Ultrahigh vacuum compatible angular vibration online monitoring system and method

Abstract

The invention provides an ultrahigh vacuum compatible angular vibration online monitoring system and method, and belongs to the technical field of precision engineering and vibration measurement. The system comprises a differential measurement unit, a signal transmission unit, a signal acquisition unit and a data processing terminal, the differential measurement unit is composed of two sealed vacuum measurement assemblies and a rigid connection assembly, a passive magnetoelectric speed sensor is arranged in the differential measurement unit, and the differential measurement unit adapts to an ultrahigh vacuum environment through vacuum compatible design. The signal acquisition unit realizes synchronous sampling of two paths of signals, and the data processing terminal solves angular vibration information through differential operation, frequency domain integration and other algorithms. The device can be directly deployed in an ultrahigh vacuum cavity, shields external vibration interference, realizes in-situ and real-time angular vibration monitoring of nano-radian magnitude, has the advantages of excellent thermal stability, compact structure and low cost, is suitable for vibration monitoring of precise optical machine elements in large scientific devices and high-end manufacturing equipment, and has a wide application prospect.

Description

Technical Field

[0001] This invention belongs to the field of precision engineering and vibration measurement technology, specifically relating to an online angular vibration monitoring system and method compatible with ultra-high vacuum. It is particularly suitable for large scientific facilities and high-end manufacturing equipment such as fourth-generation synchrotron radiation sources, high-energy particle accelerators, and extreme ultraviolet lithography machines. It can perform in-situ, real-time, nano-arc-level micro-angular vibration monitoring of precision optomechanical components such as mirrors and monochromators in ultra-high vacuum environments. Background Technology

[0002] With the advancement of equipment such as fourth-generation synchrotron radiation sources, free-electron laser devices, and extreme ultraviolet lithography machines towards higher brightness and resolution, the attitude stability requirements for core optomechanical components have increased to the nano-arc level. These components typically operate in ultra-high vacuum (better than 10⁻⁻⁴). 7 Monitoring in-situ, real-time micro-angular vibrations in environments with a permeability of 100 Pa (Pa) presents significant technical challenges.

[0003] Existing technologies mainly fall into three categories, all of which have significant limitations:

[0004] Non-contact solutions based on external optical measurements: These methods utilize laser interferometers, laser Doppler vibrometers, etc., to measure through the observation window of a vacuum chamber. However, they suffer from reference frame coupling issues, as the vibration of the testing equipment itself can be coupled into the measurement data. The measurement optical path is susceptible to air disturbances, temperature gradients, and stress birefringence of the observation window, resulting in large errors. Furthermore, they rely on optical windows and straight optical paths, making it impossible to measure deep within the vacuum chamber or obstructed areas.

[0005] Offline measurement solutions based on traditional inertial sensors: Commercial vibration sensors contain rubber seals, adhesives, and non-vacuum cables. Directly placing them in ultra-high vacuum will cause material outgassing and environmental pollution. They can only be tested offline in atmospheric conditions or with the vacuum chamber open, and cannot reflect the vibration characteristics of the equipment in online vacuum operation.

[0006] Gyroscope-based angular velocity measurement scheme: MEMS gyroscopes have poor applicability and are difficult to meet the measurement requirements of ultra-high vacuum micro-vibration scenarios.

[0007] In summary, existing technologies lack an online angular vibration monitoring system that simultaneously meets the requirements of ultra-high vacuum compatibility, nano-arc-level measurement accuracy, and low-cost in-situ deployment. Summary of the Invention

[0008] To address the shortcomings of existing technologies that cannot simultaneously achieve compatibility with ultra-high vacuum, nanoradian measurement accuracy, and in-situ real-time monitoring, this invention provides an ultra-high vacuum compatible online angular vibration monitoring system and method, enabling high-confidence, low-cost online monitoring of micro-angular vibrations of precision optomechanical components in ultra-high vacuum environments.

