Performance joint simulation method for multiple landing gears of helicopter

Abstract

The invention discloses a performance joint simulation method for multiple landing gears of a helicopter, which comprises the following steps of: 1, establishing a dynamic equilibrium equation of a helicopter body by taking a helicopter body coordinate system as a reference and calculating coordinates of stress points on the helicopter body; 2, calculating numerical values of various forces in the dynamic equilibrium equation obtained in the step 1; and step 3, giving an input quantity for the constructed dynamic balance equation, and carrying out iterative calculation to complete the calculation of the drop performance of the whole aircraft or obtain a motion data result of the aircraft in each direction. According to the technical scheme provided by the invention, the fuselage is taken as a rigid body, the landing load and the work quantity of the fuselage under the conditions of different weight gravity center states, different postures and different landing speeds are solved through the dynamic balance equation so as to obtain the drop performance data of the undercarriage, and the taxiing response of the corresponding road surface is obtained after the road spectrum is input.

Description

Technical Field

[0001] The present invention relates to the field of but not limited to the technical field of aviation structure design, and in particular to a performance joint simulation method for multiple landing gears of a helicopter. Background Art

[0002] Landing gear performance calculation is the core technology of landing gear design. The landing gear load and center of gravity overload in the performance calculation results directly affect the helicopter structural design parameters. The landing gear energy absorption work in the results directly determines whether the landing gear meets the design requirements and directly determines whether the occupants can land safely. In the landing gear performance calculation, establishing a correct calculation model is the key and basis for accurate calculation results.

[0003] The existing method for calculating the cushioning performance of helicopter landing gear is to load a reduced mass at each landing gear installation position, and the reduced mass must make the vertical acceleration of its installation point equal to the vertical acceleration of the current stress state of the entire machine. The subsequent drop test is carried out by changing the drop mass under each working condition to match the drop work with the work of each working condition obtained in the performance calculation. This simplified algorithm is fast to calculate and relatively simple to verify by test. It is a standard practice in landing gear drop performance calculation and test verification. However, when the above algorithm is used for computer wheel contact point height differences or for conditions such as two-point landing and maximum nose-up landing, since each landing gear is calculated independently, it is impossible to consider the energy transfer caused by changes in posture such as fuselage pitch, and there is a risk that the calculation results will be significantly different from the actual situation. Summary of the invention

[0004] The purpose of the present invention is: in order to solve the above-mentioned problem, an embodiment of the present invention provides a performance joint simulation method for multiple landing gear of a helicopter, so as to solve the problem that the existing method of calculating the buffer performance of helicopter landing gear has differences in the heights of the computer wheel contact points or for conditions such as two-point landing and maximum nose-up landing, the energy transfer caused by posture changes such as fuselage pitch cannot be considered, resulting in a large difference between the calculation result and the actual situation.

[0005] The technical solution of the present invention is as follows: The embodiment of the present invention provides a performance joint simulation method for multiple landing gears of a helicopter, comprising:

[0006] Step 1, using the body coordinate system as a reference, by calculating the coordinates of each force point on the body, the dynamic equilibrium equation of the body is established;

[0007] Step 2, calculating the values ​​of various forces in the dynamic equilibrium equation obtained in step 1;

[0008] Step 3: Given the input quantity for the constructed dynamic balance equation, and iterative calculation is performed to complete the drop shock performance calculation of the whole aircraft and obtain the data results of the various directions of the aircraft body;

[0009] Among them, in the performance joint simulation method, the fuselage is regarded as a rigid body, and the landing load and work of the fuselage under different weight center of gravity states, different attitudes, and different landing speeds are solved through the dynamic equilibrium equation to obtain the landing gear drop shock performance data, and the taxiing response of the corresponding pavement is obtained after the road spectrum is input.

[0010] Optionally, in the above-mentioned joint simulation method for the performance of helicopter multiple landing gears, the force points in step 1 include: each landing gear installation point, the center point of the main rotor, the center point of the tail rotor, and the center of gravity of the fuselage;

[0011] The step 1 of establishing the dynamic equilibrium equation of the body includes:

[0012] Project the external forces on each force point onto the body coordinate system, regard the body structure as a rigid body, and establish the body's dynamic equilibrium equation, including: the body's three-axis force dynamic equilibrium equation, and the body's three-axis moment dynamic equilibrium equation;

[0013] By analyzing the unsprung mass of each landing gear, the dynamic equilibrium equation of the unsprung mass of each landing gear is established.

