A. Gauchía

Influence of a shock absorber model on vehicle dynamic simulation

Abstract The dynamic simulation of mechanical systems is an essential tool in vehicle design. This work analyses the influence of a shock absorber model on a vehicles dynamic behaviour by means of a simulation-based model. The real behaviour of a European medium-range car shock absorber has been obtained by means of a test rig. From the dampers real behaviour, three mathematical models were generated, increasing the complexity. An existing full vehicle simulation application (CarSim™) was used for this particular study. The vehicles behaviour was analysed for typical driving manoeuvres taking into account lateral, vertical, and longitudinal forces and was compared with the results obtained with the different shock absorber models developed. As a result of this paper, it was demonstrated that, in order to obtain results with an acceptable level of accuracy, it is not necessary to rely on extremely complex shock absorber models.

A Sensor Fusion Method Based on an Integrated Neural Network and Kalman Filter for Vehicle Roll Angle Estimation

This article presents a novel estimator based on sensor fusion, which combines the Neural Network (NN) with a Kalman filter in order to estimate the vehicle roll angle. The NN estimates a “pseudo-roll angle” through variables that are easily measured from Inertial Measurement Unit (IMU) sensors. An IMU is a device that is commonly used for vehicle motion detection, and its cost has decreased during recent years. The pseudo-roll angle is introduced in the Kalman filter in order to filter noise and minimize the variance of the norm and maximum errors’ estimation. The NN has been trained for J-turn maneuvers, double lane change maneuvers and lane change maneuvers at different speeds and road friction coefficients. The proposed method takes into account the vehicle non-linearities, thus yielding good roll angle estimation. Finally, the proposed estimator has been compared with one that uses the suspension deflections to obtain the pseudo-roll angle. Experimental results show the effectiveness of the proposed NN and Kalman filter-based estimator.

Dynamic Performance Analysis of a Light Van Body-In-White Structure:

Requirement for low emissions and better vehicle performance has led to the demand for lightweight vehicle structures. Lighter gauge panels are being used to construct the body-in-white (BIW) monocoque structure, which is the basic component of the vehicle body. Since lighter gauge panels tend to generate more vibration and interior noise, it is necessary to optimize the dynamic performance of lightweight vehicle structures in order to achieve acceptable levels of vibro-acoustic performance. The design of a light commercial van structure has evolved over the years and through a lightweighting exercise the current BIW is about 10 per cent lighter than the previous BIW even though the volume capacity was increased by 15 per cent and the load-carrying capacity by 18 per cent. In this study, the dynamic performance of the current production light van BIW structure is investigated. Its performance is assessed against the structural dynamic performance standards which have been established for this class of structures. While the input mobility performance was found to exceed the standards easily, the modal mobility performance was found to be unsatisfactory owing to the occurrence of local panel resonant modes in the two side panels. A finite element model of the structure was developed to study the effect of adding stringers to the roof and side panels to eliminate some of the local panel modes and thus to improve the dynamic performance of the structure.

Bump Modeling and Vehicle Vertical Dynamics Prediction

During a journey, motor vehicles are subjected to different types of irregularities in the pavement. Some of these irregularities are introduced for a specific purpose over a stretch of road to slow down the vehicle at certain road points. However, the influence of installed speed bumps reveals certain additional effects which must be deeply analyzed to ensure vehicle and pedestrian safety. In some cases, it has been found that even when driving over transverse bands at a speed below the legal limit, the vehicle is damaged or tires lose grip with the pavement, precluding any kind of braking or turning maneuvers. Such phenomena indicate that either this element is not properly sized or the location is not appropriate, becoming counterproductive for traffic safety. In order to analyze the influence of these irregularities on the different components of the vehicle and its occupants, a simulation program with MatlabTM has been developed. The validated developed tool takes into account several aspects of the vehicle dynamics, bump geometry, and vehicle speed. The proposed tool provides the best possible information to establish a set of guidelines for the proper design and installation of speed bumps in different roads.

Material parameters in a simulation of metal sheet stamping

Abstract The paper presents a methodology to tackle the problem of new materials, such as high-strength steels, used in industrial manufacturing. This methodology, which uses the finite element method (FEM), is based on two main ideas: determining the material properties as accurately as possible and automating the FEM simulation as much as possible. The main tool to solve these problems is an application designed to assist die stamp designers. Such an application can be used by anyone, even with no knowledge about finite elements, and does not need user participation. This fact makes the program very powerful and allows a procedure to be defined to obtain the values of the properties of an unknown material, which combines finite element simulations with real experimental results. The paper presents the developed application as well as the procedure used to determine the material properties. By combining both aspects, it is possible to simulate any stamping process, allowing the designer to obtain much information in the earlier stages of design. This paper fulfils an identified need in the manufacturing industry. In fact, the proposed application is currently being used by a manufacturer of automotive components.