[0009] To achieve the above objectives, the present invention provides the following technical solution:

[0010] An ultra-high vacuum compatible online angular vibration monitoring system includes a differential measurement unit, a signal transmission unit, a signal acquisition unit, and a data processing terminal;

[0011] The differential measurement unit includes a first vacuum measurement component, a second vacuum measurement component, and a rigid connection component. The first vacuum measurement component and the second vacuum measurement component are independent sealed cavities, each containing a vibration sensor, and are fixedly connected by the rigid connection component.

[0012] The signal transmission unit is used to lead the signal acquired by the differential measurement unit to the outside of the vacuum cavity;

[0013] The signal acquisition unit is a multi-channel synchronous data acquisition device, connected between the signal transmission unit and the data processing terminal, used to receive two analog signals and perform analog-to-digital conversion;

[0014] The data processing terminal is communicatively connected to the signal acquisition unit and is equipped with an angular vibration monitoring algorithm module, which is used to perform kinematic difference, frequency domain integration and data storage on the two synchronously acquired signals to calculate the angular vibration information of the measured object.

[0015] As a further technical solution of the present invention: the first vacuum measuring component and the second vacuum measuring component are made of vacuum-compatible materials, and the cavity is provided with a vacuum sealing cover plate and a metal sealing gasket; all non-airtight connection screw mounting holes and positioning blind holes are provided with process venting holes or exhaust grooves, and the venting holes are connected to the bottom of the blind holes or the thread gap to the external vacuum environment.

[0016] As a further technical solution of the present invention: the vibration sensor is a passive magnetoelectric velocity sensor, which works based on the principle of electromagnetic induction and can convert mechanical vibration into voltage signal without external power supply.

[0017] As a further technical solution of the present invention: the vacuum measurement component is provided with a rigid adapter bracket, and the vibration sensor is mechanically coupled to the bottom of the cavity by means of screw locking through the adapter bracket.

[0018] As a further technical solution of the present invention: the rigid connection component is provided with a precision-machined positioning step or pin hole interface, which is used to rigidly lock the spatial position of the two vacuum measuring components, ensuring that their sensitive axes are strictly parallel and the physical baseline distance is constant; the main body is made of a material with a low coefficient of thermal expansion.

[0019] As a further technical solution of the present invention: a heat-insulating support component is provided between the rigid connection component and the object being tested, and the heat-insulating support component is a ceramic heat-insulating pad.

[0020] As a further technical solution of the present invention: all screw connections of the rigid connection assembly are provided with exhaust channels and a vacuum-compatible cable fixing structure, wherein the cable fixing structure is a cable pressure plate or a limiting slot.

[0021] As a further technical solution of the present invention: the signal acquisition unit adopts an Ethernet-based dynamic signal acquisition chassis and is equipped with a 24-bit resolution synchronous sampling module.

[0022] A method for online monitoring of angular vibration based on the system of claim 1 includes the following steps:

[0023] S1: Before installation onto the object under test, the first vacuum-sealed unit and the second vacuum-sealed unit are precisely assembled offline using the geometric positioning structure on the rigid bridging assembly. The self-alignment of the two sensors is achieved using geometric constraints, thereby constructing an integral differential measurement unit with parallel sensitive axes and a fixed baseline distance (L).

[0024] S2: The pre-assembled differential measurement unit is installed as a whole onto the surface of the object being measured through a three-protrusion structure;

[0025] S3: Synchronously acquire vibration velocity signals output from two vacuum-sealed units. and Differential operation is performed on the two signals using the fixed baseline distance (L). The original angular velocity signal of the object under test is calculated;

[0026] S4: Apply a 1Hz~100Hz bandpass filter to the calculated raw angular velocity signal to pre-filter out DC bias, low-frequency trend terms and high-frequency background noise in the time domain to obtain the purified angular vibration velocity signal.

