Dynamic calibration method for landing gear load measurement in drop test bench and load test flight

Abstract

The present invention relates to a drop test bench and a dynamic calibration method for measuring landing gear loads during load testing, belonging to the field of flight test technology. The drop test bench comprises a frame, a lifting system, a landing gear mounting platform, two pairs of landing gear mounting bases, and a force measuring platform. The lifting system is mounted within the frame, with the lower end of the lifting system fixedly connected to the landing gear mounting platform. The lower end surface of the landing gear mounting platform is mounted with a pair of landing gear mounting bases to support the landing gear struts, and another pair of landing gear mounting bases to support the landing gear struts. The force measuring platform is used to measure the impact loads on the landing gear.

Description

Technical Field

[0001] The invention relates to a drop test bench and a dynamic calibration method for landing gear load measurement in a load test flight, and belongs to the technical field of flight test. Background Art

[0002] During aircraft landing gear design qualification, landing gear load measurements are required under severe loading conditions. High-speed landings and carrier-based aircraft landings are among the most severe loading conditions. These conditions place severe dynamic loads on the aircraft. Accurately measuring landing gear loads under these conditions provides a basis for landing gear design qualification, structural modifications, and design optimization.

[0003] Currently, static calibration is the primary method for measuring landing gear loads during aircraft operation. This method uses slow loading calibration tests at different travel times to obtain data on load and strain. Modeling is then performed based on this static calibration data to generate a load equation. This load equation, derived from static loading, accurately measures landing gear loads under static and quasi-static conditions. However, loads measured under severe dynamic loading, such as landing, are affected by inertial loads and damping, resulting in limited accuracy. Load equations developed using dynamic calibration are more appropriate and offer higher accuracy when measuring loads under dynamic loading. Summary of the Invention

[0004] The purpose of the present invention is to provide a dynamic calibration method for landing gear load measurement based on a landing gear and drop test bench equipped with load-measuring strain gauges, design a complete dynamic modeling working condition, plan the implementation form of each working condition, and modify the drop test equipment, thereby improving the load measurement accuracy under severe dynamic loading conditions such as aircraft landing / ship landing, and providing better data for landing gear design evaluation, structural modification and optimization design.

[0005] The technical solution of the present invention:

[0006] A dynamic calibration method for landing gear load measurement in a load test flight, characterized in that the method comprises the following steps:

[0007] Step 1: Before the dynamic calibration test, multiple load-measuring strain gauges are installed on the main force transmission channel of the landing gear structure. These multiple load-measuring strain gauges include strain gauges sensitive to the vertical direction of the landing gear, strain gauges sensitive to the heading of the landing gear, and strain gauges sensitive to the lateral load of the landing gear. The main force transmission channel includes struts and braces.

[0008] Step 2: Based on the landing gear landing load conditions and the decoupling requirements of the load measurement model, design a complete dynamic modeling condition, including vertical load drop vibration conditions at different strokes, heading load drop vibration conditions, and lateral load drop vibration conditions;

[0009] Step 3: Based on the designed modeling and validation conditions, plan the implementation method for each condition. Specifically, the landing gear's buffer stroke and vertical load are achieved by controlling the landing gear's drop height; the heading load is achieved by controlling the landing gear's heading installation angle and wheel rotation speed; and the side load is achieved by controlling the landing gear's side installation angle. Combined drop conditions with vertical, heading, and side loads of varying strokes are achieved by controlling the landing gear's drop height, heading and side installation angles, and wheel rotation speed.

[0010] Step 4: Install vibration sensors on the landing gear and displacement sensors on the buffers. Install high-speed cameras at the test site to measure tire compression and install additional testing equipment.

[0011] Step 5: Perform drop tests on the drop test bench in sequence: without an attitude angle, with a heading installation angle, with a sideways installation angle, and with both heading and sideways installation angles. Obtain test results for each operating condition. The test results include load data, strain data, and buffer stroke data at each moment.

