Aircraft sinking speed determination method and system under conditions of no lift force and no mass reduction

Abstract

The invention belongs to the field of aircraft drop simulation and test, and particularly relates to an aircraft sinking speed determination method and system under the condition of no lift force and no mass reduction, and the method comprises the steps: determining parameters needed by the dynamics simulation of an aircraft landing gear according to a test working condition; determining the mechanical relationship of the undercarriage according to the parameters required by simulation, and building a full-aircraft landing simulation model; performing lift simulation on the full-aircraft landing simulation model, and determining a vertical ground load of the aircraft landing gear; extracting a vertical ground load of an aircraft landing gear, performing lift-free drop simulation on the full-aircraft landing simulation model, and iteratively determining a putting height according to the ground load; and calculating the sinking speed of the full-aircraft drop test according to the putting height. Compared with the prior art, the method has the advantages that lift force simulating loading equipment is omitted, initial launching attitudes such as the pitch angle, the roll angle and the yaw angle of the aircraft are fully considered, the method can be used for guiding initial launching of a drop test, the large overload risk of free falling impact is reduced, and the number of times of adjusting the launching height can be reduced.

Description

Technical Field

[0001] This application belongs to the field of aircraft drop simulation and testing, and specifically relates to a method and system for determining the descent velocity of an aircraft under conditions of no lift and no mass reduction. Background Technology

[0002] Aircraft landing gear drop simulation and testing commonly employ two methods: lift-simulated drop and reduced-mass free fall. In drop simulation, the lift-simulated method closely resembles actual landing conditions and is easy to implement. However, reduced-mass free fall simulation requires iterative adjustments to the deployed mass to ensure that the work done by the reduced mass is roughly equivalent to the work done by the lift force, and the deployment altitude is determined by the descent velocity. In drop testing, the lift-simulated method is more complex, requiring additional equipment to apply the simulated lift force, and demands high stability from this force. Reduced-mass free fall testing, on the other hand, is simpler to implement, less costly, and more feasible.

[0003] Full-scale drop tests require specific site and equipment conditions, making simulated lift-drop methods difficult to implement. Mass reduction methods are also impractical to ensure the integrity of the entire aircraft structure. Therefore, the method of reducing the sinking velocity proposed in this invention can be used to equivalently reduce the lift's impact on landing energy during landing or carrier landing. However, excessive sinking velocity may cause impact damage to the aircraft, while insufficient sinking velocity fails to achieve the test objective. Determining the sinking velocity at the moment of impact is a problem that urgently needs to be solved. Summary of the Invention

[0004] To address the aforementioned problems, this application provides a method and system for determining the sinking velocity of an aircraft under conditions of no lift and no mass reduction, thereby solving the problem of difficulty in determining the sinking velocity of an aircraft upon touchdown in the prior art.

[0005] The technical solution of this application is: a method for determining the descent velocity of an aircraft under conditions of no lift and no mass reduction, comprising:

[0006] Determine the parameters required for simulating aircraft landing gear dynamics based on the test conditions;

[0007] The mechanical relationship of the landing gear is determined based on the parameters required for simulation, and a full-scale landing simulation model is built.

[0008] Lift simulation was performed on the full-scale landing simulation model to determine the vertical ground load on the aircraft landing gear.

[0009] Extract the vertical ground load of the aircraft landing gear, perform a no-lift drop simulation on the full-aircraft landing simulation model, and determine the drop height iteratively based on the ground load;

[0010] The sinking speed of the entire aircraft during the drop test was calculated based on the drop height.

[0011] Preferably, the mechanical relationship of the landing gear is as follows:

[0012] Total axial force of the hydropneumatic landing gear buffer Represented as:

[0013] ;

[0014] in For air spring force, For oil damping force, For internal friction, For structural constraint force;

[0015] Air spring force for:

[0016] ;

[0017] in For piston rod pressure area, The initial pressure of the air cavity, Let S be the initial volume of the air cavity, S be the buffer stroke, and n be the air variability index. Atmospheric pressure;

[0018] Oil damping force for:

[0019] ;

[0020] in Oil density, For piston rod oil pressure area, For oil orifice flow coefficient, Let v be the area of ​​the oil hole and v be the relative speed between the piston rod and the outer cylinder.

