A reaction wheel micro-vibration measurement device and method

Abstract

One technical solution of the present invention is to provide a reaction wheel micro-vibration measurement device. Another technical solution of the present invention is to provide a reaction wheel micro-vibration measurement method. With the aid of the reaction wheel micro-vibration measurement device and method, the present invention can realize real-time, standard measurement of reaction wheel micro-vibration and obtain disturbance components in six directions; through the visual detection device and three-dimensional digital image correlation technology, it can avoid the interference of the system on the measurement target and achieve good measurement accuracy; by using the optical elements and adjustment mechanism in the visual detection device, the number of high-speed cameras required in the three-dimensional image measurement is reduced, the equipment cost is effectively reduced, and the advantages of synchronous acquisition are also combined. The device and method of the present invention are not only suitable for micro-vibration measurement of reaction wheels, but can also be used for full-field modal testing of other components, and have good flexibility.

Description

Technical Field

[0001] The invention belongs to the technical field of vibration testing and relates to a reaction wheel micro-vibration measuring device and method. Background Art

[0002] As an important functional component of the satellite, the reaction wheel achieves attitude control of the entire satellite and space interference balance by changing its own angular momentum. During in-orbit operation, the reaction wheel is affected by factors such as rotor imbalance and bearing defects, which produces micro-vibrations, which will deteriorate the working environment of the equipment and cause blurred imaging of the onboard camera. The micro-vibration of the reaction wheel has the characteristics of small amplitude and wide bandwidth, which places high demands on the measurement equipment. The measurement method for micro-vibration is usually based on ground testing, which is divided into contact and non-contact.

[0003] Contact measurement completes the conversion of vibration signals into electrical signals by installing sensors. Commonly used equipment include Kistler force measurement system and seismic mass vibration measurement system. Kistler force measurement system uses four three-axis force sensors in the platform to complete the disturbance force and torque measurement of the reaction wheel. The measurement accuracy is at the millinewton level, but the equipment is expensive. The seismic mass vibration measurement system consists of a large mass block, two highly sensitive accelerometers and a spring suspension structure. The accelerometer is used to capture the vibration signal and calculate the vibration size of the reaction wheel in combination with the physical parameters of the mass block. Although the seismic mass vibration measurement system is relatively low in cost, there is an error in the center of mass position of the mass block in the three-dimensional simulation, which reduces the final measurement accuracy.

[0004] Non-contact measurement can complete static or dynamic measurement without contacting the object being measured, reducing system interference. The measurement methods include image measurement, photoelectric position sensor measurement, and laser measurement, such as the air-floating micro-vibration measurement system developed in Japan. This system uses a CCD laser sensor to collect radial vibration signals of the reaction wheel, and the measurement accuracy in a stable state can reach 10 -4 N, the disadvantage is that it can only measure low-frequency disturbance force in one direction. With the rapid development of computer and image technology, optical measurement methods combined with machine vision have been widely studied. Three-dimensional digital image correlation technology is based on the principle of binocular stereo vision. With its full-field, real-time and high-precision characteristics, it has become one of the powerful means of vibration measurement. Summary of the invention

[0005] The technical problem to be solved by the present invention is that the existing reaction wheel micro-vibration measurement device has certain interference to the measured target during measurement, does not have full-field performance, and the equipment is expensive; and the current optical measurement of reaction wheel micro-vibration has certain functional limitations, can only measure vibration in a single direction, and the equipment structure is relatively complex.

[0006] In order to solve the above technical problems, a technical solution of the present invention is to provide a reaction wheel micro-vibration measuring device, which is characterized by comprising:

[0007] Support system, the reaction wheel is fixed on the measuring plate, the measuring plate is supported by the support system, and the surface of the measuring plate is sprayed with random speckles;

[0008] The visual inspection system comprises a mounting frame, on which an annular light source, a high-speed camera, a height adjustment mechanism and two angle adjustment mechanisms are fixed; a right-angle prism reflector is arranged on the height adjustment mechanism, the right-angle prism reflector, the high-speed camera and the annular light source are located directly above the reaction wheel, and the right-angle prism reflector is located between the reaction wheel, the high-speed camera and the annular light source; a plane reflector is respectively arranged on the two angle adjustment mechanisms, and the two plane reflectors are respectively located on the left and right sides of the right-angle prism reflector; a speckle image on the surface of the measuring plate is mapped on the two plane reflectors, and the speckle image formed by the two plane reflectors is refracted to the high-speed camera through the right-angle prism reflector, so that the high-speed camera can realize the acquisition of the speckle image formed by the plane reflector, and present the speckle images of the two plane reflectors on the left and right frames of the same image;

[0009] The control processing system is used to control the operation of the reaction wheel and trigger the high-speed camera to collect speckle images in real time. The control processing system processes the feedback speckle image sequence to obtain the reaction wheel micro-vibration signal.

