Simplified Vehicle Model Research Articles

An Efficient Numerical Model to Predict the Mechanical Response of a Railway Track in the Low-Frequency Range

With railway interoperability, new trains are allowed to move on the French railway network. These trains may present different designs from standard trains. This work aims to complete the current approach for vehicle admission on the railway network, which is defined in technical baselines. Historically, computation rules for traffic conditions are based on simplified analytical works, which are considerably qualitative. They have evolved through feedback and experimental campaigns to comply with the track structure evolution. An efficient methodology based on numerical simulation is needed to evaluate railway vehicle admission to answer this issue. A perspective to update these computation rules is to evaluate the structural fatigue in the rail. That is to say, fatigue is caused by bending and shear stresses. The complexity of the railway system has led to an investigation at first of the vertical response of the railway track and quantifying its contribution to the rail’s stress response. In that sense, this paper investigates the vertical track response to a moving railway vehicle at low frequencies. For this purpose, a lightweight numerical model for the track, a multi-body model for the vehicle, and a random vertical track irregularity are proposed. More explicitly, the track model consists of a two-layer discrete support model in which the rail is considered as a beam and sleepers are point masses. The rail pads and ballast layer are modelled as spring/damper couples. Numerical results show a negligible effect of track inertia forces due to high track stiffness and damping. Nevertheless, this assumption is valid for normal rail stresses but not for ballast loading, especially in the case of sleeper voids or unsupported sleepers. Hence, the prediction of the mechanical stress state in the rail for fatigue issues is achieved through a static track model where the equivalent loading is obtained from a dynamic study of a simplified vehicle model. A statistical analysis shows that the variability of the vertical track irregularity does not influence the output variabilities like the maximum in time and space of the normal and shear stress.

Double-parameter Hopf bifurcation analysis of a high-speed rail vehicle with an alternative wheel/rail contact approximation

This investigation integrates an alternative fully-parameterized approximation of nonlinear wheel/rail interaction into a simplified vehicle model, and a two-parameter Hopf bifurcation analysis is conducted to reveal the influence of the wheel/rail contact geometry and secondary suspension parameters for high-speed rail vehicles. The bifurcation diagram is compared among the 6 DOFs bogie model, linear and nonlinear 7 DOFs vehicle model, nonlinear 17 DOFs vehicle model, and 3D full DOFs vehicle model. It shows that the nonlinear 7 DOFs vehicle model can meet the requirement of both carbody hunting and bogie hunting simulations. 6 DOFs bogie model can only be used in bogie hunting bifurcation analysis. Linear vehicle model would bring errors in either critical speed or limit circle magnitude. The divergences in the linear terms of rolling radius and contact angle polynomials are significant enough in field operation to cause a noticeable difference in Hopf bifurcation speed. Attention shall be paid to the shape of equivalent conicity and contact angle curve. The crucial parameters to the Hopf bifurcation include the series stiffness and damping coefficient of the yaw damper and the lateral damper damping. However, the requirement of suspension parameters for stability can conflict in carbody hunting and bogie hunting cases.

Dynamic displacement response analysis of bridge in the impact vibration of slight and frequent vehicle bump

To study the impact of vehicle moving on bridge, the bump occurring under the determined limit conditions of vehicle from no bump to the beginning of bump was named as slight and frequent vehicle bump. With a 1/4 simplified vehicle model and the Euler-Bernoulli bridge model, the required minimum impact height for the bump and the effect of bump impact on the vertical dynamic mid-span displacement response of bridge were figured out in different vehicle speed, axle load and wheel diameter. The simulation analysis by ANSYS software, with HSFLD242 unit simulating air inside the tire and MASS21 simulating the car weight held by tires, verified the results of the minimum impact height. The effect of bump impact on the vertical dynamic mid-span displacement response of bridge was also verified by observation using the TCQN-6A bridge deflection detector on the mid-span dynamic deflection of a 25-metre simply supported beam bridge.

