Distributed tilt rotor solar unmanned aerial vehicle and design method thereof

Abstract

The invention discloses a distributed tilt rotor solar unmanned aerial vehicle and a design method thereof. The method may include: calculating solar radiation intensity; calculating the total weight of the unmanned aerial vehicle by combining energy balance and power balance according to the design input and the initial value of the flight weight, and iteratively optimizing the flight weight; component parameters of the distributed tilt-rotor solar unmanned aerial vehicle are designed. According to the solar unmanned aerial vehicle, short-distance take-off and landing can be achieved, and due to the good transverse stability, part of crosswind can be resisted, so that the solar unmanned aerial vehicle can have good take-off and landing performance and take-off and landing safety.

Description

Technical Field

[0001] The present invention relates to the field of solar-powered unmanned aerial vehicles, and more specifically, to a distributed tilt-rotor solar-powered unmanned aerial vehicle and a design method thereof. Background Art

[0002] A solar-powered drone is an unmanned aerial vehicle that uses solar energy as its sole energy source. It has the characteristics of high flight altitude, long flight time, and clean energy, and has good application prospects.

[0003] Due to the characteristics of their take-off and landing methods, conventional solar-powered UAVs need to rely on their wings to generate lift to get the UAV off the ground, which inevitably requires them to reach a certain speed before they can take off, and they also need a longer runway for takeoff. In addition, the airflow environment encountered by the UAV on the ground is relatively complex, and the crosswind direction changes on the runway are disorderly, which also has a great impact on the takeoff safety of the solar-powered UAV.

[0004] Therefore, it is necessary to develop a distributed tilt-rotor solar-powered UAV and its design method.

[0005] The information disclosed in the background technology section of the present invention is only intended to deepen the understanding of the general background technology of the present invention, and should not be regarded as acknowledging or suggesting in any form that the information constitutes the prior art already known to those skilled in the art. Summary of the invention

[0006] The present invention proposes a distributed tilt-rotor solar-powered UAV and a design method thereof, which can achieve short-distance takeoff and landing, and due to its good lateral stability, can resist part of the side wind, so that the solar-powered UAV can have good take-off and landing performance and take-off and landing safety.

[0007] In a first aspect, an embodiment of the present disclosure provides a distributed tilt-rotor solar-powered UAV, comprising:

[0008] The left fuselage and the right fuselage are connected by the 0# wing section;

[0009] The left 1# wing section and the right 1# wing section are connected to the outer sides of the left fuselage and the right fuselage respectively;

[0010] The tilting nacelle is arranged at the end of the 1# wing section away from the fuselage;

[0011] The tilt rotor is arranged on the tilt nacelle.

[0012] In a second aspect, the present disclosure also provides a design method, including:

[0013] Calculate solar radiation intensity;

[0014] Based on the design input and the initial value of the flight weight, the total weight of the UAV is calculated by combining the energy balance and power balance, and the flight weight is optimized iteratively;

[0015] The component parameters of the distributed tilt-rotor solar-powered UAV are designed.

[0016] Preferably, calculating the solar radiation intensity includes:

[0017] Calculate the distance factor f between the Earth and the Sun:

[0018] f=1+k1 cos(2πn day / 365)

[0019] Where: k1 is the adjustment coefficient, n day is the day ordinal number;

[0020] Calculate the solar radiation intensity E in the Earth's atmosphere SC :

[0021]

[0022] Where: C is the absorption of the inhomogeneous atmosphere, A is the average molar absorption coefficient of the atmosphere, and S0 is the solar constant.

[0023] Preferably, the total weight of the UAV is calculated based on the design input and the initial value of the flight weight in combination with the energy balance and the power balance, and the flight weight is iteratively optimized including:

[0024] Calculate flight power for climb, day cruise, and night cruise;

[0025] Determine the energy balance equation based on the energy consumption during the flight phase and the power consumption of the load during the day and at night;

[0026] The total weight of the drone is determined based on energy balance, power balance, and difference calculation with the initial weight.

[0027] Preferably, calculating the flight power for climb, daytime cruise, and nighttime cruise includes:

[0028] Calculate the power P required for the climb phase climb :

[0029]

[0030] Where: F1 is the part of the lift borne by the wing during flight, is the climb rate, η pro is the propulsion system efficiency, P0 is the power consumed by the tiltrotor;

[0031] Calculate the daytime cruising power P cruise_day :

[0032] P cruise_day =k1mgV day / K / η pro +k2v day / K / η rotor

[0033] Where: k1 and k2 are the proportions of thrust generated by the thrust propeller and the pull generated by the tilt rotor, respectively, η pro and η rotor for the efficiency of thrust propellers and tilt rotors;

[0034] Calculate the night cruising power P cruise_night :

[0035] P cruise-night =K0(k1mgV / K / η pro +k2mgV / K / η rotor )

[0036] Where: K0 is the ratio of power consumed at night cruising altitude to that consumed at daytime cruising altitude.

[0037] Preferably, the energy balance relationship is determined based on the energy consumption during the flight phase and the power consumption of the load during the day and at night, including:

[0038] The distributed tilt-rotor solar UAV starts to climb according to the sunrise time of the day. The climbing time of the UAV is calculated as t1 according to the climb rate performance, and the descent time t3 is calculated according to the descent rate. The remaining time is the daytime cruising time t2 and the nighttime cruising time t4. The energy consumption of the flight stage is:

[0039] E day =P climb t1+P cruise_day t2+P slip t3

[0040] E night =P cruise_night t4

[0041] Then the power consumption of the load during the day and at night is calculated as:

[0042] E pld_day =P pld (t1+t2+t3)

[0043] E pld_night =P pld t4

[0044] The energy consumed by the onboard equipment of the distributed tilt-rotor solar drone is E av_day and E av_night ;

[0045] Then the energy balance equation is obtained:

[0046] E bat =E night +E pld_night +E av_night

[0047] E sc =E day +E pld_day +E av_day +E night +E pld_night +E av_night

[0048] Among them, E bat and E sc They are the energy supply required by energy storage batteries and solar cells respectively.

[0049] Preferably, based on energy balance, power balance, and difference calculation with the initial weight, determining the total weight of the drone includes:

[0050] The total weight of the drone is calculated by adding up all the parts of the drone and calculating the difference between the total weight and the initial weight until |(m tota l-m0) / m0|≤0.01, and iterate to form the final total weight of the UAV.

[0051] Preferably, the total weight of the drone is calculated by adding up all the components of the drone:

[0052] m total =m mppt +m fuse +m wing +m sc +m wire +m rotor +m pro +m bat +m pld +m tilt

[0053] Among them, m total is the total weight of the drone, m bat is the weight of the energy storage battery, m wing is the wing weight, m fuse is the fuselage weight, m rotor is the tiltrotor weight, m sc is the weight of the solar cell, m mpp t is the weight of the power controller, m wire is the weight of the onboard cable, m pro The weight of the propulsion system.

[0054] Preferably, the tilt rotor weight m rotor Including the weight of the rotor, hub, mounting parts and spinner cap, it is:

[0055]

[0056] Where: r , P r ,Ω r , R r , A2 and F r They are the solidity, rotor load, rotation speed, radius, adjustment coefficient and generated pulling force of the tiltrotor respectively;

[0057] Solar cell weight m sc for:

[0058] m sc =ρ sc S sc

[0059] Where: sc is the solar cell array density, S sc The solar cell patch area is:

[0060] S sc =E sc / (E sc0 η sc η c η mppt )

[0061] Where: E sc0 is the energy of photoelectric conversion per unit area of ​​solar cells, η sc is the photovoltaic conversion efficiency of the solar array, η c is the solar cell array loss efficiency, η mppt is the power controller efficiency;

[0062] Power Controller Weight m mppt for:

[0063] m mppt =1280S sc η sc η c / K mppt

[0064] Where: S sc is the solar cell patch area, η sc is the photoelectric conversion efficiency, η c is the loss efficiency, K mppt is the power-to-weight ratio of the power controller.

[0065] Preferably, the design of the parameters of the tilt-rotor of the distributed tilt-rotor solar-powered UAV includes:

[0066] Input the initial parameters of the tiltrotor, including design thrust T, rotation speed Ω, undercut R0, number of blades k, air density ρ, inflow velocity V, and rotor radius R;

[0067] Divide the rotor blade into n blade elements, determine the airfoil distribution at each section, and input the optimal angle of attack and lift-drag coefficient at the airfoil section;

[0068] The Lagrange multiplier K is solved by the following formula:

[0069]

[0070] Calculate the conversion angle and induced attack angle α i , and then solve the rotor blade chord length b at each characteristic section i :

[0071]

[0072] The corresponding induced velocity v is solved by momentum-blade element theory i and the incoming flow angle β * :

[0073]

[0074] Then solve the installation angle:

[0075] θ=β * +α i +α best .

[0076] The methods and apparatus of the present invention have other features and advantages that will be apparent from, or will be described in detail in, the accompanying drawings and subsequent detailed descriptions incorporated herein, which together serve to explain the specific principles of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0077] The above and other objects, features and advantages of the present invention will become more apparent through a more detailed description of exemplary embodiments of the present invention in conjunction with the accompanying drawings, wherein like reference numerals generally represent like components throughout the exemplary embodiments of the present invention.

[0078] Figure 1 A front view of a distributed tilt-rotor solar-powered UAV according to an embodiment of the present invention is shown.

[0079] Figure 2A top view of a distributed tilt-rotor solar-powered UAV according to an embodiment of the present invention is shown.

[0080] Figure 3 A schematic diagram of a distributed tilt-rotor solar-powered UAV in take-off / rolling state according to an embodiment of the present invention is shown.

[0081] Figure 4 A schematic diagram of a tilt transition state of a distributed tilt-rotor solar-powered UAV according to an embodiment of the present invention is shown.

[0082] Figure 5 A schematic diagram of a distributed tilt-rotor solar-powered UAV in cruising and level flight state according to an embodiment of the present invention is shown.

[0083] Figure 6 A flow chart showing the steps of a design method according to an embodiment of the present invention.

[0084] Figure 7 A schematic diagram of a distributed tilt-rotor solar-powered UAV flight mission profile according to an embodiment of the present invention is shown.

[0085] Figure 8 A schematic diagram showing the overall design process of a distributed tilt-rotor solar-powered UAV according to an embodiment of the present invention is shown.

[0086] Description of reference numerals:

[0087] 1. Tilt-rotor; 2. Wing; 3. Thrust propeller; 4. Fuselage; 5. Vertical tail; 6. Horizontal tail; 7. Tilt-rotor nacelle; 8. Power strut; 9. 1# wing section; 10. 0# wing section; 11. 1# wing section. DETAILED DESCRIPTION

[0088] The preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein.