[0014] Optionally, in the above-mentioned performance joint simulation method for helicopter multiple landing gears, the dynamic equilibrium equations established in step 1 include:

[0015] The dynamic equilibrium equation of the three-axis force of the body is:

[0016]

[0017] The dynamic equilibrium equation of the three-axis moment of the body is:

[0018]

[0019] In step 1, by analyzing the unsprung mass of each landing gear, the buffer is equivalent to a spring and a damper in parallel, and the wheel is equivalent to a spring, and the dynamic equilibrium equation of the unsprung mass of each landing gear is established as follows:

[0020]

[0021] Where m is the overall mass of the machine, [F xi ,F yi ,F zi ] T is the force of the landing gear in each direction, [0,0,mg] T is the gravity acting on the body structure, [F zjx , F zjy , F zjz ] T The three-point force applied by the main propeller to the body, [Fwjx , F wjy , F wjz ] T It is the three-point force applied by the tail rotor to the fuselage;

[0022] I is the body moment of inertia matrix, R is the distance matrix from each landing gear installation point to the body center of gravity, R zj is the coordinate of the main propeller point in the body coordinate system, R wj is the coordinate of the tail rotor in the body coordinate system, [M zjx , M zjy , M zjz ] T is the axial torque of the main propeller, [M wjx , M wjy , M wjz ] T is the axial torque of the tail rotor;

[0023] P jli is the wheel vertical force, m ki g is the weight of the undercarriage unsprung mass, F zi is the buffer load, F xi is the heading load transmitted through the buffer, F yi is the lateral load transmitted through the buffer; for the symmetrical landing condition F yi =0;σ i is the height of each wheel center point above the ground, and i represents the landing gear number.

[0024] Optionally, in the above-mentioned method for joint simulation of performance of helicopter multiple landing gears, step 2 comprises:

[0025] Step 21, calculate the wheel vertical force P jli , the wheel vertical force P jli By σ i -R0+σ di Sure:

[0026] Taking R0 as the tire unloaded radius, the wheel vertical force P jli The calculation method is:

[0027] If σ i -R0 is greater than 0, the tire is not touching the ground, P jli =0;

[0028] If σ i -R0 is less than 0, then the static pressure curve is established by P jli With σ i -R0, and then interpolate to get P jli ;

[0029] For the uneven road surface taxiing process, by adding the ground height σdi As a correction, it is possible to calculate the helicopter's rolling response on an uneven road surface.

[0030] Optionally, in the above-mentioned performance joint simulation method for helicopter multiple landing gears, step 2 further comprises:

[0031] Step 22, calculate the buffer load F zi ; The buffer load F zi Composed of three parts, step 22 includes:

[0032] Step 22a, calculate the buffer air cavity force as:

[0033]

[0034] Where p0 is the initial inflation pressure of the air cavity, F k is the exhaust area, V0 is the air cavity volume, SH is the buffer compression, and n is the gas polytropic index;

[0035] Step 22b, calculate the buffer oil damping force as:

[0036]

[0037] Where ρ is the density of hydraulic oil, F y is the oil pressure area, C d is the oil damping coefficient, f is the oil hole area, and dSH is the buffer compression speed;

[0038] Step 22c, calculate the buffer friction:

[0039] P m =k m P kq ;

[0040] Among them, k m is the friction coefficient, P kq For the air cavity force.

[0041] Optionally, in the above-mentioned helicopter multi-landing gear performance joint simulation method, the buffer friction force is calculated in step 22c as follows:

[0042] The Dahl friction model is used for calculation, and the Dahl friction model is:

[0043]

[0044] Among them, v is the relative velocity, σ is the stiffness coefficient, and the α parameter determines the shape of the curve. The larger α is, the greater the curvature of the curve of the Dahl friction model is;

[0045] The friction force of the buffer is calculated as:

[0046]

[0047] Get the buffer load F zi for:

[0048] F zi =P kq +sign(dSH)(P y +P m ).

[0049] Optionally, in the above-mentioned performance joint simulation method for helicopter multiple landing gears, the iterative calculation in step 3 includes:

[0050] Step 31, after the basic parameters of the constructed dynamic equilibrium equations are determined, the time history of the main propeller force and the tail propeller force are input, and after the initial state of the fuselage is determined, the force applied to the fuselage by each landing gear is solved in step 2;

[0051] Step 32, substituting the calculation result of the previous step into the dynamic equilibrium equation of step 1 to obtain the acceleration, velocity and displacement of the six degrees of freedom of the body;

[0052] Step 33, the compression amount, load and work of each landing gear at the next moment can be obtained through the calculation results of the previous step, and then the force applied to the aircraft body by each landing gear is solved again through step 2;

[0053] Repeat steps 32 and 33 to perform iterative calculation.

