CN109781002B - Machine vision-based machine tool full-axis-stroke accurate positioning method - Google Patents
Machine vision-based machine tool full-axis-stroke accurate positioning method Download PDFInfo
- Publication number
- CN109781002B CN109781002B CN201910099349.8A CN201910099349A CN109781002B CN 109781002 B CN109781002 B CN 109781002B CN 201910099349 A CN201910099349 A CN 201910099349A CN 109781002 B CN109781002 B CN 109781002B
- Authority
- CN
- China
- Prior art keywords
- calibration
- intersection position
- industrial camera
- processor
- machine tool
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Images
Landscapes
- Length Measuring Devices By Optical Means (AREA)
- Machine Tool Sensing Apparatuses (AREA)
Abstract
The invention provides a machine vision-based machine tool full-axis stroke accurate positioning method, and relates to the technical field of control and adjustment. The intersection position X of the optical axis of the industrial camera and the calibration plate is calibrated to be P by using a laser interferometer and stored in the processor, the industrial camera shoots images of the intersection position X and the adjacent calibration holes M and transmits the images to the processor, and the processor calculates and stores the image coordinates of the adjacent calibration holes M through the calibration value P; the working table moves, the industrial camera shoots, the image information of the intersection position T of the optical axis of the industrial camera after the movement of the calibration plate and the adjacent calibration holes N of the intersection position T are transmitted to the processor, and the processor calculates the coordinate of the intersection position T after the movement through the stored image coordinates of the adjacent calibration holes M. The invention solves the problem that the prior art can not realize accurate positioning of a numerical control machine tool during large full-axis stroke work. The invention has the beneficial effects that: the accurate positioning of the full-axis stroke of the machine tool is realized, and the positioning accuracy can reach micron level. The use cost is low only by once calibration of the laser interferometer.
Description
Technical Field
The invention relates to the technical field of control and adjustment, in particular to a method for positioning full-axis distance precision of a numerical control machine tool in use.
Background
The numerical control machine tool is a machining device based on numerical control, and the working platform repeatedly moves on the guide rail to work according to digital program instructions. The precision requirement of the numerical control machine tool during working is very high and usually reaches the micron level. Due to long-term use, system errors, particularly numerical control system and mechanical transmission errors, caused by the long-term use can affect the precision of a machined part. The current solution is to calibrate the numerical control machine at regular times. The calibration method mainly comprises active calibration and passive calibration. Passive calibration means that a product to be processed is put on an instrument such as a three-coordinate measuring machine, and when a large error is detected, a processing part has a problem. The method has hysteresis, and when problems are found, some parts are scrapped and need to be machined again, so that waste is caused. The active calibration means that a double-frequency laser interferometer is used, the laser interferometry principle is utilized, the real-time wavelength of laser is used as the measurement reference, and errors are determined through laser reflection. The method has high calibration cost, and the dual-frequency laser interferometer cannot be arranged on a machine tool all the time for use. With the rapid development of computer systems and image processing technologies, machine vision-based image measurement technologies are now widely used in various fields of industrial manufacturing. The invention discloses an invention application document named as a method for detecting and positioning a diamond tool in place, which is published in China patent application No. CN104669065A on 2015, 6 and 3, and discloses a technical scheme of the method. The method comprises the following steps: a) fixedly mounting an imaging system on a machine tool main shaft, wherein the relative position of the machine tool main shaft and a machine tool X motion shaft is fixed; b) positioning the diamond cutter in the height direction by using the depth of field of the imaging system; c) after the positioning in the height direction is finished, adjusting the brightness of a light source and the horizontal position of the diamond cutter to obtain a clear and complete cutter image; d) according to different types of the cutters, different geometric parameters of the cutters are respectively measured by using the optical images; e) acquiring the coordinates of the cutter positioning reference point in an optical image coordinate system; f) and the coordinates of the cutter positioning reference point are converted into coordinates in a machine tool coordinate system, so that the diamond cutter is positioned in the horizontal plane of the machine tool. Generally, the higher the image measurement accuracy, the smaller the working field of view. The method has small cutter variation range, and the function of accurate positioning during large full-axis working is difficult to realize by the positioning method for machining the key target of the cutter.
Disclosure of Invention
In order to solve the technical problem that accurate positioning of a numerical control machine tool during large full-axis stroke work cannot be achieved in the prior art, the invention provides a machine vision-based machine tool full-axis stroke accurate positioning method, which achieves accurate measurement and positioning of the numerical control machine tool large full-axis stroke, enables the positioning accuracy to reach the micron level and meets the actual industrial manufacturing requirements.
