High-speed air-floating spindle modal test system based on laser shock excitation

Abstract

The application provides a high-speed air-floating spindle modal test system based on laser impact excitation, which belongs to the field of spindle modal test and comprises an air-floating vibration isolation platform, a laser, a convex lens, a laser absorption layer, a spindle test rod, a high-speed air-floating spindle, a laser vibration meter, a data acquisition system, an industrial computer and a fine adjustment device, wherein the laser, the convex lens, the high-speed air-floating spindle, the laser vibration meter, the fine adjustment device and the data acquisition system are sequentially connected to the air-floating vibration isolation platform; the high-speed air-floating spindle is provided with the spindle test rod, and the outer surface of the spindle test rod is provided with the laser absorption layer; the industrial computer is connected to the data acquisition system; the laser vibration meter is electrically connected to the data acquisition system; the data acquisition system is electrically connected to the industrial computer; and the industrial computer is electrically connected to the laser. The application realizes non-contact modal test of the high-speed air-floating spindle under different rotating speeds, which is controllable in excitation force, high in bandwidth and good in repeatability.

Description

Technical Field

[0001] This invention relates to the field of spindle modal testing, and more specifically, to a high-speed air-bearing spindle modal testing system based on laser shock excitation. Background Technology

[0002] Experimental modal analysis is an experimental analysis method that uses system input-output information to identify the inherent characteristics of a system. This technology has been widely applied in fields such as aircraft, radar satellites, automobiles, and CNC machine tools to obtain the dynamic properties (natural frequencies, damping, and mode shapes) of components or mechanical systems. Experimental modal analysis includes two stages: modal testing and modal analysis. First, modal testing is performed, typically using an excitation device (such as a force hammer) to apply excitation force to the object under test, and using vibration sensors (such as accelerometers) to acquire the vibration response signal of the structure. Then, modal analysis is performed, using digital signal processing techniques to process the excitation and response signals in the time and frequency domains, and finally extracting the system's dynamic parameters through fitting and estimation methods.

[0003] In traditional machining, experimental modal analysis is typically used to obtain the spindle's frequency response function to determine suitable machining parameters. Existing modal testing methods (such as hammer excitation and accelerometer vibration measurement) can obtain good test results for static spindles. However, as the rotational speed increases, the dynamic characteristics of the spindle change significantly, making it impossible for the statically measured spindle frequency response function to accurately predict the dynamic response of the tool during high-speed machining. Therefore, modal testing of the spindle at its operating speed is necessary. Currently reported modal tests of rotary spindles still use hammer excitation, but the vibration response measurement method has changed to non-contact, such as laser displacement sensors or laser vibrometers. Because hammer excitation is used, the hammer head needs to be in direct contact with the rotating test bar during excitation. Sliding friction exists at the contact point, and the higher the rotational speed, the longer the sliding friction distance. This introduces tangential disturbance signals during the test, reducing the signal-to-noise ratio and coherence of the measured signal, thus affecting the accuracy of the frequency response function test. Furthermore, for high-speed air-bearing spindles, the high rotational speed and low stiffness characteristics make traditional hammer excitation methods ineffective. To achieve reliable testing of the dynamics of high-speed air-bearing spindles, it is necessary to seek a non-contact excitation method with controllable excitation force, high bandwidth, and good repeatability.

[0004] Patent (application number: 202021551612.7) discloses a device for detecting the natural frequency of an object using laser excitation. It employs a laser emitter to excite the object under test and uses a fiber optic vibrometer to detect the object's vibration frequency. However, this patent neglects the interaction between the laser and the material; laser irradiation on the object's surface can damage the material. Furthermore, this patent can only be used to measure the natural frequency of structural components and cannot perform modal testing on high-speed air-bearing spindles. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the purpose of this invention is to provide a high-speed air-bearing spindle modal testing system based on laser shock excitation.

[0006] The present invention provides a high-speed air-bearing spindle modal testing system based on laser shock excitation, comprising an air-bearing vibration isolation platform, a laser, a convex lens, a laser absorption layer, a spindle test bar, a high-speed air-bearing spindle, a laser vibration meter, a data acquisition system, an industrial control computer, and a fine-tuning device. The laser, convex lens, high-speed air-bearing spindle, laser vibration meter, fine-tuning device, and data acquisition system are sequentially connected to the air-bearing vibration isolation platform.

[0007] A spindle test bar is installed on the high-speed air-bearing spindle. A laser absorption layer is provided on the outer surface of the spindle test bar. An industrial control computer is connected to a data acquisition system. A laser vibration meter is electrically connected to the data acquisition system. The data acquisition system is electrically connected to the industrial control computer. The industrial control computer is electrically connected to the laser.