[0089] To facilitate understanding of the solutions and effects of the embodiments of the present invention, two specific application examples are given below. Those skilled in the art should understand that the examples are only for facilitating understanding of the present invention, and any specific details thereof are not intended to limit the present invention in any way.

[0090] Example 1

[0091] A distributed tilt-rotor solar-powered UAV, comprising:

[0092] The left fuselage and the right fuselage are connected by the 0# wing section;

[0093] The left 1# wing section and the right 1# wing section are connected to the outer sides of the left fuselage and the right fuselage respectively;

[0094] The tilting nacelle is arranged at the end of the 1# wing section away from the fuselage;

[0095] The tilt rotor is installed on the tilt nacelle.

[0096] Figure 1 A front view of a distributed tilt-rotor solar-powered UAV according to an embodiment of the present invention is shown.

[0097] Figure 2 A top view of a distributed tilt-rotor solar-powered UAV according to an embodiment of the present invention is shown.

[0098] Specifically, Figure 1-Figure 2 As shown, the distributed tilt-rotor solar-powered UAV comprises: a tilt-rotor 1, a wing 2, a thrust propeller 3, a fuselage 4, a vertical tail 5, a horizontal tail 6, a tilt-nacelle 7, a power strut 8, a wing section 1# 9, a wing section 0# 10, a wing section 1# 11, a solar cell (laid on the upper surface of the wing or fuselage), a tilt-rotor servo, an energy cell, etc. The truss structure of the wing section 0# 10 is connected to the fuselage structure frame of the fuselage 4 on both sides, the inner truss structure of the wing section 1# 9 is connected to the structure frame of the fuselage 4, and the tilt-nacelle 7 is connected to the tilt-rotation shaft located at the leading edge of the wing section 1# 9, the tilt-rotation shaft is installed in the wing truss through a bearing and a bearing bracket, the tilt-rotation servo is located in the tilt-rotor servo 7, and is meshed with the gear at the other end of the tilt-rotation shaft through a gear, and the tilt-rotor servo controls the tilt-rotor 1 and the tilt-nacelle 7 to achieve a tilt of 0° (horizontal state) to 90° (vertical state), and the mechanism structure is bilaterally symmetrical.

[0099] Figure 3 A schematic diagram of a distributed tilt-rotor solar-powered UAV in take-off / rolling state according to an embodiment of the present invention is shown.

[0100] Distributed tilt-rotor solar-powered UAV take-off and run status Figure 3 As shown, the tilt rotors 1 at both ends provide lift vertically upward, and the thrust propellers 3 provide forward sliding power to make the wings 4 generate lift to provide lift for the solar-powered UAV to take off and land, so as to climb until it reaches a specified height.

[0101] Figure 4 A schematic diagram of a tilt transition state of a distributed tilt-rotor solar-powered UAV according to an embodiment of the present invention is shown.

[0102] Figure 5 A schematic diagram of a distributed tilt-rotor solar-powered UAV in cruising and level flight state according to an embodiment of the present invention is shown.

[0103] like Figure 4-Figure 5 As shown, when the distributed tilt-rotor solar-powered UAV climbs to the cruising altitude, it enters the tilt transition stage, and the tilt-rotors 1 at both ends perform a tilt transition until the wings 4 can fully provide lift to overcome the gravity of the UAV, then it enters the cruise level flight state to perform level flight and perform the mission.

[0104] Distributed tilt-rotor solar drones can be used in the following ways:

[0105] (1) In the ground state, the distributed tilt-rotor solar-powered UAV launcher is lowered, and the thrust propeller rotates to generate forward thrust, and the tilt-rotors on both sides rotate to generate upward lift. During the taxiing process, the wings continue to increase force. In order to reduce energy consumption, the rotors slightly unload force until the lift is greater than the gravity. The UAV takes off, leaves the ground, and begins to climb;

[0106] (2) When the UAV continues to climb to the daytime cruising altitude, the tilt-rotor begins to tilt transition until it tilts 90 degrees to the horizontal position, and together with the thrust propeller, it provides forward thrust. At this time, the speed of the thrust propeller can be slightly reduced, and the UAV is in a completely horizontal navigation state. When the solar energy is insufficient, the UAV descends without power to the night cruising state, and turns on the tilt-rotor and thrust propeller to maintain the altitude and enter the night cruising state;

[0107] (3) Before the drone lands, the landing gear needs to be deployed and the tilt-rotor can be tilted back to the vertical upward position to adjust the attitude and then land safely.

[0108] Compared with traditional solar drones, distributed tilt-rotor solar drones have better take-off and landing performance, can achieve shorter take-off distances, and have better climbing performance, that is, they have a larger climb rate, can cross the strong wind layer more quickly, and improve the safety of the drone; they have better lateral stability. For distributed tilt-rotor solar drones, they can have better resistance to side winds and have a safer take-off environment. At the same time, when descending and climbing, they can shorten a certain retreat distance, which is more convenient and safe for the control of flight airspace; distributed tilt-rotor solar drones have a smaller descent rate when landing, which reduces the impact load of the drone when landing and reduces damage to the landing gear.

[0109] Example 2

[0110] Figure 6 A flow chart showing the steps of a design method according to an embodiment of the present invention.

[0111] like Figure 6 As shown, the design method includes:

[0112] Step 101, calculating the solar radiation intensity;

[0113] Step 102, calculating the total weight of the UAV based on the design input and the initial value of the flight weight in combination with the energy balance and the power balance, and iteratively optimizing the flight weight;

[0114] Step 103, designing the component parameters of the distributed tilt-rotor solar-powered UAV.