The technical scheme of the invention is as follows: a machine tool full-axis-range accurate positioning method based on machine vision comprises a guide rail, a workbench movably connected with the guide rail, a laser interferometer and a processor, wherein a calibration plate is connected to the upper surface of the workbench, a plurality of industrial cameras are fixedly connected above the calibration plate, the calibration plate is provided with a plurality of calibration holes, the intersection position X of an optical axis W of the industrial camera and the calibration plate is calibrated by the laser interferometer, a calibration value is P and is stored in the processor, the industrial camera W shoots images of the intersection position X and adjacent calibration holes M of the intersection position X and transmits the images to the processor, and the processor calculates the image coordinates of the adjacent calibration holes M through the calibration value P and stores the image coordinates in the processor; the working table moves on the guide rail, the industrial camera W shoots the calibration plate, the image information of the intersection position T of the optical axis of the industrial camera W after the movement of the calibration plate and the adjacent calibration hole N of the intersection position T after the movement is transmitted to the processor, and the processor calculates the coordinate of the intersection position T after the movement through the stored image coordinates of the adjacent calibration hole M. The laser interferometer is calibrated only once, and then the positioning is completed by matching the industrial camera with the calibration plate, so that the operation is convenient, and the use cost is low.
Preferably, the calibration holes are round holes which are arranged in rows, the precision error of the spacing position is less than or equal to 1 mu m, and the central axis connecting line of the calibration holes is parallel to the central axis of the guide rail; the positioning precision is high.
Preferably, the optical axis of the industrial camera is parallel to the central axis of the calibration hole.
Preferably, the processor determines the pixel difference between the shifted intersection position T and the adjacent calibration hole N and then calculates the relative distance.
Preferably, the industrial camera is provided with a telecentric lens, and the distance from the tail end of the telecentric lens to the calibration plate is equal to the object distance of the telecentric lens; the influence caused by the angular deviation is eliminated, and the pixel detection precision is improved.
Preferably, the workbench is connected with a side camera, and the visual field of the side camera is all calibration holes on the calibration plate and telecentric lenses of all industrial cameras; the industrial camera and the corresponding calibration hole are convenient to confirm.
Compared with the prior art, the invention has the beneficial effects that: the accurate positioning of the full-axis stroke of the machine tool is realized, the positioning accuracy can reach the micron level, and the actual industrial manufacturing requirements are met. The laser interferometer calibration is only needed once, the operation is convenient, the use cost is low, and the real-time calibration capability in the processing process can be realized.
Drawings
FIG. 1 is a flow chart of the present invention;
FIG. 2 is a schematic connection diagram of the present invention;
FIG. 3 is a top view of FIG. 2;
FIG. 4 is a schematic diagram illustrating calibration of an industrial camera and corresponding calibration holes;
FIG. 5 is a schematic diagram illustrating calibration calculation of an industrial camera and a corresponding calibration hole;
FIG. 6 is a schematic view of the positioning by an industrial camera and corresponding calibration holes.
In the figure: 1-a guide rail; 2-a workbench; 3-a lateral camera; 4-calibrating the plate; 5-a bracket; 6-a light source; 7-an industrial camera; 21-side arm.
Detailed Description
The technical scheme of the invention is further specifically described by the following embodiments and the accompanying drawings.
Example 1:
as shown in fig. 1-6, a machine tool full-axis precise positioning method based on machine vision includes a guide rail 1, a workbench 2 movably connected with the guide rail 1, a laser interferometer, and a processor. The guide rail 1 and the workbench 2 are owned by the machine tool. The length extension direction of the guide rail 1 is consistent with the length extension direction of a machine tool shaft. The full-axis positioning means meets the positioning requirement in the maximum working distance of the machine tool guide rail. The laser interferometer is a dual-frequency laser interferometer.
The upper surface of the working table 2 is connected with a calibration plate 4. The calibration plate 4 is a strip plate. In order to prevent the precision error caused by thermal deformation, the calibration plate 4 is of a non-metal structure such as ceramic. The calibration plate 4 is provided with a plurality of calibration holes. The calibration hole is a round hole. The calibration holes are circular patterns or circular pits which are laser-printed on the upper surface of the calibration plate 4. The calibrated holes are arranged in rows. One calibration plate 4 is provided with a plurality of parallel rows of calibration holes. The diameters of the calibration holes on the same calibration plate 4 are equal. The precision error of the distance between the calibration holes in the same row is less than or equal to 1 mu m. The central axis line of the calibration hole is parallel to the central axis of the guide rail 1.