Trajectory Tracking of Autonomous Vehicle Based on Model Predictive Control With PID Feedback

The simplified vehicle model often results in inaccuracy with respect to the conventional model predictive control (MPC) as it causes steady error in tracking control, which has negative implications for vehicle cornering. This study presents a trajectory planning and tracking framework, which applies artificial potential to obtain target trajectory and MPC with PID feedback to effectively track planned trajectory. The experimental and simulation results are then presented to demonstrate the improved performance in tracking accuracy and steering smoothness compared to that of the conventional MPC control. Especially during negotiating a curve, its steady state error is close to 0.

Investigation of Gear Ratios for Hybrid System in Small Race Car Using Lap Time Simulation

To improve the dynamic performance of small racing hybrid vehicles which use an electric motor and engine, we proposed a hybrid system to synchronize these torques with simple composition. In this paper, the motor gear ratio and final gear ratio for optimizing the vehicle performance of a hybrid system in a small race car are investigated using lap time simulation. Specifically, we compared lap times on the evaluation circuit, a 400 m straight line, using the calculation method of a quasi-steady lap time simulation with a simplified vehicle model. In the paper, the hybrid system for a small race car is described, then the calculation method of the quasi-steady state lap time simulation is presented and the simulation results are discussed.

Quantitative Reliability Evaluation of Silicon Carbide-Based Inverters for Multiphase Electric Drives for Electric Vehicles

Abstract Reliability of power converter in the electric drivetrain of a vehicle can be a criterion for the comparison of various converter topologies, cooling system designs and control strategies. Therefore, reliability prediction is important for the design and control of vehicles. This paper presents an approach for quantitative evaluation of the reliability of converters for multiphase motor drives for electric vehicles (EVs) after considering the driving cycle. This paper provides a good background of reliability quantification so that it is easy to extend the presented approach to other applications. The models of subsystems have been selected to have excellent computational efficiency with good accuracy which is necessary for simulating long driving cycles. A simple vehicle model is used to obtain the traction motor torque demand for various points of the driving cycle. A multiphase interior permanent magnet synchronous motor has been used for traction motor. The operating voltage and currents of the motor are found using maximum torque per ampere (MTPA) control of IPMSM. The analytical loss calculation has been used to find the losses of switching devices of the converter. A thermal model of silicon carbide (SiC) MOSFET has been used to calculate junction temperature from the losses. The model developed here gives the failure rate and mean time between failures (MTBF) of switching devices of the inverter, which can be used to determine the failure rate. The model has been used to find the transition probabilities of a Markov model which can be used to quantify the reliability of converters of multiphase electric drives.

Discussion on Energy Propagation Model for Idling Vibration

In automotive development, it is important to determine a simple model for vehicle body at the early design stages. Much research has been done on initial design techniques called MBD (Model Based Development) and 1D CAE. In addition, it is also important to balance the various performances. In particular, idling vibration, engine shake, and road noise affect vehicle comfort. Coupling Loss Factor (CLF) is one of the parameters of Statistical Energy Analysis (SEA), and indicates that energy transmissibility, and provides design guidance in the early stages of design. Then in this paper, we construct a simplified vehicle model and perform frequency response function to obtain a guideline for reduction. Furthermore, the effectiveness of the energy transmissibility will be clarified by showing the same reduction guidelines. In addition, the effectiveness of the reduction guideline will be verified on the actual vehicle.

Application of Optical Measurement for Skin Friction Field around Tires of a Simplified Vehicle Model

The objective of this study is to apply the Global Luminescent Oil-Film Skin-Friction (GLOF) meter, which optically observes the skin friction vectors on the object surface, to reveal the fluid structure around the wheelhouse. The image analysis results show characteristic longitudinal vortices on the side surface of the front wheel and the wheelhouse. In contrast, the separation line at the rear end of the side near the rear wheelhouse is curved significantly upstream, and the separation area expands in the lower half of the rear end, probably due to the suction flow generated between the wheel and the wheelhouse.

Development and implementation of a time- and computationally-efficient methodology for reconstructing real-world crashes using finite element modeling to improve crash injury research investigations

Eleven Crash Injury Research and Engineering Network (CIREN) frontal crashes were reconstructed using a novel, time-efficient methodology involving a simplified vehicle model. Kinematic accuracy was assessed using novel kinematic scores between 0-1 and chest injury was assessed using literature-defined injury metric time histories. The average kinematic score across all simulations was 0.87, indicating good kinematic accuracy. Time histories for chest compression, rib strain, shoulder belt force, and steering column force discerned the most causative components of chest injury in all cases. Abbreviated Injury Scale (AIS) 2+ and AIS 3+ chest injury risk functions using belt force identified chest injury with 81.8% success.

