CN114782513B - Point laser sensor mounting pose calibration method based on plane - Google Patents
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Abstract
The application belongs to the field of digital measurement, and particularly relates to a plane-based point laser sensor mounting pose calibration method, which comprises the following steps of establishing a laser measurement point kinematic model according to a machine tool spindle positioning angle to form a linear equation set taking the mounting position and pose of a laser sensor as unknown numbers; installing a laser sensor and setting a virtual cutter length; the laser sensor measures reference planes with different poses, records the coordinates of each axis of the five-axis numerical control machine tool under the current measured pose and the measured value of the laser sensor, and forms a linear equation set taking the installation position and the pose of the laser sensor as unknown numbers; the laser sensor mounting position and attitude are calculated. The method is simple to operate, small in calculated amount, stable and reliable.
Description
Technical Field
The application belongs to the field of digital measurement, and particularly relates to a plane-based point laser sensor mounting pose calibration method.
Background
Under the condition that the clamping position of the part is kept unchanged in the mechanical measurement, the geometric shape of the part is measured, repeated clamping and other operations of the part are avoided, the introduction of secondary clamping errors is avoided, and the self-adaptive compensation processing of processing errors is also enabled to be possible. The non-contact on-machine measurement represented by laser measurement has high measurement accuracy, large sampling data volume and high measurement speed, and is widely applied to high-precision and high-efficiency numerical control machining. However, due to assembly errors, the mounting pose of the laser sensor inevitably deviates from the theoretical pose, and the measurement accuracy of the geometric shape of the part is directly affected. Therefore, it is necessary to calibrate the actual mounting pose of the laser sensor.
In the prior art, the mounting pose calibration of the point laser sensor is realized through a special calibration tool. Patent document CN 109341546B discloses a method for calibrating a beam of a point laser displacement sensor in any mounting pose, but the method relies on a beam calibration tool of the point laser displacement sensor consisting of a sine gauge and an index plate, and is complex to operate.
In order to simplify the calibration tool, part of the literature realizes the calibration of the installation position and the gesture of the point laser sensor based on a standard ball. The patent documents CN 114136212A and CN 110186372B each disclose a calibration method for the beam direction of the point laser sensor of the three-coordinate measuring machine based on the standard sphere, and the patent documents CN 109773686B and CN 112461177A each disclose a calibration method for the position and the posture of the point laser based on the standard sphere. The method relies on the standard ball to realize the calibration of the installation pose of the point laser sensor, on one hand, the calibration process is complex, and on the other hand, the high-precision alignment of the position of the standard ball is difficult to realize on a machine tool, 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 position of a point laser sensor, a standard side plane is taken as a calibration plane, the calibration plane is measured by the point laser sensor, a hyperstatic linear equation set is constructed by using the measurement result and a coordinate transformation model of a five-axis machine tool, and the calibration for the beam direction vector and the zero position of the laser is realized 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 the main shaft of the machine tool, so that the calibration operation can be performed through only one standard side plane during the calibration. However, in practical engineering application, 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 larger, the interference between the spindle part of the machine tool and the workbench is easy to cause, and the operability of the method is reduced.
Disclosure of Invention
In order to overcome the problems in the prior art, the application aims to provide a plane-based point laser sensor mounting pose calibration method.
The application is realized by the following technical scheme:
a method for calibrating the installation pose of a point laser sensor based on a plane comprises the following steps,
s1: according to the positioning angle of the main shaft of the machine tool, a kinematic model of a laser measuring point is established, and a linear equation set taking the installation position and the posture of the laser sensor as unknown numbers is formed;
s2: installing a calibration tool with a reference plane;
s3: installing a laser sensor and setting a virtual cutter length;
s4: the laser sensor measures reference planes with different poses, records the coordinates of each axis of the five-axis numerical control machine tool under the current measured pose and the measured value of the laser sensor, and forms a linear equation set taking the installation position and the pose of the laser sensor as unknown numbers;
s5: the laser sensor mounting position and attitude are calculated.
