CN114782513A - Plane-based point laser sensor installation pose calibration method - Google Patents

Plane-based point laser sensor installation pose calibration method Download PDF

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CN114782513A
CN114782513A CN202210431328.3A CN202210431328A CN114782513A CN 114782513 A CN114782513 A CN 114782513A CN 202210431328 A CN202210431328 A CN 202210431328A CN 114782513 A CN114782513 A CN 114782513A
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laser sensor
machine tool
axis
laser
coordinate system
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CN114782513B (en
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章绍昆
沈昕
赵国波
李卫东
姜振喜
付豪
李博
黄思思
王良泽
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Chengdu Aircraft Industrial Group Co Ltd
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    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T7/00—Image analysis
    • G06T7/50—Depth or shape recovery
    • G06T7/521—Depth or shape recovery from laser ranging, e.g. using interferometry; from the projection of structured light
    • 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
    • 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
    • G06T2207/30244—Camera pose

Abstract

The invention belongs to the field of digital measurement, and particularly relates to a method for calibrating the installation pose of a point laser sensor based on a plane, which comprises the following steps of establishing a laser measurement point kinematics model according to the positioning angle of a machine tool spindle to form a linear equation set taking the installation position and the posture of the laser sensor as unknown numbers; installing a laser sensor and setting a virtual knife length; the laser sensor measures a reference plane at different poses, records the coordinates of each axis of the five-axis numerical control machine tool and the measurement value of the laser sensor under the current measurement pose, and forms a linear equation set taking the installation position and the attitude of the laser sensor as unknown numbers; and calculating the installation position and the attitude of the laser sensor. The method is simple to operate, small in calculated amount, stable and reliable.

Description

Plane-based point laser sensor installation pose calibration method
Technical Field
The invention belongs to the field of digital measurement, and particularly relates to a point laser sensor installation pose calibration method based on a plane.
Background
Under the condition that the machine measurement keeps the clamping position of the part unchanged, the geometric shape of the part is measured, and operations such as repeated clamping of the part are avoided, so that introduction of secondary clamping errors is avoided, and adaptive compensation processing of processing errors is possible. The non-contact on-machine measurement represented by laser measurement is more and more widely applied to high-precision and high-efficiency numerical control machining due to high measurement precision, large sampling data volume and high measurement speed. However, due to assembly errors, the installation pose of the laser sensor inevitably deviates from the theoretical pose, and the measurement accuracy of the geometric shape of the part is directly influenced. Therefore, it is necessary to calibrate the actual installation posture of the laser sensor.
In the prior art, the calibration of the installation pose of the point laser sensor is realized through a special calibration tool. Patent document CN 109341546B discloses a light beam calibration method for a point laser displacement sensor in any installation pose, but the method relies on a light beam calibration tool for the point laser displacement sensor composed of a sine gauge and an index plate, and the operation is complicated.
In order to simplify the calibration tool, part of documents realize the calibration of the mounting position and the posture of the point laser sensor based on a standard ball. Patent documents CN 114136212 a and CN 110186372B each disclose a calibration method for the beam direction of a point laser sensor of a three-coordinate measuring machine based on a standard sphere, and patent documents CN 109773686B and CN 112461177 a each disclose a calibration method for the position and the posture of a point laser based on a standard sphere. The method realizes the calibration of the installation pose of the point laser sensor by depending on the standard ball, on one hand, the calibration process is complex, and on the other hand, the high-precision alignment of the position of the standard ball on a machine tool is difficult to realize, and the operability is poor.
In order to further simplify the calibration process, patent document CN 110500978B discloses an online calibration method for the beam direction vector and the zero point position of a point laser sensor, which uses a standard side plane as a calibration plane, measures the calibration plane with the point laser sensor, constructs a hyperstatic linear equation set by using the measurement result and a coordinate transformation model of a five-axis machine tool, and realizes the calibration of the beam direction vector and the zero point position by solving the equation set. In the method, the kinematic model of the measured point only considers five motion axes of the machine tool, but does not consider the positioning angle of a main shaft of the machine tool, so that the calibration operation can be carried out through only one standard side plane during calibration. In practical engineering application, however, in order to ensure the accuracy of the measured value of the point laser sensor, the included angle between the light beam of the point laser sensor and the calibration plane to be measured should not exceed 3 degrees, so that the movement angle of the rotating shaft of the five-axis machine tool is large, the interference between the spindle part of the machine tool and the workbench is easily caused, and the operability of the method is reduced.
