A platform and method for measuring inertial parameters based on frequency response function mass line

Abstract

The invention discloses an inertial parameter measurement platform and method based on a frequency response function mass line. The platform comprises a support frame, a balancing platform, a triaxial acceleration sensor, a force hammer, a data collector and a display. The balancing platform is suspended in the support frame horizontally by a flexible rope, a structure to be measured is placed on the balancing platform, a plurality of triaxial acceleration sensors are arranged on the structure to be measured according to measurement requirements, the force hammer is used to apply excitation to the structure to be measured, the triaxial acceleration sensor and the force hammer are respectively connected to the data collector through data lines, and the data collector is also connected to the display for displaying the collected data; the platform is easy to adjust the balance operation and can be disassembled and extended by itself; the coordinates of the excitation point and the response point can be accurately determined by means of the geometric parameters of the measuring platform, and repeated measurement by a three-dimensional coordinate instrument is not required, the inertial parameters and errors of the experimental platform can be known, and the measurement accuracy can be improved when calculating the inertial parameters of the component to be measured.

Description

Technical Field

[0001] The invention relates to the technical field of complex component rigid body inertia parameter measurement, in particular to an inertia parameter measurement platform and method based on a frequency response function mass line. Background Art

[0002] Efficient, convenient and accurate acquisition of rigid body inertia parameters of complex components such as automobiles, aviation and aerospace has always been a hot topic and difficulty in the field of mechanical manufacturing. The inertia parameters of complex components include mass, center of mass, moment of inertia and product of inertia. In general, when conducting mass line method experiments, soft ropes or flexible supports are used to build a test bench to measure the inertia parameters of the component to be tested. The coordinates of the excitation point and the response point are measured by an expensive three-dimensional coordinate measuring machine. The factors affecting the experimental results due to the unbalanced force of each flexible rope are ignored, and the error influence of the experimental test platform on the measurement results is ignored, resulting in a relatively cumbersome measurement process, high cost, low efficiency and poor accuracy. Summary of the invention

[0003] In response to the above test experimental problems, the present invention provides an inertial parameter measurement platform and method based on frequency response function mass line.

[0004] The technical solution for achieving the purpose of the present invention is:

[0005] An inertial parameter measurement platform based on a frequency response function mass line comprises a support frame, a balancing platform, a triaxial acceleration sensor, a force hammer, a data collector and a display. The balancing platform is suspended in the support frame horizontally by a flexible rope, a structure to be measured is placed on the balancing platform, a plurality of triaxial acceleration sensors are arranged on the structure to be measured according to measurement requirements, the force hammer is used to apply excitation to the structure to be measured, the triaxial acceleration sensor and the force hammer are respectively connected to the data collector through data lines, and the data collector is also connected to the display to display the collected data.

[0006] The balancing platform comprises a pair of platform frames which are arranged in parallel and at intervals, the two ends of the platform frames are connected by connecting rods respectively, the upper surface of each platform frame is provided with an elongated groove which opens upward, a rotating shaft is provided in the middle of the elongated groove, and the two ends of the rotating shaft pass through the platform stretcher, the rotating shaft is connected to the platform stretcher through bearings, gears are provided at the two ends of the rotating shaft in the elongated groove, the lower part of the gear is meshed with two symmetrically arranged ratchets fixed to the platform frame through ratchet shafts, a V-shaped support frame is fixed in the middle of the rotating shaft, the structural member to be tested is mounted on the V-shaped support frame, the two sides of the V-shaped support frame are respectively connected to one end of the oblique bracket, the other end of the oblique bracket is connected to one end of a slider arranged in the elongated groove, the other end of the slider is connected to the platform frame through a spring, and the lower part of the ratchet is connected to the two sliders in the groove through pull wires respectively.

[0007] The rotating shaft passes through the platform single frame and is provided with balance indicator needles at both ends. The balance indicator needles rotate synchronously with the rotating shaft. The balance indicator needles can be used to determine whether the structure to be tested mounted on the V-shaped support frame is in a balanced state.