[0054] Optionally, in the above-mentioned performance joint simulation method for helicopter multiple landing gears, the termination method of the iterative calculation in step 3 includes:

[0055] When the drop shock energy is dissipated by the oil damping force and friction force, the compression of each buffer no longer changes, and the calculation of the drop shock performance of the whole machine at this weight state is completed; or,

[0056] The helicopter ground taxiing simulation is completed using the dynamic equilibrium equation within the specified time to obtain the data results of the various directional motion of the aircraft.

[0057] The beneficial effects of the present invention are as follows: the embodiment of the present invention provides a performance joint simulation method for multiple landing gears of a helicopter. By analyzing the force of the body, taking the body coordinate system as a reference, and calculating the coordinates of each force point on the body, the dynamic equilibrium equation of the body is established; the values ​​of each force in the established dynamic equilibrium equation are calculated; for the constructed dynamic equilibrium equation, the input quantity is given, and iterative calculation is performed to obtain the data results of the body's directional motion. Using the performance joint simulation method provided by the embodiment of the present invention, on the one hand, rigid body dynamics are used to perform body dynamics analysis, and load calculations of multiple landing gears can be performed simultaneously. Compared with the traditional mass reduction algorithm, such a calculation method can better simulate the landing gear's drop shock work curve under the conditions of asymmetric landing and different landing gear stiffness; on the other hand, the dynamic equilibrium equation constructed by the present invention can be used to calculate the drop shock performance. By applying different road spectra to each wheel, it can also be used to calculate the response of the whole machine to the road spectrum. The technical solution provided by the embodiment of the present invention has the following beneficial effects:

[0058] First, each landing gear has two independent degrees of freedom: the compression of the buffer and the compression of the wheel. The buffer can only be activated when the force transmitted by the lower mass exceeds the activation force of the buffer, successfully simulating the effect of static friction.

[0059] Second, the dynamic equilibrium equation constructed by the present invention regards the fuselage as a rigid body and simplifies the forces of each landing gear into three-dimensional forces acting on the landing gear mounting point, which not only omits the process of reducing the mass equivalent calculation of the whole machine mass, but also theoretically this algorithm can better simulate the response of the whole machine under various working conditions;

[0060] Third, after limiting the rotational freedom of the aircraft, the weight states of the model under the three-point horizontal landing condition are consistent with the results of the traditional algorithm, so the calculation results of the dynamic balance equation can be considered reliable;

[0061] Fourth, fast calculation: due to the smooth transition of friction force, the difficulty of nonlinear mechanical calculation is alleviated;

[0062] Fifth, it has a wide range of applications: it can calculate the drop shock performance of the entire aircraft under all working conditions and the ground taxiing response of helicopters. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] The accompanying drawings are used to provide a further understanding of the technical solution of the present invention and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the technical solution of the present invention and do not constitute a limitation on the technical solution of the present invention.

[0064] Figure 1 A schematic diagram of the forces acting on the helicopter body in the performance joint simulation method for multiple landing gears of a helicopter provided in an embodiment of the present invention;

[0065] Figure 2 is the Coulomb friction model;

[0066] Figure 3 It is a curve diagram of Dahl friction model when α=1;

[0067] Figure 4 The calculation results of the simulation example using the performance joint simulation method of the helicopter multiple landing gear provided by the embodiment of the present invention; Figure 4 Figure a is a local diagram of the vertical load on the front tire, and figure b is a local diagram of the vertical load on the main tire. DETAILED DESCRIPTION

[0068] The accompanying drawings are used to provide a further understanding of the technical solution of the present invention and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the technical solution of the present invention and do not constitute a limitation on the technical solution of the present invention.

[0069] The above background technology has already explained the importance of landing gear performance calculation in landing gear design. However, the existing helicopter landing gear buffer performance calculation method has the following problems:

[0070] First, there is a risk that the calculated wheel touchdown point height is different from the actual situation, or for conditions such as two-point landing and maximum nose-up landing, the energy transfer caused by the change of the fuselage pitch attitude cannot be considered, resulting in a large difference between the calculated result and the actual situation.

