Modal parameter measuring device and method

Abstract

The invention discloses a modal parameter measuring device and method, the device comprises a measuring device body and an excitation rod, the excitation rod passes through one side surface of the measuring device body, the measuring device body is detachably connected with a measured device, and the excitation rod reciprocates relative to the measuring device body to apply an excitation force to the measured device; a force sensor is arranged at one end, in contact with the tested equipment, of the excitation rod and is used for measuring excitation force; the measuring device body is also fixedly connected with an acceleration sensor which is used for measuring a vibration acceleration signal of the measured equipment. According to the measurement method, excitation force is applied to a measured device by using motor driving, so that a measured object generates response displacement and response acceleration, and a frequency response curve is obtained through combination of excitation frequency and response displacement. Meanwhile, the excitation frequency is changed to scan and obtain a frequency response function curve within a certain frequency range, and equipment modal parameters are obtained through calculation. According to the invention, the modal measurement efficiency can be effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of modal parameter measurement of general equipment, and in particular to a modal parameter measurement device and method. Background Art

[0002] After general equipment is designed and manufactured, it is usually necessary to measure its modal parameters to evaluate its modal parameters such as stiffness and damping, so as to assess its anti-vibration performance. If its anti-vibration performance is poor, it will cause vibration during operation, which will significantly affect the accuracy of the equipment.

[0003] Existing equipment usually uses the hammer method or vibration tester to measure its modal parameters. The hammer method uses a force hammer to hammer the device being measured. Its advantages are that the force hammer is small in size and flexible in operation, but its disadvantage is that manual operation is inefficient. During the measurement process, people need to use a force hammer to perform hammer tests on the equipment multiple times and take the average value of its response to obtain its frequency response function and manually calculate its modal parameters. The theoretical calculation requirements for testers are high, and multiple manual measurements are inefficient. Existing vibration testers are usually desktop devices with large sizes. The advantages are that the excitation is automatic and the efficiency is improved. The disadvantage is that it is limited by the size of the workbench, and it is difficult to test large equipment. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a modal parameter measuring device and method, which applies an excitation force to a workpiece to be measured by driving an excitation hammer with a motor, measures the response displacement or response acceleration of the measured device, obtains its frequency response curve, and solves and obtains its modal parameters, thereby achieving the purpose of measuring the modal parameters of general equipment.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A modal parameter measuring device, comprising: a measuring device body and an excitation rod, wherein the excitation rod passes through a side surface of the measuring device body, the measuring device body is detachably connected to a device under test, and the excitation rod reciprocates relative to the measuring device body to apply an excitation force to the device under test;

[0007] A force sensor is provided at the end of the excitation rod that contacts the device under test, for measuring the magnitude of the excitation force; an acceleration sensor is also fixedly connected to the measuring device body, for measuring the vibration acceleration signal of the device under test.

[0008] To optimize the above technical solutions, the specific measures taken also include:

[0009] Furthermore, a motor is provided inside the measuring device body, and the rotation of the motor drives the excitation rod to reciprocate relative to the measuring device body.

[0010] Furthermore, the rotating shaft of the motor is connected to a cam through a connecting piece, the circumferential dimensions of the cam are inconsistent, a circular joint is provided at the end of the excitation rod away from the device under test, the outer edge of the circular joint contacts the outer edge of the cam, and a connecting rod perpendicular to the excitation rod is also provided in the middle section of the excitation rod, the two ends of the connecting rod are connected to the inner surface of the measuring device body through a spring, the rotation of the cam drives the movement stroke of the circular joint to change, and when the highest point of the cam contacts the circular joint, it drives the excitation rod to excite the device under test; the spring is used to reset the excitation rod.

[0011] Furthermore, a control module is also provided inside the measuring device body, and the control module is connected to the motor via a connecting wire, and the control module controls the rotation speed of the motor.

[0012] Furthermore, a suction cup, a guide sleeve and a lifting ring are provided on the outer surface of the measuring device body. The measuring device body is hoisted to the surface of the measured device through the lifting ring and adsorbed to the surface of the measured device through the suction cup. The guide sleeve is used to guide the reciprocating motion of the excitation rod.

