Method for determining initial parameters of bird-like aircraft based on improved scale rate and model estimation

Abstract

The invention provides an improved scale rate and model estimation-based bird-like aircraft initial parameter determination method, which comprises the following steps of: firstly, calculating the statistical weight of a corrected bionic object bird, and secondly, establishing a corrected scale rate characteristic parameter; according to the method, the basic reasonable main parameters of the bird-imitating aircraft are rapidly determined in the initial design stage of the aircraft, a detailed design scheme can be rapidly formed according to less subsequent calculation simulation and tests, and the development process of the bird-imitating aircraft is greatly shortened. A comparison result shows that after initial parameters of the bird-imitating aircraft estimated by adopting a traditional scale rate and a model are designed, the bird-imitating aircraft with relatively good flight performance can be obtained through multi-round optimization, simulation and experiments; the initial parameters of the bird-imitating aircraft estimated by the method are closer to those of the bird-imitating aircraft with better flight performance, so that the method is proved to be capable of reducing the intermediate optimization process and quickly forming a detailed design scheme.

Description

Technical Field

[0001] The invention relates to the technical field of bird-mimicking aircraft design, and in particular to a method for determining initial parameters of a bird-mimicking aircraft based on improved scale rate and model estimation. Background Art

[0002] At present, due to the increasing demand for bird-like aircraft in the security and civil fields, a research boom has gradually been set off at home and abroad. According to statistics, there are currently more than 30 types of bird-like aircraft that can fly stably in the world.

[0003] At present, there are two main methods for estimating the initial basic parameters of bird-like aircraft used internationally. One is to estimate based on the statistical scaling rate of flying organisms; the other is to roughly estimate the range of variation of each parameter based on experience, take several discrete points within the range of variation of each parameter, and then evaluate and select a reasonable preliminary design plan from all possible permutations and combinations through the results of numerical simulation and wind tunnel experiments.

[0004] For the first method as shown in Table 1, the flying organism scale rate method (hereinafter referred to as the scale rate method)

[0005] Table 1 Scaling rate estimation formula

[0006] Characteristic parameters Scale rate Wingspan L(m) <![CDATA[1.17m 0.39 ]]> <![CDATA[Wing area S (m 2 )]]> <![CDATA[0.16m 0.72 ]]> Flight speed V(m / s) <![CDATA[10.147m 0.158 ]]> <![CDATA[Cruising power P 巡航 (W)]]> <![CDATA[17.63m 1.167 ]]> Flapping frequency f(Hz) <![CDATA[3.98m -0.27 ]]>

[0007] There are important defects:

[0008] (1) The sample accuracy is poor.

[0009] The statistical samples of this scale rate range from tens of grams to tens of kilograms, and from tens of centimeters to several meters in length. Obviously, the error is too large for a specific bionic object. For example, when designing an aircraft with pigeons as bionic objects, it is inappropriate to sample hummingbirds weighing tens of grams or even birds weighing more than ten kilograms. Only pigeon samples can be selected for statistics.

[0010] (2) The functions of birds and bionic aircraft are not completely consistent. The key parameter mass m in the formula in Table 1 is not suitable for direct estimation of bionic aircraft. On the one hand, the main purpose of bionic aircraft is to achieve the efficient movement function of birds. However, in addition to the weight of their skeletal and nervous systems, birds in nature also have the weight of non-movement functions such as warmth and courtship; on the other hand, bionic aircraft will include the weight of payloads (such as cameras, micro-ammunition, etc.) and additional information interaction equipment, and these functions are not possessed by birds in nature.

[0011] (3) The total area and total scale in the scale ratio do not reflect the different roles of the arm and hand in the bird's wing, which is a major flaw. Figure 1As shown. The proportion of the area, length and airfoil (cross-sectional shape) of the arm and wing in a bird's wing are important parameters that determine its flight ability, and cannot be described only by the area and length of the entire wing. It has been proven that the secondary flight feather area and airfoil of the arm wing mainly affect lift, while the primary flight feathers and airfoil of the hand wing mainly affect thrust, and also affect lift. Their functions are completely different.

[0012] (4) The scaling factor only estimates the flapping frequency, not the flapping amplitude. Just like human running, the frequency and stride amplitude are equally important to running ability. It has been proven that the flapping efficiency of birds is actually related to the product of frequency and amplitude, which actually represents the angular velocity of the flapping.

[0013] (5) In the scale rate, the cruise power estimation method cannot be directly applied to bionic aircraft. At present, mainstream bionic aircraft mainly use battery energy to drive motors (including controllers), which in turn drive multi-degree-of-freedom motion mechanisms (reducers are often used to convert the high-speed rotation of the motor into low-frequency flapping of the mechanism). This artificial electromechanical energy transmission mode is completely different from the natural animal mode of birds through eating-digestion-blood transmission-bone movement.

[0014] The second method requires too many candidate solutions to be evaluated, and the numerical simulation and wind tunnel test process is complex, long, and costly. At the same time, the evaluation results rely on experience, and there is a risk that the estimated parameter variation range may not include reasonable solution points. Summary of the invention

[0015] In order to solve the problem of long development cycle in the prior art when the scale and function of bird-like aircraft are diversified to meet different customer needs, the present invention proposes a method for determining the initial parameters of the bird-like aircraft based on improved scale rate and model estimation. The present invention can be used to quickly determine the basic and reasonable main parameters of the bird-like aircraft in the initial design stage of the aircraft, and a detailed design plan can be quickly formed based on less subsequent calculations, simulations and experiments, greatly shortening the development process of the bird-like aircraft.

[0016] The technical solution of the present invention is:

[0017] A method for determining initial parameters of a bird-mimicking flying vehicle based on improved scale rate and model estimation comprises the following steps:

[0018] Step 1: Calculate the modified statistical weight m1 of the bionic object bird; including the following steps:

[0019] Step 1.1: Select the population of bionic bird for data statistics;

[0020] Step 1.2: Analyze the functions of the bionic bird and the bionic aircraft, and use the formula based on the statistical results of step 1.1

[0021] η1*m1+η2*m1=η3*m2+η4*m2

[0022] Calculate the corrected statistical mass m1 of the bionic bird; where η1 is the statistically obtained weight ratio of the bionic bird's organs that are directly related to flight activities and have similar functions, η2 is the statistically obtained weight ratio of the bionic bird's organs that are related to flight activities but have independent functions; η3 is the weight ratio of the components of the proposed bionic aircraft that are directly related to flight activities and have similar functions, η4 is the weight ratio of the components of the proposed bionic aircraft that are related to flight but have independent functions; m2 is the estimated take-off weight of the bionic aircraft;

[0023] Step 2: Establish the corrected scale rate characteristic parameters as:

[0024] Wingspan L, wing area S, hand-wing length ratio β, hand-wing area ratio γ, flapping frequency f, flapping amplitude Angular velocity ω, flight speed V, wing cruise power P 翼巡航 ;

[0025] The wingspan L, wing area S, flight speed V and flapping frequency f are function expressions of the statistical weight of the bionic bird obtained in step 1; the proportion of hand-wing length β and the proportion of hand-wing area γ are statistical values ​​based on the bionic bird population;

[0026] Flutter amplitude According to the formula

[0027]

[0028] It is calculated that, where St is the Strouhal number;

[0029] The angular velocity ω is calculated according to the formula

[0030]

[0031] Calculated;

[0032] Wing cruise power P 翼巡航 According to the formula

[0033] P 翼巡航 =k×P 升力诱导

[0034] Calculated; the parameter k is an estimated parameter, representing the relationship between the induced drag caused by lift and other waste drag of the bionic aircraft; P 升力诱导 is the lift induced power, according to the formula

[0035]

[0036] Where α is a constant coefficient, given by It is calculated that ρ is the air density and g is the acceleration due to gravity.

[0037] Beneficial Effects

[0038] The present invention proposes a method for determining the initial parameters of a bird-mimicking aircraft based on improved scaling rate and model estimation, which can quickly determine the basic and reasonable main parameters of the bird-mimicking aircraft in the initial design stage of the aircraft, and can quickly form a detailed design plan based on less subsequent calculations, simulations and experiments, greatly shortening the development process of the bird-mimicking aircraft.

