Shaft body rotating speed measuring system and method based on vision and coding

Abstract

The invention discloses a shaft body rotating speed measuring system and method based on vision and coding, and the system comprises a coding strip, a coding pattern on the coding strip employs multi-bit binary two-dimensional coding, the coding strip is divided into a plurality of rows in the length direction, and each row has a unique coding value; the length of the coding strip is equal to the perimeter of the shaft body; the high-speed camera is used for carrying out continuous image acquisition on the coding strip on the circumferential surface of the shaft body to be detected; and the coding vision calculation module is in communication connection with the high-speed camera and is used for acquiring the coding image acquired by the high-speed camera, preprocessing the coding image, extracting and analyzing the coding value of each frame of coding image and further calculating the rotating speed of the shaft body. A binary two-dimensional coding mode is adopted for the coding strip, the coding value of each frame of coding image is collected through the high-speed camera, then the absolute rotation angle value is obtained, the rotation speed of the shaft body is calculated, dependence on an algorithm is not large, and the measurement performance is stable.

Description

Technical Field

[0001] The present invention relates to the technical field of shaft rotation speed measurement, and in particular to a shaft rotation speed measurement system and method based on vision and coding. Background Art

[0002] Shaft speed measurement is a common measurement task in rotating machinery and is widely used in engines, turbines, transmission systems, etc. According to different measurement principles and technologies, speed measurement methods can be roughly divided into two categories: sensor methods and machine vision methods.

[0003] Traditional speed measurement methods mainly use sensor methods, including photoelectric sensors, Hall effect sensors, eddy current sensors, laser sensors, electrostatic sensors, etc. Most methods require certain modifications to the shaft (such as adding magnets or reflective markers), and the corresponding sensor mounting brackets must be designed according to different measurement environments. With the development of machine vision technology, domestic and foreign scholars have developed many new angle measurement methods based on machine vision technology. Machine vision methods have higher flexibility and non-contact advantages, and are particularly suitable for complex and dynamic speed measurements. Although visual methods can provide better system integration and adaptability, they have high requirements for image quality, computing processing capabilities, and real-time performance.

[0004] The patent application with publication number CN113447670A discloses a rotation speed measurement method and system for monocular linear array visual tracking of stripe coding marks. The scheme uses straight stripes with linear density changes to be attached end to end along the rotation direction to the surface of the shaft body. The angle change is indirectly calculated by analyzing the change in the relative frequency of the stripe sequence in the collected image through Fourier transform. There will be a frequency mutation at the junction of the stripe sequence, so it is also necessary to separately calculate the relationship between the frequency and angle changes excluding the mutation part.

[0005] Patent application with publication number CN106443046A and patent application with publication number CN106680529A respectively disclose a device and method for measuring the rotation speed of a rotating shaft based on variable density sinusoidal stripes and double sinusoidal variable density stripes. These two schemes paste linear variable density sinusoidal stripes on the surface of the rotating shaft to be measured, and different stripe densities correspond to different angles within the rotation angle of 0-2π of the rotating shaft. The stripe density of different frame images is obtained by Fourier transformation, thereby indirectly calculating the rotation angle and rotation speed values.

[0006] The patent application with publication number CN118091177A discloses a high-precision rotational speed measurement device based on vision and its measurement method. A right-angled triangle is pasted on the surface of the shaft as a measurement mark. The length of the long right-angled side of the triangle is equal to the circumference of the shaft. When the shaft rotates to different angles, the length of the virtual center line in the image and the intersection line of the triangle are different, so that the shaft angle and rotation speed value are indirectly calculated. This scheme requires the selection of a virtual center line, and different selections will lead to different angle information; at the same time, two cameras are required. Secondly, before installing the two cameras, the radial angle of their installation position needs to be measured, and the angle is calculated using the length difference of the two virtual intersection lines collected by the two cameras at different times. The installation accuracy of the two cameras is required to be high. If the shaft speed is high, the time interval between the shooting of the two cameras must be broken, otherwise the rotation may exceed one circle, so higher requirements are put forward for the coordinated control of the cameras.

