Vojnotehnicki glasnik / Military Technical Courier

29-40

Authors: Donevski Dragan V.

Nowadays, a number of light terrain wheeled vehicles are used for various purposes. Their basic performances are related to achieving high average speed off roads and to overcoming various obstacles. This type of vehicles is mainly used for commercial purposes. Models of these vehicles have been modernized and upgraded during the time but their basic purpose remains the same. However, nowadays there is a need to use these vehicles for other purposes. This is carried out through the process of conversion. The conversion means that a vehicle changes its purpose by the application of various technical solutions. One of conversions is related to the application of weapons on the vehicle chassis. The weapon mounting is connected with various problems such as vehicle stiffness, weapon precision, presence of various oscillations, overall vehicle layout and crew deployment. In order to mount weapons efficiently, the methodology of its selection is proposed. It consists of several phases and the most important of them are the following ones: the consideration of performances of modern light terrain wheeled vehicles, analysis of weapons convenient for application, creation of the vehicle-platform-weapon system mathematical model, analysis of the dynamic characteristics of the created model and the selection of the best solution, experimental research and analysis of theoretical and experimental results. The realization of the proposed methodology will considerably improve the quality of the design of vehicle- platform-weapon systems.

60-77

Authors: Ilić Slaviša M., Radosavljević Vladan R.

The paper has solved the problem of optimizing the existing inefficient and irrational system of the quantitative monitoring of the situation in peacetime fuel supplies at the pumping stations in the Army of Serbia. A study of existing organizational forms, military pumping stations as well as civilian ones, was carried out. Based on the completion of the survey by competent persons in the military, the methods of expert evaluation and the obtained quantitative indicator of the tested models, a multicriteria optimization was performed in order to select the optimal model. The optimization of the existing models, in terms of efficiency and economy, would be the rationalization and modernization - automation of military capacity and greater reliance on automated civilian pumping stations. Introduction Within the framework of the undergoing reform of the Serbian Army and in order to reduce the total costs, it is necessary to optimize the existing supply system that is technologically outdated, inefficient and uneconomic. The problem of research in this paper is reduced to the selection of an optimal model of the quantitative monitoring of the state of peacetime stocks of fuel at the pumping stations in the Serbian Army, in order to ensure economical operation and efficient monitoring of available and issued quantities, aiming at better decision making and management in the supply system as well as at achieving faster system response, with greater reliance on government logistics. Organization of work and monitoring the fuel quantitative status at pumping stations The existing system of monitoring the quantitative state of fuel pumping stations in the Army of Serbia has the following disadvantages: getting unreliable data, due to outdated equipment for fuel handling and measuring equipment, and manual collection of data; creation of unauthorized shortages (due to subjective human error or deception); inadequate engagement of respective material and human resources. Optimization of quantitative monitoring of peacetime supplies of fuel at gas stations should aim at reducing the impact of the human factor, introducing automated quantitative monitoring of fuel condition with modern equipment for handling as well as applying technology for fast reading and dissemination of information and reports. Civilian pumping stations have been modernized gradually with new digital pump machines, systems for automated production and automated systems for measuring the fuel level in buried tanks. The objectives and criteria of the optimization of model monitoring In order to solve the problem of multi-criteria nature, the methods of operational research have been applied and the formalization of problem solving has been carried out. Models have been identified, criteria and subcriteria have been defined as well as respective criteria values, sub-criteria and weight coefficients for chosen variants in order to rank the alternatives - models. On the basis of the defined objectives and optimization approaches, the task of optimization to be solved is to choose one optimal model of monitoring the quantitative condition of peacetime stocks of fuels at gas stations, out of three variations or alternative models. Application of expert assessment and methods of analytical hierarchy process The problem was solved first 'manually', by using MS Excell, and after that by using the Expert Choice software package. The Expert Choice software package is based on the application of the method of analytical hierarchy process and combines the benefits that this method offers with the speed and visibility of computerized calculations and their result display. The purpose of the AHP method is to rank alternative decisions by their importance and to select the most acceptable alternative on the basis of a defined set of criteria and alternatives. The problem of determining the weight of criteria has been determined by applying the method of expert evaluation, along with interviewing and taking into account the competence of the interviewees. Conclusion The existing solutions in the system of logistics support, focused on the monitoring of the quantitative status of peacetime fuel supplies at the pumping stations in the Serbian Army, are not the product of system analysis and optimization. Therefore, it is not rational for them to get an IT support. The continuous task should thus be to monitor the phenomena and problems and their formalized description in order to create a foundation for their automation and successful problem solving.