Further, S1 is specifically: establishing a machining coordinate system { M } fixedly connected with a machine tool, wherein the origin of the machining coordinate system { M } is positioned at a machining coordinate offset point of the machine tool, and the coordinate axis direction is consistent with the absolute coordinate system of the machine tool; establishing a tool coordinate system { T } fixedly connected with a tool, wherein the origin of the tool coordinate system { T } is positioned at a tool point, and the coordinate axis direction is consistent with a machine tool coordinate system { M }; a laser coordinate system { L } fixedly connected with the laser sensor is established, the origin of the laser coordinate system { L } is positioned at a measurement reference zero point, the Z-direction coordinate axis is consistent with the laser emission axis, and the X/Y-direction coordinate axis can be selected at will.
The position of the laser coordinate system { L } origin relative to the tool coordinate system { T } can be described as
The pose of the Z-axis of the laser coordinate system { L } relative to the tool coordinate system { T } can be described as
In the measurement, the laser sensor measures the reading of l, and the position of the laser measuring point relative to the machine coordinate system { M }, thereby M P is represented as
Wherein,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 the machine tool spindle. Equation (8) is a kinematic model of the laser measurement point taking into account the positioning angle of the machine tool spindle.
Expanding equation (8) into a linear system of equations, expressed as
AX＝B (9)
Wherein x= (δx, δy, δz, δi, δj)k) T Is 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 matrix, and can be represented by the coordinates of each rotating shaft of a five-axis numerical control machine tool and the 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 each translational axis coordinate and measuring point coordinate of a five-axis numerical control machine tool.
The equation set contains 6 unknown numbers of δx, δy, δz, δi, δj and δk, when the laser sensor is calibrated based on the reference plane, the reference plane with known positions needs to be measured under the state of more than 6 different machine tool pose states, so as to construct more than 6 linear equations, and the equation set is solved by an analysis or fitting method.
Further, S2 is specifically: and installing a calibration tool with a reference plane, ensuring that a reference plane equation is a known quantity under a machining coordinate system, and expressing as F (x, y, z) =0.
Further, since the kinematic model of the laser measurement point in the formula (8) considers the positioning angle of the spindle of the machine tool, when the rotation axis of the machine tool moves so that the spindle axis is not perpendicular to the calibration plane, the spindle rotation causes the measurement data of the laser sensor to change for the XY plane or the parallel plane thereof. Therefore, the reference plane can be perpendicular to the spindle axis 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 ensured 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 the spindle component and the workbench is reduced.
Further, S3 is specifically: the laser sensor is arranged on the spindle of the five-axis numerical control machine tool through the tool handle, the laser sensor rays are along the axial direction of the spindle of the five-axis numerical control machine tool, and the laser sensor can rotate along the spindle of the random machine tool. Setting a virtual cutter length, wherein the virtual cutter length value is the projection length of the distance from the end face 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 tool tip point is the origin of the tool coordinate system { T }.
Due to the deviation of the mounting pose of the laser sensor, the reference zero point of the laser sensor is inevitably deviated from the position of the virtual tool tip point, and the laser emission axis is also deviated from the direction of the main shaft of the machine tool, as shown in fig. 2.
Further, S4 is specifically: measuring a reference plane with n different positions and attitudes by a five-axis numerical control machine motion control laser sensor, wherein n is not less than the dimension of an unknown number X, and recording the motion quantity (X i ,Y i ,Z i ,M i ,N i ,S i ) And laser sensor measurement l i Where i=1, 2, …, n; n is more than or equal to 6.
Reconstructing n linear equations according to the recorded coordinates of each axis of the five-axis numerical control machine tool under each measuring pose and the measured value of the laser sensor by combining a reference plane equation F (x, y, z) =0 and a linear equation set AX=B to form an n-order linear equation set
Wherein the unknown number X is the expression of the mounting position (delta X, delta y, delta z) and the posture (delta i, delta j, delta k) of the laser sensor, and is a 6-dimensional column vector and a coefficient matrixThe expression of the measurement reading of the laser sensor and the coordinates of each rotation axis of the five-axis numerical control machine tool is an n multiplied by 6 matrix, and a constant term is +.>The expression of each translational axis coordinate and measuring point coordinate of the five-axis numerical control machine tool is an n-dimensional column vector.
