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14TECHNICAL SCIENCES
STRUCTURAL DRAFTING OF CONVERTIPLANE-TYPE UNMANNED AERIAL VEHICLE
Nabiyev R.
Abdullayev A.
Qarayev Q.
Azerbaijan National Aviation Academy, Baku. AZ1045, Mardakan ave. 30
https://doi.org/10.5281/zenodo.7198424
Abstract
The article gives a structural draft of a convertiplane-type unmanned aerial vehicle and the purpose of its components and depending on the location the effect of the selected elements on its aerodynamic properties is based on theoretical and practical knowledge. Also, the main parameters of the convertiplane have been optimized in the context of observation of strategic objects and the probability of its detection by visual, acoustic and radar detection means has been determined.
Keywords: unmanned aerial vehicles, convertiplane, flight controllers, flying wing, aerodynamic features, accumulator batteries.
It is well known that in a globalizing world it is necessary to have quality information to assess critical risks for effective management, rational planning, optimal use of resources and a high level of security.
Timely detection of threats to the security of oil and gas export pipelines, ensuring the security of air, water and land borders throughout the country by taking preventive and adequate measures in this direction is of national importance. It is possible to carry out research, inventory, planning, environmental monitoring or operational control of the infrastructure of onshore and offshore oil and gas production facilities using UAVs [1]. One of the main applications of UAVs is their use in mapping and aerial photography. By performing mapping and aerial photography in the most dangerous places, it is possible to prepare topographic maps, as well as to observe strategic objects using UAV, which minimizes the risks to human life and health. The efficiency of using the latest generation UAVs is irreplaceable, which are very hard to be detected by visual, acoustic and radar detection in the observation and protection of strategic objects. The UAV's autonomous flight function on a given route significantly reduces the cost and time spent on piloting aircraft and real-time on-board imaging, allows you to monitor the terrain in real time and make decisions on the spot.
The purpose of the work: Consists of determining the optimal structural draft of a convertiplane-type unmanned aerial vehicle (UAV) designed for mapping, monitoring of oil and gas
industry facilities, observation of strategic facilities and aerial reconnaissance and combining the flight and technical characteristics of both the helicopter and the aircraft.
Structure and working principle of components of convertiplane-type uAv. Description and main parameters of the components that make up the internal parts of the convertiplane [2, 3], designed by us and having the necessary technical characteristics, are described in Table 1.
The structure of a convertiplane has been designed based on the "Skywalker X8 Flying Wing 2120mm" stationary wing glider using the propulsion engine directly installed on the rear of the fuselage, electronic equipment attached on the body and lifting motors fixed to glider through two carrier arms made of carbon tubes installed parallel to each other on the top of the wings. Carbon tubes with a diameter of 20 mm, wall thickness of 1 mm and a length of 1 m have been used as carrier arms. The front and bottom view of a convertiplane is described in Figure 1a and 1b.
When installing lifting engines, the structural, aerodynamic and following requirements for the purpose of the UAV must be observed.
1) The distance between the centers of the motors on the axis of rotation should be as small as possible.
2) During propellers rotation the area of the circles they draw must be outside the area occupied by the glider.
3) The location of the engines must allow the UAV to be used for its intended purpose.
Tabic 1.
Onboard components included in the structure of the convertiplane.
№ Name and (or) brand of the product Description Operating principles or features
1. Here 2 GHSS # GPS module
2. PIXHAWK. 2.1-Cube The flight controller consists of a microprocessor, 3-axis gyroscope, magnetometer and 2 barometers. Frequency: - 168 MHs; RAM: - 256 kB;
3. Carbon tubes Composite carbon tubes
4. Batteries s 1 LiPo battery 6S 5000 mAh
5. PI5x5 Prop-2PCS/PAlR i ■ m m - Maximum rotation speed - 3500 rot/rnin; - It is lightweight, has a large carrying capacity and a long flight time. - Number of wings - 2;
m1
6. Non-collector electrical motor (lift), T -Motor MT4008 K.V600 - Internal resistance - 132 mil; - Stator diameter - 40 mm and length-8 nun; - Shaft diameter - 4 mm; -Weight - 100 g;
- Current - 40 A - Frequency - 400 Hs - Battery - 2-6S - Weight - 26 g - Dimensions - 55.6x25.2x11.3 mm
7. ESC- clcctronic speed controller T-Motor 40A T-MDTDI?
Master Airscrew 12x6 K-Series Propeller Drag (thrust) propeller
8.