A plurality of industrial cameras 7 are fixedly connected above the calibration plate 4. Above the calibration plate 4, the machine tool is provided with a bracket 5. The holder 5 is strip-shaped. The length extension direction of the bracket 5 is consistent with the length extension direction of the guide rail 1. The lower surface of the bracket 5 is connected with a light source 6. The light source 6 is in a strip shape and is provided with a brightness adjusting control switch. The bracket 5 is connected to an industrial camera 7. The industrial cameras 7 are arranged in a row along the length extension direction of the bracket 5. The distance between the industrial cameras 7 can be different, but the distance cannot be larger than the length of the calibration plate 4, so that at least one industrial camera 7 can observe more than one calibration hole on the calibration plate 4 when the movable workbench 2 is at any position of the effective axial distance. The industrial camera 7 is provided with a telecentric lens. The distance from the end of the telecentric lens to the calibration plate 4 is equal to the object distance of the telecentric lens. That is, it is ensured that the image captured by the industrial camera 7 does not change in magnification and is free from distortion. The optical axis of the industrial camera 7 is parallel to the central axis of the calibration hole. The industrial camera 7 is marked with a sign, the industrial camera 7 as shown in fig. 4-6 is marked with W.
A side camera 3 is connected to the table 2. A projecting side arm 21 is attached to one side of the table 2. The side camera 3 is fixed to the upper surface of the side arm 21. The lens of the side camera 3 faces the calibration plate 4. The field of view of the side camera 3 is all the calibration holes on the calibration plate 4 and the telecentric lens of the industrial camera 7 above the calibration plate 4.
Initially, the calibration holes of the calibration plate 4 are calibrated. The laser interferometer is placed at one end of the guide rail 1. The laser interferometer value is zeroed. The working table 2 is moved to a certain position and stopped. The side camera 3 photographs the industrial camera of the mark W and the calibration hole of the calibration plate 4. The optical axis of the industrial camera marked W intersects the calibration plate 4 at the position X. Let the calibration hole adjacent to the left side of the intersection position X be the calibration hole M, and the calibration hole adjacent to the right side be the calibration hole M +1 (as shown in fig. 4). The intersection position X is calibrated by a laser interferometer. The calibration operation mode conforms to the GB/T17421.1-1998 part 1 of the machine tool inspection general rule: geometric accuracy of the machine tool under no load or finish machining conditions ". The laser interferometer reads the calibration value P and stores the value in the processor. And the calibration value P is the distance from the intersection position X to the zero setting of the laser interferometer relative to the guide rail.
The industrial camera 7 shoots images of the intersection position X and the adjacent calibration holes M of the intersection position X and transmits the images to the processor. The industrial camera shot image of the marker W is shown in the dashed box of 4. Setting the distance from zero of the guide rail to the center point of the circle M of the calibration hole as LMX is a distance L from the intersection positionX. Conversion to actual distance difference Q(X-M)＝(LX-LM) R, R represents the actual distance represented by 1 pixel, in mm/pixel.
And the processor calculates the image coordinates of the adjacent calibration holes M through the calibration value P and stores the image coordinates in the processor. Firstly, a calibration reference value S is calculatedM。SMRepresenting the value that the laser interferometer should display when the calibration hole M is at the intersection position X. This reference value does not require a motion measurement, since the current coordinate estimate corresponds to P' ═ SM+Q(X-M)+ d, where P' is read directly from the laser interferometer. d represents a systematic error. Due to temperature and humidity changes, vibration, quantization and other factors, d is a fixed value under the condition that the worktable 2 does not move continuously. Therefore, d should be as little as possible to participate in the calculation to reduce the error, and the system calculated value P' should be equal to the laser interferometer indicated value P. Therefore, S is used in the calculationMSet to zero to obtain a system calculated value P0＝Q(X-M)+ d. Then, P-P0I.e. calibrating the system reference value S of the hole MMIn mm. As shown in fig. 5, a dotted box in the figure indicates an industrial camera shot image of the mark W.
And repeating the operation, calibrating all the industrial cameras 7 and the calibration plate 4 in the full-axis range of the guide rail 1, and realizing that each industrial camera 7 obtains a reference value corresponding to any calibration hole on the calibration plate 4. The data is stored in the processor. The laser interferometer is removed.
