CN109558871B - Pointer instrument reading identification method and device - Google Patents
Pointer instrument reading identification method and device Download PDFInfo
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- CN109558871B CN109558871B CN201811258560.1A CN201811258560A CN109558871B CN 109558871 B CN109558871 B CN 109558871B CN 201811258560 A CN201811258560 A CN 201811258560A CN 109558871 B CN109558871 B CN 109558871B
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06V—IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING
- G06V10/00—Arrangements for image or video recognition or understanding
- G06V10/20—Image preprocessing
- G06V10/25—Determination of region of interest [ROI] or a volume of interest [VOI]
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06V—IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING
- G06V10/00—Arrangements for image or video recognition or understanding
- G06V10/20—Image preprocessing
- G06V10/24—Aligning, centring, orientation detection or correction of the image
- G06V10/243—Aligning, centring, orientation detection or correction of the image by compensating for image skew or non-uniform image deformations
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06V—IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING
- G06V2201/00—Indexing scheme relating to image or video recognition or understanding
- G06V2201/02—Recognising information on displays, dials, clocks
Abstract
The invention provides a method and a device for identifying the reading of a pointer instrument, which effectively avoid identifying more and complicated scale marks in the instrument, eliminate errors in identifying the scale marks of the instrument, greatly improve the identification precision of the reading of the pointer instrument, avoid using complex algorithms due to the fact that algorithms such as Hough transformation, least square method and the like are not used, greatly improve the operation speed and ensure better real-time property.
Description
Technical Field
The invention relates to the technical field of computer vision, in particular to a method for identifying the reading of a pointer instrument.
Background
The pointer type instrument is used as a traditional measuring instrument, has the advantages of simple structure, convenience in maintenance, low price, high reliability, strong adaptability, small environmental influence and the like, is widely applied to the fields of scientific experiments, industrial production and the like, and has an irreplaceable position after the appearance of a digital instrument.
At present, most methods for acquiring the readings of the pointer type instruments still adopt manual observation of the readings of the dial plate of the instrument, and the methods are greatly influenced by subjective factors and objective conditions. For example, the observation angle, the observation distance and the judgment and estimation ability of the reader are different, so that the reading error is large, the reliability is low, once the real-time monitoring is needed, the attendance of workers is needed, the labor intensity is increased, and the safety is reduced; on the other hand, if the environment for installing the instrument is severe, the instrument may not be beneficial to manual reading, for example, the installed position is too high to the ground, or the working environment is high in temperature. Therefore, with the continuous development and the increasing maturity of computer vision technology, image processing technology and other technologies, the introduction of computer vision technology to meter reading is a necessary trend.
The automatic identification of the instrument is realized by utilizing a computer vision technology, an industrial camera is used for replacing human eyes, the error caused by human factors can be effectively eliminated, the reliability is improved, the labor consumption is reduced, and the real-time monitoring of the instrument is realized. The identification of the reading of the pointer type instrument mainly relates to two aspects, namely the identification and the positioning of the scale mark and the pointer of the instrument on the one hand, and the interpretation of the actual reading of the instrument on the other hand. The computer vision and image processing technology is used for identifying and positioning the scale lines and the pointers of the instrument, methods such as a Hough transformation algorithm, a least square algorithm, a difference image method, a central projection method, a template characteristic method and the like are mainly used, and in the aspect of interpretation of the indication value of the pointer instrument, the adopted methods are mainly classified into an angle method and a distance method and improved methods thereof. The above methods have disadvantages in themselves, and many researchers have been improving the methods or selecting a combination of methods, but there is still no method that can be recognized as optimal in all aspects.
Disclosure of Invention
The embodiment of the invention provides a method and a device for identifying the reading of a pointer instrument, which avoid identifying the scale mark of the instrument, eliminate the error of identifying the scale of the instrument, improve the identification precision of the reading of the pointer instrument, avoid the use of a complex algorithm, improve the operation speed and ensure better real-time property.
In a first aspect, the present invention provides a pointer instrument reading identification method, including:
when a pointer of the pointer instrument is at an initial position, acquiring a first image of the pointer instrument, wherein the first image has a characteristic mark point;
identifying and positioning a dial and a zero indicator for the first image, and determining a zero angle by using the characteristic mark points;
acquiring a second image of the pointer instrument in real time, and identifying and positioning a dial plate and a current pointer of the second image;
acquiring a characteristic mark point in the second image, and determining the current pointer angle of the pointer instrument by using the position relation between the current pointer and the characteristic mark point;
and determining the current reading of the pointer instrument by using the zero position angle determined by the first image and the current pointer angle determined by the second image.
As an alternative, the method for acquiring a first image of the pointer instrument when the pointer of the pointer instrument is at the initial position, wherein the first image has a characteristic mark point, further includes:
a characteristic pattern is placed on the dial plate of the pointer instrument to serve as a characteristic mark point, and the area where the characteristic pattern is located is an area not swept by an instrument pointer;
the camera is aligned to the pointer instrument, so that the instrument can clearly and completely image in the camera;
the relative height of the camera and the instrument is ensured to be within the depth of field range of the camera, the instrument dial is adjusted according to the included angle between the optical axis of the camera and the perpendicular line of the center of the instrument until complete imaging is achieved, and the instrument is adjusted to be wholly within the camera view field according to the horizontal relative position of the camera and the instrument, and the dial is imaged completely;
when the pointer instrument is in a dark environment without natural light, the active illumination light source is adopted for illumination.
As an alternative, the acquiring a first image of the pointer instrument when the pointer of the pointer instrument is at the initial position, the first image having a characteristic mark point, includes:
acquiring a pointer zero position image of a pointer instrument by using a camera;
carrying out distortion correction on the acquired pointer zero position image according to camera parameters obtained by calibrating a camera to obtain a distortion corrected image;
and carrying out edge detection on the image after distortion correction to obtain an edge detection image of the zero position of the pointer type instrument.
As an alternative, the identifying and positioning of the dial and the null pointer for the first image, and the determining of the null angle using the characteristic mark points, includes:
carrying out contour extraction calculation on the edge detection image to obtain all contours in the edge detection image;
determining the range of the number of pixels forming the dial plate in the edge detection image according to the actual size of the dial plate of the pointer instrument, the camera parameters obtained by calibration and the distance between the camera and the dial plate, and extracting the contour of the dial plate according to the distribution characteristics of the internal gray value and the external gray value of the edge of the dial plate to finish the identification of the dial plate;
carrying out ellipse fitting on the extracted dial contour to obtain a position coordinate of the center of the dial in the image, the size of a long axis and a short axis of the dial ellipse and an inclination angle of the dial in the edge detection image;
intercepting an image of a dial area in a zero position image of a pointer of the pointer instrument after distortion correction, wherein the intercepted range is a square area with the center of the dial as an intercepted center and the side length being 1.5 times of the length of a major axis of a fitting ellipse of the dial, carrying out affine transformation on the intercepted image according to the inclination angle of the dial in the image and the sizes of the major axis and the minor axis, and adjusting the dial inclined into the ellipse in the image into a perfect circle dial;
carrying out binarization processing on the intercepted and affine transformed right circular dial image;
in the binary image, the center of a dial is taken as the center of a circle, the length of 0.2 times of the radius of the dial is taken as the scanning radius, and the gray value and the corresponding coordinate of one circle in the image are obtained at the scanning interval of 1 degree;
extracting a continuous interval with the gray value of 0, recording the interval width and the central coordinate of the 0-value interval, and sequencing according to the interval width, wherein the central coordinate of the 2 nd wide 0-value interval is used as a zero pointer pointing coordinate, and the coordinate and the dial central coordinate form a zero pointer vector to complete the identification and positioning of the zero pointer;
extracting the mark point from the circular dial image after binarization processing, carrying out contour extraction and ellipse fitting, positioning the circle center coordinate of the mark point, and forming a basic reference vector by the coordinate and the dial center coordinate;
and calculating the included angle of the two vectors by using a zero pointer vector and a basic reference vector according to a vector included angle formula, wherein the included angle is the angle of the zero position of the pointer relative to the reference mark point, and the angle is determined as the zero position angle of the pointer to finish the identification of the zero position of the pointer.
As an optional solution, the method further comprises:
and repeating the identification of the zero position of the pointer for multiple times to carry out average value operation on the zero position angle of the pointer as the zero position angle.
As an alternative, the acquiring a second image of the pointer instrument in real time, and identifying and positioning the dial and the current pointer on the second image includes:
distortion correction is carried out on an original image of the pointer instrument which is acquired by a camera in real time and is in real time in the working process according to camera calibration parameters to obtain a pointer instrument image after distortion correction;
performing edge detection on the image after distortion correction to obtain a real-time edge detection image of the real-time pointer instrument in work;
performing contour extraction operation on the real-time edge detection image to obtain all contours in the edge detection image, performing primary screening according to the number of pixels forming the contours, wherein the screening range is given by the size range of pixels imaged by a pointer instrument in a camera, and the screening range is calculated according to camera calibration parameters and the position relation between the camera and the pointer instrument;
carrying out ellipse fitting on the outline, detecting the deviation degree of pixel points forming the outline from the fitting ellipse, extracting the outline of the pointer instrument, and obtaining the central coordinate of the dial plate of the pointer instrument in the image of the pointer instrument in work, the length of the long axis and the short axis of the imaging ellipse of the dial plate and the rotating angle through ellipse fitting calculation;
according to ellipse fitting information of the dial plate of the pointer instrument acquired in real time, an image of the dial plate part is intercepted from the pointer instrument image after distortion correction, and the intercepted range is a square area which takes the central coordinate of the dial plate in the image as the center and has the side length 1.5 times of the length of the long axis of ellipse fitting of the dial plate;
and performing affine transformation on the captured dial area image of the pointer instrument according to the inclination angle and the major and minor axis sizes of the dial in the captured dial area image of the pointer instrument, and adjusting the dial inclined into an ellipse in the distortion-corrected dial image of the pointer instrument into a perfect circle dial.
As an alternative, the acquiring a feature mark point in the second image, and determining a current reading of the pointer instrument by using a position relationship between a current pointer and the feature mark point includes:
the method comprises the steps of identifying and positioning the position of a pointer of an instrument in work in real time, identifying characteristic mark points, calculating an included angle between the pointer in work and the mark points, wherein the included angle has directivity, and the calculated included angle is an angle formed by rotating the pointer position around the center of the instrument anticlockwise to the mark points.