9. Non-collector electrical motor (thrust), U7-V2.0 KV490 Cm Thrust engine
10. ESC - electronic speed controller T-Motor 80A FLAME LV Operates with 400 Hs ESC 4-6S. - Current - 80 A - Dimensions: 30,6x72,2x17,3 mm - Weight - 110 g
11. Foxtcch Map-02 Oil "-/J 1-, - Number of pixels (effective): 24.3 mp - Shooting speed: 30-1/4000 sec. - Image format: jpeg, raw, - Operating voltage - 8,4 V
12. MinimOSD & - Operating voltage - 5 V, - FTDi input
13. Radio telemetry module CUAV SX Radio CUAV SX Radio 5H - 900MHz Wireless Data Transmission Module TX RX - Weight-39 g
14. FPV 5,8 GHz Wircllcss Video Link 48CH Transmitter TS832 LaP - Power - 600 mW; - Weight - 25 g
a)
Fig. 1. View of the front and bottom of the convertiplane
b)
The first requirement is to reduce the moment of forces acting on the carrier arms, and consequently their load, and it's a structural requirement. When fulfilling this requirement, it should be taken into account that the
minimum distance between the centers of rotation of the rear engines serving vertical lift is limited by the length of the propeller shaft.
Fig. 2. Upper view of the convertiplane.
Second, the maximum use of the lifting force of the engines is ensured when fulfilling the aerodynamic requirement. Otherwise, the lift force of the engine will decrease as a result of the downward flow of air in the vertical direction of the propeller in proportion to the extent to which the wing covers the area of the circle covered during rotation.
For the purpose of mapping, as well as electron-optical reconnaissance of strategic objects, the UAV is equipped with a video camera mounted to the bottom of the fuselage front side. During rotation, the blades may enter the field of view of the video camera's lens and adversely affect image quality. Thus, in order to meet the third requirement, as well as to ensure a stable balance of UAV in the air, the engines are mounted to the upper side of wings. In such a design, the center of gravity of the PUA is below the flatness of the lifting motors, which ensures that the steady balance condition is met in any situation.
The on glider installation place of the propulsion engine, which provides horizontal flight, is provided by the manufacturer at the rear of the fuselage. Under the same conditions, the front-mounted traction motor has two known disadvantages compared to the rear-
mounted thrust motor. First, the front part of the glider sharply reduces the speed of the air flow going back from the propeller mounted on the front, resulting in a significant reduction in the speed of the aircraft. Second, the vortex air flow created by the front-mounted propeller tries to rotate the aircraft around the main axis by affecting one of the wings from below and the other from above and in aviation terms, to disturb its horizontal balance on the roll. In order to maintain horizontal balance, it is necessary to create a different lifting force on the wings by changing the position of the small moving parts on the back of the wings - the ailerons. This increases the aircraft's air resistance and power consumption and reduces flight time. The top view of the engine layout on the glider is described in Figure 2.
Propulsion system. The power system of the convertiplane includes five non-collector electric motors and their electronic speed controllers and two servomechanisms. As is well known, a propeller, a non-collector electric motor and its electronic speed controller together form the propeller-motor group (PMG). The vertical take-off and landing is provided by four and the horizontal flight by one PMG.
Servomechanisms are used to control two movable ailerons installed to the right and left wings. Ailerons maintain the air balance of the convertiplane by regulating the up-down, right-left and rotational
movements in horizontal flight mode. The principles of
aircraft power system construction have been extensively analyzed in the literature [2, 3]. For this specific design, the functional block diagram of the convertiplane's electrical circuits is described in Figure 3.
Fig. 3. Functional block diagram of the electrical circuits of the convertiplane
ESC (Electronic speed controller) forms the power circuit, schematically located between battery and motor, connected to them by two and three wires, respectively. The size of the cross-sectional area of the five power wires is proportional to the value of the current flowing through them and their diameters are also larger than those of the signal wires due to the large current flow.
Conflicting issues need to be solved during the placing of ESCs. For example, electromagnetic fields around power cables can interfere the operation of
sensitive, mainly MEMS-type inertial navigation devices and GPS receivers, as well as flight controllers. To reduce the impact of electromagnetic interference and losses, it is advisable to shorten the length of power cables. On the other hand, in order to reduce the temperature, it is advisable to place the ESCs in the air flow created by the blades, for example, at a distance equal to half the radius of the blades from the center of the lifting motors. Thus, as an optimal solution, it was decided to place the ESCs on the bottom side of the motors. In this case, two power cables
Fig 4. View of the convertiplane's fuselage
connecting battery and ESC pass through the carbon tube, and the following advantages are obtained.