Disclosure of Invention
In order to overcome the problems in the prior art, the invention aims to provide a point laser sensor installation pose calibration method based on a plane.
The invention is realized by the following technical scheme:
a point laser sensor installation pose calibration method based on a plane comprises the following steps,
s1: establishing a laser measuring point kinematics model according to the machine tool spindle positioning angle to form a linear equation set taking the installation position and the posture of a laser sensor as unknown numbers;
s2: installing a calibration tool with a reference plane;
s3: installing a laser sensor and setting a virtual knife length;
s4: the laser sensor measures a reference plane at different poses, records the coordinates of each axis of the five-axis numerical control machine tool and the measurement value of the laser sensor under the current measurement pose, and forms a linear equation set taking the installation position and the attitude of the laser sensor as unknown numbers;
s5: and calculating the installation position and the attitude of the laser sensor.
Further, S1 specifically includes: establishing a machining coordinate system { M } fixedly connected with the machine tool, wherein the origin of the machining coordinate system is positioned at a machine tool machining coordinate offset point, and the coordinate axis direction is consistent with the machine tool absolute coordinate system; establishing a cutter coordinate system { T } fixedly connected with the cutter, wherein the origin point of the cutter coordinate system is located at a cutter point, and the coordinate axis direction is consistent with the machine tool coordinate system { M }; and establishing a laser coordinate system { L } fixedly connected with the laser sensor, wherein the origin point of the laser coordinate system is positioned at a measurement reference zero point, the coordinate axis in the Z direction is consistent with the laser emission axis, and the coordinate axis in the X/Y direction can be selected at will.
The position of the origin of the laser coordinate system { L } relative to the tool coordinate system { T } can be described as
Figure BDA0003610699430000021
The attitude of the Z-axis of the laser coordinate system { L } relative to the tool coordinate system { T } can be described as
Figure BDA0003610699430000022
When the laser sensor measures the reading of l during measurement, the position of the laser measurement point relative to the machine tool coordinate system { M }MP is represented as
Figure BDA0003610699430000031
Wherein the content of the first and second substances,
Figure BDA0003610699430000032
the pose of the tool coordinate system { T } relative to the machine tool coordinate system { M } is determined by a kinematic model of the machine tool, wherein the kinematic model needs to consider the positioning angle of a main shaft of the machine tool. Equation (8) is a laser measurement point kinematics model considering the machine tool spindle positioning angle.
Equation (8) is developed as a linear system of equations, expressed as
AX＝B (9)
Wherein X ═ δ X, δ y, δ z, δ i, δ j, δ k)TIs an unknown number of a linear equation set and is a 6-dimensional column vector; a is a coefficient matrix of a linear equation set, is a 3 multiplied by 6 order matrix, and can be represented by coordinates of each rotating shaft of a five-shaft numerical control machine tool and measurement reading of a laser sensor; and B is a constant term of a linear equation set, is a 3-dimensional column vector and can be represented by coordinates of each translation axis and coordinates of a measuring point of the five-axis numerical control machine tool.
The equation set comprises 6 unknowns including delta x, delta y, delta z, delta i, delta j and delta k, when the laser sensor is calibrated based on a reference plane, the reference plane with known position needs to be measured under more than 6 different machine tool pose states, more than 6 linear equations are further constructed, and the equation set is solved through an analysis or fitting method.
Further, S2 specifically includes: and installing a calibration tool with a reference plane, and ensuring that the reference plane equation is a known quantity expressed as F (x, y, z) ═ 0 under a machining coordinate system.
Furthermore, because the laser measuring point kinematics model in the formula (8) considers the positioning angle of the spindle of the machine tool, under the condition that the axis of the spindle is not perpendicular to the calibration plane due to the motion of the rotating shaft of the machine tool, the rotation of the spindle can cause the change of the measured data of the laser sensor on the XY plane or the parallel plane thereof. Therefore, the reference plane can be set to be perpendicular to the axis of the spindle of the five-axis numerical control machine tool, namely the reference plane is parallel to the XY plane of the machine tool, the equation of the reference plane is guaranteed to be a known quantity, the tool installation difficulty is reduced, the calibration calculation process is simplified, the large-amplitude swing of the machine tool rotating shaft in the calibration process is avoided, and the interference risk of the spindle part and the workbench is reduced.
