A device and method for testing the dynamic performance of a pendulum based on a laser heterodyne interferometer

Abstract

This invention discloses a device and method for testing the dynamic performance of a pendulum based on a laser heterodyne interferometer. The pendulum driving module of this invention applies a dynamic acceleration signal with adjustable amplitude and frequency to the clamping fixture and the pendulum under test via piezoelectric ceramics. Then, the dynamic displacement response of the clamping fixture and the pendulum under test is simultaneously detected through the heterodyne interferometry optical path. Next, the theoretical displacement signal of the pendulum under test driven by the piezoelectric ceramics and the actual displacement signals of the clamping fixture and the pendulum under test are obtained through a signal acquisition system. Finally, signal processing and data comparison are performed by a terminal computer to obtain the dynamic response characteristics of the pendulum under test under applied excitation within and outside the bandwidth and range. The device of this invention is simple and reliable, has a wide measurement range, extremely high testing accuracy, and strong anti-electromagnetic interference capability.

Description

Technical Field

[0001] This invention belongs to the field of quartz accelerometer sensors, and in particular relates to a device and method for testing the dynamic performance of a pendulum based on a laser heterodyne interferometer. Background Technology

[0002] Quartz flexural accelerometers are high-precision sensors used to measure linear acceleration. They are small in size, low in power consumption, and highly sensitive, playing a significant role in inertial navigation systems. A quartz accelerometer mainly consists of upper and lower torque converters, a pendulum assembly, and a servo circuit. Among these, the quartz pendulum plate in the pendulum assembly serves as the sensitive core component of the quartz flexural accelerometer, sensing acceleration. With the development of science and technology, the demand for high-performance quartz accelerometers is increasing, which also places higher demands on the reliability of the quartz pendulum plate. Therefore, research on quartz pendulum plate quality testing technology has become an urgent task.

[0003] Traditional methods for testing quartz pendulums involve static measurement, which calculates the pendulum's stiffness based on Hooke's theorem by determining the force applied to the pendulum's mass and the resulting displacement. This method requires precise mounting of the pendulum and a strict measurement environment because the flexible beam of the quartz pendulum has low stiffness and will exhibit significant displacement under gravity, making it susceptible to external interference. Furthermore, this contact-based measurement approach suffers from significant errors when using measuring tools such as vernier calipers and microscopes, which can easily scratch the pendulum's surface.

[0004] Currently, non-contact measurement methods utilizing electrical and optical sensors have become a hot research topic due to their high detection accuracy, high efficiency, and avoidance of surface scratches during measurement. Compared to static measurement methods, which have strict requirements for environment and mounting, methods that use external excitation (such as air blowing excitation) to induce corresponding displacement in the pendulum not only reduce measurement errors and decrease the dependence of testing on the environment, but also allow for better study of the dynamic characteristics of the quartz pendulum, enabling a more comprehensive and accurate evaluation of the quartz pendulum's quality and performance. Summary of the Invention

[0005] To address the current need for dynamic performance verification and production testing of high-quality quartz pendulums using high-sensitivity quartz accelerometers, such as the need for non-contact dynamic testing of minute displacements generated by the frequency characteristics and sensitive acceleration input of high-performance quartz pendulums, this invention aims to provide a device and method for testing the dynamic performance of pendulums based on a laser heterodyne interferometer. This invention enables rapid and accurate testing of high-performance quartz pendulums with a simple device structure, providing a comprehensive and intuitive dynamic performance evaluation within the range and bandwidth of the quartz pendulum.

[0006] The technical solution adopted in this invention is as follows:

[0007] I. A test device for the dynamic performance of a pendulum based on a laser heterodyne interferometer

[0008] Clamping fixture, used to mount the test pendulum;

[0009] The pendulum drive module is used to place the clamping fixture on which the pendulum to be tested is mounted and to drive the clamping fixture and the pendulum to be tested to move simultaneously based on the drive signal.

[0010] The heterodyne interferometry optical path is used to generate two measurement beams and apply the two measurement beams to the clamping fixture and the pendulum under test respectively to generate corresponding reflected beams. After collecting the reflected beams from the clamping fixture and the pendulum under test, two beat frequency signals are generated.

[0011] The signal processing module is used to generate the dynamic response characteristics of the pendulum under test based on the drive signal from the pendulum drive module and two beat frequency signals.

[0012] The swing plate driving module includes:

[0013] The piezoelectric ceramic is installed in the displacement platform and is used to install the clamping fixture. The signal generator is electrically connected to the piezoelectric ceramic via a voltage amplifier. The displacement platform is used to adjust the position of the clamping fixture and the pendulum under test, so that the measurement beam is incident on the clamping fixture and the pendulum under test, and the reflected beams of the clamping fixture and the pendulum under test return to the heterodyne interferometry measurement optical path.

[0014] The displacement platform includes a manually operated three-axis displacement platform and an electrically operated two-dimensional displacement platform connected together. The electrically operated two-dimensional displacement platform is used to adjust the height and horizontal position of the pendulum to be measured, and the manually operated three-axis displacement platform is used to adjust the exit direction of the reflected beam of the clamping fixture and the pendulum to be measured, so that the reflected beam is incident into the heterodyne interferometry measurement optical path.

