M. Luisa Martinez

A constraint solver to define correctly dimensioned and overdimensioned parts

Creating mechanical parts through conceptual design implies the use of constraints. When developing conceptual design-based CAD programs, two independent modules must be created: on the one hand, the sketcher module, which must define the models geometrical constraints and interpret the users intention through a system of rules. On the other, the calculation module which must resolve the final geometry and eventually dimension the mechanical part. This paper presents a new approach to the constraint-based solvers. The proposed approach establishes the complete two-dimensional geometry and constraints of a sketch and relates it with the complete dimensioning of the sketch. The developed methodology gives as result a complete and consistent dimensioning of the sketch following the rules established by a standard like ISO, determining also if the system is over-constrained and detecting the redundant dimensions. The methodology establishes the most suitable dimensioning but, it is also possible to obtain other alternatives of full sets of dimensions. First, the geometric constraints considered are described, and the use of each one justified, together with the numerical methods used to resolve the set of non-linear constraints obtained. A procedure has also been developed for choosing the set of independent constraints of the system, by introducing the priority factor concept, which lets the overriding constraints in the system be decided, and then the algorithms developed for automatically assigning the constraints are presented. Also described are the criteria followed that lead to an automatic generation of dimensions, as well as to equivalent and alternative dimensioning. Finally, a series of examples are presented to show the possibilities of the developed methodology.

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.

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.

Virtual reality applied to traffic accident analysis

This paper presents an application of virtual reality techniques to traffic accident analysis. The paper shows the features of the developed software and the characteristics of the corresponding virtual environment: objects, tasks, behaviors, actions, etc. Physical models used to define the real behavior of the objects involved in the accident are also described. A specific collision model is presented. This model reproduces the forces that appear in a traffic accident. Some considerations on further applications of this work are also presented, including its use in a network environment, including the WWW. Finally, a case study is introduced.

Simulation of the Electrical Operation of a Lathe by Using PI Type Regulators and Bond-Graph Technique

When designing circuits, engineers need to know the voltages and intensities at every point in the circuit. In simple circuits the results can be calculated by hand by using complex numbers, but in complex circuits this is impossible. This is why, nowadays, recourse is had to computer simulation so that circuits can be designed before being built, since it eliminates the need to build prototypes of the circuits with the ensuing time and cost.Bond-Graph technique is a visual methodology that adds more transparency to the processes and it has turned out to be remarkably useful as it is a simple, effective method that can be applied to any physical system where there is a power exchange.This work initially analyses the starting mechanism of a direct current machine using Bond Graph technique, compares it with a model developed in Simulink