CN108620955B - The measurement of machine tool rotary axis error and discrimination method based on monocular vision - Google Patents

The measurement of machine tool rotary axis error and discrimination method based on monocular vision Download PDF

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CN108620955B
CN108620955B CN201810372989.7A CN201810372989A CN108620955B CN 108620955 B CN108620955 B CN 108620955B CN 201810372989 A CN201810372989 A CN 201810372989A CN 108620955 B CN108620955 B CN 108620955B
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lathe
error
point
axis
rotating shaft
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CN108620955A (en
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刘巍
潘翼
李肖
王福吉
贾振元
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Dalian University of Technology
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23Q—DETAILS, COMPONENTS, OR ACCESSORIES FOR MACHINE TOOLS, e.g. ARRANGEMENTS FOR COPYING OR CONTROLLING; MACHINE TOOLS IN GENERAL CHARACTERISED BY THE CONSTRUCTION OF PARTICULAR DETAILS OR COMPONENTS; COMBINATIONS OR ASSOCIATIONS OF METAL-WORKING MACHINES, NOT DIRECTED TO A PARTICULAR RESULT
    • B23Q17/00—Arrangements for observing, indicating or measuring on machine tools
    • B23Q17/24—Arrangements for observing, indicating or measuring on machine tools using optics or electromagnetic waves
    • B23Q17/2452—Arrangements for observing, indicating or measuring on machine tools using optics or electromagnetic waves for measuring features or for detecting a condition of machine parts, tools or workpieces
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23Q—DETAILS, COMPONENTS, OR ACCESSORIES FOR MACHINE TOOLS, e.g. ARRANGEMENTS FOR COPYING OR CONTROLLING; MACHINE TOOLS IN GENERAL CHARACTERISED BY THE CONSTRUCTION OF PARTICULAR DETAILS OR COMPONENTS; COMBINATIONS OR ASSOCIATIONS OF METAL-WORKING MACHINES, NOT DIRECTED TO A PARTICULAR RESULT
    • B23Q17/00—Arrangements for observing, indicating or measuring on machine tools
    • B23Q17/24—Arrangements for observing, indicating or measuring on machine tools using optics or electromagnetic waves
    • B23Q17/2409—Arrangements for indirect observation of the working space using image recording means, e.g. a camera
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T7/00—Image analysis
    • G06T7/80—Analysis of captured images to determine intrinsic or extrinsic camera parameters, i.e. camera calibration
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T2207/00—Indexing scheme for image analysis or image enhancement
    • G06T2207/30—Subject of image; Context of image processing
    • G06T2207/30108—Industrial image inspection
    • G06T2207/30164—Workpiece; Machine component

Abstract

The present invention is based on the measurements of the machine tool rotary axis error of monocular vision to belong to lathe geometric error fields of measurement with discrimination method, is related to a kind of method using monocular vision measurement lathe rotating shaft geometric error measurement and identification.This method is using monocular camera during rotating shaft interval, turning round twice in succession, acquisition has the positioning target image of coded markings point, by the image procossing to intermittent rotary, rebuild coordinate of the coded markings point under lathe coordinate system, utilize mathematical point and corresponding relationship of the actual point coordinate in error matrix model, solve lathe independent position error, lathe composition error is acquired using to the image procossing that continuous rotation is shot, lathe independent position error is finally eliminated in lathe composition error and obtains lathe dependence location error.This method efficiently solves the problems, such as that measurement process is cumbersome and identification model is complicated, realizes non-cpntact measurement using monocular vision, equipment cost is low and equipment robustness is high.

Description

The measurement of machine tool rotary axis error and discrimination method based on monocular vision
Technical field
The invention belongs to lathe geometric error fields of measurement, are related to a kind of utilization monocular vision measurement lathe rotating shaft geometry The method of error measure and identification.