[0010] Preferably, the support system comprises a support frame, the bottom of the marble platform is supported on the support frame, a vibration isolator is provided between the marble platform and the support frame, a transfer fixture is provided on the top surface of the marble platform, and the measuring plate is provided on the transfer fixture.

[0011] Preferably, a camera fixing plate and an annular light source mounting plate are provided on the top of the mounting frame, and the high-speed camera and the annular light source are respectively fixed on the camera fixing plate and the light source mounting plate, and the annular light source surrounds the high-speed camera.

[0012] Preferably, the height adjustment mechanism includes a mounting plate arranged on the mounting frame, a bottom plate is provided below the mounting plate, the bottom plate is passed through a screw, one end of the screw passes through the bottom plate and is screwed into the mounting plate, a star-shaped handle is provided at the other end of the screw, sliding rods are provided on both sides of the screw, the sliding rod is fixed between the mounting plate and the bottom plate, a slider is passed through the screw and the sliding rod, the screw is rotated by rotating the star-shaped handle, thereby driving the slider to move up and down along the sliding rod, and the right-angle prism reflector is arranged on the slider; a side plate is provided on the rear side of the bottom plate, and the side plate is connected and fixed to the mounting plate.

[0013] Preferably, the angle adjustment mechanism includes a mounting block arranged on the mounting frame, the mounting block is provided with multiple rows of threaded holes, the position adjustment member is fixed to the mounting block through different threaded holes to achieve the purpose of adjusting the height above the surface, the position adjustment member is provided with an angle adjustment member with two star-shaped handles, the mirror frame is arranged on the angle adjustment member, the plane reflector is placed in the mirror frame, and the deflection angle of the plane reflector is adjusted by rotating the two star-shaped handles using the angle adjustment member.

[0014] Another technical solution of the present invention is to provide a method for measuring micro-vibration of a reaction wheel, characterized in that the above-mentioned device is used, and the method comprises the following steps:

[0015] Step 1): Use the height adjustment mechanism and the angle adjustment mechanism to adjust the right-angle prism reflector and the plane reflector to a suitable position so that the left and right views of the high-speed camera can fully present the speckle characteristics of the measurement plate, and use the Zhang Zhengyou calibration method to obtain the internal parameters and relative position parameters of the left and right views of the high-speed camera;

[0016] Step 2): Install the reaction wheel, control the reaction wheel to operate according to the measurement condition, and then trigger the high-speed camera to collect data in real time;

[0017] Step 3): Process the image sequence collected by the high-speed camera and select four initial reference points (N1, N2, N3, N4) on the measurement board. The coordinate positions of the four initial reference points in the world coordinate system are shown in the following formula (1):

[0018]

[0019] In formula (1), a is the distance from the coordinate point to the horizontal y-axis, and b is the distance from the coordinate point to the horizontal x-axis;

[0020] The reference points are mapped to the image coordinate system through the calibrated internal and external parameters, and the zero-mean normalized correlation coefficient C is calculated using the Newton-Raphson algorithm. zncc , perform a two-dimensional matching search on the reference point, and the zero-mean normalized correlation coefficient C zncc As shown in the following formula (2):

[0021]

[0022] In formula (2), f(x i ,y i ) is the image coordinates before measuring the plate vibration displacement (x i ,y i ), g(x i ,y i ) is the image coordinate after the vibration displacement of the measuring plate (x i ,y i ) gray value, fm and g m are the grayscale averages of the images before and after the vibration displacement, respectively;

[0023] Step 4): Correspond the two-dimensional image coordinates of the matching search to the world coordinate system through calibration parameters, and obtain the three-dimensional coordinates q of the four reference points at different times t n (t) = [x n (t),y n (t),z n (t)]; perform the second-order derivative of the coordinates and calculate the disturbance force F of the reference point on the three coordinate axes qn (t), as shown in the following formula (3):

[0024]

[0025] In formula (3), n is the reference point number, which is 1, 2, 3, 4; M is the mass of the measuring plate;

[0026] Step 5): Use the three-component disturbance force F of the reference point (N1, N2, N3, N4) qn (t) Calculate and obtain the six time domain components of the reaction wheel micro-vibration (F x ,F y ,F z ,M x ,M y ,M z ), as shown in the following formula (4):

[0027]

[0028] In formula (4), F x1 、F x2 、F x3 、F x4 Respectively represent the disturbance force of the reference point (N1, N2, N3, N4) on the x-axis; F y1 、F y2 、F y3 、F y4 Respectively represent the disturbance force of the reference point (N1, N2, N3, N4) on the y-axis; F z1 、F z2 、F z3 、F z4 They represent the disturbance forces of the reference points (N1, N2, N3, N4) on the z-axis respectively.