[0015] The heterodyne interferometry optical path includes:

[0016] Two light signals (i.e., measurement beams) emitted from the light signal generation unit enter the measurement arm unit and the reference arm unit, respectively. The measurement arm unit divides the incoming light signals into a first light signal and a second light signal. The first light signal emitted from the measurement arm unit is incident on the pendulum under test. The light signal reflected by the pendulum under test then passes through the measurement arm unit and enters the first reference arm assembly of the reference arm unit. The second light signal emitted from the measurement arm unit is incident on the clamping fixture. The light signal reflected by the clamping fixture then passes through the measurement arm unit and enters the second reference arm assembly of the reference arm unit. The reference arm unit divides the incoming light signals into a third light signal and a fourth light signal. The first reference arm assembly combines the third light signal and the light signal reflected by the pendulum under test to generate a first beat frequency signal and sends it to the signal processing module. The second reference arm assembly combines the fourth light signal and the light signal reflected by the clamping fixture to generate a second beat frequency signal and sends it to the signal processing module.

[0017] The measuring arm unit includes a second acousto-optic modulator, a second ordinary beam splitter, a third polarizing beam splitter, a second polarizing beam splitter, a third quarter-wave plate, and a second quarter-wave plate. A beam of light emitted from the first polarizing beam splitter of the light signal generation unit is incident on the second ordinary beam splitter after passing through the second acousto-optic modulator. The first and second light signals generated by the second ordinary beam splitter are incident on the third and second polarizing beam splitters, respectively. The first light signal from the third polarizing beam splitter is incident on the test pendulum after passing through the third quarter-wave plate. The light signal reflected by the test pendulum is then incident on the fourth ordinary beam splitter of the first reference arm assembly after passing through the third quarter-wave plate and the third polarizing beam splitter. The first light signal from the second polarizing beam splitter is incident on the clamping fixture after passing through the second quarter-wave plate. The light signal reflected by the clamping fixture is then incident on the third ordinary beam splitter of the second reference arm assembly after passing through the second quarter-wave plate and the second polarizing beam splitter.

[0018] The reference arm unit includes a first acousto-optic modulator, a first ordinary beam splitter, a fourth ordinary beam splitter, a third ordinary beam splitter, a second photodetector, and a first photodetector. A beam of light emitted from the first polarization beam splitter of the light signal generation unit is incident on the first ordinary beam splitter after passing through the first acousto-optic modulator. The first light signal generated by the first ordinary beam splitter and the light signal reflected from the test plate emitted from the third polarization beam splitter of the measurement arm unit are combined by the fourth ordinary beam splitter to generate a first beat frequency signal. The first beat frequency signal is collected by the second photodetector. The second light signal generated by the first ordinary beam splitter and the light signal reflected from the clamping fixture emitted from the second polarization beam splitter of the measurement arm unit are combined by the third ordinary beam splitter to generate a second beat frequency signal, which is collected by the first photodetector.

[0019] The optical signal generation unit includes a laser, a first quarter-wave plate, a first half-wave plate, and a first polarizing beam splitter arranged sequentially along the optical axis. The optical signal emitted from the first half-wave plate enters the first polarizing beam splitter and is reflected and transmitted, thereby emitting two optical signals.

[0020] The clamping fixture includes two flat plates, each with a swing plate mounting hole.

[0021] II. A method for testing the dynamic performance of a pendulum based on a laser heterodyne interferometer

[0022] S1: The pendulum to be tested is mounted on the clamping fixture. The pendulum driving module generates a dynamic acceleration signal and applies it to the clamping fixture and the pendulum to be tested, so that the pendulum to be tested and the clamping fixture produce periodic small displacements under the operation of the pendulum driving module.

[0023] S2: The heterodyne interferometry optical path detects the beat frequency signal corresponding to the test pendulum and the clamping fixture. The signal processing module calculates the actual displacement of the test pendulum tongue and the clamping fixture based on the collected beat frequency signal.

[0024] S3: The signal processing module calculates the theoretical displacement of the clamping fixture based on the voltage signal output from the swing plate drive module, and a displacement response is composed of two actual displacements and the theoretical displacement.

[0025] S4: Change the amplitude and frequency of the dynamic acceleration signal of the pendulum under test, repeat S1-S3 multiple times, obtain several displacement responses and form a set of displacement responses, and then generate the dynamic response characteristics of the pendulum under test to the applied dynamic acceleration signal within the working frequency and range.

[0026] In step S2, the signal processing module calculates the actual displacement of the pendulum tongue and the clamping fixture based on the acquired beat frequency signal, including:

[0027] In the signal processing module, the actual displacement of the pendulum tongue of the pendulum under test is obtained after phase-locked processing of the beat frequency signal of the pendulum under test; and the actual displacement of the clamping fixture is obtained after phase-locked processing of the beat frequency signal of the clamping fixture.

