Design and evaluation of sideslip angle observer for vehicle stability control

This paper presents a method for estimating the vehicle side slip angle, which is considered as a significant signal in determining the vehicle stability region in vehicle stability control systems. The proposed method combines the model-based method and kinematics-based method. Side forces of the front and rear axles are provided as a weighted sum of directly calculated values from a lateral acceleration sensor and a yaw rate sensor and from a tire model according to the nonlinear factor, which is defined to identify the degree of nonlinearity of the vehicle state. Then, the side forces are fed to the extended Kalman filter, which is designed based on the single-track vehicle model associated with a tire model. The cornering stiffness identifier is introduced to compensate for tire force nonlinearities. A fuzzy-logic procedure is implemented to determine the nonlinear factor from the input variables: yaw rate deviation from the reference value and lateral acceleration. The proposed observer is compared with a model-based method and kinematics-based method. An 8 DOF vehicle model and Dugoff tire model are employed to simulate the vehicle state in MATLAB/SIMULINK. The simulation results shows that the proposed method is more accurate than the model-based method and kinematics-based method when the vehicle is subjected to severe maneuvers under different road conditions.     

A finite element model for flexible pipe armor wire instability

The constructive disposition of metallic and plastic layers confers flexible pipes with high and low axial stiffness respectively when tensile and compressive loads are applied. Under certain conditions typically found during deepwater installation or operation, flexible pipes may be subjected to high axial compression, sometimes accompanied by bending. If not properly designed, the structure may not be able to withstand this loading and fails. From practical experience observed offshore and in laboratory tests two principal mechanisms, which will be discussed in this paper, have been identified regarding the configuration of the armor wires. When the pipe fails by compression the armor wires may exhibit localized lateral or radial deflections, consequently permanent damage is observed in the armor wires with a sudden reduction of the structure’s axial stiffness. The pressure armor may also unlock, thus causing potential fluid leakage.In this work a finite element model is developed to estimate the critical instability load and failure modes. An axi-symmetric model is constructed employing a complex combination of beam and spring elements. For each armor layer only one wire needs to be modeled, hence the computational cost is minimized without compromising the phenomenon characterization. A parametric case study is performed for a typical flexible pipe structure, where the friction coefficient between the wire armors and the external pressure are varied, and the critical instability loads and failure modes are obtained and results are discussed.     

Integration of a single cylinder engine model and a boost system model for efficient numerical mapping of engine performance and fuel consumption

A numerical engine mapping methodology is proposed for the engine performance and fuel consumption map generation. An integrated model is developed by coupling a single cylinder GT-Power® engine model with a MATLAB/ Simulink® based boost system model to simulate a turbocharged diesel engine over the entire engine operating speed and load ranges within reasonable computational constraints. A single cylinder engine model with the built-in multi-zone combustion modeling option in GT-Power® is configured as a predictive engine model. The cycle averaged simulation result from the engine model is used as the boundary conditions of the boost system including intake and exhaust manifolds and a turbocharger. The boost system model developed in MATLAB/Simulink® platform calculates the intake and exhaust conditions which are fed back to the engine model. The integrated system model predicts the performance and fuel consumption of a turbocharged diesel engine with better predictive capability than mean value engine models. Its computational time is fast enough to simulate the engine over the entire engine operation range compared to multi-cylinder engine models.     

Possible experimental method to determine the suspension parameters in a simplified model of a passenger car

Currently, as well as in the past, researchers have shown great interest in developing suspension systems for vehicles and especially in the design and optimization of the suspension parameters, such as the stiffness and the damping coefficient. These parameters are considered to be important factors that have an influence on safety and improve the comfort of the passengers in the vehicle. This paper describes a simplified methodology to determine, in a quick manner, the suspension parameters for different types of passenger cars equipped with passive suspension systems. Currently, different types of passenger cars are produced with different types of suspension systems. Finding a simplified methodology to determine these parameters with sufficient accuracy would contribute a simplified and quick method to the inspection of the working conditions of a suspension system. Therefore, a simple system to determine these parameters is needed. An analysis of the suspension parameters is performed using mathematical modeling and numerical analysis conducted using the Working Model software. The result derived from the developed methodology shows small errors when compared with the generic values, and it can be concluded that the design of the suspension parameter measurement device using the developed methodology is useful, simple, and has sufficient accuracy.     