[0007] In summary, among the existing vision-based rotation speed measurement solutions, the first three solutions require complex operations such as Fourier transform, have high computational overhead, and poor real-time performance. The angle measurement value of the last solution comes from the inverse calculation of the length of the virtual intersection line, which has high computational cost, poor real-time performance, and requires two cameras. It is difficult to apply to scenarios where space is limited and it is difficult to install two cameras. It also has high requirements for collaborative control of cameras and high overall implementation cost. Summary of the invention

[0008] In view of the deficiencies in the prior art, the present invention provides a system and method for measuring shaft speed based on vision and coding to solve the problem of poor real-time performance caused by high computational overhead.

[0009] In a first aspect, a system for measuring shaft speed based on vision and encoding is provided, comprising: The coding strip, on which the coding pattern adopts multi-bit binary two-dimensional coding, is multi-bit binary coding in the width direction, and the coding strip is divided into several rows in the length direction, and each row has a unique coding value; the length of the coding strip is equal to the circumference of the shaft body, and it is used to wrap around and stick to the circumferential surface of the shaft body to be tested for one circle; A high-speed camera is used to continuously capture images of the coded strips on the circumferential surface of the shaft to be measured; The coding vision calculation module is connected to the high-speed camera through the data transmission module, and is used to obtain the coded image captured by the high-speed camera and perform preprocessing, extract and analyze the coding value of each frame of the coded image, and then calculate the shaft rotation speed.

[0010] Furthermore, the coding pattern on the coding strip adopts 4-8-bit binary two-dimensional coding.

[0011] Furthermore, the binary two-dimensional encoding method adopts binary Gray code.

[0012] Furthermore, it also includes a camera bracket for fixing and adjusting the position of the high-speed camera.

[0013] In a second aspect, a method for measuring shaft speed based on vision and coding is provided, which is implemented using the shaft speed measurement system based on vision and coding as described above, and includes the following steps: Paste the coding tape and wrap it around the circumference of the shaft to be tested; A high-speed camera is used to continuously collect coding images covering the entire coding axis segment and transmit them to the coding vision computing module; The coding vision calculation module preprocesses each frame of the acquired coded image, extracts the coding value of the coded image, and parses the row number information of the corresponding coded image according to the coding value to obtain the corresponding absolute angle value, and then calculates the angle difference between two adjacent frames of coded images and calculates the instantaneous rotation speed of the shaft.

[0014] Further, the extracting the code value of the coded image and parsing the row number information of the corresponding coded image according to the code value specifically includes: Extracting the code value located on the horizontal center line of the preprocessed code image; Based on the coding value, the row number information corresponding to the current coded image is determined with reference to the coding matrix corresponding to the coding pattern on the coding strip.

[0015] Furthermore, if the coding value of the current coded image does not find a matching row in the coding matrix, the Hamming distance is used to find the nearest row from the screenwriter matrix, and the row number information of the row is used as the row number information of the current coded image.

[0016] Furthermore, the rotation angle difference between two adjacent frames of coded images is obtained by the following method: Determine the i The absolute rotation angle of the axis corresponding to the frame encoding image : ; In the formula, For the i The number of rows obtained after decoding the frame-coded image, The number of rows obtained after decoding the first frame of the encoded image. For the i The number of full revolutions of the frame coded image relative to the axis of the first frame coded image; The difference in rotation angle between two adjacent frames of coded images is .

[0017] Furthermore, the instantaneous rotation speed of the shaft is obtained by the following method: Calculate the instantaneous angular velocity of the axis corresponding to two adjacent frames of encoded images : ; In the formula, is the shooting interval of the high-speed camera, is the shooting frame rate of the high-speed camera; ; Furthermore, an interpolation algorithm is used to calculate the instantaneous rotation speed of the shaft at the non-sampling moment, thereby obtaining the continuous instantaneous rotation speed of the shaft.

