CN111595279A - Method for constructing actual coordinate system of large workpiece and application thereof - Google Patents
Method for constructing actual coordinate system of large workpiece and application thereof Download PDFInfo
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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
- G01B21/00—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant
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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
- G01B11/005—Measuring arrangements characterised by the use of optical techniques for measuring two or more coordinates coordinate measuring machines
Abstract
The invention discloses a method for constructing a large workpiece actual coordinate system and application thereof, wherein the method comprises the following steps: a calibration process is carried out in advance, and a theoretical coordinate system of the workpiece, theoretical position coordinates of the position pin to be measured under the theoretical coordinate system of the workpiece and a theoretical Z plane are obtained; after the large-scale workpiece is located on the base, the actual coordinate system is solved: respectively measuring the exposed pin body of each pin to be measured by using a three-dimensional measuring system, and calculating an actual measurement coordinate; solving the rotation-translation conversion relation T between the measured coordinate and the theoretical position coordinateRotating shaft(ii) a By TRotating shaftRotating and translating the theoretical coordinate system of the workpiece to obtain an actual coordinate system of the large workpiece; the technical scheme of the invention can reduce errors in the base mounting process and the part placement process, establish a coordinate system which is more in line with the actual situation and improve the measurement precision of the workpiece.
Description
Technical Field
The invention relates to the field of automatic vision measurement, in particular to a method for constructing an actual coordinate system of a large workpiece and application thereof.
Background
In the manufacturing industry, the processing precision is an important basis for measuring the process level, and the over-size brings great loss to enterprises for a long time; the size precision of a workpiece to be measured needs to be strictly controlled in the field of processing and measuring of large-sized workpieces, for example, in the manufacturing fields of automobiles, ships, aerospace and the like, when the workpiece to be measured is automatically measured, in order to prevent the mounting position of the workpiece to be measured from changing, a high-precision base is used for fixing the workpiece to be measured, a plurality of positioning pins are arranged on the high-precision base, the positioning holes of the workpiece to be measured are used as positioning references, the positioning pins are inserted into the positioning holes of the workpiece to be measured during use, the freedom degree of the workpiece to be measured is limited by the cooperation of the positioning pins, and the linear motion of the workpiece to be measured in X, Y, Z three axial directions and the six freedom degrees of the rotation motion around X, Y, Z are controlled.
The traditional method is that after a large-sized workpiece (such as a white body, an airplane fuselage framework, an airplane fuselage skin and the like) is fixed, a three-dimensional measurement system is directly used for obtaining the three-dimensional coordinates of the characteristic points of the workpiece and comparing the three-dimensional coordinates with the theoretical coordinates of the workpiece, and the machining error of the workpiece is judged; because the positioning pin has an adjusting error, and the large-size workpiece has a large weight, the base has a certain deformation after fixing the workpiece, and the adjusting error and the deformation can introduce an integral error into the measuring system, namely, the actual coordinate system and the theoretical coordinate system of the workpiece have a deviation, so that the accuracy of the detection result of the three-dimensional measuring system is influenced.
An improvement of the existing method is that an auxiliary part, such as a reference ball, is connected to the side face of the positioning pin, and the auxiliary part is used for constructing deviation between an actual coordinate system and a theoretical coordinate system, but a connecting rod or other connecting structures are usually arranged between the auxiliary part and the positioning pin, so that errors can still be introduced in the assembling and adjusting process, and the construction precision of the actual coordinate system is influenced.
Disclosure of Invention
In order to solve the problems, the invention provides a method for constructing an actual coordinate system of a large-sized workpiece and a method for evaluating the precision by using the method.