[0028] The beneficial effects of this invention are as follows:

[0029] 1. This invention provides a device and method for testing the vibration characteristics of a pendulum. The invention utilizes piezoelectric ceramics and a heterodyne interferometry optical path to construct a simple and reliable measurement device. During the test, the amplitude and frequency of the acceleration signal can be freely adjusted, resulting in extremely high testing accuracy and strong resistance to electromagnetic interference. This allows for batch testing of the vibration characteristics of pendulums.

[0030] 2. The testing device of this invention is performed on an optical platform, with a simple structure that is easy to assemble. The optical measurement method proposed in this invention can achieve high-precision non-destructive testing of a pendulum, and can directly detect the dynamic response characteristics of each position on the pendulum under external excitation. Furthermore, it offers a wide testing frequency and measurement range, which can be precisely controlled. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the overall structure of the pendulum dynamic performance testing device.

[0032] Figure 2 This is a schematic diagram of the optical path for heterodyne interferometry.

[0033] Figure 3 This is a structural diagram of the pendulum drive module. Figure 1 .

[0034] Figure 4 This is a structural diagram of the pendulum drive module. Figure 2.

[0035] Figure 5 This is a structural diagram of the clamping fixture.

[0036] Figure 6 This is a schematic diagram of the structure of a quartz pendulum.

[0037] Figure 7 This is a flowchart of signal demodulation.

[0038] Figure 8 This is the result of calibrating the output displacement of the piezoelectric ceramic using a heterodyne interferometry optical path.

[0039] In the diagram: 1. Signal generator; 2. Voltage amplifier; 3. Piezoelectric ceramic; 4. Manual three-axis displacement platform; 5. Electric two-dimensional displacement platform; 6. Optical platform; 7. Clamping fixture; 8. Test plate; 9. Signal acquisition system; 10. Heterodyne interferometry optical path; 11. Adapter fixture; 12. Terminal computer. 111. Right-angle bracket; 112. Optical breadboard; 101. Laser; 102. First quarter-wave plate; 103. First half-wave plate; 104. First polarizing beam splitter; 105. First acousto-optic modulator; 106. Second acousto-optic modulator; 107. First ordinary beam splitter; 108. Second ordinary beam splitter; 109. Third polarizing beam splitter; 1010. Second polarizing beam splitter; 1011. Third quarter-wave plate; 1012. Second quarter-wave plate; 1013. Fourth ordinary beam splitter; 1014. Third ordinary beam splitter; 1015. Second photodetector; 1016. First photodetector. Detailed Implementation

[0040] To enable those skilled in the art to better understand the present invention and to more clearly define the scope of protection of the present invention, the present invention will be described in detail below with reference to certain specific embodiments. It should be noted that the following are only some specific embodiments of the present invention, and are merely a part of the embodiments of the present invention. The specific and direct descriptions of related structures are only for the convenience of understanding the present invention, and the specific features do not necessarily or directly limit the scope of the present invention. Conventional selections and substitutions made by those skilled in the art under the guidance of the present invention, as well as reasonable arrangements and combinations of several technical features under the guidance of the present invention, should all be considered within the scope of protection of the present invention.

[0041] like Figure 1 , Figure 3 and Figure 4 As shown, the present invention proposes a device for testing the dynamic performance of a pendulum based on a laser heterodyne interferometer, comprising:

[0042] The clamping fixture 7 is used to mount the pendulum 8 to be tested; the material of the clamping fixture 7 is the same as that of the quartz pendulum, which facilitates subsequent heterodyne interferometry measurements. Optionally, the pendulum 8 to be tested is a quartz pendulum, and the material of the clamping fixture 7 is quartz.

[0043] The pendulum drive module is used to place the clamping fixture 7 on which the pendulum 8 to be tested is mounted and to drive the clamping fixture 7 and the pendulum 8 to be tested to move simultaneously based on the drive signal; that is, the clamping fixture 7 and the pendulum 8 to be tested are simultaneously the detection objects of the heterodyne interferometry optical path 10.

[0044] The heterodyne interferometry optical path 10 is used to generate two measurement beams and apply the two measurement beams to the clamping fixture 7 and the pendulum plate 8 under test respectively to generate corresponding reflected beams. After collecting the reflected beams of the clamping fixture 7 and the pendulum plate 8 under test, two beat frequency signals are generated.

[0045] The signal processing module is used to generate the dynamic response characteristics of the pendulum 8 under test based on the drive signal of the pendulum drive module and the two beat frequency signals.

[0046] It should be noted that, Figure 1 In the diagram, the arrows between the piezoelectric ceramic 3, the clamping fixture 7, and the pendulum 8 under test indicate the mechanical connection between these three components; the arrows between the clamping fixture 7 and the heterodyne interferometry optical path 10, and between the pendulum 8 under test and the heterodyne interferometry optical path 10, indicate optical signal transmission; the bold arrows between other components indicate electrical signal transmission.