[0071] Second, in traditional landing gear performance calculations, the presence of friction makes the mechanical model incoherent, resulting in singularities in the dynamics calculations;

[0072] Third, the existing calculation model cannot be used for calculating driving on uneven roads, and the model is less universal.

[0073] In order to solve the above three problems, the present invention proposes a performance joint simulation method for multiple landing gears of helicopters. By constructing a coherent landing gear dynamics model and treating the fuselage as a rigid body, the landing load and work of the fuselage under different weight center of gravity states and different attitudes and landing speed conditions are solved through dynamic balance, so as to obtain more accurate landing gear drop shock performance data and obtain the taxiing response of this pavement after inputting the road spectrum.

[0074] The present invention provides the following specific embodiments which can be combined with each other. The same or similar concepts or processes may not be described in detail in some embodiments.

[0075] The embodiment of the present invention provides a performance joint simulation method for multiple landing gears of a helicopter, comprising the following steps:

[0076] Step 1, using the body coordinate system as a reference, by calculating the coordinates of each force point on the body, the dynamic equilibrium equation of the body is established;

[0077] Step 2, calculating the values ​​of various forces in the dynamic equilibrium equation obtained in step 1;

[0078] Step 3: Given the input quantity for the constructed dynamic balance equation, and iterative calculation is performed to complete the drop shock performance calculation of the whole aircraft and obtain the data results of the various directions of the aircraft body;

[0079] Among them, in the performance joint simulation method, the fuselage is regarded as a rigid body, and the landing load and work of the fuselage under different weight center of gravity states, different attitudes, and different landing speeds are solved through the dynamic equilibrium equation to obtain the landing gear drop shock performance data, and the taxiing response of the corresponding pavement is obtained after the road spectrum is input.

[0080] In one implementation of the embodiment of the present invention, Figure 1 The figure is a schematic diagram of the body force in the performance joint simulation method of helicopter multiple landing gears provided by an embodiment of the present invention. The force points in the above step 1 include: each landing gear installation point, the main rotor center point, the tail rotor center point, and the body gravity center point.

[0081] In this implementation, the dynamic equilibrium equation of the body is established in step 1, including:

[0082] The external forces on each stress point are projected onto the body coordinate system, the body structure is regarded as a rigid body, and the body's dynamic equilibrium equations are established, including: the body's three-axis force dynamic equilibrium equations, and the body's three-axis moment dynamic equilibrium equations.

[0083] The dynamic equilibrium equation of the three-axis force of the body is:

[0084]

[0085] The dynamic equilibrium equation of the three-axis moment of the body is:

[0086]

[0087] Where m is the overall mass of the machine, [F xi ,F yi ,F zi ] T is the force of the landing gear in each direction, [0,0,mg] T is the gravity acting on the body structure, [F zjx , F zjy , F zjz ] T The three-point force applied by the main propeller to the aircraft body, [F wjx , F wjy , Fwjz ] T It is the three-point force applied by the tail rotor to the fuselage;

[0088] I is the body moment of inertia matrix, R is the distance matrix from each landing gear installation point to the body center of gravity, R zj is the coordinate of the main propeller point in the body coordinate system, R wj is the coordinate of the tail rotor in the body coordinate system, [M zjx , M zjy , M zjz ] T is the axial torque of the main propeller, [M wjx , M wjy , M wjz ] T is the anisotropic torque of the tail rotor.

[0089] By analyzing the unsprung mass of each landing gear, the buffer is equivalent to a parallel spring and damper, and the wheel is equivalent to a spring. The dynamic equilibrium equation of the unsprung mass of each landing gear is established as follows:

[0090]

[0091] Among them, P jli is the wheel vertical force, m ki g is the weight of the undercarriage unsprung mass, F zi is the buffer load, F xi F is the heading load transmitted through the buffer, which reacts as a rebound load during the rolling landing. yi is the lateral load transmitted through the buffer; for the symmetrical landing condition F yi =0;σ i is the height of each wheel center point above the ground, and i represents the landing gear number.