Further, S3 specifically includes: the laser sensor is installed on the main shaft of the five-axis numerical control machine tool through the tool holder, the light of the laser sensor is along the axis direction of the main shaft of the five-axis numerical control machine tool, and the laser sensor can rotate along with the main shaft of the machine tool. And setting a virtual cutter length, wherein the virtual cutter length is the projection length of the distance from the end surface of the spindle to the ideal position of the measurement reference zero point of the laser sensor in the axial direction of the spindle of the machine tool. At this time, the virtual edge point is the origin of the tool coordinate system { T }.
Due to the deviation of the installation pose of the laser sensor, the measurement reference zero point of the laser sensor inevitably deviates from the position of the virtual tool nose, and the laser emission axis also deviates from the direction of the main shaft of the machine tool, as shown in fig. 2.
Further, S4 specifically includes: the laser sensor is controlled by the movement of the five-axis numerical control machine tool to measure the reference plane at n different positions and postures, wherein n is not less than the dimension of an unknown number X, and the amount of exercise (X) of the five-axis numerical control machine tool at each measuring position and posture is recordedi,Yi,Zi,Mi,Ni,Si) And laser sensor measurement value liWhere i is 1,2, …, n; n is more than or equal to 6.
According to the recorded coordinates of each axis of the five-axis numerical control machine tool and the measured value of the laser sensor under each measurement pose, n linear equations are reconstructed by combining a reference plane equation F (x, y, z) with 0 and a linear equation system AX with B to form an n-order linear equation system
Figure BDA0003610699430000041
The unknown number X is an expression of the installation position (delta X, delta y, delta z) and the attitude (delta i, delta j, delta k) of the laser sensor, is a 6-dimensional column vector and is a coefficient matrix
Figure BDA0003610699430000042
The expression of the coordinate of each rotating shaft of the five-axis numerical control machine tool and the measurement reading of the laser sensor is an n multiplied by 6 order matrix and a constant term
Figure BDA0003610699430000043
The expression is the expression of the coordinate of each translation axis and the coordinate of a measuring point of the five-axis numerical control machine tool and is an n-dimensional column vector.
Still further, the different positions and attitudes of the machine tool should satisfy the following conditions:
(1) and ensuring that the reference plane is positioned in the effective stroke of the laser sensor.
(2) Guarantee form coefficient matrix
Figure BDA0003610699430000044
Is satisfied with
Figure BDA0003610699430000045
Matrix of
Figure BDA0003610699430000046
Condition number of
Figure BDA0003610699430000047
As small as possible.
Furthermore, the calibration operation can be performed near the zero position of the rotating shaft of the machine tool, so that the risk of interference between a spindle part of the machine tool and a workbench due to the excessive motion amount of the rotating shaft of the five-axis machine tool is avoided, and the operability of the calibration operation is improved.
Further, S5 specifically includes: the linear equation system constructed in S4 is solved, and X ═ (δ X, δ y, δ z, δ i, δ j, δ k) is calculatedTAnd the installation position and the posture of the laser sensor are identified.
Furthermore, according to the number of the measuring points, the installation pose of the laser sensor can be identified according to the following method:
s51: when n is 6, the matrix A is a 6-order square matrix and can be directly solved by adopting an analytic method;
s52: when n >6, the matrix a is a long matrix of rank 6, which can be solved using a least squares fit.
The application has the advantages that:
according to the invention, the laser sensor is controlled by the five-axis numerical control machine tool to measure the same reference plane at different positions and postures, and the actual installation pose of the laser sensor is obtained by identification by combining the actual measurement result of the laser sensor and the laser measurement point kinematics model, so that the accurate calibration of the installation pose of the point laser sensor is realized. The method is simple to operate, small in calculated amount, stable and reliable.
Drawings
Fig. 1 is a flow chart of calibration of installation pose of a point laser sensor based on a reference plane.
Fig. 2 is a schematic diagram of deviation of installation pose of the laser sensor.
Fig. 3-8 are schematic diagrams of calibration positions of laser sensors of the machine tool with the AC double-pendulum structure.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are for explaining the present invention and not for limiting the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
S1: considering the positioning angle of the main shaft of the machine tool, establishing a laser measuring point kinematics model to form a linear equation system taking the installation position and the posture of the laser sensor as unknown numbers
Establishing a machining coordinate system { M } fixedly connected with the machine tool, wherein the origin point of the machining coordinate system is located at a machine tool machining coordinate offset point, and the coordinate axis direction is consistent with the machine tool absolute coordinate system; establishing a cutter coordinate system { T } fixedly connected with a cutter, wherein the origin point of the cutter coordinate system is located at a cutter point, and the coordinate axis direction is consistent with a machine tool coordinate system { M }; and establishing a laser coordinate system { L } fixedly connected with the laser sensor, wherein the origin point of the laser coordinate system is positioned at a measurement reference zero point, the coordinate axis in the Z direction is consistent with the laser emission axis, and the coordinate axis in the X/Y direction can be selected at will.