[0008] The pull wire is connected to the slider via a slipknot bolt.

[0009] The two ratchets are connected via a tension spring.

[0010] Both ends of the platform single frame are provided with lifting ears, and the flexible rope suspends the balancing platform horizontally in the supporting frame through the four lifting ears.

[0011] The connecting rod is connected to the platform stretcher through a fastening bolt. By adjusting the fastening position of the connecting rod and the balancing single frame, the distance between the two platform single frames can be adjusted, thereby adjusting the width of the balancing platform.

[0012] A method for measuring an inertial parameter measurement platform based on a frequency response function mass line comprises the following steps:

[0013] 1) Place the structure to be tested on the balance platform and adjust the V-shaped support frame to balance the entire test platform;

[0014] 2) Place two triaxial acceleration sensors on P1 (L1 W1 H1) and P2 (L2 W2 H2), and set P1 as the coordinate reference point to establish a coordinate system, with the axis perpendicular to the plane where the balance platform is located as the z-axis, the direction of the connecting rod as the x-axis, and the axis perpendicular to the xz plane as the y-axis; then arrange 13 triaxial acceleration sensors on the structure to be tested, the contour formed by the position of the arrangement point of each sensor is approximately the main contour of the structure to be tested, and the area enclosed by the connection line of any three sensors is as large as possible, the measurement axes of each sensor are parallel to the three axes of the established coordinate system, and the arrangement points are prohibited from being arranged at the symmetry axis or rotation node line of the component to be tested;

[0015] 3) Connect each acceleration sensor and hammer to the data collector through a data line, calibrate and debug the data collector, set the acquisition time to 10s, and remove abnormal signals; use the hammer to excite the structure to be tested, and collect data once each time the structure is stimulated. A total of 7 positions are stimulated, and each position is stimulated three times in the three-axis direction;

[0016] 4) According to the signals of each acceleration sensor and hammer collected by the data acquisition device, and the acceleration value between the natural frequency of the flexible rope and the natural frequency of the structure to be tested, the average acceleration of each excitation point under three excitation responses is taken as the acceleration of the point;

[0017] 5) Calculate the inertia parameters of the structure to be tested based on the collected acceleration and the excitation force applied by the hammer, as follows:

[0018] 5-1) When the entire rigid body is excited When the acceleration P1 is applied, the corresponding point can measure the acceleration in three directions: (a 1 x a 1 y a 1 z ), the three-axis acceleration of P3 is (a 3 x a 3 y a 3 z ), according to the relationship between the acceleration of each point and the acceleration of the origin of the rigid body under the same excitation force, the following formula (1) is determined;

[0019]

[0020] The excitation force F is calculated by the three equations in formula (1): 1 The angular acceleration (α 1 β 1 γ 1 );

[0021] 5-2) Given the angular acceleration under the same excitation force and the P at any point on the structure to be tested j (L j W j H j )Three-axis acceleration sensor value (a j x a j y a j z ), according to formula (1), the coordinates of each response point of the entire structural rigid body in the direction of the response acceleration are inversely calculated, as shown in the following formula (2):

[0022]

[0023] 5-3) Calculate the equivalent acceleration of the center of mass of the entire structural member. Suppose the acceleration of the center of mass of the entire rigid body is (a c x a c y a c z ), the coordinates of the centroid are (L c W c H c ),but:

[0024]

[0025] 5-4) Combine the rigid body center of mass motion formula and formula (3) to calculate the mass and center of mass of the entire rigid body. Suppose the mass of the entire rigid body is M c ,but:

[0026]

[0027] Substitute the data under at least two excitations to calculate M c and the center of mass (L c W c H c );

[0028] 5-5) According to the translational equivalent theorem of force, the moment of momentum theorem and the moment of momentum theorem of rigid body rotation about a fixed axis, the moment of inertia parameters of the entire rigid body are calculated as follows:

[0029]

[0030]

[0031] Combining formula (5) and formula (6), solving the inertia parameters requires parameters under at least three excitations; based on the 7 excitations in step 3) and the data obtained from 15 triaxial acceleration sensor measurement points, multiple sets of data are superimposed according to the above steps to improve the accuracy of the inertia parameters;

[0032] 5-6) Finally, the mass, center of mass coordinates and moment of inertia parameters of the entire rigid body are calculated. By removing the mass, center of mass coordinates and moment of inertia parameters of the known measuring platform, the mass, center of mass coordinates and moment of inertia parameters of the component to be measured are obtained.