[0047] The oscillator drive module includes:

[0048] The displacement platform is mounted on the optical platform 6 via the adapter fixture 11. The heterodyne interferometry optical path 10 is also set on the optical platform 6. The piezoelectric ceramic 3 is installed in the displacement platform and is used to mount the clamping fixture 7. The pendulum plate 8 under test and the clamping fixture 7 are vertically set on the optical platform 6. The signal generator 1 is electrically connected to the piezoelectric ceramic 3 via the voltage amplifier 2. The signal generator 1 applies a voltage signal with a preset frequency and amplitude to the piezoelectric ceramic 3 through the voltage amplifier 2, thereby driving the clamping fixture 7 and the pendulum plate 8 under test according to the dynamic acceleration signal (i.e., the periodic vibration signal with adjustable frequency and amplitude) with a known frequency and amplitude, so that the pendulum tongue of the pendulum plate 8 under test produces a small displacement response.

[0049] The displacement platform is used to adjust the positions of the clamping fixture 7 and the pendulum 8 under test, so that the measurement beam is incident on the clamping fixture 7 and the pendulum 8 under test, and the reflected beams of the clamping fixture 7 and the pendulum 8 under test return to the heterodyne interferometry measurement optical path 10. Specifically, the reflected beam of the clamping fixture 7 passes through the second 1 / 4 wave plate 1012 and the second polarizing beam splitter 1010 of the heterodyne interferometry measurement optical path 10, and then is combined with the optical signal propagating in the first reference arm through the third ordinary beam splitter 1014 to generate a beat frequency signal. The reflected beam of the pendulum 8 under test passes through the third 1 / 4 wave plate 1011 and the third polarizing beam splitter 109, and then is combined with the optical signal propagating in the second reference arm through the fourth ordinary beam splitter 1013 to generate a beat frequency signal.

[0050] The displacement platform includes a connected manual three-axis displacement platform 4 and a motorized two-dimensional displacement platform 5. The motorized two-dimensional displacement platform 5 is used to adjust the height and horizontal position of the pendulum 8 under test, while the manual three-axis displacement platform 4 is used to adjust the exit direction of the reflected beam from the clamping fixture 7 and the pendulum 8 under test, so that the reflected beam is incident into the heterodyne interferometry measurement optical path 10. Optionally, one side of the piezoelectric ceramic 3 is glued to the manual three-axis displacement platform 4, and the other side of the piezoelectric ceramic 3 is glued to the clamping fixture 7.

[0051] The adapter 11 includes a large right-angle bracket 111 and an optical breadboard 112; the optical breadboard 112 is vertically arranged and connected to the optical platform 6 through the large right-angle bracket 111, and the optical breadboard 112 is connected to the displacement platform.

[0052] In the heterodyne interferometry optical path 10, two light signals (i.e., measurement beams) emitted from the light signal generation unit enter the measurement arm unit and the reference arm unit, respectively. The measurement arm unit divides the incoming light signal into a first light signal and a second light signal. The first light signal emitted from the measurement arm unit is incident on the pendulum 8 under test. The light signal reflected by the pendulum 8 under test then passes through the measurement arm unit and enters the first reference arm assembly of the reference arm unit. The second light signal emitted from the measurement arm unit is incident on the clamping fixture 7. The light signal reflected by the clamping fixture 7 then passes through the measurement arm unit and enters the second reference arm assembly of the reference arm unit. The reference arm unit divides the incoming light signal into a third light signal and a fourth light signal. The first reference arm assembly combines the third light signal and the light signal reflected by the pendulum 8 under test to generate a first beat frequency signal and sends it to the signal processing module. The second reference arm assembly combines the fourth light signal and the light signal reflected by the clamping fixture 7 to generate a second beat frequency signal and sends it to the signal processing module.

[0053] One feasible implementation method is, for example Figure 2As shown, the reference arm unit includes a first acousto-optic modulator 105, a first ordinary beam splitter 107, a fourth ordinary beam splitter 1013, a third ordinary beam splitter 1014, a second photodetector 1015, and a first photodetector 1016.

[0054] The measuring arm unit includes a second acousto-optic modulator 106, a second ordinary beam splitter 108, a third polarizing beam splitter 109, a second polarizing beam splitter 1010, a third quarter-wave plate 1011, and a second quarter-wave plate 1012.

[0055] The first optical signal (i.e., a measurement beam) generated by the first polarizing beam splitter 104 is incident on the first ordinary beam splitter 107 after passing through the first acousto-optic modulator 105. The first optical signal and the second optical signal generated by the first ordinary beam splitter 107 are exactly the same. The second optical signal (i.e., another measurement beam) generated by the first polarizing beam splitter 104 is incident on the second ordinary beam splitter 108 after passing through the second acousto-optic modulator 106. The first optical signal and the second optical signal generated by the second ordinary beam splitter 108 have the same power and the same polarization direction.

