Ion thruster working state grid micro-deformation measurement method

Abstract

The application relates to the technical field of measurement, in particular to a kind of ion thruster working state grid tiny deformation measurement method, comprising the following steps: step 1: constructing measurement system;Step 2: debugging camera;Step 3: open ion thruster to start working, make three cameras synchronous shooting by control software, complete image shooting collection every 30 seconds, and process image data collected synchronously;Step 4: continuously collect images, and process image data synchronously until ion thruster is powered off and cooled to room temperature;Step 5: according to the data processing result of continuous image collection, the result of ion thruster working state grid tiny deformation measurement is calculated.The application realizes the multidimensional repeated measurement of a group of data at the same time, improves the test accuracy, ensures the long-time continuous work of camera in vacuum, plasma environment, can collect ion thruster full working process data, and improves the reliability of test.

Description

Technical Field

[0001] This application relates to the field of measurement technology, and more specifically, to a method for measuring minute deformation of the gate of an ion thruster during operation. Background Technology

[0002] The gate assembly of an ion thruster, also known as the "ion optical system," is the core component of the ion thruster. When the thruster is working, the gate assembly undergoes thermal deformation due to high temperature, resulting in minute deformation of the gate and affecting the extraction performance. Therefore, measuring the minute deformation of the gate under working conditions is of great significance.

[0003] When the ion thruster is working, the gate temperature rises from low to high. When the thruster reaches a stable operating temperature, the small deformation of the gate also tends to stabilize. When the thruster stops working, the gate temperature gradually decreases, and the gate begins to undergo small deformation again until the thruster returns to room temperature. Therefore, it is necessary to measure the small deformation of the gate throughout the entire working process of the thruster.

[0004] Due to factors such as the plasma environment generated by the operation of ion thrusters, the complexity of the grid structure, and the heat dissipation of the camera in a vacuum, images are currently acquired using monocular cameras and image contour extraction-based calculation methods. While this method is feasible under natural light conditions, it leads to a decrease in image clarity and contrast and blurred image edges in a vacuum due to poor external lighting conditions. This results in significant errors during edge fitting. Furthermore, since cameras do not have heat dissipation issues under atmospheric conditions, they stop working due to excessively high temperatures in a vacuum, resulting in incomplete data acquisition. Summary of the Invention

[0005] This application provides a method for measuring minute deformation of the gate in the working state of an ion thruster. Based on the three-dimensional digital image correlation method, it realizes the measurement of minute deformation of the gate throughout the entire working process of the ion thruster, thereby improving the test accuracy and reliability.

[0006] To achieve the above objectives, this application provides a method for measuring minute deformation of the gate of an ion thruster in its operating state, based on a three-dimensional digital image speckle method, comprising the following steps: Step 1: Constructing a measurement system, installing a ceramic probe at the measurement position of the ion thruster gate, suspending the ion thruster inside a vacuum chamber, and installing a first camera, a second camera, and a third camera outside the beam region of the ion thruster; Step 2: Debugging the cameras, fine-tuning the camera installation position before closing the vacuum chamber, continuously taking 10 sets of static images each time, processing the image data, and calculating the displacement value. When the displacement value of all 10 sets of image data is less than 10 micrometers, debugging is complete; Step 3: Turning on the ion thruster to start operation, using control software to make the three cameras shoot synchronously, completing image acquisition every 30 seconds, and simultaneously processing the acquired image data; Step 4: Continuously acquiring images and simultaneously processing the image data until the ion thruster is turned off and cooled to room temperature; Step 5: Calculating the measurement result of minute deformation of the gate in the operating state of the ion thruster based on the data processing results of the continuously acquired images.

[0007] Furthermore, in step 1, the ceramic probe includes a cylindrical section and a spherical region, on which a speckle pattern is sprayed.

[0008] Furthermore, the ceramic probe is mounted at the test location on the gate surface, and the spherical region is not obstructed.

[0009] Furthermore, in step 1, when installing the cameras, the included angle between the first camera, the second camera, and the third camera is 120°, the distance from the ceramic probe is equal, and the optical axes of the three camera lenses all pass through the center of the spherical region of the ceramic probe.