[0021] Internal friction for:

[0022] ;

[0023] in The equivalent coefficient of friction of the buffer;

[0024] Structural restraint force In the full-scale landing simulation model, it is treated as a spring with infinite stiffness.

[0025] Preferably, the vertical ground load of the aircraft landing gear is determined as follows:

[0026] Adjust the initial state of the aircraft before landing according to the test conditions, including the aircraft's heading engagement speed, descent speed, pitch angle, roll angle and yaw angle;

[0027] The simulated lift force is applied at the center of gravity, equal in magnitude and opposite in direction to the gravity force;

[0028] By simulating landing with added lift, the vertical ground loads of the nose landing gear and main landing gear are obtained.

[0029] Preferably, the specific method for determining the placement height is as follows:

[0030] Control the aircraft to crash into the ground in a free fall manner, extract the maximum ground load of the current landing gear, if the main landing gear touches the ground first, compare it with the vertical ground load of the main landing gear; if the nose landing gear touches the ground first, compare it with the vertical ground load of the nose landing gear.

[0031] If the maximum ground load is greater than the corresponding vertical ground load, the deployment height is reduced; if the maximum ground load is less than the corresponding vertical ground load, the deployment height is increased.

[0032] This process of iterating through the drop height is repeated until the error between the maximum ground load and the corresponding vertical ground load of the current landing gear is controlled within a certain range. Within.

[0033] Preferably, the method for calculating the sinking velocity during the full-scale drop test is as follows:

[0034] Substituting the drop height into the free fall formula yields the sinking speed of the aircraft landing gear tires when they touch down:

[0035] ;

[0036] in Let g be the sinking velocity, g be the acceleration due to gravity, and h be the drop height.

[0037] Preferably, the parameters required for simulating aircraft landing gear dynamics include the overall installation position, weight, center of gravity, moment of inertia, pitch angle, roll angle, yaw angle, sinking speed, and heading speed at landing.

[0038] Another technical solution of this application is: a system for determining the descent velocity of an aircraft under conditions of no lift and no mass reduction, comprising:

[0039] The simulation parameter determination module is used to determine the parameters required for simulating aircraft landing gear dynamics based on the test conditions.

[0040] The simulation model building module is used to determine the mechanical relationship of the landing gear based on the parameters required for simulation and to build a full-aircraft landing simulation model.

[0041] The ground load determination module is used to perform lift simulation on the full-aircraft landing simulation model to determine the vertical ground load of the aircraft landing gear.

[0042] The drop height determination module is used to extract the vertical ground load of the aircraft landing gear, perform a lift-free drop simulation on the full-aircraft landing simulation model, and iteratively determine the drop height based on the ground load.

[0043] The sinking speed determination module is used to calculate the sinking speed of the entire aircraft during the drop test based on the drop height.

[0044] Preferably, the mechanical relationship of the landing gear is as follows:

[0045] Total axial force of the hydropneumatic landing gear buffer Represented as:

[0046] ;

[0047] in For air spring force, For oil damping force, For internal friction, For structural constraint force;

[0048] Air spring force for:

[0049] ;

[0050] in For piston rod pressure area, The initial pressure of the air cavity, Let S be the initial volume of the air cavity, S be the buffer stroke, and n be the air variability index. Atmospheric pressure;

[0051] Oil damping force for:

[0052] ;

[0053] in Oil density, For piston rod oil pressure area, For oil orifice flow coefficient, Let v be the area of ​​the oil hole and v be the relative speed between the piston rod and the outer cylinder.