[0013] The present invention also provides a modal parameter measurement method based on the modal parameter measurement device, comprising the following steps:

[0014] S1. The modal parameter measurement device is detachably connected to the surface of the device under test;

[0015] S2, the excitation rod applies an excitation force to the device under test;

[0016] S3, measuring the vibration acceleration of the device under test and the excitation force applied by the excitation rod respectively through an acceleration sensor and a force sensor;

[0017] S4, changing the frequency of the excitation force applied by the excitation rod in an incremental manner to obtain the excitation force and vibration acceleration at different frequencies;

[0018] S5. The frequency response acceleration curve under the action of unit force is obtained by the ratio of vibration acceleration to excitation force; the abscissa is the frequency range of the applied excitation force, and the ordinate is the real part of the vibration acceleration of the device under test; the frequency response acceleration curve is the real part curve of the acceleration frequency response function;

[0019] S6. Draw an imaginary part curve of the acceleration frequency response function according to the response delay;

[0020] S7. Analyze the real part curve and the imaginary part curve of the acceleration frequency response function to obtain the first-order natural frequency, damping ratio and stiffness of the device under test.

[0021] To optimize the above technical solutions, the specific measures taken also include:

[0022] Furthermore, S6 is specifically:

[0023] The expression of the excitation force is F=F1*sin(ωt+φ1), and the expression of the vibration acceleration is A=a*sin(ωt+φ2), where F represents the excitation force, F1 represents the peak value of the excitation force, ω represents the frequency, t represents the time, φ1 represents the phase of the excitation force, A represents the vibration acceleration, a represents the peak value of the vibration acceleration, φ2 represents the phase of the vibration acceleration, φ2-φ1 is the phase difference between the excitation force and the vibration acceleration, and the imaginary part of the acceleration frequency response function is obtained by calculating the phase difference.

[0024] Further, in S7, the expression of the real part curve of the acceleration frequency response function is:

[0025]

[0026] Where G(w) represents the real part of the acceleration frequency response function, w n is the natural frequency of the equipment, w is the frequency at each point on the curve, k is the stiffness at the measurement position, and e is the damping ratio;

[0027] The expression of the imaginary part curve of the acceleration frequency response function is:

[0028]

[0029] Where, H(w) represents the imaginary part of the acceleration frequency response function;

[0030] S7 specifically includes:

[0031] Analyze the real part curve of the acceleration frequency response function to obtain the peak and trough of the first waveform of the real part curve of the acceleration frequency response function. The coordinates of the peak are point 1 (ω1, a1), w1 represents the frequency corresponding to point 1, a1 represents the acceleration corresponding to point 1, and the coordinates of the trough are point 2 (ω2, a2); ω2 represents the frequency corresponding to point 2, and a2 represents the acceleration corresponding to point 2;

[0032] Analyze the imaginary part curve of the acceleration frequency response function and obtain the first trough of the imaginary part curve of the acceleration frequency response function. The coordinates of the trough are point 3 (ω3, a3). The frequency ω3 at point 3 is the first-order natural frequency of the device under test, and the damping ratio e is

[0033]

[0034] Substituting the first-order natural frequency ω3 and the damping ratio e into the expression of the imaginary part curve of the acceleration frequency response function, the stiffness k of the device under test at the measuring position is obtained.

[0035] The beneficial effects of the present invention are as follows: the measuring device and the measuring method of the present invention utilize a motor drive to apply an excitation force to the device under test, so that the object under test generates a response displacement and a response acceleration, and a frequency response curve is obtained by combining the excitation frequency and the response displacement. At the same time, the excitation frequency is changed to scan and obtain a frequency response function curve within a certain frequency range, and the device modal parameters are obtained by calculation. This method can realize the acquisition of the frequency response function curve within a certain frequency range, and the present invention can effectively improve the efficiency of modal measurement and meet the needs of modal measurement of large equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 is a flow chart of a specific embodiment of the measurement method of the present invention;

[0037] Figure 2 It is a schematic diagram of the installation of the measuring device of the present invention;

[0038] Figure 3 It is a schematic diagram of the internal structure of the measuring device of the present invention from a side view;

[0039] Figure 4 A top view of the measuring device of the present invention;

[0040] FIG5 is a schematic diagram of an acceleration frequency response curve obtained by the present invention; Figure 5a is the real part curve of acceleration frequency response, Figure 5b It is the imaginary part curve of acceleration frequency response.