[0033] The present invention provides an inertial parameter measurement platform and method based on a frequency response function mass line. The platform has simple balancing operation and can be disassembled and expanded by itself. The coordinates of the excitation point and the response point can be accurately determined by means of the geometric parameters of the measurement platform without the need for repeated measurement by a three-dimensional coordinate instrument. The inertial parameters and errors of the experimental platform can be known, and the measurement accuracy can be improved when calculating the inertial parameters of the component to be measured. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is an axonometric view of an inertial parameter measurement platform based on the frequency response function mass line;

[0035] Figure 2 This is the axonometric view of the balancing platform;

[0036] Figure 3 Longitudinal section of the balance platform Figure 1 ;

[0037] Figure 4Longitudinal section of the balance platform Figure 2 ;

[0038] Figure 5 for Figure 4 Enlarged view of part A in the middle;

[0039] Figure 6 It is a flow chart of a measurement method of an inertial parameter measurement platform based on a frequency response function mass line;

[0040] Figure 7 This is a schematic diagram of the arrangement of the three-axis sensors on the measurement platform;

[0041] Figure 8 It is the acceleration time domain and frequency domain diagram;

[0042] In the figure: 1. Support frame 2. Balance platform 3. Flexible rope 4. Structural member to be tested 5. Three-axis acceleration sensor 6. Hammer 7. Display 8. Data collector 9. Platform frame 10. Long groove 11. Balance indicator needle 12. Connecting rod 13. Lifting ear 14. Oblique bracket 15. V-shaped support frame 16. Spring 17. Slider 18. Pull wire 19. Gear 20. Rotating shaft 21. Ratchet 22. Ratchet shaft 23. Tension spring. DETAILED DESCRIPTION

[0043] The present invention is further described below with reference to the accompanying drawings and embodiments, but the present invention is not limited thereto.

[0044] Example:

[0045] like Figure 1 , Figure 2 , Figure 3 and Figure 4 As shown:

[0046] An inertial parameter measurement platform based on a frequency response function mass line includes a support frame 1, a balancing platform 2, a triaxial acceleration sensor 5, a force hammer 6, a data collector 8 and a display 7. The balancing platform 2 is suspended horizontally in the support frame 1 through a flexible rope 3, a structure 4 to be measured is placed on the balancing platform 2, a plurality of triaxial acceleration sensors 5 are arranged on the structure 4 to be measured according to measurement requirements, the force hammer 6 is used to apply excitation to the structure 4 to be measured, the triaxial acceleration sensor 5 and the force hammer 6 are respectively connected to the data collector 8 through data lines, and the data collector 8 is also connected to the display 7 for displaying the collected data.

[0047] The balancing platform 2 comprises a pair of parallel and spaced platform frames 9, both ends of which are connected by connecting rods 12. An elongated groove 10 with an opening upward is provided on the upper surface of each platform frame 9. A rotating shaft 20 is provided in the middle of the elongated groove 10, and both ends of the rotating shaft 20 pass through the platform stretcher 9. The rotating shaft 20 is connected to the platform stretcher through bearings. Gears 19 are provided at both ends of the rotating shaft 20 in the elongated groove 10. The lower part of the gear 19 is meshed with two symmetrically arranged ratchets 21 fixed to the platform frame 9 through a ratchet shaft 22. A V-shaped support frame 15 is fixed in the middle of the rotating shaft 20. The structural member 4 to be tested is mounted on the V-shaped support frame 15. Both sides of the V-shaped support frame 15 are respectively connected to one end of the oblique bracket 14, and the other end of the oblique bracket 14 is connected to one end of a slider arranged in the elongated groove 10. The other end of the slider 17 is connected to the platform frame 9 through a spring 16. The lower part of the ratchet 21 is connected to the two sliders 17 in the groove 10 through a pull wire 18.

