CN115628700B - High-precision measuring rod calibration method - Google Patents
High-precision measuring rod calibration method Download PDFInfo
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- CN115628700B CN115628700B CN202211362242.6A CN202211362242A CN115628700B CN 115628700 B CN115628700 B CN 115628700B CN 202211362242 A CN202211362242 A CN 202211362242A CN 115628700 B CN115628700 B CN 115628700B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/002—Measuring arrangements characterised by the use of optical techniques for measuring two or more coordinates
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B5/00—Measuring arrangements characterised by the use of mechanical techniques
- G01B5/14—Measuring arrangements characterised by the use of mechanical techniques for measuring distance or clearance between spaced objects or spaced apertures
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Abstract
The invention discloses a high-precision measuring stick calibration method which comprises the steps of calibrating a mechanical hand tool coordinate system, a measuring workbench coordinate system and a camera coordinate system; based on the standard size of the high-precision measuring rod, establishing a measuring rod connecting library and a high-precision measuring rod model database to generate a corresponding three-dimensional model; making a priori template based on the model to perform model positioning to obtain space coordinates of the measuring rod, and determining the optimal measuring position of the measuring rod; and measuring the measuring rod, and analyzing the reference parameters to generate a calibration result. The invention is controlled by a system, eliminates subjective difference and other artificial factors, and forms a standardized and unified calibration method. The automatic feeding and discharging device realizes automatic feeding and discharging of the machine device, can achieve large-batch calibration, can greatly reduce occupation of manpower and material resources, and simultaneously meets the requirements of high efficiency and low cost.
Description
Technical Field
The invention relates to the technical field of measuring instruments, in particular to a high-precision measuring rod calibration method.
Background
With the development of society, many industries have new demands on parts thereof due to the development requirements, and quantitative descriptions of many things are needed, so that measurement is very important in technical application and scientific theory exploration. In engineering application, the measuring tool is used in many places, so that various measuring tools are provided for meeting different requirements of people in different working environments, and the high-precision measuring rod is a very common measuring tool and is a representative one. In the machining process, the measuring stick is a measuring tool which is frequently used by workers and inspectors, for example, in the production of a plurality of gear products, various single-piece or small-batch internal gear machining is frequently encountered, and generally, the measuring stick method is used by operators to measure the gear span, so that the measuring precision is high. The measuring rod has simple structure, convenient use and extremely high precision, is generally 0.001mm, and is widely used by technicians.
Because of the high precision requirement of the measuring rod, the measuring rod needs to be calibrated regularly, and the accuracy is ensured to be enough and the applicability is good. At present, a measuring rod is generally calibrated by a technician to be placed on a measuring instrument, two measuring heads are contacted with two ends of the measuring rod, the measuring heads are required to be parallel and tangential to a cylinder, and the distance between the two measuring heads is the diameter of the measuring rod. Because the accuracy requirement of the measuring rod is extremely high and the measuring rod is slightly inclined, as shown in fig. 5, the measured data cannot reflect the real situation of the measuring rod faithfully, if the measuring rod is not processed, the measuring errors are all brought into data information in the calculation process, so that the measuring rod is inaccurate to detect, and the trouble is caused to the subsequent calibration of other precise instruments by using the measuring rod. And the current measuring rod calibration is mostly manually operated, so that the efficiency is lower, and the consumed cost is higher.
Disclosure of Invention
This section is intended to outline some aspects of embodiments of the application and to briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section as well as in the description of the application and in the title of the application, which may not be used to limit the scope of the application.
Therefore, the invention solves the technical problems that: the prior art has the problems of low efficiency, high cost and error in grabbing the measuring rod by a machine device.
In order to solve the technical problems, the invention provides the following technical scheme: the invention relates to a high-precision measuring rod calibration method, which is characterized by comprising the following steps of:
calibrating a manipulator tool coordinate system, a measuring workbench coordinate system and a camera coordinate system;
Based on the standard size of the high-precision measuring rod, establishing a measuring rod connecting library and a high-precision measuring rod model database to generate a corresponding three-dimensional model;
Making a priori template based on the model to perform model positioning to obtain space coordinates of the measuring rod, and determining the optimal measuring position of the measuring rod;
and measuring the measuring rod, and analyzing the reference parameters to generate a calibration result.