[0029] The present invention uses a reaction wheel micro-vibration measurement device and method to achieve real-time, standard measurement of reaction wheel micro-vibration and obtain disturbance components in six directions; through a visual detection device and three-dimensional digital image correlation technology, it can avoid the interference of the system on the measurement target and achieve good measurement accuracy; using optical elements and adjustment mechanisms in the visual detection device, the number of high-speed cameras required in three-dimensional image measurement is reduced, effectively reducing equipment costs, while having the advantages of synchronous acquisition. The device and method of the present invention are not only suitable for micro-vibration measurement of reaction wheels, but can also be used for full-field modal testing of other components, with good flexibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The system composition of the reaction wheel micro-vibration measuring device of the present invention;

[0031] Figure 2 It is a structural schematic diagram of the reaction wheel micro-vibration measuring device of the present invention;

[0032] Figure 3 A schematic diagram of optical elements and adjustment mechanisms in the visual inspection system of the present invention;

[0033] Figure 4 This is a flow chart of the vibration measurement method based on three-dimensional digital image correlation of the present invention;

[0034] Figure 5 Schematic diagram of the measuring plate and surface reference points of the present invention. DETAILED DESCRIPTION

[0035] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0036] like Figure 1 , 2 As shown, a reaction wheel micro-vibration measuring device provided by the present invention is composed of a support system A, a visual detection system B and a control processing system C.

[0037] Support system A includes support frame 1, vibration isolator 2, marble platform 3, transfer fixture 4 and measuring plate 5. The bottom of marble platform 3 is supported on support frame 1, and vibration isolator 2 is provided between marble platform 3 and support frame 1. Transfer fixture 4 is provided on the top surface of marble platform 3. Measuring plate 5 is fixed on marble platform 3 through transfer fixture 4 and reaction wheel D, and random speckle is sprayed on the surface.

[0038] The visual inspection system B includes a mounting frame 6, an annular light source 15, a light source mounting plate 16, a camera fixing plate 17, a high-speed camera 18, a height adjustment mechanism B1, a right-angle prism reflector 13, an angle adjustment mechanism B2 and a plane reflector 24. The mounting frame 6 is constructed and connected by an aluminum profile using angle pieces and trapezoidal bolts. The mounting frame 6 is fixed with an annular light source 15, a high-speed camera 18, a height adjustment mechanism B1 and two angle adjustment mechanisms B2. The height adjustment mechanism B1 is provided with a right-angle prism reflector 13, and the right-angle prism reflector 13, the high-speed camera 18 and the annular light source 15 are located directly above the reaction wheel D, and the right-angle prism reflector 13 is located between the reaction wheel D and the high-speed camera 18 and the annular light source 15. A plane reflector 24 is respectively provided on the two angle adjustment mechanisms B2, and the two plane reflectors 24 are respectively located on the left and right sides of the right-angle prism reflector 13. The speckle image on the surface of the measuring plate 5 is mapped onto the two plane mirrors 24. The speckle images formed by the two plane mirrors 24 are refracted to the high-speed camera 18 through the right-angle prism mirror 13, so that the high-speed camera 18 can collect the speckle image formed by the plane mirrors 24 and present the speckle images of the two plane mirrors 24 on the left and right frames of the same image.

[0039] A camera fixing plate 17 and an annular light source mounting plate 16 are provided on the top of the mounting frame 6 , and a high-speed camera 18 and an annular light source 15 are fixed on the camera fixing plate 17 and the light source mounting plate 16 respectively, and the annular light source 15 surrounds the high-speed camera 18 .

[0040] The height adjustment mechanism B1 includes a mounting plate 14 arranged on the mounting frame 6, a base plate 8 is provided below the mounting plate 14, the base plate 8 is passed through the screw 12, one end of the screw 12 passes through the base plate 8 and is screwed into the mounting plate 14, a star-shaped handle 7 is provided at the other end of the screw 12, sliding rods 9 are provided on both sides of the screw 12, the sliding rods 9 are fixed between the mounting plate 14 and the base plate 8, a slider 10 is passed through the screw 12 and the sliding rod 9, the screw 12 is rotated by rotating the star-shaped handle 7, thereby driving the slider 10 to move up and down along the sliding rod 9, and a right-angle prism reflector 13 is provided on the slider 10; a side plate 11 is provided on the rear side of the base plate 8, and the side plate 11 is connected and fixed to the mounting plate 14.