The position of the origin of the laser coordinate system { L } relative to the tool coordinate system { T } can be described as
Figure BDA0003610699430000051
The attitude of the Z-axis of the laser coordinate system { L } relative to the tool coordinate system { T } can be described as
Figure BDA0003610699430000052
During the measurement, the laser sensor measures the reading asl, the position of the laser measuring point relative to the machine coordinate system { M }MP is represented as
Figure BDA0003610699430000053
Wherein, the first and the second end of the pipe are connected with each other,
Figure BDA0003610699430000061
the pose of the tool coordinate system { T } relative to the machine tool coordinate system { M } is determined by a kinematic model of the machine tool, wherein the kinematic model needs to consider the positioning angle of a main shaft of the machine tool. Equation (8) is a laser measurement point kinematics model considering the machine tool spindle positioning angle.
Equation (8) is developed as a linear system of equations, expressed as
AX＝B (14)
Where X is (δ X, δ y, δ z, δ i, δ j, δ k)TIs an unknown number of a linear equation set and is a 6-dimensional column vector; a is a coefficient matrix of a linear equation set, is a 3 multiplied by 6 order matrix, and can be represented by coordinates of each rotating shaft of a five-axis numerical control machine tool and measurement reading of a laser sensor; and B is a constant term of a linear equation set, is a 3-dimensional column vector and can be represented by coordinates of each translation axis and coordinates of measurement points of the five-axis numerical control machine tool.
The equation set comprises 6 unknowns including delta x, delta y, delta z, delta i, delta j and delta k, when the laser sensor is calibrated on the basis of a reference plane, the reference plane with known positions needs to be measured under more than 6 different machine tool pose states, more than 6 linear equations are further constructed, and the equation set is solved through an analysis or fitting method.
S2: calibration tool with installation reference plane
And installing a calibration tool with a reference plane, and ensuring that the reference plane equation is a known quantity expressed as F (x, y, z) ═ 0 in the machining coordinate system.
Furthermore, because the laser measuring point kinematics model in the formula (8) considers the positioning angle of the spindle of the machine tool, under the condition that the axis of the spindle is not perpendicular to the calibration plane due to the motion of the rotating shaft of the machine tool, the rotation of the spindle can cause the change of the measured data of the laser sensor on the XY plane or the parallel plane thereof. Therefore, the reference plane can be set to be perpendicular to the axis of the spindle of the five-axis numerical control machine tool, namely the reference plane is parallel to the XY plane of the machine tool, the equation of the reference plane is guaranteed to be a known quantity, the tool installation difficulty is reduced, the calibration calculation process is simplified, the large-amplitude swing of the rotating shaft of the machine tool in the calibration process is avoided, and the interference risk of spindle parts and the workbench is reduced.
S3: installing a laser sensor and setting a virtual tool length
The laser sensor is installed on a spindle of the five-axis numerical control machine tool through a tool handle, light of the laser sensor is along the axis direction of the spindle of the five-axis numerical control machine tool, and the laser sensor can rotate along with the spindle of the five-axis numerical control machine tool. And setting a virtual cutter length, wherein the virtual cutter length is the projection length of the distance from the end surface of the spindle to the ideal position of the measurement reference zero point of the laser sensor in the axial direction of the spindle of the machine tool. At this time, the virtual edge point is the origin of the tool coordinate system { T }.
Due to the deviation of the installation pose of the laser sensor, the measurement reference zero point of the laser sensor inevitably deviates from the position of the virtual tool nose, and the laser emission axis also deviates from the direction of the main shaft of the machine tool, as shown in fig. 2.
S4: the laser sensor measures a reference plane at different poses, records the coordinates of each axis of the five-axis numerical control machine tool and the measured value of the laser sensor under the current measuring pose, and forms a linear equation set taking the installation position and the attitude of the laser sensor as unknown numbers
Measuring reference plane at n different positions and postures by controlling laser sensor through movement of five-axis numerical control machine tool, wherein n is not less than dimension of unknown number X, recording movement amount (X) of five-axis numerical control machine tool at each measuring position and posturei,Yi,Zi,Mi,Ni,Si) And laser sensor measurements liWhere i is 1,2, …, n; n is more than or equal to 6.