Background technique
It is right with the quick raising of the high speed development and level of processing of the high-tech sectors such as Aeronautics and Astronautics, nuclear power, metallurgy High-end numerical control machine and the demand of equipment increase rapidly, also propose requirements at the higher level to the machining accuracy of numerically-controlled machine tool.Five-axle linkage The numerical control processing main manufacturing process continuous, smooth and complex-curved as space, more traditional three-axis numerical control processing are being processed It has a distinct increment in precision, quality and efficiency, and important component of the rotating shaft as five-axle number control machine tool, geometry miss Poor work in-process couples to form complicated space error by multiaxis, seriously affects the machining accuracy of lathe, so five axis of research The measurement and identification of error of rotary axle have realistic meaning in linkage numerical control machine.Current main machine tool error detection method Have: standard component measurement, laser interferometer, ball bar, plane grating, R-test etc., wherein vision measuring method is at low cost, structure The advantages such as simplicity, measurement accuracy height, it can be achieved that machine tool error non-cpntact measurement, therefore, invent a kind of easy to operate, measurement at This is low, and the high error of rotary axle detection of measurement accuracy is particularly important with identification technique.
" one kind five of 105371793 A of Patent No. CN of Zhou Xiangdong, Tang little Qi of the Central China University of Science and Technology et al. invention Axis rotary axis of machine tool geometric error is once loaded measurement method " spatial error model based on mechanism, the survey that is once loaded can be passed through Amount, calculates the ten binomial geometric error parameters of two rotary shafts of five-axle number control machine tool, but this method belongs to contact type measurement side Method, and more gauge heads is required to touch the different measuring surface of square benchmark test specimen one by one, operating process is relatively complicated.Xi'an Rett is fast A kind of " number of 102744648 A of Patent No. CN of woods capital, Wang Xiu peak of fast manufacturing engineering research Co., Ltd et al. invention Control machine tool rotary working table error measure and isolated method " use measurement in platen face by current vortex sensor The metal ring of the heart, in conjunction with the non-cpntact measurement of the achievable lathe geometric error of error decoupling method, this method structure is simple, grasps Facilitate, but be relatively suitable for the error-detecting of linear axis, and higher cost is not particularly suited for the measurement of error of rotary axle and distinguishes Know.
Summary of the invention
The invention solves technical problem be to overcome problem of the prior art, invent a kind of lathe based on monocular vision Error of rotary axle measurement and discrimination method.This method is using single camera vision system combination positioning target detection five-axle number control machine tool Error of rotary axle realizes the multinomial error separate of single measurement of rotating shaft.Installation contains coding first on platen The positioning target of mark point simultaneously indexes rotating shaft, adopts during lathe was every certain scale division value intermittent rotary one week Collection label point image, rebuilds the coordinate under coded markings point lathe coordinate system using camera imaging model, by measurement point coordinate It is brought into solution lathe independent position error in error matrix model；It sets lathe continuous rotary one week later, control camera is every Label point image is acquired every identical scale division value, can similarly acquire lathe composition error, eliminating lathe independent position error is machine Bed rely on location error, this method using coded markings point combination monocular vision realize rotating shaft of numerical control machine error detection and Identification, efficiently solve measurement process it is cumbersome and identification model challenge.It recognizes model simply and is non-cpntact measurement, behaviour Make simply, equipment cost is low, robustness is high.
