A shaft instantaneous speed measuring device and method based on image correlation degree

Abstract

This invention relates to a device and method for measuring the instantaneous rotational speed of a rotating shaft based on image correlation, comprising a rotating shaft system, an area array camera, a data cable, and a computer. The method includes the following steps: adjusting the camera pose so that the target pattern is located at the center of the area array sensor; as the rotating shaft rotates, the end-face image on the imaging sensor also rotates with the shaft; during shaft vibration, the area array camera continuously images the end-face of the rotating shaft, and then transmits the resulting series of images to the computer via the data cable; finally, the end-face feature image sequence processing module and data processing module in the computer process the end-face feature image sequence, and calculate the instantaneous rotational speed information of the rotating shaft using the proposed rotational speed measurement method.

Description

Technical Field

[0001] This invention relates to the field of machine vision vibration measurement technology, and in particular to a device and method for measuring the instantaneous rotational speed of a rotating shaft based on image correlation. Background Technology

[0002] Shafts are essential components of various rotating machinery. Vibration monitoring of shafts during operation is crucial for the entire rotating machinery structure. Rotational speed information is a key parameter reflecting the operating status of rotating equipment. Currently, most traditional methods for measuring shaft rotational speed involve contact and non-contact tachometers. Contact tachometers can affect the rotational characteristics of the object being measured, resulting in poor measurement performance and low accuracy. Non-contact tachometers mainly include electromagnetic and photoelectric tachometers, but magnetic tachometers require a magnet to be installed on the object being measured, and photoelectric tachometers perform poorly in dusty environments. Therefore, traditional rotational speed measurement methods have significant limitations. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide a device and method for measuring the instantaneous rotational speed of a rotating shaft based on image correlation. The device and method utilize an area array camera to continuously image the end face of the rotating shaft, and process the images through a computer image processing module and a data processing module to realize the instantaneous rotational speed measurement of the rotating shaft. The measuring device is simple and has high measurement efficiency.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: A device for measuring the instantaneous rotational speed of a rotating shaft based on image correlation, comprising... A target pattern is installed on the end face of the shaft to sense the rotational speed of the shaft; A single-array camera continuously acquires images of the contour features of the rotating shaft end face, and transmits the acquired end face contour feature image sequence to the computer image processing module via a data cable; A data cable is used for communication, control, and data transmission between the area scan camera and the computer. A computer controls the frame rate, image grayscale, brightness, etc. of the array camera sampling, and processes the feature image sequence transmitted to the computer to obtain the rotation speed information of the shaft. A target pattern sequence processing software module is installed in the computer to process the pattern sequence signal and calculate the shaft rotation speed signal.

[0005] In a preferred embodiment: the target pattern is a target pattern sticker, which is obtained by a printer. The front side is a square target image and the back side is an adhesive layer, used to sense the rotational speed information of the shaft.

[0006] In a preferred embodiment: the target pattern sticker has a black square pattern, the diagonal length of which is equal to the diameter of the pivot.

[0007] In a preferred embodiment: when the area array camera captures the target pattern, its imaging optical axis is perpendicular to the plane of the target pattern, and the center of the positional fringe is imaged onto the area array camera as much as possible.

[0008] In a preferred embodiment: the rotating shaft is driven by a motor, thereby causing the end face target pattern to change position.

[0009] In a preferred embodiment: the area array camera continuously images the target pattern on the end face of the rotating shaft, and stores each frame of the target pattern sequence in a computer.

[0010] In a preferred embodiment: the target pattern sequence processing software module can obtain the correlation signal between adjacent frame square target patterns.

[0011] In a preferred embodiment: the image processing module obtains the number of cycles generated per revolution of the target pattern.

[0012] In a preferred embodiment: the instantaneous rotational speed measurement of the shaft requires correlation-speed curve calibration.

[0013] This invention also provides a method for measuring the instantaneous rotational speed of a rotating shaft based on image correlation. The method employs the aforementioned image correlation-based instantaneous rotational speed measuring device, and the correlation-speed curve calibration includes the following steps: Step S1: Determine the system's sampling frame rate, and obtain the system's maximum measured rotational speed based on the sampling frame rate. The formula for calculating the system's maximum measured rotational speed is as follows:

[0014] in f The system's sampling frame rate, k The number of cycles generated for the target pattern; Step S2: Within the allowable maximum speed range, select m , m >10 sets of constant speed operating conditions were set, and target pattern sequences under m sets of constant speed operating conditions were collected. The correlation signal between adjacent frames of the target pattern sequence acquired at each constant speed was calculated, and the average value was used as the correlation calibration point at that speed. The mathematical formula is as follows:

[0015] Where N is the number of target patterns acquired under a certain constant speed condition. r 12 , r23 ... r N-1，N The correlation between the first and second frames, the correlation between the second and third frames, and the correlation between the (N-1)th and Nth images in the target pattern sequence under constant speed conditions; Step S3: Repeat step S2 for the target pattern sequence obtained under each constant speed condition, that is, obtain multiple sets of correlation-speed calibration points; Step S4: Perform curve fitting on the obtained multiple sets of correlation-speed calibration points to obtain the correlation-speed curve of the measurement system; The correlation signal between target patterns at any two time points is interpolated onto the correlation-rotation speed calibration curve to obtain the instantaneous rotation speed information of the shaft.