First, due to the electrical conductivity of carbon, the impact of electromagnetic interference coming from the wires to the surrounding devices is significantly reduced. Second, the lengths of power cables connecting engine and ESC are minimal. Finally, by choosing the same dimensions of the trays on which they are fastened, it is possible to install
engine and its ESC in a multi-layered way at the end of the carbon tube, resulting in a relatively simple design
[4].
The place and direction of the propulsion motor on the glider requires its ESC to be located inside the fuselage. In this case, in order to improve the temperature regime, it is advisable to select a relatively large ESC power reserve factor or to provide air flow that provides heat transfer through the fuselage [12-14].
Fig 5. Functions of FC, RC and GPS devices.
Power system. The power system of the convertiplane consists of two LiPo batteries (AB) connected in parallel and four voltage converters with stabilized output voltages. The operating voltage of each battery used as a power source is 22.2 V, power capacity is 5000 mAh. Voltage converters convert the relatively high voltage of batteries into the required low-value and stable voltages. The first supplies 5 V power to flight controller, the second 5 V to servomechanisms and the low-voltage circuit of the electronic speed controller of the thrust motor, the third 12 V to video transmitter and the fourth 8.4 V to camera. Except the voltage converters included in the components of flight controllers, the other voltage converters are assembled in one block and placed symmetrically to the central axis, between battery and flight controllers inside the fuselage.
The power system of the convertiplane is powered directly from the battery. Aircraft weighing up to 20 kg usually use one or more Li-Po batteries to provide the required power and flight time. The battery weighs more than the electrical equipment used in the convertiplane and has a significant effect on the equal distribution of the load on the motors. To maintain the transverse balance of aircraft, the batteries are placed symmetrically on the right and left sides relative to the center axis of a glider. To achieve the longitudinal balance of the aircraft, it must be taken into account that the propulsion engine is unmovably fixed to the rear of the glider. Therefore, it is possible to change the center of gravity of the aircraft by sliding the place of the batteries in the direction of the central axis, thus achieving an equal distribution of the load on the motors. In this case, the center of gravity of the aircraft falls on the point of intersection of the diagonal lines connecting the lifting engines diagonally (Fig. 2).
In general, the coordinates of the center of gravity of the glider can be calculated using the following known formulas:
X, =
ZGjXj
Y =
ZGiyj
(1)
here:
- Xt and Yt - coordinates of the aircraft's center of gravity;
- xi and yi - coordinates of the centers of gravity of the seperate parts of aircraft;
- Gi - weight of the seperate parts of aircraft;
- G - total weight of aircraft.
Figure 4 describes the location of UAV elements in fuselage from the top view.
Control and navigation system. The navigation system of the convertiplane consists of navigation devices, including GPS receiver, 3-axis gyroscope, 3-axis accelerometer, magnetometer and barometer. GPS is global positioning system, gyroscope and accelerometer are inertial navigation devices, magnetometer is used as an electronic compass, barometer - used to determine the relative flight altitude based on atmospheric pressure. The combined use of these systems improves the quality of the flight.
As mentioned above (Fig. 2), the center of gravity affects the stability of the aircraft. To increase the horizontal stability, it is advisable to place the center of gravity of the multi-rotor aircraft below the flatness of rotation of the blades, for example, at the level of the engines [5].
It is possible to ignore the weight of the flight controllers, GPS and radio control receivers used to control the convertiplane in the equal distribution of weights relative to the center of gravity of aircraft. In order to determine the installation place on glider, let's look at a diagram describing the relationship between
G
G
all three electronic devices in terms of similarities and differences in their functions (Fig. 5).
Performing the calculation operation as described in Figure 5 is a similar function of flight controller and GPS receiver. Two reports or coordinate systems are used to perform these operations, which include the processing of navigation data and the calculation of flight parameters that determine the position of the aircraft in space. The locations of both flight controller and GPS centers relative to the center of gravity of the aircraft must be known in the moving coordinate system at the center of gravity in order to properly assess their position in space.
Flight controllers can be located in the center of gravity of a multi-rotor aircraft or near the center of gravity. Problems that can occur when the flight controller is placed away from the center of gravity of the aircraft have not yet been observed [6].
GPS receiver is a navigation device that processes the received navigation data and its antenna and receiver are usually installed in the same case. The followings should be taken into account when placing GPS receiver on the aircraft:
1) GPS antenna should be aimed at the open sky by placing it on top of the aircraft to receive satellite signals carrying navigation information without impediment;
2) The GPS antenna should be as far away as possible from the aircraft's electromagnetic interference power supplies and wires.
