Mobility and Vehicle Mechanics

1-18

Authors: Rajko Radonjić Aleksandra Janković

This paper examines contemporary research and educational problems in automotive industry. In terms of perception and better understanding of the complex interdependence of this issue the block diagram is formed of the man-vehicle interaction in three important observation segments: (1) vehicle development through history, (2) phases of creating the vehicle and its life expectancy, (3) influence of the vehicle on human life. Functions of education and research and their complex interdependence are observed within the mentioned second segment of the block diagram – that is, „phase of the life expectancy of the vehicle“. The following is pointed out: multidisciplinarity of this issue, typical vehicle characteristics considering appropriate species of traffic systems, and transfer of knowledge and technologies in the land-air traffic. Within land transport road traffic is especially in focus and the mentioned current problems in the aspect of research and education. Thereby, special attention is given to the problem of the vehicle control in the complex system of the road traffic that is cybernetic system driver-vehicle-roads-surroundings. This problem is illustrated by the results of the specific researches that signal the complexity of the issue, multidisciplinarity, current measurement equipment need, it is also illustrated by the examination of the contemporary disciplines etc. Basing on the general situation and trends in the world and the current problems in Serbia, as well as the approach in this paper, it is possible to critically analyze the past and the current condition in the subject areas with more realistic designs of the future condition and taking the necessary measures in order to improve it.

39-51

Authors: Nenad Miljić, Slobodan J. Popović, Marko Kitanović

Engine speed signal contains valuable and rich content information about the engine working process. Measurement of the engine speed is usually carried out by sensor wheels mounted on the crankshaft. Measurement errors are mostly influenced by geometric tolerances of the engine speed sensor wheel as well as by its radial run-out. In order to avoid the occurrence of this systemic deviation, in the lab and highest accuracy engine speed measurements are usually conducted by means of incremental encoders, radially and axially fixed to the crankshaft with the anti-twist safeguard toward the crankcase. This paper shows how this type of engine speed measurement, which is considered to be the most accurate, is prone to systematic errors as well. The influence of the kinematic parameters of the encoder - crankcase linkage, on the error occurrence is discussed as well as suggested methods for systematic deviation parameters identification and engine crankshaft angular speed error compensation.

63-71

Authors: Mirko Blagojević, Zorica Đorđević, Miloš Matejić, Nenad Kostić, Nenad Petrović

Cycloidal speed reducer is a very complex mechanical system and for studying its dynamic behaviour must be considered all its specifics. On the level of internal dynamic forces very big impact have: manufacturing errors of cycloid disc and other elements of reducer, assembly errors, unequal load distribution, ... On the basis of the models of external and internal gear trains, a dynamic model of a single - stage cycloidal speed reducer is developed in the paper. It is assumed that the values of the stiffness are constant and the excitation force time-variable function. The values of displacement, velocity, and dynamic force for single meshing are presented in this paper. The greatest impact on the dynamic force value has the coefficient of damping and coefficient of stiffness between cycloid disc and the ring gear.

1-10

Authors: Đorđe Vranješ, Branimir Miletić

Traffic accidents present one of the most causes for child injuries in many countries, and almost 50% of all children up to 14 years have been killed in traffic accidents like passenger in vehicle. To prevent that, many car manufactures are developed different protection systems in cars, especially safety belts and child protection seats. Research studies have been investigated the impact of different factors to child restraint systems using level and set different risk levels associated with using or not using protection systems in vehicles. In addition, some studies also investigated how gender, education level, number of passengers, cultural and social characteristics in some areas, length of destination and other factors influenced on child restraint using level. Taking that, in this work we show some important investigation methods, results and recommendations for future investigations which will provide basis for taking measures for improvement of child restraint using systems in vehicle.

19-31

Authors: Duško Pešić, Emir Smailović, Nenad Marković

In the analysis of traffic accidents is one of the many tasks set before an expert traffic engineering profession is properly calculate or estimate deceleration motor vehicles that were involved in the accident. The problem becomes much simpler if done immediately after the accident inspection, and the court records are no data on the measured braking forces. However is not uncommon for a person who performs inspection data is entered on the weight of the vehicle when performing emergency technical inspection. As usual site investigation documentation contains information on vehicle weight, or information on the type of engine and associated equipment, it comes to the situation where the measured brake forces of vehicles, while data on vehicle weight cannot be determined. Considering to the weight of the same brand and type of vehicles can vary more than 500 kg, depending on the type of engine and equipment, it is also the maximum value of the braking coefficient, and therefore the maximum speed of the vehicle to trace braking can differentiate and more than 30 km/h. Depending on the used vehicle weight, will depend on the calculated speed of the braking trace, and therefore possible gaps participant accident.

