J. Maroto

Real-Time Traffic Simulation With a Microscopic Model

This paper describes a microscopic model that is able to simulate traffic situations in an urban environment in real time for use in driving simulators. Two types of vehicles are considered in the simulation, namely the user-driven vehicle at the center of the simulation model and the other vehicles that interact with it and its surroundings, which configure the developed traffic model. Simulation is performed in a reduced zone, called the control zone, surrounding the user-driven vehicle. This control zone is a mobile zone centered on the user-driven vehicle. The size of the control zone depends on the maximum number of vehicles involved simultaneously, the traffic density, and the drivers limit of visibility. The other vehicles involved in the traffic simulation are created or destroyed within the limits of the control zone. The general behavior of the traffic model is based on the following theory. Vehicles have an associated driver model that establishes several control functions for them to follow the path, while the steering, acceleration, and braking maneuvers follow certain models of behavior. A traffic light regulation is also included but only in the control area. The possibility of introducing anomalous traffic situations into the simulation is also considered, such as the presence of obstacles, abnormal maneuvers, etc. The developed model is immediately applicable to large-scale driving simulators for driver training, traffic control studies, and safety studies

Efficient simulation of mechanism kinematics using bond graphs

Abstract This paper presents a methodology for obtaining the equations corresponding to a mechanism that are necessary for carrying out a kinematic simulation. A simulation of this kind means obtaining the coordinates dependent on the system according to the movements imposed by the degrees of freedom. Unlike a dynamic simulation, where the set of elements moves according to the different external forces existing, in kinematic simulation the movement of the whole set depends exclusively on imposing movement on one or more of the bodies according to the degrees of freedom initially possessed by the mechanism. After presenting an analysis of how to obtain the necessary equations for several simple systems, this methodology is applied to the particular case of a front-loader, where in order to move and tilt the bucket, various closed mechanisms are integrated.

A Full Driving Simulator of Urban Traffic including Traffic Accidents

This paper describes a model for traffic simulation of an urban environment and its implementation in a driving simulator. The simulator is also able to reproduce realistic traffic accidents. In order to attain real-time simulation, the simulation environment has been partitioned considering the city as divided into segments of road, junctions, and sectors that minimize the interaction between the cars involved in the traffic simulation and the traffic simulation is considered only in a control zone centered on the driven vehicle. Simplified dynamic vehicle models have also been used when vehicles are not involved in the accident, allowing for a sufficiently realistic behavior. A traffic light regulation only in the area next to the driven vehicle is also included. A complex model for the vehicles involved in traffic accidents has been developed, including multibody components and different collision models. The developed model is then immediately applicable to large scale driving simulators.

Sensitivity analysis to assess the influence of the inertial properties of railway vehicle bodies on the vehicle's dynamic behaviour

A sensitivity analysis has been performed to assess the influence of the inertial properties of railway vehicles on their dynamic behaviour. To do this, 216 dynamic simulations were performed modifying, one at a time, the masses, moments of inertia and heights of the centre of gravity of the carbody, the bogie and the wheelset. Three values were assigned to each parameter, corresponding to the percentiles 10, 50 and 90 of a data set stored in a database of railway vehicles. After processing the results of these simulations, the analysed parameters were sorted by increasing influence. It was also found which of these parameters could be estimated with a lesser degree of accuracy for future simulations without appreciably affecting the simulation results. In general terms, it was concluded that the most sensitive inertial properties are the mass and the vertical moment of inertia, and the least sensitive ones the longitudinal and lateral moments of inertia.

Kinematic Analysis Of Mechanism By Using Bond-Graph Language

This paper presents a methodology for obtaining the equations corresponding to a mechanism that are necessary for carrying out a kinematic simulation. A simulation of this kind means obtaining the co-ordinates dependent on the system according to the movements imposed by the degrees of freedom. Unlike a dynamic simulation, where the set of elements moves according to the different external forces existing, in kinematic simulation the movement of the whole set depends exclusively on imposing movement on one or more of the bodies according to the degrees of freedom initially possessed by the mechanism. After presenting an analysis of how to obtain the necessary equations for several simple systems, this methodology is applied to the particular case of a wheel loader, where in order to move and tilt the bucket, various closed mechanisms are integrated.