[0054] Internal friction for:

[0055] ;

[0056] in The equivalent coefficient of friction of the buffer;

[0057] Structural restraint force In the full-scale landing simulation model, it is treated as a spring with infinite stiffness.

[0058] Preferably, the vertical ground load of the aircraft landing gear is determined as follows:

[0059] Adjust the initial state of the aircraft before landing according to the test conditions, including the aircraft's heading engagement speed, descent speed, pitch angle, roll angle and yaw angle;

[0060] The simulated lift force is applied at the center of gravity, equal in magnitude and opposite in direction to the gravity force;

[0061] By simulating landing with added lift, the vertical ground loads of the nose landing gear and main landing gear are obtained.

[0062] Preferably, the specific method for determining the placement height is as follows:

[0063] Control the aircraft to crash into the ground in a free fall manner, extract the maximum ground load of the current landing gear, if the main landing gear touches the ground first, compare it with the vertical ground load of the main landing gear; if the nose landing gear touches the ground first, compare it with the vertical ground load of the nose landing gear.

[0064] If the maximum ground load is greater than the corresponding vertical ground load, the deployment height is reduced; if the maximum ground load is less than the corresponding vertical ground load, the deployment height is increased.

[0065] This process of iterating through the drop height is repeated until the error between the maximum ground load and the corresponding vertical ground load of the current landing gear is controlled within a certain range. Within.

[0066] Preferably, the method for calculating the sinking velocity during the full-scale drop test is as follows:

[0067] Substituting the drop height into the free fall formula yields the sinking speed of the aircraft landing gear tires when they touch down:

[0068] ;

[0069] in Let g be the sinking velocity, g be the acceleration due to gravity, and h be the drop height.

[0070] Preferably, the parameters required for simulating aircraft landing gear dynamics include the overall installation position, weight, center of gravity, moment of inertia, pitch angle, roll angle, yaw angle, sinking speed, and heading speed at landing.

[0071] The method and system for determining the aircraft sinking velocity under conditions of no lift and no mass reduction in this application have the following advantages:

[0072] This method not only saves on lift-simulation loading equipment but also fully considers the aircraft's initial drop attitude, including pitch, roll, and yaw angles. The determined sinking velocity and drop height can guide the initial drop test, reducing the risk of high overload from free-fall impact and minimizing the number of drop height adjustments. This method significantly improves the safety and operability of whole-aircraft drop tests and reduces the requirements for testing equipment. Attached Figure Description

[0073] Figure 1 This is a schematic diagram of the overall process of this application. Detailed Implementation

[0074] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below with reference to the accompanying drawings. In the drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The described embodiments are only some, not all, of the embodiments of this application. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application. The embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0075] The first aspect of this application provides a method for determining the descent speed of an aircraft under conditions of no lift and no mass reduction. The drop height is calculated based on the obtained descent speed. The calculated drop height can be initially set before the start of the full-aircraft drop test, thereby reducing the number of iterations of the test drop height and avoiding impact damage to the landing gear and fuselage due to an excessively large initial drop height.

[0076] like Figure 1 As shown, it includes the following steps:

[0077] Step 1: Determine the parameters required for simulating the aircraft landing gear dynamics based on the test conditions.

[0078] The parameters required for simulating aircraft landing gear dynamics include the overall installation position, weight, center of gravity, inertia, pitch angle, roll angle, yaw angle, sinking speed, and heading speed at landing.

[0079] Step 2: Determine the mechanical relationship of the landing gear based on the parameters required for simulation, and build a full-scale landing simulation model.

[0080] Preferably, the mechanical relationship of the landing gear is as follows:

[0081] Total axial force of the hydropneumatic landing gear buffer Represented as:

[0082] (1);

[0083] in For air spring force, For oil damping force, For internal friction, For structural constraint force;

[0084] Air spring force Generally, the static pressure can be obtained from the static pressure curve of the buffer. In the absence of actual static pressure measurement data, it can be calculated according to formula (2):

[0085] (2);

[0086] in For piston rod pressure area, The initial pressure of the air cavity, Let S be the initial volume of the air cavity, S be the buffer stroke, and n be the air variability index. Atmospheric pressure;

[0087] Oil damping force The direction is related to the direction of the velocity, and can be expressed as:

[0088] (3);

[0089] in Oil density, For piston rod oil pressure area, For oil orifice flow coefficient, Let v be the area of ​​the oil hole and v be the relative speed between the piston rod and the outer cylinder.

