Initial parameter determination method of bird-like flying vehicle based on improved scaling and model estimation

Abstract

The present invention proposes a method for determining the initial parameters of a bird-like aircraft based on improved scale factor and model estimation. The method first calculates the corrected statistical weight of the bionic bird, and then establishes the corrected scale factor characteristic parameters. The present invention allows rapid determination of the basic and reasonable key parameters of the bird-like aircraft during the initial design phase. Subsequently, a detailed design plan can be quickly developed with minimal computational simulation and testing, significantly shortening the development process of the bird-like aircraft. Comparative results show that even after designing the initial parameters of a bird-like aircraft using traditional scale factor and model estimation, multiple rounds of optimization, simulation, and testing are required to achieve a bird-like aircraft with good flight performance. However, the initial parameters estimated using the present invention are closer to the final bird-like aircraft with good flight performance. This demonstrates that the present invention can reduce intermediate optimization steps and rapidly develop a detailed design plan.

Description

Technical Field

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

[0002] Currently, due to the increasing demand for bird-like aircraft in security and civilian fields, a research boom has gradually emerged both domestically and internationally. According to statistics, there are currently more than 30 types of bird-like aircraft that can fly stably internationally.

[0003] Currently, there are two main methods used internationally to estimate the initial basic parameters of bird-like aircraft. One is based on the statistical scaling of flying organisms; the other is to roughly estimate the range of variation of each parameter based on experience. Each parameter is selected at several discrete points within its range, and then a reasonable preliminary design scheme is selected from all possible permutations and combinations through numerical simulation and wind tunnel testing.

[0004] For the first method 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 sample size for this scale rate ranges from tens of grams to tens of kilograms, and from tens of centimeters to several meters in length. This error is clearly too large for specific biomimetic objects. For example, when designing an aircraft based on pigeons, it would be inappropriate to sample a population that includes hummingbirds weighing tens of grams or even birds weighing more than ten kilograms. Only pigeons can be used for statistical analysis.

[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 movement systems such as bones and nerves, 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 natural birds.

[0011] (3) The total area and total scale in the scale ratio do not reflect the different roles of the arm and hand in bird wings, which is a major flaw, such as Figure 1As shown in Figure 2, the proportion of the wing's wing area, length, and airfoil (cross-sectional shape) are crucial parameters determining a bird's flight performance and cannot be described solely by the area and length of the entire wing. It has been shown that the area and airfoil shape of the wing's secondary feathers primarily influence lift, while the airfoil shape of the wing's primary feathers primarily contributes to thrust, while also influencing lift. Their functions are fundamentally different.

[0012] (4) The scaling factor estimates only the flapping frequency, not the flapping amplitude. Just as in human running, both the frequency and stride length are equally important to running performance. It has been shown that a bird's flapping efficiency is actually related to the product of frequency and amplitude, which represents the angular velocity of the flapping.

[0013] (5) In the scale factor, the cruise power estimation method cannot be directly applied to bionic aircraft. Currently, mainstream bionic aircraft mainly use battery energy to drive motors (including controllers), which in turn drive multi-degree-of-freedom motion mechanisms (often using a reducer 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, which is through eating-digestion-blood transmission-skeletal movement.

[0014] The second method requires evaluating too many candidate solutions, and the numerical simulation and wind tunnel testing 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 existing technology 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 bird-like aircraft based on improved scaling 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. Based on less subsequent calculations, simulations and experiments, a detailed design plan can be quickly formed, 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 aircraft 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 determined weight percentage of the bionic bird's organs that are directly related to flight activities and have similar functions; η2 is the statistically determined weight percentage of the bionic bird's organs that are related to flight activities but have independent functions; η3 is the weight percentage of the proposed bionic aircraft's components that are directly related to flight activities and have similar functions; η4 is the weight percentage of the proposed bionic aircraft's components that are related to flight but have independent functions; and m2 is the estimated takeoff weight of the bionic aircraft.

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

[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] Wherein, 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 as follows, 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 generated 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, Calculated, 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 and model estimation. The method can quickly determine the basic and reasonable main parameters of the bird-mimicking aircraft in the initial design stage of the aircraft. Based on less subsequent calculations, simulations and experiments, a detailed design plan can be quickly formed, greatly shortening the development process of the bird-mimicking aircraft.

[0039] The examples show that after the initial parameters of the bird-like aircraft are estimated using traditional scale rates and models for design, multiple rounds of optimization, simulation, and experiments are required to achieve a bird-like aircraft with better flight performance; however, the initial parameters of the bird-like aircraft estimated using the present invention are closer to the final bird-like 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 set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by 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 readily understood from the following description of the embodiments with reference to the accompanying drawings, in which:

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

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

[0044] The present invention addresses the problems existing in the existing methods for estimating the initial basic parameters of bird-like aircraft and proposes a method for determining the initial basic parameters of a bird-like aircraft based on improved scale rate and model estimation. The method is further improved on the scale rate method of flying organisms and specifically includes 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 species 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 the eagle data for statistics.