[0041] Reference numerals in the accompanying drawings: equipment under test 1, lifting ring 2, measuring device body 3, motor 4, suction cup 5, guide sleeve 6, force sensor 7, excitation rod 8, connecting wire 9, control module 10, acceleration sensor 11, connecting part 12, housing 13, spring 14, connecting rod 15, circular joint 16, cam 17. DETAILED DESCRIPTION

[0042] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0043] Embodiment 1

[0044] A modal parameter measuring device, comprising: a measuring device body 3 and an excitation rod 8, wherein the excitation rod 8 passes through a side surface of the measuring device body 3, the measuring device body 3 is detachably connected to a device under test, and the excitation rod 8 reciprocates relative to the measuring device body 3 to apply an excitation force to the device under test;

[0045] A force sensor 7 is provided at the end of the excitation rod 8 that contacts the device under test. The force sensor 7 is installed in the groove at the end of the excitation rod 8 and is used to measure the magnitude of the excitation force. The measuring device body 3 is also fixedly connected with an acceleration sensor 11, which is used to measure the vibration acceleration signal of the device under test. The head of the excitation rod 8 that contacts the device under test 1 can be replaced and can be replaced with metal, rubber or other materials according to the requirements of the object under test.

[0046] See also Figure 3 and Figure 4 A motor 4 is provided inside the measuring device body 3 , and the motor 4 is fixed to the measuring device housing 13 by screws. The rotation of the motor 4 drives the excitation rod 8 to reciprocate relative to the measuring device body 3 .

[0047] The rotating shaft of the motor 4 is connected to a cam 17 through a connector 12. The circumferential dimensions of the cam 17 are inconsistent. A circular joint 16 is provided at one end of the excitation rod 8 away from the device under test. The circular joint 16 and the excitation rod 8 are connected as a whole through threads. The outer edge of the circular joint 16 contacts the outer edge of the cam 17. The middle section of the excitation rod 8 is also provided with a connecting rod 15 perpendicular to the excitation rod 8. The two ends of the connecting rod 15 are connected to the inner surface of the measuring device body 3 through a spring 14. The rotation of the cam 17 drives the movement stroke of the circular joint 16 to change. When the highest point of the cam 17 contacts the circular joint 16, it drives the excitation rod 8 to excite the device under test. The spring 14 is used to reset the excitation rod 8.

[0048] A control module 10 is further disposed inside the measuring device body 3 . The control module 10 is connected to the motor 4 via a connecting wire 9 . The control module 10 controls the rotation speed of the motor 4 .

[0049] The outer surface of the measuring device body 3 is provided with a guide sleeve 6, and the guide sleeve 6 is used to guide the reciprocating motion of the excitation rod 8. The outer surface of the measuring device body 3 is also provided with a suction cup 5 and a lifting ring 2, such as Figure 2 As shown, the measuring device body 3 is hoisted to the surface of the device under test through the lifting ring 2, and is adsorbed to the surface of the device under test through the suction cup 5. The four suction cups 5 are based on the pneumatic adsorption principle, and the measuring device 3 is connected to the device under test 1. Since the suction cup 5 connects the device under test 1 and the measuring device body 3 as a whole, the acceleration sensor 11 is fixed on the housing 13. When the device under test 1 vibrates, the measuring device body 3 and the device under test 1 will vibrate together, and the acceleration sensor 11 can measure the vibration acceleration signal of the device under test 1.

[0050] Embodiment 2

[0051] A modal parameter measurement method based on the modal parameter measurement device described in Example 1, the flow chart is as follows Figure 1 As shown, the following steps are included:

[0052] S1. The modal parameter measurement device is detachably connected to the surface of the device under test;

[0053] S2, the excitation rod 8 applies an excitation force to the device under test;

[0054] S3, respectively measuring the vibration acceleration of the device under test and the excitation force applied by the excitation rod 8 by means of an acceleration sensor and a force sensor;

[0055] S4, changing the frequency of the excitation force applied by the excitation rod 8 in an incremental manner to obtain the excitation force and vibration acceleration at different frequencies;

[0056] S5. The frequency response acceleration curve under the action of unit force is obtained by the ratio of vibration acceleration to excitation force; the abscissa is the frequency range of the applied excitation force, and the ordinate is the real part of the vibration acceleration of the device under test; the frequency response acceleration curve is the real part curve of the acceleration frequency response function; Figure 5a shown.