[0008] The laser emits a parallel laser beam, which is then focused by a convex lens. The focal point of the focused laser beam is located on the surface of the laser absorption layer. The vibration measurement beam of the laser vibrometer is irradiated on the surface of the spindle test bar, and the dynamic signal of the spindle test bar is collected and transmitted to the data acquisition system. The data acquisition system then transmits the processed vibration signal to the industrial control computer for further processing.

[0009] Preferably, the laser absorption layer covers the outer cylindrical surface of the spindle test bar, the spindle test bar is installed at the front end of the rotor of the high-speed air-bearing spindle, the high-speed air-bearing spindle is installed on the spindle mounting base, the spindle mounting base is located on the left side of the laser support and fixed on the upper surface of the air-bearing vibration isolation platform.

[0010] Preferably, the fine-tuning device includes a Y-axis fine-tuning device, an X-axis fine-tuning device, and a Z-axis fine-tuning device. The Y-axis fine-tuning device is connected to the X-axis fine-tuning device, the X-axis fine-tuning device is connected to the Z-axis fine-tuning device, and the Z-axis fine-tuning device is connected to the upper surface of the air-bearing vibration isolation platform.

[0011] The laser vibration meter is mounted on a laser vibration meter mounting base, which is connected to the Y-axis fine-tuning device.

[0012] Preferably, the laser is mounted above the laser support, and the laser support is mounted on the upper surface of the air-bearing vibration isolation platform.

[0013] Furthermore, a lens mounting base is fixed above the laser support, located on the left side of the laser, with the convex lens installed inside the lens mounting base.

[0014] Preferably, the height of the laser and lens mount is changed by adjusting the height of the laser support;

[0015] The heights of the laser, convex lens, and laser vibrometer are adjusted using the laser support and Z-axis fine-tuning device to ensure that the center heights of the focused laser beam, the spindle test bar, and the vibration measurement beam are consistent.

[0016] Preferably, the bottom of the lens mount is equipped with a displacement adjustment function, and the position of the focal point of the focused laser beam is adjusted by the lens mount.

[0017] Preferably, the diameter of the focal point of the focused laser beam is adjusted by changing the size of the convex lens.

[0018] Preferably, the convex lens is a plano-convex lens or a biconvex lens;

[0019] The matrix material of the convex lens is calcium fluoride (CaF), borosilicate crown glass (N-BK), or ultraviolet fused silica (UVFS), and the surface of the convex lens is coated with an anti-reflective film.

[0020] Preferably, the laser absorption layer is in the shape of a cylindrical ring, and the laser absorption layer is covered on the spindle test bar by heat shrinking.

[0021] Preferably, the laser absorption layer is made of black polyvinyl chloride, polyethylene, or polyvinylidene fluoride, with a thickness of 0.1mm-0.2mm.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) The present invention can adjust the height of the laser, the convex lens and the laser vibration meter by means of the laser support and the Z-axis fine adjustment device, so as to ensure that the center height of the focused laser beam, the vibration measurement beam and the main shaft test bar are consistent. The X-axis fine adjustment device can ensure that the laser vibration meter is in the optimal measurement position.

[0024] (2) The present invention has a laser absorption layer. The laser is focused on the surface of the laser absorption layer. After the absorption layer material absorbs the laser energy, the temperature rises. After a certain degree, the material melts and vaporizes. The vaporized vapor particles continue to absorb the laser energy, and the vapor temperature continues to rise. Finally, ionization occurs, forming a high-temperature and high-density plasma. The plasma continues to absorb the laser energy, and the temperature rises further. It leaves the material surface at a certain speed and expands outward, rapidly compressing the surrounding air to form a laser-induced plasma shock wave. The recoil pressure of the shock wave forms a transient impact effect on the spindle test rod. The spindle test rod is covered by the laser absorption layer to avoid damage to the test rod by the laser. At the same time, it can also generate the impact force required for excitation.