In use, the table 2 is moved to any position on the guide rail 1, and the side camera 3 takes an image as shown in fig. 6, and the industrial camera taking an image of the mark W is shown in the broken line box of 6. The industrial camera in operation is observed to be the one marked W among the side cameras 3, the reference value S being previously set in correspondence with the calibrated holes MMThe crossing position of the industrial camera marked with W and the calibration plate 4 is T, and the adjacent calibration hole N of T and the industrial camera marked with W are not set with reference values. Image information captured by the industrial camera of the marker W is transmitted to the processor. The processor first determines the pixel difference between the shifted intersection location T and the adjacent calibration hole N. The industrial camera labeled W is working. The coordinates P of the intersection position T can be estimatedT。PT＝SM+DM+Q(T-N)R. Wherein DMRepresents the distance between the calibration hole N and the calibration hole M found by the side camera 3 and conforms to DM＝(N-M)*Ds，DsAnd the fixed distance between the centers of the two calibration holes is expressed in mm. Q(T-N)And the pixel distance of the circle center of the calibration hole N and the intersection position T, which is found when the coordinate of the intersection position T is expressed, is unit pixel. Wherein (N-M) represents the difference in numbering between the two calibration wells, DsThe fixed distance between the centers of two adjacent calibration holes is shown. R represents the actual distance represented by 1 pixel in the image, in mm/pixel. And calculating the relative distance according to the coordinates of the moved intersecting position T through the stored image coordinates of the adjacent calibration holes M.
Claims (5)
1. The full-axis precise positioning method of the machine tool based on machine vision comprises a guide rail (1), a workbench (2) movably connected with the guide rail (1), a laser interferometer and a processor, and is characterized in that: the upper surface of the workbench (2) is connected with a calibration plate (4), a plurality of industrial cameras (7) are fixedly connected above the calibration plate (4), and the calibration plate (4) is provided with a plurality of calibration holes; the workbench (2) is connected with a lateral camera (3), and the visual field of the lateral camera (3) is all calibration holes on the calibration plate (4) and telecentric lenses of all industrial cameras (7); the intersection position of the optical axis of the industrial camera (7) and the calibration plate (4) is calibrated by a laser interferometer and stored in a processor; the industrial camera W shoots images of the intersection position X and the adjacent calibration holes M of the intersection position X and transmits the images to the processor, and the processor calculates the image coordinates of the adjacent calibration holes M through the calibration value P and stores the image coordinates in the processor; the workbench (2) moves on the guide rail (1), the industrial camera W shoots an intersection position T of an optical axis of the industrial camera W and the calibration plate (4) and an adjacent calibration hole N of the intersection position T after the industrial camera W moves, and image information is transmitted to the processor; and determining the pixel difference between the moved intersection position T and the adjacent calibration hole N through the image, observing the working industrial camera W by the lateral camera (3), determining the distance between the calibration hole N and the calibration hole M through the lateral camera (3), and finally calculating the coordinate of the moved intersection position T.
2. The machine vision-based full-axis precise positioning method for the machine tool is characterized by comprising the following steps of: the calibration holes are round holes and are arranged in rows, the precision error of the spacing position is less than or equal to 1 mu m, and the central axis line of the calibration holes is parallel to the central axis of the guide rail (1).
3. The full-axis precise positioning method of the machine tool based on the machine vision is characterized in that according to the claim 1 or 2: the optical axis of the industrial camera (7) is parallel to the central axis of the calibration hole.
4. The machine vision-based full-axis precise positioning method for the machine tool is characterized by comprising the following steps of: the processor firstly determines the pixel difference between the moved intersection position T and the adjacent calibration hole N, and then calculates the relative distance.
5. The machine vision-based full-axis precise positioning method for the machine tool is characterized by comprising the following steps of: the industrial camera (7) is provided with a telecentric lens, and the distance from the tail end of the telecentric lens to the calibration plate (4) is equal to the object distance of the telecentric lens.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201910099349.8A CN109781002B (en) | 2019-01-31 | 2019-01-31 | Machine vision-based machine tool full-axis-stroke accurate positioning method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201910099349.8A CN109781002B (en) | 2019-01-31 | 2019-01-31 | Machine vision-based machine tool full-axis-stroke accurate positioning method |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN109781002A CN109781002A (en) | 2019-05-21 |