GPS receiver can be placed on the flight controller installed in the center of gravity of the multi-rotor aircraft. However, due to the limited height of the fuselage of the convertiplane, installing the GPS receiver at a certain height above the flight controller by keeping the centers aligned on the vertical axis is both structurally difficult and reduces the aerodynamic quality of the glider. For this reason, it is not advisable to install a GPS receiver above the fuselage.
In order to solve the above-mentioned issues, GPS receiver was slid to the front in the direction of the central axis of the developed convertiplane and the upper surfaces of the receiver and the fuselage have been placed in the same flatness. At the same time, the distance measurements of the center of the GPS receiver on the x, y, z axes relative to the center of the flight controller are included in the coordinate section of the flight controller program. In this case, depending on the direction of sliding, a positive or negative sign is written in front of the measurement values in accordance with the operating instructions.
RC receiver. The location of RC receiver is not decisive relative e.g to center of gravity of the aircraft, because it does not perform calculation operations and the weight does not have a significant effect on the equal distribution of the load. During the installation of RC receiver, it's tried to ensure that the conductive elements of the aircraft structure do not interfere with its antenna in the direction of the ground. Also two directional antennas mounted at an angle of 90 degrees to each other are used to improve signal reception reliability. Thus, taking into account the small geometric dimensions, light weight and the fact that the
glider is made of radio-transparent material, it has been decided to place RC receiver in a section created
inside fuselage. During the convertiplane test flights, radio control at a distance of 500 m was reliably performed [6].
Camera. As mentioned earlier, convertiplane is designed for mapping, and the video camera used for this purpose is fixed from the front to the bottom of fuselage. The body of video camera is located inside fuselage to ensure equal weight distribution of aircraft relative to the center of gravity and to reduce impact on the aerodynamic quality of the glider. In this case, its lens come out of the fuselage and are directed to the ground during a horizontal flight.
OSD (on-screen display) - Provides telemetry data view on display image. The weight of OSD is very small and does not affect the balance conditions of aircraft. Due to the shortness of the input and output cables connected to video camera, flight controller and video transmitter, it is advisable to place it close to all three devices inside fuselage.
VideoLink - (video transmitter). Video transmitter provides image and telemetry data transmission to the ground, because its temperature is relatively high in the operating mode, it is advisable to place it outside fuselage. Thus, video transmitter is placed behind camera and installed to the bottom of fuselage.
DataLink - is a telemetry device for transmitting digital data over long distances. Two identical devices are used to create two-way "ground-to-air" communication. Due to the similar operating modes, the requirements for the location of video transmitter can also be applied to the on-board telemetry device. Because it works with longer-wavelength (lower-frequency) radio signals than a video transmitter and a GPS receiver, the location of telemetry device at the bottom or top of fuselage is not decisive. Taking into account that its weight affects the balance conditions and above mentioned issues, the telemetry device is placed close to the center axis of glider and installed on the top of fuselage.
One of the main requirements for the selection and development of components has been the optimization of the main parameters of the convertiplane-type UAV in the context of observation of strategic objects. For this purpose, the detection features of the developed convertiplane-type UAV by visual, acoustic and radar type detection means have been determined.
Surface reflection. The possibility of detecting the aircraft by various technical means during the flight remains a topical issue at the present time. The main parameter characterizing the probability of detection, used as a technical-confidential indicator, is the coefficient of surface reflection. Surface reflection depends on the overall dimensions of the aircraft and the parameters of the radar (generator) that generates the electromagnetic waves directed at it. According to the report and survey books, the value of the surface reflection coefficient of small aircraft is 0.1-0.01 m2 (10 ...- 20 dB). In medium-sized aircraft, the surface reflection is 30 m2 and higher. Taking into consideration that UAV is made of a dielectric-based
polymer-composite material, the electromagnetic waves generated by radar are absorbed by the surface of the aircraft and are not reflected. This feature reduces the chance of UAVs being detected by radars [7-8].
Acoustic detection. Due to the low volume of non-collector electric motors used in these aircrafts, the probability of detection of UAV by acoustic detection means is very low [9].
The visual detection coefficient depends on the illumination level of the aircraft and is calculated by the following formula (2).
P =
(2)
Here: Фг- a stream of light reflected from the surface; Ф0- stream of light falling on a surface.
The brightness range of light, which can be absorbed by the human visual system, is very large (10-6...106 kdm2). Design of the UAV in light blue (sky) color reduces the probability of its visual detection at low altitudes (200-300 m) [10-11].
The "ARAN-4" unmanned aerial vehicle, which has such positive qualities as vertical take-off and landing, long stay in the air and simplicity of design, as well as mapping, monitoring and observation of oil and gas industry facilities to ensure the safety of strategic assets are designed and developed at the National Aviation Academy of The Republic of Azerbaijan.