The technical scheme adopted by the invention is that a kind of measurement of machine tool rotary axis error and identification side based on monocular vision Method, it is characterized in that, this method using monocular camera during rotating shaft interval, turning round twice in succession, and acquisition is with coding The positioning target image of mark point rebuilds coded markings point under lathe coordinate system by the image procossing to intermittent rotary Coordinate solves lathe independent position error using mathematical point and corresponding relationship of the actual point coordinate in error matrix model, then Lathe composition error can be acquired by the image procossing shot to continuous rotation, is finally eliminated in lathe composition error Lathe independent position error obtains lathe and relies on location error；Specific step is as follows for method:
The first step installs experimental provision
Experimental provision is made of monocular camera 1, positioning target 2, platen 3, system mounting rack 4, fixture 5, monocular The vertical platen 3 of camera 1 is mounted on system mounting rack 4, first gridiron pattern scaling board is clamped on platen 3 quasi- Standby calibration monocular camera；Fixture 5 is mounted on platen 3, to facilitate more changing the outfit for positioning target 2 and gridiron pattern scaling board Lathe rotating shaft C axis to be measured is zeroed by folder；
Positioning target 2 is photoetching glass plate, and upper surface photoetching has the first, second, third, fourth circle of the distribution that assumes diamond in shape Encoded point 69,71,73,75, and machine is established positioned at the centre code point 119 of picture centre, and with centre code point 119 for origin Bed coordinate system；
Second step, camera calibration
The present invention demarcates the intrinsic parameter of monocular camera and abnormal according to Zhang Shi standardization combined high precision gridiron pattern scaling board Variable element, selection some coordinates in space are (Xp, Yp, Zp), subpoint coordinate is (x, y) in picture plane, comprehensively considers reality The distortion phenomenon of imaging, as follows using the non-linear perspective projection model expression of video camera:
Wherein, f is the focal length of monocular camera, αx=f/dx and αy=f/dy is respectively defined as the coke of the normalization on two axis of x, y Away from (x0, y0) it is pixel coordinate system origin, by αx、αy、u0、v0The M that four parameters are constituted0For camera Intrinsic Matrix, R For 3 × 3 unit rotating orthogonal battle array, t is translation vector, the M of composition1For Camera extrinsic matrix number；I.e. by intrinsic parameter αx、αy、 u0、v0And outer parameter R, t determines the relationship of lathe coordinate system and pixel coordinate system；Point (x, y) is the ideal position of subpoint, (x ', y ') is the actual coordinate for considering distortion, δx、δyFor the nonlinear distortion variate of horizontal axis and the longitudinal axis, r is to throw under pixel coordinate system Shadow point is at a distance from origin, k1、k2With k3Respectively single order, second order and three rank coefficient of radial distortion, p1、p2Be single order, second order from Heart distortion factor；Intrinsic parameter α can be obtained by demarcating monocular camerax、αy、u0、v0And distortion parameter k1、k2、k3、p1、p2, and then really Determine camera imaging model；After the calibration of monocular camera 1 is good, gridiron pattern scaling board is replaced with positioning target 2, and be fixed on lathe worker Make on platform 3；
Third step, reference point identifying
Rotating shaft is indexed, acquisition label point diagram during lathe was every certain scale division value intermittent rotary one week Picture rebuilds the coordinate under coded markings point lathe coordinate system using camera imaging model；The present invention uses annulus coded markings The positioning target 2 of point characterizes machine tool motion position, and annulus encoding centre is dark circles mark point, outer ring is concentric circles ring region Domain, for characterizing the identity information of annulus coding, referred to as coding-belt；The circle ring area is equally divided into 10 sections, every section according to angle Corresponding bit；Background colour is white and black, and corresponding binary coding is " 0 ", " 1 "；From the mark point center of circle It sets out, according to certain orientation scanning encoding band, scanning is denoted as 1 to black code band, and white code band is denoted as 0；If do not scanned Coding-belt is then rescaned since center；After run-down, the code value sequence of entire encoded point is all read, and is formed One binary sequence, is eventually converted into decimal integer, to obtain the code value of encoded point；After decoding, according to different coding The code value of mark point recycles the camera imaging model inside and outside parameter demarcated, can rebuild the three of each correspondence markings point Coordinate is tieed up, and passes through coordinate system Reference Transforming, the three-dimensional coordinate that can finally obtain the coded markings point under lathe coordinate system is (Xw, Yw, Zw)；