| CN109781002B true CN109781002B (en) | 2020-11-17 |
Family
ID=66504017
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201910099349.8A Active CN109781002B (en) | 2019-01-31 | 2019-01-31 | Machine vision-based machine tool full-axis-stroke accurate positioning method |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN109781002B (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111174696B (en) * | 2019-11-30 | 2022-04-15 | 河北科技大学 | Laser-assisted calibration method based on CCD sensor |
| CN112150539B (en) * | 2020-08-17 | 2022-10-18 | 浙江省计量科学研究院 | Chain pitch detection device and method based on double cameras |
| CN113059404B (en) * | 2021-04-19 | 2023-04-25 | 曹智军 | Visual workpiece positioning method of numerical control milling machine |
| CN114252012B (en) * | 2021-12-22 | 2024-01-16 | 上海原能细胞生物低温设备有限公司 | Method for acquiring hole site of cryopreservation box |
| CN114346759B (en) * | 2022-03-10 | 2022-07-15 | 成都飞机工业（集团）有限责任公司 | Device for hole online detection and hole finish machining and machining method thereof |
Family Cites Families (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE19755608B4 (en) * | 1997-12-15 | 2012-12-06 | Volkswagen Ag | Use of a device and method for calibrating a scale |
| US7800758B1 (en) * | 1999-07-23 | 2010-09-21 | Faro Laser Trackers, Llc | Laser-based coordinate measuring device and laser-based method for measuring coordinates |
| CN102706274B (en) * | 2012-04-25 | 2014-08-06 | 复旦大学 | System for accurately positioning mechanical part by machine vision in industrially-structured scene |
| CN103247053B (en) * | 2013-05-16 | 2015-10-14 | 大连理工大学 | Based on the part accurate positioning method of binocular microscopy stereo vision |
| CN104669065B (en) * | 2015-01-28 | 2017-02-22 | 中国工程物理研究院激光聚变研究中心 | Diamond tool in-situ detection and positioning method |
| CN104677301B (en) * | 2015-03-05 | 2017-03-01 | 山东大学 | A kind of spiral welded pipe pipeline external diameter measuring device of view-based access control model detection and method |
| DE102016116702B4 (en) * | 2015-09-14 | 2019-01-24 | Fanuc Corporation | Measuring system for calibrating the mechanical parameters of a robot |
| CN207163401U (en) * | 2017-05-31 | 2018-03-30 | 天津大学 | Moving component multi-parameter detecting system based on combinatorial surface type standard |
| CN107705335A (en) * | 2017-09-21 | 2018-02-16 | 珠海中视科技有限公司 | Demarcate the non-method that ken line sweeps laser range finder and measures camera orientation altogether |
| CN109163658B (en) * | 2018-09-05 | 2020-05-12 | 天津大学 | Calibration method of optical reference piece capable of providing position and angle references |
-
2019
- 2019-01-31 CN CN201910099349.8A patent/CN109781002B/en active Active
Also Published As
| Publication number | Publication date |
|---|---|
| CN109781002A (en) | 2019-05-21 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN109781002B (en) | Machine vision-based machine tool full-axis-stroke accurate positioning method | |
| US10189133B2 (en) | Measurement, calibration and compensation system and method for machine tool | |
| US10751883B2 (en) | Robot system with supplementary metrology position coordinates determination system | |
| JP7259111B2 (en) | Method for measuring at least one dimension of an object | |
| JP2006509194A (en) | Workpiece inspection method | |
| JPH1183438A (en) | Position calibration method for optical measuring device | |
| CN110530296B (en) | Method for determining line laser installation error angle | |
| TW201432401A (en) | System and method of measuring computer numerical control probe | |
| US20200094407A1 (en) | Robot system with end tool metrology position coordinates determination system | |
| Zhu et al. | Noncontact 3-D coordinate measurement of cross-cutting feature points on the surface of a large-scale workpiece based on the machine vision method | |
| EP2068113A1 (en) | Calibrating method of image measuring instrument | |
| CN113421310A (en) | Method for realizing cross-field high-precision measurement based on motion position error compensation technology of grating ruler positioning | |
| CN111928776A (en) | Multi-sensor-based non-contact online measurement system and method for numerical control machine tool | |
| JP5098174B2 (en) | 3D shape measuring device | |
| JP2006145560A (en) | Calibration program and method for copying probe | |
| JP2009258098A (en) | Lens measuring apparatus, method for measuring lens, and method for manufacturing lens | |
| CN115289997B (en) | Binocular camera three-dimensional contour scanner and application method thereof | |
| JP2016191663A (en) | Calibration method of optical sensor, and three-dimensional coordinate measuring instrument | |
| Klobucar et al. | Automatic high resolution measurement set-up for calibrating precise line scales | |
| KR101823052B1 (en) | Method of measuring workpiece for correction of cnc machine job | |
| EP2641694B1 (en) | Actuating apparatus, actuating system and method for actuating a working stage to move relative to a platform with high-precision positioning capability | |
| JP2001041711A (en) | Method and apparatus for correcting table deflection of image measuring machine | |
| CN214537774U (en) | Image measuring apparatu Z axle does not have stage difference calibration piece | |
| CN110849266A (en) | Telecentric lens telecentricity debugging method of image measuring instrument | |
| JP3633863B2 (en) | Autonomous determination method of systematic error of surface profile measurement system using calibration object |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |