CN114963988A - Light pen measuring system and method for high-precision large-range measurement - Google Patents

Abstract

The invention discloses an optical pen measuring system and an optical pen measuring method for high-precision large-range measurement, wherein the system comprises an industrial robot, a laser tracker and an optical pen measuring device; the laser tracker is placed on one side of the industrial robot, and the light pen measuring device is fixed on the upper surface of the industrial robot through the magnetic suction device; the light pen measuring device comprises a T-shaped light pen and a magnetic suction device; the magnetic suction device comprises a three-joint bracket and a magnetic suction base; the T-shaped light pen comprises a T-shaped frame, three target balls of the laser tracker, three magnetic bases, a measuring head and a force sensor. The invention can realize the measurement of the structure size and the positioning error of the industrial robot based on the optical pen measuring system, and effectively ensures the precision of the measured data by utilizing the advantages of large-range and high-precision measurement of the laser tracker.

Description

Light pen measuring system and method for high-precision large-range measurement

Technical Field

The invention belongs to the technical field of industrial robot detection, and particularly relates to an optical pen measuring system and an optical pen measuring method for high-precision large-range measurement.

Background

The industrial robot is widely applied to the high-end manufacturing fields such as aviation and aerospace by virtue of the advantages of high reliability, high precision, high efficiency and the like, and the requirements on the performance and precision of the industrial robot are gradually improved. At present, the repeated positioning precision of an industrial robot can reach 0.01mm, but the absolute positioning precision of the robot is still poorer and is only in millimeter level due to the influence of multiple aspects such as processing and assembling of parts. Along with the increase of the working time of the industrial robot, the repeated positioning precision and the absolute positioning precision of the industrial robot can be degraded in performance to different degrees.

The method for improving the precision performance of the industrial robot is to use a structure parameter measurement and error calibration technology, and the structure parameter measurement can directly measure parameters such as a structural part mounting hole, an external dimension and the like through high-precision equipment such as a visual three-dimensional scanning instrument, a three-coordinate measuring instrument and the like, so as to calculate the kinematic parameters of the robot. Current three-coordinate measuring machines are too portable and the accuracy of visual three-dimensional scanning is relatively poor.

The calibration technology of the industrial robot is divided into four basic steps of modeling, measuring, identifying and compensating. The measuring step is to accurately detect the tail end position and the attitude data of the robot through external measuring equipment, and is a key step for calibrating the good and bad effect. At present, the measurement of the pose of the tail end of a robot is mainly realized through high-precision equipment such as a laser tracker, a laser interferometer and the like, wherein the measurement precision of the laser tracker is 0.015mm, the measurement precision requirement can be met, but the pose measurement is realized through a common target ball, and the measurement cannot be applied to the measurement of the structure size. And a single target ball cannot realize the measurement of attitude data.

Therefore, the invention is urgently needed to design a measuring device and a measuring method, which can fully utilize the advantages of the measuring precision and the large-range measurement of the laser tracker and can be better applied to the measurement of the size and the pose of the industrial robot with high precision and large range.

Disclosure of Invention

The technical problem to be solved by the invention is to provide an optical pen measuring system and an optical pen measuring method for high-precision and large-range measurement aiming at the defects of the prior art, so that large-range and high-precision measurement of the structure size and the end pose error of an industrial robot can be realized, and the defects of the prior art in the detection of the structure size and the end pose of the industrial robot are overcome.

In order to achieve the technical purpose, the technical scheme adopted by the invention is as follows:

an optical pen measuring system for high-precision large-range measurement comprises an industrial robot, a laser tracker and an optical pen measuring device;

the laser tracker is placed on one side of the industrial robot, and the light pen measuring device is fixed on the upper surface of the industrial robot through the magnetic suction device;

the light pen measuring device comprises a T-shaped light pen and a magnetic suction device;

the magnetic suction device comprises a three-joint bracket and a magnetic suction base;

the T-shaped light pen is arranged at one end of the three-joint support, and the other end of the three-joint support is provided with the magnetic suction base;

each rotary joint of the three-joint support is fixed in position through a joint knob, and a knob is arranged on the magnetic suction base to control the magnetic suction device to be fixed in a designated position;

the T-shaped light pen comprises a T-shaped frame, three target balls of the laser tracker, three magnetic bases, a measuring head and a force sensor;

the three magnetic bases are distributed on the T-shaped frame in an isosceles triangle form, target balls of the three laser tracking instruments are adsorbed on the magnetic bases and are recorded as an upper left laser tracker target ball, an upper right laser tracker target ball and a lower laser tracker target ball according to the directions;

and a measuring head and a force sensor are arranged at the target ball end of the laser tracker under the T-shaped frame.

The structure size measuring method based on the optical pen measuring system comprises the following steps:

the method comprises the following steps that (1) a laser tracker is placed on one side of an industrial robot, and a light pen measuring device is fixed on the upper surface of the industrial robot through a magnetic suction base;

adjusting the three-joint support to enable the measuring head to be attached to the inner edge or the outer edge of the point to be measured, ensuring that target balls of the three laser trackers are all within the visual angle range of the laser trackers, and finally adjusting joint knobs of the three-joint support to fix joint positions and keeping the state of the optical pen measuring device unchanged in the measuring process;

step (3) measuring and collecting target balls of three laser trackers by using the laser trackers respectively in a laser tracker measurement coordinate system F ₁ Spatial position of lower, respectively denoted by p ₁ ，p ₂ ，p ₃ The measurement sequence is sequentially an upper left laser tracker target ball, an upper right laser tracker target ball and a lower laser tracker target ball;

step (4) with p ₁ The point is used as the origin of the coordinate system of the light pen measuring device, and is p ₁ ，p ₂ A unit vector n in the direction of the connecting line of the points is the X-axis direction;

with p ₁ ，p ₂ ，p ₃ A unit vector a of the formed plane normal vector is in the Z-axis direction, and a unit direction vector o of the Y-axis is obtained by vector cross-multiplication calculation of the X-axis and the Y-axis;

step (5) obtaining a coordinate system F of the optical pen measuring device according to the step (4) ₂ Measuring coordinate system F in laser tracker ₁ The pose matrix H at this point is as follows:

step (6), obtaining the coordinate system F of the central point of the measuring head in the light pen measuring device ₂ The central point of the measuring head is in a measuring coordinate system F of the laser tracker ₁ The following positions are:

step (7),Measuring a coordinate system F of the central point of the measuring head obtained in the step (6) in the laser tracker ₁ And compensating the lower position to obtain the position of the contact point of the measuring head of the optical pen measuring device and the structure to be measured.

In order to optimize the technical scheme, the specific measures adopted further comprise:

the step (7) includes:

step (7-1): fixing the optical pen measuring device on the upper surface of the industrial robot through the magnetic suction device, and adjusting the three-joint support to enable the measuring head to be attached to the inner edge or the outer edge of the point to be measured;

step (7-2): obtaining a position vector P of the measuring head central point in the step (6), and defining a system measuring head deviation model by taking Q as a position vector of an actual contact point;

step (7-3): obtaining a vector F of the contact force through the output of the force sensor, and determining a direction vector n of the contact point Q and the measuring head central point P;

step (7-4): substituting the direction vector n into the system measuring head deviation model to obtain the system measuring head deviation, namely a compensation vector of measuring head errors, and compensating errors generated by the optical pen measuring device.

The step (7-2) defines the system gauge head deviation model as the following formula:

p _error ＝R*n (1)

wherein p is _error Is the compensation vector of the error, R is the average radius of the stylus, and n is the direction vector of the contact point Q and the stylus center point P.

The step (7-3) determines that the direction vector n of the contact point Q and the measuring head center point P is as follows:

where F is the vector of the three-dimensional linear force read by the force sensor.

The method for measuring the positioning error of the industrial robot based on the optical pen measuring system comprises the following steps:

step 1, placing a laser tracker on one side of an industrial robot, and directly fixing a T-shaped light pen on the upper surface of the industrial robot through screws;

step 2, respectively measuring and collecting target balls of three laser trackers in a laser tracker measurement coordinate system F by using the laser trackers ₁ Spatial position of lower, respectively denoted by p ₁ ，p ₂ ，p ₃ The measurement sequence is sequentially an upper left laser tracker target ball, an upper right laser tracker target ball and a lower laser tracker target ball;

step 3, with p ₁ The point is used as the origin of the coordinate system of the light pen measuring device, and is p ₁ ，p ₂ A unit vector n in the direction of the connecting line of the points is the X-axis direction; with p ₁ ，p ₂ ，p ₃ A unit vector a of the formed plane normal vector is in the Z-axis direction, and a unit direction vector o of the Y-axis is obtained by vector cross-multiplication calculation of the X-axis and the Y-axis;