[0048] The rotating shaft 20 passes through the platform single frame 9 and is provided with balance indicator needles 11 at both ends. The balance indicator needles 11 rotate synchronously with the rotating shaft 20. The balance indicator needles 11 can be used to determine whether the structure 4 to be tested mounted on the V-shaped support frame 15 is in a balanced state.

[0049] The pull wire 18 is connected to the slider 17 via a slipknot bolt.

[0050] The two ratchet wheels 21 are connected via a tension spring 23 .

[0051] Both ends of the platform single frame 9 are provided with lifting ears 13 , and the flexible rope 3 suspends the balancing platform 2 horizontally in the supporting frame 1 through the four lifting ears 13 .

[0052] When using the measurement platform to measure inertial parameters, the structure to be measured 4 is placed on the V-shaped support frame 15. When the structure to be measured 4 is just balanced, the balance indicator needle 11 is at the center line position, and the four flexible ropes 3 are balanced in force; when the structure to be measured 4 tilts to one side, the balance indicator needle 11 tilts accordingly, and the slider on the tilted side also compresses the spring 16 away from the rotating shaft 20, driving the pull wire 18 connected to the hitch bolt to pull the ratchet 21 to rotate, and the teeth of the ratchet 21 match the teeth of the gear 19, so that the V-shaped support frame 14 can only be allowed to move to the other side under manual adjustment until it is balanced.

[0053] like Figure 6 As shown, a measurement method of an inertial parameter measurement platform based on a frequency response function mass line includes the following steps:

[0054] 1) Place the structure to be tested on the balance platform and adjust the V-shaped support frame to balance the entire test platform;

[0055] 2) Place two triaxial acceleration sensors on P1 (L1 W1 H1) and P2 (L2 W2 H2), and set P1 as the coordinate reference point, the axis perpendicular to the plane where the balance platform is located as the z-axis, the direction of the connecting rod as the x-axis, and the axis perpendicular to the xz plane as the y-axis; then arrange 13 triaxial acceleration sensors on the structure to be tested, the contour formed by the position of each sensor arrangement point is approximately the main contour of the structure to be tested, and the area enclosed by the connection line of any three sensors is as large as possible, the measurement axes of each sensor are parallel to the three axes of the established coordinate system, and the arrangement points are prohibited from being arranged at the symmetry axis or rotation node line of the component to be tested, such as Figure 7 As shown;

[0056] 3) Connect each acceleration sensor and hammer to the data collector through a data line, calibrate and debug the data collector, set the acquisition time to 10s, and remove abnormal signals; use the hammer to excite the structure to be tested, and collect data once each time the structure is stimulated. A total of 7 positions are stimulated, and each position is stimulated three times in the three-axis direction;

[0057] 4) According to the signals of each acceleration sensor and hammer collected by the data collector, and the acceleration value between the natural frequency of the flexible rope and the natural frequency of the structure to be tested, the average acceleration of each excitation point under three excitation responses is taken as the acceleration of the point, such as Figure 8 As shown;

[0058] 5) Calculate the inertia parameters of the structure to be tested based on the collected acceleration and the excitation force applied by the hammer, as follows:

[0059] 5-1) When the entire rigid body is excited When the acceleration P1 is applied, the corresponding point can measure the acceleration in three directions: (a 1 x a 1 y a 1 z ), the three-axis acceleration of P3 is (a 3 x a 3 y a 3 z ), according to the relationship between the acceleration of each point and the acceleration of the origin of the rigid body under the same excitation force, the following formula (1) is determined;

[0060]

[0061] The excitation force F is calculated by the three equations in formula (1): 1 The angular acceleration (α 1 β 1 γ1 );