Terrain Adaptive Trajectory Planning and Tracking on Deformable Terrains

In this work, a novel single-level adaptive trajectory planner and tracking controller is developed for off-road autonomous vehicles operating on deformable terrains. Trajectory planning and tracking algorithms often rely on a simplified vehicle model to predict future vehicle states based upon control inputs, hence requiring accurate modeling and parameterization. On off-road deformable terrains this is a challenging task due to unknown terrain parameters and the complex interactions at tire-terrain interfaces, which pose issues in continuous differentiability, operating conditions, and computational time. To address these difficulties, in this paper, a neural network deformable terrain terramechanics model and its implementation within a terrain adaptive model predictive control algorithm is presented to improve vehicle safety and performance through more accurate prediction of the plant response. It is shown in simulations that the neural network is able to predict the lateral tire forces accurately and efficiently compared to the Soil Contact Model as a state-of-the-art model and is able to yield accurate bicycle model predictions. It is demonstrated that the implementation of the neural network within model predictive control can outperform both a baseline Pacejka-based and a rapidly exploring random tree controller by improving performance and allowing for more severe maneuvers to be completed that otherwise lead to failure when terrain deformations are not explicitly taken into account. The improved performance achieved through estimating terrain parameters online in an adaptive controller is highlighted against the nonadaptive realization. Finally, it is shown the algorithm is conducive to real-time implementation.

A Review of Aerodynamics Influence on Various Car Model Geometry through CFD Techniques

The aerodynamic characteristics of a vehicle play a vital role in steering stability, performance, comfort, and safety of a car. The fuel efficiency of a vehicle is determined by the performance of the internal combustion engine and the aerodynamic design of the body. One of the most important aspects of automobile design is aerodynamic styling. A vehicle with low drag resistance provides advantages in terms of cost and efficiency. This article will review design characteristics and implementation of various specific reference models on drag issues using Computational Fluid Dynamics (CFD) techniques. The benefits and limitations of these models are analysed, and the validity of results in developing guidelines to improve the performance and stability of cars are described. This review paper covers significant studies that utilise the CFD model and simulation on a simplified vehicle model using various turbulence models to generate drag coefficient. Characteristics and impacts of various vehicle design models with and without external factors such as side mirrors and door handles are also discussed. Results obtained from the research focuses on the physics flow structures such as static pressure contours, are presented for the three types of car model geometry. The simplified generic models are more efficient and advocated to apply compared to the specific model geometry based on the result acquired by the latest studies. Simplified generic models are preferred due to their cost-effectiveness, procurement of optimum time, and better simulation effects. Moreover, the study also demonstrates the importance of having a car with suitable turbulence models that are appropriate to be applied for simulations in terms of its applicability, time effectiveness, and cost.

Vehicle interior noise and vibration prediction by combination analyses of Component and Operational TPA

In this study, we propose an analytical method consisting of Operational TPA (OTPA) and Component TPA (CTPA) to predict the vehicle interior noise and vibration without the vehicle operational test in case the noise source such as engine was modified. In the proposed method, the blocked force of the noise source was obtained at a test bench and the vibration at the source attachment point on the vehicle was calculated by CTPA. After then, the response point signal (interior noise / vibration) is estimated from several reference point signals including the calculated vibration by OTPA. For the verification of this method, a simple vehicle model which is composed of four tires and a motor was prepared in addition to a test bench. OTPA was firstly applied to the vehicle model to analyze the contribution from tires and a motor to the body vibration (response point). The blocked force of a modified motor was obtained by CTPA at the test bench and the force was used to predict the response point by OTPA. Finally, the estimated interior vibration was compared with the actual measured response point vibration when the motor was replaced on the vehicle model and the accuracy was verified.