According to the recorded coordinates of each axis of the five-axis numerical control machine tool and the measured value of the laser sensor under each measurement pose, n linear equations are reconstructed by combining a reference plane equation F (x, y, z) with 0 and a linear equation system AX with B to form an n-order linear equation system
Figure BDA0003610699430000071
The unknown number X is an expression of the installation position (delta X, delta y, delta z) and the attitude (delta i, delta j, delta k) of the laser sensor, is a 6-dimensional column vector and is a coefficient matrix
Figure BDA0003610699430000072
The expression of the coordinate of each rotating shaft of the five-axis numerical control machine tool and the measurement reading of the laser sensor is an n multiplied by 6 order matrix and a constant term
Figure BDA0003610699430000073
The expression is the expression of the coordinate of each translation axis and the coordinate of a measuring point of the five-axis numerical control machine tool and is an n-dimensional column vector.
Specifically, the different positions and postures of the machine tool should satisfy the following conditions:
(1) and ensuring that the reference plane is positioned in the effective stroke of the laser sensor.
(2) Ensuring a construction coefficient matrix
Figure BDA0003610699430000074
Is satisfied with
Figure BDA0003610699430000075
Matrix array
Figure BDA0003610699430000076
Condition number of
Figure BDA0003610699430000077
As small as possible.
Furthermore, the calibration operation can be performed near the zero position of the rotating shaft of the machine tool, so that the risk of interference between a spindle part of the machine tool and a workbench due to the overlarge movement amount of the rotating shaft of the five-axis machine tool is avoided, and the operability of the calibration operation is improved.
S5: calculating laser sensor mounting position and attitude
The linear equation system constructed in S4 is solved, and X ═ δ X, δ y, δ is calculatedz,δi,δj,δk)TAnd the installation position and the posture of the laser sensor are identified.
Specifically, according to the number of the measuring points, the installation pose of the laser sensor can be identified according to the following method:
s51: when n is 6, the matrix A is a 6-order square matrix and can be directly solved by adopting an analytical method;
s52: when n >6, the matrix a is a long matrix of rank 6, which can be solved using a least squares fit.
Example 2
The embodiment discloses a point laser sensor installation pose calibration method suitable for an AC double-swing-head structure five-axis numerical control machine tool, and the flow of the method is shown in figure 1. The specific implementation contents and the cautions are as follows as an embodiment of the invention:
s1: establishing laser measuring point kinematics model
For the machine tool with the AC double-pendulum structure, after the RTCP function is started, the pose of the tool coordinate system { T } relative to the machine tool coordinate system { M } can be expressed as
Figure BDA0003610699430000081
Wherein
Figure BDA0003610699430000082
Figure BDA0003610699430000083
Figure BDA0003610699430000084
Figure BDA0003610699430000085
Wherein, (X, Y, Z, A and C) represent the coordinates of each axis of the machine tool under the RTCP function at the moment, and S represents the positioning angle of the main shaft of the machine tool.
It is assumed that the position of the laser measurement reference point { L } relative to the tool coordinate system { T } can be described as
Figure BDA0003610699430000086
The pose of the laser axis vector with respect to the tool coordinate system can be described as
Figure BDA0003610699430000087
Then there are
Figure BDA0003610699430000088
Figure BDA0003610699430000089
When the length measured by the laser sensor is represented as l in the measurement, the position of the laser measurement point relative to the tool coordinate system { T } is
Figure BDA0003610699430000091
Conversion to the position of the machine coordinate system { M } according to equation (16)MP is represented as
Figure BDA0003610699430000092
Wherein the content of the first and second substances,
Figure BDA0003610699430000093
and the formula (24) is a laser sensor measuring point kinematics model arranged on the AC double-pendulum head structure five-axis numerical control machine tool.
Equation (24) is developed as a system of linear equations, expressed as
AX＝B (25)
Wherein A is a coefficient matrix of a linear equation system
Figure BDA0003610699430000094
In the above formula, the first and second carbon atoms are,
Figure BDA0003610699430000095
x is an unknown number of the system of linear equations
X＝(δx,δy,δz,δi,δj,δk)T
B is a constant term of a system of linear equations
B＝(x-X,y-Y,z-Z)T
As can be seen from equation (25), the equation set includes 6 unknowns δ x, δ y, δ z, δ i, δ j, and δ k. When a certain reference plane is adopted to calibrate the laser sensor, the reference plane with known position needs to be measured under more than 6 different machine tool pose states, more than 6 linear equations are further constructed, and an equation set is solved through an analysis or fitting method.
