Helicopter landing gear landing load measurement method

Abstract

The application provides a helicopter landing gear landing load measurement method, the method comprises the following steps: pasting at least 10 strain gauges at the wheel shaft position; obtaining the tensile strain, shear strain, bending strain and torsional strain of the strain gauges; determining the heading load, lateral load and / or vertical load when the helicopter landing gear lands based on the tensile strain, shear strain, bending strain and torsional strain of the strain gauges; the application realizes the analysis and calculation of the transmission of the three-directional ground loads to the landing gear wheel shaft during the landing of the helicopter, the reverse derivation process of strain to load is supplemented by the forward derivation of traditional load to strain, the interference of the nonlinear superposition of combined loads on the solution of ground load calculation is eliminated, the position requirement that the strain gauge layout needs to meet the unidirectional load sensitivity is reduced, and good universality is achieved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of sensor measurement, and particularly relates to a landing load measurement method for a helicopter landing gear. BACKGROUND

[0002] During the take-off and landing of a helicopter, the landing gear as a direct bearing mechanism bears the ground heading load, the lateral load and the vertical load. Due to the influence of the ground state, environmental factors and landing attitude changes, the load bearing and load transmission of the landing gear are complex and changeable. The existing strain measurement method is only good for responding to a certain load after bridge lapping, and it is difficult to qualitatively analyze the load bearing structure under the condition of actually bearing complex combined loads. The strain superposition caused by the adverse load is difficult to eliminate, and the load measurement result is difficult to qualitatively analyze.

[0003] The actual landing load measurement is directly related to the structure design and expected performance evaluation of key components such as the bumper, the swing arm anti-sway device and the brake device. Compared with the theoretical calculation and the drop test result, the actual landing load measurement can truly reflect the combined form and distribution state of the ground load, and is of great significance to the structure design and fatigue life determination of the landing gear. SUMMARY

[0004] In view of the above technical problems, the application provides a landing load measurement method for a helicopter landing gear, which comprises the following steps:

[0005] At least 10 strain gauges are pasted at the wheel shaft position;

[0006] The tensile strain, the shear strain, the bending strain and the torsional strain of the strain gauges are obtained;

[0007] The heading load, the lateral load and / or the vertical load during the landing of the helicopter landing gear are determined based on the tensile strain, the shear strain, the bending strain and the torsional strain of the strain gauges.

[0008] Preferably, the strain gauges comprise a ninth strain gauge, a tenth strain gauge, an eleventh strain gauge and a twelfth strain gauge; and the determination of the heading load during the landing of the helicopter landing gear based on the tensile strain, the shear strain, the bending strain and the torsional strain of the strain gauges comprises the following steps:

[0009] The tensile strain, the shear strain, the bending strain and the torsional strain of the ninth strain gauge, the tenth strain gauge, the eleventh strain gauge and the twelfth strain gauge are obtained;

[0010] The strain state of the ninth strain gauge, the strain state of the tenth strain gauge, the strain state of the eleventh strain gauge and the strain state of the twelfth strain gauge are determined based on the tensile strain, the shear strain, the bending strain and the torsional strain of the ninth strain gauge, the tenth strain gauge, the eleventh strain gauge and the twelfth strain gauge;

[0011] determine the torque corresponding to the torsion strain based on the strain state of the ninth strain gauge, the strain state of the tenth strain gauge, the strain state of the eleventh strain gauge and the strain state of the twelfth strain gauge;

[0012] obtain the heading load based on the torque corresponding to the torsion strain.

[0013] Preferably, the ninth strain gauge, the tenth strain gauge, the eleventh strain gauge and the twelfth strain gauge are connected in a full-bridge manner.

[0014] Preferably, the connecting line of the ninth strain gauge and the twelfth strain gauge is perpendicular to the connecting line of the tenth strain gauge and the eleventh strain gauge; wherein the angle between the connecting line and the heading is 45°.

[0015] Preferably, the strain gauge includes a fifth strain gauge, a sixth strain gauge, a seventh strain gauge and an eighth strain gauge; and the determination of the lateral load when the helicopter landing gear lands based on the tensile-compressive strain, the shear strain, the bending strain and the torsion strain of the strain gauge includes:

[0016] obtain the tensile-compressive strain, the shear strain, the bending strain and the torsion strain of the fifth strain gauge, the sixth strain gauge, the seventh strain gauge and the eighth strain gauge;

[0017] determine the strain state of the fifth strain gauge, the strain state of the sixth strain gauge, the strain state of the seventh strain gauge and the strain state of the eighth strain gauge based on the tensile-compressive strain, the shear strain, the bending strain and the torsion strain of the fifth strain gauge, the sixth strain gauge, the seventh strain gauge and the eighth strain gauge;

[0018] determine the tensile-compressive force corresponding to the tensile-compressive strain based on the strain state of the fifth strain gauge, the strain state of the sixth strain gauge, the strain state of the seventh strain gauge and the strain state of the eighth strain gauge;

[0019] obtain the lateral load based on the tensile-compressive force corresponding to the tensile-compressive strain.

[0020] Preferably, the fifth strain gauge and the sixth strain gauge are connected in series, and the seventh strain gauge and the eighth strain gauge are connected in series, and then connected in a half-bridge manner.

[0021] Preferably, the connecting line of the fifth strain gauge and the eighth strain gauge is perpendicular to the connecting line of the sixth strain gauge and the seventh strain gauge; wherein the angle between the connecting line and the heading is 45°.

[0022] Preferably, the strain gauge includes a first strain gauge, a second strain gauge, a third strain gauge and a fourth strain gauge; and the determination of the vertical load when the helicopter landing gear lands based on the tensile-compressive strain, the shear strain, the bending strain and the torsion strain of the strain gauge includes:

[0023] obtaining tensile-compressive strain, shear strain, bending strain and torsional strain of the first strain gauge, the second strain gauge, the third strain gauge and the fourth strain gauge;

[0024] determining strain states of the first strain gauge, the second strain gauge, the third strain gauge and the fourth strain gauge based on the tensile-compressive strain, the shear strain, the bending strain and the torsional strain of the first strain gauge, the second strain gauge, the third strain gauge and the fourth strain gauge;

[0025] determining a bending moment corresponding to a combined force of the heading load and the vertical load based on the strain states of the first strain gauge, the second strain gauge, the third strain gauge and the fourth strain gauge;

[0026] obtaining the vertical load based on the bending moment corresponding to the combined force of the heading load and the vertical load.

[0027] Preferably, the first strain gauge and the second strain gauge are overlapped in a half-bridge manner, and the third strain gauge and the fourth strain gauge are overlapped in a half-bridge manner.

[0028] Preferably, the first strain gauge, the second strain gauge, the third strain gauge and the fourth strain gauge are overlapped in a full-bridge manner.

[0029] The application has the following beneficial technical effects:

[0030] The application realizes analysis and calculation of transmission of three-way ground load to the landing gear wheel shaft during landing of a helicopter, and the reverse derivation process of strain to load is supplemented by the traditional forward derivation of load to strain, so that the interference of nonlinear superposition of combined load on solving of ground load calculation is eliminated, the position requirement of strain gauge layout to meet unidirectional load sensitivity is reduced, and good universality is achieved. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 is a wheel shaft strain gauge layout schematic diagram provided by the embodiment of the application;

[0032] Figure 2 is a cross-sectional view at A-A provided by the embodiment of the application;

[0033] Figure 3 is a bridge connection manner schematic diagram provided by the embodiment of the application;

[0034] Figure 4 is another bridge connection manner schematic diagram provided by the embodiment of the application;

[0035] Figure 5 is still another bridge connection manner schematic diagram provided by the embodiment of the application. DETAILED DESCRIPTION

[0036] The application provides a helicopter landing gear landing load measurement method, taking a wheel shaft as a measurement object, and reducing the decoupling interference of an unfavorable load on a strain measurement result in a combined load condition by analyzing a qualitative relationship of strain gauge measurement results and establishing a strain decoupling calculation model, so as to realize measurement and analysis of three ground loads.

[0037] In the embodiment of the application, a strain gauge arrangement scheme is as shown in Figure 1 、 Figure 2 : pasted at a wheel shaft position, a total of 12 pieces are needed, R represents a distance from a wheel shaft center to a ground, and an action direction of unknown ground loads Fx, Fy and Fz is as shown in Figure 1 .

[0038] Among them, a lateral load Fy produces a compressive strain ε Fy and a bending strain ε My (where S9, S11 are in a tensile state, and S10, S12 are in a compressive state); a heading load Fx produces a shear strain ε Fx , a bending strain ε Mx1 and a torsional strain ε Mx , a bending strain state of S9, S10 is ε Mx1 , a bending strain state of S11, S12 is -ε Mx1 , a torsional strain state of S9, S12 at 45° is ε Mx , and a torsional strain state of S10, S11 is -ε Mx ; a vertical load Fz produces a shear strain ε Fz and a bending strain ε Mz , a bending strain state of S9, S11 is -ε Mz , and a bending strain state of S10, S12 is ε Mz . Since each strain gauge bears a shear force state, Fxz is a resultant shear force of Fx and Fz acting on the wheel shaft, Fxz' is a tangent direction projection of Fxz at a strain gauge pasting position section, and another force component is in a vertical direction of the pasting position section, and a strain effect produced thereby can be ignored. A strain state of S9, S11 is ε Fxz’ , and a strain state of S10, S12 is -ε Fxz’ . Strain result analysis of each strain gauge is as follows:

[0039]

[0040] Similarly, measurement results of strain gauges 5-8 are as follows:

[0041]

[0042] The following operation is performed on the measurement results of strain gauges 9-12:

[0043]

[0044] The following formula can be obtained by performing the following calculation on the measurement results of strain gauges 5-8. The result obtained by connecting the strain gauges in series is the average value of the measurement results of 5 and 6 and the average value of the measurement results of 7 and 8.

[0045]

[0046] The torque exerted by the yaw load on the wheel axle can be uniquely measured, thereby determining the bridging method of the 9-12 strain gauges. Figure 3 As shown, the bridging method of the 5-8 strain gauges is as follows: Figure 4 As shown.

[0047] according to Figure 1 The strain gauge arrangement method of strain gauges 1-4 yields the strain relationship under triaxial load on the ground as follows:

[0048]

[0049]

[0050] According to the mechanical relationship, F Z1 =F Z2 F X1 =F X2 M nx1 =M nx2 F y1 =F y2 M y1 =M y2

[0051] ε1-ε2=ε Mwx2 -ε Mwx1 +ε Mz2 -ε Mz1 =F x *D+F z *D

[0052] ε4-ε3=ε Mwx4 -ε Mwx3 +ε Mz4 -ε Mz3 =F x *D+F z *D

[0053] Therefore, the bridging method of strain gauges 1-4 can be determined as follows: Figure 5 As shown, the vertical load Fz can be solved by substituting the calculated result of the heading load into the above formula.

[0054] It should be noted that:

[0055] 1) Compared with the method of measuring single direction load by strain gauge, the application can directly solve the complex three-dimensional ground load borne by the landing gear, without determining the arrangement method of strain gauge after accurately analyzing the ground load, and the measurement scheme has universality.

[0056] 2) The bridge design of strain gauge is inversely deduced from the measurement results, and the two methods can effectively remove the influence of shear, tension, compression and bending on the calculation of the heading and lateral load.

[0057] 3) The strain gauge only needs 10 pieces at least to complete the measurement and solution of the three-dimensional ground load, the calculation and solution process is simple and intuitive, and the accuracy of the solution can be effectively guaranteed.

[0058] The application realizes the analysis and calculation of the three-dimensional ground load transfer to the landing gear wheel shaft during the landing process of the helicopter, the reverse deduction process of strain to load is supplemented by the traditional load to strain forward deduction, the interference of nonlinear superposition of combined load on the calculation and solution of the ground load is eliminated, the requirement of strain gauge layout to meet the position sensitive to single load is reduced, and the application has good universality.

Claims

1. A method of measuring landing loads of a helicopter landing gear, characterized in that, The method comprises: pasting at least 10 strain gauges at the wheel axle position; obtaining the tensile-compressive strain, shear strain, bending strain and torsional strain of the strain gauges; determining the heading load, lateral load and / or vertical load of the helicopter landing gear during landing based on the tensile-compressive strain, shear strain, bending strain and torsional strain of the strain gauges; wherein the strain gauges comprise a ninth strain gauge, a tenth strain gauge, an eleventh strain gauge and a twelfth strain gauge; and determining the heading load of the helicopter landing gear during landing based on the tensile-compressive strain, shear strain, bending strain and torsional strain of the strain gauges comprises: obtaining the tensile-compressive strain, shear strain, bending strain and torsional strain of the ninth strain gauge, the tenth strain gauge, the eleventh strain gauge and the twelfth strain gauge; determining the strain state of the ninth strain gauge, the strain state of the tenth strain gauge, the strain state of the eleventh strain gauge and the strain state of the twelfth strain gauge based on the tensile-compressive strain, shear strain, bending strain and torsional strain of the ninth strain gauge, the tenth strain gauge, the eleventh strain gauge and the twelfth strain gauge; determining the torque corresponding to the torsional strain based on the strain state of the ninth strain gauge, the strain state of the tenth strain gauge, the strain state of the eleventh strain gauge and the strain state of the twelfth strain gauge; obtaining the heading load based on the torque corresponding to the torsional strain. The ninth strain gauge, the tenth strain gauge, the eleventh strain gauge and the twelfth strain gauge are connected in full-bridge mode.

2. The method of claim 1, wherein, The connecting line of the ninth strain gauge and the twelfth strain gauge is perpendicular to the connecting line of the tenth strain gauge and the eleventh strain gauge; wherein the angle between the connecting line and the heading direction is 45°.

3. The method of claim 1, wherein, The strain gauges comprise a fifth strain gauge, a sixth strain gauge, a seventh strain gauge and an eighth strain gauge; and determining the lateral load of the helicopter landing gear during landing based on the tensile-compressive strain, shear strain, bending strain and torsional strain of the strain gauges comprises: obtaining the tensile-compressive strain, shear strain, bending strain and torsional strain of the fifth strain gauge, the sixth strain gauge, the seventh strain gauge and the eighth strain gauge; determining the strain state of the fifth strain gauge, the strain state of the sixth strain gauge, the strain state of the seventh strain gauge and the strain state of the eighth strain gauge based on the tensile-compressive strain, shear strain, bending strain and torsional strain of the fifth strain gauge, the sixth strain gauge, the seventh strain gauge and the eighth strain gauge; determining the tensile-compressive force corresponding to the tensile-compressive strain based on the strain state of the fifth strain gauge, the strain state of the sixth strain gauge, the strain state of the seventh strain gauge and the strain state of the eighth strain gauge; obtaining the lateral load based on the tensile-compressive force corresponding to the tensile-compressive strain.

4. The method of claim 3, wherein, The fifth strain gauge and the sixth strain gauge are connected in series, the seventh strain gauge and the eighth strain gauge are connected in series, and then connected in half-bridge mode.

5. The method of claim 4, wherein, The connecting line of the fifth strain gauge and the eighth strain gauge is perpendicular to the connecting line of the sixth strain gauge and the seventh strain gauge; wherein the angle between the connecting line and the heading direction is 45°.

6. The method of claim 1, wherein, The strain gauge comprises a first strain gauge, a second strain gauge, a third strain gauge and a fourth strain gauge; and the vertical load of the helicopter landing gear during landing is determined based on the tensile-compressive strain, shear strain, bending strain and torsional strain of the strain gauges, comprising: obtaining the tensile-compressive strain, shear strain, bending strain and torsional strain of the first strain gauge, the second strain gauge, the third strain gauge and the fourth strain gauge; determining the strain state of the first strain gauge, the strain state of the second strain gauge, the strain state of the third strain gauge and the strain state of the fourth strain gauge based on the tensile-compressive strain, shear strain, bending strain and torsional strain of the first strain gauge, the second strain gauge, the third strain gauge and the fourth strain gauge; determining the bending moment generated by the combined force of the heading load and the vertical load corresponding to the bending strain based on the strain state of the first strain gauge, the strain state of the second strain gauge, the strain state of the third strain gauge and the strain state of the fourth strain gauge; obtaining the vertical load based on the bending moment generated by the combined force of the heading load and the vertical load corresponding to the bending strain.

7. The method of claim 6, wherein, The first strain gauge and the second strain gauge are overlapped in a half-bridge manner, and the third strain gauge and the fourth strain gauge are overlapped in a half-bridge manner.

8. The method of claim 7, wherein, The first strain gauge, the second strain gauge, the third strain gauge and the fourth strain gauge are overlapped in a full-bridge manner.

Images