53-63

Authors: Slobodan Mišanović, Vladimir Spasojević

The consumption of fuel is important indicator and aspect in operation of buses for public transportation. During the tender procedure for the procurement of new buses, fuel consumption is presenting one of the evaluation criteria in order to optimize the operating costs of the vehicle during its life cycle. Since 2009, in the EU as official methodology for measuring the fuel consumption of buses for urban - suburban transport, is used SORT methodology. The methodology is a simulation of real traffic conditions: acceleration, deceleration, stopping, vehicle load, measuring the amount of fuel consumed and processing results on the specially prepared test site for city, intercity and combined cycle. This paper shows the methodology SORT 1 (urban cycle) and the results of tests on five buses of GSP ''Beograd'', brand ''Solaris Urbino 18'', which were conducted in February and March of 2014, on the proving ground ''Santa Oliva'' ( Spain ) by certification body ''Applus Idiada''. Also, will be presented a comparative view of fuel consumption for buses ''Solaris Urbino 18'' in real operating conditions on the routes are served by GSP ''Beograd''.

7-21

Authors: Dragoljub Radonjić

Analysis and comparison of the comparative cycles is of great importance in assessing the effectiveness and efficiency of actual cycles of internal combustion engines. In conventional combustion engines are used the three main comparative cycles: otto, diesel and dual. The development of internal combustion engines, by applications: the new system of mixture formation (GDI, HCCI), variable valve timing, overboost system and aftertreatment of exhaust gases, bring to modification of the real working cycle, but also the need to introduce new comparative cycle such as Atkinson, Miller, Gruden and HEHC cycles. Previous methods of analysis and comparison of the ideal cycle is reduced to the determination of the expression of specific work and thermal efficiency of each cycle as a function of the characteristic parameters, adopting the criteria of comparison and finally, comparison of the specific work and efficiency of the given cycle at different values of the selected parameter. This paper presents a new method of comparison based on the application of the general thermodynamic cycle (GTC), introduced by the author. From the general thermodynamic cycle, in particular procedures can be carried out, all possible cycles for converting heat into work (total: 130), and by determining the expression of specific work and efficiency of this cycle and placing them in appropriate conditions can obtain expressions for the specific work and efficiency of each cycle. On the basis of these procedures has been developed a software package that provides graphical views of the following characteristics of the selected cycle: P-v and T-s diagrams, changes the specific work and thermal efficiency as a function of the desired dimensionless parameter, as well as the comparison of two or more cycles according to proposed criteria.

37-54

Authors: Zoran Nikolić, Zlatomir Živanović

First Electric Vehicle (EV) has been made in in 1837. This type of motor vehicles has dominated throughout the whole 19th century. In the early 20th century the faster and more robust vehicles with Internal Combustion Engine (ICE) overcame them until late 20th century, when ecological and economic problems of further application of these vehicles have emerged. The interest in EV has risen sharply. Researches are working in several directions in order to reduce the need for oil derivatives considering that the EV's are weak primarily due to inferior "reservoir of energy" to fully meet the current driving habits. Savings can be achieved in two ways, by making more economic motor vehicles or by the use of alternative fuels. Combining an electric propulsion and IC engine drives a hybrid vehicle is obtained, with a greater amount of batteries and "plug in" that is to some extent possible to reduce fossil fuel consumption and exhaust emissions. Intensive research work on exploring new battery is still to come. Today promising results with Li - air batteries, fuel cells and super capacitors, as well as the efforts of major car manufacturers indicate that the EV could soon appear massive in the streets of cities. This paper deals with the development of EV, following the development of powertrain and can conclude the fact that in the near future this type of drive could return.

63-77

Authors: Dobrivoje Ćatić, Jasna Glišović, Sandra Veličković, Jasmina Blagojević, Marko Delić

Weibull distribution is one of the most frequently used theoretical models for approximation of empirical distributions of random variables with continuous variation. Procedures for graphical, grapho-analytical and analytical determination of Weibull distribution parameters are described in detail in this paper. Based on the graphical method for determining the position parameters of three-parameter Weibull distribution, the analytical procedure is developed, which is based on the application of the method of least squares. The set of points is approximating with the square parabola, and based on the sign of the second derivative, the information for further proceedings is obtained. For the defined procedure, an algorithm of the computer program for determination of the Weibull distribution parameters is presented in paper. By using the program, based on data from the exploitation related to the operation time until failure, the reliability modelling of wheel’s drum in braking system of light commercial vehicles was performed. The graphical and non-parametric tests were used to test the theoretical model of distribution.