As an optional solution, the real-time identifying and locating the pointer position of the instrument in operation, identifying the characteristic mark point, calculating an angle between the pointer in operation and the mark point, where the angle has directivity, and the calculated angle is an angle between the pointer position and the mark point, and rotating counterclockwise around the instrument center, and performing real-time interpretation on the reading number of the pointer instrument in operation to obtain the current reading of the pointer instrument, includes:
carrying out binarization processing on the intercepted and affine transformed right circular dial plate image, effectively protruding a pointer part by reasonably setting a binarization threshold value, and scanning counterclockwise to obtain a circle of gray value and coordinates thereof in the binarization image by taking the center of the dial plate as a circle center, taking the length of 0.2 times of the radius of the dial plate as a scanning radius and taking the scanning interval of 1 degree;
extracting a continuous interval with the gray value of 0, recording the interval width and the center coordinate of the 0-value interval, sorting according to the interval width, wherein the 2 nd-wide 0-value interval center coordinate is the pointing coordinate of the pointer, and calculating according to the pointer coordinate and the dial center coordinate to obtain a real-time pointer vector;
acquiring the position of the characteristic mark point in real time, identifying and extracting the characteristic mark point, calculating the image position coordinate of the characteristic mark point by using an ellipse fitting algorithm, and calculating a real-time basic reference vector according to the central coordinate of the instrument;
calculating an included angle between a real-time pointer vector and a real-time basic reference vector by using a point multiplication formula of the vector, and judging whether the angle between the pointer vector and the basic reference vector exceeds 180 degrees or not by using a vector direction obtained by a cross multiplication formula of the vector, wherein for the condition of exceeding 180 degrees, the included angle calculated by the vector point multiplication formula needs to be subtracted by 360 degrees to obtain the angle between the final pointer vector and the basic reference vector;
subtracting the zero position angle from the current pointer angle from the pointer vector obtained in real time to the basic reference vector to obtain the real-time rotation angle of the pointer in the working of the pointer instrument relative to the initial position;
optionally, the determining a current reading of the pointer instrument using the zero angle determined by the first image and the current pointer angle determined by the second image includes: and calculating to obtain the reading of the pointer instrument according to the corresponding relation between the index value of the pointer instrument and the rotation angle of the pointer by utilizing the real-time rotation angle and the initial angle of the zero position of the pointer relative to the 0 position of the scale mark.
In a second aspect, the present invention provides a pointer instrument reading identification apparatus, including:
the device comprises an image acquisition unit, a processing unit and a display unit, wherein the image acquisition unit is used for acquiring a first image of the pointer instrument when a pointer of the pointer instrument is at an initial position, and the first image is provided with characteristic mark points;
the image processing unit is used for identifying and positioning the dial and the zero pointer of the first image and determining a zero angle by using the characteristic mark point;
the image acquisition unit is also used for acquiring a second image of the pointer instrument in real time and identifying and positioning a dial plate and a current pointer of the second image;
the image processing unit is further used for acquiring a characteristic mark point in the second image and determining the current reading of the pointer instrument by using the position relation between the current pointer and the characteristic mark point.
According to the technical scheme, the embodiment of the invention has the following advantages:
the invention provides a method and a device for identifying the reading of a pointer instrument, which effectively avoid identifying more and complicated scale marks in the instrument, eliminate errors in identifying the scale marks of the instrument, greatly improve the identification precision of the reading of the pointer instrument, avoid using complex algorithms due to the fact that algorithms such as Hough transformation, least square method and the like are not used, greatly improve the operation speed and ensure better real-time property.
Drawings
FIG. 1 is a flow chart of one embodiment of a pointer meter reading identification method provided in embodiments of the present invention;
FIG. 2 is a schematic view of a dial plate in an embodiment of the pointer instrument reading identification apparatus provided in the embodiment of the present invention;
fig. 3 is a block diagram of an embodiment of a pointer instrument reading identification apparatus provided in an embodiment of the present invention.
Detailed Description
In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The terms "first," "second," "third," "fourth," and the like in the description and in the claims, as well as in the drawings, are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It will be appreciated that the data so used may be interchanged under appropriate circumstances such that the embodiments described herein may be practiced otherwise than as specifically illustrated or described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
Referring to fig. 1, the present invention provides a reading identification method for a pointer instrument, including:
s101, when a pointer of the pointer instrument is at an initial position, a first image of the pointer instrument is obtained, and the first image is provided with a characteristic mark point.
A characteristic pattern is placed on the dial of the pointer instrument as a mark point, the area where the characteristic pattern is located is an area not swept by an instrument pointer, the characteristic pattern can be recognized, and the unique coordinate of the characteristic pattern on the instrument can be determined through the characteristic of the pattern. The characteristic patterns can be characteristic circle patterns of a black ring with a certain width at the periphery of a white circle inside, or characteristic circle patterns of a complete circle formed by alternating white quarter circles and black quarter circles, and other patterns capable of determining unique position coordinates according to characteristics; in the embodiment of the invention, the camera is an industrial camera of a certain model, and the position relation between the camera and the instrument comprises the following steps: the relative height of the camera and the instrument ensures that the included angle between the optical axis of the camera and the central perpendicular line of the instrument can be changed within the range of ensuring the complete imaging of the instrument dial plate until the complete imaging of the instrument dial plate is obtained, the horizontal relative position of the camera and the instrument ensures that the instrument is integrated in the visual field of the camera and ensures the complete imaging of the dial plate, and if the instrument is in a dark environment without natural light, the instrument image acquisition is carried out, and the instrument is provided with an active lighting source.
S102, identifying and positioning a dial and a zero pointer of the first image, and determining a zero angle by using the characteristic mark points.
Carrying out contour extraction calculation on the edge detection image to obtain all contours in the edge detection image;
determining the range of the number of pixels forming the dial plate in the edge detection image according to the actual size of the dial plate of the pointer instrument, the camera parameters obtained by calibration and the distance between the camera and the dial plate, and extracting the contour of the dial plate according to the distribution characteristics of the internal gray value and the external gray value of the edge of the dial plate to finish the identification of the dial plate;
carrying out ellipse fitting on the extracted dial contour to obtain a position coordinate of the center of the dial in the image, the size of a long axis and a short axis of the dial ellipse and an inclination angle of the dial in the edge detection image;
intercepting an image of a dial area in a zero position image of a pointer of the pointer instrument after distortion correction, wherein the intercepted range is a square area with the center of the dial as an intercepted center and the side length being 1.5 times of the length of a major axis of a fitting ellipse of the dial, carrying out affine transformation on the intercepted image according to the inclination angle of the dial in the image and the sizes of the major axis and the minor axis, and adjusting the dial inclined into the ellipse in the image into a perfect circle dial;
carrying out binarization processing on the intercepted and affine transformed right circular dial image;
in the binary image, the center of a dial is taken as the center of a circle, the length of 0.2 times of the radius of the dial is taken as the scanning radius, and the gray value and the corresponding coordinate of one circle in the image are obtained at the scanning interval of 1 degree;
extracting a continuous interval with the gray value of 0, recording the interval width and the central coordinate of the 0-value interval, and sequencing according to the interval width, wherein the central coordinate of the 2 nd wide 0-value interval is used as a zero pointer pointing coordinate, and the coordinate and the dial central coordinate form a zero pointer vector to complete the identification and positioning of the zero pointer;
extracting the mark points from the circular dial image after binarization processing, carrying out contour extraction and ellipse fitting, positioning the coordinates of the circle center of the mark points, and forming basic reference vectors by the coordinates and the dial center coordinates;
and calculating the included angle of the two vectors by using a zero pointer vector and a basic reference vector according to a vector included angle formula, wherein the included angle is the angle of the zero position of the pointer relative to the reference mark point, and the angle is determined as the zero position angle of the pointer to finish the identification of the zero position of the pointer.