Still further, the different positions and attitudes of the machine should satisfy the following conditions:
(1) Ensuring that the reference plane is within the effective travel of the laser sensor.
(2) Ensuring construction coefficient matrixRank meets->Matrix->Condition number of->As small as possible.
Furthermore, the calibration operation can be selectively performed near the zero position of the rotating shaft of the machine tool, the risk of interference between the main shaft component of the machine tool and the workbench caused by overlarge motion quantity of the rotating shaft of the five-axis machine tool is avoided, and the operability of the calibration operation is improved.
Further, S5 is specifically: solving the linear equation set constructed in the S4, and calculating to obtain X= (δx, δy, δz, δi, δj, δk) T And the laser sensor mounting position and gesture recognition are realized.
Still further, according to the number of measurement points, the laser sensor mounting pose can be identified as follows:
s51: when n=6, the matrix a is a 6-order square matrix, which can be directly solved by adopting an analytic method;
s52: when n >6, matrix A is a long matrix of rank 6, which can be solved using least squares fitting.
The application has the advantages that:
according to the application, the five-axis numerical control machine tool is used for controlling the laser sensor to measure the same reference plane in different positions and postures, and the actual installation pose of the laser sensor is obtained through identification by combining the actual measurement result of the laser sensor and the kinematic model of the laser measurement point, 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 the mounting pose of a point laser sensor based on a reference plane.
Fig. 2 is a schematic diagram of laser sensor mounting pose deviation.
Fig. 3-8 are schematic diagrams of laser sensor positioning pose of the AC double-swing-head machine tool.
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more apparent, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application, and it is apparent that the described embodiments are intended to explain the present application rather than to limit the present application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
Example 1
S1: taking the positioning angle of a machine tool spindle into consideration, establishing a kinematic model of a laser measuring point to form a linear equation set taking the installation position and the posture of a laser sensor as unknown numbers
Establishing a machining coordinate system { M } fixedly connected with a machine tool, wherein the origin of the machining coordinate system { M } is positioned at a machining coordinate offset point of the machine tool, and the coordinate axis direction is consistent with the absolute coordinate system of the machine tool; establishing a tool coordinate system { T } fixedly connected with a tool, wherein the origin of the tool coordinate system { T } is positioned at a tool point, and the coordinate axis direction is consistent with a machine tool coordinate system { M }; a laser coordinate system { L } fixedly connected with the laser sensor is established, the origin of the laser coordinate system { L } is positioned at a measurement reference zero point, the Z-direction coordinate axis is consistent with the laser emission axis, and the X/Y-direction coordinate axis can be selected at will.
The position of the laser coordinate system { L } origin relative to the tool coordinate system { T } can be described as
The pose of the Z-axis of the laser coordinate system { L } relative to the tool coordinate system { T } can be described as
In the measurement, the laser sensor measures the reading of l, and the position of the laser measuring point relative to the machine coordinate system { M }, thereby M P is represented as
Wherein,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 the machine tool spindle. Equation (8) is a kinematic model of the laser measurement point taking into account the positioning angle of the machine tool spindle.
Expanding equation (8) into a linear system of equations, expressed as
AX＝B (14)
Wherein x= (δx, δy, δz, δi, δj, δk) T Is 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 matrix, and can be represented by the coordinates of each rotating shaft of a five-axis numerical control machine tool and the 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 each translational axis coordinate and measuring point coordinate of a five-axis numerical control machine tool.
The equation set contains 6 unknown numbers of δx, δy, δz, δi, δj and δk, when the laser sensor is calibrated based on the reference plane, the reference plane with known positions needs to be measured under the state of more than 6 different machine tool pose states, so as to construct more than 6 linear equations, and the equation set is solved by an analysis or fitting method.