94-110

Authors: Sokolović Vlada S., Oklopdžija Milan N., Marković Goran B.

Introduction This paper presents a critical analysis of the signal processing flow carried out in a software GPS receiver and a critical comparison of different architectures for signal processing within the GPS receiver. A model of software receivers is shown. Based on the displayed model, a receiver has been realized in the MATLAB software package, in which the simulations of signal processing were carried out. The aim of this paper is to demonstrate the advantages and disadvantages of different methods of the synchronization of signals in the receiver, and to propose a solution acceptable for possible implementation. The signal processing flow was observed from the input circuit to the extraction of the bits of the navigation message. The entire signal processing was performed on the L1 signal and the data collected by the input circuit SE4110. A radio signal from the satellite was accepted with the input circuit, filtered and translated into a digital form. The input circuit ends with the hardware of the receiver. A digital signal from the input circuit is brought into the PC Pentium 4 (AMD 3000 +) where the receiver is realized in Matlab. Model of software GPS receiver The first level of processing is signal acquisition. Signal acquisition was realized using the cyclic convolution. The acquisition process was carried out by measuring signals from satellites, and these parameters are passed to the next level of processing. The next level was done by monitoring the synchronization signal and extracting the navigation message bits. On the basis of the detection of the navigation message the receiver calculates the position of a satellite and then, based on the position of the satellite, its own position. Tracking of GPS signal synchronization In order to select the most acceptable method of signal synchronization in the receiver, different methods of signal synchronization are compared. The early-late-DLL (Delay Lock Loop), TDL (Tau Dither Loop) and Costas's PLL (Phase Lock Loop) models of loop tracking of signal synchronization are presented. The analysis is performed by processing the signals from the same satellite and under the same conditions of the initial signal synchronization. The multiple signal processing showed the advantages and disadvantages of the particular methods and the most acceptable solution proved to be the implementation of the DLL tracking loop phase synchronization and the code tracking loop PLL carrier frequency synchronization. The influence of the parameters of the loop itself is shown as well. After the extraction of navigation bits, all bit extracts do not come with an equal phase. This may lead to a wrong decision in rejecting the Decider and bits. Therefore, the paper proposes an additional synchronization of the extracted bits selected by the navigation messages NDA (Non-Data-Aided) algorithm in order to perform their correct detection and to position the receiver much faster. Comparison of methods of signal synchronization Based on the analysis of the methods, the simulation results are compared. The results showed that the TDL loop is not resistant to dynamic disturbances of signals, since the synchronization tracking breaks up. In addition, this loop shows susceptibility to the noise from free space. These are sufficient reasons to propose the implementation of the DLL signal tracking loop as an acceptable solution. In addition to the proposal of the tracking loop, tracking loop coefficient values are determined. Conclusion The performed analysis showed that the TDL loop is not resistant to noise and dynamic disorders of the input signal. Therefore, an appropriate solution for the implementation is the DLL loop with six correlates. The DLL tracking loop coefficients are determined as a compromise solution and they are B = 2Hz and γ = 0.7. Also, the coefficients of the PLL tracking loop of frequency synchronization are B = 20Hz and γ = 0.7. The application of the NDA algorithm results in an additional synchronization of the navigation bit message, thus making the receiver operate faster and more precisely.