[0115] In one example, calculating solar radiation intensity includes:

[0116] Calculate the distance factor f between the Earth and the Sun:

[0117] f=1+k1 cos(2πn day / 365)

[0118] Where: k1 is the adjustment coefficient, n day is the day ordinal number;

[0119] Calculate the solar radiation intensity E in the Earth's atmosphere SC :

[0120]

[0121] Where: C is the absorption of the inhomogeneous atmosphere, A is the average molar absorption coefficient of the atmosphere, and S0 is the solar constant.

[0122] In one example, based on the design input and the initial value of the flight weight, the total weight of the UAV is calculated in combination with the energy balance and the power balance, and the flight weight is iteratively optimized including:

[0123] Calculate flight power for climb, day cruise, and night cruise;

[0124] Determine the energy balance equation based on the energy consumption during the flight phase and the power consumption of the load during the day and at night;

[0125] The total weight of the drone is determined based on energy balance, power balance, and difference calculation with the initial weight.

[0126] In one example, calculating flight power for climb, day cruise, and night cruise includes:

[0127] Calculate the power P required for the climb phase climb :

[0128]

[0129] Where: F1 is the part of the lift borne by the wing during flight, is the climb rate, η pro is the propulsion system efficiency, P0 is the power consumed by the tiltrotor;

[0130] Calculate the daytime cruising power P cruise_day :

[0131] P cruise_day =k1mgV day / K / η pro +k2v day / K / η rotor

[0132] Where: k1 and k2 are the proportions of thrust generated by the thrust propeller and the pull generated by the tilt rotor, respectively, η pro and η rotor for the efficiency of thrust propellers and tilt rotors;

[0133] Calculate the night cruising power P cruise_night :

[0134] P cruise-night =K0(k1mgV / K / η pro +k2mgV / K / η rotor )

[0135] Where: K0 is the ratio of power consumed at night cruising altitude to that consumed at daytime cruising altitude.

[0136] In one example, determining the energy balance relationship according to the energy consumption of the flight phase and the power consumption of the load during the day and at night includes:

[0137] The distributed tilt-rotor solar UAV starts to climb according to the sunrise time of the day. The climbing time of the UAV is calculated as t1 according to the climb rate performance, and the descent time t3 is calculated according to the descent rate. The remaining time is the daytime cruising time t2 and the nighttime cruising time t4. The energy consumption of the flight stage is:

[0138] E day =P climb t1+P cruise_day t2+P slip t3

[0139] E night =P cruise_night t4

[0140] Then the power consumption of the load during the day and at night is calculated as:

[0141] E pld_day =P pld (t1+t2+t3)

[0142] E pld_night =P pld t4

[0143] The energy consumed by the onboard equipment of the distributed tilt-rotor solar drone is E av_day and E av_night ;

[0144] Then the energy balance equation is obtained:

[0145] E bat =E night +E pld_night +E av_night

[0146] E sc =E day +E pld_day +E av_day +E night +E pld_night +E av_night

[0147] Among them, E bat and E sc They are the energy supply required by energy storage batteries and solar cells respectively.

[0148] In one example, based on energy balance, power balance, and difference calculation with initial weight, determining the total weight of the drone includes:

[0149] The total weight of the drone is calculated by adding up all the parts of the drone and calculating the difference between the total weight and the initial weight until |(m total -m0) / m0|≤0.01, and iterate to form the final total weight of the UAV.

[0150] In one example, the total weight of the drone is calculated by adding up all the parts of the drone:

[0151] m total =m mppt +m fuse +m wing +m sc +m wire +m rotor +m pro +m bat +m pld +m tilt

[0152] Among them, m total is the total weight of the drone, m bat is the weight of the energy storage battery, m wing is the wing weight, m fuse is the fuselage weight, m rotor is the tiltrotor weight, m sc is the weight of the solar cell, m mppt is the weight of the power controller, m wireis the weight of the onboard cable, m pro The weight of the propulsion system.

[0153] In one example, the tiltrotor weight m rotor Including the weight of the rotor, hub, mounting parts and spinner cap, it is:

[0154]

[0155] Where: r , P r ,Ω r , R r , A2 and F r They are the solidity, rotor load, rotation speed, radius, adjustment coefficient and generated pulling force of the tiltrotor respectively;

[0156] Solar cell weight m sc for:

[0157] m sc =ρ sc S sc

[0158] Where: sc is the solar cell array density, S sc The solar cell patch area is:

[0159] S sc =E sc / (E sc0 η sc η c η mppt )

[0160] Where: E sc0 is the energy of photoelectric conversion per unit area of ​​solar cells, η sc is the photovoltaic conversion efficiency of the solar array, η c is the solar cell array loss efficiency, η mppt is the power controller efficiency;

[0161] Power Controller Weight m mpp t for:

[0162] m mppt =1280S sc η sc η c / K mppt

[0163] Where: S sc is the solar cell patch area, η sc is the photoelectric conversion efficiency, η c is the loss efficiency, Kmppt is the power-to-weight ratio of the power controller.