[0027] S5: Estimate the power spectral density (PSD) of the purified angular velocity signal, converting the time-domain signal into the frequency-domain angular velocity power spectral density function. To characterize the distribution of angular vibration energy with frequency;

[0028] S6: The power spectral density function of the angular velocity in the frequency domain Perform an integral transformation using the formula Convert it to angular displacement power spectral density function ;

[0029] S7: Based on preset attention bandwidth angular displacement power spectral density function By integrating and taking the square root within this frequency band, the root mean square value (RMS) of the angular vibration within this frequency band can be calculated.

[0030] As a further technical solution of the present invention, it also includes step S8: the data processing terminal executes a multi-dimensional monitoring and anomaly-triggered storage strategy.

[0031] S8-1 Real-time monitoring: The time-domain waveform of the differential angular velocity is synchronously updated and displayed on the interactive interface, and the real-time power spectral density (PSD) curve is refreshed with a first preset time interval (e.g., 4s).

[0032] S8-2, Trend Recording: Using a second preset time interval (e.g., 10s) as the period, extract the angular vibration RMS value within the interval as historical feature data for persistent storage and draw a long-term trend chart;

[0033] S8-3, Abnormal Event Handling Mechanism: The system maintains a ring buffer mechanism to temporarily store the raw angular velocity data of a fixed duration (e.g., 60s) before the current moment. When the monitored RMS value exceeds the preset safety threshold, the system automatically freezes the ring buffer and persists its contents to the storage medium as the raw data record for fault diagnosis.

[0034] This technology proposes an online angular vibration monitoring system compatible with ultra-high vacuum, which has the following advantages and benefits:

[0035] High measurement confidence: The sensor is directly integrated into the object being measured, and the measurement is based on the inertial coordinate system, completely shielding the vibration interference from the external environment or the test stand, and obtaining the true value of absolute angular vibration.

[0036] Ultra-high vacuum compatibility: Through a highly airtight packaging structure and vacuum feedthrough design, traditional high-precision inertial sensors are adapted to ultra-high vacuum environments, enabling in-situ, continuous, and real-time monitoring of equipment during online operation.

[0037] Excellent thermal stability: The use of passive sensors, ceramic insulation components, and materials with low thermal expansion coefficients effectively avoids the impact of thermal deformation on measurement accuracy.

[0038] It has strong engineering applicability: its compact structure and small size allow it to be flexibly deployed in the narrow space inside a vacuum chamber; it has no precision optical components, and its cost is far lower than that of a laser interferometer, making it extremely valuable for widespread application. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the overall system architecture according to an embodiment of the present invention;

[0040] Figure 2 This is an exploded view of the overall structure and installation of the differential measurement unit according to an embodiment of the present invention;

[0041] Figure 3This is an exploded view of the structure of a single vacuum measurement component according to an embodiment of the present invention;

[0042] Figure 4 This is an exploded view of the rigid connection component structure according to an embodiment of the present invention;

[0043] Figure 5 This is a schematic flowchart of the online angular vibration monitoring method according to an embodiment of the present invention;

[0044] The markings in the diagram are as follows: 110 - Differential measurement unit; 120 - Signal transmission unit; 130 - Signal acquisition unit; 140 - Data processing terminal; 210 - First vacuum measurement component; 220 - Second vacuum measurement component; 230 - Rigid connection component; 240 - Object under test; 211 - Vacuum chamber; 212 - Vibration sensor; 213 - Internal mounting bracket; 214 - Sealing cover plate; 215 - Vacuum sealing gasket; 216 - Vacuum feedthrough connector; 231 - Mounting base; 232 - Geometric positioning step; 233 - Thermal insulation gasket assembly; 234 - Cable fixing block. Detailed Implementation

[0045] The present invention will be further described below with reference to the embodiments. It should be noted that these are merely examples and descriptions of the inventive concept. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the inventive concept or exceed the scope defined in the claims, they should all be considered to fall within the protection scope of the present invention.

[0046] Example 1: This example provides a method suitable for ultra-high vacuum (UHV, vacuum level better than...) An online monitoring system for angular vibration in an environment (Pa).