S2: calibration tool with one reference plane for installation
For a machine tool of AC double-pendulum structure, the main shaft axis is parallel to the Z axis in the initial position. In order to reduce the tool installation difficulty and simplify the calibration calculation process, an XY plane of a machining coordinate system is selected as a reference plane of the calibration tool, and the equation of the reference plane at the moment is that z is 0.
S3: installing a laser sensor and setting a virtual tool length
The laser sensor is installed on a spindle of the five-axis numerical control machine tool through a tool handle, light of the laser sensor is along the axis direction of the spindle of the five-axis numerical control machine tool, and the laser sensor can rotate along with the spindle of the five-axis numerical control machine tool. And setting a virtual cutter length, wherein the virtual cutter length value is the projection length of the distance from the end surface of the main shaft to the ideal position of the reference zero point measured by the laser sensor in the axial direction of the main shaft of the machine tool. At this time, the virtual edge point is the origin of the tool coordinate system { T }. Due to the deviation of the installation pose of the laser sensor, the measurement reference zero point of the laser sensor inevitably deviates from the position of the virtual tool nose, and the laser emission axis also deviates from the direction of the main shaft of the machine tool, as shown in fig. 2.
S41: the laser sensor measures the reference plane at 6 different poses, records the motion amount and the measured value of the laser sensor
When any point on the reference plane Z is measured using the laser sensor, the Z-coordinate of the measurement point is 0. In conjunction with equation (25), the following equation can be obtained
sinAsinS(δx+l·δi)+sinAcosS(δy+l·δj)+cosA(δz+l·δk)＝-Z (26)
As can be seen from the above equation, solving for δ x, δ y, δ z, δ i, δ j, and δ k6 unknowns requires the following 2 conditions to be satisfied:
(1) for an actual installation scene of the laser sensor, the laser sensor is limited by the measurable angle of the laser sensor, and in order to ensure that the laser sensor can obtain an effective measurement value of a reference plane, the position near the 0-degree position of the A axis of the machine tool is selected for measurement, so that the interference risk between a main shaft component of the machine tool and a workbench is avoided, and the operability of calibration operation is improved;
(2) in at least 6 different machine tool positions (X)i,Yi,Zi,Ai,Ci,Si) (i ═ 1,2, …, n; n is more than or equal to 6), measuring the reference plane, and recording the corresponding reading l of the laser displacement sensori,(i＝1,2,…,n；n≥6)。
Specifically, the measurement is performed using 6 different positions and attitudes in this example, as shown in fig. 3-8. The machine tool starts the RTCP function, controls the machine tool to move to the position where X is equal to 0, Y is equal to 0, Z is equal to 0, A is equal to 0, C is equal to 0, and S is equal to 0, and comprises the following steps:
s41-1: controlling the machine tool to move to a position where Z is 0, A is 0, S is 0, and recording the reading of the laser sensor as l00；
S41-2: controlling the machine tool to move to a position Z-delta Z, A-0 and S-0, and recording the reading of the laser sensor as l0z；
S41-3: controlling the machine tool to move to the position Z equal to 0, A equal to delta A and S equal to 0, and recordingRecord a laser sensor reading of la0；
S41-4: controlling the machine tool to move to a position where Z is equal to delta Z, A is equal to delta A, S is equal to 0, and recording the reading of the laser sensor as lay；
S41-5: controlling the machine tool to move to the position Z equal to 0, A equal to delta A, S equal to delta S, and recording the reading of the laser sensor as ls0；
S41-6: controlling the machine tool to move to the position Z, A, S and S, and recording the reading of the laser sensor as lsz。
According to the coordinate of each axis of the five-axis numerical control machine tool and the measured value of the laser sensor under each measuring pose recorded in the measuring process, the following equation set can be constructed
Figure BDA0003610699430000111
Wherein, the first and the second end of the pipe are connected with each other,
Figure BDA0003610699430000112
coefficient matrix being a linear system of equations
Figure BDA0003610699430000113
In the above formula
Figure BDA0003610699430000114
X is an unknown number of the system of linear equations
X＝(δx,δy,δz,δi,δj,δk)T
Figure BDA0003610699430000115
Is a constant term of a linear system of equations
Figure BDA0003610699430000121
S51: laser sensor mounting position and attitude identification
And calculating the installation position and the installation posture of the laser sensor according to the movement amount of the machine tool and the measurement value of the laser sensor recorded in different positions and postures of the machine tool in the S41. Since the number of the measuring points n is 6, the method can be directly solved by adopting an analytical method. Specifically, the method comprises the following steps:
s51-1: calculating an attitude deviation component δ k and a position deviation component δ z
Figure BDA0003610699430000122
S51-2: calculating an attitude deviation component δ j and a position deviation component δ y
Figure BDA0003610699430000123
Wherein the content of the first and second substances,
Figure BDA0003610699430000124
s51-3: calculating an attitude deviation component δ i and a position deviation component δ x
Figure BDA0003610699430000125
Wherein the content of the first and second substances,
Figure BDA0003610699430000126
Figure BDA0003610699430000127
therefore, the actual installation position and the attitude of the laser sensor can be completely solved.