The technical scheme of the invention is as follows:
a method for constructing an actual coordinate system of a large-sized workpiece is characterized in that a base is arranged in a detection/installation station of the large-sized workpiece, a plurality of positioning pins are fixed on the base, and the bottom surfaces of the positioning pins are positioned on the same plane;
at least 3 positioning pins (main positioning pins) are arranged on the base, and the positioning pins control the linear motion of the workpiece to be measured in X, Y, Z three directions and six freedom degrees of rotation around X, Y, Z;
when the large workpiece enters the station, the large workpiece is positioned on the base, and the positioning pin is inserted into the corresponding positioning hole on the workpiece to be detected, so that the large workpiece is positioned and supported;
the following processes were performed in advance:
establishing a theoretical coordinate system of the workpiece according to a theoretical digital model of the large workpiece;
selecting a plurality of positioning pins as positioning pins to be measured, and calibrating theoretical position coordinates (X) of the positioning pins to be measured under the workpiece theoretical coordinate systemni,Yni,Zni) Wherein i is 1,2, …, m is the number of the positioning pins;
the position coordinate is a coordinate value of an intersection point between the central axis of the positioning pin and the bottom surface of the positioning pin;
memory coordinates ZniThe established plane is a theoretical Z plane;
the positioning pins to be tested can limit the linear motion of the workpiece in X, Y, Z three directions and six freedom motion degrees of rotation around X, Y, Z;
in the actual use process, the following steps are utilized to establish the actual coordinate system of the large workpiece:
firstly, when a large-sized workpiece is located on a base, a calibrated three-dimensional measurement system is utilized to respectively measure a pin body exposed out of each locating pin to be measured;
the pin body is cylindrical, and the central coordinate (X) of the pin body under a theoretical coordinate system of the workpiece is obtained by fitting the pin bodyci,Yci,Zci) Projecting the central coordinate onto the theoretical Z plane, and recording the projected coordinate as the actual measurement coordinate (X)ai,Yai,Zai)；
Step two, solving the measured coordinate (X)ai,Yai,Zai) With pre-calibrated theoretical position coordinates (X)ni,Yni,Zni) Rotational-translational conversion relation T betweenRotating shaft；
Wherein, wx、wy、wzAs a constituent parameter of the rotation matrix, Tx、Ty、TzThe composition parameters of the translation matrix;
step three, utilizing TRotating shaftAnd rotating and translating the theoretical coordinate system of the workpiece, and recording the rotated and translated coordinate system as an actual coordinate system of the large workpiece.
Preferably, the position pin to be measured comprises at least three non-collinear main positioning pins;
the main positioning pin is obtained according to a theoretical digital model of the base;
in step two, solving T according to the Bursa modelRotating shaft。
Or, in the scheme of the invention, the position pin to be measured comprises at least four non-coplanar positioning pins;
in step two, solving for T according to rigid body transformationRotating shaft。
Preferably, in order to improve the accuracy of the coordinate system, the method further comprises the fourth step of: marking one or more positioning pins as first positioning pins, and utilizing the first positioning pins to carry out the following correction on an actual coordinate system, wherein the method specifically comprises the following steps:
I. measuring the position coordinate of the first positioning pin by using a three-dimensional measuring system, converting the position coordinate into a current actual coordinate system, recording the position coordinate as a first position coordinate, and calculating the deviation between the first position coordinate and the theoretical position coordinate of the first positioning pin;
the theoretical position coordinates of the first positioning pin are as follows: before the large-scale workpiece is placed, theoretical position coordinates of the first positioning pin in a workpiece theoretical coordinate system are obtained through pre-calibration;
if a plurality of first positioning pins are arranged, calculating the deviation between each first positioning pin and the theoretical position coordinate respectively, and recording the maximum value of the deviation as a difference value A;
II. Judging whether the difference value A exceeds a preset tolerance, if not, enabling the current actual coordinate system to meet the requirement;
if yes, the current actual coordinate system does not meet the requirement, and the rotation-translation conversion relation T between the first position coordinate and the theoretical position coordinate of the first positioning pin is calculatedRepair the(ii) a According to TRepair theRotating and translating the current actual coordinate system to establish a new actual coordinate system;
and III, repeating the step I, II by using the new actual coordinate system until the difference value A does not exceed the preset tolerance, and storing the actual coordinate system obtained by the last iteration.