[0164] In one example, designing parameters of a tilt-rotor for a distributed tilt-rotor solar-powered UAV includes:

[0165] Input the initial parameters of the tiltrotor, including design thrust T, rotation speed Ω, undercut R0, number of blades k, air density ρ, inflow velocity V, and rotor radius R;

[0166] Divide the rotor blade into n blade elements, determine the airfoil distribution at each section, and input the optimal angle of attack and lift-drag coefficient at the airfoil section;

[0167] The Lagrange multiplier K is solved by the following formula:

[0168]

[0169] Calculate the conversion angle and induced attack angle α i , and then solve the rotor blade chord length b at each characteristic section i :

[0170]

[0171] The corresponding induced velocity v is solved by momentum-blade element theory i and the incoming flow angle β * :

[0172]

[0173] Then solve the installation angle:

[0174] θ=β * +α i +α best .

[0175] Specifically, the general design method of a conventional solar-powered UAV utilizes the basic principles of weight invariance and energy invariance. Here, a general parameter design method suitable for a distributed tilt-rotor solar-powered UAV is presented.

[0176] Figure 7 A schematic diagram of a distributed tilt-rotor solar-powered UAV flight mission profile according to an embodiment of the present invention is shown.

[0177] First, the flight mission profile of the distributed tilt-rotor solar UAV needs to be given, such as Figure 7 As shown, it is divided into the climbing phase, the daytime cruising flight phase, the descent phase, and the night cruise phase, which are repeated repeatedly until the mission is completed and the descent landing phase is entered.

[0178] Figure 8A schematic diagram showing the overall design process of a distributed tilt-rotor solar-powered UAV according to an embodiment of the present invention is shown.

[0179] like Figure 8 As shown, the specific design process is:

[0180] (1) Determine the design time point and design input parameters;

[0181] The design time point is selected as the time point with the weakest solar radiation intensity in the local latitude (summer solstice in the southern hemisphere and winter solstice in the northern hemisphere), and the initial take-off weight m0. The calculation method of solar radiation intensity in a day is:

[0182] ① Calculate the distance coefficient f between the earth and the sun

[0183] Due to the rotation and revolution of the earth in a year, its distance from the sun is constantly changing, so it is necessary to solve the distance coefficient between the sun and the earth:

[0184] f=1+k1cos(2πn day / 365)

[0185] In the formula: k1 is the adjustment coefficient, which is 0.032, n day It is the day number, that is, the number of days from January 1st.

[0186] ②Calculate solar radiation intensity

[0187] The intensity of solar radiation in the Earth's atmosphere is E SC :

[0188]

[0189] Where: C is the absorption of the inhomogeneous atmosphere, A is the average molar absorption coefficient of the atmosphere, S0 is the solar constant, which is 1367W / m 2 , where C is calculated as:

[0190] C=γp a A / (m a g)

[0191] Where: p a is the atmospheric pressure at the corresponding height, γ is the proportionality coefficient, that is, the ratio of the atmospheric concentration to the atmospheric density at the local sea level, is the average molecular mass of air, which is 28.97 g / mol, is the solar zenith angle, and its calculation formula is:

[0192]

[0193] Where: L a is the latitude of the calculated location, τ is the sun’s tail angle, t aFor true solar time, the expression of the above calculation quantity is:

[0194] τ=23.45°sin[2π(n day +284) / 365

[0195] t a =t±(L a -L as ) / 15+e s

[0196] Where: L as The geographical longitude used to calculate the local standard time, e s The time difference between true solar time and mean solar time is calculated as follows:

[0197] e s =0.1645sin2B-0.1255cosB-0.025sinB

[0198] B=2π(n day -81) / 365

[0199] (2) Based on the design input and initial weight value, the total weight m of the UAV is calculated by combining energy balance, force balance and power balance. total ;

[0200] ① Determine the optimal lift coefficient cl and calculate the drag coefficient cd and the daytime and nighttime cruising speed V day and V night ;

[0201] Through the two-dimensional airfoil analysis software profili and the three-dimensional aerodynamic analysis software xflr and CFD, the wing airfoil and the optimal angle of attack and the corresponding lift-drag coefficient suitable for the solar-powered UAV and the flight state altitude of this article are selected; then the cruising flight speed at the corresponding daytime altitude and nighttime altitude is calculated by the balance of forces, and the calculation formula is as follows:

[0202]

[0203] Where: L and D are lift and drag respectively, c l and c d is the calculated lift-drag coefficient, K and S are the lift-drag ratio and wing area, and V is the flight speed to be calculated. The calculation formula is expressed as follows:

[0204] S=b 2 / A

[0205] Where: b is the designed wing span, A is the aspect ratio, which can be estimated based on experience.

[0206] ② Calculate the flight power for climb, daytime cruise, descent, and night cruise

[0207] (a) Power required during the climb phase: P climb

[0208]

[0209] Where: F1 is the part of the lift borne by the wing during flight, is the climb rate, which varies with altitude, η pro To propel the system efficiency, P0 is the power consumed by the tiltrotor, which includes the sum of the rotor's drag power, induced power and waste power divided by the motor efficiency. The specific calculation method can be found in "Aerodynamic Manual Volume 6". The basic idea is to convert the thrust required by the rotor into a thrust coefficient, refer to the thrust power coefficient table, and combine the formula to calculate the drag power. The waste power is calculated by obtaining the waste coefficient of the entire aircraft through CFD, and the induced power is calculated through uniform inflow of momentum-blade element theory.

[0210] (b) Daytime cruising power P cruise_day

[0211] P cruise_day =k1mgV day / K / η pro +k2v day / K / η rotor

[0212] Where: k1 and k2 are the proportions of thrust generated by the thrust propeller and the pull generated by the tilt rotor, respectively, η pro and η rotor The efficiency of the thrust propeller and the tilt rotor.