[0012] Step 6: Perform coordinate conversion on the load data from the above test results: To better achieve the excitation effect of the heading and side loads, project the measured loads of the drop platform under each working condition into the body axis coordinate system with the wheel axle center as the origin, forming the load data in the new body axis coordinate system. Among them, the body axis coordinate system with the wheel axle center as the origin has a positive Z axis parallel to the axis of the landing gear strut and pointing upward, a positive X axis perpendicular to the Z axis and pointing in the positive heading, and a positive Y axis perpendicular to the XZ axis and pointing outward.

[0013] Step 7: Determine the step size for dividing the total buffer stroke based on the accuracy of the sensor measuring the buffer stroke data; divide the buffer stroke into continuous small stroke intervals according to the step size, and extract the load data and strain data in the new body axis coordinate system within the small stroke interval from the test results;

[0014] Step 8: Start modeling by interval: Based on the sorted load and strain data of the same small stroke interval, bring it into the load equation for linear regression and solve the coefficient of the load equation; the load equation is: ;

[0015] in, The buffer stroke is Heading, lateral or vertical load in the new body axis coordinate system within the interval; For load The corresponding strain in the same buffer travel interval; Buffer stroke Interval, coefficient of the load equation in the new body axis coordinate system;

[0016] The drop test bench includes: frame, lifting system, hanging basket, landing gear mounting platform, two pairs of landing gear mounting bases, and force measuring platform;

[0017] A lifting system is installed within the frame, with the lower end of the lifting system connected to the hanging basket via a solenoid valve. The lower end of the hanging basket is fixedly connected to the landing gear mounting platform. The lower end surface of the landing gear mounting platform is mounted with a pair of landing gear mounting bases for the landing gear struts, and another pair of landing gear mounting bases for the landing gear struts. The force measuring platform is used to measure the impact load of the landing gear.

[0018] Each landing gear mounting base includes a base body and a heightening base, wherein the heightening base is mounted on the base body and can adjust the height of the landing gear mounting base vertically;

[0019] In order to stimulate the landing gear heading impact load, the lower surface of the landing gear mounting platform is parallel to the impact surface of the force measuring platform. The two pairs of landing gear mounting bases are adjusted to different heights through the raising base, so that the landing gear heading installation angle can be deflected in the positive or negative heading direction.

[0020] In order to stimulate the lateral impact load of the landing gear, the landing gear mounting platform is adjusted so that the lower surface and the impact surface of the force measuring platform are at a preset angle along the lateral direction, and the landing gear heading installation angle is 0 degrees;

[0021] In order to simultaneously stimulate the landing gear directional impact load and lateral impact load, the two pairs of landing gear mounting bases are adjusted to different heights through the raising base, so that the landing gear directional mounting angle can be deflected along the positive or negative heading. At the same time, the landing gear mounting platform is adjusted so that the lower surface and the impact surface of the force measuring platform are at a preset angle along the lateral direction.

[0022] Step 2 also includes:

[0023] At the same time, the verification conditions of the load measurement model are designed. The verification conditions are combined drop conditions of vertical, heading and lateral loads at different strokes.

[0024] The method further comprises:

[0025] Step 10: Verify model accuracy: Substitute the measured strain data from the drop test of the model verification condition into the load equation of the corresponding stroke to obtain the model calculated load, and compare it with the measured load of the drop test table to obtain the verification accuracy of the model.

[0026] The number of load-measuring strain gauges shall be no less than three, and there shall be at least one electric bridge sensitive to the vertical, heading and lateral loads of the landing gear.

[0027] The dynamic calibration test shall have at least three modeling conditions, including at least one condition containing axial loads, at least one condition containing lateral loads, and at least one condition containing vertical loads.

[0028] The verification conditions of the dynamic calibration test are similar to the actual landing process of the aircraft, and the three-dimensional loads of vertical, heading and lateral must be stimulated simultaneously.

[0029] The yaw installation angle of the landing gear shall not be less than 1° to ensure that a sufficiently large yaw load is stimulated; the lateral installation angle of the landing gear shall not be less than 1° to ensure that a sufficiently large lateral load is stimulated; the drop height shall at least ensure that the sinking speed when the landing gear contacts the drop platform is not less than 50% of the maximum operating sinking speed.

