Characterization Method of Aircraft Stall and Deviation Characteristics

Abstract

The present invention relates to a method for characterizing aircraft stall and deviation characteristics, including a stall dimension characterization method and a deviation dimension characterization method; the stall dimension characterization method includes the establishment of a stall function model and a stall warning; the deviation dimension characterization method includes using the deviation angle of attack, deviation characteristics, and spin sensitivity obtained by static criteria to compare with similar models as evaluation indicators to evaluate the aircraft deviation characteristics and spin sensitivity, and using the working efficiency and reliability of the control law as evaluation indicators. The present invention covers multiple levels such as aerodynamic models, stall warnings, characteristic predictions, and control law design, and provides a good verification method for evaluating the aerodynamic characteristics and safety of high angles of attack during the aircraft design stage; it has rigorous logic and solution framework, low computational complexity, and can be quickly solved with low machine time on general performance computing devices.

Description

Technical Field

[0001] The invention relates to the field of aviation high angle of attack aerodynamics, and in particular to a method for characterizing stall and deviation characteristics of an aircraft. Background Art

[0002] When an aircraft flies in a high angle of attack area, complex and dangerous situations such as deviation, stall, and spin may occur. When designing an aircraft, designers need to fully evaluate the aircraft's aerodynamic characteristics at high angles of attack. In order to predict and evaluate a certain high angle of attack flight characteristic of an aircraft, it is often necessary to obtain a single aerodynamic characteristic under specific conditions based on wind tunnel test data. This verification method makes it impossible to fully evaluate the aerodynamic characteristics of the aircraft, and it is impossible to obtain the high angle of attack aerodynamic performance of the aircraft model from a global perspective. Especially now that the military and civil aviation are paying more and more attention to aircraft stall, it is urgent to develop a comprehensive evaluation method for characterizing the deviation characteristics of aircraft stalls at high angles of attack that is both economical and practical. Summary of the invention

[0003] In view of the deficiencies in the above-mentioned prior art, the present invention provides a method for characterizing aircraft stall and deviation characteristics, which has rigorous logic and solution framework, has low computational complexity, and can be quickly solved at low machine time on a general performance computing device.

[0004] The technical solution adopted by the present invention is:

[0005] A method for characterizing aircraft stall and deviation characteristics, characterized by comprising a stall dimension characterization method and a deviation dimension characterization method;

[0006] The stall dimension characterization method includes the establishment of the stall function model and the determination of the corresponding parameters;

[0007] The establishment of the stall function model includes:

[0008] Modeling of nonlinear aerodynamic forces at high angles of attack of aircraft, with the prediction accuracy (error) and logical accuracy of the model evaluated;

[0009] The aircraft high angle of attack nonlinear aerodynamic modeling is a mathematical model established based on flight performance analysis, control law design and flight simulation research;

[0010] The deviation dimension characterization method includes using the deviation angle of attack, deviation characteristics, and spin sensitivity obtained by static criteria to compare with similar models to evaluate the aircraft's deviation characteristics and spin sensitivity, and using the working efficiency and reliability of the anti-deviation control law as evaluation indicators to assess whether the aircraft can automatically resist deviation and whether it can achieve worry-free control.

[0011] Preferably, the flight performance analysis is performed by analyzing the performance indicators of the aircraft under different flight conditions, such as lift, drag, pitch moment, rolling moment, yaw moment, etc.; and the aerodynamic characteristics of the aircraft under different angles of attack, speeds, altitudes, etc., such as lift coefficient, drag coefficient, pitch moment coefficient, rolling moment coefficient, yaw moment coefficient, etc.; determining the structure of the mathematical model, such as state variables, input variables, output variables, etc.; according to the flight performance indicators and aerodynamic characteristics, establishing a nonlinear aerodynamic model of the aircraft at a large angle of attack, and determining the model parameters.

[0012] Control law design: determine the control objectives of the control law based on flight performance indicators and aerodynamic characteristics, such as maintaining stable flight of the aircraft and avoiding stall deviation; select appropriate control methods based on the control objectives, such as PID control, adaptive control, robust control, etc.; design the aircraft's control law based on the control method and aerodynamic model, and determine the control law parameters;

[0013] Flight simulation: Establish a flight simulation model that includes aircraft dynamics model, aerodynamic model and control law model; conduct simulation tests to verify the effectiveness of the aerodynamic model and control law, and evaluate the performance of the aircraft under different flight conditions; optimize the aerodynamic model and control law parameters based on the simulation test results to improve the accuracy of the model and the performance of the control law;

[0014] Verify the model accuracy, compare the established mathematical model with the flight test data, and evaluate the model's prediction accuracy; analyze the model's prediction error and find out the cause of the error; optimize the model parameters based on the error analysis results to improve the model's accuracy.

[0015] The model should be able to accurately and completely describe the nonlinear aerodynamics of the aircraft in the high angle of attack region, and the aerodynamic parameters in the model should be obtained after rigorous identification;

[0016] Preferably, the stall function model is a dynamic derivative model;

[0017] The dynamic derivative model predicts the force conditions of the aircraft under different flight conditions by establishing the functional relationship between the aerodynamic coefficients and the aircraft state variables (angle of attack, sideslip angle, angular velocity, rudder deflection angle, etc.);

[0018] The process of establishing the dynamic derivative model includes: establishing a high angle of attack aerodynamic database based on wind tunnel test data, and forming a dynamic derivative model from multiple dynamic derivative coefficients in the database; using wind tunnel test data and parameter identification methods (such as least squares method, gradient descent method, Newton-Raphson method, etc.) to calculate the estimated values ​​of the model parameters; using flight test data or scaled model flight test data to accurately identify the parameters of the estimated values ​​and verify the accuracy of the dynamic derivative model;

[0019] The dynamic derivative model decomposes the aerodynamic force into three parts: static aerodynamic force, oscillating aerodynamic force and rotating aerodynamic force. The dynamic derivative model can be expressed as follows:

[0020]

[0021] in, , ; represents the axial force coefficient of the body shaft system, represents the lateral force coefficient of the body axis system, represents the normal force coefficient of the body axis system, represents the rolling moment coefficient, represents the pitching moment coefficient, Represents the yaw moment coefficient. represents the angle of attack, represents the sideslip angle, , , Respectively represent the aileron, pitch, and yaw rudder deflection angles, the unit is degree;

[0022] In the above formula, It represents the static aerodynamic data item in the high angle of attack wind tunnel test, including the static aerodynamic item when the rudder deflection is zero and the static aerodynamic increment item caused by the rudder surface deflection;

[0023] The aerodynamic terms caused by the forced oscillatory motion in the high angle of attack wind tunnel test;

[0024] It is the aerodynamic term caused by rotational motion in high angle of attack wind tunnel test.

[0025] In order to ensure that the model has good prediction accuracy, whether it is mathematical modeling, intelligent learning modeling, or a comprehensive modeling method combining multiple means, the error between the predicted high angle of attack aerodynamic characteristics and the flight test should be smaller than the mathematical aerodynamic model commonly used in current engineering practice (such as the dynamic derivative model). The following measures are taken to improve the accuracy and correct the error:

[0026] For mathematical modeling, ensure that the aerodynamic model accurately reflects the aerodynamic characteristics of the aircraft, and verify and correct it through detailed wind tunnel test data and flight test data; in the modeling process, make reasonable assumptions about the aerodynamic characteristics to avoid prediction errors caused by overly simplified assumptions; optimize model parameters to make the prediction results closer to the actual situation.

[0027] For intelligent learning modeling, a large amount of flight test data and wind tunnel test data are collected to provide sufficient learning samples for algorithms such as neural networks and support vector machines. The data are trained using the algorithm, and the validation data set is used to evaluate the prediction accuracy of the model. Based on the prediction error, the model parameters are adjusted, the model structure is optimized, and the prediction accuracy is improved.