[0090] Internal friction It can be simplified to a linear function of the air spring force:

[0091] (4);

[0092] in The equivalent coefficient of friction of the buffer;

[0093] Structural restraint force It is designed to provide resistance to limit the further movement of the buffer piston rod when it reaches its maximum stroke. In the simulation model, it can be treated as a spring with infinite stiffness.

[0094] Based on the above parameters, dynamic simulation models of the nose and main landing gear can be established separately. Input the weight, center of gravity, and inertia data into the mass parameters, and build the full aircraft model according to the installation position of the landing gear.

[0095] Step 3: Perform lift simulation on the full-scale landing simulation model to determine the vertical ground load of the aircraft landing gear.

[0096] Preferably, the vertical ground load of the aircraft landing gear is determined as follows:

[0097] Adjust the initial state of the aircraft before landing according to the test conditions, including the aircraft's heading engagement speed, descent speed, pitch angle, roll angle and yaw angle, etc.

[0098] The simulated lift force is applied at the center of gravity, equal in magnitude and opposite in direction to the gravity force;

[0099] By simulating a landing with added lift, the vertical ground loads on the nose landing gear and main landing gear are obtained. These load values ​​are simulation values ​​that simulate real landing conditions and will serve as the benchmark values ​​for comparison in drop simulations without lift.

[0100] Step 4: Extract the vertical ground load of the aircraft landing gear, perform a no-lift drop simulation on the full-aircraft landing simulation model, and determine the drop height iteratively based on the ground load.

[0101] Preferably, the specific method for determining the placement height is as follows:

[0102] Based on the above full-aircraft simulation model, lift was eliminated and a roughly appropriate drop height was set so that the aircraft would crash into the ground in a free-fall manner.

[0103] Extract the maximum ground load of the current landing gear. If the main landing gear touches the ground first, compare it with the vertical ground load of the main landing gear in step three; if the nose landing gear touches the ground first, compare it with the vertical ground load of the nose landing gear in step three.

[0104] If the maximum ground load is greater than the corresponding vertical ground load, the deployment height is reduced; if the maximum ground load is less than the corresponding vertical ground load, the deployment height is increased.

[0105] This process of iterating through the drop height is repeated until the error between the maximum ground load and the corresponding vertical ground load of the current landing gear is controlled within a certain range. Within this range, the drop height obtained at this point is the initial recommended drop height for the no-lift full-aircraft drop test.

[0106] Step 5: Calculate the sinking speed of the entire machine during the drop test based on the drop height.

[0107] Preferably, the method for calculating the sinking velocity during the full-scale drop test is as follows:

[0108] Substituting the drop height into the free fall formula yields the sinking speed of the aircraft landing gear tires when they touch down:

[0109] ;

[0110] in Let g be the sinking velocity, g be the acceleration due to gravity, and h be the drop height.

[0111] Considering the differences between full-aircraft dynamics simulation and drop tests, simulation results cannot be completely consistent with experimental results. In actual testing, it is still necessary to fine-tune the drop altitude appropriately to make the experimental results as close as possible to the simulation results of the maximum ground load in step three. The simulation results of the drop altitude can be used as the initial drop altitude for the full-aircraft drop test, which can prevent impact damage to the aircraft in the first drop test and reduce the number of times the drop altitude needs to be adjusted.

[0112] As another specific implementation, a system for determining the descent velocity of an aircraft under conditions of no lift and no mass reduction includes:

[0113] The simulation parameter determination module is used to determine the parameters required for simulating aircraft landing gear dynamics based on the test conditions.