[0030] The step length should not exceed 1 cm.

[0031] The method is used to measure the landing gear load of a land-based aircraft landing at a high sinking speed and a carrier-based aircraft landing / ship landing under severe dynamic loading conditions.

[0032] Advantages of the present invention:

[0033] (1) Compared with previous methods, the test method used in this method is basically consistent with the actual use environment of aircraft landing gear. Through dynamic tests, a load measurement model is established for load measurement under dynamic loading conditions such as landing, with higher measurement accuracy.

[0034] (2) The test method used in this method can simulate the working conditions by similar to the actual landing process of an aircraft, verify the accuracy of the model, and make the measurement results more convincing. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a flow chart of the method of the present invention;

[0036] Figure 2a This is a structural diagram of the drop test bench.

[0037] Figure 2b This is a structural diagram of a method for implementing the landing gear heading installation angle.

[0038] Figure 2c This is a structural diagram of the method for achieving the lateral installation angle of the landing gear.

[0039] Figure 2d Schematic diagram of the method for achieving heading load. DETAILED DESCRIPTION

[0040] The present invention will be further described in detail below with reference to the accompanying drawings.

[0041] Example 1

[0042] A dynamic calibration method for landing gear load measurement in aircraft load test flight is used to measure landing gear loads under severe dynamic loading conditions such as aircraft landing / ship landing, etc. Figure 1 As shown, the method includes the following steps:

[0043] Step 1: Before the dynamic calibration test, Figure 2a and Figure 2b The main force transmission channel of the landing gear structure is equipped with load-measuring strain gauges, and the bridges that are sensitive to the vertical, heading and lateral loads of the landing gear must be guaranteed to have;

[0044] Step 2: Based on the landing gear's landing load conditions and the decoupling requirements of the load measurement model, a complete set of dynamic modeling conditions is designed, as shown in Table 1. These conditions include vertical load drop conditions, azimuth load drop conditions, and lateral load drop conditions at different travels. Simultaneously, validation conditions for the load measurement model are designed, which are combined drop conditions with vertical, azimuth, and lateral loads at different travels.

[0045] Table 1

[0046]

[0047] Step 3: Based on the designed modeling conditions and mold verification conditions, plan the implementation method of each condition. Among them: the buffer stroke and vertical load are achieved by controlling the landing gear drop height; the heading load is achieved by controlling the landing gear heading installation angle and the wheel belt rotation speed; Figure 2c and 2d As shown in the figure, the side load is achieved by controlling the lateral installation angle of the landing gear; the combined drop shock conditions of vertical, directional and lateral loads of different strokes are achieved by combining the control of the landing gear's drop height, directional installation angle, lateral installation angle, and wheel rotation speed;

[0048] Step 4: Modify the drop test equipment according to the implementation method of each working condition planned in Step 3, focusing on the working conditions with the landing gear with heading installation angle and lateral installation angle, which are specially designed working conditions for load measurement;

[0049] Step 5: Install vibration sensors on the landing gear and displacement sensors on the buffers. Install speed cameras at the test site to measure tire compression and install additional testing equipment.

[0050] Step 6: Perform drop tests without attitude angle, with pitch angle, with roll angle, and with both pitch and roll angles in sequence to obtain the relationship between different loads and their combinations and travel.

[0051] Step 7: Coordinate Conversion of Load Data: To better achieve the excitation effect of heading and side loads, the measured loads of the drop platform under each working condition are projected into the body axis coordinate system with the wheel axle center as the origin, forming the load data in the new body axis coordinate system. The body axis coordinate system with the wheel axle center as the origin is: the Z axis is parallel to the axis of the landing gear strut and points upward, the X axis is perpendicular to the Z axis and points in the positive heading direction, and the Y axis is perpendicular to the X and Z axes and points outward.

[0052] Step 8: Extract data in segments and reassemble. First, divide the buffer stroke into continuous small intervals with a step size of 1 mm, such as mm, where: 、 is the maximum value of the buffer stroke; then, the load and strain data of the drop shock condition are divided by stroke, and the load and strain data with the same stroke interval are placed in a matrix to form new load data and strain data divided and reorganized according to the buffer stroke; then, the data of each interval are repeatedly selected until the last interval stroke mm stroke.