Furthermore, the first positioning pin comprises a plurality of main positioning pins, and the preset tolerance value is 0.01-0.1 mm.
Further, in the second step, the actually measured coordinates (X) of the positioning pin are solved according to the burst modelai,Yai,Zai) With prestored theoretical position coordinates (X) of locating pinsni,Yni,Zni) Rotational-translational conversion relation T betweenRotating shaftThe method comprises the following steps:
the solution is performed using the following formula:
if the 1 st pin control is in the X, Y direction, the 2 nd pin control X, Z direction … … the b th pin control Z direction, then K, V is represented as follows:
where m is the number of locating pins, K, V the number of rows n of the matrix,
theoretical coordinate values (X) of a plurality of the positioning pins are connectedni,Yni,Zni) And measured coordinate values (X)ai,Yai,Zai) Solving and calculating: w is ax、wy、wz、Tx、Ty、Tz(ii) a Then obtain TRotating shaft。
Further, calibrating theoretical position coordinates of each positioning pin in advance specifically comprises:
before the large-scale workpiece is positioned, the positioning pins are calibrated by using a three-dimensional measuring system, each positioning pin is adjusted to a theoretical digital-analog position, and the position coordinate at the moment is recorded as a theoretical position coordinate.
Further, the three-dimensional measuring system is a laser tracker, a three-coordinate measuring machine or a three-dimensional scanner.
The invention also relates to a method for evaluating the precision by utilizing the actual coordinate system of the large workpiece, which comprises the following steps:
after the large workpiece is positioned, the coordinate of the feature to be measured on the large workpiece is measured by using a three-dimensional measuring system and recorded as a feature point coordinate (X)aj,Yaj,Zaj) Wherein j is 1,2, …, n, n is the number of the features to be measured; through TRotating shaftCalculating the coordinate (X) of the characteristic point coordinate in the actual coordinate system of the workpiecekj,Ykj,Zkj)；
Will coordinate (X)kj,Ykj,Zkj) With the prestored theoretical coordinates (X) of each feature to be measurednj,Ynj,Znj) Making difference to obtain the machining deviation (d) of the large workpiecex,dy,dz) And comparing the machining deviation with the design tolerance of the workpiece, and analyzing whether the current large-scale workpiece is qualified or not.
Further, the characteristic to be measured on the large workpiece is a characteristic hole, a groove or a curved surface which is manually selected in advance according to the characteristics of the workpiece;
theoretical coordinate (X) of the feature to be measurednj,Ynj,Znj) And obtaining the target through a theoretical digital model of a large workpiece.
The scheme of the invention has the following advantages:
1. the errors in the base installation process and the part placement process are reduced, and the measurement precision (less than or equal to 0.1mm) of the workpiece is improved;
2. for the positioning base, only after the workpiece is ensured to be located, a local pin body of the positioning pin can be measured by the three-dimensional measuring system, and the requirement on processing other parts of the base is low;
3. a coordinate system verification link is set, and the coordinate system is iterated circularly until the precision of the coordinate system meets the requirement;
4. practice proves that the deviation of the positioning pin in the Z direction in the practical application process is almost 0, so that each measured coordinate is projected to a theoretical Z plane for calculation when the method is used for practical calculation, the calculation can be simplified, the actual coordinate system of the workpiece can be obtained in real time, and the method is suitable for the automatic measurement process.
Drawings
FIG. 1 is a schematic diagram of a single dowel pin configuration according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a base structure according to an embodiment of the invention.
Detailed Description
The technical solution of the present invention is described in detail below with reference to the accompanying drawings and the detailed description.