[0114] The simulation model building module is used to determine the mechanical relationship of the landing gear based on the parameters required for simulation and to build a full-aircraft landing simulation model.

[0115] The ground load determination module is used to perform lift simulation on the full-aircraft landing simulation model to determine the vertical ground load of the aircraft landing gear.

[0116] The drop height determination module is used to extract the vertical ground load of the aircraft landing gear, perform a lift-free drop simulation on the full-aircraft landing simulation model, and iteratively determine the drop height based on the ground load.

[0117] The sinking speed determination module is used to calculate the sinking speed of the entire aircraft during the drop test based on the drop height.

[0118] Preferably, the mechanical relationship of the landing gear is as follows:

[0119] Total axial force of the hydropneumatic landing gear buffer Represented as:

[0120] ;

[0121] in For air spring force, For oil damping force, For internal friction, For structural constraint force;

[0122] Air spring force for:

[0123] ;

[0124] in For piston rod pressure area, The initial pressure of the air cavity, Let S be the initial volume of the air cavity, S be the buffer stroke, and n be the air variability index. Atmospheric pressure;

[0125] Oil damping force for:

[0126] ;

[0127] in Oil density, For piston rod oil pressure area, For oil orifice flow coefficient, Let v be the area of ​​the oil hole and v be the relative speed between the piston rod and the outer cylinder.

[0128] Internal friction for:

[0129] ;

[0130] in The equivalent coefficient of friction of the buffer;

[0131] Structural restraint force In the full-scale landing simulation model, it is treated as a spring with infinite stiffness.

[0132] Preferably, the vertical ground load of the aircraft landing gear is determined as follows:

[0133] Adjust the initial state of the aircraft before landing according to the test conditions, including the aircraft's heading engagement speed, descent speed, pitch angle, roll angle and yaw angle;

[0134] The simulated lift force is applied at the center of gravity, equal in magnitude and opposite in direction to the gravity force;

[0135] By simulating landing with added lift, the vertical ground loads of the nose landing gear and main landing gear are obtained.

[0136] Preferably, the specific method for determining the placement height is as follows:

[0137] Control the aircraft to crash into the ground in a free fall manner, extract the maximum ground load of the current landing gear, if the main landing gear touches the ground first, compare it with the vertical ground load of the main landing gear; if the nose landing gear touches the ground first, compare it with the vertical ground load of the nose landing gear.

[0138] If the maximum ground load is greater than the corresponding vertical ground load, the deployment height is reduced; if the maximum ground load is less than the corresponding vertical ground load, the deployment height is increased.

[0139] This process of iterating through the drop height is repeated until the error between the maximum ground load and the corresponding vertical ground load of the current landing gear is controlled within a certain range. Within.

[0140] Preferably, the method for calculating the sinking velocity during the full-scale drop test is as follows:

[0141] Substituting the drop height into the free fall formula yields the sinking speed of the aircraft landing gear tires when they touch down:

[0142] ;

[0143] in Let g be the sinking velocity, g be the acceleration due to gravity, and h be the drop height.

[0144] Preferably, the parameters required for simulating aircraft landing gear dynamics include the overall installation position, weight, center of gravity, moment of inertia, pitch angle, roll angle, yaw angle, sinking speed, and heading speed at landing.

[0145] In summary, this application has the following advantages:

[0146] This method not only saves on lift-simulation loading equipment but also fully considers the aircraft's initial drop attitude, including pitch, roll, and yaw angles. The determined sinking velocity and drop height can guide the initial drop test, reducing the risk of high overload from free-fall impact and minimizing the number of drop height adjustments. This method significantly improves the safety and operability of whole-aircraft drop tests and reduces the requirements for testing equipment.

