Modelos de simulación en tiempo real de sistemas granulares mediante autómatas celulares.

RESUMEN Las herramientas de formación basadas en simulación y realidad virtual se han convertido en las últimas décadas en una potente erramienta para la formación y el entrenamiento de multitud de tareas, especialmente aquéllas que conllevan un coste o un riesgo elevado.   Debido a las exigencias de este tipo de aplicaciones, los modelos dinámicos utilizados deben  reproducir el comportamiento del sistema simulado con suficiente realismo como para qu los hábitos adquiridos por los aprendices sean correctos. Además, deben ser suficientemente robustos y eficientes como para poder ejecutarse de forma interactiva en tiempo real.   Dentro del ámbito de la simulación de maquinaria pesada, los sistemas granulares y la interacción con el terreno (arena, grava, material granel, etc.) forman parte de las tareas  fundamentales que realiza el usuario. Sin embargo, como consecuencia de una metodología inadecuada, existe una deficiencia importante en los modelos existentes para simulación interactiva en tiempo real.   A lo largo de este trabajo se revisa la metodología de modelado utilizada habitualmente, y se desarrolla un conjunto de modelos dinámicos para la simulación de sistemas granulares.   Para conseguir modelos con un comportamiento suficientemente realista, se parte de estudios teóricos sobre el comportamiento de los sistemas granulares y la interacción con el suelo. A partir de estos estudios, y utilizando el modelo computacional de los Autómatas Celulares, se desarrolla un conjunto de modelos dinámicos que permiten la simulación interactiva de un sistema granular y una herramienta   Los modelos se validan  utilizando los trabajos teóricos anteriores, y se analiza el significado de los parámetros para permitir su ajuste en función del tipo de material que se desee simular.   Para conseguir una implementación eficiente de los modelos que permita la simulación en tiempo real, se analizan las propiedades estadísticas de la dinámica del sistema. Gracias a este análisis se consigue alcanzar un coste inferior a cuadrático respecto a las dimensiones del sistema simulado.   Se revisan las técnicas de representación gráfica existentes y se mejora la representación de las zonas de flujo por medio de l utilización de técnicas de multitextura programadas en el procesador gráfico. ______________________________________________________________________________________________The training tools based on simulation and virtual reality have become in recent decades into a powerful tool for education and training of many tasks, especially those that involve a cost or a high risk.   Due to the demands of such applications, the dynamic models have to reproduce the behavior of the system simulated with sufficient realism so that the habits acquired by trainees are correct. Furthermore, they must be sufficiently robust and efficient to be able to run interactively in real time. Within the scope of the simulation of heavy machinery, granular systems and the interaction with the ground (sand, gravel, bulk material, etc..) are part of the fundamental tasks performed by the user. However, as a result of inadequate methodology, there is a major deficiency in existing models for real-time interactive simulation. Throughout this work we review the modeling methodology used routinely, and developed a set of dynamic models for the simulation of granular systems. To obtain models with a sufficiently realistic behavior is part of theoretical studies on the behavior of granular systems and interaction with the ground. From these studies, and using the computational model of cellular automata, we develop a set of dynamic models that allow for interactive simulation of a granular system and a tool. The models are validated using the previous theoretical work, and discusses the significance of the parameters to allow adjustment of the type of material you want to simulate. To achieve an efficient implementation of the models to allow the simulation in real time, we analyze the statistical properties of the dynamics of the system. Thanks to this analysis we reach a cost of less than quadratic with respect to the dimensions of the simulated system. We review the existing techniques of graphic representation and improving the representation of the flow areas through the use of techniques multitextured programmed in the processor graph.

Modelling and simulation of several interacting cellular automata

Cellular Automata are used for modelling and simulation of many systems. In some applications, the system is formed by a set of subsystems that can be modelled separately, but, in such cases, the existence of interactions between these subsystems requires additional modelling and computer programming. In this paper we propose a modelling methodology for the simulation of a set of Cellular Automata models that interact with each other. The modelling methodology is described, together with an insight on implementation details. Also, it is applied to a particular Cellular Automata model, the Sanpile Model, to illustrate its use and to obtain some example simulations

Interactive Terrain Simulation and Force Distribution Models in Sand Piles

This paper presents an application of Cellular Automata in the field of dry Granular Systems modelling. While the study of granular systems is not a recent field, no efficient models exist, from a computational point of view, in classical methodologies. Some previous works showed that the use of Cellular Automata is suitable for the development of models that can be used in real time applications. This paper extends the existing Cellular Automata models in order to make them interactive. A model for the reaction to external forces and a pressure distribution model are presented and analyzed, with numerical examples and simulations

Computer Animation to teach interpolation

While mathematics courses are a basic topic in engineering studies, they are often considered as a dif- cult subject by students. In this work we present a learning experience based on computer animation and using the perspective of mathematical modelling. Our goal is to provide the students with a context that motivates the study of function interpolation. We present a problem statement that is intended to be solved by means of the Modeling Cycle. The development of the activity and the strategies identi ed during the process are presented and discussed

Videojuegos de estrategia en Educación Matemática. Una propuesta didáctica en secundaria