CONCLUSION The balance conditions, aerodynamic and electromagnetic compatibility requirements have been met during structural emplacement of the elements in the convertiplane type UAV. Static and dynamic balance conditions are achieved
by equal distribution of mass and forces relative to the center of gravity of the glider. In order to meet the aerodynamic requirements, the protrusions on the surface of the glider, which create the opposite aerodynamic forces, have been minimized and for meeting the requirements of electromagnetic compatibility, both electronic devices with sharply different operating frequencies were used and sensitive and power devices were placed at a certain distance and in a certain position. The insulation layer is made of electrical wires that are resistant to both high temperatures and mechanical impact.
The coordinates of the control and navigation devices relative to the center of gravity of the aircraft are taken into account in the program uploaded on the control unit. The directional diagrams of the antennas of radio-electronic devices are directed in the direction of the communication channel as much as possible. Because RC receiver is made of radio-transparent composite material, it allows to place it inside the fuselage.
Making of composite material has caused the surface reflection coefficient and weight of convertiplane-type UAV to be low and equipping it with radar devices, as well as non-collector electric
motors and making the glider in air color significantly reduced the probability of detection of the aircraft by acoustic and visual detection means.
References:
1. RN Nabiyev, AA Abdullayev. BpLA konvertoplanovoqo tipa: Tekushee sostoyanie I perspektivi. Estestvennie i texniceskie nauki. Moskva, 2021. №3 (154). p 146-162. doi: 10.25633/ ETN.2021.03.13
2. R N Nabiyev, G I Garayev, A A Abdullayev. Conceptual functional design of hybrid energy source of unmanned convertiplane. IOP Conference Series: Conference Scopus. Materials Science and Engineering. 862 (2020) 022043, doi:10.1088/1757-899X/862/2/022043.
3. Nebiyev R.N., Aabdullayev A.A., Qaraev Q.i. Razrabotka konceptualnoy funkcionalnoy sxemi bespi-lotnoqo konnvertoplan s qibridnim istocnikom enerqi. Aviakosmiceskoe priborostroenie. Moskva, 2021 q. № 5. s 1-16. doi: 10.25791/aviakosmos. 5.2021.1217
4. L.M. Savelev, i.S. Axmedyanov. Procnost letatelnix apparatov. Minobrnauki Possi, Samar. Qos. Aerokosm. Unt im. S.P.Koroleva. Samara, 2012. 274 p.
5. https://ardupilot. org/copter/docs/common-mounting-the-flight-controller.html
6. http://www.eagletreesystems.com/Manuals/ve ctor_new_rus.pdf
7. E.D. Filin, R.V. Kiricek. Metodi obnarujeniya molarazmernix BpLA na ocnove analiza elektromaqnitnoqo spektra. Informacionnie texnoloqii i telekommunikacii. 2018. Vol. 6. № 2. p 87-93.
8. S.A. Arbuzov, E.V. Qrickevic i t.d. izmerenie spektrialnix koefficentov otrojeniya poverxnostey pri multispektirialnoy vozdushnoy semke cifrovoy kamerey.
9. V.M. Kartashev, S.A. Sheyko i t.d. Osobennosti obnorujeniya i raspoznovaniya malix BpLA. ISSN0485-8972Radiotexnika. Moskva, 2018 q. № 1995. p 235-243.
10. А.А. Belov, E.N. Jidkov i t.d., "Sposob i ustroystva akusticeskoqo obnorujeniya i raspoznavaniya letatelnix apparatov". 10.07.2016 Byul. № 19.
11. S.O. Kozeruk, O.V. Korjik. Obnorujeniya malix letatelnix apparatov po akusticeskomu izluceniyu. Visnyk NTUU KPI Seriia-Radiotekhnika Radio aparat obuduvannia, 2019, Iss. 76, p.15-20.
12. F.P. Kurockin. Proektriovanie i konstrurivovanie samoletov s vertikalnim vzletom i posadkoy. M. Ma§hinistroenie, 1977. 224 p.
13. E. D. Krilov. Metodika proektirovaniyz konstrukciy BpLA iz kompozicionnix materialo. Aktualnie problemi aviaci i kosmanaftiki. Texniceskoe nauke. Moskva, p 96-97.
14. N.V. Cistiyakov, А.А. Silkin, i t.d., Razrabotka BpLA dlya aerofotosiyomki i monitorinqa mestnosti. Doklad na simpoziuma "Nedelya Qornyaka - 98" М., MQQU. p 1-4.
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