[0028] For the comprehensive modeling method that combines multiple means, we can combine the advantages of mathematical modeling and intelligent learning modeling to form a complementary relationship and improve the prediction accuracy of the model; in the modeling process, use the cross-validation method to evaluate the prediction error of the model and continuously optimize the model; or combine the experience of authoritative experts in the field to evaluate and adjust the model to improve the prediction accuracy of the model.

[0029] Preferably, when performing error analysis and verification optimization on the model, first find out the cause of the error; such as model parameters, algorithm selection, data quality, etc.; then compare the model prediction results with the flight test data to evaluate the prediction accuracy of the model; finally, based on the verification results, continuously optimize the model to improve the prediction accuracy.

[0030] The present invention achieves rapid solution with low machine time on a computing device of general performance by the following measures:

[0031] In the selection of model types, priority is given to simple mathematical models, such as dynamic derivative models, to avoid overly complex model structures to reduce computational complexity; or the advantages of mathematical modeling and intelligent learning modeling are combined, such as using mathematical models to establish a basic framework, and then using intelligent learning models for parameter optimization, which can reduce the amount of calculation while ensuring accuracy; and the model is decomposed into multiple modules, such as aerodynamic models, dynamic models, control law models, etc. The modules are independent of each other to facilitate debugging and optimization.

[0032] In terms of algorithm selection, efficient numerical algorithms are selected to solve the model, such as the Runge-Kutta method, Newton iteration method, etc., to improve computing efficiency; and parallel computing technology is used to decompose the model solving process into multiple subtasks, which are calculated in parallel on multiple processors to further shorten the calculation time.

[0033] In terms of logical framework, a clear logical framework is established to clarify the input, output and calculation process of the model, avoid redundant calculations, and improve solution efficiency; the characterization method is hierarchical and progressive, the logical relationship between levels is clear, the characteristic characterization means are direct and effective, without too many logical transitions; there is no complex iterative logic, so the number of iterations can be reduced, and early termination conditions are used to reduce unnecessary iterations.

[0034] Preferably, the effective time of the stall warning reminder given to the pilot by the aircraft or the airborne equipment determines the warning timing;

[0035] The deviation dimension is based on the deviation characteristics and spin sensitivity of the aircraft's static stability, and whether it has the ability to prevent deviation without relying on human control;

[0036] The deviation angle of attack, deviation characteristics and spin sensitivity of the aircraft in a specific state are predicted by deviation criteria and compared with similar models.

[0037] Preferably, the prediction accuracy refers to comparing the established aerodynamic model with the flight test data to calculate the prediction error;

[0038] The prediction accuracy score is based on the relative error percentage, with a full score of 100 points, and the average value of all angle of attack states is taken;

[0039] If the error between the high angle of attack aerodynamic characteristics predicted by the model and the flight test data is less than 2%, the score will be 100 points;

[0040] If the error is between 2% and 8%, the score is 80 points;

[0041] If the error is between 8% and 15%, the score is 60 points;

[0042] If the error exceeds 15%, no points will be awarded.

[0043] Preferably, determining the solution framework of the dynamic derivative model includes the following steps:

[0044] Check the model structure. All variables in the model need to be clearly defined, including physical meaning, units, and value ranges. All formulas in the model need to have a clear derivation process, including the source of the formula, assumptions, and derivation steps. If the model contains multiple equations, check whether the system of equations is closed, that is, whether all unknown quantities can be solved through the system of equations.

[0045] Check the model logic and make sure that the output of the model has clear physical meaning and is consistent with the actual situation. The model should consider boundary conditions, such as angle of attack, speed, altitude, etc., and ensure that the model is still valid under these boundary conditions. If the model requires numerical calculation, check the convergence of the model to ensure that the calculation results are stable and reliable.

[0046] Check model validation, verify the logic and accuracy of the model through theoretical analysis, compare with other theoretical models, or perform limit case analysis; verify the prediction accuracy of the model through test data, and compare the model prediction results with flight test data;

[0047] Check the readability of the model. The model documentation should be clear and easy to understand, including the model structure, formula derivation, parameter description, and usage methods. If the model is implemented using a computer program, the code should be standardized and annotated to facilitate others' understanding and use.

[0048] Logical accuracy is scored on a 100-point scale;

[0049] If the solution process is completely clear, logical, and unambiguous, the score will be 100 points;

[0050] If the solution process is relatively clear, but there are a few unclear points, the score will be recorded as 80 points;

[0051] If the solution process is partially unclear or has a few logical loopholes, but the solution is within the allowable range, the score will be recorded as 60 points;

[0052] If the solution process is obviously unclear or has a large number of logical loopholes, it will be scored as 0 points.

[0053] Natural warnings need to assess the pilot's perception of fuselage vibration under normal physiological and psychological conditions, so as to check whether the fuselage vibration starts when the angle of attack reaches 60% of the stall angle of attack and increases with the increase of the angle of attack; the assessment method of the perception degree includes:

[0054] Subjective assessment: ask pilots about their perception of fuselage vibration at different angles of attack, such as the intensity, frequency, and location of the vibration, to determine their specific feelings about the fuselage vibration; for example, whether the vibration is obvious and whether it can attract attention.

[0055] Objectively evaluate and measure the pilot's physiological indicators, such as heart rate, blood pressure, and skin conductance, analyze the impact of jitter on the pilot's physiological state, and observe the pilot's behavioral reactions when jitter occurs; for example, whether the control stick shakes, whether there is panic, etc.

[0056] Simulation test, simulating the vibration of the fuselage at different angles of attack in a flight simulator, asking pilots to evaluate and record their perception, or using a vibration platform to simulate the vibration of the fuselage, asking pilots to evaluate and record their perception;

[0057] Expert evaluation: invite flight training experts or psychology experts to evaluate the pilot's perception level based on their experience and expertise.

[0058] Since the "degree of perception of body vibration" is a subjective feeling, there is no unified standard for determination. Therefore, we can refer to some relevant research and experience to formulate some preliminary determination standards:

[0059] The pilot can feel the vibration, but it will not affect the operation. It is a mild vibration, which means the pilot can feel it.

[0060] If the pilot can feel the vibration and needs to concentrate to keep the operation stable, it means that the pilot can clearly perceive it.

[0061] If the pilot cannot confirm the vibration he feels and needs to concentrate to verify his judgment, the vibration is not obvious.

[0062] The alarm timing and alarm effectiveness scores are in percentage form, with a full score of 100 points;

[0063] If the fuselage buffeting starts when the angle of attack reaches 60% of the stall angle of attack and the pilot can clearly feel it, the score is recorded as 100 points;

[0064] If the fuselage buffeting starts later, but before the angle of attack reaches 70% of the stalling angle of attack, and the pilot is able to perceive it, the score is recorded as 80 points;

[0065] If the fuselage buffeting begins before the stall angle of attack but later than 70% of the stall angle of attack, or earlier than 60% of the stall angle of attack,

[0066] Or if the jitter can occur within the specified angle of attack range but the jitter is not obvious, the score is recorded as 60 points;

[0067] If the fuselage shakes close to the stall angle of attack, or there is no shaking, the score is recorded as 0 points;

[0068] Manual stall warning is to install electronic or mechanical airborne equipment to provide the pilot with sufficient stall warning information by voice, light, buzzer, joystick or seat shaking when the aircraft is about to enter or is entering a stall state;

[0069] The effectiveness of the warning involves testing the manual warning system in a complex driving environment, evaluating the complexity of the equipment and its potential interference with the pilot's operation to verify the clarity and effectiveness of its information; it is necessary to evaluate the complexity of the equipment's operating procedures, interface design, number of functions, etc.; it is necessary to evaluate the interference that the equipment may cause to the pilot's operation, such as operating difficulty, information overload, and misoperation; it is necessary to evaluate whether the information provided by the equipment is clear and easy to understand, such as warning information, operating prompts, etc.; it is necessary to evaluate whether the information provided by the equipment is timely and effective, such as the timing of warnings, corrective measures, etc.