Fuzzy energy management strategy for a hybrid electric vehicle based on driving cycle recognition

By considering the effect of the driving cycle on the energy management strategy (EMS), a fuzzy EMS based on driving cycle recognition is proposed to improve the fuel economy of a parallel hybrid electric vehicle. The EMS is composed of driving cycle recognition and a fuzzy torque distribution controller. The current driving cycle is recognized by learning vector quantization in driving cycle recognition. The torque of the engine and the motor is controlled by a fuzzy torque distribution controller based on the required torque of the hybrid powertrain and the battery state of charge. The membership functions and rules of the fuzzy torque distribution controller are optimized simultaneously by using particle swarm optimization. Based on the identification results of driving cycle recognition, the fuzzy torque distribution controller selects the corresponding membership function and rule to control the hybrid powertrain. The simulation research based on ADVISOR demonstrates that this EMS improves fuel economy more effectively than fuzzy EMS without driving cycle recognition.     

Forme urbaine et mobilité domicile-travail dans 13 aires urbaines françaises : une analyse multiéchelle

This article provides a multi-scale analysis of the links between commuting patterns and urban form by using both morphological and more classical indicators of urban form (like density). Thirteen French urban areas of more than 500,000 inhabitants (excluding Paris) are compared. The findings highlight the complexity of the links between urban form and commuting patterns because the same indicators of urban form do not have the same influence according to the spatial scale. Even if the influence of the morphological indicators is lower than that of more classical socioeconomic variables (income level, motorization rate), our study discusses the various and multi-scale consequences of urban development on daily travel behaviour.     

Simulation of wind-driven circulation in the Gulf of Elat (Aqaba)

The Princeton Ocean Model (POM) has been used to investigate the wind-driven circulation in the stratified long and narrow Gulf of Elat (Aqaba). Our results indicate that the circulation consists of a series of gyres aligned along the main axis of the basin, and that their size and location are strongly affected by the shoreline and, to a lesser extent, by the hydrography. The seasonality in both the flow and the free surface height (FSH) at any specific station are caused mainly by the strong seasonality in the hydrography — the FSH and the magnitude of the currents above the thermocline are inversely related to the thickness of the upper layer. The seasonality in the flow is also manifested in the location and diameter of the gyres. This seasonal change in the gyres' diameter and location might provide an explanation for the current reversal observed at the northern tip of the western boundary during the month of February.     

Recent technical and management improvements in US inland waterway transportation

Over the last several years, the US inland waterway transportation industry has significantly reduced its fuel consumption and improved its efficiency, with the side effect of less fuel tax collected per ton of cargo carried, despite the increase in cargo traffic. Fuel tax revenues are used for rehabilitation and construction projects in the inland waterway system, hence the US Army Corps of Engineers, providing us with relevant data over the interval in question, asked us to investigate this surprising reduction, and determine the main technical and fleet management improvements that caused it. Our research involved both visits with most major US inland waterway fleets, interviews with their engineers and managers, as well as statistical analysis of the above data. Technical improvements (such as engine plant efficiency increases), lighter, stronger building materials (such as light steel), and improved designs for better hydrodynamics, were not as important compared to management improvements (such as the use of computer-aided monitoring systems and advanced telecommunications, optimized tow configuration and speed, and increased triangular trips as opposed to simple round trips with returns empty). In addition, the demand for less expensive, imported steel for the US has resulted in an increased percentage of fully loaded return trips from New Orleans to the US Midwest, and hence also in increased fleet utilization.     

Maritime economics: Problems and challenges for the future

The light is always identical in its composition, but it falls on a great variety of objects, and by so falling is first revealed to us, not in its own form, for it is formless, but in theirs; in like manner, thought only appears in the objects it classifies.