[0062] 5-2) Given the angular acceleration under the same excitation force and the P at any point on the structure to be tested j (L j W j H j )Three-axis acceleration sensor value (a j x a j y a j z ), according to formula (1), the coordinates of each response point of the entire structural rigid body in the direction of the response acceleration are inversely calculated, as shown in the following formula (2):

[0063]

[0064] 5-3) Calculate the equivalent acceleration of the center of mass of the entire structural member. Suppose the acceleration of the center of mass of the entire rigid body is (a c x a c y a c z ), the coordinates of the centroid are (L c W c H c ),but:

[0065]

[0066] 5-4) Combine the rigid body center of mass motion formula and formula (3) to calculate the mass and center of mass of the entire rigid body. Suppose the mass of the entire rigid body is M c ,but:

[0067]

[0068] Substitute the data under at least two excitations to calculate M c and the center of mass (L c W c H c );

[0069] 5-5) According to the translational equivalent theorem of force, the moment of momentum theorem and the moment of momentum theorem of rigid body rotation about a fixed axis, the moment of inertia parameters of the entire rigid body are calculated as follows:

[0070]

[0071]

[0072] Combining formula (5) and formula (6), solving the inertia parameters requires parameters under at least three excitations; based on the 7 excitations in step 3) and the data obtained from 15 acceleration sensor measurement points, multiple sets of data are superimposed according to the above steps to improve the accuracy of the inertia parameters;

[0073] 5-6) Finally, the mass, center of mass coordinates and moment of inertia parameters of the entire rigid body are calculated. By removing the mass, center of mass coordinates and moment of inertia parameters of the known measuring platform, the mass, center of mass coordinates and moment of inertia parameters of the component to be measured are obtained.

Claims

1. An inertial parameter measurement platform based on frequency response function mass line, characterized in that: It includes a support frame, a balancing platform, a triaxial acceleration sensor, a force hammer, a data collector and a display. The balancing platform is suspended in the support frame by a flexible rope, and the structure to be tested is placed on the balancing platform. Several triaxial acceleration sensors are arranged on the structure to be tested according to measurement requirements. The force hammer is used to apply excitation to the structure to be tested. The triaxial acceleration sensor and the force hammer are connected to the data collector through data cables respectively. The data collector is also connected to the display to display the collected data. The balancing platform comprises a pair of platform frames which are arranged in parallel and spaced apart, the two ends of the platform frames are connected by connecting rods respectively, the upper surface of each platform frame is provided with an elongated groove which opens upward, a rotating shaft is provided in the middle of the elongated groove, and the two ends of the rotating shaft pass through the platform stretcher, the rotating shaft is connected with the platform stretcher through bearings, the two ends of the rotating shaft in the elongated groove are provided with gears respectively, the lower part of the gear is meshed with two symmetrically arranged ratchets fixed on the platform frame through ratchet shafts, a V-shaped support frame is fixed in the middle of the rotating shaft, the structure to be tested is mounted on the V-shaped support frame, the two sides of the V-shaped support frame are respectively connected with one end of the oblique support, the other end of the oblique support is connected with one end of a slider arranged in the elongated groove, the other end of the slider is connected with the platform frame through a spring, and the lower part of the ratchet is connected with the two sliders in the groove through pull wires respectively; The rotating shaft, which passes through the platform single frame, is provided with balance indicator needles at both ends respectively. The balance indicator needles rotate synchronously with the rotating shaft. The balance indicator needles can be used to determine whether the structure to be tested mounted on the V-shaped support frame is in a balanced state; The pull wire is connected to the slider via a slipknot bolt.

2. The inertial parameter measurement platform based on frequency response function mass line according to claim 1, characterized in that: The two ratchets are connected via a tension spring.

3. The inertial parameter measurement platform based on frequency response function mass line according to claim 1, characterized in that: Both ends of the platform single frame are provided with lifting ears, and the flexible rope suspends the balancing platform horizontally in the supporting frame through the four lifting ears.