[0053] Step 9: Start modeling in intervals. Based on the sorted load and strain data, substitute them into formula (1) for linear regression and obtain the coefficients of the load equation, thus obtaining the load equation.

[0054] (1)

[0055] Step 10: Verify model accuracy. Substitute the measured strain data from the drop test into the load equation for the corresponding stroke to obtain the model calculated load. Compare this with the load measured on the drop test platform to determine the model's accuracy.

[0056] Before the dynamic calibration test, load-measuring strain gauges shall be installed on the landing gear structure. The number of strain gauges shall be no less than 3, and there shall be at least one electric bridge that is sensitive to the vertical, heading and lateral loads of the landing gear.

[0057] The dynamic calibration test shall have at least three modeling conditions, including at least one condition containing axial loads, at least one condition containing lateral loads, and at least one condition containing vertical loads.

[0058] The verification conditions of the dynamic calibration test are similar to the actual landing process of an aircraft, and the three-dimensional loads of vertical, heading and lateral must be stimulated simultaneously.

[0059] The yaw load of the dynamic calibration test is achieved by controlling the yaw installation angle of the landing gear and the wheel belt turntable. The yaw installation angle of the landing gear shall not be less than 1° to ensure that a sufficiently large yaw load is stimulated. The lateral load is achieved by controlling the lateral installation angle of the landing gear. The lateral installation angle of the landing gear shall not be less than 1° to ensure that a sufficiently large lateral load is stimulated. The buffer stroke is achieved by controlling the landing gear drop height. The drop height shall at least ensure that the sinking speed of the landing gear when it contacts the drop table is not less than 50% of the maximum operating sinking speed.

[0060] Example 2

[0061] The present invention provides a dynamic calibration test of landing gear loads implemented by a drop test bench, specifically using the following steps:

[0062] Step 1: Install the landing gear on the basket according to the required attitude angle;

[0063] Step 2: Control the lifting actuator to lift the landing gear, basket and counterweight to the predetermined drop height;

[0064] Step 3: According to the test requirements, turn the wheel belt to the specified speed;

[0065] Step 4: Open the permanent magnetic suction on the upper part of the hanging basket, and the landing gear falls freely, hitting the force measuring platform, and at the same time triggering the acquisition system to obtain the test data of each channel. The test personnel collect the test data.

[0066] The method can be used to measure loads in a dynamic and severe loading process such as aircraft landing.

[0067] A dynamic calibration method for measuring landing gear loads during aircraft load test flight is provided, which is used for measuring landing gear loads under severe dynamic loading conditions such as aircraft landing or ship landing. The method comprises the following steps:

[0068] Step 1: Before the dynamic calibration test, load-measuring strain gauges shall be installed on the main force transmission channels of the landing gear structure. The number of strain gauges shall be no less than 3, and at least one strain gauge shall be installed on each bridge that is sensitive to the vertical, azimuth, and lateral loads of the landing gear.

[0069] Step 2: Design complete dynamic modeling and validation conditions based on the landing gear loading conditions and the decoupling requirements of the load measurement model. The dynamic calibration test modeling conditions must include at least three conditions, including at least one condition with azimuth loads, at least one condition with lateral loads, and at least one condition with vertical loads. The validation conditions for the dynamic calibration test should be similar to an actual aircraft landing process, stimulating vertical, azimuth, and lateral loads simultaneously.

[0070] Step 3: Plan the implementation method for each operating condition. The vertical load drop condition is achieved by controlling the landing gear descent height; the azimuth load drop condition is achieved by controlling the pitch angle of the landing gear mounting platform and the wheel speed; the side load drop condition is achieved by controlling the roll angle of the landing gear mounting platform; and the combined vertical, azimuth, and side load drop condition is achieved by controlling the combination of the pitch and roll mounting platforms and the wheel speed. To ensure sufficient azimuth and side loads are induced, the pitch and roll angles of the landing gear mounting platform must be no less than 1°. The buffer travel is achieved by controlling the landing gear descent height, which must ensure that the landing gear sinking velocity at the moment of contact with the drop platform is no less than 50% of the maximum operating sinking velocity.