[0056] The first and second optical signals generated by the second ordinary beam splitter 108 are respectively incident into the third polarization beam splitter 109 and the second polarization beam splitter 1010. The first optical signal of the third polarization beam splitter 109 is incident on the tongue of the pendulum plate 8 under test after passing through the third quarter wave plate 1011. The optical signal reflected by the pendulum plate 8 under test is then incident on the fourth ordinary beam splitter 1013 after passing through the third quarter wave plate 1011 and the third polarization beam splitter 109. The second optical signal generated by the third polarization beam splitter 109 is recovered by means of baffles, optical trash cans, etc., so that the optical signal does not enter the optical path of the measuring arm and does not interfere with the transmission of other optical signals in the optical path. The first optical signal generated by the first ordinary beam splitter 107 (i.e., the third optical signal generated by the reference arm unit) and the optical signal reflected by the test pendulum 8 emitted from the third polarization beam splitter 109 are combined by the fourth ordinary beam splitter 1013 to generate the first beat frequency signal, which is collected by the second photodetector 1015. The first optical signal of the second polarization beam splitter 1010 is incident on the clamping fixture 7 after passing through the second quarter wave plate 1012. The optical signal reflected by the clamping fixture 7 is then incident on the third ordinary beam splitter 1014 after passing through the second quarter wave plate 1012 and the second polarization beam splitter 1010. The second optical signal generated by the second polarization beam splitter 1010 is recovered by means of baffles, optical trash cans, etc., so that the optical signal does not enter the optical path of the measurement arm and does not interfere with the transmission of other optical signals in the optical path. The second optical signal generated by the first ordinary beam splitter 107 (i.e., the fourth optical signal generated by the reference arm unit) and the optical signal reflected by the clamping fixture 7 emitted from the second polarizing beam splitter 1010 are combined by the third ordinary beam splitter 1014 to generate a second beat frequency signal. The second beat frequency signal is collected by the first photodetector 1016. Both the first photodetector 1016 and the second photodetector 1015 are connected to the signal acquisition system 9 of the signal processing module. The first ordinary beam splitter 107, the fourth ordinary beam splitter 1013, and the second photodetector 1015 form the first reference arm, and the first ordinary beam splitter 107, the third ordinary beam splitter 1014, and the first photodetector 1016 form the second reference arm. The first measuring arm consists of a second ordinary beam splitter 108, a third polarizing beam splitter 109, a third quarter-wave plate 1011, a pendulum plate 8 to be tested, a fourth ordinary beam splitter 1013, and a second photodetector 1015. The second measuring arm consists of a second ordinary beam splitter 108, a second polarizing beam splitter 1010, a second quarter-wave plate 1012, a clamping fixture 7, a third ordinary beam splitter 1014, and a first photodetector 1016. The first measuring arm is used to detect the displacement of the pendulum tongue of the pendulum plate 8 to be tested, and the second measuring arm is used to detect the displacement of the clamping fixture 7.

[0057] In one feasible implementation, the optical signal generation unit includes a laser 101, a first quarter-wave plate 102, a first half-wave plate 103, and a first polarizing beam splitter 104 arranged sequentially along the optical axis. The optical signal emitted from the first half-wave plate 103 enters the first polarizing beam splitter 104 and undergoes reflection and transmission, thereby emitting two optical signals, i.e., the measurement beam. There is no need to distinguish between reflected and transmitted light entering the first acousto-optic modulator 105 and the second acousto-optic modulator 106. The other beam splitters also do not distinguish between reflected and transmitted light. The splitting power ratio of the first polarizing beam splitter 104 is adjustable, and its output first and second optical signals have different polarization directions, entering the reference arm and measurement arm respectively. Optionally, the laser 101 is a narrow-linewidth laser.

[0058] In one feasible implementation, the signal processing module includes a connected signal acquisition system 9 and a terminal computer 12. The signal acquisition system 9 is connected to the second photodetector 1015, the first photodetector 1016, and the signal monitoring terminal of the voltage amplifier 2 in the heterodyne interferometry optical path 10. The signal acquisition system 9 is used to acquire and preprocess the beat frequency signal and the monitoring terminal signal of the voltage amplifier 2. The terminal computer 12 is used for further signal processing and analysis.

[0059] In one feasible implementation, the clamping fixture 7 comprises two identical quartz plates. For example... Figure 5 As shown, each quartz plate has several evenly distributed circular openings, referred to as pendulum mounting holes. The diameter of the circular opening is slightly smaller than the outer diameter of the pendulum ring of the pendulum 8 being tested and larger than the diameter of the pendulum tongue of the pendulum 8 being tested, allowing the pendulum tongue to swing freely through the circular openings and preventing collision damage during the testing process. Each opening is surrounded by a groove that matches the size of the pendulum ring of the quartz pendulum, and rubber washers are added to protect the quartz pendulum and prevent damage during clamping. Generally, during each measurement, corresponding pendulums are installed in the mounting holes of the clamping fixture 7; these pendulums are from the same batch.

[0060] The structure of a quartz pendulum is as follows Figure 6 As shown. The outer ring is a swing ring, and the middle is a swing tongue. The swing ring and the swing tongue are connected by a flexible beam. The swing ring of the swing plate is clamped by the clamping fixture 7, and the swing tongue can swing freely in the swing plate mounting hole.

[0061] The present invention proposes a method for testing the dynamic performance of a pendulum based on a laser heterodyne interferometer, comprising the following steps:

[0062] S1: The pendulum 8 to be tested is installed on the clamping fixture 7. The pendulum driving module generates a dynamic acceleration signal with known frequency and amplitude and applies it to the clamping fixture 7 and the pendulum 8 to be tested, so that the pendulum 8 to be tested and the clamping fixture 7 produce periodic small displacements under the operation of the pendulum driving module.