The high-precision measuring rod calibration method provided by the invention is characterized by comprising the following steps of: the camera is calibrated by Zhang Zhengyou calibration method, which comprises the following steps:
The Zhang Zhengyou calibration method needs a plurality of checkerboard pictures at different relative positions with the camera to calibrate, so that the checkerboard pictures are selected and then subjected to image acquisition, the camera is continuously moved to acquire a plurality of checkerboard images at different angles, the total of 20 times is ensured that the images are in the center of the visual field of the camera as much as possible, the condition of blurring and shielding cannot occur, the paired images acquired by the binocular camera are numbered, the left-eye and right-eye images are segmented, foot point extraction is performed on the checkerboard images acquired by the left-eye and right-eye cameras, camera internal parameters are calculated, and distortion is corrected.
The high-precision measuring rod calibration method provided by the invention is characterized by comprising the following steps of: calibrating the machine device through the translation and rotation relation between the camera and the mechanical arm, comprising:
Carrying a calibration part by using a self-calibration method of a machine device to divide an image grid to obtain the grid, calculating a hand-eye relation, and assuming that a coordinate system of the machine device is (X, Y, Z, r, p, Y) and a pixel coordinate of a camera is (u, v), then for a coordinate transformation matrix T, calculating a coordinate transformation relation by the coordinate transformation relation:
In the process of using the hand-eye matrix, the coordinate transformation is performed by using the hand-eye matrix at the nearest position, and the middle transition section is overlapped by using the actual grid length so as to reduce the accumulated error. And calibrating the rotation center pixel coordinate of the tool coordinate system of the machine device relative to the image coordinate system in the hand-eye calibration process. When the pixel coordinate of the rotation center is calibrated, two calibration pictures corresponding to the tool coordinate system of the machine device are collected by the calibration block, then the gravity centers of the calibration blocks in the two pictures are obtained through the same image recognition, the rotation center under the pixel coordinate is calculated through the rotation relation between the two positions, and the position of the pixel rotation center corresponding to the coordinate system of the machine device can be obtained through utilizing the coordinate transformation matrix T.
The high-precision measuring rod calibration method provided by the invention is characterized by comprising the following steps of: and (3) establishing a measuring rod connecting library, simultaneously constructing a high-precision measuring rod model database based on the standard size of the high-precision measuring rod, generating a corresponding three-dimensional model, matching the corresponding three-dimensional model with the measuring rods of the measuring rod connecting library one by one, and giving corresponding numbers so as to facilitate the subsequent computer control system to control the machine device to quickly position and accurately grasp the measuring rods.
The high-precision measuring rod calibration method provided by the invention is characterized by comprising the following steps of: based on the digital numbering, making a priori template, acquiring the position and the whole appearance of the measuring rod by matching the images acquired and processed by the camera, and comprising the following steps:
Cutting a picture acquired by a camera into a 480 x 640 pixel graph, converting an RGB image into an HSI color space, and then performing threshold segmentation, wherein the threshold segmentation comprises gray level conversion, denoising, binarization, morphological processing and the like. And (3) performing image matching by using a priori template, identifying a target measuring rod in the acquired image, and acquiring the position and the whole appearance of the measuring rod.
The high-precision measuring rod calibration method provided by the invention is characterized by comprising the following steps of: performing edge detection on an image by using Hough straight line detection, detecting a contour of a bar, including:
A minimum circumscribed rectangle is established to contain all straight lines, and a coordinate system is established by taking the central point of the circumscribed rectangle as the origin of coordinates of the measuring rod coordinate system. And converting the coordinate system to obtain the spatial position of the measuring rod under the coordinate system of the machine device.
The high-precision measuring rod calibration method provided by the invention is characterized by comprising the following steps of: and (3) establishing a database to store measurement data by measuring the dimension parameters of the measuring bars at different angles, and selecting a minimum value as an ideal value of the measuring bars.
The high-precision measuring rod calibration system provided by the invention comprises the following components:
High-precision measuring rod conveying machine device and measuring workbench;
The machine device comprises a main body and a clamping mechanism, wherein the main body part comprises a manipulator and a first connecting plate, and the first connecting plate is used for fixing the depth camera and the clamping mechanism on the machine device;
The measuring workbench comprises a V-shaped fixing clamp and a measuring device.
The high-precision measuring rod calibration system provided by the invention is characterized in that: the V-shaped fixing clamp comprises: the device comprises a pair of V-shaped blocks, a sliding block, a guide rail, a servo motor and a screw rod; the V-shaped block on the right side is fixed on the base, the V-shaped block on the left side is fixed on the sliding block, the sliding block is fixed by a nut, a guide rail is fixed below the sliding block, and the servo motor is convenient to rotate to push the screw rod to drive the sliding block to move on the guide rail, so that clamping and positioning of the measuring rod are realized.
The high-precision measuring rod calibration system provided by the invention is characterized in that: the measuring device includes: the device comprises a base, a platform frame, a second connecting plate, an air cylinder, a side head, a rotating base and a groove; the fixture table clamping the rod to be measured is arranged on the fixture table, the angle of each rotation of the rotating base can be controlled by controlling the pulse of the servo motor, and the measuring rod is controlled to rotate at a set angle, so that the measuring rod is measured for a plurality of times, and the optimal position is adjusted and searched to obtain an ideal measurement value.
The high-precision measuring rod calibration system provided by the invention is characterized in that: the measuring device includes: the device comprises a base, a platform frame, a second connecting plate, an air cylinder, a side head, a rotating base and a groove; the fixture table clamping the rod to be measured is arranged on the fixture table, the angle of each rotation of the rotating base can be controlled by controlling the pulse of the servo motor, and the measuring rod is controlled to rotate at a set angle, so that the measuring rod is measured for a plurality of times, and the optimal position is adjusted and searched to obtain an ideal measurement value. Compared with the traditional method, the high-precision measuring rod calibration method provided by the invention has the beneficial effects that the system is controlled, subjective difference and other artificial factors are eliminated, and a standardized and unified calibration method is formed. The automatic feeding and discharging device realizes automatic feeding and discharging of the machine device, can achieve large-batch calibration, can greatly reduce occupation of manpower and material resources, and simultaneously meets the requirements of high efficiency and low cost.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the description of the embodiments will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art. Wherein:
FIG. 1 is a schematic diagram of a manipulator device for a high-precision measuring rod calibration method according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a clamping mechanism of a high-precision measuring rod calibration method according to an embodiment of the present invention;
FIG. 3 is a schematic view of positioning a V-shaped block of a high-precision measuring rod calibration method according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of a measurement platform of a high-precision measuring rod calibration method according to an embodiment of the present invention;
fig. 5 is a schematic diagram of a measuring rod inclination error of a high-precision measuring rod calibration method according to an embodiment of the present invention.
Detailed Description
So that the manner in which the above recited objects, features and advantages of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the embodiments, some of which are illustrated in the appended drawings. All other embodiments, which can be made by one of ordinary skill in the art based on the embodiments of the present invention without making any inventive effort, shall fall within the scope of the present invention.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, but the present invention may be practiced in other ways other than those described herein, and persons skilled in the art will readily appreciate that the present invention is not limited to the specific embodiments disclosed below.
Further, reference herein to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic can be included in at least one implementation of the invention. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments.
While the embodiments of the present invention have been illustrated and described in detail in the drawings, the cross-sectional view of the device structure is not to scale in the general sense for ease of illustration, and the drawings are merely exemplary and should not be construed as limiting the scope of the invention. In addition, the three-dimensional dimensions of length, width and depth should be included in actual fabrication.