120-141

Authors: Majkić Zoran Đ., Vukčević Novak S.

The paper presents the basic requirements for transport vehicles. A special request regarding the adaptation of transport vehicles for the transport of various types of cargo was taken into consideration. Superstructures and the situation arising after mounting superstructures on wheeled transport vehicles were analyzed and the following was described: console coupling, stirrups, simplex elastic coupling, two-way elastic and rigid connection elements. Vehicle torsional elasticity is provided by a proper choice of the type of connection between the superstructure and the vehicle chassis. Applying the instructions of vehicle manufacturers for using appropriate connections between the truck superstructure and the vehicle chassis provides positive torsional elasticity of the vehicle. The paper gives the general recommendations of the Volvo, Mercedes and Renault transport vehicle producers for the use of particular connection types of locations as well as structural requirements for the mounting of concrete mixers, tippers and truck tanks on their vehicles. Introduction Achieving a high level of transport effectiveness depends on a number of factors. One of the most important ones is the possibility to increase the payload share in the gross vehicle weight. This share depends on the net vehicle weight, a method of coupling the truck superstructure with the chassis frame as well as on the truck superstructure construction. Realization of this requirement is of significant importance, particularly for large business systems since it results in the reduction of number of necessary vehicles, more economic fleet maintenance and the fleet capacity increase. It is also relatively easy to adapt the vehicle for the transportation of other loads, depending on user's current needs. The adaptation is correctly performed if manufacturer's recommendations are followed during the mounting of the superstructure on the chassis. This paper gives the analysis of the types of coupling used for particular truck superstructures. Types of truck superstructure A truck superstructure is generally a torsionally stiffer structure of the vehicle chassis and by its mounting on the vehicle main frame the torsion stiffness of the whole vehicle increases. In order to retain the vehicle torsional elasticity because of its positive reaction to strain, it is necessary to apply a particular type of coupling for a particular type of truck superstructure. Regarding the torsional stiffness, truck superstructures can be divided into three groups: 1. Torsionally elastic 2. Torsionally semielastic 3. Torsionally rigid Connection of the chassis and the truck superstructure In order to retain the vehicle torsional elasticity because of its positive reaction to strain, it is necessary to apply a particular type of coupling for a particular type of truck superstructure: Panel connection Panel connection allows longitudinal motion and prevents lateral or vertical motion of the chassis runner in relation to the main vehicle frame. Stirrup (U bolt) connection Stirrup connections enable longitudinal motion of the chassis runner in relation to the main frame but they cannot accept lateral forces, so additional leading plates are mounted for that purpose. Simplex elastic connection Simplex elastic connections enable vertical motions of the automotive frames due to the effect of longitudinal torsion moments as well as longitudinal motion of the chassis runner due to the effect of longitudinal forces and frame flexion moments. Two - way elastic connection This kind of connections is used to connect the truck tank with the vehicle automotive frame. The connection supports lateral and longitudinal forces and enables vertical motion of the automotive frame in relation to the truck tank, during the torsion and lifting of the vehicle. Stiff connection (connection plates, sheets) This type of connections enables rigid connection of the automotive frame and the chassis runner thus making them behave as a whole. Connection plates transfer longitudinal, lateral and vertical forces. They are mounted from the front of the anterior support of the rear suspension to the end of the automotive (chassis runner) frame. The upper part of the plate is welded for the chassis runner, while the lower part of the plate is bolted for the automotive frame. Guidelines for the application of particular truck superstructures A truck superstructure must not prevent the chassis movement; therefore, it is important to choose a proper type of connection between the chassis and the