[0039] The embodiments show that after the initial parameters of the bird-mimicking aircraft are designed using the traditional scale rate and model estimation, multiple rounds of optimization, simulation and experimentation are required to achieve a bird-mimicking aircraft with better flight performance; while the initial parameters of the bird-mimicking aircraft estimated using the present invention are closer to the final bird-mimicking aircraft with better flight performance, thereby proving that the present invention can reduce the intermediate optimization process and can quickly form a detailed design plan.

[0040] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0042] Figure 1 : The proportion of the area and length of the arm and hand in the bird's wing, as well as the schematic diagram of the airfoil;

[0043] Figure 2 : The technical roadmap of the present invention. DETAILED DESCRIPTION

[0044] Aiming at the problems existing in the initial basic parameter estimation method of the existing bird-mimicking aircraft, the present invention proposes a method for determining the initial parameters of the bird-mimicking aircraft based on improved scale rate and model estimation. The method is further improved on the basis of the scale rate method of the flying organisms in front of the invention, and specifically comprises the following steps:

[0045] Step 1: Calculate the corrected statistical weight m1 of the bionic object bird:

[0046] Step 1.1: Select a population of bionic bird objects for data statistics to reduce the sample size in the scale rate and make the statistical sample more accurate.

[0047] For example, if people are designing a pigeon-like aircraft, they only need to select the pigeon population for statistics; if they are designing an eagle-like aircraft, they only need to select eagle data for statistics.

[0048] Step 1.2: Based on step 1.1, the functions of the bionic bird and the bionic aircraft are compared and analyzed one by one. In the bionic aircraft, the weight of non-motion functions not related to flight is subtracted, and the weight of the unique functions of the bionic aircraft is added, so that the equivalent bird statistical weight m1 is more accurate. According to the statistical results of step 1.1, using the formula

[0049] η1*m1+η2*m1=η3*m2+η4*m2

[0050] Calculate the corrected statistical mass m1 of the bionic object bird; wherein η1 is the statistically obtained weight ratio of the bionic object bird's organs that are directly related to flight activities and have similar functions, η2 is the statistically obtained weight ratio of the bionic object bird's organs that are related to flight activities but have independent functions; η3 is the weight ratio of the components of the proposed bionic aircraft that are directly related to flight activities and have similar functions, η4 is the weight ratio of the components of the proposed bionic aircraft that are related to flight but have independent functions; m2 is the estimated take-off weight of the bionic aircraft.

[0051] In the embodiment, the take-off weight m2 of the bionic aircraft is estimated according to the design requirements, and η1 and η2 are determined according to the statistical data of the bionic object bird population, and η3 and η4 are determined according to the empirical design data of typical bionic aircraft. The above formula is substituted into the above formula to solve the equivalent bird statistical weight m1.

[0052] Step 2: Modify and adjust the structural parameters L and S in the traditional scale rate characteristic parameters: modify the original characteristic parameters L and S to (L, β) and (S, γ); and add a new characteristic parameter flapping angular velocity ω.

[0053] Step 2.1: In the traditional scaling method, only the wingspan L and wing area S are considered. However, through the biological and kinematic analysis of birds, it is found that the arm wing and hand wing have a large difference in flight function. Therefore, the present invention adds two new characteristic parameters: the hand wing length ratio β and the hand wing area ratio γ:

[0054] β=L 手翼 / L

[0055] γ=S 手翼 / S

[0056] Where L 手翼 is the hand wing length, and the arm wing length L 臂翼 =(1-β)×L; S 手翼 The hand wing area = γ*S, and the arm wing area S 臂翼=(1-γ)*S. The arm-wing length ratio β reflects the functional difference between the arm-wing and hand-wing length ratios, and the arm-wing area ratio γ reflects the functional difference between the arm-wing and hand-wing area ratios. The specific statistical values ​​are determined based on the measurement data of the corresponding birds.