Expert system for simulation of metal sheet stamping

Stamping processes are frequently used in the automotive industry. In an attempt to reduce developing times and costs, conventional design and manufacturing procedures are being changed. Finite element simulations have proved to be a good help in the design and analysis of these processes. The main problem of these simulations is that they are quite difficult to perform and that there are several non-trivial questions that the user has to answer before achieving a good model. In this work, a new application has been designed. It combines the usability of a custom application with the power of such a tool as the finite element method. To design this application, a lot of questions regarding FEM simulation of stamping processes have been analyzed. The result is a methodology to automate simulations of stamping processes where the user does not need to have deep knowledge of the finite element software. Such methodology has been successfully employed in a Spanish manufacturing industry of automotive components.

Influence of Speed Bumps Design on Vehicle Safety

During a journey motor vehicles are forced to overcome different types of irregularities in the pavement. Such irregularities can be random or introduced for a specific purpose, such as asphalt protrusions and transversal bands of rubber, which have been installed into all sorts of avenues and roads open to traffic. Generally, these elements are included in a stretch of road to slow down the vehicle velocity at certain sites, such as pedestrian crossings. However, the influence of speed bumps installed shows other additional effects which must be studied to ensure the safety of vehicles and pedestrians. In some cases, it is found that, passing over ridges and transverse bands at a speed below the limit defined by law, the vehicle is damaged or the tires lose grip with the pavement, precluding any kind of braking or turning maneuvers. Such phenomena indicate that this element is not properly sized, or the placement is not appropriate, becoming counterproductive for traffic safety. In spite of the importance of these consecuences derivated from these elements they haven’t been studied deeply enough and there are very few paper about this subject. In order to analyze the actions generated by the overcome of these irregularities on the different components of the vehicle and its occupants, the problem has been studied not only using computer simulation but also by means of experimental testing on a real vehicle where accelerometers were installed in order to check the severity of the bumps. CarSimTM has been the simulation software used to calculate vehicle dynamic forces on the tires and suspension system and the accelerations and displacements that are applied to the vehicle. To characterize the behavior of a vehicle when is driven over one of these obstacles, it is necessary to study several parameters such as: speed, geometry and dimensions of the bump, and the type of vehicle and its suspension. From this information it is possible to establish a set of guidelines for the proper design and installation of speed bumps in different roads.Copyright

Bus mathematical model of acceleration threshold limit estimation in lateral rollover test

Vehicle safety is a major concerns for researchers, governments and vehicle manufacturers, and therefore a special attention is paid to it. Particularly, rollover is one of the types of accidents where researchers have focused due to the gravity of injuries and the social impact it generates. One of the parameters that define bus lateral behaviour is the acceleration threshold limit, which is defined as the lateral acceleration from which the rollover process begins to take place. This parameter can be obtained by means of a lateral rollover platform test or estimated by means of mathematical models. In this paper, the differences between these methods are deeply analysed, and a new mathematical model is proposed to estimate the acceleration threshold limit in the lateral rollover test. The proposed model simulates the lateral rollover test, and, for the first time, it includes the effect of a variable position of the centre of gravity. Finally, the maximum speed at which the bus can travel in a bend without rolling over is computed.

Modelo Simplificado para Evaluar la Torsión de un Autobús Urbano

En este articulo se propone un nuevo modelo matematico simplificado para evaluar el comportamiento de la carroceria de un autobus urbano ante esfuerzos de torsion. Evaluar la torsion de un autobus urbano es importante debido a que la rigidez a torsion afecta al comportamiento del vehiculo en los movimientos de balanceo y en la transferencia de carga a cada lado del eje. Para determinar el giro de una seccion de la superestructura de un autobus urbano al aplicar un determinado momento torsor se ha aplicado la teoria de torsion en perfiles de seccion transversal cerrada de pared delgada y la expresion de la rigidez a la torsion de una estructura tipo escalera. Los resultados obtenidos son comparados con los calculados mediante elementos finitos, mostrando que el modelo propuesto es un metodo valido alternativo para evaluar la torsion de un autobus urbano.

Sensor Fusion Based on an Integrated Neural Network and Probability Density Function (PDF) Dual Kalman Filter for On-Line Estimation of Vehicle Parameters and States

Vehicles with a high center of gravity (COG), such as light trucks and heavy vehicles, are prone to rollover. This kind of accident causes nearly 33% of all deaths from passenger vehicle crashes. Nowadays, these vehicles are incorporating roll stability control (RSC) systems to improve their safety. Most of the RSC systems require the vehicle roll angle as a known input variable to predict the lateral load transfer. The vehicle roll angle can be directly measured by a dual antenna global positioning system (GPS), but it is expensive. For this reason, it is important to estimate the vehicle roll angle from sensors installed onboard in current vehicles. On the other hand, the knowledge of the vehicle’s parameters values is essential to obtain an accurate vehicle response. Some of vehicle parameters cannot be easily obtained and they can vary over time. In this paper, an algorithm for the simultaneous on-line estimation of vehicle’s roll angle and parameters is proposed. This algorithm uses a probability density function (PDF)-based truncation method in combination with a dual Kalman filter (DKF), to guarantee that both vehicle’s states and parameters are within bounds that have a physical meaning, using the information obtained from sensors mounted on vehicles. Experimental results show the effectiveness of the proposed algorithm.