Automotive Science and Engineering

Vehicle Directional Stability Control Using Bifurcation Analysis of Yaw Rate Equilibrium

M.H. Shojaeefard

In this article, vehicle cornering stability and brake stabilization via bifurcation analysis has been investigated. In order to extract the governing equations of motion, a nonlinear four-wheeled vehicle model with two degrees of freedom has been developed. Using the continuation software package MatCont a stability analysis based on phase plane analysis and bifurcation of equilibrium is performed and an optimal controller has been proposed. Finally, simulation has been done in Matlab-Simulink software considering a sine with dwell steering angle input, and the effectiveness of the proposed controller on the aforementioned model has been validated with Carsim model.

Studying Influence of Preheating Conditions on Design Parameters of Continuous Paint Cure Ovens

Z. Baniamerian

This paper concentrates on a new procedure which experimentally recognises gears and bearings faults of a typical gearbox system using a least square support vector machine (LSSVM). Two wavelet selection criteria Maximum Energy to Shannon Entropy ratio and Maximum Relative Wavelet Energy are used and compared to select an appropriate wavelet for feature extraction. The fault diagnosis method consists of three steps, firstly the six different base wavelets are considered. Out of these six wavelets, the base wavelet is selected based on wavelet selection criterion to extract statistical features from wavelet coefficients of raw vibration signals. Based on wavelet selection criterion, Daubechies wavelet and Meyer are selected as the best base wavelet among the other wavelets considered from the Maximum Relative Energy and Maximum Energy to Shannon Entropy criteria respectively. Finally, the gearbox faults are classified using these statistical features as input to LSSVM technique. The optimal decomposition level of wavelet is selected based on the Maximum Energy to Shannon Entropy ratio criteria. In addition to this, Energy and Shannon Entropy of the wavelet coefficients are used as two new features along with other statistical parameters as input of the classifier. Some kernel functions and multi kernel function as a new method are used with three strategies for multi classification of gearboxes. The results of fault classification demonstrate that the LSSVM identified the fault categories of gearbox more accurately with multi kernel and OAOT strategy.

A comparison of different network based modeling methods for prediction of the torque of a SI engine equipped with variable valve timing

A.H. Kakaee

Nowadays, due to increasing the complexity of IC engines, calibration task becomes more severe and the need to use surrogate models for investigating of the engine behavior arises. Accordingly, many black box modeling approaches have been used in this context among which network based models are of the most powerful approaches thanks to their flexible structures. In this paper four network based modeling methods are used and compared to model the behavior of an IC engine: neural networks model (NN), group method of data handling model (GMDH), a hybrid NN and GMDH model (NN-GMDH), and a GMDH model whose structure is determined by genetic algorithm (Genetic-GMDH). The inputs are engine speed, throttle angle, and intake valve opening and closing timing, and the output is the engine brake torque. Results show that NN has the best prediction capability and Genetic-GMDH model has the most flexible and simplest structure and relatively good prediction ability.

Numerical Study on the Crushing Behavior of Square Tubes Under Three Dimensional Oblique Loading

A. Khalkhali

This study aims to numerically investigate on the crashworthiness of thin-walled square tubes by consideration of 3-D oblique loading. In this type of loading, direction of loading is defined by using two spatial angles relative to the position of the tube. To this aim, finite element (FE) analysis is employed to simulate the loading for 8 different numerical models with different loading orientation. Subsequently, load-displacement diagrams as well as deformation shapes during the loading are derived for each model. Moreover, a study is done on the tube collapse mode for each case. Effect of loading orientation and tube thickness on the maximum crushing load and energy absorption are also studied via a parametric study on the FE simulations. Results indicated a different trend for all cases of 3D oblique loading compared to axial loading. This study highlights the significance of consideration of a 3D orientation in analysis of crushing behavior of thin-walled tubes.

Studying Simultaneous Injection of Natural Gas and Gasoline Effect on Dual Fuel Engine Performance and Emissions

A. Mirmohamadi

According to the Global Fuel Crisis, it seems necessary to use alternative fuel instead of gasoline. Since the natural gas is cheaper, have higher frequency than gasoline and less pollution, it is a suitable fuel. Many efforts have been done in order to replace gasoline with natural gas. One of the methods is to inject natural gas and gasoline fuel simultaneously and to use the benefits of both fuels. The purpose of this paper is studying natural gas and gasoline blend effect on engine power, torque and emissions. The simulated model was validated in different engine RPMs for gasoline and natural gas, were separately injected into the engine at full load condition. The results of simulation was had good agreement with experiments. The results show that by natural gas and gasoline Simultaneous injection power and torque have been reduced. NOX, HC and CO2 Pollutants change periodically, but their production level is generally lower than gasoline mode, but the CO pollutant increases.

The Effects of Changes in Height on the Aerodynamic Performance of Automobiles

H. Afshar

In this study, the fluid flow around a Pride vehicle was solved in a two-dimensional design using numerical methods. To do so, a two-dimensional figure of a Pride was modeled and gridded, and different surfaces were introduced. Then, governing equations the fluid flow was solved for the standard K-ε model and the appropriate boundary conditions. Areas that increased lift and drag forces were specified through studying the results and observing flow lines, pressure distribution, and vortices created around the automobile. In this way, the ideal height for different speeds was determined through examining the changes in those forces at different heights. In this study, the Pride was examined at different heights 80, 120, 160 (standard), 200, and 250 mm for the speeds 10, 20, 33, and 40 m/s. The results showed that lift and drag forces depended on the height of the automobile and changed at different heights