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N.V. ZOSIMOVYCH, R.K. SINGLA
Sharda University, Greater Noida,UP, India
INFLUENCE OF FACTORS DETERMINE THE VALUE OF TOLERANCE ON THE OUTBOARD SIDE UAV
As a result of perfection of forms modern and perspective unmanned aerial vehicles (UAV) probes of typical geometrical parameters of a surface have been made and the technique of appointment of admissions on external surfaces is offered. In this paper analyzed the selection criteria tolerances on contours of UAVs, proposed a model choice structural and technological solution in implementing tolerances and explored factors that determine the value of tolerance for the external contours of UAV.
Key words: Unmanned aerial vehicle (UAV), surface, aerodynamic quality, sinuosity, technological roughness’s, ledge, indent, constructive and technological actions, fuselage, fuel consumption, specifications, flying vehicle (FV), mathematical model (MM).
Increase of efficiency UAV is caused, on the one side, by a problem of fuel resources, and with another side a tendency of change of structure of expenses for life cycle aside reduction of a share of initial FV cost. Aircraft engineering practice marks following basic ways of increase of FV efficiency :
The importance and urgency of improving the aerodynamic efficiency by improving the forms of modern and advanced FV, including by improving the quality of exterior surfaces, confirmed by the entire history of aviation.
Detailed consideration the dependence of resistance from quality of performance of external surfaces by manufacture shows that additional resistance can reach 2…10% at zero upward force . The greatest share is brought by the deviations increasing a lateral section, details for example acting in a stream (approximately 5 %). Nearby 1.2 … 1.5 % are necessary on rivets and bolts connections; 0.5 % on joints of sheets; leaky position of shutters and hatches gives 1.0…1.5 %; rough coloring (over 20 microns) – up to
At speed from above М=1.5 the size of all components increases approximately twice and resistance from a sinuosity - more than in 5 times. For the reasons specified above the resistance increase through technological roughness’s for subsonic FV makes approximately 5…6 %, and for supersonic (М=2-3) - 10…16% .
Perfection of quality of external surfaces probably at the expense of constructive and technological actions that in turn can lead to additional expenses [3-7]. Therefore an important question at definition of quality of external surfaces is the choice of criterion for quantitative estimations of similar actions [8-12]. As such criterion for a quantitative estimation of losses from additional resistance it is possible to accept the expense or fuel cost [13-18]. The expediency of an estimation of such kind is obvious, as fuel consumption is unique precisely measured parameter at the given design stage UAV, directly reflecting infringement of aerodynamics of a surface, both in manufacture, and in operation [19-26].
In development of designs FV and, accordingly, technologies of their manufacture always crucial importance had constant increase in speeds of flight . Growth of speeds of flight not only causes of application of new, more and more heat-resistant materials (Fig. 1), but also is accompanied still nearby important for development of the production technology of tendencies [27-28].
It first of all concerns change of forms of units FV [5, 29]. Simple rectilinear forms of surfaces of units of a glider in process of growth of speeds pass in complex surfaces of double curvature. To the production technology the total disappearance of cylindrical formations of fuselages is essential almost at speeds from above М=0.85 and linear surfaces of wings and plumage, since the speeds from above М=2.0. On change by their surfaces characterized by complex enough laws of formation of the form come .
The proceeding increase in speeds (at least to М=3.5…4.5) causes toughening of requirements to accuracy of the external contours, interfaced to serious problems in the field of technology and designing of units .
Deviation of elements of a surface from a theoretical contour, a raising of heads of bolts, rivets, screws in a stream, steps, a roughness etc. on everyone concrete FV or group of planes are appointed in specifications developers.
Maximum deviations on elements of aerodynamic surfaces are defined proceeding from admissible sizes of additional resistance and flow conditions on various modes. As a rule, specifications on the form and quality of a surface of the airplane provide division of units into zones according to their importance in formation of a streamline stream. Typical requirements to parameters of quality of surfaces UAV are in a range of мм .
To the first zone carry surfaces of units to which increased requirements on quality of a flow are shown. Higher requirements are accepted for a wing мм, less high ones for a fuselage at great numbers and thickness of an interface. Conditions of preservation of a laminar flow are put in a basis of requirements at small numbers as there is an opinion that roughness’s start to influence, if their height exceeds a thickness of a laminar local layer .
Additional resistance from a surface sinuosity is in sedate dependence on size of a deviation of a surface and its position concerning a forward edge . This circumstance is considered in specifications at definition of zones of surfaces of units.
Taking into account similar reasons restrictions of size of local roughness’s of type of ledges, cracks and fixture heads are generated мм .
By working out of constructive and technological decisions it is necessary to define the requirements shown to quality of object of manufacture and technological processes, in particular to appoint maximum deviations of aerodynamic surfaces.