[0070] Take, for example, a flight simulator in which a pilot is flying in low-altitude complex weather conditions and the aircraft is about to enter a stall state. Assume that the aircraft is equipped with two stall warning systems, one is a simple sound warning, and the other is a complex visual warning that includes multiple information and indicator lights.

[0071] Complex visual warning systems may distract the pilot's attention and cause operational errors; simple sound warning systems provide relatively simple information but are easy to understand; complex visual warning systems provide relatively rich information but require interpretation by the pilot; simple sound warning systems may issue a warning in time before the aircraft enters a stall state; complex visual warning systems require interpretation by the pilot, which may delay the warning.

[0072] The pilots were asked to operate the two stall warning systems respectively, and their operation time, operation error rate, psychological stress and physiological indicators were recorded; the pilots' operating experience of the two stall warning systems was investigated, including equipment complexity, potential interference, information clarity and effectiveness.

[0073] The effectiveness of the alert is scored in the form of clarity and simplicity of the alert, with a full score of 100. Clear and simple alerts are:

[0074] The warning should be issued in time when the aircraft is about to enter or is entering a stall state so that the pilot has enough time to take measures; the warning should be able to predict the trend of the aircraft entering a stall state and provide early warning information.

[0075] Warning information should be clear and easy to understand, avoiding the use of professional terms or vague expressions; warning information should clearly indicate the status of the aircraft, such as "stall warning" or "deviation warning"; warning information should be intuitive and easy to understand, such as using sound, light, images, etc.

[0076] The warning method should be consistent with the warning method of other aircraft systems to facilitate quick identification by pilots; the warning method should be diversified, such as sound, light, vibration, etc., to improve the effectiveness of the warning; pilots should be able to choose different warning methods according to their own needs.

[0077] The design of the warning interface should be simple and clear to facilitate pilots to quickly obtain information; warning information should be effectively distinguished from other information to avoid information overload; warning operations should be simple and convenient to facilitate pilots to operate quickly in emergency situations.

[0078] If the warning method is clear and effective and does not increase the pilot's operating burden, the score will be 100 points;

[0079] If the warning mode is relatively clear but there is a small amount of interference, the score is recorded as 80 points;

[0080] If the warning method is complex, causing difficulty or confusion for the pilot, the score will be recorded as 60 points;

[0081] If the warning method cannot allow the pilot to obtain clear warning information, no points will be awarded.

[0082] Preferably, the deviation angle of attack is comprehensively determined according to the critical angle of attack, the neutral angle of attack of the sideslip deviation parameter, and the neutral angle of attack of the lateral control deviation parameter;

[0083] The critical angle of attack is obtained according to static wind tunnel test data, and the angle of attack corresponding to the maximum lift coefficient in the static wind tunnel test is the critical angle of attack;

[0084] The sideslip deviation parameter neutral angle of attack is based on the sideslip deviation parameter The expression formula is calculated as follows:

[0085]

[0086] In the formula, is the heading static stability derivative, is the angle of attack, is the lateral static stability derivative, , is the moment of inertia of the aircraft about the body axis, let the right side be 0, and the angle of attack obtained is the neutral angle of attack of the sideslip deviation parameter;

[0087] The lateral control deviation parameter neutral angle of attack is calculated according to the expression formula of the lateral control deviation parameter LCDP, specifically:

[0088]

[0089] In the formula, is the heading static stability derivative, is the lateral static stability derivative, is the derivative of the yaw moment coefficient with respect to the aileron deflection, is the derivative of the rolling moment coefficient with respect to the aileron deflection. Let the right side be 0, and the angle of attack obtained is the neutral angle of attack of the sideslip deviation parameter.

[0090] Preferably, the aircraft deviation and spin sensitivity is predicted by using a semi-empirical stability static criterion, and compared with the deviation and spin sensitivity of similar aircraft models;

[0091] The semi-empirical stability static criterion is based on the sideslip deviation parameter and lateral control deviation parameters LCDP Combination

[0092] When using, As the horizontal axis, LCDP As the ordinate, the angle of attack As parameter variables, four regions A\B\C\D are divided on the coordinate plane, and the deviation characteristic curve of the actual aircraft is drawn to determine the sensitivity of the aircraft to deviation and tailspin;

[0093] If the curve is in area A, it indicates no deviation trend; if the curve is in area B, it indicates mild initial yaw divergence, followed by reverse roll (mild roll deviation), with low spin sensitivity; if the curve is in area C, it indicates moderate initial yaw divergence, followed by reverse roll (moderate roll deviation), which is moderate spin sensitivity; if the curve is in area D, it indicates strong yaw divergence and reverse roll, with high spin sensitivity;

[0094] The critical angle of attack, the sideslip deviation parameter neutral angle of attack, and the lateral control deviation parameter neutral angle of attack are averaged to obtain the deviation angle of attack;

[0095] The deviation characteristics are comprehensive characteristics of three dimensions: pitch deviation characteristics, roll deviation characteristics, and direction deviation characteristics, and the weight value is determined according to the dynamic characteristics of the aircraft deviation process;

[0096] When the aircraft's angle of attack increases, airflow separation will cause the nose to pitch up, which is the initial stage of the deviation process and has a greater impact on the aircraft's longitudinal stability. As the nose pitches up, the aircraft will generate a rolling moment, causing the aircraft to roll away, which is the mid-term stage of the deviation process and has a greater impact on the aircraft's lateral stability. Finally, the aircraft will yaw, which is the final stage of the deviation process and has a greater impact on the aircraft's directional stability. Roll deviation and directional deviation will directly affect the possibility of the aircraft entering a spin, so the weights of these two dimensions are relatively high. Although pitch deviation will cause the nose to pitch up, if the aircraft has sufficient longitudinal stability, it can avoid entering a spin, so the weight of this dimension is relatively low.

[0097] The weight of the pitch deviation characteristic is 0.3, the weight of the roll deviation characteristic is 0.4, and the weight of the direction deviation characteristic is 0.4. This is because the deviation of the aircraft is first reflected in the airflow separation after the angle of attack increases, resulting in roll deviation, followed by direction deviation, and finally the nose pitches up. The roll deviation and direction deviation will cause the aircraft to enter a tailspin.

[0098] The pitch deviation characteristic is used to evaluate the longitudinal stability and stability region boundary of the aircraft;

[0099] The roll deviation characteristics and direction deviation characteristics are used to evaluate the corresponding aerodynamic damping characteristics and the control efficiency of the aerodynamic control surface;

[0100] The spin sensitivity is compared with that of the same type of aircraft in the same angle of attack section. If it is the same as that of the same type of aircraft, it is normal; if it is more sensitive than the same type of aircraft, the characteristic is poor and the subsequent evaluation score is lower; if the sensitivity is lower, the characteristic is better and the subsequent evaluation score is higher.

[0101] The aircraft deviation characteristics and spin sensitivity are evaluated by comparing the deviation angle of attack and spin sensitivity with similar aircraft, as well as the degree of deviation characteristics.

[0102] Preferably, the control law design evaluates the control law's automatic anti-deviation capability and the degree to which worry-free operation can be achieved;

[0103] The automatic anti-deviation capability of the control law includes the ability to quickly issue an early warning when the aircraft is about to enter a stall state, and to quickly correct the deviation by automatically adjusting the flight state. At the same time, in complex flight environments, the anti-deviation control law can effectively suppress external interference and prevent the aircraft from entering a dangerous state due to stall deviation;

[0104] The degree to which the control law achieves worry-free operation includes the ability of the control law to achieve ease of operation, operational reliability and human-machine interaction friendliness within the design range. Specifically, when the pilot faces the risk of stall, he only needs to perform simple operations according to the operating prompts of the anti-deviation control law to achieve automatic anti-deviation of the aircraft; the anti-deviation control law can work stably under various known complex flight conditions to ensure that the pilot can perform worry-free operation; the design of the anti-deviation control law should fully consider the pilot's operating habits and psychological needs, and provide intuitive and easy-to-understand feedback information.

[0105] Preferably, the anti-deviation control law is evaluated based on the following indicators:

[0106] Stall warning accuracy control, stall correction success rate control, system failure rate control, and system recovery time control;

[0107] The stall warning accuracy control refers to the probability that the anti-deviation control law can accurately warn of stall deviation within a predetermined threshold;

[0108] Conduct a large number of simulated flight tests through flight simulators to record the stall warning conditions of the aircraft under critical flight conditions;

[0109] Analyze the triggering conditions of the early warning system to ensure that it can provide a warning before the aircraft actually enters a stall; compare the time difference between the output of the early warning system and the actual stall state of the aircraft to evaluate the timeliness of the warning.

[0110] The warning accuracy score is converted into a percentage, with a full score of 100, that is, the warning accuracy is 100%, and the average of all tests is taken. If the warning system issues a warning within 5 seconds before the aircraft enters a stall, the accuracy is recorded as 100% accurate and the score is 100 points; if the warning time is within 5-10 seconds, the accuracy is recorded as 80% and the score is 80 points; if the warning time exceeds 10 seconds, or no warning is issued, the accuracy is recorded as 0% and the score is 0 points;

[0111] Stall correction success rate control refers to the probability that the aircraft can successfully correct the stall deviation after the warning. The evaluation method is to use a flight simulator to simulate the aircraft stall deviation scenario and record the correction effect of the anti-deviation control law;

[0112] The stall correction success rate score is converted into a percentage score, with a full score of 100, that is, a correction success rate of 100%, and the average of all tests is taken. If the aircraft successfully returns to a safe flight state within 5 seconds after the warning, it is recorded as 100% correction success and scored 100 points; if the return time is within 5-10 seconds, the correction success rate is recorded as 80%, and the score is 80 points; if the return time exceeds 10 seconds, or the correction fails, no points will be awarded;

[0113] System failure rate control refers to the failure rate of the designed aircraft anti-deviation control law in actual operation. Its evaluation method is to record the failure of the anti-deviation control law through long-term actual flight tests and simulation tests, and use the number of failures per thousand flight hours (FFH) as an indicator;

[0114] If FFH is less than 0.1, the score is 100 points; if FFH is between 0.1 and 1, the score is 80 points; if FFH exceeds 1, the score is 60 points;

[0115] System recovery time control refers to the time required for the anti-deviation control law to resume normal operation after a control law failure occurs. The self-diagnosis and recovery capabilities of the control law system are evaluated by intentionally introducing a fault in a simulation test and recording the time from the occurrence of the fault to the restoration of normal operation.

[0116] The recovery time score adopts the time threshold method, with a full score of 100. If the system returns to normal within 0.5 minutes, the score is 100 points; if the recovery time is between 0.5 and 2 minutes, the score is 80 points; if the recovery time exceeds 2 minutes, the score is 60 points.

[0117] The beneficial effects of the present invention compared with the prior art are as follows:

[0118] More comprehensive. The present invention comprehensively evaluates the high angle of attack characteristics of the aircraft from the two dimensions of stall and deviation, covering multiple aspects such as aerodynamic model, stall warning, characteristic prediction, control law design, etc., which is more comprehensive than the existing technology. The present invention not only evaluates the aerodynamic characteristics, but also evaluates the timing and effectiveness of the stall warning, as well as the deviation characteristics, spin sensitivity, the working efficiency and reliability of the anti-deviation control law, etc., reflecting the safety of the aircraft more comprehensively than the existing technology.

[0119] More efficient: The modeling method and evaluation framework adopted by the present invention have low computational complexity and can be quickly solved on a computing device of general performance, which is more efficient than the prior art; the present invention intuitively displays the stall / deviation characteristics of the aircraft through a polygonal radar chart, which facilitates rapid identification of advantages and disadvantages, and is more intuitive and efficient than the prior art.

[0120] More operable. The present invention adopts a clear logical framework and evaluation process, which is easy to understand and operate, and is easier to apply than the existing technology. The present invention adopts a polygonal radar chart to visualize the evaluation results, which is intuitive and easy to understand, and is easier to understand and apply than the existing technology.

[0121] The invention has wider application, and is applicable to different types of aircraft, including military aircraft and civil airliners, and has wide application value; the invention can be used in various stages of aircraft design, including conceptual design, preliminary design and detailed design stages, to provide a reference for aircraft design. BRIEF DESCRIPTION OF THE DRAWINGS

[0122] Figure 1 A multi-dimensional evaluation diagram of stall / deviation characteristics of a preferred embodiment of the present application;

[0123] Figure 2 This is a comprehensive analysis diagram of the preferred embodiment of this application. DETAILED DESCRIPTION

[0124] The present invention is described in detail below with reference to the accompanying drawings and embodiments:

[0125] Attached Figure 1 It can be seen that the comprehensive characterization method of aircraft stall / spin characteristics includes stall dimension and deviation dimension. The stall dimension includes aircraft high angle of attack nonlinear aerodynamic modeling and aircraft stall warning; the deviation dimension includes aircraft deviation characteristics and spin sensitivity, and control law design.

[0126] The stall dimension mainly examines the ability to characterize the aerodynamic characteristics of the aircraft at high angles of attack and the corresponding characteristics that the aircraft can warn when approaching the stall area.

[0127] The aircraft high angle of attack nonlinear aerodynamic modeling refers to a mathematical model established for flight performance analysis, control law design and flight simulation research. The model should be able to accurately and completely describe the aircraft's nonlinear aerodynamic force in the high angle of attack area, and the aerodynamic parameters in the model should be obtained after rigorous identification.

[0128] When conducting an evaluation, regardless of whether the modeling method is mathematical modeling, intelligent learning modeling, or a comprehensive modeling method that combines multiple means, it should be ensured that the model has good prediction accuracy, and the error between the predicted high angle of attack aerodynamic characteristics and the flight test should be smaller than that of the mathematical aerodynamic model (such as the dynamic derivative model); at the same time, the solution process should be clear and concise, with rigorous logic and solution framework, low computational complexity, and able to be quickly solved with low machine time on a general performance computing device.

[0129] The high angle of attack nonlinear aerodynamic modeling characteristics are evaluated by prediction accuracy and logical accuracy. The prediction accuracy refers to comparing the established aerodynamic model with the flight test data and calculating the prediction error. The prediction accuracy score uses the relative error percentage, with a full score of 100 points, and the average value of all angles of attack states is taken. If the error between the high angle of attack aerodynamic characteristics predicted by the model and the flight test data is less than 2%, the score is 100 points; if the error is between 2% and 8%, the score is 80 points; if the error is between 8% and 15%, the score is 60 points; if the error exceeds 15%, no score. The logical accuracy refers to a qualitative assessment of whether the model's solution framework is clear and the logic is rigorous. The logical accuracy score is scored on a 100-point scale. If the solution process is completely clear, logical, and unambiguous, the score is 100 points; if the solution process is relatively clear but there are a few unclear points, the score is 80 points; if the solution process is partially unclear or has a few logical loopholes, but the solution result is within the allowable range, the score is 60 points; if the solution process is obviously unclear or has a large number of logical loopholes, it will be scored 0 points.