truck superstructure. Chassis twisting is most expressed in the area behind the driver's cabin and it should decline towards the rear of the vehicle. If a rigid superstructure is mounted on the basic frame and the coupling is also rigid, the twisting of the main frame is not gradual but sudden and restricted to a limited area where high levels of torsion stress occur. The principal rule regarding the rigidity of superstructures is: the stiffer superstructure is, the more elastic connection must be. Manufacturer's recommendations for particular types of truck superstructures Manufacturer's recommendations for concrete mixer superstructures The truck superstructure of a concrete mixer is an example of torsionally flexible mounting. Figs. 7, 8, and 9 show types and cites of connections as well as some structural requirements of Volvo, Mercedes and Renault transport vehicles [2, 3, 4, 5]. In a 6x2 Volvo (Fig. 7), the first three couplings are cantilevered and five other connections are achieved with midfielder plates. The mixer is mounted on 6x2 vehicles with suspension or on 4x2 or 6x2 vehicles with air damping. All twin - shaft trucks could be loaded with 13t on the rear axle. Mercedes does not give much information related to the concrete mixer superstructure. To ensure stability and reduce strain of truck frames, the chassis runner is stiffened in the rear. Fig. 6 shows that the Mercedes chassis runner bends outwards, because of the possibility of embedding a larger drum or because of lowering the existing one in order to lower the focus down and thus increase the stability of the entire vehicle. Recommendations of the body tipper manufacturer A body tipper is an example of a torsionally flexible superstructure. Fig. 10 shows some types of sites and links, as well as some structural requirements of Volvo and Mercedes tippers [2, 3, 4]. Linking the main frame with the mounting one is performed using the console connection in the front part while near the axles connecting plates are used. To ensure the stability of the vehicle when unloading and to reduce stress, the frames are stiffened in the rear (Fig. 8). Recommendations of the manufacturer for mounting tanks Tank compartments are usually of circular or elliptical cross section, and as such they have large shaft, polar or torsion inertional moments. If the theories of material resistance and construction resistance are applied, it can be easily shown that the bending and torsion rigidity directly depend on the size of the moment inertia; x x c ~ I ; ϕ ϕ c ~ I , from which it can be concluded that the tank is a very rigid structure regarding bending and twisting. To connect the superstructure to the vehicle base, two-way elastic connections are used. Fig. 9 shows a twin-shaft Volvo tank with the number and types of connections used in connecting the main frame with the tank compartment. Three-axle tanks and four-axle tanks with the type and number of links of the main vehicle frame with the tank compartment are also shown. Similarly to the case of the tipper MB [3], there is no much information about linking the basic frame with the tank. Fig. 9 shows only a simplified method of coupling, without defining the number of connections and a more detailed description of connections. However, an important difference observed in relation to the solution of the Volvo manufacturer is that a chassis runner is used. Conclusion The analysis of the guidelines of leading manufacturers for upgrades, transport vehicle chassis and their connections leads to the following conclusions: The connection with the basic superstructure frame is an extremely complex issue. It is necessary to consider many factors (type of connection, the connection location, size and shape of the assembly - extra frames, the types of upgrades, etc.) since its characteristics directly affect both the reliability and the payload mass. As shown in the guidelines for the implementation of certain kinds of connection upgrades, a type of interactions on the basic frame depends on the torsional stiffness of the superstructure. Truck superstructures must not move to limit the chassis and is thus important to properly choose the types of connections and chassis upgrades. The connection of the upgrade to the basic frame is taken as already given by the manufacturer, having in mind extensive research of the manufacturer in this field. Regardless the simplifications in the application of general recommendations, the comparative analysis shows that there is a proper connection of the base and mounting frame which eliminates the possibility of breakdown.