In this embodiment, the zero recognition process may be repeated multiple times to obtain an average value, thereby improving the accuracy.
S103, acquiring a second image of the pointer instrument in real time, and identifying and positioning the dial plate and the current pointer of the second image.
Performing distortion correction on a second image of a pointer instrument in work acquired by a camera in real time according to camera calibration parameters to obtain an instrument image after distortion correction, performing edge detection on the image after distortion correction to obtain a real-time edge detection image of the instrument in work, performing contour extraction operation on the real-time edge detection image to obtain all contours in the edge detection image, performing primary screening according to the number of pixels forming the contours, wherein the screening range is given by the pixel size range of the instrument imaged in the camera used in the embodiment, the pixel size range is determined by the spatial resolution of the selected camera, calculating according to the camera calibration parameters and the position relation of the camera and the instrument, performing ellipse fitting on the remaining contours after primary screening of the contours, detecting the degree of deviation of pixel points forming the contours from fitting ellipses, and extracting the instrument contour according to the distribution characteristics of the gray values of the instrument edge, obtaining the central coordinate of the instrument dial in the image in work, the length of the long axis and the short axis of the imaging ellipse of the dial and the rotation angle of the imaging ellipse of the dial by ellipse fitting calculation, intercepting the image of the dial part in the instrument image after distortion correction according to the ellipse fitting information of the pointer instrument dial acquired in real time, wherein the intercepted range is a square area with the central coordinate of the dial in the image as the center and the side length being 1.5 times of the length of the long axis of the ellipse fitting of the dial, carrying out affine transformation on the intercepted image of the instrument dial area, and adjusting the dial inclined into the ellipse in the image into a perfect circular dial so as to be convenient for subsequent pointer identification and positioning;
s104, obtaining the characteristic mark points in the second image, and determining the current pointer angle of the pointer instrument by using the position relation between the current pointer and the characteristic mark points.
The method comprises the steps of identifying and positioning the position of a pointer of an instrument in work in real time, identifying characteristic mark points, calculating an included angle between the pointer in work and the mark points, wherein the included angle has directivity, and the calculated included angle is an angle formed by rotating the pointer position around the center of the instrument anticlockwise to the mark points.
Specifically, a circle-right dial image which is intercepted and subjected to affine transformation is subjected to binarization processing, a pointer part can be effectively protruded by reasonably setting a binarization threshold value, a circle center is taken as a circle center, 0.2 time of the dial radius is taken as a scanning radius, and a circle of gray value and coordinates thereof in the binarization image are obtained by anticlockwise scanning at a scanning interval of 1 degree;
extracting a continuous interval with the gray value of 0, recording the interval width and the center coordinate of the 0-value interval, sorting according to the interval width, wherein the 2 nd-wide 0-value interval center coordinate is the pointing coordinate of the pointer, and calculating according to the pointer coordinate and the dial center coordinate to obtain a real-time pointer vector;
acquiring the position of the characteristic mark point in real time, identifying and extracting the characteristic mark point, calculating the image position coordinate of the characteristic mark point by using an ellipse fitting algorithm, and calculating a real-time basic reference vector according to the central coordinate of the instrument;
calculating an included angle between a real-time pointer vector and a real-time basic reference vector by using a point multiplication formula of the vector, and judging whether the angle from the pointer vector to the basic reference vector exceeds 180 degrees or not by using a vector direction obtained by a cross multiplication formula of the vector, wherein for the condition of exceeding 180 degrees, the included angle calculated by the vector point multiplication formula needs to be subtracted by 360 degrees to obtain the current pointer angle from the final pointer vector to the basic reference vector;
and S105, determining the current reading of the pointer instrument by using the zero position angle determined by the first image and the current pointer angle determined by the second image.
And according to the relation of the division values between the dial scales and the pointer rotation angles, the number of the pointer instrument in the working process is interpreted in real time to obtain the current reading of the pointer instrument.
Specifically, subtracting the zero position angle determined by the first image from the current pointer angle from the pointer vector obtained in real time to the basic reference vector to obtain the real-time rotation angle of the pointer in the working of the pointer instrument relative to the initial position;
and calculating to obtain the reading of the pointer instrument according to the corresponding relation between the index value of the pointer instrument and the rotation angle of the pointer by utilizing the real-time rotation angle and the initial angle of the zero position of the pointer relative to the 0 position of the scale mark, and finishing the real-time interpretation of the reading of the pointer instrument.
The invention provides a method for identifying the reading of a pointer instrument, which effectively avoids identifying more and complicated scale marks in the instrument, eliminates errors in identifying the scale marks of the instrument, greatly improves the identification precision of the reading of the pointer instrument, avoids using complex algorithms due to the fact that algorithms such as Hough transformation, least square method and the like are not used, greatly improves the operation speed, and ensures better real-time property.