[0018] The present invention proposes a system and method for measuring shaft speed based on vision and coding, which has the following beneficial effects: (1) The coding strip of the present invention adopts a multi-bit binary two-dimensional coding method, which is a two-dimensional coding with both width and length directions. Each row of the corresponding coding matrix has a unique multi-bit binary coding value, so that the collected coding image has an absolute coding, so that the corresponding row number can be obtained by identifying the coding value of the collected coding image, and the corresponding absolute rotation angle value can be calculated, and then the instantaneous rotation speed of the shaft body can be calculated. Compared with the existing method of calculating the rotation speed by calculating the stripe density change or the length of the virtual intersection line, it is less dependent on the algorithm, has a more stable measurement performance, and can be better applied to variable speed measurement scenarios; (2) Non-contact shaft rotation measurement based on machine vision uses a thin and light coding strip with negligible mass, which does not generate any load on the shaft itself. A simple measurement system consisting of a high-speed camera and a coding vision computing module can achieve non-contact measurement of the shaft. This can be used in scenarios where the shaft is not equipped with a rotation speed measurement sensor device or is difficult to install. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 Schematic diagram of the structure of a shaft speed measurement system based on vision and encoding provided by an embodiment of the present invention; Figure 2 It is a coding pattern based on 8-bit binary two-dimensional coding provided by an embodiment of the present invention; Figure 3 Schematic diagram of a coding matrix of an 8-bit binary two-dimensional code provided in an embodiment of the present invention; Figure 4 is a flowchart of image processing and decoding calculation provided by an embodiment of the present invention; Figure 5 is a partial captured image of a case provided by an embodiment of the present invention; Figure 6 These are some measurement results of the cases provided by the embodiments of the present invention. DETAILED DESCRIPTION

[0021] To make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described in detail below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0022] In the description of the present invention, it should be understood that the terms "upper", "lower", "center", "longitudinal", "lateral", "vertical", "horizontal", etc. indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. When an element is considered to be "connected" to another element, it may be directly connected to the other element or there may be a centered element at the same time. In addition, in the description of the present invention, unless otherwise specified, the meaning of "plurality" refers to at least two.

[0023] Example 1 This embodiment provides a shaft speed measurement system based on vision and encoding, such as Figure 1 As shown, including: The coding strip, on which the coding pattern adopts multi-bit binary two-dimensional coding, is multi-bit binary coding in the width direction, and the coding strip is divided into several rows in the length direction, and each row has a unique coding value; the length of the coding strip is equal to the circumference of the shaft body, and it is used to wrap around and stick to the circumferential surface of the shaft body to be tested for one circle; A high-speed camera is used to continuously capture images of the coded strips on the circumferential surface of the shaft to be measured; The coding vision calculation module is connected to the high-speed camera through the data transmission module, and is used to obtain the coded image captured by the high-speed camera and perform preprocessing, extract and analyze the coding value of each frame of the coded image, and then calculate the shaft rotation speed.

[0024] Specifically, this system uses a coding strip as the rotation angle sensor, which is pasted along the circumference of the rotating shaft to form a complete coding circle. Its main functions include: Angle calibration: The coding pattern on the coding strip is used as an identification mark, and each multi-bit binary code value represents a fixed angle change. The high-speed camera calculates the angle change during the rotation of the shaft by photographing these codes. According to different application scenarios, the coding pattern on the coding strip can choose binary two-dimensional codes with different bits. When the measurement accuracy requirements are low, 3-bit or 4-bit binary two-dimensional codes can be selected; taking 4-bit binary two-dimensional codes as an example, the corresponding coding matrix is ​​16 rows, and the corresponding angular resolution is 360 / 16=22.5 degrees / row; as the measurement accuracy requirements increase, the number of bits of binary two-dimensional codes can be gradually increased, such as 5-bit, 6-bit, 7-bit, 8-bit and higher-bit codes; Figure 2 An 8-bit binary two-dimensional coding scheme is shown, and the corresponding coding matrix is ​​256 rows, and the corresponding angular resolution is 360 / 256 degrees / row, which has a relatively high accuracy; binary two-dimensional coding with higher bits is suitable for situations where the shaft diameter is larger, otherwise the barcode of the last digit is too dense, especially in the case of high-speed rotation, the last digit will be difficult to distinguish. It should be noted that since each row of the coding matrix corresponding to the coding pattern is different, the order of the matrix coding rows can be adjusted arbitrarily, so the coding pattern can also have many corresponding deformations; however, in order to improve the recognition accuracy, it is preferred to use the binary Gray code encoding method, Figure 2 Shown is an 8-bit binary Gray code.