[0016] Compared with the prior art, the present invention has the following advantages: (1) The method only requires the use of an area array camera to continuously image the end face of the shaft and process the acquired feature images to realize the instantaneous rotation speed measurement of the shaft. (2) The present invention can realize the instantaneous rotation speed measurement of the shaft by using an area array sensor. Compared with the traditional tachometer method for measuring rotation speed, the measurement accuracy is higher, the cost is more economical, and the measurement efficiency is higher. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the device structure according to a preferred embodiment of the present invention; Figure 2 The target pattern designed in the preferred embodiment of the present invention can be pasted onto the end face of the rotating shaft; Figure 3 This is a correlation-speed curve obtained by fitting correlation-speed calibration points in a preferred embodiment of the present invention; Figure 4 This is a flowchart illustrating the measurement process of measuring the instantaneous rotational speed of a shaft using image correlation, according to a preferred embodiment of the present invention.

[0018] In the diagram, 1-area array camera, 2-camera bracket, 3-data cable, 4-computer, 5-target pattern, 6-rotating axis. Detailed Implementation

[0019] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0020] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0021] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations according to this application; as used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise; furthermore, it should be understood that when the terms “comprising” and / or “including” are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0022] Figure 1 This is a schematic diagram of the device structure according to an embodiment of the present invention. Figure 1 As shown, this embodiment provides a three-dimensional vibration displacement measurement device for a rotating shaft based on an area array camera, including an area array camera 1, a camera bracket 2, a data cable 3, a computer 4, a target pattern 5, and a rotating shaft 6. The area array camera 1 continuously acquires and records the target pattern 5 on the end face of the rotating shaft, and the computer 4 is equipped with an image sequence processing software module and a data processing module, which can calculate the correlation signal between the target pattern sequences of the image sequences transmitted to the computer.

[0023] Target pattern 5 is installed on the end face of the rotating shaft to sense the rotational speed information of the rotating shaft; The area scan camera 1 continuously acquires images of the contour features of the rotating shaft end face, and transmits the acquired end face contour feature image sequence to the computer image processing module via a data cable; Data cable 3 is used for communication, control, and data transmission between the area scan camera and the computer. Computer 4 controls the frame rate, image grayscale, brightness, etc. of the array camera sampling, and processes the feature image sequence transmitted to the computer to obtain the rotation speed information of the rotating shaft. The target pattern 5 sequence processing software module is installed in the computer 4 to process the pattern sequence signal and calculate the shaft rotation speed signal.

[0024] The target pattern sticker 5 is obtained by printing. The front side is a square target image and the back side is an adhesive layer, which is used to sense the rotation speed information of the shaft.

[0025] The target pattern 5 sticker has a black square pattern, and the diagonal length of the black square pattern is equal to the diameter of the rotating shaft.

[0026] When the area array camera captures the target pattern, its imaging optical axis is perpendicular to the plane of the target pattern, and it tries to make the center of the positional fringe image onto the area array camera.

[0027] The rotating shaft is driven by a motor, thereby causing changes in the pose of the target pattern on the end face.

[0028] The area array camera 1 continuously images the target pattern on the end face of the rotating shaft and stores each frame of the target pattern sequence in the computer.

[0029] The target pattern sequence processing software module can obtain the correlation signal between adjacent frame square target patterns.

[0030] The image processing module obtains the number of cycles generated per revolution of the target pattern.

[0031] The instantaneous rotational speed measurement of the shaft requires correlation-speed curve calibration.

[0032] The specific implementation steps are as follows: Step S1: Determine the system's sampling frame rate before measurement, and obtain the system's maximum measurement speed based on the sampling frame rate. The formula for calculating the system's maximum measurement speed is as follows:

[0033] in f The system's sampling frame rate, k The number of cycles generated for the target pattern.

[0034] Step S2: Within the allowable maximum speed range, select N ( N >10) sets of constant speed operating conditions, and data collection N For a set of target pattern sequences under constant speed conditions, the correlation signal between adjacent frames of the target pattern sequence acquired at each constant speed is calculated, and the average value is used as the correlation calibration point at that speed. The mathematical formula is as follows:

[0035] Where N is the number of target patterns collected under a certain constant speed condition, r12, r23... rN-1, and N is the correlation between the first and second frames, the second and third frames, and the N-1th and Nth images in the target pattern sequence under the constant speed condition.