S2: calibration tool with datum plane
And installing a calibration tool with a reference plane, ensuring that a reference plane equation is a known quantity under a machining coordinate system, and expressing as F (x, y, z) =0.
Further, since the kinematic model of the laser measurement point in the formula (8) considers the positioning angle of the spindle of the machine tool, when the rotation axis of the machine tool moves so that the spindle axis is not perpendicular to the calibration plane, the spindle rotation causes the measurement data of the laser sensor to change for the XY plane or the parallel plane thereof. Therefore, the reference plane can be perpendicular to the spindle axis 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 ensured 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 the spindle component and the workbench is reduced.
S3: mounting a laser sensor and setting a virtual blade length
The laser sensor is arranged on the spindle of the five-axis numerical control machine tool through the tool handle, the laser sensor rays are along the axial direction of the spindle of the five-axis numerical control machine tool, and the laser sensor can rotate along the spindle of the random machine tool. Setting a virtual cutter length, wherein the virtual cutter length value is the projection length of the distance from the end face 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 tool tip point is the origin of the tool coordinate system { T }.
Due to the deviation of the mounting pose of the laser sensor, the reference zero point of the laser sensor is inevitably deviated from the position of the virtual tool tip point, and the laser emission axis is also deviated from the direction of the main shaft of the machine tool, as shown in fig. 2.
S4: the laser sensor measures reference planes with different poses, records the coordinates of each axis of the five-axis numerical control machine tool under the current measured pose and the measured value of the laser sensor, and forms a linear equation set taking the installation position and the pose of the laser sensor as unknown numbers
Measuring a reference plane with n different positions and attitudes by a five-axis numerical control machine motion control laser sensor, wherein n is not less than the dimension of an unknown number X, and recording the motion quantity (X i ,Y i ,Z i ,M i ,N i ,S i ) And laser sensor measurement l i Where i=1, 2, …, n; n is more than or equal to 6.
Reconstructing n linear equations according to the recorded coordinates of each axis of the five-axis numerical control machine tool under each measuring pose and the measured value of the laser sensor by combining a reference plane equation F (x, y, z) =0 and a linear equation set AX=B to form an n-order linear equation set
Wherein the unknown number X is the expression of the mounting position (delta X, delta y, delta z) and the posture (delta i, delta j, delta k) of the laser sensor, and is a 6-dimensional column vector and a coefficient matrixThe expression of the measurement reading of the laser sensor and the coordinates of each rotation axis of the five-axis numerical control machine tool is an n multiplied by 6 matrix, and a constant term is +.>The expression of each translational axis coordinate and measuring point coordinate of the five-axis numerical control machine tool is an n-dimensional column vector.
Specifically, different positions and postures of the machine tool can meet the following conditions:
(1) Ensuring that the reference plane is within the effective travel of the laser sensor.
(2) Ensuring construction coefficient matrixRank meets->Matrix->Condition number of->As small as possible.
Furthermore, the calibration operation can be selectively performed near the zero position of the rotating shaft of the machine tool, the risk of interference between the main shaft component of the machine tool and the workbench caused by overlarge motion quantity 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
Solving the linear equation set constructed in the S4, and calculating to obtain X= (δx, δy, δz, δi, δj, δk) T And the laser sensor mounting position and gesture recognition are realized.
Specifically, according to the number of measurement points, the mounting pose of the laser sensor can be identified according to the following method:
s51: when n=6, the matrix a is a 6-order square matrix, which can be directly solved by adopting an analytic method;
s52: when n >6, matrix A is a long matrix of rank 6, which can be solved using least squares fitting.