[0025] High-precision sensing: The encoding strip provides extremely high rotation angle accuracy, and its unique multi-bit binary code value can achieve precise angle measurement.

[0026] Shaft fitting: The coding strip needs to be precisely pasted along the circumferential surface of the shaft to ensure that the end of the coding strip is connected to correspond to the 0-360 degree rotation cycle of the shaft.

[0027] The high-speed camera of this system is responsible for real-time and continuous capture of the image data of the coded shaft segment with the coded strip pasted on the shaft body. Its main functions include: High-speed imaging: The frame rate of a high-speed camera usually needs to be higher than the rotation speed of the shaft to ensure that the angle change of each rotation of the shaft can be captured. The frame rate of the camera should be at least twice the rotation speed (rotation speed / 60×2) to ensure that there is no missing motion information between images.

[0028] Image acquisition: The camera continuously captures the coded stripes on the shaft. By continuously capturing each frame of the image, it can record the changes in the rotation angle of the shaft within a certain period of time.

[0029] The data transmission module of this system is used to connect the high-speed camera and the coding visual computing module, and is responsible for transmitting the image data collected by the high-speed camera to the coding visual computing module in real time. In this embodiment, the data transmission module includes a data cable and a signal cable, and its main functions include: High-speed data transmission: In order to meet the needs of real-time data acquisition, the data cable needs to have high-speed data transmission capabilities to ensure that the image data can be transmitted to the encoding visual computing module for processing in a timely manner.

[0030] Control signal transmission: The control signal sent by the coded visual computing module is transmitted to the high-speed camera through the signal cable to control the start and stop of the high-speed camera's shooting action, realize the acquisition of the shaft segment coded image, and provide a basis for image processing and speed calculation.

[0031] The Encoded Vision Computing Module is the data processing center of the entire measurement system, responsible for storing, processing and analyzing image data collected by the high-speed camera. Its functions include: Data storage: The encoded visual computing module needs to have a large storage capacity to accommodate the large amount of image data collected by the high-speed camera in a short period of time and provide fast reading and writing capabilities.

[0032] Image decoding and analysis: Through image processing algorithms (such as edge detection, image decoding, image matching, etc.), the coding visual computing module can identify the coding value in each image and calculate the rotation angle change between adjacent images. Furthermore, the angular velocity and rotation speed of the axis can be calculated based on the rotation angle and time interval.

[0033] Real-time calculation and display: The encoded visual computing module needs to provide real-time data processing capabilities in order to monitor the rotation state of the axis in real time and ensure the timeliness and accuracy of the data.

[0034] In some embodiments, a camera bracket is also included to fix and adjust the position of the high-speed camera to ensure that the coded image is captured accurately. Its functions include: Stability support: The camera stand needs to ensure that the camera is not affected by external interference or vibration during shooting, ensuring image clarity and stability.

[0035] Height and position adjustment: In order to more accurately align the coding stripes on the rotating axis, the camera bracket can adjust the height and angle of the camera to ensure that the complete coding stripes can be captured every time.

[0036] The entire measurement system relies on the coordinated work of various components to ensure that high-precision image data of the shaft body during rotation is collected by the high-speed camera, and the coded visual computing module uses this data to calculate the rotation angle and speed of the shaft body. The coded strip, as a high-precision angle sensing method, combined with the high-speed transmission capability of the data transmission module, ensures that the measurement system can accurately measure the rotation angle and instantaneous speed of the shaft body under constant or variable speed conditions.