[0057] Step 2.2: In the traditional scaling method, the flapping frequency f is taken into account. In addition to the flapping frequency f, the flapping amplitude It is also an important factor that affects the flight of birds. In the design process, especially the design of the mechanism, the two parameters of flapping frequency and flapping amplitude have an impact on the mechanism design. The original scale rate can only estimate the flapping frequency data. Therefore, the present invention adds the parameter of flapping amplitude to the scale rate, which can be used as a reference for the value in the design process.

[0058] In addition, the angular velocity is obtained by multiplying the flapping amplitude by the frequency. The angular velocity can more comprehensively and accurately describe the motion law of the bird-like flying vehicle. Therefore, a new characteristic parameter, the flapping angular velocity ω, is added:

[0059]

[0060] The angular velocity ω is used to balance the reflection f and Effect on flapping efficiency.

[0061] Considering the flapping amplitude of birds The problem that it is difficult to obtain by actual observation is solved. Based on the quasi-steady assumption when the airflow passes through the aircraft, the present invention proposes to establish f and The flapping amplitude is calculated by the approximate relationship method

[0062]

[0063] Among them, St is the Strouhal number, generally ranging from 0.3 to 0.4, V is the flight speed, L is the wingspan, and f is the flapping frequency, which has been proven to be reasonable by the practice of bionic aircraft.

[0064] Step 3: Change the cruise power P in the traditional scale rate characteristic parameter 巡航 Corrected to wing cruise power P 翼巡航 :

[0065] Since the cruise power of the wing has a crucial influence on the weight of the required battery and the total weight of the bionic aircraft, the cruise power P in the traditional scale rate characteristic parameter is 巡航 The estimation formula is too simple, so the present invention expands and modifies it:

[0066] P 翼巡航 =k×P 升力诱导 , k∈1.2~1.3

[0067] The parameter k is an estimated parameter, which represents the relationship between the induced drag caused by lift and other drags (such as friction drag and shape drag) of the bionic aircraft, and its empirical value is 1.2 to 1.3; P 升力诱导 is the lift induced power, calculated as follows:

[0068] Estimation based on potential flow theory

[0069]

[0070] α is a constant coefficient, which can be obtained from It is calculated that ρ is the air density and g is the acceleration due to gravity.

[0071] The final estimated scale rate characteristic parameter is:

[0072]

[0073] Based on the characteristic parameters estimated above, a detailed design plan can be quickly formed in the initial design stage of the aircraft, greatly shortening the development process of the bird-like aircraft.

[0074] Embodiments of the present invention are described in detail below. The embodiments are exemplary and intended to be used to explain the present invention, but should not be construed as limiting the present invention.

[0075] Example 1: Estimation of basic parameters of the “Carrier Pigeon” bionic aircraft solution:

[0076] Step 1: It is necessary to design a pigeon-like aircraft with a take-off weight of 260g; first, statistics are conducted based on the pigeon population, and a biological analysis is performed on the pigeons to determine the weight proportion of each functional organ directly related to flight activities, and the weight proportion of components of the bionic aircraft that are directly related to flight activities and have similar functions is determined based on the empirical design data of typical bionic aircraft, and η1=45.92%, η2=24.1%, η3=79.3%, η4=10% are obtained, and the equivalent bird weight m1=331g=0.331kg is finally determined by substituting into the formula η1*m1+η2*m1=η3*m2+η4*m2.

[0077] Step 2: Calculate the proportion of hand wing length β and hand wing area γ. According to biometric data, determine β = 35% and γ = 65%.

[0078] The scale rate estimation formula is obtained by taking the biological data of pigeons as samples:

[0079] Characteristic parameters Scale rate Wingspan L(m) <![CDATA[0.805m 0.1486 ]]> <![CDATA[Wing area S (m 2 )]]> <![CDATA[0.5874m 1.924 ]]> Flight speed V(m / s) <![CDATA[10.148m 0.158 ]]> Flapping frequency f(Hz) <![CDATA[7.7545m -0.27 ]]> Wing length ratio β 35％ Wing area ratio γ 65％

[0080] Here m is the equivalent bird weight m1.