[0130] The stall warning of the aircraft refers to the natural or artificial stall warning that the pilot can obtain clearly through hearing, vision, touch, etc. The natural stall warning refers to the stall warning such as vibration, shaking, sound, etc. that the pilot can clearly perceive from the body under normal physiological and psychological conditions; the artificial stall warning refers to the installation of electronic or mechanical airborne equipment, which can provide the pilot with sufficient stall warning information in the form of voice, light, buzzer, joystick or seat shaking, etc. when the aircraft is about to enter or is entering a stall state.

[0131] When conducting the assessment, no matter what warning method is used, the driver should be given a sufficient and effective warning before the stall occurs. The warning should not be too early or too late. When the angle of attack reaches 60% of the stall angle of attack, the approaching reminder should be started, and the warning intensity should be increased as the angle of attack increases. Even in a complex driving environment, the driver should have a clear warning perception. All warning methods should be clear, effective and not complicated. The effectiveness of the warning should not be reduced in order to increase the diversity of the warning.

[0132] The stall warning situation of the aircraft is evaluated from the two aspects of natural warning and artificial warning, with the warning timing and warning effectiveness. The warning timing refers to the effective moment when the aircraft or airborne equipment gives the pilot a stall warning reminder. Natural warnings need to evaluate the pilot's perception of fuselage vibration under normal physiological and psychological conditions, so as to check whether the fuselage vibration starts when the angle of attack reaches 60% of the stall angle of attack and increases with the increase of the angle of attack. The warning timing and warning effectiveness scores are in the form of percentages, with a full score of 100 points. If the fuselage shake starts when the angle of attack reaches 60% of the stall angle of attack, and the pilot can clearly feel it, the score is recorded as 100 points; if the fuselage shake starts later, but before the angle of attack reaches 70% of the stall angle of attack, and the pilot can feel it, the score is recorded as 80 points; if the fuselage shake starts before the stall angle of attack but later than 70% of the stall angle of attack, or earlier than 60% of the stall angle of attack, or the shake can occur within the specified angle of attack range but the shake is not obvious, the score is recorded as 60 points; if the fuselage shakes close to the stall angle of attack, or there is no shake phenomenon, the score is recorded as 0 points. The effectiveness of the warning involves testing the manual warning system in a complex driving environment, evaluating the complexity of the equipment and its potential interference with the pilot's operation, so as to verify the clarity and effectiveness of its information. The effectiveness of the warning is scored in the form of clarity and simplicity of the warning, using a percentage system with a full score of 100. If the warning method is clear and effective and does not increase the pilot's operating burden, the score is 100 points; if the warning method is relatively clear but there is a small amount of interference, the score is 80 points; if the warning method is complicated and causes difficulty or confusion for the pilot, the score is 60 points; if the warning method cannot allow the pilot to obtain clear warning information, no points will be awarded.

[0133] The deviation dimension comprehensively examines the aircraft's deviation characteristics and spin sensitivity based on static stability, and whether it has the ability to prevent deviation without relying on human control.

[0134] The aircraft deviation characteristics and spin sensitivity refer to predicting the aircraft's deviation angle of attack, deviation characteristics and spin sensitivity in a specific state through deviation criteria, and comparing them with similar models. The deviation criterion is a mature static engineering criterion with high reliability and universality. The deviation angle of attack should be comprehensively determined based on the critical angle of attack, the sideslip deviation parameter neutral angle of attack, and the lateral control deviation parameter neutral angle of attack. The critical angle of attack can be obtained based on static wind tunnel test data. The angle of attack corresponding to the maximum lift coefficient in the static wind tunnel test is the critical angle of attack; the sideslip deviation parameter neutral angle of attack is determined based on the sideslip deviation parameter. The expression formula is calculated, specifically:

[0135]

[0136] In the formula, is the heading static stability derivative, is the angle of attack, is the lateral static stability derivative, , is the moment of inertia of the aircraft about the fuselage axis, and the right side is set to 0. The angle of attack obtained is the neutral angle of attack of the sideslip deviation parameter; the neutral angle of attack of the lateral control deviation parameter is calculated according to the lateral control deviation parameter LCDP The expression formula is calculated, specifically:

[0137]

[0138] In the formula, is the heading static stability derivative, is the lateral static stability derivative, is the derivative of the yaw moment coefficient with respect to the aileron deflection, is the derivative of the rolling moment coefficient with respect to the aileron deflection. Let the right side be 0, and the angle of attack obtained is the neutral angle of attack of the sideslip deviation parameter. The aircraft deviation and spin sensitivity are predicted by the semi-empirical stability static criterion, and compared with the deviation and spin sensitivity of similar aircraft. The semi-empirical stability static criterion is based on the sideslip deviation parameter. and lateral control deviation parameters LCDP When in use, As the horizontal axis, LCDP As the ordinate, the angle of attack As parameter variables, four areas A\B\C\D are divided on the coordinate plane, and the deviation characteristic curve of the actual aircraft is drawn to determine the aircraft's deviation and tailspin sensitivity.

[0139] When evaluating, the critical angle of attack, the neutral angle of attack of the sideslip deviation parameter, and the neutral angle of attack of the lateral control deviation parameter are averaged, and the deviation angle is obtained. The deviation angle is compared with the deviation angle of attack of the same type of aircraft. If it is higher than the average deviation angle of attack of the same type of aircraft, it indicates that it has better deviation characteristics and a larger normal flight margin. The deviation characteristics are comprehensive characteristics of three dimensions: pitch deviation characteristics, roll deviation characteristics, and direction deviation characteristics. The weight of the pitch deviation characteristic is 0.3, the weight of the roll deviation characteristic is 0.4, and the weight of the direction deviation characteristic is 0.4. This is because the deviation of the aircraft is first reflected in the roll deviation caused by the separation of the airflow after the angle of attack increases, followed by the direction deviation, and finally the nose is tilted up, and the roll deviation and direction deviation will cause the aircraft to enter a tailspin. The pitch deviation characteristic mainly evaluates the longitudinal stability and stability domain boundary of the aircraft, and the roll deviation characteristic and the direction deviation characteristic mainly evaluate the corresponding aerodynamic damping characteristics and the control efficiency of the aerodynamic control surface. When analyzing spin sensitivity, compare it with the spin sensitivity of the same type of aircraft in the same angle of attack section. If it is the same as the spin sensitivity of the same type of aircraft, it is normal; if it is more sensitive than the same type of aircraft, the characteristic is poorer and the subsequent evaluation score is lower; if the sensitivity is lower, the characteristic is better and the subsequent evaluation score is higher.