To typical deviations of geometrical parameters of elements carry out next :
1) smooth deviations from the theoretical contour, measured by comparison of an actual surface from the ideal. In practice as the ideal accept a surface set in one of systems:
а) the measuring machine on the basis of mathematical model of a surface;
b) reference surface in the form of its breadboard model;
c) flat carriers of the form and the sizes at use plaza and sample methods, means of spatial coordination, control templates or assembly equipment;
2) eminence of one part of a surface over another against a stream (so-called ‘step’) or on a stream (‘ledge’). Geometrical parameters appreciate by results of excess measurements;
3) smoothness of transition of one part of a surface in another (so-called ‘sinuosity’), characterized in the length of a wave and amplitude. The sinuosity is classified on character of display  - cylindrical or spatial. This kind of an error of an external surface is defined by discrepancy of manufacturing and design assemblage in which result there are the internal pressure covering all sections or its parts. Local deformations occur owing to formation of connections (rivets, welded seams). Sinuosity measure or concerning a base line, a tangent to the maximum roughness (ruler), or by results of comparison of an actual surface with ideal . At a smooth deviation of contours on sinuosity size on base makes where is scope of an error. At the set size of the admission it is necessary to accept
4) local excess of elements of a surface in the form of acting (sinking down) heads of fixture. These errors are registered by means of universal and special measuring instruments. The basic geometrical parameters of deviations are the height and diameter ;
5) cracks through or without an exit between elements of a surface of the unit. These errors also are measured by universal tools or special templates and characterized by the relation of width to depth т.е. or the admission for width of a through crack ;
6) punching of an external surface of the unit owing to defects of a surface. These errors are limited by an equivalent aperture on area unit  (Fig. 2).
Admissions on a relative positioning of global surfaces of separate units and units among themselves in this case are not considered.
For the purpose of definition of a generality of the constructive and technological decisions accepted in specifications, revealing of the reasons defining size of the admission have been analyzed specifications for more 30 FV various types and appointment.
Fig. 1. Growing of speeds on flight of FV : 1) for aluminum designs; 2) for titanium designs; 3) for designs from special steels; 4) for designs from special alloys; 5) for subsonic UAV
Fig. 2. The typical geometrical parameters of a surface limited to admissions : 1) cylindrical sinuosity; 2) spatial sinuosity; 3) crack (a backlash); 4) ledge against a stream; 5) ledge on a stream; 6) punching
Fig. 3. Dependence of change of the admission on a deviation from a contour of the unit from speed
Fig. 4. Dependence of change of the admission on parameters of a sinuosity of a surface from speed
Fig. 5. Dependence of change of the admission on parameters of a ledge of a surface from speed
Fig. 6. Dependence of change of the admission on parameters of a crack of a surface from speed
Fig. 7. Dependence of change of the admission on immersing parameters in a surface from speed
Fig. 8. Dependence of change of the admission on parameters of a ledge from a surface in from speed
On Fig. 3-8 the schedules constructed by results of statistical processing set in specifications of admissions are presented .
Qualitative performance indicators, as noted in , is a ratio of the target impact to cost for the whole lifecycle is As for improvement of quality surface of targeted output are generally does not change that improving the efficiency is possible due to changing the value of the life cycle. Hence as a selection criterion tolerance assume the condition  as:
where manufacturing cost; maintenance costs for the entire lifecycle, equal to staff salaries; the cost of ground handling and support of UAV flights; the cost of UAV repairing; fuel costs. Surface quality a direct impact on UAV fuel costs, because deviations from ideal surface in majority cases helps to increase the resistance at zero lift, i.e. Whereas where range (field) error.
The same time cost of production depends on the achieved level precision that determined by the methods applied and industrial facilities with the characteristic tendency of rising costs with increase accuracy . Noted suggesting that dependence of cost the function can be described according to (1) the optimal value of tolerance is defined by equation :
and depends upon the intensity rising costs when the Given equation is correct for the case when the UAV target output unchanged.
Depending upon variant of the problem the criterion may be modified and added:
The criterion for last two options is (1).
Solutions above criteria for the tolerances values should be checked for the conditions of current implementation or newly adopted technological processes. Practically it means selecting from an array of possible technological solutions to the most suitable which must simultaneously provide minimum production costs, i.e. or allowance and non-zero value the tolerance field.
Thus, selection process for constructive and technological solutions for improving the external contours of UAV includes a number of consistently carried decisions (levels) with special constraints (Fig. 9).