A method for constructing an actual coordinate system of a large-sized workpiece is characterized in that a base is arranged in a detection/installation station of the large-sized workpiece, a plurality of positioning pins 1 are fixed on the base, and the bottom surfaces 2 of the positioning pins are positioned on the same plane;
at least 3 positioning pins (main positioning pins) are arranged on the base, and the positioning pins control the linear motion of the workpiece to be measured in X, Y, Z three directions and six freedom degrees of rotation around X, Y, Z;
when a large workpiece enters the station, the large workpiece is positioned on the base, and the positioning pin 1 is inserted into a corresponding positioning hole on the workpiece to be detected, so that the large workpiece is positioned and supported;
the following processes are performed in advance (workpieces of the same type, the pre-calibration process is performed only once):
establishing a theoretical coordinate system of the workpiece according to a theoretical digital model of the large workpiece;
selecting a plurality of positioning pins as positioning pins to be measured, and calibrating theoretical position coordinates (X) of the positioning pins to be measured in a workpiece theoretical coordinate systemni,Yni,Zni) Where i is 1,2, …M, m is the number of the positioning pins;
the position coordinate is a coordinate value of an intersection point between the central axis of the positioning pin and the bottom surface 2 of the positioning pin;
memory coordinates ZniThe established plane is a theoretical Z plane;
the positioning pins to be tested can limit the linear motion of the workpiece in X, Y, Z three directions and six freedom motion degrees of rotation around X, Y, Z;
in the actual use process, the following steps are utilized to establish the actual coordinate system of the large workpiece:
firstly, when a large-sized workpiece is positioned on a base, a calibrated three-dimensional measuring system is utilized to respectively measure a pin body 3 exposed out of each positioning pin to be measured;
the pin body 3 is cylindrical, and the central coordinate (X) of the pin body 3 under the theoretical coordinate system of the workpiece is obtained by fittingci,Yci,Zci) Projecting the central coordinate onto a theoretical Z plane, and recording the projected coordinate as an actual measurement coordinate (X)ai,Yai,Zai)；
Step two, solving the measured coordinate (X)ai,Yai,Zai) With pre-calibrated theoretical position coordinates (X)ni,Yni,Zni) Rotational-translational conversion relation T betweenRotating shaft；
Wherein, wx、wy、wzAs a constituent parameter of the rotation matrix, Tx、Ty、TzThe composition parameters of the translation matrix;
step three, utilizing TRotating shaftAnd rotating and translating the theoretical coordinate system of the workpiece, and recording the rotated and translated coordinate system as an actual coordinate system of the large workpiece.
Wherein, mark the theoretical position coordinate of each locating pin in advance, specifically do:
before the large-scale workpiece is positioned, the positioning pins are calibrated by using a three-dimensional measuring system, each positioning pin is adjusted to a theoretical digital-analog position, and the position coordinate at the moment is recorded as a theoretical position coordinate.
The positioning pin to be measured comprises at least three non-collinear main positioning pins;
the main positioning pin is obtained according to a theoretical digital model of the base;
in step two, solving T according to the Bursa modelRotating shaft。
Or the positioning pin to be measured comprises at least four non-coplanar positioning pins;
in step two, solving for T according to rigid body transformationRotating shaft。
In this embodiment, a burst model is used to solve TRotating shaftIn step two, the measured coordinates (Y) of the locating pin are solved according to the burst modelai,Yai,Zai) With prestored theoretical position coordinates (X) of locating pinsni,Yni,Zni) Rotational-translational conversion relation T betweenRotating shaftThe method comprises the following steps:
the solution is performed using the following formula:
if the 1 st pin control is in the X, Y direction, the 2 nd pin control X, Z direction … … the b th pin control Z direction, then K, V is represented as follows:
where m is the number of locating pins, K, V the number of rows n of the matrix,
theoretical coordinate value (X) of simultaneous multiple positioning pinsni,Yni,Zni) And measured coordinate values (X)ai,Yai,Zai) Solving and calculating: w is ax、wy、wz、Tx、Ty、Tz(ii) a Then obtain TRotating shaft。
In order to improve the precision of the coordinate system, the embodiment further includes a fourth step:
marking one or more positioning pins as first positioning pins, and utilizing the first positioning pins to carry out the following correction on an actual coordinate system, wherein the method specifically comprises the following steps:
I. measuring the position coordinate of the first positioning pin by using a three-dimensional measuring system, converting the position coordinate into a current actual coordinate system, recording the position coordinate as a first position coordinate, and calculating the deviation between the first position coordinate and the theoretical position coordinate of the first positioning pin;
the theoretical position coordinates of the first positioning pin are as follows: before the large-scale workpiece is placed, theoretical position coordinates of the first positioning pin in a workpiece theoretical coordinate system are obtained through pre-calibration;
if a plurality of first positioning pins are arranged, calculating the deviation between each first positioning pin and the theoretical position coordinate respectively, and recording the maximum value of the deviation as a difference value A;
II. Judging whether the difference value A exceeds a preset tolerance, if not, enabling the current actual coordinate system to meet the requirement;
if yes, the current actual coordinate system does not meet the requirement, and the rotation-translation conversion relation T between the first position coordinate and the theoretical position coordinate of the first positioning pin is calculatedRepair the(ii) a According to TRepair theRotating and translating the current actual coordinate system to establish a new actual coordinate system;
and III, repeating the step I, II by using the new actual coordinate system until the difference value A does not exceed the preset tolerance, and storing the actual coordinate system obtained by the last iteration.