Example 2
The embodiment discloses a point laser sensor mounting pose calibration method suitable for an AC double-swing-head structure five-axis numerical control machine tool, and the flow is shown in figure 1. As an embodiment of the present application, the following are specific embodiments and considerations:
s1: establishing a kinematic model of a laser measuring point
For an AC double-swing machine tool, when the RTCP function is turned on, the pose of the tool coordinate system { T } relative to the machine tool coordinate system { M } can be expressed as
Wherein the method comprises the steps of
Wherein, (X, Y, Z, A, C) represents the coordinates of each axis of the machine tool under the RTCP function, 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 } with respect to the tool coordinate system { T } can be described asThe pose of the laser axis vector with respect to the tool coordinate system can be described as +.>Then there is
In measurement, when the length measured by the laser sensor is denoted as l, the position of the laser measurement point with respect to the tool coordinate system { T }, is
Position converted to machine tool coordinate system { M } according to equation (16) M P is represented as
Wherein,
the formula (24) is a kinematic model of a measuring point of a laser sensor arranged on a five-axis numerical control machine tool with an AC double-swing structure.
Expanding equation (24) into a system of linear equations, expressed as
AX＝B (25)
Wherein A is a coefficient matrix of a linear equation set
In the above-mentioned method, the step of,
x is the unknown of the system of linear equations
X＝(δx,δy,δz,δi,δj,δk) T
B is a constant term of a linear equation set
B＝(x-X,y-Y,z-Z) T
From equation (25), it can be seen that the system of equations contains 6 unknowns for δx, δy, δz, δi, δj, and δk. When a laser sensor is calibrated by adopting a certain reference plane, the reference plane with known position is required to be measured under the state of more than 6 different machine tool pose, more than 6 linear equations are constructed, and an equation set is solved by an analysis or fitting method.
S2: calibration fixture with one datum plane
For an AC double-swing machine tool, the spindle axis is parallel to the Z axis in the initial position. In order to reduce the difficulty of tool installation 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 a reference plane equation at the moment is z=0.
S3: mounting a laser sensor and setting a virtual blade length
The laser sensor is arranged on the spindle of the five-axis numerical control machine tool through the tool handle, the laser sensor rays are along the axial direction of the spindle of the five-axis numerical control machine tool, and the laser sensor can rotate along the spindle of the random machine tool. Setting a virtual cutter length, wherein the virtual cutter length value is the projection length of the distance from the end face 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 tool tip point is the origin of the tool coordinate system { T }. Due to the deviation of the mounting pose of the laser sensor, the reference zero point of the laser sensor is inevitably deviated from the position of the virtual tool tip point, and the laser emission axis is also deviated from the direction of the main shaft of the machine tool, as shown in fig. 2.
S41: the laser sensor measures the reference plane with 6 different poses, and the motion quantity and the laser sensor measured value are recorded
For the reference plane z=0, when any point on the plane is measured using the laser sensor, the Z-direction coordinates of the measurement point are all 0. By combining (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 δx, δy, δz, δi, δj, and δk6 unknowns requires that the following 2 conditions be satisfied:
(1) For an actual laser sensor installation scene, the angle 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 machine tool A axis is selected for measurement, so that the interference risk of a machine tool spindle component and a workbench is avoided, and the operability of calibration operation is improved;
(2) In at least 6 different machine tool positions (X i ,Y i ,Z i ,A i ,C i ,S i ) (i=1, 2, …, n; n is more than or equal to 6), measuring a reference plane, and recording the corresponding reading l of the laser displacement sensor i ,(i＝1,2,…,n；n≥6)。
Specifically, the measurements are taken in this example using 6 different positions and attitudes, as shown in FIGS. 3-8. The machine tool starts an RTCP function, controls the machine tool to move to the position of x=0, y=0, z=0, a=0, c= 0,S =0, and comprises the following steps:
s41-1: control the machine to move to the z=0, a= 0,S =0 position, record the laser sensor reading as l 00 ；
S41-2: the machine tool is controlled to move to a position of Z= delta Z, A = 0,S = 0, and the reading of the laser sensor is recorded as l 0z ；
S41-3: the machine tool is controlled to move to a position Z=0, A= [ delta ] A and S=0, and the reading of the laser sensor is recorded as l a0 ；
S41-4: control deviceThe machine tool moves to a position of Z= delta Z, A= delta A and S = 0, and the reading of the laser sensor is recorded as l ay ；
S41-5: the machine tool is controlled to move to a position z=0, a= Δa, s= Δs, and the laser sensor reading is recorded as l s0 ；
S41-6: the machine tool is controlled to move to the positions of Z= delta Z, A= delta A and S= delta S, and the reading of the laser sensor is recorded as l sz 。
According to the coordinates 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
Wherein,coefficient matrix which is a system of linear equations
In the above
X is the unknown of the system of linear equations
X＝(δx,δy,δz,δi,δj,δk) T
Constant term being a system of linear equations
S51: laser sensor mounting location and gesture recognition
The laser sensor mounting position and posture are calculated from the machine tool movement amounts and laser sensor measurement values recorded by the machine tool at different positions and postures in S41. Since the number of measurement points n=6, the solution can be directly achieved by an analytical method. Specifically, the method comprises the following steps:
s51-1: calculating an attitude deviation component δk and a position deviation component δz
S51-2: calculating an attitude deviation component δj and a position deviation component δy
Wherein,
s51-3: calculating an attitude deviation component δi and a position deviation component δx
Wherein,
the actual installation position and the actual attitude of the laser sensor can be completely obtained.