[0037] The above embodiment provides a shaft rotation speed measurement system based on vision and coding, and its coding strip adopts a multi-bit binary two-dimensional coding method, which is a two-dimensional code with both width and length directions. Each row of the corresponding coding matrix has a unique multi-bit binary code, so that the collected coding image has an absolute code, so that the coding value of the collected coding image can be identified to obtain its corresponding row number, and the corresponding absolute angle value can be calculated to calculate the instantaneous rotation speed of the shaft. Compared with the existing method of calculating the change in stripe density or the length of the virtual intersection line to obtain the rotation speed, it is less dependent on the algorithm, has a more stable measurement performance, and can be better applied to variable speed measurement scenarios. Non-contact shaft rotation measurement based on machine vision uses a light and thin coding strip with negligible mass, does not generate any load on the shaft itself, and can realize non-contact measurement of the shaft by combining a simple measurement system composed of a high-speed camera and a coding vision computing module. It can be applied to scenarios where the shaft is not installed or difficult to install a rotation speed measurement sensor device.

[0038] Example 2 Based on the vision and coding-based shaft speed measurement system provided in Example 1, this embodiment provides a vision and coding-based shaft speed measurement method, which includes the following steps: S1. Draw the coding pattern and print the coding strip.

[0039] Specifically, the process includes the following: S1.1. Draw a coding pattern based on binary two-dimensional coding: In this embodiment, an 8-bit binary two-dimensional coding strip is used as an example to illustrate, and an 8-bit binary two-dimensional coding black and white coding pattern is drawn. This coding is composed of black and white rectangles, black represents binary 0, white represents binary 1, and a multi-bit binary array is synthesized into a coding matrix. According to the accuracy requirements of the system, different binary digits can be selected. In this embodiment, an 8-bit binary two-dimensional coding pattern is used; the 8-bit binary two-dimensional coding can divide a circle of the shaft into 256 equal parts. The coding matrix corresponding to the 8-bit binary two-dimensional coding is as follows: Figure 3 shown.

[0040] S1.2. Calculate the circumference of the shaft: Calculate the circumference of the shaft according to the diameter or radius of the rotating shaft to be measured. The circumference of the shaft is the basis for determining the length of the encoding strip. Assuming the circumference of the shaft is L, the total length of the encoding strip should be equal to L.

[0041] S1.3, Print paper code: According to the calculated code pattern, print out a code strip equal to the circumference of the shaft. The code strip will be used to stick to the surface of the shaft to ensure the accuracy and clarity of the code pattern.

[0042] S2. Attachment of the coding strip: Attach the coding strip and wrap it around the circumference of the shaft to be tested. The specific requirements include the following: S2.1. Attach the code along the rotation direction of the shaft: The code strip should be tightly attached along the rotation direction of the shaft to ensure that each code stripe is correctly aligned. When attaching, avoid skewing or wrinkling the code to ensure the clarity and accuracy of the image.

[0043] S2.2. Ensure that the coding is connected from beginning to end: The beginning and end of the coding strip should be seamlessly connected to ensure that the coding can continuously cover the entire rotation cycle when the shaft rotates one circle, and each rotation angle corresponds to a unique coding mark.

[0044] S2.3. The encoding direction is parallel to the rotation direction: The encoding strips should be arranged in a way that ensures they are parallel to the rotation direction of the shaft (in the same direction or in the opposite direction) to avoid affecting the subsequent image decoding and angle calculation due to incorrect encoding direction.

[0045] S3. Install and adjust the high-speed camera. Specific requirements include the following: S3.1. Install the high-speed camera: Fix the high-speed camera on the camera bracket to ensure that the camera can stably capture the coded strip on the shaft. The installation location should be selected where the coded shaft section can be clearly captured to avoid vibration or other interference to the camera during the shooting process.

[0046] S3.2, adjust the camera position: through the adjustment function of the camera bracket, accurately adjust the horizontal and vertical position of the camera to ensure that the camera field of view can cover the entire encoding shaft section. The distance between the camera and the shaft should be moderate to avoid being too close or too far to affect the image clarity.

[0047] S3.3. Adjust the camera focus: adjust the camera focus according to the shooting field of view and imaging distance to ensure that the coding pattern is clearly visible and that the image coding stripes are not blurred during static shooting.