Example 3
The difference from example 2 is that: the reference plane is measured with more than 6 different poses in step S4, and the laser sensor installation pose is identified with a least squares fit in step S5. The specific implementation steps are as follows:
s42: the laser sensor measures the reference plane with more than 6 different poses, records the motion amount and the measured value of the laser sensor
The laser sensor is controlled by the movement of the five-axis numerical control machine tool to measure the reference plane at different positions and postures, and the movement amount of the five-axis numerical control machine tool and the measurement value of the laser sensor at each measuring position and posture are recorded.
Specifically, more than 6 different positions and attitudes are taken for measurement, and machine coordinate value data (X) is recordedi,Yi,Zi,Ai,Ci,Si) And corresponding laser displacement sensor reading liWherein i is 1,2, …, n; n is a radical of an alkyl radical>6. In order to ensure that the laser sensor can effectively measure the reference plane, the swing angle of the A shaft of the machine tool is positioned near the position of 0 degree for measurement.
According to the coordinate of each axis of the five-axis numerical control machine tool and the measured value of the laser sensor under each measurement pose recorded in the measurement process, the following equation set can be constructed
Figure BDA0003610699430000131
S52: laser sensor mounting position and attitude identification
Constructing laser sensor installation position and attitude identification objective function
min f(δx,δy,δz,δi,δj,δk) (29)
Wherein, the first and the second end of the pipe are connected with each other,
Figure BDA0003610699430000132
the actual mounting position and attitude of the laser sensor can be completely determined by solving the formula (29) by the least square method.

Claims (9)

1. A point laser sensor installation pose calibration method based on a plane is characterized by comprising the following steps: comprises the following steps of (a) preparing a solution,
s1: establishing a laser measuring point kinematics model according to the positioning angle of the machine tool spindle to form a linear equation set taking the installation position and the posture of a laser sensor as unknown numbers;
s2: installing a calibration tool with a reference plane;
s3: installing a laser sensor and setting a virtual knife length;
s4: the laser sensor measures a reference plane at different poses, records the coordinates of each axis of the five-axis numerical control machine tool and the measurement value of the laser sensor under the current measurement pose, and forms a linear equation set taking the installation position and the attitude of the laser sensor as unknown numbers;
s5: and calculating the installation position and the attitude of the laser sensor.
2. The plane-based point laser sensor installation pose calibration method according to claim 1, characterized in that:
s1 specifically includes: establishing a machining coordinate system { M } fixedly connected with the machine tool, wherein the origin of the machining coordinate system is positioned at a machine tool machining coordinate offset point, and the coordinate axis direction is consistent with the machine tool absolute coordinate system; establishing a cutter coordinate system { T } fixedly connected with a cutter, wherein the origin point of the cutter coordinate system is located at a cutter point, and the coordinate axis direction is consistent with a machine tool coordinate system { M }; and establishing a laser coordinate system { L } fixedly connected with the laser sensor, wherein the origin of the laser coordinate system is positioned at a measurement reference zero point, the coordinate axis in the Z direction is consistent with the laser emission axis, and the coordinate axes in the X/Y direction are selected randomly.