[0041] The angle adjustment mechanism B2 includes a mounting block 19 arranged on the mounting frame 6, and a plurality of rows of threaded holes are arranged on the mounting block 19. A position adjustment member 20 is fixed on the mounting block 19 through different threaded holes to achieve the purpose of adjusting the height from the surface. An angle adjustment member 21 with a star-shaped handle 22 is provided on the position adjustment member 20. A mirror frame 23 is arranged on the angle adjustment member 21, and a plane reflector 24 is placed in the mirror frame 23. The deflection angle of the plane reflector 24 is adjusted by rotating the star-shaped handle 22 and using the angle adjustment member 21.

[0042] The control processing system C includes a driving power supply 25 and a computer 26. The computer 26 is connected to the driving power supply 25 to control the operation of the reaction wheel and trigger the high-speed camera 18 to collect data in real time. The computer 26 integrates software based on a vibration measurement method related to three-dimensional digital images to process the image sequence to obtain the micro-vibration signal of the reaction wheel.

[0043] The vibration measurement method based on three-dimensional digital image correlation is as follows: Figure 4 As shown, the following steps are included:

[0044] Step 1): Use the height adjustment mechanism B1 and the angle adjustment mechanism B2 to adjust the right-angle prism reflector 13 and the plane reflector 24 to a suitable position so that the left and right views of the high-speed camera 18 can fully present the speckle characteristics of the measurement plate 5, and use the Zhang Zhengyou calibration method to obtain the internal parameters and relative position parameters of the left and right views of the high-speed camera 18;

[0045] Step 2): Install the reaction wheel D, control the reaction wheel D to operate according to the measurement condition, and then trigger the high-speed camera 18 to perform real-time acquisition;

[0046] Step 3): Process the image sequence collected by the high-speed camera 18, select four initial reference points (N1, N2, N3, N4) on the measuring board 5, and the coordinate positions of the four initial reference points in the world coordinate system are shown in the following formula (1):

[0047]

[0048] In formula (1), a is the distance from the coordinate point to the horizontal y-axis, and b is the distance from the coordinate point to the horizontal x-axis;

[0049] The reference points are mapped to the image coordinate system through the calibrated internal and external parameters, and the zero-mean normalized correlation coefficient C is calculated using the Newton-Raphson algorithm. zncc , perform a two-dimensional matching search on the reference point, and the zero-mean normalized correlation coefficient C zncc As shown in the following formula (2):

[0050]

[0051] In formula (2), f(x i ,y i ) is the image coordinates (x) of the measuring plate 5 before vibration displacement i ,y i ), g(x i ,y i ) is the image coordinate (x) of the measuring plate (5) after vibration displacement i ,y i ) gray value, f m and g mare the grayscale averages of the images before and after the vibration displacement, respectively;

[0052] Step 4): Correspond the two-dimensional image coordinates of the matching search to the world coordinate system through calibration parameters, and obtain the three-dimensional coordinates q of the four reference points at different times t n (t) = [x n (t),y n (t),z n (t)]; perform the second-order derivative of the coordinates and calculate the disturbance force F of the reference point on the three coordinate axes qn (t), as shown in the following formula (3):

[0053]

[0054] In formula (3), n is the reference point number, which is 1, 2, 3, 4; M is the mass of the measuring plate 5;

[0055] Step 5): Use the three-component disturbance force F of the reference point (N1, N2, N3, N4) qn (t) Calculate and obtain the six time domain components of the reaction wheel micro-vibration (F x ,F y ,F z ,M x ,M y ,M z ), as shown in the following formula (4):

[0056]

[0057] In formula (4), F x1 、F x2 、F x3 、F x4 Respectively represent the disturbance force of the reference point (N1, N2, N3, N4) on the x-axis; F y1 、F y2 、F y3 、F y4 Respectively represent the disturbance force of the reference point (N1, N2, N3, N4) on the y-axis; F z1 、F z2 、F z3 、F z4 They represent the disturbance forces of the reference points (N1, N2, N3, N4) on the z-axis respectively.