In order to facilitate identification and calculation, during application, the first positioning pin comprises a plurality of main positioning pins, and the preset tolerance value is 0.01-0.1 mm.
In this embodiment, the three-dimensional measurement system is a laser tracker, a three-coordinate measuring machine, or a three-dimensional scanner.
As an application of the actual coordinate system, the technical solution further includes:
a method for evaluating the precision by using the actual coordinate system of a large workpiece specifically comprises the following steps:
after the large-sized workpiece is positioned, three-dimensional operation is utilizedThe measuring system measures the coordinate of the feature to be measured on the large workpiece and records the coordinate as the coordinate (X) of the feature pointaj,Yaj,Zaj) Wherein j is 1,2, …, n, n is the number of the features to be measured; through TRotating shaftCalculating the coordinate (X) of the characteristic point coordinate in the actual coordinate system of the workpiecekj,Ykj,Zkj)；
Will coordinate (X)kj,Ykj,Zkj) With the prestored theoretical coordinates (X) of each feature to be measurednj,Ynj,Znj) Making difference to obtain the machining deviation (d) of the large workpiecex,dy,dz) And comparing the machining deviation with the design tolerance of the workpiece, and analyzing whether the current large-scale workpiece is qualified or not.
The characteristic to be measured on the large workpiece is a characteristic hole, a groove or a curved surface which is manually selected in advance according to the characteristics of the workpiece;
theoretical coordinate (X) of the feature to be measurednj,Ynj,Znj) And obtaining the target through a theoretical digital model of a large workpiece.
Taking the large workpiece to be measured as the whole vehicle body of the vehicle as an example, according to the characteristics of different vehicle types and measurement requirements, characteristic holes, grooves, cylinders, front cover curved surfaces, vehicle door installation grooves and the like on the large workpiece are manually selected in advance as characteristic points to be measured.
As shown in fig. 2, the base of the white body of the whole automobile is provided with eight positioning pins, wherein the positioning pins at the front right, the rear right and the rear left are main positioning pins 4; the front right locating pin controls three directions of XYZ, the rear right locating pin controls two directions of YZ, and the rear left locating pin controls the direction of Z.
By adopting the technical scheme of the invention, the errors in the base mounting process and the part placement process can be reduced, a coordinate system more conforming to the actual situation is established, and the measurement precision (less than or equal to 0.1mm) of the workpiece is improved.
The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. The foregoing description is not intended to be exhaustive or to limit the invention to the precise form disclosed, and obviously many modifications and variations are possible in light of the above teaching. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and its practical application to enable others skilled in the art to make and use various exemplary embodiments of the invention and various alternatives and modifications thereof. It is intended that the scope of the invention be defined by the following claims and their equivalents.