Also in the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "upper, lower, inner and outer", etc. are based on the orientation or positional relationship shown in the drawings, are merely for convenience of describing the present invention and simplifying the description, and do not indicate or imply that the apparatus or elements referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the present invention. Furthermore, the terms "first, second, or third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
The terms "mounted, connected, and coupled" should be construed broadly in this disclosure unless otherwise specifically indicated and defined, such as: can be fixed connection, detachable connection or integral connection; it may also be a mechanical connection, an electrical connection, or a direct connection, or may be indirectly connected through an intermediate medium, or may be a communication between two elements. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art.
Example 1
Referring to fig. 1-4, a first embodiment of the present invention provides a method and a system for calibrating a high-precision measuring stick, including:
S1: calibrating a manipulator tool coordinate system, a measuring workbench coordinate system and a camera coordinate system;
furthermore, the camera calibration method Zhang Zhengyou comprises the following steps:
The Zhang Zhengyou calibration method needs a plurality of checkerboard pictures at different relative positions with the camera to calibrate, so that the checkerboard pictures are selected and then subjected to image acquisition, the camera is continuously moved to acquire a plurality of checkerboard images at different angles, the total of 20 times is ensured that the images are in the center of the visual field of the camera as much as possible, the condition of blurring and shielding cannot occur, the paired images acquired by the binocular camera are numbered, the left-eye and right-eye images are segmented, foot point extraction is performed on the checkerboard images acquired by the left-eye and right-eye cameras, camera internal parameters are calculated, and distortion is corrected.
Furthermore, calibrating the machine device through the translation and rotation relation between the camera and the mechanical arm comprises the following steps:
Carrying a calibration part by using a self-calibration method of a machine device to divide an image grid to obtain the grid, calculating a hand-eye relation, and assuming that a coordinate system of the machine device is (X, Y, Z, r, p, Y) and a pixel coordinate of a camera is (u, v), then for a coordinate transformation matrix T, calculating a coordinate transformation relation by the coordinate transformation relation:
In the process of using the hand-eye matrix, the coordinate transformation is performed by using the hand-eye matrix at the nearest position, and the middle transition section is overlapped by using the actual grid length so as to reduce the accumulated error. And calibrating the rotation center pixel coordinate of the tool coordinate system of the machine device relative to the image coordinate system in the hand-eye calibration process. When the pixel coordinate of the rotation center is calibrated, two calibration pictures corresponding to the tool coordinate system of the machine device are collected by the calibration block, then the gravity centers of the calibration blocks in the two pictures are obtained through the same image recognition, the rotation center under the pixel coordinate is calculated through the rotation relation between the two positions, and the position of the pixel rotation center corresponding to the coordinate system of the machine device can be obtained through utilizing the coordinate transformation matrix T.
It should be noted that, the self-calibration method of the machine device is used to carry calibration parts to divide the image grids to obtain grids, and when the hand-eye relation calculation is performed, a grid dividing calculation method is adopted to obtain a hand-eye matrix on each grid. In the actual calibration process, the X-axis direction of the base coordinate system of the machine device is considered to be the same as the X-axis direction of the pixel coordinate system of the camera, the height difference in the Z direction is ignored, and only the calculation of the two-dimensional plane relation is needed.
S2: based on the standard size of the high-precision measuring rod, establishing a measuring rod connecting library and a high-precision measuring rod model database to generate a corresponding three-dimensional model;
furthermore, a measuring rod connecting base is established, meanwhile, a high-precision measuring rod model database is established based on the standard size of the high-precision measuring rod, a corresponding three-dimensional model is generated, the corresponding three-dimensional model is matched with the measuring rods of the measuring rod connecting base one by one, and corresponding numbers are given to the measuring rods, so that a subsequent computer control system can control a machine device to quickly position and accurately grasp the measuring rods.
S3: making a priori template based on the model to perform model positioning to obtain space coordinates of the measuring rod, and determining the optimal measuring position of the measuring rod;
furthermore, a priori templates are manufactured based on digital numbers, and the positions and the whole morphology of the measuring sticks are obtained by matching images acquired and processed by a camera, comprising:
Cutting a picture acquired by a camera into a 480 x 640 pixel graph, converting an RGB image into an HSI color space, and then performing threshold segmentation, wherein the threshold segmentation comprises gray level conversion, denoising, binarization, morphological processing and the like. And (3) performing image matching by using a priori template, identifying a target measuring rod in the acquired image, and acquiring the position and the whole appearance of the measuring rod.