[0092] For each dynamic equilibrium equation obtained in the above implementation, the calculation of the values ​​of each force in the dynamic equilibrium equation obtained in step 1 in step 2 includes the following calculations:

[0093] Step 21, calculate the wheel vertical force P jli , the wheel vertical force P jli By σ i -R0+σ di Sure:

[0094] Taking R0 as the tire unloaded radius, the wheel vertical force P jli The calculation method is:

[0095] If σ i -R0 is greater than 0, the tire is not touching the ground, P jli =0;

[0096] If σ i -R0 is less than 0, then the static pressure curve is established by P jli With σ i -R0, and then interpolate to get P jli ;

[0097] For the uneven road surface taxiing process, by adding the ground height σ di As a correction, it is possible to calculate the helicopter's rolling response on an uneven road surface.

[0098] Step 22, calculate the buffer load F zi ; The buffer load F zi It consists of the following three parts, and the calculation methods of the three parts are as follows:

[0099] (a) Buffer air cavity force:

[0100]

[0101] Where p0 is the initial inflation pressure of the air cavity, F k is the exhaust area, V0 is the air cavity volume, SH is the buffer compression, and n is the gas polytropic index;

[0102] (b) Buffer oil damping force:

[0103]

[0104] Where ρ is the density of hydraulic oil, F y is the oil pressure area, C d is the oil damping coefficient, f is the oil hole area, and dSH is the buffer compression speed.

[0105] (c) Buffer friction:

[0106] P m =k m P kq ;

[0107] Among them, k m is the friction coefficient, P kq For the air cavity force.

[0108] It should be noted that in traditional calculations, it is judged when the compression speed of the buffer reaches 0, but it is difficult to find the speed 0 point in numerical calculations. Therefore, by adding a speed threshold, it is assumed that the buffer completes the energy absorption of the positive stroke within this range and starts to move in the reverse direction, that is, the buffer is in a static friction state at this moment. However, this algorithm brings the following problems:

[0109] Question 1: Figure 2In the Coulomb friction model shown, static friction is distributed on the axis with v = 0 and changes with the external force input; during the calculation process, it is difficult to calculate static friction;

[0110] Problem 2: Friction force jumps at the speed threshold boundary, causing the buffer to restart at the boundary and other non-convergence problems.

[0111] To solve the above problems, the Dahl friction model is adopted in the embodiment of the present invention, namely:

[0112]

[0113] Among them, v is the relative velocity, σ is the stiffness coefficient, and the α parameter determines the shape of the curve. The larger α is, the greater the curvature of the curve. When α = 1, Figure 3 The Dahl friction model is shown. From this, the friction force of the buffer can be obtained as:

[0114]

[0115] The Dahl friction model is used in the embodiment of the present invention to avoid the problem that the static friction calculated by the Coulomb friction model makes the mechanical model incoherent, thereby causing singularities in the dynamics calculation and further causing the model calculation to terminate.

[0116] The buffer load F is obtained by comprehensive calculation. zi for:

[0117] F zi =P kq +sign(dSH)(P y +P m ).

[0118] In an implementation of the embodiment of the present invention, the implementation of the above step 3 may include:

[0119] After the basic parameters of the constructed dynamic equilibrium equations are determined, the time history of the main rotor force and the tail rotor force are input. After the initial state of the fuselage is determined, the forces applied to the fuselage by each landing gear can be solved in step 2.

[0120] Substitute the calculation results of the previous step into the dynamic equilibrium equation of step 1 to obtain the acceleration, velocity, and displacement of the six degrees of freedom of the body;

[0121] The calculation results of the previous step can be used to obtain the compression amount, load and work of each landing gear at the next moment, and then the force applied to the aircraft by each landing gear can be solved again in step 2;

[0122] Substitute the result calculated in the previous step into the dynamic equilibrium equation of step 1, and use the Runge-Kutta method to obtain the acceleration, velocity, and displacement of the six degrees of freedom of the body at the next moment; and iterate.

[0123] Finally, after the drop shock energy at a certain position is dissipated by the oil damping force and friction force, the compression amount of each buffer no longer changes, and the drop shock performance calculation of the whole aircraft at this weight state is completed; or the dynamic equilibrium equation is used to complete the helicopter ground taxiing simulation within the specified time to obtain the data results of the various directions of the aircraft motion.