Claims (10)
1. A method for constructing an actual coordinate system of a large-sized workpiece is characterized in that a base is arranged in a detection/installation station of the large-sized workpiece, a plurality of positioning pins are fixed on the base, and the bottom surfaces of the positioning pins are positioned on the same plane;
when the large workpiece enters the station, the large workpiece is positioned on the base, and the positioning pin is inserted into the corresponding positioning hole on the workpiece to be detected, so that the large workpiece is positioned and supported;
the following processes were performed in advance:
establishing a theoretical coordinate system of the workpiece according to a theoretical digital model of the large workpiece;
selecting a plurality of positioning pins as positioning pins to be measured, and calibrating theoretical position coordinates (X) of the positioning pins to be measured under the workpiece theoretical coordinate systemni，Yni，Zni) Wherein i is 1,2, …, m is the number of the positioning pins;
the position coordinate is a coordinate value of an intersection point between the central axis of the positioning pin and the bottom surface of the positioning pin;
memory coordinates ZniThe established plane is a theoretical Z plane;
the positioning pins to be tested can limit the linear motion of the workpiece in X, Y, Z three directions and six freedom motion degrees of rotation around X, Y, Z;
the method is characterized in that in the actual use process, the following steps are utilized to establish the actual coordinate system of the large workpiece:
firstly, when a large-sized workpiece is located on a base, a calibrated three-dimensional measurement system is utilized to respectively measure a pin body exposed out of each locating pin to be measured;
the pin body is cylindrical, and the central coordinate (X) of the pin body under a theoretical coordinate system of the workpiece is obtained by fitting the pin bodyci，Yci，Zci) Projecting the central coordinate onto the theoretical Z plane, and recording the projected coordinate as the actual measurement coordinate (X)ai，Yai，Zai)；
Step two, solving the measured coordinate (X)ai，Yai，Zai) With pre-calibrated theoretical position coordinates (X)ni，Yni，Zni) Rotational-translational conversion relation T betweenRotating shaft；
Wherein, wx、wy、wzAs a constituent parameter of the rotation matrix, Tx、Ty、TzThe composition parameters of the translation matrix;
step three, utilizing TRotating shaftAnd rotating and translating the theoretical coordinate system of the workpiece, and recording the rotated and translated coordinate system as an actual coordinate system of the large workpiece.
2. The method for constructing the actual coordinate system of the large workpiece according to claim 1, wherein the positioning pin to be measured comprises at least three main non-collinear positioning pins;
the main positioning pin is obtained according to a theoretical digital model of the base;
in step two, solving T according to the Bursa modelRotating shaft。
3. The method for constructing the actual coordinate system of the large workpiece according to claim 1, wherein the positioning pins to be measured comprise at least four non-coplanar positioning pins;
in step two, solving for T according to rigid body transformationRotating shaft。
4. The method for constructing the actual coordinate system of the large workpiece according to the claim 2 or 3, further comprising the fourth step of: marking one or more positioning pins as first positioning pins, and utilizing the first positioning pins to carry out the following correction on an actual coordinate system, wherein the method specifically comprises the following steps:
I. measuring the position coordinate of the first positioning pin by using a three-dimensional measuring system, converting the position coordinate into a current actual coordinate system, recording the position coordinate as a first position coordinate, and calculating the deviation between the first position coordinate and the theoretical position coordinate of the first positioning pin;
the theoretical position coordinates of the first positioning pin are as follows: before the large-scale workpiece is placed, theoretical position coordinates of the first positioning pin in a workpiece theoretical coordinate system are obtained through pre-calibration;
if a plurality of first positioning pins are arranged, calculating the deviation between each first positioning pin and the theoretical position coordinate respectively, and recording the maximum value of the deviation as a difference value A;
II. Judging whether the difference value A exceeds a preset tolerance, if not, enabling the current actual coordinate system to meet the requirement;
if yes, the current actual coordinate system does not meet the requirement, and the rotation-translation conversion relation T between the first position coordinate and the theoretical position coordinate of the first positioning pin is calculatedRepair the(ii) a According to TRepair theRotating and translating the current actual coordinate system to establish a new actual coordinate system;
and III, repeating the step I, II by using the new actual coordinate system until the difference value A does not exceed the preset tolerance, and storing the actual coordinate system obtained by the last iteration.
