de la respuesta vibroacústica. Para las estructuras estudiadas en este trabajo, los mencionados rangos de baja y alta densidad modal se corresponden, en general, con los rangos de baja y alta frecuencia, respectivamente. Los métodos numéricos que permiten obtener la respuesta vibroacústica para estos rangos de frecuencia están bien especificados. Para el rango de baja frecuencia se emplean técnicas deterministas, como el método de los Elementos Finitos, mientras que, para el rango de alta frecuencia las técnicas estadísticas son más utilizadas, como el Análisis Estadístico de la Energía. En el rango de medias frecuencias ninguno de estos métodos numéricos puede ser usado con suficiente precisión y, como consecuencia -a falta de propuestas más específicas- se han desarrollado métodos híbridos que combinan el uso de métodos de baja y alta frecuencia, intentando que cada uno supla las deficiencias del otro en este rango medio. Este trabajo propone dos soluciones diferentes para resolver el problema de la media frecuencia. El primero de ellos, denominado SHFL (del inglés Subsystem based High Frequency Limit procedure), propone un procedimiento multihíbrido en el cuál cada subestructura del sistema completo se modela empleando una técnica numérica diferente, dependiendo del rango de frecuencias de estudio. Con este propósito se introduce el concepto de límite de alta frecuencia de una subestructura, que marca el límite a partir del cual dicha subestructura tiene una densidad modal lo suficientemente alta como para ser modelada utilizando Análisis Estadístico de la Energía. Si la frecuencia de análisis es menor que el límite de alta frecuencia de la subestructura, ésta se modela utilizando Elementos Finitos. Mediante este método, el rango de media frecuencia se puede definir de una forma precisa, estando comprendido entre el menor y el mayor de los límites de alta frecuencia de las subestructuras que componen el sistema completo. Los resultados obtenidos mediante la aplicación de este método evidencian una mejora en la continuidad de la respuesta vibroacústica, mostrando una transición suave entre los rangos de baja y alta frecuencia. El segundo método propuesto se denomina HS-CMS (del inglés Hybrid Substructuring method based on Component Mode Synthesis). Este método se basa en la clasificación de la base modal de las subestructuras en conjuntos de modos globales (que afectan a todo o a varias partes del sistema) o locales (que afectan a una única subestructura), utilizando un método de Síntesis Modal de Componentes. De este modo es posible situar espacialmente los modos del sistema completo y estudiar el comportamiento del mismo desde el punto de vista de las subestructuras. De nuevo se emplea el concepto de límite de alta frecuencia de una subestructura para realizar la clasificación global/local de los modos en la misma. Mediante dicha clasificación se derivan las ecuaciones globales del movimiento, gobernadas por los modos globales, y en las que la influencia del conjunto de modos locales se introduce mediante modificaciones en las mismas (en su matriz dinámica de rigidez y en el vector de fuerzas). Las ecuaciones locales se resuelven empleando Análisis Estadístico de Energías. Sin embargo, este último será un modelo híbrido, en el cual se introduce la potencia adicional aportada por la presencia de los modos globales. El método ha sido probado para el cálculo de la respuesta de estructuras sometidas tanto a cargas estructurales como acústicas. Ambos métodos han sido probados inicialmente en estructuras sencillas para establecer las bases e hipótesis de aplicación. Posteriormente, se han aplicado a estructuras espaciales, como satélites y reflectores de antenas, mostrando buenos resultados, como se concluye de la comparación de las simulaciones y los datos experimentales medidos en ensayos, tanto estructurales como acústicos. Este trabajo abre un amplio campo de investigación a partir del cual es posible obtener metodologías precisas y eficientes para reproducir el comportamiento vibroacústico de sistemas en el rango de la media frecuencia. ABSTRACT Over the last years an increasing need of novel prediction techniques for vibroacoustic analysis of space structures has arisen. Current numerical techniques arc able to predict with enough accuracy the vibro-acoustic behaviour of systems with low and high modal densities. However, space structures are, in general, very complex and they present a range of frequencies in which a mixed behaviour exist. In such cases, the full system is composed of some sub-structures which has low modal density, while others present high modal density. This frequency range is known as the mid-frequency range and to develop methods for accurately describe the vibro-acoustic response in this frequency range is the scope of this dissertation. For the structures under study, the aforementioned low and high modal densities correspond with the low and high frequency ranges, respectively. For the low frequency range, deterministic techniques as the Finite Element Method (FEM) are used while, for the high frequency range statistical techniques, as the Statistical Energy Analysis (SEA), arc considered as more appropriate. In the mid-frequency range, where a mixed vibro-acoustic behaviour is expected, any of these numerical method can not be used with enough confidence level. As a consequence, it is usual to obtain an undetermined gap between low and high frequencies in the vibro-acoustic response function. This dissertation proposes two different solutions to the mid-frequency range problem. The first one, named as The Subsystem based High Frequency Limit (SHFL) procedure, proposes a multi-hybrid procedure in which each sub-structure of the full system is modelled with the appropriate modelling technique, depending on the frequency of study. With this purpose, the concept of high frequency limit of a sub-structure is introduced, marking out the limit above which a substructure has enough modal density to be modelled by SEA. For a certain analysis frequency, if it is lower than the high frequency limit of the sub-structure, the sub-structure is modelled through FEM and, if