[0071] Step 4: Modify the drop test equipment according to the drop conditions planned in Step 3, focusing on the landing gear mounting platform for conditions with yaw and lateral mounting angles, which are specially designed for load measurement.

[0072] Step 5: Install vibration sensors on the landing gear axles and displacement sensors on the bumpers. Install speed cameras at the test site to measure tire compression and install additional testing equipment.

[0073] Step 6: Perform drop tests without attitude angle, with pitch angle, with roll angle, and with both pitch and roll angles in sequence to obtain the relationship between different loads and their combinations and travel.

[0074] Step 7: Measure the load on the drop platform based on the ground coordinate system Substitute the coordinate transformation matrix to obtain the load along the local body axis coordinate system of the landing gear , see formula (2) for details, where: is the heading installation angle of the landing gear, is the lateral mounting angle of the landing gear.

[0075] (2)

[0076] Step 8: Divide the measured load and strain data after coordinate transformation by stroke, and put the load and strain data in the same stroke interval into a matrix to form new load and strain data divided by stroke. For example, divide the buffer stroke into continuous small intervals with a step size of 1mm. ,in , forming load data as shown in Equation (3) to Equation (5), and the strain data are similar.

[0077] (3)

[0078] (4)

[0079] (5)

[0080] The data of different modeling conditions of the drop test are reorganized into a new load-strain matrix according to the travel interval, as shown in Equation (6) and Equation 7, where , until the last trip.

[0081] (6)

[0082] (7)

[0083] Step 9: Based on the load and strain data in the same stroke range, the coefficients of the load equation can be obtained by substituting them into formula (8), thereby obtaining the load equation.

[0084] (8)

[0085] Step 10: Substitute the measured strain data of the drop test of the mold verification condition into the load equation of the corresponding stroke to obtain the model calculation load, and compare it with the measured load of the drop test table to obtain the verification accuracy of the model.