[0063] S2: The heterodyne interferometry optical path 10 detects the beat frequency signal corresponding to the test pendulum 8 and the clamping fixture 7. The signal processing module calculates the actual displacement of the test pendulum 8's tongue and the clamping fixture 7 based on the collected beat frequency signal. This displacement is a periodic small displacement.

[0064] In one feasible implementation, the signal processing module calculates the actual displacement of the pendulum tongue of the pendulum plate 8 and the clamping fixture 7 based on the acquired beat frequency signal, including:

[0065] In the signal processing module, after performing phase-locked processing on the beat frequency signal of the pendulum 8 under test, the actual displacement of the pendulum tongue of the pendulum 8 under test under a given acceleration input is obtained; and after performing phase-locked processing on the beat frequency signal of the clamping fixture 7, the actual displacement of the clamping fixture 7 under a given acceleration input is obtained.

[0066] S3: The signal processing module calculates the theoretical displacement of the clamping fixture 7 and the pendulum 8 under a given acceleration input based on the voltage signal output by the voltage amplifier 2 in the pendulum drive module. The displacement response is composed of two actual displacements and the theoretical displacement.

[0067] S4: Change the amplitude and frequency of the dynamic acceleration signal of the pendulum 8 under test, repeat S1-S3 multiple times, obtain several displacement responses and form a set of displacement responses, and then generate the dynamic response characteristics of the pendulum 8 under test to the applied dynamic acceleration signal within the working frequency and range.

[0068] In one specific embodiment, the piezoelectric ceramic used is a Thorlabs PA25FEW piezoelectric ceramic chip with a maximum load voltage of 200V, a maximum displacement under full load of 2.8μm, a resonant frequency as high as 350kHz, and a load capacity of 210N at maximum displacement. The chip diameter does not exceed 1cm. According to the piezoelectric ceramic chip specifications and voltage-displacement curve, the displacement amplitude is 500nm when the input voltage is 25V. Therefore, the displacement amplitude reaches 20nm when the input voltage is 1V, and precise input modulation at the 1nm level can be achieved when the input voltage is 50mV.

[0069] In one specific embodiment, the heterodyne interferometry optical path uses a 532nm frequency-standard laser as the light source, a gooch & Housego 3080-125 model acousto-optic modulator with an operating frequency of 80MHz and a wavelength of 415-900nm, and a Thorlabs PDA100A2 photodetector. The signal acquisition system uses the Moku:Pro precision test and measurement platform developed by Liquid Instruments, which integrates multiple functions including a signal generator, data acquisition unit, and lock-in amplifier. Moku:Pro can output two sinusoidal signals with frequencies of 80.00MHz and 80.01MHz, respectively, which are then amplified by power amplifiers to modulate the first and second acousto-optic modulators. This step is crucial for the heterodyne interferometry optical path, modulating the measured pendulum displacement signal from a low-frequency range with significant noise interference to a cleaner 10kHz frequency range. The choice of 10kHz as the difference frequency for the heterodyne interferometry optical path was determined after comprehensively considering the noise of the test environment, the bandwidth of the photodetector, and other noise factors. Simultaneously, the relatively low difference frequency of 10kHz reduces the sampling frequency requirements during data acquisition and improves the calculation speed of subsequent data processing. Furthermore, when measuring the displacement signal of the pendulum at low frequencies, the frequency resolution can be increased by extending the data acquisition time to demodulate the low-frequency displacement signal. Moku:Pro can also simultaneously measure the beat frequency signal of the heterodyne interferometry optical path, the voltage signal across the piezoelectric ceramic, and the difference frequency signal of the acousto-optic modulator (AOM), and then directly analyze the measurement data via computer. Optionally, the AOM difference frequency signal can be omitted from acquisition. Instead, a sinusoidal signal with the AOM difference frequency can be generated in the terminal computer based on the parameters set for the AOM, and the displacement information can then be calculated based on the beat frequency signal of the heterodyne interferometry optical path and the voltage signal across the piezoelectric ceramic.

[0070] One feasible implementation method is, for example Figure 7 As shown, in MATLAB on the terminal computer, the detected displacement signal is calculated using IQ quadrature demodulation and Hilbert transform. This signal demodulation scheme has higher demodulation accuracy and stronger noise immunity. Furthermore, the algorithm incorporates the measured actual difference frequency signal from the acousto-optic modulator for demodulation, avoiding instability in the modulation frequencies and clock inconsistencies between the two modulators, thus improving demodulation accuracy.

[0071] Specifically, the Hilbert transform and IQ demodulation of the AOM difference frequency signal are used to extract the beat frequency signal output from the optical path near the AOM difference frequency. The high-frequency carrier of the original signal is canceled, the signal is moved to the baseband, the sideband retains the vibration information, the low-pass filter retains the vibration frequency-related signal, the high-frequency residue or noise is removed, and the phase is de-wrapped to avoid ±π jumps, thus obtaining a continuous phase signal. Meanwhile, the Hilbert transform and IQ demodulation of the original piezoelectric ceramic voltage signal can accurately demodulate the vibration signal, and the narrowband envelope signal is extracted through ultra-narrow low-pass filtering.