Simulation of an Asynchronous Machine by using a Pseudo Bond Graph

For engineers, computer simulation, is a basic tool since it enables them to understand how systems work without actually needing to see them. They can learn how they work in different circumstances and optimize their design with considerably less cost in terms of time and money than if they had to carry out tests on a physical system. However, if computer simulation is to be reliable it is essential for the simulation model to be validated. There is a wide range of commercial brands on the market offering products for electrical domain simulation (SPICE, LabVIEW PSCAD,Dymola, Simulink, Simplorer,...). These are powerful tools, but require the engineer to have a perfect knowledge of the electrical field. This paper shows an alternative methodology to can simulate an asynchronous machine using the multidomain Bond Graph technique and apply it in any program that permit the simulation of models based in this technique; no extraordinary knowledge of this technique and electric field are required to understan...

A full-scale simulation model to reproduce urban traffic in real conditions in driving simulators

This paper describes a model capable of simulating large-scale traffic in an urban environment. The goal is of this work is the realistic and detailed simulation of the traffic, reproducing the behavior of each vehicle involved in the environment individually. This model has been developed in order to be integrated in an immersive driving simulator, where the driving position is the center of the simulation and the traffic model reproduces what happens around them. The general behavior of the traffic model is based on the following theory. Depending on the size of the urban environment to be simulated, the number of vehicles involved, and the traffic density, the environment can be studied as a whole or segmented in adjacent areas. Each vehicle model has two components. First, the behavior of the vehicle is simulated individually, modeling acceleration and braking, depending on the type and characteristics of each vehicle (mass, power, size, etc.). Second, the behavior of the drivers is also modeled, by type (passive, moderate, aggressive), playing various maneuvers also common in urban traffic circulation, such as lane changes, behavior at crossings and intersections, etc. A traffic light regulation model and the complete signposting of the urban environment are also included. As a result, the developed traffic model is applicable to large-scale traffic simulation integrated in an immersive driving simulator and is very useful when investigating complex behaviors of these environments. The model has been validated comparing it with results obtained from various references and very satisfactory results have been obtained.

Simulation of Multi-body Systems Using Multi-bond Graphs

The use of multi-bond graphs (MBGs) has an increasing importance in the development of large mechanical systems, called multi-body systems (MBS), composed of a finite number of rigid bodies interconnected by kinematical constraints. The constitutive relationships of multi-bond resistors, transformers, and gyrators give way to zero-order causal paths (ZCPs) whose most important peculiarity is that their associated topological loops involve more than one direction. Two different methods are used to solve the ZCPs. With the first one, Lagrange multipliers are introduced by means of new flows and efforts as break variables of causal paths, adding constraint equations. With the second one, break variables are used directly to open the ZCPs. The procedure used solves the problem and implies the presence of new variables and constraint equations. Several algorithms have been developed to obtain the set of equations. The result is a set of differential–algebraic equations (DAEs) solved using a backward differential formulae (BDF) numerical method. An application to multi-body systems with a combination of classes of ZCPs will be shown.

Blood clot simulation model by using the Bond-Graph technique.

The World Health Organization estimates that 17 million people die of cardiovascular disease, particularly heart attacks and strokes, every year. Most strokes are caused by a blood clot that occludes an artery in the cerebral circulation and the process concerning the removal of this obstruction involves catheterisation. The fundamental object of the presented study consists in determining and optimizing the necessary simulation model corresponding with the blood clot zone to be implemented jointly with other Mechanical Thrombectomy Device simulation models, which have become more widely used during the last decade. To do so, a multidomain technique is used to better explain the different aspects of the attachment to the artery wall and between the existing platelets, it being possible to obtain the mathematical equations that define the full model. For a better understanding, a consecutive approximation to the definitive model will be presented, analyzing the different problems found during the study. The final presented model considers an elastic characterization of the blood clot composition and the possibility of obtaining a consecutive detachment process from the artery wall. In conclusion, the presented model contains the necessary behaviour laws to be implemented in future blood clot simulation models.

A minimal set of dynamic equations in systems modelled with bond graphs

Abstract The current paper presents a procedure for converting to a minimal set the dynamic equations of a system modelled with bond graphs starting from a large set of differential-algebraic equations including any type of topological loops and zero-order causal paths (ZCPs). This minimal set is composed only of differential equations expressed in terms of the degrees of freedom of the system. These equations are suitable for use in real-time simulations. Initially, flows corresponding to inertances and displacements associated with compliances are used to establish the dynamic equations and to find the ZCPs of the system. Two different methods are used to solve the ZCPs. With the first method, Lagrange multipliers are introduced by means of new flows and efforts as break variables of causal paths, adding constraint equations. With the second method, break variables are used directly to open the ZCPs. The procedure developed in the present paper solves the problem originated by the use of Lagrange multipliers with the introduction of break variables that imply the presence of new variables and constraint equations. This procedure, before numerical integration of the dynamic equations, converts the equations to a minimal set in order to gain computational efficiency. Several examples are also provided to illustrate the conversion steps.