№ 112(8), October, 2015
Public date: 30.10.2015
Archive of journal: Articles count 151, 381 kb
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Description
The article considers the problems of determining the settings area of the control device, which ensure stable operation of the closed system. It shows the solution to the problem using the enhanced amplitude-phase characteristics. The proposed method of finding the domain of stability of parameters of the control device is more simple than classical methods and allows, in general, to find conditions for the stability, not to test the system for stability under given parameters
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Description
The article deals with the study of the influence of the elastic damping mechanism (EDM) on the operability index for arable MTU on the basis of the 1,4 class tractor. The elastic damping mechanism was designed in order to smooth the aggregate starting, to reduce the dynamic load in transmission, to protect the engine from the external load vibration. The experimental results that were obtained while full-scale field studies of serial and test (containing EDM in transmission) machines are given in the article. Various oscillograms are analyzed: torque on the axis of tractor's driving wheel, tractive effort, the speed of the driving wheel, angular velocity of engine shaft and haulage. The mass-spectrum analysis was carried out to study the tractor characteristics in time more thoroughly. Such analysis allows to evaluate qualitatively the EDM influence. The normalized autocorrelation function and spectrum density of variation in time are studied in details for the following MTU characteristics: the wheel torque, haulage and tractive effort. These characteristics were compared with analogous characteristics for serial MTU model. The obtained results confirm that the EDM use in the tractor transmission has a positive effect on the functional MTU indexes. Obtained data can be used in mathematical modeling of MTU functioning
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CONTROLLING SMALL MOVEMENTS OF ULTRA PRECISE DC ELECTRIC DRIVE WITH ELASTIC SHAFTING
DescriptionControl of the movement and positioning are the most intensive tasks of automatic control and regulation. However, these problems must be solved in the automation objects such as assembly and production lines, manufacturing machines, conveyors, hoisting machines, packaging machines, filling lines for liquids, metal-working machines. One problem lies in the fact that all the real drives are connected to the actuators with not perfectly tough shafting, but has some elasticity. This leads to the difficulty of motion of the executive body of the drive automatic control systems which consists of signal source generating signal due optimum speed diagrams for small movements of electric drive’s actuating device and automatic regulation system, which allows to work out optimum speed diagrams for small movements of electric drive’s actuating device with ultra-precision. In this article were developed optimum speed diagram for small movements of ultra-precise electric drive with elastic shafting. Were have identified all parameters of diagrams and its range of existence and also developed a device for generating the optimum speed diagram for small movements of ultra-precise electric drive with elastic shafting. The implementation of the proposed hardware software complex will significantly improve the accuracy of motion actuators of various ultra- precise DC drives
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MECHANICAL GRINDING OF SOLID POWDER MATERIALS
DescriptionThe article is dedicated to the determination of conditions for solid bodies’ fragmentation, providing minimal size of particles by means of their mechanical dispersion through the example of powders of titanium carbide (TiC), cubic boron nitride – borazon (CBN) and boron carbide (B4C). The theoretical and practical aspects of the process of mechanical fragmentation of particles of solid powder materials in ball mill for their further utilization in furnace charge for high-speed gas-flame sputtering of wear-resistant composite materials are examined in the article. Methods of preliminary calculation of minimum allowable size of solid particles of powder materials during mechanical fragmentation, based upon Griffiths’ mechanical theory of rapture using experimental data for hardness of material and its yield are proposed and theoretically substantiated. There we have the results of experiments on mechanical fragmentation of titanium carbide in attritor, boron carbide and cubic boron nitride in centrifugal planetary mill, confirming correctness of theoretical propositions and calculations are set out. Recommendations on mechanical fragmentation of solid powder materials in ball mills are formulated as well
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Description
The development of agricultural production inevitably entails an increasing volume of traffic and a turnover of goods. Therefore, the issues of increasing transport efficiency, reducing the price of transportations and improving productivity acquire great importance. In most cases, supersize dump trucks used for the transport of agricultural production have much more than 6 tons axle load. Thus, these cars need to have roads with improved surface to each field, which undoubtedly is a significant drawback. Because of the extra movements of harvester dump trucks on the turning strip at the end of the field, it increases expenses of damage and loss of crops and the arrival of heavy machinery in the field leading to soil compaction, that in the end affects the future crop. Transportation of agricultural commodities is most effective when the car arrives directly to the harvester machinery. Such vehicles must have sufficient abilities and capacity of the body comparable with the volume of a combine hopper and has no significant impact on soil sealing. With this method, harvesters do not make extra movements and are not idle. Basic requirements for vehicles used in the harvesting potatoes, are in a more productive use due to increasing the capacity and reducing downtime when loading or unloading and minimizing the level of damage to other tubers. For the transportation of agricultural products there is a different transport technology, which either do not fully meets the requirements of transportation of highly fragile product, or has a significant cost. Therefore, we require a specially equipped vehicle bodies, with a competitive ability in the range acceptable to the Russian Federation. As one of the innovative developments, this article proposes a tipper body of the vehicle for transportation of highly fragile agricultural products. The proposed design solution for the tipper ensures a uniform unloading of transported products from the vehicle body and prevents arching issues