[0140] The deviation characteristics and spin sensitivity of an aircraft are evaluated by comparing the deviation angle of attack and spin sensitivity with aircraft of the same type, as well as the degree of deviation characteristics. When comparing the deviation angle of attack, first calculate the average value of the critical angle of attack, the neutral angle of attack of the sideslip deviation parameter, and the neutral angle of attack of the lateral control deviation parameter to determine the deviation angle of attack. Then compare the obtained deviation angle of attack with the average deviation angle of attack of aircraft of the same type. If the deviation angle of attack is higher than the average deviation angle of attack of aircraft of the same type, the score is recorded as 100 points; if the deviation angle of attack is the same as the average deviation angle of attack of aircraft of the same type, the score is recorded as 80 points; if the deviation angle of attack is lower than the average deviation angle of attack of aircraft of the same type, the score is recorded as 60 points. When comparing the spin sensitivity, it is necessary to compare the spin sensitivity of the aircraft with that of aircraft of the same type within the same angle of attack section to evaluate the difficulty of the aircraft entering a spin. The spin sensitivity score adopts the relative comparison method, with a full score of 100 points. If the spin sensitivity is the same as that of the same type of aircraft, the score is 80 points; if the spin sensitivity is higher than that of the same type of aircraft, the score is 60 points; if the spin sensitivity is lower than that of the same type of aircraft, the score is 100 points. When evaluating the deviation characteristics, the pitch deviation characteristic score E1, the roll deviation characteristic score E2, and the direction deviation characteristic score E3 are evaluated in a percentage system, and a comprehensive deviation characteristic score E is performed. If the aircraft shows good longitudinal stability before the critical angle of attack, the nose pitch speed is moderate, and the restoring moment is sufficient, the score is 90-100 points; if the aircraft has average longitudinal stability before the critical angle of attack, the nose pitch speed is fast, and the restoring moment is acceptable, the score is 70-89 points; if the aircraft has poor longitudinal stability before the critical angle of attack, the nose pitch speed is too fast, and the restoring moment is insufficient, the score is 60-69 points. If the aircraft has large roll damping and moderate roll rate under sideslip conditions, the score is 90-100 points; if the aircraft has average roll damping and fast roll rate under sideslip conditions, the score is 70-89 points; if the aircraft has small roll damping and too fast roll rate under sideslip conditions, the score is 60-69 points. If the aircraft has large directional damping and good yaw stability under sideslip conditions, the score is 90-100 points; if the aircraft has average directional damping and fair yaw stability under sideslip conditions, the score is 70-89 points; if the aircraft has small directional damping and poor yaw stability under sideslip conditions, the score is 60-69 points. Finally, a comprehensive deviation characteristic score is calculated using the following formula:

[0141] E=E1×0.3+E2×0.4+E3×0.4

[0142] The control law design refers to the design verification and evaluation of the flight control system control method on the fly-by-wire aircraft to ensure flight safety. The evaluation content mainly refers to the automatic anti-deviation capability of the simulated aircraft under typical working conditions, with the working efficiency and reliability of the control law as the evaluation index. The control law design is based on the full consideration of the nonlinearity, uncertainty and coupling effects of the aircraft under critical flight conditions such as low speed and high angle of attack, and adopts modern control theory, combined with adaptive control, robust control and other technologies, to design a flight control law suitable for aircraft anti-stall deviation, and through numerical simulation and flight simulation tests, the anti-stall deviation control law is verified and optimized to ensure its effectiveness in actual flight.

[0143] When conducting the evaluation, the automatic anti-deviation capability and the degree of worry-free operation of the control law are mainly evaluated. The automatic anti-deviation capability of the control law includes that when the aircraft is about to enter the stall state, the anti-deviation control law can quickly issue an early warning and quickly correct the deviation by automatically adjusting the flight state. At the same time, in complex flight environments, the anti-deviation control law can effectively suppress external interference and prevent the aircraft from entering a dangerous state due to stall deviation. The degree of worry-free operation of the control law includes that the control law can achieve ease of operation, reliability of operation and human-computer interaction friendliness within the design range. Specifically, when the pilot faces the risk of stalling, he only needs to perform simple operations according to the operation prompts of the anti-deviation control law to achieve automatic anti-deviation of the aircraft; the anti-deviation control law can work stably under various known complex flight conditions to ensure that the pilot can perform worry-free operation; the design of the anti-deviation control law should fully consider the pilot's operating habits and psychological needs, and provide intuitive and easy-to-understand feedback information.

[0144] The following indicators are used to evaluate the working efficiency and reliability of the anti-deviation control law: stall warning accuracy, stall correction success rate, system failure rate, and system recovery time. The stall warning accuracy refers to the probability that the anti-deviation control law can accurately warn of stall deviation within a predetermined threshold. The evaluation method includes conducting a large number of simulated flight tests through a flight simulator to record the stall warning of the aircraft in a critical flight state; analyzing the triggering conditions of the warning system to ensure that it can provide a warning before the aircraft actually enters a stall; comparing the time difference between the output of the warning system and the actual stall state of the aircraft to evaluate the timeliness of the warning. The warning accuracy score is converted into a score in the form of a percentage, with a full score of 100 points, that is, the warning accuracy is 100%, and the average value of all tests is taken. If the warning system issues a warning within 5 seconds before the aircraft enters a stall, the accuracy is recorded as 100% accurate and the score is 100 points; if the warning time is within 5-10 seconds, the accuracy is recorded as 80% and the score is 80 points; if the warning time exceeds 10 seconds, or the warning fails, the accuracy is recorded as 0% and the score is 0 points. The stall correction success rate refers to the probability that the aircraft can successfully correct the stall deviation after the warning. The evaluation method is to use a flight simulator to simulate the aircraft stall deviation scenario and record the correction effect of the anti-deviation control law. The stall correction success rate score is converted into a percentage, with a full score of 100 points, that is, the correction success rate is 100%, and the average of all tests is taken. If the aircraft successfully returns to a safe flight state within 5 seconds after the warning, it is recorded as 100% correction success and scored 100 points; if the return time is within 5-10 seconds, the correction success rate is recorded as 80%, and the score is 80 points; if the return time exceeds 10 seconds, or the correction fails, no score is given. The system failure rate refers to the failure rate of the designed aircraft anti-deviation control law in actual operation. The evaluation method is to record the failure of the anti-deviation control law through long-term actual flight tests and simulation tests, and use the number of failures per thousand flight hours (FFH) as an indicator. If FFH is less than 0.1, the score is 100 points; if FFH is between 0.1 and 1, the score is 80 points; if FFH exceeds 1, the score is 60 points. The system recovery time refers to the time required for the anti-deviation control law to resume normal operation after a control law failure occurs. The self-diagnosis and recovery capabilities of the control law system are evaluated by deliberately introducing a fault in a simulation test and recording the time from the occurrence of the fault to the restoration of normal operation. The recovery time score adopts the time threshold method, with a full score of 100 points. If the system returns to normal within 0.5 minutes, the score is 100 points; if the recovery time is between 0.5 and 2 minutes, the score is 80 points; if the recovery time exceeds 2 minutes, the score is 60 points.

[0145] Finally, a comprehensive examination is conducted on the different levels of each dimension, and the scores of all scoring points are calculated. The scoring points of the stall dimension include the prediction accuracy and logical accuracy of the high angle of attack aerodynamic modeling, the warning timing and warning effectiveness of the stall warning, a total of 4 points; the scoring points of the deviation dimension include the deviation angle of attack, spin sensitivity, comprehensive deviation characteristics in the deviation characteristics, and the warning accuracy, stall correction success rate, system failure rate, and system recovery time in the anti-deviation control law, a total of 7 points.

[0146] The evaluation of each level is summarized in the form of a score, and a total of 11 scoring points in all dimensions are visualized in a polygonal radar chart, with the polygon coverage representing the stall / deviation characteristics of the aircraft. Each scoring point is drawn on the radar chart to form a polygon, in which each corner represents a scoring point. The polygon coverage can reflect the overall performance of the aircraft in terms of stall / deviation characteristics. The greater the coverage, the better the performance of the aircraft in this dimension. By analyzing the radar chart, it is possible to find out in which aspects the aircraft has advantages and which aspects need improvement, thereby providing guidance for aircraft design optimization and flight safety.

[0147] Taking the stall / deviation characteristics of two different design configurations of an aircraft as an example, a comprehensive analysis is conducted.