[0057] S6. Draw the imaginary part curve of the acceleration frequency response function according to the response delay. The expression of the excitation force is F=F1*sin(ωt+φ1), and the expression of the vibration acceleration is A=a*sin(ωt+φ2). In the formula, F represents the excitation force, F1 represents the peak value of the excitation force, ω represents the frequency, t represents the time, φ1 represents the phase of the excitation force, A represents the vibration acceleration, a represents the peak value of the vibration acceleration, φ2 represents the phase of the vibration acceleration, φ2-φ1 is the phase difference between the excitation force and the vibration acceleration, and the imaginary part of the acceleration frequency response function is obtained by calculating the phase difference. Figure 5b shown.

[0058] S7. Analyze the real part curve and the imaginary part curve of the acceleration frequency response function to obtain the first-order natural frequency, damping ratio and stiffness of the device under test.

[0059] According to the calculation formula of displacement frequency response function,

[0060] The acceleration frequency response function is obtained as

[0061] Where w is the frequency at that point on the curve, w n is the natural frequency of the equipment, k is the stiffness at the measurement position, and e is the damping ratio.

[0062] Among them, the real part and imaginary part of the acceleration frequency response function are:

[0063]

[0064] Where G(w) represents the real part of the acceleration frequency response function, w nis the natural frequency of the equipment, w is the frequency at each point on the curve, k is the stiffness at the measurement position, and e is the damping ratio; H(w) represents the imaginary part of the acceleration frequency response function.

[0065] Analyze the real part curve of the acceleration frequency response function to obtain the peak and trough of the first waveform of the real part curve of the acceleration frequency response function. The coordinates of the peak are point 1 (ω1, a1), w1 represents the frequency corresponding to point 1, a1 represents the acceleration corresponding to point 1, and the coordinates of the trough are point 2 (ω2, a2); ω2 represents the frequency corresponding to point 2, and a2 represents the acceleration corresponding to point 2;

[0066] Analyze the imaginary part curve of the acceleration frequency response function and obtain the first trough of the imaginary part curve of the acceleration frequency response function. The coordinates of the trough are point 3 (ω3, a3). The frequency ω3 at point 3 is the first-order natural frequency of the device under test, and the damping ratio e is

[0067]

[0068] Substituting the first-order natural frequency ω3 and the damping ratio e into the expression of the imaginary part curve of the acceleration frequency response function, the stiffness k of the device under test at the measuring position is obtained.

[0069] According to this method, the second, third, ... N-order natural frequencies, damping ratios and stiffnesses can be obtained.

[0070] The terms such as "upper", "lower", "left", "right", "front", "back", etc. used in the present invention are only for the convenience of description and are not intended to limit the scope of the present invention. Changes or adjustments to their relative relationships should be regarded as within the scope of the present invention without substantially changing the technical content.

[0071] The above are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should be regarded as the protection scope of the present invention.

Claims

1. A modal parameter measurement device, characterized in that: include: A measuring device body (3) and an excitation rod (8), wherein the excitation rod (8) passes through a side surface of the measuring device body (3), the measuring device body (3) is detachably connected to the device under test, and the excitation rod (8) reciprocates relative to the measuring device body (3) to apply an excitation force to the device under test; A force sensor (7) is provided at the end of the excitation rod (8) contacting the device under test, for measuring the magnitude of the excitation force; an acceleration sensor (11) is also fixedly connected to the measuring device body (3), for measuring the vibration acceleration signal of the device under test.

2. The modal parameter measuring device according to claim 1, characterized in that: A motor (4) is arranged inside the measuring device body (3), and the rotation of the motor (4) drives the excitation rod (8) to reciprocate relative to the measuring device body (3).