[0025] (3) The present invention has a Y-axis fine adjustment device, and the vibration measurement beam of the laser vibrometer can move along the axis of the spindle test rod to measure the vibration response at different axial positions of the spindle test rod. Corresponding to the single-point excitation in the traditional modal test, the moving sensor picks up vibration at multiple points. By measuring the vibration response at a series of points along the axis of the test rod, more modal information of the spindle can be obtained, and the modal vibration mode of the test rod can be plotted. This enables non-contact modal testing of high-speed air-bearing spindles at different speeds with controllable excitation force, high bandwidth and good repeatability. Attached Figure Description

[0026] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0027] Figure 1 This is a global front view of a preferred embodiment of the present invention;

[0028] Figure 2 This is a partial top view of a preferred embodiment of the present invention;

[0029] Figure 3 This is a partial isometric view of a preferred embodiment of the present invention;

[0030] Figure 4 This is a partial top view of a preferred embodiment of the present invention;

[0031] The following components are labeled in the diagram: 1. Air-bearing vibration isolation platform; 2. Laser support; 3. Laser; 31. Parallel laser beam; 32. Focused laser beam; 4. Lens mounting base; 5. Convex lens; 6. Laser absorption layer; 7. Spindle test bar; 8. High-speed air-bearing spindle; 9. Spindle mounting base; 10. Laser vibration meter; 10. Measuring beam; 11. Laser vibration meter mounting base; 12. Y-axis fine-tuning device; 13. X-axis fine-tuning device; 14. Z-axis fine-tuning device; 15. Data acquisition system; 16. Industrial control computer. Detailed Implementation

[0032] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0033] Example

[0034] This invention provides a high-speed air-bearing spindle modal testing system based on laser shock excitation, such as... Figure 1-4As shown, it includes an air-bearing vibration isolation platform 1, a laser support 2, a laser 3, a lens mounting base 4, a convex lens 5, a laser absorption layer 6, a spindle test bar 7, a high-speed air-bearing spindle 8, a spindle mounting base 9, a laser vibration meter 10, a laser vibration meter mounting base 11, a Y-axis fine-tuning device 12, an X-axis fine-tuning device 13, a Z-axis fine-tuning device 14, a data acquisition system 15, and an industrial control computer 16. Laser support 2 is mounted on the upper surface of air-bearing vibration isolation platform 1. Laser 3 is mounted above laser support 2. Lens mounting base 4 is located to the left of laser 3 and fixed above laser support 2. Convex lens 5 is mounted inside lens mounting base 4. Laser 3 emits a parallel laser beam 31. After passing through convex lens 5, the parallel laser beam 31 forms a focused laser beam 32. The focal point of the focused laser beam 32 is located on the surface of laser absorption layer 6. Laser absorption layer 6 covers the outer cylindrical surface of spindle test rod 7. Spindle test rod 7 is mounted at the rotor front end of high-speed air-bearing spindle 8. High-speed air-bearing spindle 8 is mounted on spindle mounting base 9, which is located to the left of laser support 2 and fixed to air-bearing vibration isolation platform 1. The upper surface of the spindle test bar 7; the laser vibration meter 10 is located on the left side of the spindle test bar 7, and the vibration measurement beam 101 of the laser vibration meter 10 irradiates the surface of the spindle test bar 7. The laser vibration meter 10 is mounted on the laser vibration meter mounting base 11. The Y-axis fine adjustment device 12, the X-axis fine adjustment device 13 and the Z-axis fine adjustment device 14 are connected in sequence below the laser vibration meter mounting base 11. The Z-axis fine adjustment device 14 is fixed on the upper surface of the air-bearing vibration isolation platform 1; the data acquisition system 15 is located above the air-bearing vibration isolation platform 1, and the industrial control computer 16 is located above the data acquisition system 15. The laser vibration meter 10 is electrically connected to the data acquisition system 15, the data acquisition system 15 is electrically connected to the industrial control computer 16, and the industrial control computer 16 is electrically connected to the laser 3.

[0035] Working principle: Laser 3 emits pulsed laser light, which is focused by convex lens 5 onto the surface of laser absorption layer 6 covering spindle test rod 7. This induces a plasma shock wave to impact spindle test rod 7 installed at the front end of high-speed air-bearing spindle 8. The vibration response of high-speed air-bearing spindle 8 and spindle test rod 7 under the transient impact force of the laser is measured by laser vibration meter 10. The response signal is acquired by data acquisition system 15 and transmitted to industrial control computer 16 for processing to obtain the spindle frequency response function. The measurement position of laser vibration meter 10 is changed by Y-axis fine adjustment device 12, and the impact and measurement process is repeated to realize the measurement of frequency response function at different axial positions of the test rod. All frequency response functions are combined to perform modal analysis and extract modal parameters of high-speed air-bearing spindle 8.