[0124] The embodiment of the present invention provides a performance joint simulation method for multiple landing gears of a helicopter. Through the force analysis of the body, the coordinate system of the body is used as a reference, and the coordinates of each force point on the body are calculated to establish the dynamic balance equation of the body; the values ​​of each force in the established dynamic balance equation are calculated; for the constructed dynamic balance equation, the input quantity is given, and iterative calculation is performed to obtain the data results of the body's directional motion. Using the performance joint simulation method provided by the embodiment of the present invention, on the one hand, rigid body dynamics are used to perform body dynamics analysis, and the load calculation of multiple landing gears can be performed simultaneously. Compared with the traditional mass reduction algorithm, this calculation method can better simulate the landing gear under the conditions of asymmetric landing, different landing gear stiffness, etc. The drop shock work curve; on the other hand, the dynamic balance equation constructed by the present invention can be used to calculate the drop shock performance. By applying different road spectra to each wheel, it can also be used to calculate the response of the whole machine to the road spectrum. The technical solution provided by the embodiment of the present invention has the following beneficial effects:

[0125] First, each landing gear has two independent degrees of freedom: the compression of the buffer and the compression of the wheel. The buffer can only be activated when the force transmitted by the lower mass exceeds the activation force of the buffer, successfully simulating the effect of static friction.

[0126] Second, the dynamic equilibrium equation constructed by the present invention regards the fuselage as a rigid body and simplifies the forces of each landing gear into three-dimensional forces acting on the landing gear mounting point, which not only omits the process of reducing the mass equivalent calculation of the whole machine mass, but also theoretically this algorithm can better simulate the response of the whole machine under various working conditions;

[0127] Third, after limiting the rotational freedom of the aircraft, the weight states of the model under the three-point horizontal landing condition are consistent with the results of the traditional algorithm, so the calculation results of the dynamic equilibrium equation can be considered reliable;

[0128] Fourth, fast calculation: due to the smooth transition of friction force, the difficulty of nonlinear mechanical calculation is alleviated;

[0129] Fifth, it has a wide range of applications: it can calculate the drop shock performance of the entire aircraft under all working conditions and the ground taxiing response of helicopters.

[0130] The following is a simulation example of the performance joint simulation method for multiple landing gear of a helicopter provided in an embodiment of the present invention.

[0131]

[0132]

[0133] like Figure 4 , which is the calculation result of a simulation example using the performance joint simulation method for helicopter multiple landing gears provided by an embodiment of the present invention; Figure 4 Figure a is a local diagram of the vertical load on the front tire, and figure b is a local diagram of the vertical load on the main tire.

[0134] Although the embodiments disclosed in the present invention are as above, the contents are only embodiments adopted to facilitate understanding of the present invention and are not intended to limit the present invention. Any technician in the field to which the present invention belongs can make any modifications and changes in the form and details of implementation without departing from the spirit and scope disclosed in the present invention, but the patent protection scope of the present invention shall still be subject to the scope defined in the attached claims.

Claims

1. A performance joint simulation method for multiple landing gears of a helicopter, characterized in that: include: Step 1, using the body coordinate system as a reference, by calculating the coordinates of each force point on the body, the dynamic equilibrium equation of the body is established; Step 2, calculating the values ​​of various forces in the dynamic equilibrium equation obtained in step 1; Step 3: Given the input quantity for the constructed dynamic balance equation, and iterative calculation is performed to complete the drop shock performance calculation of the whole aircraft and obtain the data results of the various directions of the aircraft body; Among them, in the performance joint simulation method, the fuselage is regarded as a rigid body, and the landing load and work of the fuselage under different weight center of gravity states, different attitudes, and different landing speeds are solved through the dynamic equilibrium equation to obtain the landing gear drop shock performance data, and the taxiing response of the corresponding pavement is obtained after the road spectrum is input.

2. The performance joint simulation method of helicopter multiple landing gear according to claim 1 is characterized in that: The stress points in step 1 include: each landing gear mounting point, the center point of the main rotor, the center point of the tail rotor, and the center of gravity of the fuselage; The step 1 of establishing the dynamic equilibrium equation of the body includes: Project the external forces on each force point onto the body coordinate system, regard the body structure as a rigid body, and establish the body's dynamic equilibrium equation, including: the body's three-axis force dynamic equilibrium equation, and the body's three-axis moment dynamic equilibrium equation; By analyzing the unsprung mass of each landing gear, the dynamic equilibrium equation of the unsprung mass of each landing gear is established.