[0148] In the stall dimension, the error between the high angle of attack aerodynamic characteristics predicted by the high angle of attack aerodynamic model and the flight test data of the aircraft A configuration is between 2% and 8%, and the prediction accuracy is scored 80 points; the definition of the model's solution framework is completely clear, logical, and unambiguous, and the logical accuracy is scored 100 points; the fuselage vibration starts before the angle of attack reaches 70% of the stall angle of attack, and the pilot can perceive it, and the warning timing is scored 80 points; the warning method of the manual warning system is relatively clear, but there is a small amount of interference that does not affect the pilot's operation, and the warning effectiveness is scored 80 points. In the deviation dimension, the deviation angle of attack is lower than the average deviation angle of attack of aircraft of the same type, and the deviation angle of attack score is 60 points; it is relatively sensitive to spins, and the spin sensitivity score is 60 points; the comprehensive deviation characteristic score E score is 77 points; the warning time of the anti-deviation control law is 7 seconds, and the warning accuracy score is 80 points; the aircraft returns to a safe flight state within 6 seconds after the warning, and the stall correction success rate score is 80 points; the system failure rate is relatively high, with FFH reaching 1.1, and the system failure rate score is 60 points; it can return to normal within 20 seconds after a failure, and the system recovery time score is 100 points.

[0149] In the stall dimension, the error between the high angle of attack aerodynamic characteristics predicted by the high angle of attack aerodynamic model and the flight test data for the aircraft Configuration B is between 2% and 8%, with a prediction accuracy score of 80 points; the model's solution framework is completely clear, logical, and unambiguous, with a logical accuracy score of 100 points; the fuselage shake starts before the angle of attack reaches 60% of the stall angle of attack, and the pilot can clearly perceive it, with a warning timing score of 100 points; the warning method of the manual warning system is relatively clear, but there is a small amount of interference that does not affect the pilot's operation, with a warning effectiveness score of 80 points. In the deviation dimension, the deviation angle of attack is basically the same as the average deviation angle of attack of aircraft of the same type, and the deviation angle of attack is scored as 80 points; it is insensitive to spins, and the spin sensitivity is scored as 80 points; the comprehensive deviation characteristic score E is 84 points; the warning time of the anti-deviation control law is 5 seconds, and the warning accuracy is scored as 100 points; the aircraft returns to a safe flight state within 8 seconds after the warning, and the stall correction success rate is scored as 80 points; the system failure rate is low, with FFH only 0.08, and the system failure rate is scored as 100 points; it fails to return to normal within 2 minutes after a failure, and the system recovery time is scored as 60 points.

[0150] A comprehensive analysis chart of stall / deviation characteristics is drawn based on the scores of the two configurations. From the chart, we can clearly compare the strengths and weaknesses of the two models in different characteristics. At the same time, based on the size of the polygon coverage area, we can determine which model has better stall / deviation characteristics. Specifically:

[0151] In the stall dimension:

[0152] The prediction accuracy and logic accuracy of the high angle of attack aerodynamic model of configuration A were both scored 80 points, the fuselage vibration warning timing was scored 80 points, and the manual warning effectiveness was scored 80 points. This shows that the stall warning system of configuration A is relatively effective, but there are still some shortcomings.

[0153] Configuration B scored 100 points for high angle of attack aerodynamic model prediction accuracy and logic accuracy, 100 points for fuselage vibration warning timing, and 80 points for manual warning effectiveness. Configuration B's stall warning system is more complete, able to predict stall more accurately and give pilots clear warning information.

[0154] In the deviating dimension:

[0155] Configuration A scored 60 points for the deviation angle of attack, 60 points for the spin sensitivity, and 77 points for the comprehensive deviation characteristics. Configuration A performed poorly in terms of deviation characteristics, with a low deviation angle of attack, high spin sensitivity, and average overall deviation characteristics.

[0156] Configuration B scored 80 points for the deviation angle of attack, 80 points for the spin sensitivity, and 84 points for the comprehensive deviation characteristics. Configuration B performed well in terms of deviation characteristics, with a deviation angle of attack that was the same as that of similar aircraft, low spin sensitivity, and better overall deviation characteristics than Configuration A.

[0157] In the anti-deviation control law:

[0158] Configuration A's warning accuracy is scored 80 points, stall correction success rate is scored 80 points, system failure rate is scored 60 points, and system recovery time is scored 100 points. The anti-deviation control law of configuration A can effectively issue warnings and correct stalls, but the system failure rate is high and needs to be improved.

[0159] Configuration B's warning accuracy is scored 100 points, the stall correction success rate is scored 80 points, the system failure rate is scored 100 points, and the system recovery time is scored 60 points. The anti-deviation control law of Configuration B can issue warnings and correct stalls more accurately, and the system failure rate is low, but the recovery time is long, which needs to be improved.

[0160] In addition, from Figure 2 A comprehensive analysis shows that the polygonal coverage area of ​​Configuration B is larger, indicating that its overall performance in stall / deviation characteristics is better than that of Configuration A.

[0161] The conclusion is: the stall / deviation characteristics of configuration B are better. Its stall warning system is more complete, the deviation characteristics are better, and the anti-deviation control law is more reliable.

[0162] The above is only a preferred embodiment of the present invention, and does not limit the structure of the present invention in any form. Any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention are within the scope of the technical solution of the present invention.

Claims

1. A method for characterizing aircraft stall and deviation characteristics, characterized in that: Including stall dimension characterization method and deviation dimension characterization method; The stall dimension characterization method includes the establishment of the stall function model, the determination of the corresponding parameters and the stall alarm; The establishment of the stall function model includes: Modeling of nonlinear aerodynamic forces at high angles of attack of aircraft, and evaluating the model's prediction accuracy and logical accuracy; The aircraft high angle of attack nonlinear aerodynamic modeling is a mathematical model established based on flight performance analysis, control law design and flight simulation research; The deviation dimension characterization method includes using the deviation angle of attack, deviation characteristics, and spin sensitivity obtained by static criteria to compare with similar aircraft models as evaluation indicators to evaluate the aircraft's deviation characteristics and spin sensitivity, and using the working efficiency and reliability of the anti-deviation control law as evaluation indicators to evaluate whether the aircraft can automatically resist deviation and whether it can achieve worry-free control; The stall function model is a dynamic derivative model; The dynamic derivative model predicts the force conditions of the aircraft under different flight conditions by establishing the functional relationship between the aerodynamic coefficients and the aircraft state variables. The process of establishing the dynamic derivative model includes: establishing a high angle of attack aerodynamic database based on wind tunnel test data, and forming a dynamic derivative model from multiple dynamic derivative coefficients in the database; using wind tunnel test data and parameter identification methods to calculate the estimated values ​​of model parameters; using flight test data or scaled model flight test data to accurately identify the parameters of the estimated values ​​and verify the accuracy of the dynamic derivative model; The dynamic derivative model decomposes the aerodynamic force into three parts: static aerodynamic force, oscillating aerodynamic force and rotating aerodynamic force. The dynamic derivative model is expressed as follows: in, , ; represents the axial force coefficient of the body shaft system, represents the lateral force coefficient of the body axis system, represents the normal force coefficient of the body axis system, represents the rolling moment coefficient, represents the pitching moment coefficient, represents the yaw moment coefficient, represents the angle of attack, represents the sideslip angle, , , Respectively represent the aileron, pitch, and yaw rudder deflection angles, the unit is degree; In the above formula, It represents the static aerodynamic data item in the high angle of attack wind tunnel test, including the static aerodynamic item when the rudder deflection is zero and the static aerodynamic increment item caused by the rudder surface deflection; The aerodynamic terms caused by the forced oscillatory motion in the high angle of attack wind tunnel test; It is the aerodynamic term caused by rotational motion in high angle of attack wind tunnel test.