In another embodiment of the method for identifying the reading of the pointer instrument, the pointer instrument takes a pressure gauge as an example, and the method includes the steps of acquiring an image of the pointer pressure gauge, identifying the zero position of a pointer of the pointer pressure gauge and identifying the reading of the pointer pressure gauge, which are described in detail below.
S1.1 acquisition of pointer type pressure gauge images
The acquisition of the pointer type pressure gauge image comprises the steps that a characteristic pattern is placed on a dial plate of the pointer type pressure gauge as a mark point, the area where the characteristic pattern is located is an area not swept by a pointer of the pressure gauge, the characteristic pattern can be identified, and the unique coordinate of the characteristic pattern on the pressure gauge can be determined through pattern characteristics.
The characteristic pattern can be a characteristic circle pattern of a black ring with a certain width at the periphery of a white circle, or a characteristic circle pattern of a complete circle formed by alternating white quarter circles and black quarter circles, and other patterns capable of determining unique position coordinates according to characteristics.
Referring to fig. 2, a unit of the pointer type pressure gauge to be identified according to an embodiment of the present invention is MPa, and the provided characteristic pattern is a characteristic circle pattern of a black ring with a certain width on the periphery of an internal white circle.
The camera is aligned to the pointer type pressure gauge, so that the pressure gauge can clearly and completely image in the camera; in the embodiment of the invention, the camera is an industrial camera of a certain model, and the position relation between the camera and the pressure gauge comprises the following steps: the relative height of the camera and the pressure gauge ensures that the included angle between the optical axis of the camera and the central perpendicular line of the pressure gauge can be changed within the range of ensuring the complete imaging of the dial plate of the pressure gauge within the range of the depth of field of the camera, and the horizontal relative position of the camera and the pressure gauge ensures that the pressure gauge is wholly within the visual field of the camera and ensures the complete imaging of the dial plate.
If the pressure gauge is in a dark environment without natural light, the image of the pressure gauge is acquired, and an active lighting source is provided.
After the condition arrangement is completed, the camera acquires the image of the pointer type pressure gauge in real time.
S1.2 pointer zero position identification of pointer type pressure gauge
As shown in fig. 1, before real-time reading identification is performed on the pointer type pressure gauge, zero-position identification of the pointer of the pressure gauge needs to be performed, and the zero-position identification process in this embodiment can be repeated for multiple times so as to obtain an average value, thereby improving the accuracy. The implementation steps comprise:
s1.2.1, processing the acquired zero position image of the pointer of the pressure gauge, and specifically comprising the following steps:
s1.2.1.1 collecting zero position image of pressure gauge pointer by industrial camera;
s1.2.1.2, carrying out distortion correction on the acquired original image according to the camera parameters obtained by calibrating the industrial camera to obtain a distortion corrected image;
s1.2.1.3, performing edge detection on the image after distortion correction to obtain an edge detection image of the zero position of the pointer of the pressure gauge;
s1.2.2 identifying and positioning the zero pressure gauge dial, the concrete steps include:
s1.2.2.1, carrying out contour extraction calculation on the obtained zero position edge detection image of the pressure gauge pointer to obtain all contours in the image;
s1.2.2.2, estimating the range of the number of pixels forming the dial plate in the edge detection image according to the actual size of the dial plate of the pressure gauge, the camera parameters obtained by calibration and the distance between the camera and the dial plate, performing preliminary screening, and extracting the contour of the dial plate according to the distribution characteristics of the internal and external gray values of the edge of the dial plate to realize the identification of the dial plate, wherein the internal white outer ring of the edge of the dial plate is black, and the gray value has obvious gradient change;
s1.2.2.3, carrying out ellipse fitting according to the extracted dial outline to obtain the position coordinates of the dial center in the image, the sizes of the major axis and the minor axis of the dial ellipse, and the inclination angle of the dial in the image;
s1.2.2.4 intercepting the image of the dial area in the zero position image of the pressure gauge pointer after distortion correction, wherein the intercepted range is that the center of the dial in the image is taken as the intercepting center, the side length is a square area which is 1.5 times of the length of the long axis of the dial fitting ellipse, the intercepted image is affine transformed according to the inclination angle of the dial in the image and the sizes of the long axis and the short axis, so that the dial inclined into the ellipse in the image is adjusted into a perfect circle dial for the subsequent pointer identification and positioning;
s1.2.3 identifying and positioning the zero pointer of the pressure gauge, the method comprises the following steps:
s1.2.3.1, carrying out binarization processing on the intercepted and affine transformed right circular dial image;
s1.2.3.2 in the binary image, the center of the dial is used as the center of a circle, the length of 0.2 times of the radius of the dial is used as the scanning radius, and the gray value and the coordinate of one circle in the image are obtained at the scanning interval of 1 degree;
s1.2.3.3 extracting the continuous interval with 0 gray value, recording the interval width and the center coordinate of the 0 value interval, and sorting according to the interval width, wherein the center coordinate of the 2 nd 0 value interval is used as the zero pointer pointing coordinate, and the coordinate and the dial center coordinate form a zero pointer vector, thereby realizing the identification and positioning of the zero pointer;
s1.2.4 identifying and positioning the characteristic mark points, and calculating the zero angle, the method comprises the following steps:
s1.2.4.1 extracting the mark point from the circular dial image after binarization processing according to the white and black dot characteristics of the mark point, performing contour extraction and ellipse fitting, and accurately locating the center coordinate of the mark point, wherein the coordinate and the dial center coordinate form a basic reference vector;
s1.2.4.2 according to the vector angle formula, the angle between the zero pointer vector and the basic reference vector can be calculated, which is the angle of the pointer zero relative to the reference mark point and can be called as the pointer zero angle, thus realizing the identification of the pointer zero.
S1.2.4.3 repeating the above steps n times, averaging to obtain the final zero angle, and using the zero angle as the reference for real-time interpretation and identification of the reading of the pointer pressure gauge.