the frequency of analysis is higher than the high frequency limit, the sub-structure is modelled by SEA. The procedure leads to a number of hybrid models required to cover the medium frequency range, which is defined as the frequency range between the lowest substructure high frequency limit and the highest one. Using this procedure, the mid-frequency range can be define specifically so that, as a consequence, an improvement in the continuity of the vibro-acoustic response function is achieved, closing the undetermined gap between the low and high frequency ranges. The second proposed mid-frequency solution is the Hybrid Sub-structuring method based on Component Mode Synthesis (HS-CMS). The method adopts a partition scheme based on classifying the system modal basis into global and local sets of modes. This classification is performed by using a Component Mode Synthesis, in particular a Craig-Bampton transformation, in order to express the system modal base into the modal bases associated with each sub-structure. Then, each sub-structure modal base is classified into global and local set, fist ones associated with the long wavelength motion and second ones with the short wavelength motion. The high frequency limit of each sub-structure is used as frequency frontier between both sets of modes. From this classification, the equations of motion associated with global modes are derived, which include the interaction of local modes by means of corrections in the dynamic stiffness matrix and the force vector of the global problem. The local equations of motion are solved through SEA, where again interactions with global modes arc included through the inclusion of an additional input power into the SEA model. The method has been tested for the calculation of the response function of structures subjected to structural and acoustic loads. Both methods have been firstly tested in simple structures to establish their basis and main characteristics. Methods are also verified in space structures, as satellites and antenna reflectors, providing good results as it is concluded from the comparison with experimental results obtained in both, acoustic and structural load tests. This dissertation opens a wide field of research through which further studies could be performed to obtain efficient and accurate methodologies to appropriately reproduce the vibro-acoustic behaviour of complex systems in the mid-frequency range.

Railway Rapid Transit timetables with variable and elastic demand.

This paper focuses on the design of railway timetables considering a variable elastic demand profile along a whole design day. Timetabling is the third stage in the classical hierarchical railway planning process. Most of previous works on this topic consider a uniform demand behavior for short planning intervals. In this paper, we propose a MINLP model for designing non-periodic timetables on a railway corridor where demand is dependent on waiting times. In the elastic demand case, long waiting times lead to a loss of passengers, who may select an alternative transportation mode. The mode choice is modeled using two alternative methods. The first one is based on a sigmoid function and can be used in case of absence of information for competitor modes. In the second one, the mode choice probability is obtained using a Logit model that explicitly considers the existence of a main alternative mode. With the purpose of obtaining optimal departure times, in both cases, a minimization of the loss of passengers is used as objective function. Finally, as illustration, the timetabling MINLP model with both mode choice methods is applied to a real case and computational results are shown.

Analysis of the problems associated with dynamic interaction between train, track and structure at transition zones

El gran desarrollo experimentado por la alta velocidad en los principales países de la Unión Europea, en los últimos 30 años, hace que este campo haya sido y aún sea uno de los principales referentes en lo que a investigación se refiere. Por otra parte, la aparición del concepto super − alta velocidad hace que la investigación en el campo de la ingeniería ferroviaria siga adquiriendo importancia en los principales centros de investigación de los países en los que se desea implantar este modo de transporte, o en los que habiendo sido ya implantado, se pretenda mejorar. Las premisas de eficacia, eficiencia, seguridad y confort, que este medio de transporte tiene como razón de ser pueden verse comprometidas por diversos factores. Las zonas de transición, definidas en la ingeniería ferroviaria como aquellas secciones en las que se produce un cambio en las condiciones de soporte de la vía, pueden afectar al normal comportamiento para el que fue diseñada la infraestructura, comprometiendo seriamente los estándares de eficiencia en el tiempo de viaje, confort de los pasajeros y aumentando considerablemente los costes de mantenimiento de la vía, si no se toman las medidas oportunas. En esta tesis se realiza un estudio detallado de la zonas de transición, concretamente de aquellas en las que existe una cambio en la rigidez vertical de la vía debido a la presencia de un marco hidráulico. Para realizar dicho estudio se lleva a cabo un análisis numérico de interacción entre el vehículo y la estructura, con un modelo bidimensional de elemento finitos, calibrado experimentalmente, en estado de tensión plana. En este análisis se tiene en cuenta el efecto de las irregularidades de la vía y el comportamiento mecánico de la interfaz suelo-estructura, con el objetivo de reproducir de la forma más real posible el efecto de interacción entre el vehículo, la vía y la estructura. Otros efectos como la influencia de la velocidad del tren y los asientos diferenciales, debidos a deformaciones por consolidación de los terraplenes a ambos lados el marco hidráulico, son también analizados en este trabajo. En esta tesis, los cálculos de interacción se han llevado a cabo en dos fases diferentes. En la primera, se ha considerado una interacción sencilla debida al paso de un bogie de un tren Eurostar. Los cálculos derivados de esta fase se han denominado cálculos a