Furthermore, the detecting the contour of the output bar by detecting the edges of the image through Hough straight line detection comprises:
A minimum circumscribed rectangle is established to contain all straight lines, and a coordinate system is established by taking the central point of the circumscribed rectangle as the origin of coordinates of the measuring rod coordinate system. And converting the coordinate system to obtain the spatial position of the measuring rod under the coordinate system of the machine device.
S4: and measuring the measuring rod, and analyzing the reference parameters to generate a calibration result.
Furthermore, a database is established to store the measurement data by measuring the dimension parameters of the measuring bars at different angles, and the minimum value is selected as the ideal value of the measuring bars.
In an alternative embodiment, a high-precision stick calibration system for use in a high-precision stick calibration method, comprising:
A high precision stick transporting machine device 100 and a measuring table 200;
The machine device 100 comprises a main body 101 and a clamping mechanism 102, wherein the main body 101 comprises a manipulator 103 and a first connecting plate 104, and the first connecting plate 104 is used for fixing a depth camera 105 and the clamping mechanism 102 on the machine device 100;
the measuring table 200 includes a V-shaped fixing jig 201 and a measuring device 202.
The V-shaped fixing jig 201 includes: a pair of V-shaped blocks 201a, a slider 201b, a guide rail 201c, a servo motor 201d, and a screw 201e; the right V-shaped block is fixed on the base, the left V-shaped block is fixed on the sliding block 201b, the sliding block 201b is fixed by a nut, the guide rail 201c is fixed below the sliding block, the servo motor 201d is convenient to rotate and push the screw rod 201e to drive the sliding block 201b to move on the guide rail 201c, and clamping and positioning of the measuring rod are achieved.
The measuring device includes: base 202a, platform frame 202b, second connection plate 202c, cylinder 202d, side head 202e, swivel base 202f and groove 202g; the fixture table clamping the rod to be measured is arranged on the fixture table, the angle of each rotation of the rotating base can be controlled by controlling the pulse of the servo motor, and the measuring rod is controlled to rotate at a set angle, so that the measuring rod is measured for a plurality of times, and the optimal position is adjusted and searched to obtain an ideal measurement value.
Example 2
Referring to fig. 1-5, for an example of the present invention, a high precision stick calibration method is provided, and in order to verify the beneficial effects of the present invention, a scientific demonstration is performed by a specific embodiment.
Step one: the position of the machine device 100 relative to the measuring table 200 is arranged reasonably to ensure that there is no interference between the machine device 100 and the gauge.
Step two: calibrating the measuring instrument, the camera, the mechanical hand tool coordinate system and the measuring workbench coordinate system, ensuring the mechanical hand measuring workbench to work stably and reliably, and acquiring real and effective data by the camera.
It should be noted that the depth camera is composed of a photosensitive element, a lens module and a plurality of sensors, obtains the physical distance between an object in a scene and the camera, further obtains depth information, and performs three-dimensional reconstruction on a target to achieve target positioning.
And the software program matched with the measuring instrument is utilized, the software is communicated with the control system, the parameter setting and other operations are realized, and meanwhile, the special software is used for debugging and detecting the measuring system, so that the measuring precision can meet the requirements. Meanwhile, a Zhang Zhengyou calibration method is used for calibrating the camera, a Zhang Zhengyou calibration method is used for calibrating a plurality of checkerboard pictures at different relative positions with the camera, so that the checkerboard pictures are selected and then subjected to image acquisition, the camera is continuously moved to acquire a plurality of checkerboard pictures at different angles, the total of 20 times is achieved, the pictures are ensured to be in the center of the visual field of the camera as far as possible, the condition of blurring and shielding can not occur, the paired pictures acquired by the binocular camera are numbered, the left-eye and right-eye images are segmented, foot point extraction is performed on the checkerboard pictures acquired by the left-eye and right-eye cameras, camera internal parameters are calculated, and distortion is corrected.