[0072] The reason this invention simultaneously measures both the pendulum under test and the clamping fixture is to more accurately calibrate the output displacement of the piezoelectric ceramic in real time and avoid errors caused by structural design and the installation and coordination of various components. The heterodyne interferometry optical path is not difficult to build, but it offers very high testing accuracy, achieving sub-nanometer and even picometer-level precision. This allows for precise evaluation of the pendulum's testing performance and provides a reference and guarantee for structural adjustments and performance improvements of quartz pendulums.

[0073] A 10Hz voltage signal was applied to the piezoelectric ceramic 3, and the output displacement of the piezoelectric ceramic was calibrated using a heterodyne interferometry optical path, as shown in the following figure. Figure 8 As shown in the figure, the solid line represents the actual measured displacement, and the dashed line is obtained after fitting the calibration results. The fitted linear model satisfies X = 13.047U - 1.8642, where U represents the driving voltage and X represents the actual detected displacement. The statistical index R0 is used... 2 To measure the goodness of fit of the linear model; R 2 The higher the value, the better the linear model fits the data. The R-value of this invention... 2 The result of 0.9993 demonstrates a high degree of linearity between the piezoelectric ceramic driving voltage and the actual detected displacement.

[0074] R 2 The calculation formula is as follows:

[0075] R 2 =1(SSres / SStot)

[0076] Where SSres represents the residual sum of squares, used to characterize the difference between the collected data points and the predicted data points in the linear model; SStot represents the total sum of squares, used to characterize the difference between the collected data points and the mean of the collected data points; 1() represents the percentage operation.

[0077] The present invention also conducted experiments measuring the actual detected displacement corresponding to different frequencies under the same driving voltage amplitude, and the results are shown in Table 1. Table 1 shows that the displacement detection level driven by the piezoelectric ceramic is similar under different driving frequencies using the heterodyne interferometry optical path.

[0078] Table 1 Actual Detected Displacement Data

[0079]

[0080] Finally, it should be noted that the above embodiments and descriptions are only used to illustrate the technical solutions of the present invention and not to limit it. Those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the disclosure of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the protection scope of the claims of the present invention.

Claims

1. A pendulum dynamic performance testing device based on a laser heterodyne interferometer, characterized in that, The application relates to a dynamic response characteristic measurement device for a pendulum plate, which comprises the following components: a clamping tool (7) for mounting a pendulum plate to be measured (8); a pendulum plate driving module for placing the clamping tool (7) mounted with the pendulum plate to be measured (8) and driving the clamping tool (7) and the pendulum plate to be measured (8) to move simultaneously based on a driving signal; a heterodyne interference measurement light path (10) for generating two measurement light beams and producing corresponding reflected light beams after the two measurement light beams act on the clamping tool (7) and the pendulum plate to be measured (8) respectively, and generating two beat signals after the reflected light beams of the clamping tool (7) and the pendulum plate to be measured (8) are collected; a signal processing module for generating the dynamic response characteristic of the pendulum plate to be measured (8) according to the driving signal of the pendulum plate driving module and the two beat signals.

2. The pendulum dynamic performance testing device based on a laser heterodyne interferometer according to claim 1, characterized in that, The pendulum plate driving module comprises: a piezoelectric ceramic (3) mounted in a displacement platform, the piezoelectric ceramic (3) is used for mounting the clamping tool (7), and a signal generator (1) is electrically connected with the piezoelectric ceramic (3) through a voltage amplifier (2); the displacement platform is used for adjusting the positions of the clamping tool (7) and the pendulum plate to be measured (8), so that the measurement light beams are incident on the clamping tool (7) and the pendulum plate to be measured (8), and the reflected light beams of the clamping tool (7) and the pendulum plate to be measured (8) return to the heterodyne interference measurement light path (10).

3. The laser heterodyne interferometer based pendulum dynamic performance testing device according to claim 2, characterized in that, The displacement platform comprises a connected manual three-axis displacement platform (4) and an electric two-dimensional displacement platform (5), the electric two-dimensional displacement platform (5) is used for adjusting the height and horizontal position of the pendulum plate to be measured (8), and the manual three-axis displacement platform (4) is used for adjusting the emission direction of the reflected light beams of the clamping tool (7) and the pendulum plate to be measured (8), so that the reflected light beams are incident on the heterodyne interference measurement light path (10).

4. The pendulum dynamic performance testing device based on a laser heterodyne interferometer according to claim 1, characterized in that, The heterodyne interference measurement light path (10) comprises: two light signals emitted from a light signal generating unit enter a measurement arm unit and a reference arm unit respectively, the measurement arm unit divides the entering light signals into first light signals and second light signals, the first light signals emitted from the measurement arm unit are incident on the pendulum plate to be measured (8); the light signals reflected by the pendulum plate to be measured (8) are incident on a first reference arm assembly of the reference arm unit after passing through the measurement arm unit again; the second light signals emitted from the measurement arm unit are incident on the clamping tool (7); the light signals reflected by the clamping tool (7) are incident on a second reference arm assembly of the reference arm unit after passing through the measurement arm unit again; the reference arm unit divides the entering light signals into third light signals and fourth light signals, the first reference arm assembly produces a first beat signal after the third light signals and the light signals reflected by the pendulum plate to be measured (8) are combined; the second reference arm assembly produces a second beat signal after the fourth light signals and the light signals reflected by the clamping tool (7) are combined.