4th step, error of rotary axle measurement and identification
Rotating shaft of numerical control machine error there are mainly two types of error, be lathe independent position error (PIGE) and lathe respectively according to Rely location error (PDGE), the former is mainly the rigging error of lathe and unrelated with lathe command position, so being constant, the latter It is mainly derived from geometric error caused by the manufacturing defect of numerically-controlled machine tool parts and components, it is related to lathe command position, so to become One function of amount and angle of revolution, the two combine and can indicate the composition error of machine tool rotary axis are as follows:
E=ePIGE+ePDGE(θ) (2)
Lathe rotating shaft lathe independent position error is recognized first, when controlling lathe intermittent movement to a certain position, this When rotating shaft composition error item contain only ePIGE, and connect error and share 4, including 2 linear position errors, 2 corners Error, then its error matrix is represented by
Wherein, εxc、εycFor C axis practical center and the linear position error of desired center in the x direction and the y direction；δxc、δyc It is the practical axis of C axis and ideal axis around the angular errors of X-axis and Y-axis.Due to containing only 4 unknown quantitys in error matrix T, i.e., It is adopted under 0 ° of lathe coordinate system, 90 °, 180 ° and 270 ° of 4 angles according to monocular camera by the indexing to rotating shaft The image for collecting coded markings point rebuilds coded markings point using the coordinate and camera imaging model under pixel coordinate system respectively Coordinate under lathe coordinate system isThe equation obtained using formula (4) is i.e. The lathe independent position error of rotating shaft of numerical control machine can be acquired.Set the mathematical point coordinates of lower 4 angles of lathe coordinate system asSolution formula are as follows:
It recognizes lathe rotating shaft lathe again later and relies on location error, control lathe is run with certain speed, turned round at this time The composition error item of axis is ePIGE+ePDGE(θ), then its error matrix may be expressed as:
Wherein, Δ εxc、ΔεycFor C axis practical center and the linear position error of desired center in the x direction and the y direction；Δ δxc、ΔδycIt is the practical axis of C axis and ideal axis around the angular errors of X-axis and Y-axis, above-mentioned 4 errors are that required lathe returns Shaft lathe relies on location error；It has recognized lathe rotating shaft lathe in a static condition before and has relied on location error, i.e. εxc、 εyc、δxc、δycFor known quantity, then still contain 4 unknown quantitys in T, 0 °, 90 °, 180 ° and 270 ° equally in lathe coordinate system 4 angles under triggering camera shoot and respectively rebuild coded markings point coordinate, be denoted asSolution formula are as follows:
The composition error that rotating shaft of numerical control machine is acquired under quasi-static work subtracts known lathe and relies on position mistake Difference, the as lathe of rotating shaft rely on location error.
The invention has the beneficial effects that realizing rotating shaft of numerical control machine error using coded markings point combination monocular vision Detection and identification, efficiently solve that measurement process is cumbersome and identification model challenge, realized and non-connect using monocular vision Touching measurement, has structure simple, easy to operate, and equipment cost is low and equipment robustness is high.This method identification model is simple and is Non-cpntact measurement realizes the detection and identification of rotating shaft of numerical control machine error, equipment using coded markings point combination monocular vision It is at low cost, robustness is high.
Detailed description of the invention
Fig. 1 is the measurement of machine tool rotary axis error and identification illustraton of model based on monocular vision.Wherein, 1- monocular camera, 2- Positioning target, 3- platen, 4- system mounting rack, 5- fixture.
Fig. 2 is the image of coded markings point on positioning target.Wherein, 69,71,73,75 be respectively first, second, third, 4th circle codification point, 119 be the centre code point of picture centre, and X, Y are the reference axis of lathe coordinate system.
Fig. 3 is the measurement of machine tool rotary axis error and identification principle figure.Wherein, εxc、εycRespectively C axis practical center and reason Think the linear position error of center in the x direction and the y direction, δxc、δycRespectively the practical axis of C axis and ideal axis are around X-axis and Y The angular errors of axis, C axis are lathe theory rotating shaft, and C ' axis is the practical rotating shaft of lathe.