[0047] The overall system architecture is as follows Figure 1 As shown, this system spans two environmental regions: vacuum and atmosphere. It mainly consists of a differential measurement unit 110 located in the ultra-high vacuum environment, a signal transmission unit 120 spanning the environment, and a data acquisition unit 130 and a data processing unit 140 located in the atmospheric environment.

[0048] The structural design of the differential measurement unit is as follows: Figure 2 , Figure 3 and Figure 4 As shown, the differential measurement unit 110 adopts a modular architecture of "split offline packaging and rigid online integration", specifically including:

[0049] The first vacuum sealing unit 210 and the second vacuum sealing unit 220 are both independently sealed rectangular metal cavities 211, preferably made of 304 stainless steel, with electrolytic polishing to withstand UHV environments. Inside the cavity, a magnetoelectric speed sensor 213 (such as a 941B type magnetoelectric speed sensor with a sensitivity of approximately 20-30V / (m / s)) is suspended and mounted via a mounting bracket 212. This sensor is a passive device and does not generate heat during operation. A sealing cover 214 is provided on the top of the cavity, and hermetic sealing is achieved through a silver wire coil 215.

[0050] Rigid connection unit 230: This component serves as the geometric reference for the entire module and has a plate-like structure. To ensure the stability of the measurement baseline under vacuum baking (up to 120°C) and operating temperature fluctuations, the main body 231 is preferably made of Invar alloy (Invar36), which has a coefficient of thermal expansion lower than 100°C. .like Figure 5 As shown, the rigid bridging assembly 230 is provided with a geometric positioning structure 232, specifically a precision positioning step. Two vacuum-sealed units are mounted at both ends of the assembly through this structure, thereby forcibly limiting the parallelism of the sensitive axes of the two vacuum measurement units and establishing a fixed physical baseline distance L (L is set to 200mm in this embodiment). To prevent the heat of the object under test from being directly conducted to the system, thereby causing geometric errors in the system, this embodiment adopts a "thermal blocking" installation strategy. An independent heat insulation pad 233 is provided between the rigid connection unit 230 and the object under test 240. The heat insulation pad 233 is preferably made of vacuum-compatible special ceramic materials, such as alumina ceramic (Al2O3), zirconia ceramic (ZrO2), or machinable glass ceramic (Macor). These materials have high compressive strength, extremely low thermal conductivity, and excellent ultra-high vacuum degassing characteristics.

[0051] Signal Transmission and Acquisition: In the vacuum environment, the sensor signal cables use twisted-pair shielded cables with PEEK insulation or polyimide (Kapton) sheathing, and are fixed by the cable clamp 234 on the top surface of the rigid connection unit to suppress the "flickering effect" of the cables in the vacuum micro-vibration environment. The signal cables are led out to the signal acquisition unit 140 through the vacuum feedthrough flange, which is a CF flange with welded BNC connectors. Outside the vacuum chamber (atmospheric side), a low-noise coaxial cable is used to connect the atmospheric side interface of the vacuum feedthrough to the data acquisition terminal 130. In this embodiment, the data acquisition terminal 130 is an NI (National Instruments) CompactDAQ system, specifically composed of an NIcDAQ-9185 acquisition chassis and an NI9234 dynamic signal acquisition card, and is connected to the data processing terminal 140 (host computer) via a Gigabit Ethernet cable.

[0052] Example 2: This example describes in detail the angular vibration monitoring method running on the data processing terminal 140. The method flow is as follows: Figure 5 As shown.

[0053] S3-S4: Acquisition and Differential Calculation. The system synchronously acquires two velocity signals at a sampling rate of 2kHz. Calculate angular velocity .

[0054] S5: Signal conditioning (bandpass filtering). For A digital bandpass filter (such as a Butterworth filter) in the 1Hz-100Hz range is applied. The lower limit of 1Hz effectively filters out DC zero drift and extremely low-frequency ground pulsation from the sensor, while the upper limit of 100Hz filters out electronic noise and high-frequency modes that are not of interest.