Research on Curvilinear Motion of Automobile with the Application of On-Board Can Bus Data

Modelling of vehicle's motion is one of the solutions applied in the research of automotive safety. There is always a discussion which model should be used for computer simulation. Models with higher number of degrees of freedom require identification of many parameters, which are usually difficult to obtain. So, very often relatively simple flat model of vehicle's motion is applied. It needs only such parameters as mass of a vehicle, location of centre of gravity from front and rear axle, yaw mass moment of inertia and side slip characteristics of the front and rear axle. In this paper the upper mentioned model was applied, considering different side slip characteristics of the front and rear axle. The scenario of vehicle's motion was based on random changes of steering wheel angle during the road test, recording signals from on-board CAN (Controller Area Network) bus of automobile simultaneously, which were further applied in simulation.

Modular estimation of lateral vehicle dynamics and application in optimal AFS control

The paper introduces a novel modular estimation approach for lateral vehicle and tire dynamics using a simplified vehicle model and a non-linear estimation algorithm. A dynamics-oriented representation of lateral tire forces with a single track lateral vehicle model (STVM) has been introduced. Subsequently, extended Kalman filter (EKF) based distributed observer modules for each dynamical parameter has been designed and combined into a Unified Estimation Scheme (UES). Finally, a linear quadratic regulator (LQR) based Active Front Steering (AFS) control system has been designed using the estimated parameters. The accuracy and computational efficiency of the designed scheme has been analyzed and compared to non-modular UKF, EKF, and Particle Filter (PF) algorithms, through Monte-Carlo Simulations using the CarSim dataset for both high and low [Formula: see text] surfaces, followed by further validation using real-time dataset. The results show that the proposed system significantly improve the accuracy and speed of estimation, as well as stable performance in closed loop control.

Numerical investigation on the contribution of underbody flow-induced noise on vehicle interior noise

Aerodynamic noise transmitted through greenhouse panels and sealing often dominates the higher frequencies of the interior noise level, whereas the underbody area contributes mainly to low and middle frequencies. A method that unsteady Computational Fluid Dynamics (CFD) for exterior airflow combined with Finite Element Method (FEM) for interior acoustic response was used. To validate the accuracy of this method, the interior wind noise of a simplified vehicle model proposed by Hyundai was computed. The comparison between the computational and experimental result showed that this method had enough accuracy to compute the interior wind noise induced by the exterior flow field. Then, the same method was used to compute the wind noise transmitted through the underbody of a passenger car. The characteristic of the noise source and noise inside the cabin was revealed, and the contribution of underbody flow-induced noise to the interior noise was also investigated. Finally, the influence of the underbody panels thicknesses on the interior wind noise was evaluated.

Improved lateral-dynamics-intended railway vehicle model involving nonlinear wheel/rail interaction and car body flexibility

To study the vehicle hunting behavior and its coupling with car body vibrations, a simplified lateral-dynamics-intended railway vehicle model is developed. A two-truck vehicle is modeled as a 17 degrees-of-freedom rigid system, into which the car body flexural vibrations of torsion and bending modes are further integrated. The wheel/rail interaction employs a real-time calculation for the Hertzian normal contact, in which the nonlinear curvatures of wheel and rail profiles are presented as functions of wheelset lateral movement and/or yaw rotation. Then the tangential/creep forces are analytically expressed as the Hertzian contact patch geometry, and lead to a continuous and fast calculation compared to a look-up table interpolation. It is shown that the hunting frequencies of the vehicle model and a truck model differ significantly, which verifies the necessity of the whole vehicle model. In the case of low wheel/rail conicity, the hunting frequency increases linearly with vehicle speed, whereas it rises slowly at high speed for a large conicity. Comparison of hunting frequency and damping ratio between various conicities shows that first hunting (car body hunting) may occur when the vehicle is operated at a low speed in a small conicity case, while a second hunting (truck hunting) appears when the vehicle is operated at a high speed in a large conicity case. Stability analysis of linear and nonlinear vehicle models was carried out through coast down method and constant speed simulations. Results tell that the linear one overestimates the lateral vibrating. Whereas the structural vibrations of car body can be ignored in the stability analysis. Compared to existing simplified models for hunting stability study, the proposed simplified vehicle model released limitations in the nonlinear geometries of wheel/rail profiles, and it is suitable for a frequency-domain analysis by deriving the analytical expressions of the normal and tangential wheel/rail contact forces.