S1.3 identification of pointer instrument readings
With reference to fig. 1, after zero-position identification of the pointer type pressure gauge is realized, real-time image acquisition is performed on the pointer type pressure gauge in work, real-time monitoring is performed, and a reading of the pressure gauge in the embodiment is identified, and the implementation steps include:
s1.3.1 the processing of pointer pressure gauge images in operation includes the following steps:
s1.3.1.1, distortion correction is carried out on the original image of the working pressure gauge acquired by the camera in real time according to the camera calibration parameters to obtain a pressure gauge image after distortion correction;
s1.3.1.2, performing edge detection on the image after distortion correction to obtain a real-time edge detection image of the working pressure gauge;
s1.3.2 identifying and locating the pointer pressure gauge in real time, comprising the following steps:
s1.3.2.1 performing contour extraction operation on the real-time edge detection image to obtain all contours in the edge detection image, performing preliminary screening according to the number of pixels forming the contours, wherein the screening range is given by the size range of pixels imaged by the camera used by the pressure gauge in the embodiment, the size range of the pixels is determined by the spatial resolution of the selected camera, and the contour extraction operation is calculated according to the camera calibration parameters and the position relationship between the camera and the pressure gauge;
s1.3.2.2, after outline preliminary screening, most interference items are removed, a pressure gauge outline needs to be extracted from the rest outline, according to the embodiment, the pressure gauge is imaged as an ellipse or a perfect circle in a camera, and the pressure gauge is characterized by black white outer frame inside, gray values on two sides of the rest outline are detected, ellipse fitting is carried out on the outline, the degree of deviation of pixel points forming the outline from the fitting ellipse is detected, the pressure gauge outline can be extracted, and the central coordinate of the pressure gauge dial in the image, the length of the long axis and the short axis of the imaging ellipse of the dial, and the rotation angle of the dial are obtained through ellipse fitting calculation;
s1.3.2.3, according to the ellipse fitting information of the dial of the pressure gauge obtained in real time, intercepting the image of the dial part from the pressure gauge image after distortion correction, wherein the intercepted range is a square area with the central coordinate of the dial in the image as the center and the side length of the square area being 1.5 times of the length of the ellipse fitting major axis of the dial;
s1.3.2.4 performing affine transformation on the captured pressure gauge dial area image according to the inclination angle and major and minor axis sizes of the dial in the image, and adjusting the dial inclined into ellipse in the image into a true circular dial for facilitating subsequent pointer identification and positioning;
s1.3.3, identifying and positioning the pointer position of the pressure gauge in work in real time, identifying the characteristic mark points, calculating the included angle between the pointer in work and the mark points, wherein the included angle has directivity, and the calculated included angle is the angle between the pointer position and the mark points by rotating around the center of the gauge anticlockwise, and the specific steps include:
s1.3.3.1, performing binarization processing on the intercepted and affine transformed right circular dial image, and projecting the pointer part effectively by reasonably setting a binarization threshold value, wherein the dial center is used as the center of a circle, the length of 0.2 times of the dial radius is used as the scanning radius, and the scanning interval of 1 degree is used for scanning counterclockwise to obtain the gray value and the coordinate of one circle in the binarization image;
s1.3.3.2 extracting continuous intervals with gray value of 0, recording interval width and center coordinate of 0 interval, sorting according to interval width, wherein the 2 nd 0 interval center coordinate is pointing coordinate of pointer, calculating according to pointer coordinate and dial center coordinate to obtain real-time pointer vector;
s1.3.3.3 although the feature mark point is fixed relative to the pressure gauge when the pressure gauge works, in order to ensure real-time performance and avoid the pressure gauge or the camera from being influenced by the outside to generate micro displacement and other changes, the feature mark point position still needs to be obtained in real time, according to the feature of the feature mark point in the embodiment, the mark point is identified and extracted, the image position coordinate of the mark point is calculated by an ellipse fitting algorithm, and then the real-time basic reference vector is calculated according to the center coordinate of the pressure gauge;
s1.3.4, real-time interpretation of readings of the pointer pressure gauge during operation, comprising the following steps:
s1.3.4.1, calculating an included angle between the real-time pointer vector and the real-time basic reference vector by using a vector point multiplication formula, and judging whether the angle between the pointer vector and the basic reference vector exceeds 180 degrees or not by using the vector direction obtained by the vector cross multiplication formula, wherein for the condition of exceeding 180 degrees, the included angle calculated by the vector point multiplication formula needs to be subtracted by 360 degrees to obtain the final angle between the pointer vector and the basic reference vector;
s1.3.4.2 subtracting the zero pointer angle from the pointer vector obtained in real time to the basic reference vector to obtain the real-time rotation angle of the pointer in the working of the pointer instrument relative to the initial position;
s1.3.4.3 in this embodiment, the division value of the pressure gauge is 0.02Mpa, and the corresponding pointer rotation angle is 9 degrees, but the initial position of the pointer is not at 0 position on the scale mark distribution rule, but has an initial angle relative to 0 position on the scale mark, so the angle needs to be calibrated by: when the pointer of the pressure gauge points to the scale marks of 0.1, 0.2 and 0.3 respectively, identifying and calculating to obtain the rotating angle of the pointer, and performing difference averaging according to the theoretical rotating angle respectively to obtain the initial angle of the zero position of the pointer relative to the 0 position of the scale marks;
s1.3.4.4 obtaining the actual rotation angle of the pointer through identification and calculation in the working process of the pressure gauge, when the angle is not 0, adding the initial angle of the pointer zero position relative to the 0 position of the graduation line to the actual rotation angle of the pointer, and then calculating to obtain the reading of the pressure gauge according to the corresponding relation between the division value of the pressure gauge and the rotation angle of the pointer;
the method for identifying the reading of the pointer instrument effectively avoids identifying more and complicated scale marks in the instrument, eliminates errors in identifying the scale marks of the instrument, greatly improves the identification precision of the reading of the pointer instrument, avoids using complex algorithms due to the fact that algorithms such as Hough transformation, least square method and the like are not used, greatly improves the operation speed, and ensures better instantaneity.