En este trabajo presentamos el análisis de una propuesta didáctica basada en una actividad de modelización para trabajar conceptos y procedimientos matemáticos mediante el videojuego Bloons Tower Defense 5. Se trata de un videojuego del género de defensa de torres y es un juego de estrategia en el que el jugador debe defender un territorio utilizando torres defensivas que disparan fuego a los enemigos de forma autónoma. El análisis de la propuesta didáctica presentada se basa en una experiencia llevada a cabo con alumnos de 4º curso de ESO y, según los resultados, se realizarán algunas propuestas de mejora al modelo de enseñanza inicial. La propuesta diseñada permite trabajar contenidos del bloque de funciones a través de la resolución de problemas de modelización, además los resultados de este estudio exploratorio pueden posibilitar la realización de investigaciones en el ámbito de la modelización

Texture advection on discontinuous flows

Texture advection techniques, which transport textures using a velocity field, are used to visualize the dynamics of a flow on a triangle mesh. Some flow phenomena lead to velocity fields with discontinuities that cause the deformation of the texture which is not properly controlled by these techniques. We propose a method to detect and visualize discontinuities on a flow, keeping consistent texture advection at both sides of the discontinuity. The method handles the possibility that the discontinuity travels across the domain of the flow with arbitrary velocity, estimating its speed with least-squares approximation. The technique is tested with different sample scenarios and with two avalanche scenes, showing that it can run at interactive rates

Forecasting Adverse Weather Situations in the Road Network

Weather is an important factor that affects traffic flow and road safety. Adverse weather situations affect the driving conditions directly; hence, drivers must be informed about the weather conditions downstream to adapt their driving. In the framework of intelligent transport systems, several systems have been developed to know the weather situations and inform drivers. However, these systems do not forecast weather in advance, and they need the support of road operators to inform drivers. This paper presents a new autonomous system to forecast weather conditions in a short time and to give users the information obtained. The system uses a set of algorithms and rules to determine the weather and to forecast dangerous situations on the road network. It has been implemented using a multiagent approach and tested with real data. Results are very promising. The system is able to forecast adverse situations with a high degree of quality. This quality makes it possible to trust in the system and to avoid the supervision of operators

New Developments in Simulation-Based Harbour Crane Training

This paper presents the efforts that have been made during the development of a set of harbour training simulators to improve their quality. The paper focuses on two main research lines: the improvement of complex physical systems involved in the simulation and the analysis of hardware architecture solutions. Cable-based hoist systems and bulk materials are systems present in different harbour equipment and are usually simulated with poor quality due to their complexity. In this paper physics-based models for the interactive simulation of these systems are proposed and applied to real cases. Also, different hardware simulator architectures are analysed and different approaches are proposed to the problem of choosing the devices for a simulator

Elevation Cable Modeling for Interactive Simulation of Cranes

In this paper, the way to simulate hoisting cables in real time is addressed. We overcome instability in such simulation by considering a two-layered model: a model for the dynamics of a cable passing through a set of pulleys and an oscillation model based on the classical one-dimensional wave equation. The first layer considers the interaction between the cable and pulleys with the elevation equipment, while the second layer simulates cable oscillation. Numerical instability is avoided by suspending the oscillation layer when required. Due to the system properties, this can be carried out in such a way that does not cause significant loss in the system quality. It considers the oscillation of the cable between every pair of pulleys, collision detection and the variation of the cable length very efficiently. Rendering issues are discussed, with remarks on how to prevent aliasing artifacts in the cable. Efficiency is analyzed, including performance tests which show that the model can be run very efficiently. The paper also covers how to integrate the model in a complex multibody simulation with a high degree of interactivity.In this paper, the way to simulate hoisting cables in real time is addressed. We overcome instability in such simulation by considering a two-layered model: a model for the dynamics of a cable passing through a set of pulleys and an oscillation model based on the classical one-dimensional wave equation. The first layer considers the interaction between the cable and pulleys with the elevation equipment, while the second layer simulates cable oscillation. Numerical instability is avoided by suspending the oscillation layer when required. Due to the system properties, this can be carried out in such a way that does not cause significant loss in the system quality. It considers the oscillation of the cable between every pair of pulleys, collision detection and the variation of the cable length very efficiently. Rendering issues are discussed, with remarks on how to prevent aliasing artifacts in the cable. Efficiency is analyzed, including performance tests which show that the model can be run very efficiently. The paper also covers how to integrate the model in a complex multibody simulation with a high degree of interactivity

Crane collision modelling using a neural network approach

The objective of the present work is to find a Collision Detection algorithm to be used in the Virtual Reality crane simulator (UVSim®), developed by the Robotics Institute of the University of Valencia for the Port of Valencia. The method is applicable to box-shaped objects and is based on the relationship between the colliding object positions and their impact points. The tool chosen to solve the problem is a neural network, the multilayer perceptron, which adapts to the characteristics of the problem, namely, non-linearity, a large amount of data, and no a priori knowledge. The results achieved by the neural network are very satisfactory for the case of box-shaped objects. Furthermore, the computational burden is independent from the object positions and how the surfaces are modelled; hence, it is suitable for the real-time requirements of the application and outperforms the computational burden of other classical methods. The model proposed is currently being used and validated in the UVSim Gantry Crane simulator