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Description
The article discusses the relevance of the development of the methodological apparatus of analysis and evaluation of the functioning of complex organizational and technical systems, as well as methods of forming a set of dynamic optimal control models
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Description
At calculations, we have used the next assumptions: 1. Not excluded systematic errors distributed with equal probability; 2. Random errors are normally distributed; 3. Total error is the composition of not excluded systematic and random errors. In calculating of measurement error of pressure, we proceeded from working formula. The confidence interval of each variable less than instrumental error, therefore, to characterize the total error of the measured value P, we use the instrumental errors of all variables. In estimating of temperature measurement error was consider the systematic and random error. To estimate random error we used measurement data of the specific volume of water on six isotherms. Obtained values were compared with published data. As an approximate estimate of the random error of our experimental data, we can take it as a total for all the isotherms of the specific volume in comparison with the published data. For studied fractions confidence limit of total error of measurement results located in the range of 0,03 ч 0,1%. At temperatures close to the critical increasing influence of errors of reference and the error associated with the introduction of corrections on the thermal expansion of the piezometer. In the two-phase area confidence limit of total error increases and located between 0,08 ч 0,15%. This is due to the sharp increase in this area of reference error of pressure and error in determining to the weight of the substance in the piezometer
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Description
The industrial safety on cereal production is currently important due to the severity of the consequences of accidents occurring to them. It should be noted that, despite the considerable efforts of recent years, awareness-raising and supervisory plan towards preventing their occurrence, the lack of attention of organizations operating hazardous production facilities to comply with the relevant standards and requirements allows us to characterize the recent situation in this area quite difficult, as evidenced by statistics. In this article it is clearly illustrated the qualitative and quantitative expression of such an approach in practice. The conceptual framework is disclosed in the light of efforts to carry out industrial safety examination in the conformity assessment of hazardous industrial facilities according to industrial safety requirements in the Russian Federation. The basic methods and technical means used for the prevention of accidents at hazardous production facilities of storage and processing of plant raw materials provide an overview of domestic and foreign producers. The item-description of the system of protection of buildings and facilities of hazardous production facilities is given taking into account the industry specifics. There are specified the key factors meeting modern technical requirements, cost-based position of enterprises, ensuring conditions for safe operation of the storage and processing of plant raw materials
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PROSPECTS OF SMALL HYDROPOWER PLANTS IN THE PIEDMONT AND MOUNTAIN STREAMS
DescriptionThe article reveals the advantages of low energy in comparison with other renewable energy sources. It is shown that broad prospects are visible for small (100 - 1000 kW) and micro hydropower plants (up to 100 kW) when used in the foothill and mountain areas. At the same time, the construction of hydropower plants of sleeve-type has improved the operational and technical characteristics, among other types of small-scale power plants. The article presents main analytical expressions for calculating hydroelectric power generator and it has built graphic dependences for the power generator of pressure and water flow. To improve the performance of small hydroelectric power plants we have proposed using unregulated water turbine and non-contact induction generator in their construction, thus, we could stabilize voltage and frequency directly by the frequency converter. Depending on the requirements of consumers to power supply reliability and electricity quality, we have offered several options for structural and circuit solutions of autonomous systems of electrosupply, made using small hydroelectric power plants. Thus, we can greatly enhance the efficiency of such systems if they are used with other types of renewable sources, such as windfarms or solar power plants
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THE CHOICE OF THE GENERATOR AND ELECTRICITY STABILIZATION FOR SMALL HYDROPOWER PLANTS
DescriptionThe article analyzes the main characteristics of the electricity generators to use them as a part of small hydroelectric power plants. It is shown, that contactless asynchronous generators in comparison with synchronous generators and DC generators have improved their operational and technical characteristics, and above all, their reliability and performance efficiency. We have shown graphic dependences of the cost and the weight of power generators. It is proposed using direct frequency converter as a stabilizer of parameters of asynchronous generator of electricity, used as a source of electricity for small hydropower plants. The article explains the features of the work and the choice of parameters for generators, working together with the direct frequency converters. The authors have revealed some aspects of the work of direct frequency converters with natural commutation and with adjustable phase angle, including their advantages and disadvantages. The article also presents block diagrams for small hydroelectric power plants, made with the help of asynchronous generators and direct frequency converters