As shown in fig. 3, correspondingly, the present invention further provides a pointer instrument reading identification apparatus, including:
the image acquisition unit 301 is used for acquiring a first image of the pointer instrument when a pointer of the pointer instrument is at an initial position, wherein the first image has a characteristic mark point;
the image processing unit 302 is used for identifying and positioning the dial and a zero pointer of the first image, and determining a zero angle by using the characteristic mark points;
the image acquisition unit 301 is further configured to acquire a second image of the pointer instrument in real time, and identify and position a dial and a current pointer of the second image;
the image processing unit 302 is further configured to obtain a feature mark point in the second image, and determine a current reading of the pointer instrument by using a position relationship between a current pointer and the feature mark point.
The image capturing unit 301 may be an industrial camera, and the image processing unit 302 may be implemented by a computer or a processing chip, which is not limited thereto.
It is clear to those skilled in the art that, for convenience and brevity of description, the specific working processes of the above-described systems, apparatuses and units may refer to the corresponding processes in the foregoing method embodiments, and are not described herein again.
In the several embodiments provided in the present application, it should be understood that the disclosed system, apparatus and method may be implemented in other manners. For example, the above-described apparatus embodiments are merely illustrative, and for example, the division of the units is only one logical division, and other divisions may be realized in practice, for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or units, and may be in an electrical, mechanical or other form.
The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.
In addition, functional units in the embodiments of the present invention may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.
Those skilled in the art will appreciate that all or part of the steps in the methods of the above embodiments may be implemented by associated hardware instructed by a program, which may be stored in a computer-readable storage medium, and the storage medium may include: read Only Memory (ROM), Random Access Memory (RAM), magnetic or optical disks, and the like.
While the pointer instrument reading identification method and apparatus provided by the present invention have been described in detail, for those skilled in the art, the idea of the embodiment of the present invention may be changed in the specific implementation manner and the application scope, and in summary, the content of the present description should not be construed as limiting the present invention.
Claims (6)
1. A pointer instrument reading identification method, the method comprising:
when a pointer of the pointer instrument is at an initial position, acquiring a first image of the pointer instrument, wherein the first image has a characteristic mark point;
identifying and positioning a dial and a zero pointer for the first image, and determining a zero angle by using the characteristic mark points, wherein the method comprises the following steps:
carrying out contour extraction calculation on the edge detection image to obtain all contours in the edge detection image;
determining the range of the number of pixels forming the dial plate in the edge detection image according to the actual size of the dial plate of the pointer instrument, the camera parameters obtained by calibration and the distance between the camera and the dial plate, and extracting the contour of the dial plate according to the distribution characteristics of the internal gray value and the external gray value of the edge of the dial plate to finish the identification of the dial plate;
carrying out ellipse fitting on the extracted dial contour to obtain a position coordinate of the center of the dial in the image, the size of a long axis and a short axis of the dial ellipse and an inclination angle of the dial in the edge detection image;
intercepting an image of a dial area in a zero position image of a pointer of the pointer instrument after distortion correction, wherein the intercepted range is a square area with the center of the dial as an intercepted center and the side length being 1.5 times of the length of a major axis of a fitting ellipse of the dial, carrying out affine transformation on the intercepted image according to the inclination angle of the dial in the image and the sizes of the major axis and the minor axis, and adjusting the dial inclined into the ellipse in the image into a perfect circle dial;
carrying out binarization processing on the intercepted and affine transformed right circular dial image;
in the binary image, the center of a dial is taken as the center of a circle, the length of 0.2 times of the radius of the dial is taken as the scanning radius, and the gray value and the corresponding coordinate of one circle in the image are obtained at the scanning interval of 1 degree;
extracting a continuous interval with the gray value of 0, recording the interval width and the central coordinate of the 0-value interval, and sequencing according to the interval width, wherein the central coordinate of the 2 nd wide 0-value interval is used as a zero pointer pointing coordinate, and the coordinate and the dial central coordinate form a zero pointer vector to complete the identification and positioning of the zero pointer;
extracting the mark point from the circular dial image after binarization processing, carrying out contour extraction and ellipse fitting, positioning the circle center coordinate of the mark point, and forming a basic reference vector by the coordinate and the dial center coordinate;
calculating an included angle between two vectors by a zero pointer vector and a basic reference vector according to a vector included angle formula, wherein the included angle is an angle between the zero position of the pointer and a reference mark point, and the angle is determined as a zero position angle of the pointer to finish the identification of the zero position of the pointer;
acquiring a second image of the pointer instrument in real time, and identifying and positioning a dial plate and a current pointer of the second image; repeating the identification of the zero position of the pointer for multiple times, and carrying out average value operation on the zero position angle of the pointer as a zero position angle;
acquiring a characteristic mark point in the second image, and determining the current pointer angle of the pointer instrument by using the position relation between the current pointer and the characteristic mark point;
determining a current reading of the pointer instrument using the zero angle determined from the first image and the current pointer angle determined from the second image comprises:
and calculating to obtain the reading of the pointer instrument according to the corresponding relation between the index value of the pointer instrument and the rotation angle of the pointer by utilizing the real-time rotation angle and the initial angle of the zero position of the pointer relative to the 0 position of the scale mark.