[0010] Furthermore, in step 1, the first camera, the second camera, and the third camera are all housed inside a protective cover. The protective cover is made of a sputter-resistant metal material, and a cooling circulating water system is also installed on the protective cover housing. The inlet temperature of the cooling circulating water system is ≤15℃.

[0011] Furthermore, in step 2, when the camera is debugged and the captured image is processed, the pixel at the center of the spherical region of the ceramic probe is selected as the seed point of the image. The sub-image region is no larger than the pixel region covered by the spherical region. The search method is to traverse all pixels in the area covered by the spherical region of the ceramic probe.

[0012] Furthermore, in step 3, each time an image is captured, images from two cameras are selected as a set of data, resulting in a total of three sets of data.

[0013] Furthermore, in step 3, when processing the captured image data synchronously, each group of data is processed sequentially using filtering, integer pixel matching, and subpixel calculation. After the data processing is completed, the processing results of the three groups of data are compared. If the difference between the processing results of the three groups of data is less than 10um, then it is considered valid data.

[0014] Furthermore, in step 4, following the image acquisition and processing method in step 3, multiple sets of valid data are continuously acquired until the ion thruster is shut down and cooled to room temperature.

[0015] Furthermore, in step 5, the average value of multiple sets of valid data is calculated to obtain the result of the measurement of the small deformation of the gate in the working state of the ion thruster.

[0016] The present invention provides a method for measuring minute deformation of the grid in the working state of an ion thruster, which has the following beneficial effects:

[0017] This application involves spraying a specific speckle pattern onto the top of a ceramic probe and combining it with a three-dimensional digital image correlation method to select the optimal seed point, pixel search method, and image sub-region size. A three-camera layout is adopted, with two cameras forming three sets of binocular vision systems. This enables simultaneous multi-dimensional repeated measurement of a set of data, improving test accuracy. In addition, plasma protection and cooling measures are taken for the cameras to ensure long-term continuous operation in vacuum and plasma environments. This allows for the acquisition of data throughout the entire working process of the ion thruster, improving test reliability. Attached Figure Description

[0018] The accompanying drawings, which form part of this application, are used to provide a further understanding of the application and to make other features, objects, and advantages of the application more apparent. The illustrative embodiments and descriptions of this application are used to explain the application and do not constitute an undue limitation of the application. In the drawings:

[0019] Figure 1 This is a schematic diagram of the structure of the gate micro-deformation measurement system for the ion thruster operating state provided in the embodiments of this application;

[0020] Figure 2 This is a schematic diagram of the internal arrangement of the vacuum chamber of the ion thruster working state gate micro-deformation measurement system provided in the embodiments of this application;

[0021] Figure 3 This is a schematic diagram of a ceramic probe provided according to an embodiment of this application;

[0022] Figure 4 This is a schematic diagram of the installation between the ceramic probe and the ion thruster gate according to an embodiment of this application;

[0023] In the figure: 1-First camera, 2-Second camera, 3-Third camera, 4-Ion thruster, 41-Screen grid, 42-Accelerating grid, 43-Decelerating grid, 5-Ceramic probe, 51-Cylindrical section, 52-Spherical region, 53-Screen grid probe, 54-Accelerating grid probe, 55-Decelerating grid probe, 6-Control software, 7-Ion thruster beam region, 8-Vacuum chamber. Detailed Implementation

[0024] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0025] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this application described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0026] In this application, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "middle," "vertical," "horizontal," "lateral," and "longitudinal" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing this application and its embodiments, and are not intended to limit the indicated device, element, or component to having a specific orientation, or to be constructed and operated in a specific orientation.

[0027] Furthermore, in addition to indicating location or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in some cases to indicate a certain dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0028] In addition, the term "multiple" should mean two or more.

[0029] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0030] When the ion thruster 4 is in operation, the gate assembly will undergo slight thermal deformation due to high temperature. The method for measuring the slight deformation of the gate in the working state of the ion thruster provided in this application uses a ceramic probe 5 with speckle image pre-installed on the gate to convert the slight deformation of the gate into a slight displacement of the ceramic probe 5. Three high-definition cameras working simultaneously continuously acquire images of the changes in the ceramic probe 5. The three sets of image data are divided into three groups of two. The three slight displacements are calculated by a specific three-dimensional digital image correlation method. The relative error between the three calculated quantities is compared with the camera calibration error to determine the validity of the data. Finally, the average value of the valid data is taken as the final measurement result.