[0036] Step S3: Repeat step S2 for each target pattern sequence obtained under constant speed conditions to obtain multiple sets of correlation-speed calibration points.

[0037] Step S4: Perform curve fitting on the obtained multiple sets of correlation-speed calibration points to obtain the correlation-speed curve of the measurement system.

[0038] Finally, the instantaneous rotational speed of the shaft can be characterized by the correlation signal between the target patterns at any two moments, which is used to interpolate the correlation-rotational speed calibration curve.

[0039] This invention only requires using an area array camera to continuously image the end face of the rotating shaft and process the acquired feature images to achieve instantaneous rotational speed measurement of the rotating shaft. Compared with existing measurement methods, it not only reduces hardware costs but also reduces the amount of data collected, making rotational speed signal extraction faster and more efficient, and improving the efficiency of rotational speed measurement.

Claims

1. A device for measuring the instantaneous rotational speed of a rotating shaft based on image correlation, characterized in that: include A target pattern is installed on the end face of the shaft to sense the rotational speed of the shaft; A single-array camera continuously acquires images of the contour features of the rotating shaft end face, and transmits the acquired end face contour feature image sequence to the computer image processing module via a data cable; A data cable is used for communication, control, and data transmission between the area scan camera and the computer. A computer controls the frame rate, image grayscale, and brightness of the array camera sampling, and simultaneously processes the feature image sequence transmitted to the computer to obtain the rotation speed information of the rotating shaft. A target pattern sequence processing software module is installed in the computer to process the pattern sequence signal and calculate the shaft rotation speed signal; The instantaneous rotational speed measurement of the shaft requires correlation-speed curve calibration; the correlation-speed curve calibration includes the following steps: Step S1: Determine the system's sampling frame rate, and obtain the system's maximum measured rotational speed based on the sampling frame rate. The formula for calculating the system's maximum measured rotational speed is as follows: ,in f The system's sampling frame rate, k The number of cycles generated for the target pattern; Step S2: Within the allowable maximum speed range, select m , m >10 sets of constant speed operating conditions were set, and target pattern sequences under m sets of constant speed operating conditions were collected. The correlation signal between adjacent frames of the target pattern sequence acquired at each constant speed was calculated, and the average value was used as the correlation calibration point at that speed. The mathematical formula is as follows: Where N is the number of target patterns collected under a certain constant speed condition. r 12 , r 23 ... r N-1，N The correlation between the first and second frames, the correlation between the second and third frames, and the correlation between the (N-1)th and Nth images in the target pattern sequence under constant speed conditions are given. Step S3: Repeat step S2 for the target pattern sequence obtained under each constant speed condition, that is, obtain multiple sets of correlation-speed calibration points; Step S4: Perform curve fitting on the obtained multiple sets of correlation-speed calibration points to obtain the correlation-speed curve of the measurement system; The correlation signal between target patterns at any two time points is interpolated onto the correlation-rotation speed calibration curve to obtain the instantaneous rotation speed information of the shaft.

2. The instantaneous rotational speed measurement device for a rotating shaft based on image correlation according to claim 1, characterized in that: The target pattern is a target pattern sticker, which is obtained by printing. The front side is a square target image, and the back side is an adhesive layer, used to sense the rotational speed information of the shaft.

3. The instantaneous rotational speed measurement device for a rotating shaft based on image correlation according to claim 2, characterized in that: The target pattern sticker has a black square pattern, and the diagonal length of the black square pattern is equal to the diameter of the rotating shaft.

4. The instantaneous rotational speed measurement device for a rotating shaft based on image correlation according to claim 1, characterized in that: When the area array camera captures the target pattern, its imaging optical axis is perpendicular to the plane of the target pattern, and it tries to make the center of the positional fringe image onto the area array camera.

5. The instantaneous rotational speed measurement device for a rotating shaft based on image correlation according to claim 1, characterized in that: The rotating shaft is driven by a motor, thereby causing changes in the pose of the target pattern on the end face.

6. The instantaneous rotational speed measurement device for a rotating shaft based on image correlation according to claim 1, characterized in that: The area array camera continuously images the target pattern on the end face of the rotating shaft and stores each frame of the target pattern sequence in the computer.

7. The instantaneous rotational speed measurement device for a rotating shaft based on image correlation according to claim 1, characterized in that: The target pattern sequence processing software module can obtain the correlation signal between adjacent frame square target patterns.

8. The instantaneous rotational speed measurement device for a rotating shaft based on image correlation according to claim 1, characterized in that: The image processing module obtains the number of cycles generated per revolution of the target pattern.

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