After calibration, the camera can accurately represent a certain position in the space in a camera coordinate system, but the position is only displayed under the camera coordinate system, and in order to further convert the position relationship into a coordinate point under the coordinate system of the tail end of the mechanical arm, a translation and rotation relationship is required to be established between the camera and the mechanical arm, namely, after the camera accurately acquires the object coordinates, a coordinate conversion relationship is required to be established between the camera and the grabbing tool of the tail end of the mechanical arm, and the mechanical arm can accurately acquire positioning grabbing point information for grabbing. The self-calibration method of the machine device is used for carrying the calibration part blocks to carry out grid division of the image, so that the thought deviation caused by manual calibration can be greatly reduced. The self-calibration method of the machine device is used for carrying calibration parts to divide image grids to obtain grids, and when the hand-eye relation calculation is carried out, a grid dividing calculation method is adopted to obtain a hand-eye matrix on each grid. In the actual calibration process, the X-axis direction of the base coordinate system of the machine device is considered to be the same as the X-axis direction of the pixel coordinate system of the camera, the height difference in the Z direction is ignored, and only the calculation of the two-dimensional plane relation is needed. Assuming that the machine coordinate system is (X, Y, Z, r, p, Y) and the pixel coordinates of the camera are (u, v), then for the coordinate transformation matrix T, the coordinate transformation relationship:
In the process of using the hand-eye matrix, the coordinate transformation is performed by using the hand-eye matrix at the nearest position, and the middle transition section is overlapped by using the actual grid length so as to reduce the accumulated error. And calibrating the rotation center pixel coordinate of the tool coordinate system of the machine device relative to the image coordinate system in the hand-eye calibration process. When the pixel coordinate of the rotation center is calibrated, two calibration pictures corresponding to the tool coordinate system of the machine device are collected by the calibration block, then the gravity centers of the calibration blocks in the two pictures are obtained through the same image recognition, the rotation center under the pixel coordinate is calculated through the rotation relation between the two positions, and the position of the pixel rotation center corresponding to the coordinate system of the machine device can be obtained through utilizing the coordinate transformation matrix T.
Step three: and (3) establishing a measuring rod connecting library, simultaneously constructing a high-precision measuring rod model database based on the standard size of the high-precision measuring rod, generating a corresponding three-dimensional model, matching the corresponding three-dimensional model with the measuring rods of the measuring rod connecting library one by one, and giving corresponding numbers so as to facilitate the subsequent computer control system to control the machine device to quickly position and accurately grasp the measuring rods.
Step four: and selecting a high-precision V-shaped block with proper specification, and fixedly mounting the high-precision V-shaped block on a rotary detection platform, wherein the mounting precision of the high-precision V-shaped block is ensured. As shown in FIG. 3, a long V-shaped block with an included angle of 90 DEG between two inclined planes is selected for fixing the rod to be measured, limiting four degrees of freedom, ensuring the verticality of the axis of the rod and the measuring reference plane, and simultaneously facilitating the stability of the rod when the rod is measured.
It should be noted that typical V-block sizes and configurations are standardized, with the included angles α of the two bevels generally being 60 °,90 ° and 120 °. The material is typically HT200-250 or alloy tool steel, etc., and the maximum value of the surface roughness should not be more than 0.63.
As shown in fig. 5, when calibrating the measuring stick, the measuring stick is placed on the turntable of the instrument, and due to the offset and inclination problems of the mounting of the measuring stick, the axis of the measuring stick cannot coincide with the coordinate axis, and even if the measuring stick is carefully adjusted, an inclination error remains. Therefore, the measured rod deviates from the ideal position, so that the data acquired by the measuring head of the measuring instrument deviates, the ideal circle is changed into an ellipse, the ideal situation is (a), and the error situation is (b). According to the graph, after the measuring rod is inclined, the measured data cannot reflect the actual situation of the measuring rod, and if certain processing is not carried out on the inclination, all measurement errors are brought into data information in the calculation process, so that the calibration result is inaccurate.