[0081] Flutter amplitude Where St is 0.35, and the other parameters in the formula can be calculated based on the equivalent bird mass m1. Substituting them into the equation, we get

[0082]

[0083] Substituting the flapping amplitude and frequency into the angular velocity:

[0084] ω=10.452*0.9954*2=20.797rad / s

[0085] According to the above results, and calculated that α in the power calculation formula is 17063.098, the power calculation formula can be obtained

[0086] P 升力诱导 =17063.098*(0.26) 2 / (57.031*0.683*0.683*10)=4.374W

[0087] P 翼巡航 =k×P 升力诱导 =4.374*1.2=5.249W

[0088] In this embodiment, the estimation results using the traditional scaling method and the method of the present invention are shown in Table 2:

[0089] Table 2 Comparison of the effects of the present invention using the "pigeon" bionic aircraft as an example

[0090]

[0091] It can be seen that compared with the scale rate method, the present invention gives the length and area of ​​the arm and hand wings, the flapping amplitude and the flapping angular velocity. The addition of these parameters is useful for better describing the overall scheme; compared with the parameter values ​​given by the present invention, except for the frequency, the relative errors of other parameters of the scale rate method are between 1.70% and 28.8%, while the relative difference between the frequency and the final object is 42.7%. It shows that the initial parameters of the bird-like aircraft estimated by the present invention are closer to the bird-like aircraft with better flight performance in the end, proving that the present invention can reduce the intermediate optimization process and quickly form a detailed design scheme.

[0092] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and intent of the present invention.

Claims

1. A method for determining initial parameters of a bird-mimicking aircraft based on improved scale rate and model estimation, characterized in that: The following steps are involved: Step 1: Calculate the corrected statistical weight m1 of the bionic object bird; The following steps are involved: Step 1.1: Select the population of bionic bird for data statistics; Step 1.2: Analyze the functions of the bionic bird and the bionic aircraft, and use the formula based on the statistical results of step 1.1 η1*m1+η2*m1=η3*m2+η4*m2 Calculate the corrected statistical mass m1 of the bionic bird; where η1 is the statistically obtained weight ratio of the bionic bird's organs that are directly related to flight activities and have similar functions, η2 is the statistically obtained weight ratio of the bionic bird's organs that are related to flight activities but have independent functions; η3 is the weight ratio of the components of the proposed bionic aircraft that are directly related to flight activities and have similar functions, η4 is the weight ratio of the components of the proposed bionic aircraft that are related to flight but have independent functions; m2 is the estimated take-off weight of the bionic aircraft; Step 2: Establish the corrected scale rate characteristic parameters as: Wingspan L, wing area S, hand-wing length ratio β, hand-wing area ratio γ, flapping frequency f, flapping amplitude Angular velocity ω, flight speed V, wing cruise power P 翼巡航 ; The wingspan L, wing area S, flight speed V and flapping frequency f are the functional expressions of the statistical weight of the bionic bird obtained in step 1; the proportion of wing length β and the proportion of wing area γ are the statistical values ​​of the bionic bird population; the flapping amplitude According to the formula It is calculated that, where St is the Strouhal number; The angular velocity ω is calculated according to the formula Calculated; Wing cruise power P 翼巡航 According to the formula P 翼巡航 =k×P 升力诱导 Calculated; the parameter k is an estimated parameter, representing the relationship between the induced drag caused by lift and other waste drag of the bionic aircraft; P 升力诱导 is the lift induced power, according to the formula Where α is a constant coefficient, given by It is calculated that ρ is the air density and g is the acceleration due to gravity.

2. The method for determining initial parameters of a bird-mimicking aircraft based on improved scale rate and model estimation according to claim 1, characterized in that: The Strouhal number St is between 0.3 and 0.

4.

3. The method for determining initial parameters of a bird-mimicking aircraft based on improved scaling and model estimation according to claim 1, characterized in that: The estimated parameter k is between 1.2 and 1.

3.

4. The method for determining initial parameters of a bird-mimicking aircraft based on improved scaling and model estimation according to claim 1, characterized in that: For pigeon-like bird-like aircraft, the wingspan L scale rate is 0.805m 0.1486 The wing area S scale rate is 0.5874m 1.924 , the flight speed V scale rate is 10.148m 0.158 The flutter frequency f is 7.7545m -0.27 .

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