7-27

Authors: Dobrivoje Ninković

Since the first patent granted in 1905 to the Swiss engineer A. Büchi for utilizing the IC engine exhaust gas energy for driving a turbine compounded with the engine, which is generally understood as the basis for the introduction of turbocharging, the latter has enjoyed a steady development first in the large Diesel engine segment, where it brought about efficiencies of 55%, becoming nowadays the indispensable technology for further progress in the field of IC engines in general. Surveyed in the lecture is the development of the turbocharging concepts and realizations in the large engine field, where it matured and formed thus the basis for the introduction of the technology to the engines used to propel road vehicles. Although turbocharging is still an active R&D subject in the large engine segment, it is apparent that the main activities are now to be found in the field of small engines. The role of turbocharging as a means for further increasing the specific engine power, reducing both the production of CO2 and the emission of pollution gases detrimental to the environment while simultaneously improving driveability of the vehicles, is also discussed. Finally, an overview is presented of the current development trends in this area.

47-59

Authors: Josip Vlahović

The passenger vehicle today is modern and highly equipped. Already in the basic version, it has a servo steering, power brakes, Antilock Braking System, Electronic Stability Control, air bag, etc. It has crash safe and dynamically robust body. Body corrosion resistance is significantly better. Engines consume less, and yet (and nevertheless) the emission is nearly 100 times cleaner than 30 years ago. In any case, the passenger cars today are much better, safer, more reliable and environmentally friendly. They became larger and heavier, but they are fulfilling all requirements. All this is possible through the application of new methods of body construction, by application of the know-how in new production technologies and through application of the new metallurgical classes of Steel and Aluminium. There are also new plastics and composites, too. Great progress has been made in electronic monitoring and control of vehicle systems. Today, on the market, there are vehicles with automatic control. Future cars will soon not need a driver. On the other hand, new limitations on the road, like speed limits, are coming more and more. Congestions on roads would lead toward more speed limits. Because of these, it is quite difficult to say how would passenger cars look like in the future? It could happen that private cars would be controlled from some control centre.

79-88

Authors: Dušan Arsić Vukić Lazić Srbislav Aleksandrović Dragan Milosavljević Božidar Krstić Petar Marinković Milan Đorđević

There is constant tendency of engineers to decrease a weight of vehicles and to increase their capacity and mobility. Parallel with development of high strength steels, which starts in 90's years of last century, starts their application in industry for producing motor vehicles with special purpose (construction mechanization vehicles, fire and military vehicles, etc.). With increase of strength of used materials there are conditions for using lower thickness of cross sections what have direct influence to the weight reduction. With respect to that, one of the most used method for producing that kind of structures is welding, in this paper is analysed the weldability of used HS steel and it is proposed the optimal welding technology for welding HSS class S690QL. The assemblies and parts on one military vehicle are made of that steel. The optimal welding technology should preserve good mechanical properties in weld metal, transition zone and in HAZ as the most critical zone of the welded joint.

7-27

Authors: Stojan Petrović, Velimir Petrovic

This paper presents an overview and analysis of European regulations related to the emissions of passenger and heavy-duty vehicles. After introduction, wich summurizies the problem of motor vehicle exhaust emission, addopted European adopted emission standard are presented with special attention on newly introduced mesurement of particle number concentration. Then, the emphasis has been put on world harmonization of emission control procedures and the establishment of the so-called Global Technical Regulation (GTR). In addition to the already adopted global harmonization of regulations and procedures for the assessment of emissions related to motorcycles (GTR 2), heavy vehicles (GTR 4) and non-road vehicles (GTR 11), special attention is paid to the new global regulation relating to the passenger cars (GTR 15). Finally, the paper analyzes the possibility of real driving emissions (RDE) measurement under consideration in EU and two possibilities are mentioned. Special attention is paid to the application of portable emission measurement system (PEMS) for testing vehicles paricle emission under real driving conditions.

55-68

Authors: Snežana Petković

Technical inspection of vehicles has been identified worldwide as an essential element of road safety and accident prevention. The conclusion is, nonetheless, that very little is known about the effect of unroadworthy vehicles on road accidents. It is why many international studies have been conducted in order to determine the effect and also to introduce new methodologies for vehicle inspections that would reduce the number of road accidents. This paper presents the results of international studies on the influence of vehicle technical inspection on road safety, and it also describes actions that have been implemented in the Republic of Srpska with the aim of improving road safety and roadworthiness.

85-96

Authors: Saša Milojević Nenad Ilić Radivoje Pešić

Fuel can be dangerous if handled improperly. Gasoline and diesel are potentially dangerous fuels, but over time we are learned to use them safely. The same is true with liquefied petroleum gas and natural gas. The hydrogen is suitable as a fuel for vehicles powered with both, internal combustion engines or indirectly for electric engines inside of fuel cell propulsion systems, too. The problems associated with the production and storage of hydrogen currently limits the application of pure hydrogen as engine fuel in vehicles. This paper represents our designing proposition of a low-floor city bus for hydrogen power. For application inside of low-floor city buses, hydrogen cylinders have to be installed on the roof for reasons of space. In addition, regarding to the lack of available information, the paper demonstrates an overview about safety regulations for vehicles with regard to the installation of specific components in hydrogen fuel line.