[0048] S3.4. Determine the viewing angle and shooting angle: The camera viewing angle and shooting angle should be adjusted to the optimal position to make the coded stripes clearly identifiable in the image and avoid distortion of the stripes due to excessive or small shooting angles.

[0049] S4, the high-speed camera is connected to the encoding visual computing module.

[0050] Specifically, it includes: S4.1. Cable connection: Use data cables and signal cables to connect the high-speed camera to the encoding vision computing module to ensure that image data and control signals can be transmitted between the encoding vision computing module and the camera in real time and at high speed; the data transmission speed should meet the real-time computing requirements of the system to avoid data loss or delay.

[0051] S4.2. Ensure stable connection: Test the data transmission channel to ensure there is no signal loss or interference, and ensure data stability and transmission quality.

[0052] S5. Data acquisition: Use a high-speed camera to continuously acquire the encoding image covering the entire encoding axis segment and transmit it to the encoding vision computing module.

[0053] Specifically, after the rotating shaft to be measured rotates, when measurement is required, the high-speed camera is triggered by the coding visual computing module to shoot and record each frame of the image. The high-speed camera will continuously shoot images of the coded shaft segment, and each frame of the coded image represents the angle information of the shaft at a certain moment. These image data will be transmitted to the coding visual computing module in real time for processing.

[0054] S6. Image processing and decoding calculation: The coding vision calculation module pre-processes each frame of the acquired coded image, extracts the coding value of the coded image, and parses the row number information of the corresponding coded image according to the coding value to obtain the corresponding absolute angle value, and then calculates the angle difference between two adjacent frames of coded images and calculates the instantaneous rotation speed of the shaft.

[0055] Specifically, the image processing and decoding calculation process is as follows: Figure 4 As shown, the process includes the following: S6.1. Image preprocessing: Each frame of the received coded image will first undergo image preprocessing, including cropping, denoising, contrast enhancement, sharpening, etc., to ensure that the coding pattern in the coded image is clear and recognizable.

[0056] S6.2, encoding and decoding: extract the encoding value located on the horizontal center line of the preprocessed encoded image; based on the encoding value, refer to the encoding matrix corresponding to the encoding pattern on the encoding strip to determine the row number information corresponding to the current encoded image. In some preferred embodiments, if the encoding value of the current encoded image does not find a matching row in the encoding matrix, the Hamming distance is used to find the nearest row from the screenwriter matrix, and the row number information of the row is used as the row number information of the current encoded image.

[0057] S6.3, Angle calculation: The actual coding value is obtained by real-time decoding of the currently captured coded image, and the axis angle value corresponding to the current coded image is calculated based on the row number information of the coded value in the entire coding matrix. The absolute angle value of the axis corresponding to the current frame image Calculated as: ; In the formula, For the i The number of rows obtained after decoding the frame-coded image, The number of rows obtained after decoding the first frame of the encoded image. For the i The number of full revolutions of the frame coded image relative to the axis of the first frame coded image; The difference in rotation angle between two adjacent frames of coded images is .

[0058] Calculate the instantaneous angular velocity of the axis corresponding to two adjacent frames of encoded images : ; In the formula, is the shooting interval of the high-speed camera, is the shooting frame rate of the high-speed camera; The instantaneous speed of the shaft is ; In addition, the direction of rotation of the shaft can be determined by observing whether the row position is increasing or decreasing.

[0059] In some preferred embodiments, the method further includes: S6.5, interpolation processing: in order to obtain more rotation angles and instantaneous speed values ​​at non-sampling moments, the rotation angle values ​​may be interpolated. Through a linear interpolation algorithm, the angle information of the shaft body at non-sampling moments may be calculated, thereby obtaining continuous rotation angles and instantaneous speed values.

[0060] The effect of the technical solution of the present invention is further explained below in conjunction with actual measured cases.

[0061] This case uses 8-bit binary two-dimensional encoding, shaft diameter: 100mm; shaft speed: 5000r / min. According to the shaft speed, the camera frame rate is set to 1600fps and the exposure time is 62.5μs. Some of the captured images are as follows Figure 5 Some of the measurement results are shown in Figure 6 As shown, the average relative error is 0.26%.