5. The method for constructing the actual coordinate system of the large workpiece according to claim 4, wherein the first positioning pin comprises a plurality of main positioning pins, and the preset tolerance value is 0.01-0.1 mm.
6. The method for constructing the actual coordinate system of the large workpiece according to claim 2, wherein in the second step, the actual coordinates (X) of the positioning pin are solved according to a burst modelai，Yai，Zai) With prestored theoretical position coordinates (X) of locating pinsni，Yni，Zni) Rotational-translational conversion relation T betweenRotating shaftThe method comprises the following steps:
the solution is performed using the following formula:
if the 1 st pin control is in the X, Y direction, the 2 nd pin control X, Z direction … … the b th pin control Z direction, then K, V is represented as follows:
where m is the number of locating pins, K, V the number of rows n of the matrix,
theoretical coordinate values (X) of a plurality of the positioning pins are connectedni，Yni，Zni) And measured coordinate values (X)ai，Yai，Zai) Solving and calculating: w is ax、wy、wz、Tx、Ty、Tz(ii) a Then obtain TRotating shaft。
7. The method for constructing the actual coordinate system of the large-sized workpiece according to claim 1, wherein the theoretical position coordinates of each positioning pin are calibrated in advance, and specifically:
before the large-scale workpiece is positioned, the positioning pins are calibrated by using a three-dimensional measuring system, each positioning pin is adjusted to a theoretical digital-analog position, and the position coordinate at the moment is recorded as a theoretical position coordinate.
8. The method for constructing the actual coordinate system of the large workpiece according to claim 1, wherein the three-dimensional measuring system is a laser tracker, a three-dimensional measuring machine or a three-dimensional scanner.
9. A method for evaluating the precision of a large workpiece by using an actual coordinate system is characterized in that,
after the large-sized workpiece is positioned, the coordinate of the feature to be measured on the large-sized workpiece is measured by using the three-dimensional measuring systemAnd is recorded as a feature point coordinate (X)aj，Yaj，Zaj) Wherein j is 1,2, …, n, n is the number of the features to be measured; through TRotating shaftCalculating the coordinate (X) of the characteristic point coordinate in the actual coordinate system of the workpiecekj，Ykj，Zkj)；
Will coordinate (X)kj，Ykj，Zkj) With the prestored theoretical coordinates (X) of each feature to be measurednj，Ynj，Znj) Making difference to obtain the machining deviation (d) of the large workpiecex，dy，dz) And comparing the machining deviation with the design tolerance of the workpiece, and analyzing whether the current large-scale workpiece is qualified or not.
10. The method for performing accuracy evaluation by using the actual coordinate system of the large-sized workpiece according to claim 9, wherein the feature to be measured on the large-sized workpiece is a feature hole, a groove or a curved surface which is manually selected in advance according to the characteristics of the workpiece;
theoretical coordinate (X) of the feature to be measurednj，Ynj，Znj) And obtaining the target through a theoretical digital model of a large workpiece.
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| CN112197725A (en) * | 2020-11-06 | 2021-01-08 | 航天海鹰(镇江)特种材料有限公司 | Accurate positioning method for large composite material part machining tool |
| CN112419314A (en) * | 2020-12-10 | 2021-02-26 | 易思维（杭州）科技有限公司 | Characteristic point eliminating method based on correlation |
| CN112578730A (en) * | 2020-11-16 | 2021-03-30 | 中国航发西安动力控制科技有限公司 | Method for quickly converting reference coordinates in self-adaptive machining |
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| CN115090842A (en) * | 2022-06-06 | 2022-09-23 | 首钢京唐钢铁联合有限责任公司 | Continuous casting machine base positioning method and related equipment |
| CN115079637A (en) * | 2022-06-29 | 2022-09-20 | 歌尔股份有限公司 | Method, device and equipment for establishing workpiece coordinate system and storage medium |
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