[0055] S6-S7: Frequency domain integration. The filtered signal is windowed (e.g., using the Hanning window) using the Welch algorithm, and PSD calculations are performed to obtain the angular velocity power spectral density. Using the formula Directly obtain the angular displacement power spectrum;

[0056] S8-S9: Data monitoring and anomaly triggering. The system runs three data streams simultaneously:

[0057] 1. The time-domain waveform and PSD curve are refreshed every 4 seconds so that the operator can observe the current vibration frequency (such as 50Hz power frequency or 300Hz molecular pump frequency).

[0058] 2. Calculate the RMS value within the 1-100Hz bandwidth every 10 seconds and store it in the database to generate weekly / monthly stability reports.

[0059] 3. The system maintains a 60-second circular buffer in memory. Once the calculated RMS value exceeds a preset threshold (e.g., 100 nrad), the system immediately triggers a "freeze" command, writing the raw angular vibration velocity data containing the fault for 60 seconds into the hard disk for subsequent fault diagnosis.

[0060] This invention utilizes the physical characteristics of inertial sensors to perform measurements based on an inertial coordinate system. By directly integrating the sensor onto the object under test, the system can completely shield against vibration interference from the external environment or the test support, directly obtaining the true value of the absolute angular vibration of the precision mechanism under test relative to inertial space, significantly improving the physical confidence of the measurement.

[0061] This invention designs an integrated differential measurement system compatible with ultra-high vacuum. A highly hermetic packaging structure physically isolates the sensor from the vacuum environment, and signal extraction is achieved through vacuum feedthrough. This design enables high-precision inertial sensors, originally only usable in atmospheric conditions, to be compatible with ultra-high vacuum environments, allowing for in-situ, continuous, and real-time angular vibration monitoring during actual equipment operation, achieving a leap from "offline testing" to "online real-time monitoring."

[0062] This invention ensures extremely high thermal stability and avoids the impact of thermal deformation on measurement accuracy by using a passive magnetoelectric sensor, setting a ceramic heat insulation component between the system and the object being measured, and using materials with the thermal expansion coefficient.

[0063] The system described in this invention has a compact structure and small size, allowing for flexible multi-point deployment within the confined spaces of a vacuum cavity. With its simple structure and lack of precision optical components, the system achieves equal or even superior monitoring performance at a cost far lower than laser interferometers, making it highly valuable for engineering applications.

[0064] The above is an exemplary description of the invention. Obviously, the specific implementation of the invention is not limited to the above-described manner. Any non-substantial improvement made using the inventive concept and technical solution of the invention, or the direct application of the inventive concept and technical solution to other situations without modification, is within the protection scope of the invention.

Claims

1. An online monitoring system for angular vibration compatible with ultra-high vacuum, characterized in that, It includes a differential measurement unit, a signal transmission unit, a signal acquisition unit, and a data processing terminal; The differential measurement unit includes a first vacuum measurement component, a second vacuum measurement component, and a rigid connection component. The first vacuum measurement component and the second vacuum measurement component are independent sealed cavities, each containing a vibration sensor, and are fixedly connected by the rigid connection component. The signal transmission unit is used to lead the signal acquired by the differential measurement unit to the outside of the vacuum cavity; The signal acquisition unit is a multi-channel synchronous data acquisition device, connected between the signal transmission unit and the data processing terminal, used to receive two analog signals and perform analog-to-digital conversion; The data processing terminal is communicatively connected to the signal acquisition unit and is equipped with an angular vibration monitoring algorithm module, which is used to perform kinematic difference, frequency domain integration and data storage on the two synchronously acquired signals to calculate the angular vibration information of the measured object.

2. The ultra-high vacuum compatible online angular vibration monitoring system according to claim 1, characterized in that, The first and second vacuum measurement components are made of vacuum-compatible materials, and the cavity is equipped with a vacuum sealing cover and a metal sealing gasket; all non-airtight connection screw mounting holes and positioning blind holes are equipped with process venting holes or venting grooves, and the venting holes connect to the bottom of the blind holes or the thread gap to the external vacuum environment.