Fig. 4 is that machine tool rotary axis error measures and recognizes flow chart.
Specific embodiment
A specific embodiment of the invention is described in detail below in conjunction with technical solution and attached drawing.
Fig. 1 is the measurement of machine tool rotary axis error and identification illustraton of model based on monocular vision.The present invention uses positioning target 2 For the photoetching glass plate of thickness 3mm, there are four the circle codification point for the distribution that assumes diamond in shape and one are centrally located for upper surface photoetching Encoded point is turned round using monocular camera 1 in rotating shaft interval, twice in succession when measurement by its clamping on platen 3 In the process, acquisition has 2 image of positioning target of coded markings point, and acquisition has the positioning target image of coded markings point, warp The image procossing to intermittent rotary is crossed, coordinate of the coded markings point under lathe coordinate system is rebuild, utilizes mathematical point and actual point Corresponding relationship of the coordinate in error matrix model solves lathe independent position error, using the figure acquired to continuous rotation Lathe composition error is acquired as handling, lathe independent position error is finally eliminated in lathe composition error can acquire lathe dependence Location error.The process of method is as shown in Figure 4, the specific steps are as follows:
The first step, the installation of experimental provision
Experimental provision platform is by monocular camera 1, Feature target 2,5 note group of platen 3, system mounting rack 4 and fixture At gridiron pattern scaling board being installed on platen 3 by fixture 5, then the vertical platen 3 of monocular camera 1 is pacified On system mounting rack 4, lathe rotating shaft C axis to be measured is zeroed.
Second step, camera calibration
This method demarcates the intrinsic parameter of monocular camera and abnormal according to Zhang Shi standardization combined high precision gridiron pattern scaling board Variable element can determine intrinsic parameter α after calibrationx、αy、u0、v0, outer parameter R, t and distortion parameter k1、k2、k3、p1、p2, and then determine Camera imaging model；Gridiron pattern scaling board is changed to positioning target 2 after monocular camera calibration, and is fixed on platen 3 On.
Third step, label point feature identification
For accurate characterization machine tool motion position, using the positioning target for having annulus coded markings point, as shown in Figure 2.It will Annulus encodes region and is equally divided into 10 sections according to angle, every section of corresponding bit, according to certain side when image procossing To scanning encoding band, scanning to black code band is denoted as 1, and white code band is denoted as 0, after run-down, obtains the two of entire encoded point System sequence, being converted into decimal integer is code value, is using the code value and camera imaging model of different coding mark point It is (X that three-dimensional coordinate of the coded markings point under lathe coordinate system, which can be rebuild,w, Yw, Zw)；
4th step, error of rotary axle measurement and identification
Fig. 3 measures for machine tool rotary axis error and identification principle figure, in this method, according to unknown in error matrix model Quantity is measured, sets the scale division value of lathe C axis as 90 °, i.e., during lathe intermittent-rotation one week, is located at 0 °, 90 °, An image is acquired under 180 ° and 270 ° of four angles, and rebuilds the encoded point three-dimensional coordinate containing PIGEIt is sat simultaneously in the lathe established using the central point of piece image as origin In mark system, mathematical point three-dimensional coordinate is sought according to the positional relationship of encoded point on high accuracy positioning targetUsing formula (3), (4), according to mathematical point and actual point coordinate in error Corresponding relationship in matrix model solves lathe independent position error (PIGE)；
After lathe C axis zero, then lathe continuous rotary is controlled one week, equally every 90 ° of triggering camera acquisitions of scale division value Image handles reduction encoded point three-dimensional coordinate by subsequent imageBy Formula (5), (6) can solve the lathe composition error containing PIGE and PDGE, and PIGE is the known quantity that previous step solves at this time, Lathe independent position error (PIGE) is finally eliminated in lathe composition error can be obtained lathe dependence location error (PDGE).