3. The performance joint simulation method of helicopter multiple landing gear according to claim 2 is characterized in that: The kinetic equilibrium equations established in step 1 include: The dynamic equilibrium equation of the three-axis force of the body is: The dynamic equilibrium equation of the three-axis moment of the body is: In step 1, by analyzing the unsprung mass of each landing gear, the buffer is equivalent to a spring and a damper in parallel, and the wheel is equivalent to a spring, and the dynamic equilibrium equation of the unsprung mass of each landing gear is established as follows: Where m is the overall mass of the machine, [F xi ,F yi ,F zi ] T is the force of the landing gear in each direction, [0,0,mg] T is the gravity acting on the body structure, [F zjx , F zjy , F zjz ] T The three-point force applied by the main propeller to the body, [F wjx , F wjy , F wjz ] T It is the three-point force applied by the tail rotor to the fuselage; I is the body moment of inertia matrix, R is the distance matrix from each landing gear installation point to the body center of gravity, R zj R is the coordinate of the main propeller point in the body coordinate system, wj is the coordinate of the tail rotor in the body coordinate system, [M zjx , M zjy , M zjz ] T is the axial torque of the main propeller, [M wjx , M wjy , M wjz ] T is the axial torque of the tail rotor; P jli is the wheel vertical force, m ki g is the weight of the undercarriage unsprung mass, F zi is the buffer load, F xi is the heading load transmitted through the buffer, F yi is the lateral load transmitted through the buffer; for the symmetrical landing condition F yi =0;σ i is the height of each wheel center point above the ground, and i represents the landing gear number.

4. The performance joint simulation method for multiple landing gears of a helicopter according to claim 3, characterized in that: The step 2 comprises: Step 21, calculate the wheel vertical force P jli , the wheel vertical force P jli By σ i -R0+σ di Sure: Taking R0 as the tire unloaded radius, the wheel vertical force P jli The calculation method is: If σ i -R0 is greater than 0, the tire is not touching the ground, P jli =0; If σ i -R0 is less than 0, then the static pressure curve is established by P jli With σ i -R0, and then interpolate to get P jli ; For the uneven road surface taxiing process, by adding the ground height σ di As a correction, it is possible to calculate the helicopter's rolling response on an uneven road surface.

5. The performance joint simulation method for multiple landing gear of a helicopter according to claim 4, characterized in that: The step 2 also includes: Step 22, calculate the buffer load F zi ; The buffer load F zi Composed of three parts, step 22 includes: Step 22a, calculate the buffer air cavity force as: Where p0 is the initial inflation pressure of the air cavity, F k is the exhaust area, V0 is the air cavity volume, SH is the buffer compression, and n is the gas polytropic index; Step 22b, calculate the buffer oil damping force as: Where ρ is the density of hydraulic oil, F y is the oil pressure area, C d is the oil damping coefficient, f is the oil hole area, and dSH is the buffer compression speed; Step 22c, calculate the buffer friction: P m =k m P kq ; Among them, k m is the friction coefficient, P kq For the air cavity force.

6. The performance joint simulation method for multiple landing gear of a helicopter according to claim 5, characterized in that: The method for calculating the friction force of the buffer in step 22c is: The Dahl friction model is used for calculation, and the Dahl friction model is: Among them, v is the relative velocity, σ is the stiffness coefficient, and the α parameter determines the shape of the curve. The larger α is, the greater the curvature of the curve of the Dahl friction model is; The friction force of the buffer is calculated as: Get the buffer load F zi for: F zi =P kq +sign(dSH)(P y +P m )。 7. The performance joint simulation method for multiple landing gear of a helicopter according to claim 6, characterized in that: The iterative calculation in step 3 includes: Step 31, after the basic parameters of the constructed dynamic equilibrium equations are determined, the time history of the main propeller force and the tail propeller force are input, and after the initial state of the fuselage is determined, the force applied to the fuselage by each landing gear is solved in step 2; Step 32, substituting the calculation result of the previous step into the dynamic equilibrium equation of step 1 to obtain the acceleration, velocity and displacement of the six degrees of freedom of the body; Step 33, the compression amount, load and work of each landing gear at the next moment can be obtained through the calculation results of the previous step, and then the force applied to the aircraft body by each landing gear is solved again through step 2; Repeat steps 32 and 33 to perform iterative calculation.

8. The performance joint simulation method for multiple landing gears of a helicopter according to claim 7, characterized in that: The termination method of the iterative calculation in step 3 includes: When the drop shock energy is dissipated by the oil damping force and friction force, the compression of each buffer no longer changes, and the calculation of the drop shock performance of the whole machine at this weight state is completed; or, The helicopter ground taxiing simulation is completed using the dynamic equilibrium equation within the specified time to obtain the data results of the various directional motion of the aircraft.

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