Gregorio Romero

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.

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.

Modelling and simulation of a thrombectomy probe applied to the middle cerebral artery by using the bond graph technique

Thrombosis is produced by the formation of a clot inside blood vessels causing an abrupt interruption of the blood flow. In the cerebral arteries, this occlusion can take place due to the presence of a clot that has formed at another location of greater diameter. It then obstructs the cerebral artery due to its smaller cross section. The process concerning the removal of this obstruction involves catheterisation. The experimental probe under study in this paper was developed by Dr G. Pearce and Reverend Neil Perkinson [1]. The probe, which when developed further may form the basis of a new Thrombectomy Aspiration Device (TAD) is called the GPTAD. Once fully developed, the GPTAD may provide a means of clot removal from vessels in the human arterial system e.g. the cerebral vessels. The modelling that we present in this paper, taking into account the catheter, the probe, artery, blood clot and adhesion forces, may assist with the optimisation of the design of the GPTAD probe. In the model used for the simulation both mechanical and hydraulic aspects have been considered with the purpose of combining the effect of the fluid-blood transmission for the different sections of the vein and the catheter.

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...

An investigation into the performance of a new mechanical thrombectomy device using bond graph modeling: application to the extraction of blood clots in the middle cerebral artery

A number of thrombectomy devices using a variety of methods have now been developed to facilitate clot removal. We present research involving one such experimental device recently developed in the UK, called a ‘GP’ Thrombus Aspiration Device (GPTAD). This device has the potential to bring about the extraction of a thrombus. Although the device is at a relatively early stage of development, the results look encouraging. In this work, we present an analysis and modeling of the GPTAD by means of the bond graph technique; it seems to be a highly effective method of simulating the device under a variety of conditions. Such modeling is useful in optimizing the GPTAD and predicting the result of clot extraction. The aim of this simulation model is to obtain the minimum pressure necessary to extract the clot and to verify that both the pressure and the time required to complete the clot extraction are realistic for use in clinical situations, and are consistent with any experimentally obtained data. We therefore consider aspects of rheology and mechanics in our modeling.

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.

A musculoskeletal human gait model using the Bond Graph technique

Today, the modeling and simulation of the human gait musculoskeletal system is well-developed using various techniques such as the vectorial mechanics and Lagrange’s Equations, the Kane’s method, etc. This paper proposes the use of the Bond Graph technique as an alternative method, developing primarily the muscle models needed to simulate, analyze and correct, in case of existing pathologies, the human gait motion. Two of the largest potentialities of the Bond Graph technique are their modular and multi-domain capacities. These capabilities facilitate the modification of the muscle parameters giving flexibility to the models and allowing a dynamic analysis of the gait. For each muscle, it has been used the Hill-type model that, with its schematic representation of the muscular functions such as the mechanical force generation, serial elastic, passive elastic, and damping elements, speeds up its implementation through the use of the Bond Graph technique.

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.

An Alternative for Human Gait Modeling Using the Bondgraph Technique

The systematic analysis of the human gait with a skeletal or neuromuscular disorder is a valuable clinical instrument to determine the nature and severity of the disease. At present, there are many institutions that have developed a series of numerical models that simulate and analyze biomechanics systems such as the human gait.