The characteristics of present invention is according to monocular vision non-cpntact measurement solves measurement using simple error identification model Process is cumbersome and recognizes model challenge, has the advantages that structure is simple and convenient to operate, and coded markings point and monocular is utilized to regard Feel the detection and identification for being implemented in combination with rotating shaft of numerical control machine error, there are the spies such as good, the measurement stability height of equipment economy Point.

Claims (1)

1. a kind of measurement of machine tool rotary axis error and discrimination method based on monocular vision, it is characterized in that, this method uses monocular Camera rotating shaft interval, twice in succession turn round during, acquisition have coded markings point positioning target image, by pair The image procossing of intermittent rotary rebuilds coordinate of the coded markings point under lathe coordinate system, utilizes mathematical point and actual point coordinate Corresponding relationship in error matrix model solves lathe independent position error, using what is shot to continuous rotation Image procossing can acquire lathe composition error, and lathe independent position error is finally eliminated in lathe composition error can be obtained lathe Rely on location error；Specific step is as follows for method:
The first step installs experimental provision
Experimental provision is by monocular camera (1), positioning target (2), platen (3), system mounting rack (4) and fixture (5) group At；The vertical platen (3) of monocular camera (1) is mounted on system mounting rack (4), then gridiron pattern scaling board is clamped in Platen is prepared on (3) for camera calibration；Fixture (5) is mounted on platen (3), positioning target is facilitated (2) with the replacement clamping of gridiron pattern scaling board；
Positioning target (2) is photoetching glass plate, and upper surface photoetching has the first circle codification point (69) of the distribution that assumes diamond in shape, the second circle Shape encoded point (71), third circle codification point (73), the 4th circle codification point (75) and centrally located centre code point It (119), is and with centre code point (119) that origin establishes lathe coordinate system；Positioning target (2) is photoetching glass plate, upper surface Photoetching has the first circle codification point (69), the second circle codification point (71), third circle codification point (73), for the distribution that assumes diamond in shape 4 circle codification points (75) and centre code point (119) positioned at picture centre, and be that origin is established with centre code point (119) Lathe coordinate system, four additional circle codification point are used for the motion information of the accurate transmission lathe；Gridiron pattern is demarcated after calibration is good Plate is replaced with positioning target (2), and fixed on platen (3), and lathe rotating shaft C axis to be measured is zeroed；
Second step, camera calibration
The present invention demarcates the intrinsic parameter and distortion ginseng of monocular camera according to Zhang Shi standardization combined high precision gridiron pattern scaling board Number, selection some coordinates in space are (Xp, Yp, Zp), subpoint coordinate is (x, y) in picture plane, comprehensively considers actual imaging Distortion phenomenon uses the non-linear perspective projection model expression of video camera are as follows:
Wherein, f is the focal length of monocular camera, αx=f/dx and αy=f/dy is respectively defined as the normalization focal length on two axis of x, y, (x0, y0) it is pixel coordinate system origin, by αx、αy、u0、v0The M that four parameters are constituted0For camera Intrinsic Matrix, R 3 × 3 unit rotating orthogonal battle array, t are translation vector, the M of composition1For Camera extrinsic matrix number；I.e. by intrinsic parameter αx、αy、u0、v0 And outer parameter R, t determines the relationship of lathe coordinate system and pixel coordinate system；Point (x, y) is the ideal position of subpoint, (x ', y ') For the actual coordinate for considering distortion, δx、δyFor the nonlinear distortion variate of horizontal axis and the longitudinal axis, r is subpoint and original under pixel coordinate system The distance of point, k1、k2With k3Respectively single order, second order and three rank coefficient of radial distortion, p1、p2It is single order, second order centrifugal distortion system Number；Intrinsic parameter α can be obtained by demarcating monocular camerax、αy、u0、v0And distortion parameter k1、k2、k3、p1、p2, and then determine camera at As model；After monocular camera (1) calibration is good, gridiron pattern scaling board is replaced with positioning target (2), and in platen (3) Upper fixation；