[0147] As one specific implementation method, the following is an illustration using a concrete example:

[0148] Considering that the weight, center of gravity parameters, landing attitude, landing gear parameters, and installation positions of each aircraft type are different, and that establishing a dynamic simulation model is not the core task of this method, the detailed formula derivation and modeling process of "Step 1: Determine the parameters required for simulation based on the test conditions" and "Step 2: Determine the mechanical relationship of the landing gear and build a full-scale landing simulation model" are skipped in this example. Nevertheless, Step 1 and Step 2 are necessary steps for simulation analysis, and the modeling parameters must be correctly implemented according to the instructions. The specific implementation of this method will be explained below with simple and clear examples starting from Step 3.

[0149] Step 3: Determine the ground load on the aircraft landing gear through lift simulation.

[0150] Based on the full-aircraft dynamics simulation model built in steps one and two, if the aircraft pitch angle is set as... The roll angle is yaw angle is Therefore, it can be easily determined that the right main landing gear of the aircraft touches down first and has the greatest load. In this step, a simulated lift force perpendicular to the ground is applied at the aircraft's center of gravity, with a magnitude equal to the weight, and the corresponding initial downward sinking velocity is set according to the operating parameters. Since the lift force and gravity are balanced, the sinking velocity of the aircraft remains constant during descent, and the magnitude of the drop height does not affect the landing gear ground load. From the initial attitude of the aircraft, it can be seen that the left main landing gear touches down after the right main landing gear, and the nose landing gear touches down last. Under this condition, the right main landing gear with the greatest ground load is used as the comparison benchmark, and its load value will be used in the iterative process of subsequent steps. Time-load data similar to those shown in Table 1 can be obtained through simulated lift-drop-vibration simulation.

[0151] Table 1. Simulated load-time data for heave-drop vibration

[0152]

[0153] As can be seen from Table 1, the right main landing gear touches the ground after 0.3s, and the ground load reaches its maximum value at 0.6s. At this time, the maximum load value of 400kN is used as the benchmark value for the no-lift drop simulation.

[0154] Step 4: Conduct a drop-earthquake simulation without lift, and iterate the drop height according to the ground load.

[0155] Based on the simulation model in step three, lift is removed and the drop altitude is appropriately reduced while maintaining the same drop attitude. It is important to note that in this step, the aircraft is affected by gravitational acceleration, and the drop altitude directly affects the descent speed at landing gear touchdown. Allowing the aircraft to undergo free fall yields time-load data similar to those shown in Table 2.

[0156] Table 2. First Round of Free Fall Simulation Load-Time Data

[0157]

[0158] As can be seen from Table 2, the maximum load of 800kN in the first round of free fall simulation is significantly greater than the result of the lift-drop simulation, therefore the drop height needs to be reduced. After reducing the drop height, a free fall simulation was performed again, yielding time-load data similar to that shown in Table 3.

[0159] Table 3. Load-time data from the second round of free-fall simulation.

[0160]

[0161] Table 3 shows that the maximum load of the second round of free-fall simulation (340 kN) is less than that of the simulated heave-fall simulation, therefore the drop height needs to be increased. After increasing the drop height, the free-fall simulation is run again, and this process of adjusting the drop height is repeated until the error between the maximum ground load in the free-fall simulation and the maximum ground load in the simulated heave-fall simulation is controlled within a certain range. Within this range, the final time-load data is similar to that shown in Table 4.

[0162] Table 4. Final Iteration of Free Fall Simulation Load-Time Data

[0163]

[0164] Table 4 shows that the maximum load in the final wheel free-fall simulation was 399.7 kN, with an error of [missing value]. The drop height of 0.36m at this point is the initial recommended drop height for the drop test of the entire aircraft without lift and without shrinkage.

[0165] The iteration of the drop height in this step is the core of this method. The simplified table data provided is intended to illustrate the ground load comparison method and the adjustment approach for the drop height. In actual operation, the results of each round of free fall simulation may be too high or too low. Adjustments can be made repeatedly according to the above method based on the load conditions.

[0166] Step 5: Calculate the sinking speed of the entire machine in the drop test based on the drop height.