2. The method for characterizing the stall and deviation characteristics of an aircraft according to claim 1, characterized in that include: Flight performance analysis, control law design, flight simulation and verification model accuracy; Flight performance analysis: by analyzing the performance indicators of the aircraft under different flight conditions and the aerodynamic characteristics of the aircraft under different angles of attack, speeds, altitudes, etc., the structure of the mathematical model is determined. Based on the flight performance indicators and aerodynamic characteristics, a nonlinear aerodynamic model of the aircraft at high angles of attack is established, and the model parameters are determined; Control law design: determine the control target of the control law based on flight performance indicators and aerodynamic characteristics; select the control method based on the control target; design the aircraft's control law based on the control method and aerodynamic model, and determine the control law parameters; Flight simulation: Establish a flight simulation model that includes aircraft dynamics model, aerodynamic model and control law model; conduct simulation tests to verify the effectiveness of the aerodynamic model and control law, and evaluate the performance of the aircraft under different flight conditions; optimize the aerodynamic model and control law parameters based on the simulation test results to improve the accuracy of the model and the performance of the control law; Verify the model accuracy, compare the established mathematical model with the flight test data, and evaluate the model's prediction accuracy; analyze the model's prediction error and find out the cause of the error; optimize the model parameters based on the error analysis results to improve the model's accuracy.

3. The method for characterizing aircraft stall and deviation characteristics according to claim 1, characterized in that: When performing error analysis and verification and optimization on the model, first find out the cause of the error; then compare the model prediction results with the flight test data to evaluate the model's prediction accuracy; finally, based on the verification results, continue to optimize the model to improve the prediction accuracy.

4. The method for characterizing aircraft stall and deviation characteristics according to claim 1, characterized in that: The effective time for the aircraft or airborne equipment to give the pilot a stall warning reminder determines the warning timing; The deviation dimension is based on the deviation characteristics and spin sensitivity of the aircraft's static stability, and whether it has the ability to prevent deviation without relying on human control; The deviation angle of attack, deviation characteristics and spin sensitivity of the aircraft in a specific state are predicted by deviation criteria and compared with similar models.

5. The method for characterizing aircraft stall and deviation characteristics according to claim 1, characterized in that: Determine the solution framework of the dynamic derivative model, including the following steps: Check the model structure, including physical meaning, units and value range; all formulas in the model have a clear derivation process, including the source of the formula, assumptions and derivation steps; if the model contains multiple equations, check whether the equation system is closed, that is, whether all unknown quantities can be solved through the equation system; Check the model logic, and make sure that the model output has clear physical meaning and is consistent with the actual situation. The model takes boundary conditions into consideration and ensures that the model is still valid under these boundary conditions. If the model requires numerical calculations, check the convergence of the model to ensure that the calculation results are stable and reliable. Check model validation, verify the logic and accuracy of the model through theoretical analysis, compare with other theoretical models, or perform limit case analysis; verify the prediction accuracy of the model through test data, and compare the model prediction results with flight test data; Check the readability of the model. The model documentation should be clear and easy to understand, including the model structure, formula derivation, parameter description, and usage methods. If the model is implemented using a computer program, the code should be standardized and annotated to facilitate others' understanding and use.

6. The method for characterizing aircraft stall and deviation characteristics according to claim 1, characterized in that: The deviation angle of attack is comprehensively determined according to the critical angle of attack, the neutral angle of attack of the sideslip deviation parameter, and the neutral angle of attack of the lateral control deviation parameter; The critical angle of attack is obtained according to static wind tunnel test data, and the angle of attack corresponding to the maximum lift coefficient in the static wind tunnel test is the critical angle of attack; The sideslip deviation parameter neutral angle of attack is based on the sideslip deviation parameter The expression formula is calculated as follows: In the formula, is the heading static stability derivative, is the angle of attack, is the lateral static stability derivative, , is the moment of inertia of the aircraft about the body axis, let the right side be 0, and the angle of attack obtained is the neutral angle of attack of the sideslip deviation parameter; The lateral control deviation parameter neutral angle of attack is calculated according to the expression formula of the lateral control deviation parameter LCDP, specifically: In the formula, is the heading static stability derivative, is the lateral static stability derivative, is the derivative of the yaw moment coefficient with respect to the aileron deflection, is the derivative of the rolling moment coefficient with respect to the aileron deflection. Let the right side be 0, and the angle of attack obtained is the neutral angle of attack of the sideslip deviation parameter.

7. The method for characterizing aircraft stall and deviation characteristics according to claim 1, characterized in that: The aircraft deviation and spin sensitivity is predicted by using semi-empirical stability static criterion and compared with the deviation and spin sensitivity of similar aircraft. The semi-empirical stability static criterion is based on the sideslip deviation parameter and lateral control deviation parameters LCDP Combination When using, As the horizontal axis, LCDP As the ordinate, the angle of attack As parameter variables, four regions A\B\C\D are divided on the coordinate plane, and the deviation characteristic curve of the actual aircraft is drawn to determine the sensitivity of the aircraft to deviation and tailspin; The critical angle of attack, the sideslip deviation parameter neutral angle of attack, and the lateral control deviation parameter neutral angle of attack are averaged to obtain the deviation angle of attack; The deviation characteristics are comprehensive characteristics of three dimensions: pitch deviation characteristics, roll deviation characteristics, and direction deviation characteristics, and the weight value is determined according to the dynamic characteristics of the aircraft deviation process; The pitch deviation characteristic is used to evaluate the longitudinal stability and stability region boundary of the aircraft; The roll deviation characteristics and direction deviation characteristics are used to evaluate the corresponding aerodynamic damping characteristics and the control efficiency of the aerodynamic control surface; Spin sensitivity is compared with the spin sensitivity of the same type of aircraft in the same angle of attack section. If it is equal to the spin sensitivity of the same type of aircraft, it is normal; if it is more sensitive than the same type of aircraft, the characteristic is reduced and the subsequent evaluation score is reduced; if the sensitivity is reduced, the characteristic is improved and the subsequent evaluation score is improved; The aircraft deviation characteristics and spin sensitivity are evaluated by comparing the deviation angle of attack and spin sensitivity with similar aircraft, as well as the degree of deviation characteristics.

8. The method for characterizing aircraft stall and deviation characteristics according to claim 1, characterized in that: Control law design evaluates the control law's ability to automatically resist deviation and the degree to which worry-free operation can be achieved; The automatic anti-deviation capability of the control law includes the ability to quickly issue an early warning when the aircraft is about to enter a stall state, and to quickly correct the deviation by automatically adjusting the flight state. At the same time, in complex flight environments, the anti-deviation control law can effectively suppress external interference and prevent the aircraft from entering a dangerous state due to stall deviation; The degree to which the control law can achieve worry-free operation includes the ability of the control law to achieve ease of operation, operational reliability and human-machine interaction friendliness within the design range. Specifically, when the pilot faces the risk of stall, he only needs to perform simple operations according to the operating prompts of the anti-deviation control law to achieve automatic anti-deviation of the aircraft.

9. The method for characterizing aircraft stall and deviation characteristics according to claim 8, characterized in that: The anti-deviation control law is evaluated based on the following indicators: Stall warning accuracy control, stall correction success rate control, system failure rate control, and system recovery time control; The stall warning accuracy control refers to the probability that the anti-deviation control law can accurately warn of stall deviation within a predetermined threshold; Conduct simulated flight tests through flight simulators to record stall warning conditions of aircraft in critical flight conditions; Analyze the triggering conditions of the warning system to ensure that it can provide warning before the aircraft actually enters a stall; Compare the time difference between the output of the warning system and the actual stall state of the aircraft to evaluate the timeliness of the warning.

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