Claims

1. A method for measuring micro-vibration of a reaction wheel, characterized in that: The following device is used: A support system (A), a reaction wheel (D) is fixed on a measuring plate (5), the measuring plate (5) is supported by the support system (A), and a surface of the measuring plate (5) is sprayed with random speckles; The visual inspection system (B) comprises a mounting frame (6), on which a ring light source (15), a high-speed camera (18), a height adjustment mechanism (B1) and two angle adjustment mechanisms (B2) are fixed; a right-angle prism reflector (13) is arranged on the height adjustment mechanism (B1); the right-angle prism reflector (13), the high-speed camera (18) and the ring light source (15) are located directly above a reaction wheel (D); the right-angle prism reflector (13) is located between the reaction wheel (D) and the high-speed camera (18) and the ring light source (15); the two angles A plane reflector (24) is provided on each of the adjustment mechanisms (B2), and the two plane reflectors (24) are respectively located on the left and right sides of the right-angle prism reflector (13); a speckle image on the surface of the measuring plate (5) is mapped onto the two plane reflectors (24), and the speckle images formed by the two plane reflectors (24) are refracted to the high-speed camera (18) through the right-angle prism reflector (13), so that the high-speed camera (18) can collect the speckle images formed by the plane reflectors (24), and present the speckle images of the two plane reflectors (24) on the left and right frames of the same image; A control processing system (C) is used to control the operation of the reaction wheel and trigger a high-speed camera (18) to collect speckle images in real time. The control processing system (C) processes the speckle image sequence fed back to obtain a micro-vibration signal of the reaction wheel (D); The support system (A) comprises a support frame (1), the bottom of a marble platform (3) is supported on the support frame (1), a vibration isolator (2) is provided between the marble platform (3) and the support frame (1), a transfer fixture (4) is provided on the top surface of the marble platform (3), and the measuring plate (5) is provided on the transfer fixture (4); The following steps are involved: Step 1): using a height adjustment mechanism (B1) and an angle adjustment mechanism (B2) to adjust the right-angle prism reflector (13) and the plane reflector (24) to a suitable position, so that the left and right views of the high-speed camera (18) can fully present the speckle characteristics of the measuring plate (5), and using the Zhang Zhengyou calibration method to obtain the internal parameters and relative position parameters of the left and right views of the high-speed camera (18); Step 2): installing a reaction wheel (D), controlling the reaction wheel (D) to operate according to the measurement condition, and then triggering a high-speed camera (18) to perform real-time acquisition; Step 3): Process the image sequence collected by the high-speed camera (18), select four initial reference points (N1, N2, N3, N4) on the measuring board (5), and the coordinate positions of the four initial reference points in the world coordinate system are shown in the following formula (1): In formula (1), a is the distance from the coordinate point to the horizontal y-axis, and b is the distance from the coordinate point to the horizontal x-axis; The reference points are mapped to the image coordinate system through the calibrated internal and external parameters, and the zero-mean normalized correlation coefficient C is calculated using the Newton-Raphson algorithm. zncc , perform a two-dimensional matching search on the reference point, and the zero-mean normalized correlation coefficient C zncc As shown in the following formula (2): In formula (2), f(x i ,y i ) is the image coordinate (x) of the measuring plate (5) before vibration displacement i ,y i ), g(x i ,y i ) is the image coordinate (x) of the measuring plate (5) after vibration displacement i ,y i ) gray value, f m and g m are the grayscale averages of the images before and after the vibration displacement, respectively; Step 4): Correspond the two-dimensional image coordinates of the matching search to the world coordinate system through calibration parameters, and obtain the three-dimensional coordinates q of the four reference points at different times t n (t) = [x n (t),y n (t),z n (t)]; perform the second-order derivative of the coordinates and calculate the disturbance force F of the reference point on the three coordinate axes qn (t), as shown in the following formula (3): In formula (3), n is the reference point number, which is 1, 2, 3, 4; M is the mass of the measuring plate (5); Step 5): Use the three-component disturbance force F of the reference point (N1, N2, N3, N4) qn (t) Calculate and obtain the six time domain components of the reaction wheel micro-vibration (F x ,F y ,F z ,M x ,M y ,M z ), as shown in the following formula (4): In formula (4), F x1 、F x2 、F x3 、F x4 Respectively represent the disturbance force of the reference point (N1, N2, N3, N4) on the x-axis; F y1 、F y2 、F y3 、F y4 Respectively represent the disturbance force of the reference point (N1, N2, N3, N4) on the y-axis; F z1 、F z2 、F z3 、F z4 They represent the disturbance forces of the reference points (N1, N2, N3, N4) on the z-axis respectively.

Images