[0167] Substituting the drop height into formula (5) yields the sinking speed of the aircraft landing gear tires when they touch the ground. For example, with a drop height of 0.36m:

[0168] m / s

[0169] Therefore, the sinking velocity of the entire machine during the drop test can be calculated to be 2.66 m / s.

[0170] This example demonstrates that the proposed method is clear, concise, and easy to operate. On one hand, this method uses a computer to adjust the overall drop height, avoiding the risk of impact damage to the aircraft caused by large-scale adjustments in drop height during field testing. On the other hand, the proposed drop method, which involves no lift and no reduction in mass, is highly feasible and significantly reduces testing costs.

[0171] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for determining the descent velocity of an aircraft under conditions of no lift and no mass reduction, characterized in that, include: Determine the parameters required for simulating aircraft landing gear dynamics based on the test conditions; The mechanical relationship of the landing gear is determined based on the parameters required for simulation, and a full-scale landing simulation model is built. Lift simulation was performed on the full-scale landing simulation model to determine the vertical ground load on the aircraft landing gear. Extract the vertical ground load of the aircraft landing gear, perform a no-lift drop simulation on the full-aircraft landing simulation model, and determine the drop height iteratively based on the ground load; The sinking speed of the entire aircraft during the drop test was calculated based on the drop height.

2. The method for determining the aircraft sinking velocity under conditions of no lift and no mass reduction as described in claim 1, characterized in that, The mechanical relationship of the landing gear is as follows: Total axial force of the hydropneumatic landing gear buffer Represented as: ； in For air spring force, For oil damping force, For internal friction, For structural constraint force; Air spring force for: ； in For piston rod pressure area, The initial pressure of the air cavity, Let S be the initial volume of the air cavity, S be the buffer stroke, and n be the air variability index. Atmospheric pressure; Oil damping force for: ； in Oil density, For piston rod oil pressure area, For oil orifice flow coefficient, Let v be the area of ​​the oil hole and v be the relative speed between the piston rod and the outer cylinder. Internal friction for: ； in The equivalent coefficient of friction of the buffer; Structural restraint force In the full-scale landing simulation model, it is treated as a spring with infinite stiffness.

3. The method for determining the aircraft sinking velocity under conditions of no lift and no mass reduction as described in claim 1, characterized in that, Determine the vertical ground load of the aircraft landing gear, specifically: Adjust the initial state of the aircraft before landing according to the test conditions, including the aircraft's heading engagement speed, descent speed, pitch angle, roll angle and yaw angle; The simulated lift force is applied at the center of gravity, equal in magnitude and opposite in direction to the gravity force; By simulating landing with added lift, the vertical ground loads of the nose landing gear and main landing gear are obtained.

4. The method for determining the aircraft sinking velocity under conditions of no lift and no mass reduction as described in claim 3, characterized in that, The specific method for determining the placement height is as follows: Control the aircraft to crash into the ground in a free fall manner, extract the maximum ground load of the current landing gear, if the main landing gear touches the ground first, compare it with the vertical ground load of the main landing gear; if the nose landing gear touches the ground first, compare it with the vertical ground load of the nose landing gear. If the maximum ground load is greater than the corresponding vertical ground load, the deployment height is reduced; if the maximum ground load is less than the corresponding vertical ground load, the deployment height is increased. This process of iterating through the drop height is repeated until the error between the maximum ground load and the corresponding vertical ground load of the current landing gear is controlled within a certain range. Within.

5. The method for determining the aircraft sinking velocity under conditions of no lift and no mass reduction as described in claim 1, characterized in that, The calculation method for the sinking velocity during the full-scale drop test is as follows: Substituting the drop height into the free fall formula yields the sinking speed of the aircraft landing gear tires when they touch down: ； in Let g be the sinking velocity, g be the acceleration due to gravity, and h be the drop height.