Step five: and (3) manufacturing a priori template by using the number coded in the step three. Cutting a picture acquired by a camera into a 480 x 640 pixel graph, converting an RGB image into an HSI color space, and then performing threshold segmentation, wherein the threshold segmentation comprises gray level conversion, denoising, binarization, morphological processing and the like. And (3) performing image matching by using a priori template, identifying a target measuring rod in the acquired image, and acquiring the position and the whole appearance of the measuring rod. And (3) performing edge detection on the image, detecting straight lines (namely, measuring bar outlines) by using Hough straight line detection, establishing a minimum circumscribed rectangle to contain all the straight lines, and establishing a coordinate system by taking the central point of the circumscribed rectangle as the origin of coordinates of the measuring bar coordinate system. And converting the coordinate system to obtain the spatial position of the measuring rod under the coordinate system of the machine device.
Step six: and C, controlling the machine device to grasp the target measuring rod according to the information obtained in the step five, and stably placing the target measuring rod on the V-shaped block clamp fixed in the step four, wherein a space convenient for measurement is reserved. Meanwhile, whether the manipulator completely exits from the measurement area needs to be judged so as to prevent the manipulator from interfering with the measurement process, so that the calibration result is wrong or hidden danger in safety is brought. And then driving a servo motor to tighten the measuring rod, so as to ensure that the axis of the measuring rod is vertical to the measuring surface.
Step seven: after the manipulator is detected to completely exit the measuring area, the measuring is started, and the measuring head of the measuring instrument reads the dimension parameters of the measuring rod. After the measurement of the size of the measuring rod is finished, the cylinder is controlled to loosen the measuring head, the rotating platform is controlled by the servo motor to rotate a preset angle, then the measuring head is measured again, the measuring head reciprocates, repeated measurement is carried out for a plurality of times by one measuring rod, a database is established to store measurement data, and the minimum value is selected as an ideal value of the measuring rod.
Step eight: and (3) automatically blanking by a machine device, taking off the calibrated measuring rod from the measuring table, and transporting the measuring rod back to the original position. And repeating the steps of five, six and seven to realize the mass calibration of the measuring bars, and returning the machine device to the original position after the whole calibration of the measuring bars is finished.
It should be noted that the embodiments described herein are for the purpose of aiding the reader in understanding the practice of the invention, and it should be understood that the scope of the invention is not limited to such specific statements and embodiments. Those of ordinary skill in the art can make various other specific modifications and combinations from the teachings of the present disclosure without departing from the spirit thereof, and such modifications and combinations remain within the scope of the present disclosure.
Claims (1)
1. The high-precision measuring rod calibration method is characterized by comprising the following steps of:
calibrating a manipulator tool coordinate system, a measuring workbench coordinate system and a camera coordinate system;
Based on the standard size of the high-precision measuring rod, establishing a measuring rod connecting library and a high-precision measuring rod model database to generate a corresponding three-dimensional model;
Making a priori template based on the model to perform model positioning to obtain space coordinates of the measuring rod, and determining the optimal measuring position of the measuring rod;
measuring the measuring rod, and analyzing the standard parameters to generate a calibration result;
Calibrating the camera by using Zhang Zhengyou calibration method;
The Zhang Zhengyou calibration method uses a plurality of checkerboard pictures at different relative positions with the camera to calibrate, so that the checkerboard pictures are selected and then are subjected to image acquisition, and the camera continuously moves to acquire a plurality of checkerboard pictures with different angles for 20 times;
Numbering paired images acquired by the binocular cameras, dividing left-eye and right-eye images, extracting foot points of checkerboard images acquired by the left-eye and right-eye cameras, calculating camera internal parameters, and correcting distortion;
Calibrating the machine device through the translation and rotation relation between the camera and the mechanical arm;