3. The ultra-high vacuum compatible online angular vibration monitoring system according to claim 1, characterized in that, The vibration sensor is a passive magnetoelectric velocity sensor.

4. The ultra-high vacuum compatible online angular vibration monitoring system according to claim 2, characterized in that, The vacuum measurement assembly has a rigid adapter bracket inside, and the vibration sensor is mechanically coupled to the bottom of the cavity by screw locking through the adapter bracket.

5. The ultra-high vacuum compatible online angular vibration monitoring system according to claim 1, characterized in that, The rigid connection component is equipped with a precision-machined positioning step or pin hole interface for rigidly locking the spatial position of the two vacuum measuring components, ensuring that their sensitive axes are strictly parallel and the physical baseline distance is constant; the main body is made of a material with a low coefficient of thermal expansion.

6. The ultra-high vacuum compatible online angular vibration monitoring system according to claim 1, characterized in that, A thermal insulation support component is provided between the rigid connection component and the object being tested, and the thermal insulation support component is a ceramic thermal insulation pad.

7. The ultra-high vacuum compatible online angular vibration monitoring system according to claim 1, characterized in that, All screw connections of the rigid connection assembly are provided with venting channels and a vacuum-compatible cable fixing structure, which is a cable pressure plate or a limiting slot.

8. The ultra-high vacuum compatible online angular vibration monitoring system according to claim 1, characterized in that, The signal acquisition unit adopts an Ethernet-based dynamic signal acquisition chassis and is equipped with a 24-bit resolution synchronous sampling module.

9. A method for online monitoring of angular vibration compatible with ultra-high vacuum, characterized in that, The system applied to any one of claims 1-8 includes the following steps: S1: Before installation onto the object being measured, the first vacuum-sealed unit and the second vacuum-sealed unit are precisely assembled offline using the geometric positioning structure on the rigid bridging assembly. The self-alignment of the two sensors is achieved using geometric constraints, thus constructing an integral differential measurement unit with parallel sensitive axes and a fixed baseline distance. S2: The pre-assembled differential measurement unit is installed as a whole onto the surface of the object being measured through a three-protrusion structure; S3: Synchronously acquire vibration velocity signals output from two vacuum-sealed units. and Differential operation is performed on the two signals using a fixed baseline distance L. The original angular velocity signal of the object under test is calculated; S4: Apply a 1Hz~100Hz bandpass filter to the calculated raw angular velocity signal to pre-filter out DC bias, low-frequency trend terms and high-frequency background noise in the time domain to obtain the purified angular vibration velocity signal. S5: Estimate the power spectral density of the purified angular velocity signal, converting the time-domain signal into the angular velocity power spectral density function in the frequency domain. To characterize the distribution of angular vibration energy with frequency; S6: The power spectral density function of the angular velocity in the frequency domain Perform an integral transformation using the formula Convert it to angular displacement power spectral density function ; S7: Based on preset attention bandwidth angular displacement power spectral density function By integrating and taking the square root within this frequency band, the root mean square value of the angular vibration in this frequency band can be calculated.

10. The ultra-high vacuum compatible online monitoring method for angular vibration according to claim 9, characterized in that, It also includes step S8: The data processing terminal executes a multi-dimensional monitoring and anomaly-triggered storage strategy. S8-1 Real-time monitoring: The time-domain waveform of the differential angular velocity is synchronously updated and displayed on the interactive interface, and the real-time power spectral density curve is refreshed with a first preset time interval. S8-2, Trend Recording: Using the second preset time interval as the period, extract the angular vibration RMS value within the interval as historical feature data for persistent storage and draw a long-term trend chart; S8-3, Abnormal Event Handling Mechanism: The system maintains a circular cache mechanism to temporarily store the raw angular velocity data of a fixed duration before the current moment in real time; when the monitored RMS value exceeds the preset safety threshold, the system automatically freezes the circular cache and persists its contents to the storage medium as the raw data record for fault diagnosis.

Images