[0031] This application embodiment is based on the three-dimensional digital image correlation method, which realizes simultaneous multi-dimensional repeated measurement of a set of image data, specifically including the following steps:

[0032] Step 1: As Figure 1-2 As shown, a measurement system is constructed, wherein the ceramic probe 5 includes a cylindrical section 51 and a spherical region 52. A specific speckle pattern is sprayed onto the spherical region 52 to make the captured images clearer and obtain more accurate data processing results, such as... Figure 3 As shown; the ceramic probe 5 is mounted at the test position on the gate surface, and the spherical region 52 is not obstructed, as shown. Figure 4 As shown, the number of ceramic probes 5 is the same as the number of gates. The gates include a screen gate 41, an acceleration gate 42, and a deceleration gate 43. Similarly, the ceramic probes 5 are also equipped with screen gate probes 53, acceleration gate probes 54, and deceleration gate probes 55, which are installed at the measurement positions on the surface of each gate. Then, the ion thruster 4 is hoisted into the vacuum chamber 8. The first camera 1, the second camera 2, and the third camera 3 are installed outside the ion thruster beam region 7. The first camera 1, the second camera 2, and the third camera 3 are all housed inside a protective cover made of sputter-resistant metal material. The protective cover shell is also equipped with a cooling circulation system. The circulating water system, with an inlet temperature of ≤15℃, ensures that the camera can work continuously for a long time in vacuum and plasma environments, preventing the camera from stopping due to excessive temperature and improving the clarity of the captured images. In addition, when installing the cameras, the included angle between the first camera 1, the second camera 2, and the third camera 3 is 120°, and the distances from the ceramic probe 5 are equal. Furthermore, the optical axes of the three camera lenses all pass through the center of the spherical region 52 of the ceramic probe 5, and the included angles between the optical axes of the three lenses and the measured point are the same, ensuring that the three cameras are triggered synchronously when taking pictures, and three sets of image data can be obtained simultaneously.

[0033] Step 2: Camera debugging. Before the vacuum equipment is closed, the camera installation position is fine-tuned. Ten sets of still photos are taken continuously each time. The image data is processed and the displacement value is calculated. When the displacement value of all 10 sets of image data is less than 10 micrometers, the debugging is completed. When debugging the camera, the three-dimensional digital image correlation method is used to process the captured images. The specific acquisition process of image data is as follows: the pixel point at the center of the spherical region 52 of the ceramic probe 5 is selected as the seed point of the image. The sub-image region is not larger than the pixel region covered by the spherical region 52. The search method is to traverse all pixels in the area covered by the spherical region 52 of the ceramic probe 5.

[0034] Step 3: Turn on the ion thruster 4 to start working. Use the control software 6 to make the three cameras shoot synchronously, capturing images every 30 seconds. Process the captured image data synchronously. Each time images are captured, the images from two cameras are selected as a set of data. Combine them in pairs to obtain three sets of data, which constitute three sets of binocular vision systems. This allows for three measurement data points at the same time and measurement point, enabling multi-dimensional repeated measurement of a set of data simultaneously, ensuring the accuracy of the measurement data. In addition, when processing the captured image data, the original image is first filtered. Then, the seed point and the size of the target image sub-region are selected, and the correlation function C is determined. By traversing the area covered by the spherical region 52 of the ceramic probe 5, the pixel coordinates of the point with the largest correlation coefficient in the target image are found to determine the integer pixel displacement x (integer pixel matching). Then, the sub-pixel displacement y is determined by grayscale interpolation (sub-pixel calculation). The final displacement of the measurement point is z = x + y. After the data processing is completed, the displacement values ​​of the three sets of data are compared. If the difference between the processing results of the three sets of data is less than 10um, it is considered valid data.