[0062] It can be understood that the same or similar parts of the above embodiments can be referenced to each other, and the contents not described in detail in some embodiments can refer to the same or similar contents in other embodiments.

[0063] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A shaft speed measurement system based on vision and encoding, characterized in that: include: The coding strip, on which the coding pattern adopts multi-bit binary two-dimensional coding, is multi-bit binary coding in the width direction, and the coding strip is divided into several rows in the length direction, and each row has a unique coding value; the length of the coding strip is equal to the circumference of the shaft body, and it is used to wrap around and stick to the circumferential surface of the shaft body to be tested for one circle; A high-speed camera is used to continuously capture images of the coded strips on the circumferential surface of the shaft to be measured; The coding vision calculation module is connected to the high-speed camera through the data transmission module, and is used to obtain the coded image captured by the high-speed camera and perform preprocessing, extract and analyze the coding value of each frame of the coded image, and then calculate the shaft rotation speed.

2. The shaft speed measurement system based on vision and encoding according to claim 1 is characterized in that: The coding pattern on the coding strip adopts 4-8-bit binary two-dimensional coding.

3. The shaft speed measurement system based on vision and encoding according to claim 1 or 2, characterized in that: The binary two-dimensional encoding method adopts binary Gray code.

4. The shaft speed measurement system based on vision and encoding according to claim 1 is characterized in that: Also included is a camera stand for fixing and adjusting the position of the high-speed camera.

5. A method for measuring shaft speed based on vision and coding, characterized in that: The method is implemented by using the vision and encoding based shaft speed measurement system as described in any one of claims 1 to 4, comprising the following steps: Paste the coding tape and wrap it around the circumference of the shaft to be tested; A high-speed camera is used to continuously collect coding images covering the entire coding axis segment and transmit them to the coding vision computing module; The coding vision calculation module preprocesses each frame of the acquired coded image, extracts the coding value of the coded image, and parses the row number information of the corresponding coded image according to the coding value to obtain the corresponding absolute angle value, and then calculates the angle difference between two adjacent frames of coded images and calculates the instantaneous rotation speed of the shaft.

6. The method for measuring shaft speed based on vision and coding according to claim 5, characterized in that: The step of extracting the code value of the coded image and parsing the row number information of the corresponding coded image according to the code value specifically includes: Extracting the code value located on the horizontal center line in the preprocessed code image; Based on the coding value, the row number information corresponding to the current coded image is determined with reference to the coding matrix corresponding to the coding pattern on the coding strip.

7. The method for measuring shaft speed based on vision and coding according to claim 6, characterized in that: If the encoding value of the current encoded image does not find a matching row in the encoding matrix, the Hamming distance is used to find the nearest row from the screenwriter matrix, and the row number information of the row is used as the row number information of the current encoded image.

8. The method for measuring shaft speed based on vision and coding according to claim 5, characterized in that: The rotation angle difference between two adjacent frames of coded images is obtained by the following method: Determine the i The absolute rotation angle of the axis corresponding to the frame encoding image : ； In the formula, For the i The number of rows obtained after decoding the frame-coded image, The number of rows obtained after decoding the first frame of the encoded image. For the i The number of full revolutions of the frame coded image relative to the axis of the first frame coded image; The difference in rotation angle between two adjacent frames of coded images is .

9. The method for measuring shaft speed based on vision and coding according to claim 8, characterized in that: The instantaneous speed of the shaft is obtained by the following method: Calculate the instantaneous angular velocity of the axis corresponding to two adjacent frames of encoded images : ； In the formula, is the shooting interval of the high-speed camera, is the shooting frame rate of the high-speed camera; The instantaneous speed of the shaft is .

10. The method for measuring shaft speed based on vision and coding according to claim 5, characterized in that: The interpolation algorithm is used to calculate the instantaneous speed of the shaft at the non-sampling moment, thereby obtaining the continuous instantaneous speed of the shaft.

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