5. The laser heterodyne interferometer based pendulum dynamic performance testing device according to claim 4, characterized in that, The measurement arm unit comprises a second acousto-optic modulator (106), a second common beam splitter prism (108), a third polarizing beam splitter prism (109), a second polarizing beam splitter prism (1010), a third 1 / 4 wave plate (1011) and a second 1 / 4 wave plate (1012); one light signal emitted from the light signal generating unit enters the second acousto-optic modulator (106) and then enters the second common beam splitter prism (108); the first light signal and the second light signal generated by the second common beam splitter prism (108) enter the third polarizing beam splitter prism (109) and the second polarizing beam splitter prism (1010) respectively; the first light signal of the third polarizing beam splitter prism (109) enters the to-be-measured pendulum piece (8) through the third 1 / 4 wave plate (1011), and the light signal reflected by the to-be-measured pendulum piece (8) enters the first reference arm assembly through the third 1 / 4 wave plate (1011) and the third polarizing beam splitter prism (109) again; the first light signal of the second polarizing beam splitter prism (1010) enters the clamping tool (7) through the second 1 / 4 wave plate (1012), and the light signal reflected by the clamping tool (7) enters the second reference arm assembly through the second 1 / 4 wave plate (1012) and the second polarizing beam splitter prism (1010) again.

6. The laser heterodyne interferometer based pendulum dynamic performance testing device according to claim 4, characterized in that, The reference arm unit comprises a first acousto-optic modulator (105), a first common beam splitter prism (107), a fourth common beam splitter prism (1013), a third common beam splitter prism (1014), a second photodetector (1015) and a first photodetector (1016); one light signal emitted from the light signal generating unit enters the first acousto-optic modulator (105) and then enters the first common beam splitter prism (107); the first light signal generated by the first common beam splitter prism (107) and the light signal reflected by the to-be-measured pendulum piece (8) emitted from the measurement arm unit are combined by the fourth common beam splitter prism (1013) to generate a first beat frequency signal; the first beat frequency signal is collected by the second photodetector (1015); the second light signal generated by the first common beam splitter prism (107) and the light signal reflected by the clamping tool (7) emitted from the measurement arm unit are combined by the third common beam splitter prism (1014) to generate a second beat frequency signal, and the second beat frequency signal is collected by the first photodetector (1016).

7. The laser heterodyne interferometer based pendulum dynamic performance testing device according to claim 4, characterized in that, The light signal generating unit comprises a laser (101), a first 1 / 4 wave plate (102), a first half wave plate (103) and a first polarizing beam splitter prism (104) arranged in sequence along an optical axis; the light signal emitted from the first half wave plate (103) enters the first polarizing beam splitter prism (104) to be reflected and transmitted, so that two light signals are emitted.

8. The laser heterodyne interferometer based pendulum dynamic performance testing device according to claim 1, wherein, The clamping tool (7) comprises two plates, and each plate is provided with a pendulum piece mounting hole.

9. A method for testing dynamic performance of a pendulum based on a laser heterodyne interferometer, characterized in that, The test method adopts the pendulum piece dynamic performance test device based on a laser heterodyne interferometer, and comprises the following steps: S1: install the to-be-tested pendulum plate (8) on the clamping tool (7), generate a dynamic acceleration signal by using a pendulum plate driving module and act on the clamping tool (7) and the to-be-tested pendulum plate (8), so that the to-be-tested pendulum plate (8) and the clamping tool (7) produce periodic micro-displacement under the working of the pendulum plate driving module; S2: the heterodyne interference measurement light path (10) detects the beat frequency signals corresponding to the to-be-tested pendulum plate (8) and the clamping tool (7), and a signal processing module calculates the actual displacement of the to-be-tested pendulum plate (8) and the clamping tool (7) according to the collected beat frequency signals; S3: the signal processing module calculates the theoretical displacement of the clamping tool (7) according to the voltage signal output in the pendulum plate driving module, and a displacement response is composed of the two actual displacements and the theoretical displacement; S4: the amplitude and frequency of the dynamic acceleration signal of the to-be-tested pendulum plate (8) are changed, S1-S3 are repeated multiple times, a plurality of displacement responses are obtained and a displacement response set is composed, and then the dynamic response characteristics of the to-be-tested pendulum plate (8) to the applied dynamic acceleration signal in the working frequency and the range are generated.

10. The method of claim 9, wherein the laser heterodyne interferometer is a laser Doppler vibrometer. In the S2, the signal processing module calculates the actual displacement of the to-be-tested pendulum plate (8) and the clamping tool (7) according to the collected beat frequency signals, including: In the signal processing module, after the beat frequency signal of the to-be-tested pendulum plate (8) is phase-locked, the actual displacement of the to-be-tested pendulum plate (8) is obtained, and after the beat frequency signal of the clamping tool (7) is phase-locked, the actual displacement of the clamping tool (7) is obtained.

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