[0035] Step 4: Continuously acquire images and simultaneously process image data. Following the image acquisition and processing method in Step 3, continuously acquire multiple sets of valid data until the ion thruster 4 is turned off and cooled to room temperature.

[0036] Step 5: Based on the data processing results of continuously acquired images, calculate the average value of multiple sets of valid data. Take the average value of three sets of valid data in a certain state, which is the gate spacing in the current state. Then, based on the average value of the valid data, obtain the gate spacing of two adjacent states. Subtract them one by one to obtain the final result of the gate micro-deformation measurement of the ion thruster 4 in the working state.

[0037] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for measuring minute deformation of the grid in the working state of an ion thruster, characterized in that, The three-dimensional digital image speckle method includes the following steps: Step 1: Construct a measurement system, install the ceramic probe at the measurement position of the ion thruster grid, suspend the ion thruster in the vacuum chamber, and install the first camera, second camera and third camera outside the ion thruster beam region respectively; Step 2: Adjust the camera. Before closing the vacuum chamber, fine-tune the camera installation position. Take 10 sets of still photos continuously each time, process the image data, and calculate the displacement value. When the displacement value of all 10 sets of image data is less than 10 micrometers, the adjustment is complete. Step 3: Turn on the ion thruster to start working. Use the control software to make the three cameras shoot synchronously. The image is captured every 30 seconds, and the captured image data is processed synchronously. Step 4: Continuously acquire images and process the image data simultaneously until the ion thruster is turned off and cooled to room temperature; Step 5: Based on the data processing results of continuously acquired images, calculate the results of the gate micro-deformation measurement in the working state of the ion thruster.

2. The method for measuring minute deformation of the gate in the working state of an ion thruster according to claim 1, characterized in that, In step 1, the ceramic probe includes a cylindrical section and a spherical region, on which a speckle pattern is sprayed.

3. The method for measuring minute deformation of the grid in the working state of an ion thruster according to claim 2, characterized in that, The ceramic probe is mounted at the test location on the gate surface, and the spherical region is not obstructed.

4. The method for measuring minute deformation of the gate in the working state of an ion thruster according to claim 3, characterized in that, In step 1, when installing the cameras, the included angle between the first camera, the second camera, and the third camera is 120°, the distance from the ceramic probe is equal, and the optical axes of the three camera lenses all pass through the center of the spherical region of the ceramic probe.

5. The method for measuring minute deformation of the gate in the working state of an ion thruster according to claim 4, characterized in that, In step 1, the first camera, the second camera, and the third camera are all housed inside a protective cover. The protective cover is made of a sputter-resistant metal material, and a cooling water circulation system is also provided on the protective cover housing. The inlet temperature of the cooling water circulation system is ≤15℃.

6. The method for measuring minute deformation of the gate in the working state of an ion thruster according to claim 5, characterized in that, In step 2, when the camera is debugged and the captured image is processed, the pixel at the center of the spherical region of the ceramic probe is selected as the seed point of the image. The sub-image region is no larger than the pixel region covered by the spherical region. The search method is to traverse all pixels in the area covered by the spherical region of the ceramic probe.

7. The method for measuring minute deformation of the grid in the working state of an ion thruster according to claim 1, characterized in that, In step 3, each time an image is captured, images from two cameras are selected as a set of data, resulting in a total of three sets of data.

8. The method for measuring minute deformation of the grid in the working state of an ion thruster according to claim 7, characterized in that, In step 3, when processing the captured image data synchronously, each group of data is processed sequentially using filtering, integer pixel matching, and subpixel calculation. After the data processing is completed, the processing results of the three groups of data are compared. If the difference between the processing results of the three groups of data is less than 10um, then it is considered valid data.

9. The method for measuring minute deformation of the gate in the working state of an ion thruster according to claim 8, characterized in that, In step 4, following the image acquisition and processing method in step 3, multiple sets of valid data are continuously acquired until the ion thruster is shut down and cooled to room temperature.

10. The method for measuring minute deformation of the gate in the working state of an ion thruster according to claim 9, characterized in that, In step 5, the average value of multiple sets of valid data is calculated to obtain the result of the measurement of the small deformation of the gate in the working state of the ion thruster.

Images