6. The method for determining the aircraft sinking velocity under conditions of no lift and no mass reduction as described in claim 1, characterized in that, The parameters required for simulating aircraft landing gear dynamics include the overall installation position, weight, center of gravity, inertia, pitch angle, roll angle, yaw angle, sinking speed, and heading speed at landing.

7. A system for determining the descent velocity of an aircraft under conditions of no lift and no mass reduction, comprising the method described in any one of claims 1-6, characterized in that, include: The simulation parameter determination module is used to determine the parameters required for simulating aircraft landing gear dynamics based on the test conditions. The simulation model building module is used to determine the mechanical relationship of the landing gear based on the parameters required for simulation and to build a full-aircraft landing simulation model. The ground load determination module is used to perform lift simulation on the full-aircraft landing simulation model to determine the vertical ground load of the aircraft landing gear. The drop height determination module is used to extract the vertical ground load of the aircraft landing gear, perform a lift-free drop simulation on the full-aircraft landing simulation model, and iteratively determine the drop height based on the ground load. The sinking speed determination module is used to calculate the sinking speed of the entire aircraft during the drop test based on the drop height.

8. The system for determining the aircraft sinking velocity under conditions of no lift and no mass reduction as described in claim 7, characterized in that, The mechanical relationship of the landing gear is as follows: Total axial force of the hydropneumatic landing gear buffer Represented as: ； in For air spring force, For oil damping force, For internal friction, For structural constraint force; Air spring force for: ； in For piston rod pressure area, The initial pressure of the air cavity, Let S be the initial volume of the air cavity, S be the buffer stroke, and n be the air variability index. Atmospheric pressure; Oil damping force for: ； in Oil density, For piston rod oil pressure area, For oil orifice flow coefficient, Let v be the area of ​​the oil hole and v be the relative speed between the piston rod and the outer cylinder. Internal friction for: ； in The equivalent coefficient of friction of the buffer; Structural restraint force In the full-scale landing simulation model, it is treated as a spring with infinite stiffness.

9. The system for determining the aircraft sinking velocity under conditions of no lift and no mass reduction as described in claim 7, characterized in that, Determine the vertical ground load of the aircraft landing gear, specifically: Adjust the initial state of the aircraft before landing according to the test conditions, including the aircraft's heading engagement speed, descent speed, pitch angle, roll angle and yaw angle; The simulated lift force is applied at the center of gravity, equal in magnitude and opposite in direction to the gravity force; By simulating landing with added lift, the vertical ground loads of the nose landing gear and main landing gear are obtained.

10. The system for determining the aircraft sinking velocity under conditions of no lift and no mass reduction as described in claim 9, characterized in that, The specific method for determining the placement height is as follows: Control the aircraft to crash into the ground in a free fall manner, extract the maximum ground load of the current landing gear, if the main landing gear touches the ground first, compare it with the vertical ground load of the main landing gear; if the nose landing gear touches the ground first, compare it with the vertical ground load of the nose landing gear. If the maximum ground load is greater than the corresponding vertical ground load, the deployment height is reduced; if the maximum ground load is less than the corresponding vertical ground load, the deployment height is increased. This process of iterating through the drop height is repeated until the error between the maximum ground load and the corresponding vertical ground load of the current landing gear is controlled within a certain range. Within.

11. The system for determining the aircraft sinking velocity under conditions of no lift and no mass reduction as described in claim 7, characterized in that, The calculation method for the sinking velocity during the full-scale drop test is as follows: Substituting the drop height into the free fall formula yields the sinking speed of the aircraft landing gear tires when they touch down: ； in Let g be the sinking velocity, g be the acceleration due to gravity, and h be the drop height.

12. The system for determining the aircraft sinking velocity under conditions of no lift and no mass reduction as described in claim 7, characterized in that, The parameters required for simulating aircraft landing gear dynamics include the overall installation position, weight, center of gravity, inertia, pitch angle, roll angle, yaw angle, sinking speed, and heading speed at landing.

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