Automotive Engineering

Fren kuvveti uygulanan tekerlek aracın hızına uygun olmayan şekilde yavaş dönerse bu olaya kayma denir. Serbest dönen tekerlek %0 kaymalıdır. Kilitlenmiş olan tekerleğin kayması % 100'dür. En ideal fren durumu tekerleğin durduğu anda değil lastik ve zemin durumuna göre %10 veya %50 kayma durumudur. İstenilen kaymanın elde edilebilmesi için gerekli fren basıncı lastik ile yol arasındaki bağlantı kuvvetine bağlıdır. Bu kuvvet katsayısı kuru zeminde yüksek , ıslak zeminde daha düşük , buzlu zeminde çok düşük bir değerdir. ABS bütün bu zemin durumlarına uyum sağlayarak tekerlekleri istenilen kayma aralığında tutmayı amaçlar. Islak veya kaygan zeminde sürücü aniden frene bastığı zaman aracın kayması çok kolaydır. Frenlerin aniden devreye sokulması tekerleklerin kilitlenerek kaymasına neden olur. Araç hareketine devam etmekle kalmaz, istikamet dengesi ve direksiyon hâkimiyeti de kaybolur. Böyle bir durumda aracın frenleri devamlı değil, ara ara pompalayarak aracın dengesini korunabilir ve böylece direksiyon hâkimiyeti kaybedilmez. Ancak bu durumda da durma mesafeniz çok artar. Bu sakıncaları ortadan kaldırmak için araçlarda ABS (Anti-Lock Brake System) kullanılmaktadır. ABS genel olarak, kaygan zeminlerde ani ve stabil bir şekilde durmayı sağlayan fren sistemi olarak tanımlanır. Kaygan bir zeminde acemi bir sürücü eğer aracında ABS sistemi varsa, ABS olmayan usta bir sürücüye göre çok daha rahat ve erken durabilir. Sistem bilgisayar kontrollü çalıştığından sürücü sadece frene basılı tutar, gerisini sistem otomatik halleder.

Objective: Human body finite element models (FE-HBMs) are available in standard occupant or pedestrian postures. There is a need to have FE-HBMs in the same posture as a crash victim or to be configured in varying postures. Developing FE models for all possible positions is not practically viable. The current work aims at obtaining a posture-specific human lower extremity model by reconfiguring an existing one. Methodology: A graphics-based technique was developed to reposition the lower extremity of an FE-HBM by specifying the flexion–extension angle. Elements of the model were segregated into rigid (bones) and deformable components (soft tissues). The bones were rotated about the flexion–extension axis followed by rotation about the longitudinal axis to capture the twisting of the tibia. The desired knee joint movement was thus achieved. Geometric heuristics were then used to reposition the skin. A mapping defined over the space between bones and the skin was used to regenerate the soft tissues. Mesh smoothing was then done to augment mesh quality. Results: The developed method permits control over the kinematics of the joint and maintains the initial mesh quality of the model. For some critical areas (in the joint vicinity) where element distortion is large, mesh smoothing is done to improve mesh quality. Conclusions: A method to reposition the knee joint of a human body FE model was developed. Repositions of a model from 9 degrees of flexion to 90 degrees of flexion in just a few seconds without subjective interventions was demonstrated. Because the mesh quality of the repositioned model was maintained to a predefined level (typically to the level of a well-made model in the initial configuration), the model was suitable for subsequent simulations.

The state estimation and the analysis of load flow are very important subjects in the analysis and management of Electrical Power Systems (EPS). This article describes the state estimation in EPS using the Extended Kalman Filter (EKF) and the method of Holt to linearize the process model and then calculates a performance error index as indicators of its accuracy. Besides, this error index can be used as a reference for further comparison between methodologies for state estimation in EPS such as the Unscented Kalman Filter, the Ensemble Kalman Filter, Monte Carlo methods, and others. Results of error indices obtained in the simulation process agree with the order of magnitude expected and the behavior of the filter is appropriate due to follows adequately  the true value of the state variables. The simulation was done using Matlab and the electrical system used corresponds to the IEEE 14 and 30 bus test case systems. State Variables to consider in this study are the voltage and angle magnitudes.

Real-time simulations refer to the simulations of a physical system where model equations for one time-step are solved within the same time period as in reality. An FPGA/CPU-based real-time simulation platform is presented in this paper, with a full-electric vehicle model implemented in a central processing unit (CPU) board and an electric drive model implemented in a field programmable gate arrays (FPGA) board. It has been a challenge to interface two models solved with two different processors. In this paper, one open-loop and three closed-loop interfaces are proposed. Real-time simulation results show that the best method is to transmit electric machine speed from the vehicle model to the electric derive model, with feedback electric machine torque calculated in FPGA. In addition, a virtual vehicle testing tool (CarMaker) is used when building the vehicle model, achieving more accurate modeling of vehicle subsystems. The presented platform can be used to verify advanced vehicle c...

Published: 1 Sept , 2019 Today most accidents are caused by drivers’ fatigue, drowsiness and losing attention on the road ahead. In this paper, a system is introduced, using RGB-D cameras to automatically identify drowsiness and give warning. In this system two important modules have been utilized simultaneously to identify the state of driver’s mouth and eyes for detecting drowsiness. At first, using the depth information, the mouth area and its state are identified. Then using CNN networks, to predict whether the eyes are open or closed, a semi-VGG architecture is used .The results of yawning and eyes states detection are integrated to decide whether an alarm should be issued. The results show an accuracy of about 90% which is encouraging.

Fast charging is an essential stakeholder concern for achieving a deeper penetration of Electric Vehicles (EVs), as optimizing the charging times of conventional vehicles is as yet a bottleneck to be solved. An important drawback of EV’s fast charging lies in the degradation suffered by the Li-ion Batteries (LIBs) at high charging currents. A deep understanding of the how these fast-charging activities affect the LIBs’ degradation is necessary in order to design appropriate fast charging stations and EV powertrains for different scenarios and contexts. In this regard, the present paper analyzes the effect of fast charging on Libs’ degradation under operation profiles from real driving cycles. Specifically, Battery Electric Buses (BEBs) driving profiles from three demos in European Cities (Gothenburg, Osnabrück and Barcelona) have been used in this analysis. In order to deduce the best practices for the design of the charging stations, different sizes for the chargers have been simul...

Global opportunities in the auto industry have resulted in increases in production outside North America. This paper reports the results of a study in which a group of small automotive suppliers assessed the appropriateness of global entry strategies, and evaluated the degree of asset specificity and risks

Informing the users about their environment is of extreme importance for their full and independent functioning in the traffic system. Today's development of technology provides the user the access to information about their environment by using the smartphone device at any moment if there is a defined applicative solution. For this, it is necessary to define the user's environment according to the Ambient Assisted Living (AAL) concept, which understands adequate technology of gathering, processing and distribution of information. This paper presents the proposal of the solution for informing the traffic network users about the environment for the defined group of users based on the beacon technology. The mentioned solution is based on the results of two separate studies about the needs of users who move along a part of the traffic network. The aim of the proposed solution is to provide the user with precise and real-time information and to raise the level of safety during m...

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