4. The inertial parameter measurement platform based on frequency response function mass line according to claim 1, characterized in that: The connecting rod is connected to the platform stretcher through a fastening bolt. By adjusting the fastening position of the connecting rod and the balancing single frame, the distance between the two platform single frames can be adjusted, thereby adjusting the width of the balancing platform.

5. The measurement method of the inertial parameter measurement platform based on the frequency response function mass line according to claim 1 is characterized in that: The steps include: 1) Place the structure to be tested on the balance platform and adjust the V-shaped support frame to balance the entire test platform; 2) Place two triaxial acceleration sensors on P1 (L1 W1 H1) and P2 (L2 WH2), and set P1 as the coordinate reference point to establish a coordinate system, with the axis perpendicular to the plane where the balance platform is located as the z-axis, the direction of the connecting rod as the x-axis, and the axis perpendicular to the xz plane as the y-axis; then arrange 13 triaxial acceleration sensors on the structure to be tested, the contour formed by the position of the arrangement point of each sensor is approximately the main contour of the structure to be tested, and the area enclosed by the connection line of any three sensors is as large as possible, the measurement axes of each sensor are parallel to the three axes of the established coordinate system, and the arrangement points are prohibited from being arranged at the symmetry axis or rotation node line of the component to be tested; 3) Connect each acceleration sensor and hammer to the data collector through a data line, calibrate and debug the data collector, set the acquisition time to 10s, and remove abnormal signals; use the hammer to excite the structure to be tested, and collect data once each time the structure is stimulated. A total of 7 positions are stimulated, and each position is stimulated three times in the three-axis direction; 4) According to the signals of each acceleration sensor and hammer collected by the data acquisition device, and the acceleration value between the natural frequency of the flexible rope and the natural frequency of the structure to be tested, the average acceleration of each excitation point under three excitation responses is taken as the acceleration of the point; 5) Calculate the inertia parameters of the structure to be tested based on the collected acceleration and the excitation force applied by the hammer, as follows: 5-1) When the entire rigid body is excited When the acceleration P1 is applied, the corresponding point can measure the acceleration in three directions: (a 1 x a 1 y a 1 z ), the three-axis acceleration of P3 is (a 3 x a 3 y a 3 z ), according to the relationship between the acceleration of each point and the acceleration of the origin of the rigid body under the same excitation force, the following formula (1) is determined; The excitation force F is calculated by the three equations in formula (1): 1 The angular acceleration (α 1 β 1 γ 1 ); 5-2) Given the angular acceleration under the same excitation force and the P at any point on the structure to be tested j (L j W j H j )Three-axis acceleration sensor value (a j x a j y a j z ), according to formula (1), the coordinates of each response point of the entire structural rigid body in the direction of the response acceleration are inversely calculated, as shown in the following formula (2): 5-3) Calculate the equivalent acceleration of the center of mass of the entire structural member. Suppose the acceleration of the center of mass of the entire rigid body is (a c x a c y a c z ), the coordinates of the center of mass are (L c W c H c ),but: 5-4) Combine the rigid body center of mass motion formula and formula (3) to calculate the mass and center of mass of the entire rigid body. Suppose the mass of the entire rigid body is M c ,but: Substitute the data under at least two excitations to calculate M c and the center of mass (L c W c H c ); 5-5) According to the translational equivalent theorem of force, the moment of momentum theorem and the moment of momentum theorem of rigid body rotation about a fixed axis, the moment of inertia parameters of the entire rigid body are calculated as follows: Combining formula (5) and formula (6), solving the inertia parameters requires parameters under at least three excitations; based on the 7 excitations in step 3) and the data obtained from 15 triaxial acceleration sensor measurement points, multiple sets of data are superimposed according to the above steps to improve the accuracy of the inertia parameters; 5-6) Finally, the mass, center of mass coordinates and moment of inertia parameters of the entire rigid body are calculated. By removing the mass, center of mass coordinates and moment of inertia parameters of the known measuring platform, the mass, center of mass coordinates and moment of inertia parameters of the component to be measured are obtained.

Images