Carrying a calibration part by using a self-calibration method of a machine device to divide an image grid to obtain the grid, calculating a hand-eye relation, and assuming that a coordinate system of the machine device is (X, Y, Z, r, p, Y) and a pixel coordinate of a camera is (u, v), then for a coordinate transformation matrix T, calculating a coordinate transformation relation by the coordinate transformation relation:
in the process of applying the hand-eye matrix, the coordinate transformation is carried out by using the hand-eye matrix at the nearest position, and the middle transition section is overlapped by using the actual grid length so as to reduce the accumulated error;
In the process of calibrating the hand and eye, calibrating the pixel coordinate of the rotation center of the machine tool coordinate system relative to the image coordinate system, when calibrating the pixel coordinate of the rotation center, acquiring two calibration pictures of a calibration block rotated by 180 degrees corresponding to the machine tool coordinate system, then identifying the two pictures with the images to obtain the gravity centers of the calibration blocks in the two pictures, calculating the rotation center under the pixel coordinate according to the rotation relation between the two positions, and obtaining the position of the pixel rotation center corresponding to the machine coordinate system by utilizing the coordinate transformation matrix T;
Carrying a calibration part by using a self-calibration method of a machine device to divide an image grid to obtain grids, and obtaining a hand-eye matrix on each grid by adopting a grid dividing calculation method when carrying out hand-eye relation calculation;
The X-axis direction of the base coordinate system of the machine device is the same as the X-axis direction of the pixel coordinate system of the camera, the height difference in the Z direction is not calculated, and only the two-dimensional plane relation is calculated;
Establishing a measuring rod connecting library, simultaneously constructing a high-precision measuring rod model database based on the standard size of the high-precision measuring rod, generating a corresponding three-dimensional model, matching the corresponding three-dimensional model with the measuring rods of the measuring rod connecting library one by one, and giving corresponding numbers;
making a priori template based on the number, and acquiring the position and the whole shape of the measuring rod by matching the images acquired and processed by the camera;
Cutting a picture acquired by a camera into a 480 x 640 pixel graph, converting an RGB image into an HSI color space, and then carrying out threshold segmentation, including gray level conversion, denoising, binarization and morphological processing, carrying out image matching by using a priori template, identifying a target measuring stick in the acquired image, and acquiring the position and the overall shape of the measuring stick;
Based on hough straight line detection, detect the measuring stick profile, include:
establishing a minimum circumscribed rectangle to contain all straight lines, establishing a coordinate system by taking a central point of the circumscribed rectangle as a coordinate origin of a measuring rod coordinate system, and performing coordinate system conversion to obtain a spatial position of the measuring rod under the coordinate system of a machine device;
establishing a database to store measurement data by measuring the dimension parameters of the measuring bars at different angles, and selecting a minimum value as an ideal value of the measuring bars;
Further comprises:
A high-precision rod-handling machine device (100) and a measuring table (200);
the machine device (100) comprises a main body (101) and a clamping mechanism (102), wherein the main body (101) comprises a manipulator (103) and a first connecting plate (104), and the first connecting plate (104) is used for fixing a depth camera (105) and the clamping mechanism (102) on the machine device (100);
The measuring workbench (200) comprises a V-shaped fixed clamp (201) and a measuring device (202);
the V-shaped fixing clamp (201) comprises: a pair of V-shaped blocks (201 a), a sliding block (201 b), a guide rail (201 c), a servo motor (201 d) and a screw (201 e); the right V-shaped block is fixed on the base, the left V-shaped block is fixed on the sliding block (201 b), the sliding block (201 b) is fixed by a nut, a guide rail (201 c) is fixed below the sliding block, and a servo motor (201 d) is convenient to rotate to push a screw rod (201 e) to drive the sliding block (201 b) to move on the guide rail (201 c), so that clamping and positioning of a measuring rod are realized;
The measuring device includes: a base (202 a), a platform frame (202 b), a second connecting plate (202 c), a cylinder (202 d), a side head (202 e), a rotating base (202 f) and a groove (202 g); the fixture table clamping the rod to be measured is arranged on the fixture table, the angle of each rotation of the rotating base is controlled by controlling the pulse of the servo motor, and the measuring rod is controlled to rotate at a set angle, so that the measuring rod is measured for a plurality of times, and the optimal position is adjusted and searched to obtain an ideal measurement value.
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