2. The pointer instrument reading identification method of claim 1, wherein the acquiring a first image of the pointer instrument when the pointer of the pointer instrument is at the initial position, the first image having a characteristic mark point, further comprises:
a characteristic pattern is placed on the dial plate of the pointer instrument to serve as a characteristic mark point, and the area where the characteristic pattern is located is an area not swept by an instrument pointer;
the camera is aligned to the pointer instrument, so that the instrument can clearly and completely image in the camera;
the relative height of the camera and the instrument is ensured to be within the depth of field range of the camera, the instrument dial is adjusted according to the included angle between the optical axis of the camera and the perpendicular line of the center of the instrument until complete imaging is achieved, and the instrument is adjusted to be wholly within the camera view field according to the horizontal relative position of the camera and the instrument, and the dial is imaged completely;
when the pointer instrument is in a dark environment without natural light, the active illumination light source is adopted for illumination.
3. The pointer instrument reading identification method of claim 1, wherein the acquiring a first image of the pointer instrument when the pointer of the pointer instrument is at an initial position, the first image having characteristic mark points comprises:
acquiring a pointer zero position image of a pointer instrument by using a camera;
carrying out distortion correction on the acquired pointer zero position image according to camera parameters obtained by calibrating a camera to obtain a distortion corrected image;
and carrying out edge detection on the image after distortion correction to obtain an edge detection image of the zero position of the pointer type instrument.
4. The pointer instrument reading identification method of claim 1, wherein the step of acquiring a second image of the pointer instrument in real time, and identifying and positioning a dial and a current pointer of the second image comprises the steps of:
distortion correction is carried out on an original image of the pointer instrument which is acquired by a camera in real time and is in real time in the working process according to camera calibration parameters to obtain a pointer instrument image after distortion correction;
performing edge detection on the image after distortion correction to obtain a real-time edge detection image of the real-time pointer instrument in work;
performing contour extraction operation on the real-time edge detection image to obtain all contours in the edge detection image, performing primary screening according to the number of pixels forming the contours, wherein the screening range is given by the size range of pixels imaged by a pointer instrument in a camera, and the screening range is calculated according to camera calibration parameters and the position relation between the camera and the pointer instrument;
carrying out ellipse fitting on the outline, detecting the deviation degree of pixel points forming the outline from the fitting ellipse, extracting the outline of the pointer instrument, and obtaining the central coordinate of the dial plate of the pointer instrument in the image of the pointer instrument in work, the length of the long axis and the short axis of the imaging ellipse of the dial plate and the rotating angle through ellipse fitting calculation;
according to ellipse fitting information of the dial plate of the pointer instrument acquired in real time, an image of the dial plate part is intercepted from the pointer instrument image after distortion correction, and the intercepted range is a square area which takes the central coordinate of the dial plate in the image as the center and has the side length 1.5 times of the length of the long axis of ellipse fitting of the dial plate;
and performing affine transformation on the captured dial area image of the pointer instrument according to the inclination angle and the major and minor axis sizes of the dial in the captured dial area image of the pointer instrument, and adjusting the dial inclined into an ellipse in the distortion-corrected dial image of the pointer instrument into a perfect circle dial.
5. The pointer instrument reading identification method of claim 4, wherein the obtaining of the feature mark point in the second image and the determining of the current pointer angle of the pointer instrument by using the position relationship between the current pointer and the feature mark point comprises:
the method comprises the steps of identifying and positioning the pointer position of the instrument in work in real time, identifying the characteristic mark points, calculating the included angle between the pointer in work and the mark points, wherein the included angle has directivity, and the calculated included angle is the angle between the pointer position and the mark points in anticlockwise rotation around the center of the instrument.
6. The method for identifying the reading of the pointer instrument as claimed in claim 5, wherein the real-time identification and positioning of the pointer position of the instrument in operation, the identification of the characteristic mark point, the calculation of the included angle between the pointer in operation and the mark point, the included angle having directivity, the calculated included angle being the angle between the counterclockwise rotation of the pointer position around the center of the instrument and the mark point, the real-time interpretation of the reading of the pointer instrument in operation to obtain the current reading of the pointer instrument comprises:
carrying out binarization processing on the intercepted and affine transformed right circular dial plate image, effectively protruding a pointer part by reasonably setting a binarization threshold value, and scanning counterclockwise to obtain a circle of gray value and coordinates thereof in the binarization image by taking the center of the dial plate as a circle center, taking the length of 0.2 times of the radius of the dial plate as a scanning radius and taking the scanning interval of 1 degree;
extracting a continuous interval with the gray value of 0, recording the interval width and the center coordinate of the 0-value interval, sorting according to the interval width, wherein the 2 nd-wide 0-value interval center coordinate is the pointing coordinate of the pointer, and calculating according to the pointer coordinate and the dial center coordinate to obtain a real-time pointer vector;
acquiring the position of the characteristic mark point in real time, identifying and extracting the characteristic mark point, calculating the image position coordinate of the characteristic mark point by using an ellipse fitting algorithm, and calculating a real-time basic reference vector according to the central coordinate of the instrument;
calculating an included angle between a real-time pointer vector and a real-time basic reference vector by using a point multiplication formula of the vector, and judging whether the angle between the pointer vector and the basic reference vector exceeds 180 degrees or not by using a vector direction obtained by a cross multiplication formula of the vector, wherein for the condition of exceeding 180 degrees, the included angle calculated by the vector point multiplication formula needs to be subtracted by 360 degrees to obtain the angle between the final pointer vector and the basic reference vector;
and subtracting the zero position angle from the current pointer angle from the pointer vector obtained in real time to the basic reference vector to obtain the real-time rotation angle of the current pointer relative to the initial position in the working process of the pointer instrument.
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| CN110796095B (en) * | 2019-10-30 | 2022-08-09 | 浙江大华技术股份有限公司 | Instrument template establishing method, terminal equipment and computer storage medium |
| CN111091121B (en) * | 2019-11-22 | 2022-08-26 | 重庆大学 | Ellipse dial plate detection and correction method based on image processing |
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