[0213] (c) Glide power P slip

[0214] It is usually 0, and the strategy adopted is unpowered decline.

[0215] (d) Night cruising power P cruise_night

[0216] P cruise-night =K0(k1mgV / K / η pro +k2mgV / K / η rotor )

[0217] Where: K0 is the ratio of the power consumed at night cruising altitude to that consumed at daytime cruising altitude, and its calculated value is determined based on the flight altitudes of the two.

[0218] ③ Calculate energy consumption

[0219] Determine the time required for each flight stage in turn. Generally, the distributed tilt-rotor solar drone starts to climb according to the sunrise time of the day, and then calculates the climbing time of the drone as t1 according to the climb rate performance, and calculates the descent time t3 according to the descent rate. The remaining time is the daytime cruising time t2 and the nighttime cruising time t4. The energy consumption of the flight stage is:

[0220] E day =P climb t1+P cruise_day t2+P slip t3

[0221] E night =P cruise_night t4

[0222] If the drone needs to carry a payload, the power and energy consumption of the payload must be calculated. The power and energy consumption of the payload during the day and at night are:

[0223] E pld_day =P pld (t1+t2+t3)

[0224] E pld_night =P pld t4

[0225] In addition, the energy consumed by the distributed tilt-rotor solar-powered UAV’s onboard equipment is E av_day and E av_night .

[0226] According to the energy consumption characteristics of the distributed tilt-rotor solar-powered UAV, the energy balance equation can be obtained as follows:

[0227] E bat =E night +E pld_night +E av_night

[0228] E sc =E day +E pld_day +E av_day +E night +E pld_night +E av_night

[0229] The above E bat and E sc They are the energy supply required by energy storage batteries and solar cells respectively.

[0230] ④ Calculate and estimate the weight of each system

[0231] The weight estimation of distributed tilt-rotor solar-powered UAV is based on the actual weight of the existing components, such as the load weight m pld , Tilt mechanism weight m tilt Etc., while the remaining parts can be estimated based on statistical data and the existing technical level.

[0232] (a) Energy storage battery weight m bat

[0233] The weight of the energy storage battery is calculated based on the required energy of the energy storage battery obtained above, which can be expressed as:

[0234] m bat =E bat / K bat

[0235] In the above formula: K bat It is the energy density of the energy storage battery, in Wh / kg.

[0236] (b) Wing weight m wing

[0237] The wing weight includes the weight of the wing skin and internal structure, and its calculation formula is as follows:

[0238] m wing =A0S 0.556 A 0.651

[0239] In the above formula: A0 is the adjustment coefficient, which is related to factors such as the unmanned machine shape and material.

[0240] (c) Body weight

[0241] The weight of the fuselage includes the weight of the fuselage skin, tail and fuselage structure, which can be expressed as:

[0242] m fuse =A1S f 0.24 F 0.687

[0243] In the above formula: A1 is the adjustment coefficient, which is related to the unmanned machine configuration, materials and other factors, S f is the fuselage wetted area, and F is the fuselage slenderness ratio.

[0244] (d) Tilt rotor weight m rotor

[0245] The weight of the tilt rotor includes the weight of the rotor, the weight of the hub, and the weight of the mounting components and the rotor cap. The estimated formula is:

[0246]

[0247] In the above formula: r , P r ,Ω r , R r , A2 and F r They are respectively the solidity of the tiltrotor, the rotor load, the rotation speed, the radius, the adjustment coefficient and the thrust generated.

[0248] (e) Solar cell weight m sc

[0249] m sc =ρ sc S sc

[0250] Where: sc is the solar cell array density, which is 0.6kg / m 2 , S sc is the solar cell paving area, which is related to the energy required for the solar UAV flight mission and the solar radiation energy. The calculation formula is as follows:

[0251] S sc =E sc / (E sc0 η sc η c η mppt )

[0252] Where: E sc0 is the energy of photoelectric conversion per unit area of ​​solar cells, η sc is the photovoltaic conversion efficiency of the solar array, η c is the solar cell array loss efficiency, η mppt is the power controller efficiency.

[0253] (f) Weight of power controller m mppt

[0254] m mppt =1280S sc η sc η c / K mppt

[0255] Where: S sc is the solar cell patch area, η sc is the photoelectric conversion efficiency, η c is the loss efficiency, K mppt is the power-to-weight ratio of the power controller.

[0256] (g) Weight of airborne cable m wire

[0257] m wire =0.12(msc +m bat )

[0258] (h) Propulsion system weight m pro

[0259] m pro =P pro_climb / K pro

[0260] Where: K pro is the power-to-weight ratio of the propulsion system.

[0261] (I) Total weight of the machine (m) total

[0262] The total weight of the drone is calculated by adding up all the previous parts and then subtracting it from the initial weight until |(m total -m0) / m0|≤0.01, and iterate to form the final weight.