[0036] like Figure 1 As shown, the height of laser support 2 is adjustable, and indirectly, the heights of laser 3 and lens mounting base 4 are also adjustable. Laser 3 is an Nd:YAG pulsed laser with a wavelength of 1064 nm, a pulse width on the order of nanoseconds, and a laser power density greater than 10.12 W / m 2 Furthermore, the laser power density is adjustable. The diameter of the focal point of the focused laser beam 32 is adjusted by changing the size of the convex lens 5. For example... Figure 2 As shown, convex lens 5 is a plano-convex lens or a biconvex lens. The substrate material of convex lens 5 is calcium fluoride (CaF2), borosilicate crown glass (N-BK7), or ultraviolet fused silica (UVFS), and the surface of convex lens 5 is coated with an anti-reflective coating. Figure 3 As shown, the laser absorption layer 6 is made of black polyvinyl chloride, polyethylene, or polyvinylidene fluoride, with a thickness of 0.1mm-0.2mm. The laser absorption layer 6 is a cylindrical ring shape and is heat-shrinkable onto the spindle test bar 7. The lens mounting base 4 has a displacement adjustment function at its bottom, allowing adjustment of the focal point position of the focused laser beam 32.

[0037] The high-speed air-bearing spindle modal testing system based on laser shock excitation described in the above embodiments of the present invention can realize non-contact modal testing of high-speed air-bearing spindles at different speeds with controllable excitation force, high bandwidth and good repeatability.

[0038] More specifically, refer to Figures 1-4First, the laser vibrometer 10 is electrically connected to the data acquisition system 15, and the laser 3 and the data acquisition system 15 are electrically connected to the industrial control computer 16. Then, using the laser support 2 and the Z-axis fine-tuning device 14, the heights of the laser 3, the convex lens 5, and the laser vibrometer 10 are adjusted so that the center heights of the focused laser beam 32, the vibration measurement beam 101, and the spindle test bar 7 are aligned. The X-axis fine-tuning device 13 is then adjusted to position the laser vibrometer 10 at the optimal measurement location. Simultaneously, a suitable cylindrical annular laser absorption layer 6 is selected and heat-shrinkly applied to the spindle test bar. The test bar 7 is placed on the laser. Then, the laser is turned on, and the lens mounting base 4 is adjusted so that the focal point of the focused laser beam 32 is located on the surface of the laser absorption layer 6. Next, the parameters of the laser 3 and the rotational speed of the high-speed air-bearing spindle 8 are set. The laser vibration meter 10 is turned on, and a test command is sent via the industrial control computer 16. The laser 3 emits a single pulse laser. The pulse laser passes through the convex lens 5 and irradiates the surface of the laser absorption layer 6. After absorbing the laser energy, the temperature of the absorption layer material rises. At a certain point, the material undergoes melting and vaporization. The vaporized steam particles continue to absorb laser energy, and the steam temperature will continue to rise. As the laser energy continues to rise, ionization eventually occurs, forming a high-temperature, high-density plasma. This plasma continues to absorb laser energy, further increasing its temperature, and expands outwards from the material surface at a certain speed, rapidly compressing the surrounding air to form a laser-induced plasma shock wave. The recoil pressure of this shock wave creates a transient impact effect on the spindle test rod 7. Under this impact force, the rotor, composed of the spindle test rod 7 and the high-speed air-bearing spindle 8, will produce a vibration response. This vibration response is measured by the laser vibration meter 10, and the vibration signal is transmitted to the data acquisition system 15. After hardware filtering and digital processing, the vibration... The response signal is transmitted to the industrial control computer 16, and after digital signal processing, the runout error information of the spindle test bar 7 itself is filtered out, and finally the vibration response caused only by laser excitation is obtained. On the other hand, the laser impact force signal is obtained by prior calibration. Based on the impact force signal and the vibration response signal, the spindle frequency response function can be calculated by the frequency response function calculation program written by the industrial control computer. By adjusting the Y-axis fine adjustment device 12, the frequency response function is measured at different axial positions of the test bar. Finally, by combining the frequency response functions at different positions, the modal information of the spindle can be obtained through modal parameter identification technology.