3. The modal parameter measuring device according to claim 2, characterized in that: The rotating shaft of the motor (4) is connected to a cam (17) via a connecting piece (12). The circumferential dimensions of the cam (17) are inconsistent. A circular joint (16) is provided at one end of the excitation rod (8) away from the device under test. The outer edge of the circular joint (16) contacts the outer edge of the cam (17). A connecting rod (15) perpendicular to the excitation rod (8) is also provided in the middle section of the excitation rod (8). Both ends of the connecting rod (15) are connected to the inner surface of the measuring device body (3) via a spring (14). The rotation of the cam (17) drives the movement stroke of the circular joint (16) to change. When the highest point of the cam (17) contacts the circular joint (16), the excitation rod (8) is driven to excite the device under test. The spring (14) is used to reset the excitation rod (8).

4. The modal parameter measuring device according to claim 2, characterized in that: A control module (10) is also provided inside the measuring device body (3); the control module (10) is connected to the motor (4) via a connecting wire (9); and the control module (10) controls the rotation speed of the motor (4).

5. The modal parameter measuring device according to claim 1, characterized in that: The outer surface of the measuring device body (3) is provided with a suction cup (5), a guide sleeve (6) and a lifting ring (2); the measuring device body (3) is hoisted to the surface of the device to be measured via the lifting ring (2) and is adsorbed to the surface of the device to be measured via the suction cup (5); the guide sleeve (6) is used to guide the reciprocating motion of the excitation rod (8).

6. A modal parameter measurement method based on the modal parameter measurement device according to claim 1, characterized in that: The following steps are involved: S1. The modal parameter measurement device is detachably connected to the surface of the device under test; S2, the excitation rod (8) applies an excitation force to the device under test; S3, measuring the vibration acceleration of the device under test and the excitation force applied by the excitation rod (8) respectively by means of an acceleration sensor and a force sensor; S4, changing the frequency of the excitation force applied by the excitation rod (8) in an incremental manner to obtain the excitation force and vibration acceleration at different frequencies; S5. The frequency response acceleration curve under the action of unit force is obtained by the ratio of vibration acceleration to excitation force; the abscissa is the frequency range of the applied excitation force, and the ordinate is the real part of the vibration acceleration of the device under test; the frequency response acceleration curve is the real part curve of the acceleration frequency response function; S6. Draw an imaginary part curve of the acceleration frequency response function according to the response delay; S7. Analyze the real part curve and the imaginary part curve of the acceleration frequency response function to obtain the first-order natural frequency, damping ratio and stiffness of the device under test.

7. The modal parameter measurement method according to claim 6, characterized in that: S6 is specifically: The expression of the excitation force is F=F1*sin(ωt+φ1), and the expression of the vibration acceleration is A=a*sin(ωt+φ2), where F represents the excitation force, F1 represents the peak value of the excitation force, ω represents the frequency, t represents the time, φ1 represents the phase of the excitation force, A represents the vibration acceleration, a represents the peak value of the vibration acceleration, φ2 represents the phase of the vibration acceleration, φ2-φ1 is the phase difference between the excitation force and the vibration acceleration, and the imaginary part of the acceleration frequency response function is obtained by calculating the phase difference.

8. The modal parameter measurement method according to claim 6, characterized in that: In S7, the expression of the real part curve of the acceleration frequency response function is: Where G(w) represents the real part of the acceleration frequency response function, w n is the natural frequency of the equipment, w is the frequency at each point on the curve, k is the stiffness at the measurement position, and e is the damping ratio; The expression of the imaginary part curve of the acceleration frequency response function is: Where, H(w) represents the imaginary part of the acceleration frequency response function; S7 specifically includes: Analyze the real part curve of the acceleration frequency response function to obtain the peak and trough of the first waveform of the real part curve of the acceleration frequency response function. The coordinates of the peak are point 1 (ω1, a1), w1 represents the frequency corresponding to point 1, a1 represents the acceleration corresponding to point 1, and the coordinates of the trough are point 2 (ω2, a2); ω2 represents the frequency corresponding to point 2, and a2 represents the acceleration corresponding to point 2; Analyze the imaginary part curve of the acceleration frequency response function and obtain the first trough of the imaginary part curve of the acceleration frequency response function. The coordinates of the trough are point 3 (ω3, a3). The frequency ω3 at point 3 is the first-order natural frequency of the device under test, and the damping ratio e is Substituting the first-order natural frequency ω3 and the damping ratio e into the expression of the imaginary part curve of the acceleration frequency response function, the stiffness k of the device under test at the measuring position is obtained.

Images