[0263] m total =m mppt +m fuse +m wing +m sc +m wire +m rotor +m pro +m bat +m pld +m tilt

[0264] (3) Design the overall parameters of the pneumatic components of the entire aircraft

[0265] ① Tilt-rotor design

[0266] The design of the tilt-rotor must provide lift while generating a large propulsion force during forward flight. Therefore, an efficient design method should be adopted for the design of the tilt-rotor. Here, an improved design method based on the Angelo design method is used and combined with momentum-blade element and vortex theory for optimization design. The specific design method is as follows:

[0267] a. First, input the initial parameters, such as design thrust, rotation speed, undercut, number of blades, air density, inflow velocity, and rotor radius;

[0268] b. Divide the rotor blade into n blade elements, determine the airfoil distribution at each section, and input the optimal angle of attack and lift-drag coefficient at the airfoil section;

[0269] c. Solve the Lagrange multiplier K, which is calculated as follows:

[0270]

[0271] d. Calculate the conversion angle and induced attack angle α i , and then solve the rotor blade chord length b at each characteristic section i , and its calculation formula is as follows:

[0272]

[0273] e. Calculate the installation angle θ

[0274] The corresponding induced velocity v is solved by momentum-blade element theory i and the incoming flow angle β * :

[0275]

[0276] Then solve the installation angle: θ = β * +α i +α best . Then the final geometric appearance parameters of the tilt-rotor can be obtained.

[0277] ②Thrust propeller design

[0278] The thrust propeller is designed based on vortex theory. The specific design process is as follows:

[0279] a. Given the axial flow velocity V0, propeller diameter D, propeller rotation speed n, blade installation angle θ, number of blades N, and blade chord length b.

[0280] b. Calculate the given parameters of each blade element: circumferential velocity Vt, geometric angle of attack Solidity σ and incoming flow Mach number Ma.

[0281] c. Calculate the aerodynamic characteristics of each blade element within a certain range of Mach number and angle of attack.

[0282] d. Use Newton's iteration method to determine the interference angle of each blade element.

[0283] e. Calculate the actual air flow velocity angle φ, axial velocity interference coefficient a, annular velocity interference coefficient a0, tension coefficient Tc, and torque coefficient Qc.

[0284] f. Calculate the total aerodynamic force of the propeller using the calculation results of each blade element. The thrust, torque and efficiency of the propeller are:

[0285]

[0286] Until the required pulling force data is obtained, the final thrust propeller data is obtained.

[0287] ③Wing design

[0288] The design of the wing includes the design of geometric parameters such as the wing span, aspect ratio, wing root chord length, wing tip chord length, and installation angle.

[0289] Select the daytime cruising altitude as the design point, then select the airfoil based on the calculated Reynolds number and select the optimal angle of attack as the installation angle and the corresponding lift coefficient, and then select the appropriate aspect ratio. The reference area S of the wing can be calculated based on the aspect ratio formula, lift calculation formula or lift-to-drag ratio formula, as shown in the following formula.

[0290]

[0291] Then we can further calculate the wing root chord length c root and wing tip chord length c tip , expressed as:

[0292]

[0293] Where: λ is the tip-root ratio.

[0294] ④ Tail wing design

[0295] The tail of the distributed tilt-rotor solar UAV provides the UAV with longitudinal balancing torque, increases longitudinal stability and heading torque during flight. The tail capacity method is used to calculate the tail design, and the calculation formula is:

[0296]

[0297] Where: C VT , C HT The tail capacity coefficients of the vertical tail and the horizontal tail are respectively, S VT , S HT They are the areas of the vertical tail and the horizontal tail, L VT , L HT They are the moment arms of the vertical tail and the horizontal tail respectively.

[0298] ⑤Body design

[0299] The design of the fuselage needs to consider its loading conditions and internal load arrangement constraints, and then obtain its shape constraint input, mainly the fuselage length l F , slenderness ratio λ F , equivalent diameter d F And the maximum cross-sectional area of ​​the fuselage A F Calculate constraints, then use 3D modeling software CATIA to design the surface sketch, and then optimize the 3D model to get the final fuselage shape. The specific parameter calculation formula is as follows:

[0300] l F =aW c

[0301] d F = l F / λ F

[0302]

[0303] In the above formula: a and c are equivalent coefficients, which are obtained based on statistical data and are related to the type and material of the aircraft; W is the total weight of the aircraft.

[0304] After the aerodynamic shape design of the distributed tilt-rotor solar-powered UAV is completed, the detailed design can then be carried out.

[0305] The overall design method of the distributed tilt-rotor solar UAV is to calculate based on the appropriate flight mission profile based on force balance, power balance, energy balance and other methods, and then iteratively calculate to obtain the final weight parameters; then, based on the momentum theorem, blade element theory, slipstream theory, and vortex theory, the tilt-rotor and thrust propeller of the distributed tilt-rotor solar UAV are designed and calculated; and through statistical algorithms and the original quasi-design method, the aerodynamic components such as wings, tail, and fuselage of the distributed tilt-rotor solar UAV are designed, and finally the three-dimensional appearance drawing is obtained through the three-dimensional drawing software CATIA.

[0306] Those skilled in the art should understand that the purpose of the above description of the embodiments of the present invention is only to exemplarily illustrate the beneficial effects of the embodiments of the present invention, and is not intended to limit the embodiments of the present invention to any given examples.

[0307] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A distributed tilt-rotor solar-powered UAV, characterized in that: include: The left fuselage and the right fuselage are connected by the 0# wing section; The left 1# wing section and the right 1# wing section are connected to the outer sides of the left fuselage and the right fuselage respectively; The tilting nacelle is arranged at the end of the 1# wing section away from the fuselage; The tilt rotor is arranged on the tilt nacelle.

2. A design method for a distributed tilt-rotor solar-powered UAV according to claim 1, characterized in that: include: Calculate solar radiation intensity; Based on the design input and the initial value of the flight weight, the total weight of the UAV is calculated by combining the energy balance and power balance, and the flight weight is optimized iteratively; The component parameters of the distributed tilt-rotor solar-powered UAV are designed.