158-174

Authors: Borisov Mirko A., Banković Radoje D.

Application of computer technology in the Earth science has led to the creation and development of new scientific disciplines, particularly digital cartography and GIS. This paper describes the application of GIS from several points of view such as: multi-scale, multi-thematic, multi-viewing, accommodation to standard software platforms and multi-user data accesses. Introduction The premise of a successful usage of topographic data nowadays implies their disposal in a digital form and organisation in a modern way, suitable for further computer processing. It is a unanimous opinion that it can be successfully completed only through creating data basis of space developing GIS. The theme of the written work is the development and application of GIS, and management of topographic data in accordance with international standards and users' needs. Moving to digital technology of creating and using topographic data should not be literal translation of the analogue map into a digital picture or just the automation of the map making using digital technology. The new method implies the formation of the central topographic data base which would generate displays of arbitrary scales, desired volumes of content, changeable sheet dimensions, various thematic displays, altogether in accordance with users' demands and needs. Digital cartography and GIS The development and application of computers in the area of earth sciences caused the creation of new definitions and disciplines among which are noticeable computer supported cartography and GIS. The computer-supported cartography was in its later phase called digital cartography and it can be used in two ways: like modern technology of date processing about space and like a new discipline. The main principle on which digital cartography as a discipline is based represents the processing and visualization of data about space but with computer supported technology. Application of GIS from various aspects Topographic maps have existed for many years in more or less similar or the same traditional form. By creating the basic data base about space through the application of GIS technology, a wide range of possibilities for dynamic selection of content appears. This content will further be shown on the screen or as a drawing on a piece of paper. The aspects of multidisciplinarity promote topographic data base as a significant part of general spatial data infrastructure. Application from the multiscale aspect There are different information levels which differ among themselves in quantity and content of data necessary for various levels of observation management and decision making. One of the principal tasks which emerges is a choice of the basic scale and resolution of the display for which the data are gathered. In cartography, that is a scale of 1:25,000, based on which the topographic map (TM) is created. Mutual complement of GIS and WWW will completely change the classic delivery of spatial data. Various topographic and thematic maps will be created and obtained from the unique data base. Application from the multithematic aspect The main objective of the formation of spatial data infrastructure is the creation of the standard GIS platform but also the possibility of multi purpose application of GIS for environment (farming, forestry, waterpower engineering) land development (commercial and business), itinerary analysis, tracing of retail and wholesale routes distributional nets (shops and warehouse locations) media and marketing planning (locations, sales territory, sales prospects, market analysis according to users), finances - insurance (from the users aspect, investors and areas of low/high risk), healthcare (general healthcare, appearance of epidemic and its spreading) and non-productive activities (tourism, archaeology, environment protection). Application from the aspect of multidisplay Once formed, the spatial data base, or GIS, should offer to the user a lot of graphic, descriptive and other important information which is, in fact, a digital or traditional display in a form of a determined output. One of the ways of using GIS implies cartographic publishing (getting the reproductive originals and printing geographic map sheets) in a traditional form. Application from the aspect of adjustment to standard software platforms In the groundbreaking period of civilization with radical changes in a scientific - technological sphere, it was necessary to select a new, most suitable software platform with attaching hardware components. After thorough analyses (analyses of foreign and national literature and the usage of demo versions of various GIS software), the American company ESRI software platform was selected. Application from the aspect of multiusers data access Internet and Intranet are deeply rooted technologies and have been increasingly used as technologies to accomplish the growing number of distributed informational systems. Therefore, the above-mentioned technologies are needed for distributed work with spatial data. Maintenance of GIS data The maintenance of the topographic data denotes a process of updating old-fashioned content and entering new geospatial data as well as the elimination and the correction of details which are not in accordance with the real state on the field. In connection with the volume and the method of work, difference should be made between the spatial data maintenance aspects for the basic scale, which refer to the entire content and specific elements of the content. Regarding periods in which the present space data maintenance is done, there are continuous and periodical ones. Conclusion When establishing the unique GIS, we ought to apply a principle according to which all the data once gathered in one State institution can be used variedly as well as in many other institutions (military, administrative, economic, scientific, cultural, etc.). This principle does not apply only to the rationalization but also to uniqueness and quality of the research of common geospace. In the present state of the development, it is hard to predict the trends of cartographic and generally speaking GIS processes, but the most important is that topographic data have digital form the meaning of which is universal, regardless of the current development of technique and technology.