The factors determining value for admission to contours of the Unmanned Aerial Vehicles
Fig. 9. The algorithm of choosing structural and technological solutions in implementation of tolerances (TR – technical requirements; TS –technological solution; ES –engineering solution)
Fig. 10. The structure of the mathematical model the choice of tolerances to external contours
The magnitude external outline tolerance influences range of factors which determine the value derived from operating costs which depend on the quality the external surface defined as the cost an additional fuel :
where hours fuel consumption; increment value of resistance due of surface defects.
In order reduce the amount of calculations for comparing various design and technological solutions expedient to introduce the concept costs per unit of surface area ($/m2) :
Taking into account that the additional resistance for irregularities such wave, step, slit, etc. may be described by the equation:
where drag coefficient of isolated irregularities; functions reflecting the influence of speed and altitude; maximum height of the surface that is equal to scale of error; the coordinate characteristic parameter roughness (in m, for example, maximum amplitude of wave, a step, etc.); относительная площадь, занимаемая исследуемой неровностью relative area occupied by roughness of investigated; показатели степени the exponents.
According to the equations (3) and (4):
Thus the additional cycle costs are defined by basic parameters of UAV and conditions of its exploitation. Expenses for manufacture in general depend on method adopted pre-production, level of the cost of one hour defined accepted methods and means. In general, this set of determines the technological solutions which used to implement the some set design solutions.
Establishment of functional relation between cost of production and size the construction errors are self-task. In the present paper considers only the final results to principal design solutions. Proceeding from the results of statistical analysis manufacturing costs may be recommended dependence types of:
These dependences (1), (5) and (6) allow establishing a quantitative correlation between forms of factors in described, i.e. to present the process choice of tolerances as mathematical model (MM) (Fig. 10).
In general case this MM must be supplemented a description of the impact of external factors on target function provided to the form of fuel prices, unit cost of work, etc. . Optimal value of tolerance according to the accepted criteria determined by the equation:
using which possible to find an estimate each factor relative to the base value, i.e.
Given equation (8) allows you to recalculate the tolerance when changing flight conditions, engineering and technology implementations (ETI) and the external environment. For example, changes in service life defined by the ratio . Then when be taken more close tolerance, as Influence of flying speed estimated by the ratio :
In case of monotonic changes the incoming parameters require to tightening tolerance with growth. For the solution problems of choosing tolerance (especially in case of iterate through possible options), for example, over 30 and the different flight conditions), you can use the algorithm and calculation program developed on the basis suggested MM.
The analysis of appointment of admissions on external surfaces of units FV, practice of their appointment and realization in manufacture allow drawing following conclusions:
Поступила в редакцию __.__.2012
М.В. Зосімович, Р.К. Сiнгла
Дослыдження форм сучасних та перспективних безпiлотних лiтальних апаратів (БЛА) дозволило дiстати оцінку типових геометричних параметрiв поверхнi та призначення допускiв на зовнiшнi поверхнi апаратiв. У статтi проаналызовано критерыъ вибору допускыв на зовнышны контури БЛА, запропонована модель обрання конструктивних i технологiчних рiшень пiд час призначення допуску та вивчено фактори що визначають значення величини допускiв на зовнiшнi контури БЛА.
^ природоресурсний та екологiчний моніторинг, безпілотний літальний апарат (БЛА), авіаційний комплекс (АК), інформаційна панель (ІП), льотчик-оператор, монітор, стимул, математична модель (ММ).
^ – канд. техн. наук, професор кафедри iнженерноï механiки Унiверситета Шарда, Грейта Нойда, Iндiя, e-mail: firstname.lastname@example.org .
Rohit Kumar Singla – магiстр iнженерноï механiки i виробничих технологiй, асистент-професор кафедри iнженерноï механiки Унiверситета Шарда, Грейта Нойда, Iндiя.
Н.В. Зосимович, Р.К. Сингла
Исследование форм современных и перспективных беспилотных летательных аппаратов (БЛА) позволило получить оценку типичных геометрических параметров поверхности и назначения допусков на внешние поверхности аппаратов. В статье проанализированы критерии выбора допусков на внешние контуры БЛА, предложена модель выбора конструктивных и технологических решений при назначении допуска и изучены факторы, которые определяют значения величины допусков на внешние контуры БЛА
^ природоресурсный и экологический мониторинг, беспилотный летательный аппарат (БЛА), авиационный комплекс (АК), информационная панель (ИП), летчик-оператор, монитор, стимул, математическая модель (ММ).
Зосимович Николай Владимирович – канд. техн. наук, профессор кафедры инженерной механики Университета Шарда, Грейта Нойда, Индия, e-mail: email@example.com .
Rohit Kumar Singla – магистр инженерной механики и производственных технологий, ассистент-профессор кафедры инженерной механики Университета Шарда, Грейта Нойда, Индия
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