corto plazo. En la segunda, se ha realizado un análisis considerando múltiples pasos de bogie del tren Eurostar, conformando un análisis de degradación en el que se tiene en cuenta, en cada ciclo, la deformación de la capa de balasto. Los cálculos derivados de esta fase, son denominados en el texto como cálculos a largo plazo. Los resultados analizados muestran que la utilización de los denominados elementos de contacto es fundamental cuando se desea estudiar la influencia de asientos diferenciales, especialmente en transiciones terraplén-estructura en las que la cuña de cimentación no llega hasta la base de cimentación de la estructura. Por otra parte, tener en cuenta los asientos del terraplén, es sumamente importante, cuando se desea realizar un análisis de degradación de la vía ya que su influencia en la interacción entre el vehículo y la vía es muy elevada, especialmente para valores altos de velocidad del tren. En cuanto a la influencia de las irregularidades de la vía, en los cálculos efectuados, se revela que su importancia es muy notable, siendo su influencia muy destacada cuanto mayor sea la velocidad del tren. En este punto cabe destacar la diferencia de resultados derivada de la consideración de perfiles de irregularidades de distinta naturaleza. Los resultados provenientes de considerar perfiles artificiales son en general muy elevados, siendo estos más apropiados para realizar estudios de otra índole, como por ejemplo de seguridad al descarrilamiento. Los resultados provenientes de perfiles reales, dados por diferentes Administradores ferroviarios, presentan resultados menos elevados y más propios del problema analizar. Su influencia en la interacción dinámica entre el vehículo y la vía es muy importante, especialmente para velocidades elevadas del tren. Además el fenómeno de degradación conocido como danza de traviesas, asociado a zonas de transición, es muy susceptible a la consideración de irregularidades de la vía, tal y como se desprende de los cálculos efectuados a largo plazo. The major development experienced by high speed in the main countries of the European Union, in the last 30 years, makes railway research one of the main references in the research field. It should also be mentioned that the emergence of the concept superhigh − speed makes research in the field of Railway Engineering continues to gain importance in major research centers in the countries in which this mode of transportation is already implemented or planned to be implemented. The characteristics that this transport has as rationale such as: effectiveness, efficiency, safety and comfort, may be compromised by several factors. The transition zones are defined in railway engineering as a region in which there is an abrupt change of track stiffness. This stiffness variation can affect the normal behavior for which the infrastructure has been designed, seriously compromising efficiency standards in the travel time, passenger comfort and significantly increasing the costs of track maintenance, if appropriate measures are not taken. In this thesis a detailed study of the transition zones has been performed, particularly of those in which there is a change in vertical stiffness of the track due to the presence of a reinforced concrete culvert. To perform such a study a numerical interaction analysis between the vehicle, the track and the structure has been developed. With this purpose a two-dimensional finite element model, experimentally calibrated, in a state of plane stress, has been used. The implemented numerical models have considered the effects of track irregularities and mechanical behavior of soil-structure interface, with the objective of reproducing as accurately as possible the dynamic interaction between the vehicle the track and the structure. Other effects such as the influence of train speed and differential settlement, due to secondary consolidation of the embankments on both sides of culvert, have also been analyzed. In this work, the interaction analysis has been carried out in two different phases. In the first part a simple interaction due to the passage of a bogie of a Eurostar train has been considered. Calculations derived from this phase have been named short-term analysis. In the second part, a multi-load assessment considering an Eurostar train bogie moving along the transition zone, has been performed. The objective here is to simulate a degradation process in which vertical deformation of the ballast layer was considered. Calculations derived from this phase have been named long-term analysis. The analyzed results show that the use of so-called contact elements is essential when one wants to analyze the influence of differential settlements, especially in embankment-structure transitions in which the wedge-shaped backfill does not reach the foundation base of the structure. Moreover, considering embankment settlement is extremely important when it is desired to perform an analysis of track degradation. In these cases the influence on the interaction behaviour between the vehicle and the track is very high, especially for higher values of speed train. Regarding the influence of the track irregularities, this study has proven that the track’s dynamic response is heavily influenced by the irregularity profile and that this influence is more important for higher train velocities. It should also be noted that the difference in results derived from consideration of irregularities profiles of different nature. The results coming from artificial profiles are generally very high, these might be more appropriate in order to study other effects, such as derailment safety. Results from real profiles, given by the monitoring works of different rail Managers, are softer and they fit better to the context of this thesis. The influence of irregularity profiles on the dynamic interaction between the train and the track is very important, especially for high-speeds of the train. Furthermore, the degradation phenomenon known as hanging sleepers, associated with transition zones, is very susceptible to the consideration of track irregularities, as it can be concluded from the long-term analysis.