3. The plane-based point laser sensor installation pose calibration method according to claim 2, characterized in that:
the position of the origin of the laser coordinate system { L } relative to the tool coordinate system { T } is described as
Figure FDA0003610699420000011
The Z-axis of the laser coordinate system { L } is described as the attitude relative to the tool coordinate system { T }
Figure FDA0003610699420000012
When in measurement, the measurement reading of the laser sensor is l, and the position of the laser measurement point relative to the machine tool coordinate system { M }, namelyMP is represented as
Figure FDA0003610699420000013
Wherein, the first and the second end of the pipe are connected with each other,
Figure FDA0003610699420000014
the pose of a tool coordinate system { T } relative to a machine tool coordinate system { M } is determined by a kinematic model of the machine tool, the kinematic model needs to consider the positioning angle of a machine tool spindle, and the formula (8) is a laser measuring point kinematic model considering the positioning angle of the machine tool spindle;
equation (8) is developed as a linear system of equations, expressed as
AX＝B (4)
Wherein X ═ δ X, δ y, δ z, δ i, δ j, δ k)TIs an unknown number of a linear equation set and is a 6-dimensional column vector; a is a coefficient matrix of a linear equation set, is a 3 multiplied by 6 order matrix, and can be represented by coordinates of each rotating shaft of a five-shaft numerical control machine tool and measurement reading of a laser sensor; b is a constant term of a linear equation set, is a 3-dimensional column vector and is expressed by coordinates of each translation axis and coordinates of measuring points of the five-axis numerical control machine tool;
the equation set comprises 6 unknowns including delta x, delta y, delta z, delta i, delta j and delta k, when the laser sensor is calibrated on the basis of a reference plane, the reference plane with known positions needs to be measured under more than 6 different machine tool pose states, more than 6 linear equations are further constructed, and the equation set is solved through an analysis or fitting method.
4. The plane-based point laser sensor installation pose calibration method according to claim 3, characterized in that:
s2 specifically includes: installing a calibration tool with a reference plane, and ensuring that the reference plane equation is a known quantity expressed as F (x, y, z) ═ 0 under a machining coordinate system; and setting the reference plane to be vertical to the axis of the main shaft of the five-axis numerical control machine tool, and ensuring that the equation of the reference plane is a known quantity.
5. The plane-based point laser sensor installation pose calibration method according to claim 4, characterized in that:
s3 specifically includes: the laser sensor is mounted on a spindle of the five-axis numerical control machine tool through a tool handle, light of the laser sensor is along the axis direction of the spindle of the five-axis numerical control machine tool, and the laser sensor can rotate along the spindle of the five-axis numerical control machine tool; setting a virtual cutter length, wherein the virtual cutter length value is the projection length of the distance from the end surface of the main shaft to the ideal position of the reference zero point measured by the laser sensor in the axial direction of the main shaft of the machine tool; at this time, the virtual edge point is the origin of the tool coordinate system { T }.
6. The plane-based point laser sensor installation pose calibration method according to claim 5, characterized in that:
s4 specifically includes: measuring reference plane at n different positions and postures by controlling laser sensor through movement of five-axis numerical control machine tool, wherein n is not less than dimension of unknown number X, recording movement amount (X) of five-axis numerical control machine tool at each measuring position and posturei,Yi,Zi,Mi,Ni,Si) And laser sensor measurements liWhere i is 1,2, …, n; n is more than or equal to 6;
according to the recorded coordinates of each axis of the five-axis numerical control machine tool and the measured value of the laser sensor under each measurement pose, n linear equations are reconstructed by combining a reference plane equation F (x, y, z) with 0 and a linear equation system AX with B to form an n-order linear equation system
Figure FDA0003610699420000031
Wherein the unknown number X is the mounting position (delta X, delta y, delta z) and attitude (delta i, delta j, delta k) of the laser sensorExpression is 6-dimensional column vector and coefficient matrix
Figure FDA0003610699420000032
The expression of the coordinate of each rotating shaft of the five-axis numerical control machine tool and the measurement reading of the laser sensor is an n multiplied by 6 order matrix and a constant term
Figure FDA0003610699420000033
The expression of the coordinate of each translation axis and the coordinate of a measuring point of the five-axis numerical control machine tool is an n-dimensional column vector.
7. The plane-based point laser sensor installation pose calibration method according to claim 6, characterized in that:
the different positions and postures of the machine tool meet the following conditions:
(1) ensuring that the reference plane is positioned in the effective stroke of the laser sensor;
(2) guarantee form coefficient matrix
Figure FDA0003610699420000034
Is satisfied with
Figure FDA0003610699420000035
Matrix array
Figure FDA0003610699420000036
Condition number of
Figure FDA0003610699420000037
As small as possible.
8. The plane-based point laser sensor installation pose calibration method according to claim 6, characterized in that:
s5 specifically includes: the linear equation system constructed in S4 is solved, and X ═ δ X, δ y, δ z, δ i, δ j, δ k are calculatedTAnd the installation position and the posture of the laser sensor are identified.
9. The plane-based point laser sensor installation pose calibration method according to claim 8, characterized in that:
according to the number of the measuring points, the installation pose of the laser sensor is identified according to the following method:
s51: when n is 6, the matrix A is a 6-order square matrix and is directly solved by adopting an analytic method;
s52: when n is greater than 6, the matrix A is a long matrix with the rank of 6, and is solved by fitting with a least square method.
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