[0048] Step 1.2: Based on step 1.1, conduct a one-to-one comparison analysis of the functions of the bionic bird and the bionic aircraft. In the bionic aircraft, subtract the weight of non-motion functions not related to flight and add the weight of the bionic aircraft's unique functions to make the equivalent bird statistical weight m1 more accurate. Based on the statistical results of step 1.1, use the formula

[0049] η1*m1+η2*m1=η3*m2+η4*m2

[0050] Calculate the corrected statistical mass m1 of the bionic object bird; where 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 proposed bionic aircraft's components that are directly related to flight activities and have similar functions, η4 is the weight ratio of the proposed bionic aircraft's components 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 traditional scaling methods, only wingspan L and wing area S are considered. However, biological and kinematic analysis of birds reveals that arm wings and hand wings contribute significantly to flight function. Therefore, this invention adds two new characteristic parameters: hand wing length ratio β and hand wing area ratio γ:

[0054] β=L 手翼 / L

[0055] γ=S 手翼 / S

[0056] Among them L 手翼 is the hand wing length, and the arm wing length L 臂翼 =(1-β)×L; S 手翼 The arm wing area = γ*S, and the arm wing area S 臂翼=(1-γ)*S. The wing length ratio β reflects the functional difference between the arm-wing and hand-wing length ratios, and the 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 considered. In addition to the flapping frequency f, the flapping amplitude It is also an important factor that affects bird flight. In the design process, especially the design of the mechanism, both the flapping frequency and the flapping amplitude parameters have an impact on the mechanism design. The original scale rate can only estimate the flapping frequency data. Therefore, the present invention adds the flapping amplitude parameter to the scale rate, which can be used as a reference for the value during 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, 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 of being difficult to obtain by actual observation is solved. Based on the quasi-steady assumption of airflow passing 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 factor 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, representing the relationship between the induced drag caused by lift and other drags (such as friction drag and form 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 Calculated, ρ is the air density and g is the acceleration due to gravity.

[0071] The final estimated scale rate characteristic parameters are:

[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] The following describes in detail embodiments of the present invention. The embodiments are exemplary and intended to explain the present invention, but are not to be construed as limiting the present invention.

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

[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 conducted on the pigeons to determine the weight proportion of each functional organ directly related to flight activities, and based on the empirical design data of typical bionic aircraft, the weight proportion of components of the bionic aircraft that are directly related to flight activities and have similar functions is determined, and η1=45.92%, η2=24.1%, η3=79.3%, η4=10% are obtained. Substituting into the formula η1*m1+η2*m1=η3*m2+η4*m2, the equivalent bird weight m1 is finally determined to be 331g=0.331kg.

[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 obtained by taking the biological data of pigeons as samples is:

[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] Where m is the equivalent bird weight m1.

[0081] Flutter amplitude Where St is taken as 0.35, the other parameters in the formula can be calculated based on the equivalent bird mass m1, and we can get

[0082]

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

[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 "Carrier Pigeon" bionic aircraft as an example

[0090]

[0091] As can be seen, compared to the scale-rate method, the present invention provides the length and area of ​​the arm and hand wings, the flapping amplitude, and the flapping angular velocity. The inclusion of these parameters helps better describe the overall design. Compared to the parameter values ​​given by the present invention, the relative errors of the scale-rate method's other parameters, except for frequency, range from 1.70% to 28.8%, while the frequency differs from the final actual design by 42.7%. This indicates that the initial parameters of the bird-like aircraft estimated using the present invention are closer to the final bird-like aircraft with good flight performance, demonstrating that the present invention can reduce intermediate optimization steps and quickly form a detailed design plan.

[0092] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative 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 purpose of the present invention.

Claims

1. A method for determining initial parameters of a bird-mimicking aircraft based on improved scaling and model estimation, characterized by: 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 determined weight percentage of the bionic bird's organs that are directly related to flight activities and have similar functions; η2 is the statistically determined weight percentage of the bionic bird's organs that are related to flight activities but have independent functions; η3 is the weight percentage of the proposed bionic aircraft's components that are directly related to flight activities and have similar functions; η4 is the weight percentage of the proposed bionic aircraft's components that are related to flight but have independent functions; and m2 is the estimated takeoff weight of the bionic aircraft. Step 2: Establish the corrected scale rate characteristic parameters as follows: 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 ; Wherein wingspan L, wing area S, flight speed V and flapping frequency f are the 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 the statistical values ​​of the bionic bird population; the flapping amplitude According to the formula It is calculated as follows, 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 generated 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, Calculated, 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 scaling 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 1.2 to 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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