[0039] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0040] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A high-speed air-bearing spindle modal testing system based on laser shock excitation, characterized in that, The system includes an air-bearing vibration isolation platform (1), a laser (3), a convex lens (5), a laser absorption layer (6), a spindle test bar (7), a high-speed air-bearing spindle (8), a laser vibration meter (10), a data acquisition system (15), an industrial control computer (16), and a fine-tuning device. The laser (3), the convex lens (5), the high-speed air-bearing spindle (8), the laser vibration meter (10), the fine-tuning device, and the data acquisition system (15) are sequentially connected to the air-bearing vibration isolation platform (1). The high-speed air-bearing spindle (8) is provided with the spindle test bar (7), the outer surface of the spindle test bar (7) is provided with the laser absorption layer (6), the industrial control computer (16) is connected to the data acquisition system (15), the laser vibration meter (10) is electrically connected to the data acquisition system (15), the data acquisition system (15) is electrically connected to the industrial control computer (16), and the industrial control computer (16) is electrically connected to the laser (3); The laser (3) emits a parallel laser beam (31), which, after passing through the convex lens (5), forms a focused laser beam (32). The focal point of the focused laser beam (32) is located on the surface of the laser absorption layer (6), forming a laser-induced plasma shock wave, which causes the spindle test bar (7) and the high-speed air-bearing spindle (8) to vibrate. The vibration measurement beam (101) of the laser vibration meter (10) irradiates the surface of the spindle test bar (7) and transmits the vibration signal to the data acquisition system (15). The data acquisition system (15) transmits the processed vibration signal to the industrial control computer (16) for processing.

2. The high-speed air-bearing spindle modal testing system based on laser shock excitation according to claim 1, characterized in that, The laser absorption layer (6) covers the outer cylindrical surface of the spindle test bar (7). The spindle test bar (7) is installed at the front end of the rotor of the high-speed air-bearing spindle (8). The high-speed air-bearing spindle (8) is installed on the spindle mounting base (9). The spindle mounting base (9) is located on the left side of the laser support (2) and fixed on the upper surface of the air-bearing vibration isolation platform (1).

3. The high-speed air-bearing spindle modal testing system based on laser shock excitation according to claim 1, characterized in that, The fine-tuning device includes a Y-axis fine-tuning device (12), an X-axis fine-tuning device (13), and a Z-axis fine-tuning device (14). The Y-axis fine-tuning device (12) is connected to the X-axis fine-tuning device (13), the X-axis fine-tuning device (13) is connected to the Z-axis fine-tuning device (14), and the Z-axis fine-tuning device (14) is connected to the upper surface of the air-bearing vibration isolation platform (1). The laser vibration meter (10) is mounted on the laser vibration meter mounting base (11), and the laser vibration meter mounting base (11) is connected to the Y-axis fine adjustment device (12).

4. The high-speed air-bearing spindle modal testing system based on laser shock excitation according to claim 3, characterized in that, The laser (3) is mounted above the laser support (2), and the laser support (2) is mounted on the upper surface of the air-bearing vibration isolation platform (1); Furthermore, a lens mounting base (4) is fixed above the laser support (2), the lens mounting base (4) is located on the left side of the laser (3), and the convex lens (5) is installed inside the lens mounting base (4).

5. The high-speed air-bearing spindle modal testing system based on laser shock excitation according to claim 4, characterized in that, The height of the laser (3) and the lens mount (4) is changed by adjusting the height of the laser support (2); The heights of the laser (3), the convex lens (5), and the laser vibration meter (10) are adjusted by the laser support (2) and the Z-axis fine-tuning device (14) to make the center heights of the focused laser beam (32), the spindle test bar (7), and the vibration measurement beam (101) consistent.

6. The high-speed air-bearing spindle modal testing system based on laser shock excitation according to claim 4, characterized in that, The lens mounting base (4) is equipped with a displacement adjustment function at its bottom, and the position of the focal point of the focused laser beam (32) is adjusted by the lens mounting base (4).

7. The high-speed air-bearing spindle modal testing system based on laser shock excitation according to claim 1, characterized in that, The diameter of the focal point of the focused laser beam (32) is adjusted by changing the size of the convex lens (5).

8. The high-speed air-bearing spindle modal testing system based on laser shock excitation according to claim 1, characterized in that, The convex lens (5) is a plano-convex lens or a biconvex lens; The substrate material of the convex lens (5) is calcium fluoride (CaF2), borosilicate crown glass (N-BK7), or ultraviolet fused silica (UVFS), and the surface of the convex lens (5) is coated with an anti-reflective film.

9. The high-speed air-bearing spindle modal testing system based on laser shock excitation according to claim 1, characterized in that: The laser absorption layer (6) is in the shape of a cylindrical ring, and the laser absorption layer (6) is covered on the spindle test bar (7) by heat shrinking.

10. The high-speed air-bearing spindle modal testing system based on laser shock excitation according to claim 1, characterized in that: The laser absorption layer (6) is made of black polyvinyl chloride, polyethylene, or polyvinylidene fluoride, with a thickness of 0.1 mm to 0.2 mm.

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