A roll frequency design method for underframe equipment of a high-speed railway vehicle for elastic vibration reduction

Field measurements of the elastic vibration of a car body (CB) and its coupling with the underframe equipment vibration were carried out for a high-speed railway vehicle, it was found that there was a significant increase of CB elastic vibration when passing a particular location and the equipment absorbed little of the CB vertical elastic vibration. In order to reduce the CB elastic vibration, the suspension parameters of the underframe equipment in the roll direction were optimized. A simplified vehicle model including the roll motion of the CB and the underframe equipment was built for theoretical study, in which the modal displacement of the CB floor corresponding to the CB diamond mode was extracted from finite-element analysis. Based on the frequency response analysis, the frequency range in which the elastic vibration was magnified was obtained. By increasing the roll moment of inertia of the equipment and decreasing lateral distance between the suspension points, the roll frequency of the underframe equipment was decreased and the CB vibration was reduced. To verify the analysis, a three-dimensional multi-body dynamic railway vehicle system was established in SIMPACK. The optimized parameters were validated and shown to be effective for absorbing the CB diamond-mode elastic vibration.

The effect of rear cavity modifications on the drag and flow field topology of a Square Back Ahmed Body

This work presents a numerical investigation of turbulent flow over a simplified vehicle model called the Square Back Ahmed Body (SBAB). The simulations are performed at Reynolds number 1 × 105 using the k − [Formula: see text] SSTSAS turbulence model. The numerical results for the standard reference model, that is, SBAB, have been validated against available experimental data and numerical simulations. The performance of a passive flow controller with four variants on the mean wake topology and the resultant drag reduction is evaluated. The four variants are; (i) straight cavity, (ii) straight cavity with rounded edges, (iii) C-shaped cavity, and (iv) tapered cavity. For a straight cavity with a depth equal to 33.33% of the body height, drag is lowered by 5.63%. With the same cavity depth, rounding the straight cavity edges reduces the drag by 10.67% owing to the streamlining and shortening of the recirculation region. For a C-shaped cavity, the amount of drag reduction increased slightly by 1% more than that off straight cavity with rounded edges, due to improvement in the base pressure distribution compared to that of the latter case. Tapering the cavity edges at an angle of 6° gave a significant drag reduction of 22.55% primarily due to a tremendous decrease in wake size. The drag reduction achieved in all the cases results from the modification in the mean wake topology induced by afterbody shape remodeling. The power spectra of the evolution of the lift coefficient over time reveal a noticeable decrement in the flow randomness with the inclusion of a cavity and its modifications, which interprets the mitigation of the chaotic nature in the wake. The cavity presence has also increased the vorticity spreading rate in the mixing layer and produced significant attenuation of Turbulent Kinetic Energy (TKE).

Three-Dimensional Path-Following Control for an Underwater Vehicle

This paper addresses the problem of guidance and control of an underwater vehicle. Guidance and control is achieved by introducing a control architecture with three modules: path generation, path following, and vehicle autopilot. This paper provides a formulation for the path-following algorithm, featuring an easily adjustable parameter that affects how aggressively the vehicle converges to a desired path. The framework for the path-following algorithm is built upon the Special Orthogonal Group SO(3) and introduces a path-following variable that allows the position of a target point moving along the desired path to be adjusted according to a specified control law. This paper derives guaranteed performance bounds of the path-following algorithm and considers limits on the vehicle’s angular rates, as well as limited performance of the vehicle autopilot. The resulting convergence properties are demonstrated with simulations using both a simple vehicle model and a vehicle modeled using computational fluid dynamics.

Self-Organizing Neuro-Fuzzy Control for Underwater Robotic Vehicles.(Dept.E)

Underwater robotic vehicles have become an important tool for various underwater tasks because they have greater speed, endurance and depth capability, as well as a higher factor of safety, than human divers. However, most vehicle control system designs have been based on a simplified vehicle model, which has often resulted in poor performance because the nonlinear and time-varying vehicle dynamics lave parameters uncertainty. It is desirable to have an advanced control system with the capability of learning and adapting to change in the vehicle dynamies and parameters. The proposed system is possessing neural network's learning ability. There are no rules initially in the proposed system. They are created and adapted as on-line leaning proceeds via simultaneous structure and parameter identification. The identification process of the controller includes both structure and parameter learning.