Third step, reference point identifying
Rotating shaft is indexed, acquisition label point image during lathe was every certain scale division value intermittent rotary one week, The coordinate under coded markings point lathe coordinate system is rebuild using camera imaging model；The present invention is using annulus coded markings point Positioning target characterizes machine tool motion position, and annulus encoding centre is dark circles mark point, outer ring is concentric annular regions, is used for Characterize the identity information of annulus coding, referred to as coding-belt；The circle ring area is equally divided into 10 sections, every section correspondence one according to angle Binary digit；Background colour is white and black, and corresponding binary coding is " 0 ", " 1 "；From the mark point center of circle, according to Certain orientation scanning encoding band, scanning are denoted as 1 to black code band, and white code band is denoted as 0；If not scanning coding-belt, It is rescaned since center；After run-down, the code value sequence of entire encoded point is all read, and forms a binary system Sequence is eventually converted into decimal integer, to obtain the code value of encoded point；After decoding, according to the code of different coding mark point Value recycles the camera imaging model inside and outside parameter demarcated, can rebuild the three-dimensional coordinate of each correspondence markings point, and pass through Coordinate system Reference Transforming is crossed, the three-dimensional coordinate that can finally obtain the coded markings point under lathe coordinate system is (Xw, Yw, Zw)；
4th step, error of rotary axle measurement and identification
Rotating shaft of numerical control machine error is that lathe independent position error and lathe rely on position and miss respectively there are mainly two types of error Difference, the former is mainly the rigging error of lathe and unrelated with lathe command position, so being constant, the latter is mainly derived from numerical control Geometric error caused by the manufacturing defect of lathe parts and components, it is related to lathe command position, so being variable and angle of revolution One function, the two combine and can indicate the composition error of machine tool rotary axis are as follows: e=ePIGE+ePDGE(θ) (2)
Lathe rotating shaft lathe independent position error is recognized first, when controlling lathe intermittent movement to a certain position, is returned at this time The composition error item of shaft contains only ePIGE, and connect error and share 4, including 2 linear position errors, 2 angular errors, Then its error matrix is represented by
Wherein, εxc、εycFor C axis practical center and the linear position error of desired center in the x direction and the y direction；δxc、δycFor C axis The angular errors of practical axis and ideal axis around X-axis and Y-axis；Due to containing only 4 unknown quantitys in error matrix T, by right The indexing of rotating shaft is acquired according to monocular camera and is encoded under 0 ° of lathe coordinate system, 90 °, 180 ° and 270 ° of 4 angles The image of mark point is rebuild coded markings point lathe respectively and is sat using the coordinate and camera imaging model under pixel coordinate system Mark system under coordinate beIt can be acquired using the equation that formula (4) obtains The lathe independent position error of rotating shaft of numerical control machine；Set the mathematical point coordinates of lower 4 angles of lathe coordinate system asSolution formula are as follows:
Lathe rotating shaft lathe is recognized again and relies on location error, and control lathe is run with certain speed, at this time the synthesis of rotating shaft Error term is ePIGE+ePDGE(θ), then its error matrix indicates are as follows:
Wherein, Δ εxc、ΔεycFor C axis practical center and the linear position error of desired center in the x direction and the y direction；Δδxc、 ΔδycIt is the practical axis of C axis and ideal axis around the angular errors of X-axis and Y-axis, above-mentioned 4 errors are that required lathe relies on position Set error；Lathe rotating shaft lathe independent position error, i.e. ε are recognized in a static condition beforexc、εyc、δxc、δycFor The amount of knowing then still contains 4 unknown quantitys, touches under 0 °, 90 °, 180 ° and 270 ° of 4 angles equally in lathe coordinate system in T It sends out camera to shoot and rebuild coded markings point coordinate respectively, be denoted asIt solves Formula are as follows:
The composition error that rotating shaft of numerical control machine is acquired under quasi-static work subtracts known lathe independent position error i.e. Location error is relied on for the lathe of rotating shaft.
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