Claims

1. A dynamic calibration method for landing gear load measurement in a load test flight, characterized in that: The method comprises the following steps: Step 1: Before the dynamic calibration test, multiple load-measuring strain gauges are installed on the main force transmission channel of the landing gear structure. These multiple load-measuring strain gauges include strain gauges sensitive to the vertical direction of the landing gear, strain gauges sensitive to the heading of the landing gear, and strain gauges sensitive to the lateral load of the landing gear. The main force transmission channel includes struts and braces. Step 2: Based on the landing gear landing load conditions and the decoupling requirements of the load measurement model, design a complete dynamic modeling condition, including vertical load drop vibration conditions at different strokes, heading load drop vibration conditions, and lateral load drop vibration conditions; Step 3: Based on the designed modeling and validation conditions, plan the implementation method for each condition. Specifically, the landing gear's buffer stroke and vertical load are achieved by controlling the landing gear's drop height; the heading load is achieved by controlling the landing gear's heading installation angle and wheel rotation speed; and the side load is achieved by controlling the landing gear's side installation angle. Combined drop conditions with vertical, heading, and side loads of varying strokes are achieved by controlling the landing gear's drop height, heading and side installation angles, and wheel rotation speed. Step 4: Install vibration sensors on the landing gear and displacement sensors on the buffers. Install high-speed cameras at the test site to measure tire compression and install additional testing equipment. Step 5: Perform drop tests on the drop test bench in sequence: without an attitude angle, with a heading installation angle, with a sideways installation angle, and with both heading and sideways installation angles. Obtain test results for each operating condition. The test results include load data, strain data, and buffer stroke data at each moment. Step 6: Perform coordinate conversion on the load data from the above test results: To better achieve the excitation effect of the heading and side loads, project the measured loads of the drop platform under each working condition into the body axis coordinate system with the wheel axle center as the origin, forming the load data in the new body axis coordinate system. Among them, the body axis coordinate system with the wheel axle center as the origin has a positive Z axis parallel to the axis of the landing gear strut and pointing upward, a positive X axis perpendicular to the Z axis and pointing in the positive heading, and a positive Y axis perpendicular to the XZ axis and pointing outward. Step 7: Determine the step size for dividing the total buffer stroke based on the accuracy of the sensor measuring the buffer stroke data; divide the buffer stroke into continuous small stroke intervals according to the step size, and extract the load data and strain data in the new body axis coordinate system within the small stroke interval from the test results; Step 8: Start modeling by interval: Based on the sorted load and strain data of the same small stroke interval, bring it into the load equation for linear regression and solve the coefficient of the load equation; the load equation is: ； in, The buffer stroke is Heading, lateral or vertical load in the new body axis coordinate system within the interval; For load The corresponding strain in the same buffer travel interval; Buffer stroke Interval, coefficient of the load equation in the new body axis coordinate system; The drop test bench includes: frame, lifting system, hanging basket, landing gear mounting platform, two pairs of landing gear mounting bases, and force measuring platform; A lifting system is installed within the frame, with the lower end of the lifting system connected to the hanging basket via a solenoid valve. The lower end of the hanging basket is fixedly connected to the landing gear mounting platform. The lower end surface of the landing gear mounting platform is mounted with a pair of landing gear mounting bases for the landing gear struts, and another pair of landing gear mounting bases for the landing gear struts. The force measuring platform is used to measure the impact load of the landing gear. Each landing gear mounting base includes a base body and a heightening base, wherein the heightening base is mounted on the base body and can adjust the height of the landing gear mounting base vertically; In order to stimulate the landing gear heading impact load, the lower surface of the landing gear mounting platform is parallel to the impact surface of the force measuring platform. The two pairs of landing gear mounting bases are adjusted to different heights through the raising base, so that the landing gear heading installation angle can be deflected in the positive or negative heading direction. In order to stimulate the lateral impact load of the landing gear, the landing gear mounting platform is adjusted so that the lower surface and the impact surface of the force measuring platform are at a preset angle along the lateral direction, and the landing gear heading installation angle is 0 degrees; In order to simultaneously stimulate the landing gear directional impact load and lateral impact load, the two pairs of landing gear mounting bases are adjusted to different heights through the raising base, so that the landing gear directional mounting angle can be deflected along the positive or negative heading. At the same time, the landing gear mounting platform is adjusted so that the lower surface and the impact surface of the force measuring platform are at a preset angle along the lateral direction.

2. The method according to claim 1, characterized in that Step 2 also includes: At the same time, the verification conditions of the load measurement model are designed. The verification conditions are combined drop conditions of vertical, heading and lateral loads at different strokes. The method further comprises: Step 10: Verify model accuracy: Substitute the measured strain data from the drop test of the model verification condition into the load equation of the corresponding stroke to obtain the model calculated load, and compare it with the measured load of the drop test table to obtain the verification accuracy of the model.

3. The method according to claim 1, characterized in that The number of load-measuring strain gauges shall be no less than three, and there shall be at least one electric bridge sensitive to the vertical, heading and lateral loads of the landing gear.

4. The method according to claim 1, wherein The dynamic calibration test shall have at least three modeling conditions, including at least one condition containing axial loads, at least one condition containing lateral loads, and at least one condition containing vertical loads.

5. The method according to claim 1, wherein The verification conditions of the dynamic calibration test are similar to the actual landing process of the aircraft, and the three-dimensional loads of vertical, heading and lateral must be stimulated simultaneously.

6. The method according to claim 1, characterized in that The yaw installation angle of the landing gear shall not be less than 1 degree to ensure that a sufficiently large yaw load is stimulated; the lateral installation angle of the landing gear shall not be less than 1 degree to ensure that a sufficiently large lateral load is stimulated; the drop height shall at least ensure that the sinking speed of the landing gear when it contacts the drop platform is not less than 50% of the maximum operating sinking speed.

7. The method according to claim 1, characterized in that The step length should not exceed 1 cm.

8. The method according to claim 1, characterized in that The method is used for measuring the landing gear load of a land-based aircraft landing at a high sinking speed and a carrier-based aircraft landing / under the condition of severe dynamic loading of the carrier landing gear.

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