Example 3
The difference from example 2 is that: in the step S4, more than 6 different poses are adopted to measure the reference plane, and in the step S5, the least square fitting method is adopted to identify the mounting pose of the laser sensor. The specific implementation steps are as follows:
s42: the laser sensor measures the reference plane with more than 6 different poses, and the motion quantity and the laser sensor measured value are recorded
The movement of the five-axis numerical control machine tool and the measured value of the laser sensor are recorded under each measuring position and each measuring posture by controlling the laser sensor to measure the reference plane at different positions and postures through the movement of the five-axis numerical control machine tool.
Specifically, more than 6 different positions and attitudes are used for measurement, and machine coordinate value data (X i ,Y i ,Z i ,A i ,C i ,S i ) And corresponding laser displacement sensor reading l i Where i=1, 2, …, n; n is n>6. In order to ensure that the laser sensor can effectively measure the reference plane, the swing angle of the axis A of the machine tool is positioned near the 0-degree position for measurement.
According to the coordinates 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
S52: laser sensor mounting location and gesture recognition
Constructing a laser sensor mounting location and gesture recognition objective function
min f(δx,δy,δz,δi,δj,δk) (29)
Wherein,
the actual installation position and posture of the laser sensor can be completely obtained by the least square method (29).
Claims (4)
1. A method for calibrating the installation pose of a point laser sensor based on a plane is characterized by comprising the following steps: comprises the following steps of the method,
s1: according to the positioning angle of the main shaft of the machine tool, a kinematic model of a laser measuring point is established, and a linear equation set taking the installation position and the posture of the laser sensor as unknown numbers is formed;
s2: installing a calibration tool with a reference plane;
s3: installing a laser sensor and setting a virtual cutter length;
s4: the laser sensor measures reference planes with different poses, records the coordinates of each axis of the five-axis numerical control machine tool under the current measured pose and the measured value of the laser sensor, and forms a linear equation set taking the installation position and the pose of the laser sensor as unknown numbers;
s5: calculating the mounting position and the attitude of the laser sensor;
s1 specifically comprises the following steps: establishing a machining coordinate system { M } fixedly connected with a machine tool, wherein the origin of the machining coordinate system { M } is positioned at a machining coordinate offset point of the machine tool, and the coordinate axis direction is consistent with the absolute coordinate system of the machine tool; establishing a tool coordinate system { T } fixedly connected with a tool, wherein the origin of the tool coordinate system { T } is positioned at a tool point, and the coordinate axis direction is consistent with a machine tool coordinate system { M }; establishing a laser coordinate system { L } fixedly connected with a laser sensor, wherein the origin of the laser coordinate system { L } is positioned at a measurement reference zero point, a Z-direction coordinate axis is consistent with a laser emission axis, and X/Y-direction coordinate axes are arbitrarily selected;
the position of the laser coordinate system { L } origin relative to the tool coordinate system { T } is described as
The pose of the Z-axis of the laser coordinate system { L } relative to the tool coordinate system { T } is described as
In the measurement, the laser sensor measures the reading of l, and the position of the laser measuring point relative to the machine coordinate system { M }, thereby M P is represented as
Wherein,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 the machine tool spindle, and the formula (3) is a kinematic model of a laser measuring point considering the positioning angle of the machine tool spindle;
expanding equation (3) into a linear system of equations, expressed as
AX＝B (4)