3. The design method according to claim 2, wherein: Calculation of solar radiation intensity includes: Calculate the distance factor f between the Earth and the Sun: f=1+k1 cos(2πn day / 365) Where: k1 is the adjustment coefficient, n day is the day ordinal number; Calculate the solar radiation intensity E in the Earth's atmosphere SC : Where: C is the absorption of the inhomogeneous atmosphere, A is the average molar absorption coefficient of the atmosphere, and S0 is the solar constant.

4. The design method according to claim 2, wherein: Based on the design input and the initial value of the flight weight, the total weight of the UAV is calculated by combining the energy balance and power balance, and the flight weight is iteratively optimized, including: Calculate flight power for climb, day cruise, and night cruise; Determine the energy balance equation based on the energy consumption during the flight phase and the power consumption of the load during the day and at night; The total weight of the drone is determined based on energy balance, power balance, and difference calculation with the initial weight.

5. The design method according to claim 4, wherein: Calculation of flight power for climb, day cruise, and night cruise includes: Calculate the power P required for the climb phase climb : Where: F1 is the part of the lift borne by the wing during flight, is the climb rate, η pro is the propulsion system efficiency, P0 is the power consumed by the tiltrotor; Calculate the daytime cruising power P cruise_day : P cruise_day =k1mgV day / K / h pro +k2mgV day / K / h rotor Where: k1 and k2 are the proportions of thrust generated by the thrust propeller and the pull generated by the tilt rotor, respectively, η pro and η rotor for the efficiency of thrust propellers and tilt rotors; Calculate the night cruising power P cruise_night : P cruise-night =K0(k1mgV / K / h pro +k2mgV / K / h rotor ) Where: K0 is the ratio of the power consumed at night cruising altitude to that consumed at daytime cruising altitude.

6. The design method according to claim 4, wherein: According to the energy consumption of the flight phase and the power consumption of the load during the day and night, the energy balance relationship is determined as follows: The distributed tilt-rotor solar UAV starts to climb according to the sunrise time of the day. The climbing time of the UAV is calculated as t1 according to the climb rate performance, and the descent time t3 is calculated according to the descent rate. The remaining time is the daytime cruising time t2 and the nighttime cruising time t4. The energy consumption of the flight stage is: From day =P climb t1+P cruise_day t2+P slip t3 E night =P cruise_night t4 Then the power consumption of the load during the day and at night is calculated as: It is pld_day =P pld (t1+t2+t3) E pld_night =P pld t4 The energy consumed by the onboard equipment of the distributed tilt-rotor solar drone is E av_day and E av_night ; Then the energy balance equation is obtained: AND bat =And night +E pld_night +E av_night AND sc =And day +E pld_day +E av_day +E night +E pld_night +E av_night Among them, E bat and E sc They are the energy supply required by energy storage batteries and solar cells respectively.

7. The design method according to claim 4, wherein: Based on energy balance, power balance, and difference calculation with initial weight, the total weight of the drone is determined to include: The total weight of the drone is calculated by adding up all the parts of the drone and calculating the difference between the total weight and the initial weight until |(m total -m0) / m0|≤0.01, and iterate to form the final total weight of the UAV.

8. The design method according to claim 7, wherein: The total weight of the drone is calculated by adding up all the parts of the drone: m total =m mppt +m fuse +m wing +m sc +m wire +m rotor +m pro +m bat +m pld +m tilt Among them, m total is the total weight of the drone, m bat is the weight of the energy storage battery, m wing is the wing weight, m fuse is the fuselage weight, m rotor is the tiltrotor weight, m sc is the weight of the solar cell, m mppt is the weight of the power controller, m wire is the weight of the onboard cable, m pro The weight of the propulsion system.

9. The design method according to claim 8, wherein: The tilt rotor weight m rotor Including the weight of the rotor, hub, mounting parts and spinner cap, it is: Where: r , P r ,Ω r , R r , A2 and F r They are the solidity, rotor load, rotation speed, radius, adjustment coefficient and generated pulling force of the tiltrotor respectively; Solar cell weight m sc for: m sc =ρ sc S sc Where: sc is the solar cell array density, S sc The solar cell patch area is: S sc =E sc / (E sc0 or sc or c or mppt ) Where: E sc0 is the energy of photoelectric conversion per unit area of ​​solar cells, η sc is the photovoltaic conversion efficiency of the solar array, η c is the solar cell array loss efficiency, η mppt is the power controller efficiency; Power Controller Weight m mppt for: m mppt =1280S sc or sc or c / K mppt Where: S sc is the solar cell patch area, η sc is the photoelectric conversion efficiency, η c is the loss efficiency, K mppt is the power-to-weight ratio of the power controller.

10. The design method according to claim 2, wherein: The design of the parameters of the tilt-rotor of the distributed tilt-rotor solar UAV includes: Input the initial parameters of the tiltrotor, including design thrust T, rotation speed Ω, undercut R0, number of blades k, air density ρ, inflow velocity V, and rotor radius R; Divide the rotor blade into n blade elements, determine the airfoil distribution at each section, and input the optimal angle of attack and lift-drag coefficient at the airfoil section; The Lagrange multiplier K is solved by the following formula: Calculate the conversion angle and induced attack angle α i , and then solve the rotor blade chord length b at each characteristic section i : The corresponding induced velocity v is solved by momentum-blade element theory i and the incoming flow angle β * : Then solve the installation angle: θ=β * +a i +a best 。

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