Wherein x= (δx, δy, δz, δi, δj, δk) T Is 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, which is a 3 multiplied by 6 matrix, and is represented by the coordinates of each rotating shaft of a five-axis numerical control machine tool and the measurement readings of a laser sensor; b is a constant term of a linear equation set, is a 3-dimensional column vector, and is represented by each translational axis coordinate and measuring point coordinate of a five-axis numerical control machine tool;
the equation set contains 6 unknown numbers of δx, δy, δz, δi, δj and δk, when the laser sensor is calibrated based on a reference plane, the reference plane with known positions needs to be measured under the state of more than 6 different machine tool positions, so as to construct more than 6 linear equations, and the equation set is solved by an analysis or fitting method;
s3 specifically comprises the following steps: the laser sensor is arranged on the spindle of the five-axis numerical control machine tool through the tool handle, the laser sensor rays are along the axial direction of the spindle of the five-axis numerical control machine tool, and the laser sensor can rotate along the spindle of the random 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 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 tool point is the origin of the tool coordinate system { T };
s4 specifically comprises the following steps: measuring a reference plane by using a five-axis numerical control machine tool motion control laser sensor at n different positions and postures, wherein n is not smaller than the dimension of an unknown number X, and recording the motion quantity X of the five-axis numerical control machine tool at each measured position and posture i ,Y i ,Z i ,M i ,N i ,S i And laser sensor measurement l i Where i=1, 2, …, n; n is more than or equal to 6;
reconstructing n linear equations according to the recorded coordinates of each axis of the five-axis numerical control machine tool under each measuring pose and the measured value of the laser sensor by combining a reference plane equation F (x, y, z) =0 and a linear equation set AX=B to form an n-order linear equation set
Wherein the unknown number X is the expression of the mounting position (delta X, delta y, delta z) and the posture (delta i, delta j, delta k) of the laser sensor, and is a 6-dimensional column vector and a coefficient matrixThe expression of the measurement reading of the laser sensor and the coordinates of each rotation axis of the five-axis numerical control machine tool is an n multiplied by 6 matrix, and a constant term is +.>The expression of each translational axis coordinate and measuring point coordinate of the five-axis numerical control machine tool is an n-dimensional column vector;
the different positions and attitudes of the machine tool should meet the following conditions:
(1) Ensuring that the reference plane is located within the effective travel of the laser sensor;
(2) Ensuring construction coefficient matrixRank meets->
2. The method for calibrating the mounting pose of the plane-based point laser sensor according to claim 1, wherein the method comprises the following steps of:
s2 specifically comprises the following steps: installing a calibration tool with a reference plane, ensuring that a reference plane equation is a known quantity under a machining coordinate system, and expressing as F (x, y, z) =0; the reference plane is set to be perpendicular to the spindle axis of the five-axis numerical control machine tool, and the equation of the reference plane is ensured to be a known quantity.
3. The method for calibrating the mounting pose of the plane-based point laser sensor according to claim 1, wherein the method comprises the following steps of:
s5 specifically comprises the following steps: solving the linear equation set constructed in the S4, and calculating to obtain X= (δx, δy, δz, δi, δj, δk) T And the laser sensor mounting position and gesture recognition are realized.
4. The method for calibrating the mounting pose of the plane-based point laser sensor according to claim 3, wherein the method comprises the following steps of:
according to the number of measuring points, the mounting pose of the laser sensor is identified according to the following method:
s51: when n=6, the matrix A is a 6-order square matrix, and the method is adopted to directly solve;
s52: when n >6, matrix A is a long matrix with rank of 6, and is solved by using least square fitting.
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