step 4, obtaining a T-shaped light pen coordinate system F based on the step 3 ₃ Measuring coordinate system F in laser tracker ₁ The pose matrix H at this point is as follows:

step 5, knowing a default coordinate system F of the industrial robot ₄ Coordinate system F of T-shaped light pen ₃ Is H ₁ Thus the industrial robot defaults to the coordinate system F ₄ Measuring coordinate system F in laser tracker ₁ Pose matrix H of ₂ Comprises the following steps:

and 6, controlling the industrial robot to move to a certain point in the space, and recording the position and posture in the industrial robot controller as H _N And indicating the command pose of the industrial robot, and setting the pose error of the industrial robot to be equal to H _N -H ₂ 。

The invention has the following beneficial effects:

the invention can realize the measurement of the structure size and the positioning error of the industrial robot based on the optical pen measuring system, and effectively ensures the precision of the measured data by utilizing the advantages of large-range and high-precision measurement of the laser tracker.

Drawings

FIG. 1 is a diagram of a light pen measurement system of the present invention;

FIG. 2 is a block diagram of a light pen measuring device of the present invention;

FIG. 3 is an assembly view of the T-shaped light pen of the present invention;

FIG. 4 is a structural view of a T-shaped light pen of the present invention

FIG. 5 is a view showing the structure of the magnetic attraction device of the present invention;

FIG. 6 is a schematic illustration of the positioning error measurement of the present invention;

1-light pen measuring device, 2-industrial robot, 3-laser tracker, 101-T type light pen, 102-magnetic attraction device, 201-T type frame, 202-measuring head, 203-upper right laser tracker target ball, 204-lower laser tracker target ball, 205-upper left laser tracker target ball, 206-first magnetic base, 207-second magnetic base, 208-third magnetic base, 209-force sensor, 301-magnetic attraction base, 302-three joint support, 303-first joint knob, 304-second joint knob, 305-third joint knob.

Detailed Description

Embodiments of the present invention are described in further detail below with reference to the accompanying drawings.

As shown in fig. 1 to 5, the optical pen measuring system for high-precision and wide-range measurement of the present invention mainly includes three parts, i.e., an industrial robot 2, a laser tracker 3, and an optical pen measuring device 1.

Wherein the optical pen measuring device 1 can be fixed on the surface of the industrial robot 2 through the magnetic attraction device 102 of the optical pen measuring device.

The light pen measuring device 1 mainly comprises two parts, namely a T-shaped light pen 101 and a magnetic attraction device 102.

Wherein the T-shaped light pen 101 mainly comprises a T-shaped frame 201; target balls for three laser trackers: an upper left laser tracker target ball 205, an upper right laser tracker target ball 203, and a lower laser tracker target ball 204; a first magnetic base 206, a second magnetic base 207, a third magnetic base 208; and a stylus 202 and force sensor 209.

The first magnetic base 206, the second magnetic base 207 and the third magnetic base 208 are distributed on the T-shaped frame 101 in an isosceles triangle shape, and the upper left laser tracker target ball 205, the upper right laser tracker target ball 203 and the lower laser tracker target ball 204 are adsorbed on the first magnetic base 206, the second magnetic base 207 and the third magnetic base 208.

The magnetic attraction device 102 mainly comprises a three-joint support 302 and a magnetic attraction base 301, each rotary joint of the three-joint support 302 can be fixed in position through a first joint knob 303, a second joint knob 304 and a third joint knob 305, the T-shaped light pen 101 is installed at one end of the three-joint support 302, the magnetic attraction base 301 is installed at the other end of the three-joint support 302, and the magnetic attraction device 102 can be controlled to be fixed at a specified position by controlling the knobs on the magnetic attraction base 301.

Based on the light pen measuring system, the method for realizing the structure size measurement comprises the following steps:

step (1), placing a laser tracker 3 at one side of an industrial robot 2, and fixing an optical pen measuring device 1 on the upper surface of the industrial robot 2 through a magnetic suction base 301;

step (2), adjusting the three-joint support 302 to enable the measuring head 202 of the optical pen measuring device 1 to be attached to the inner edge or the outer edge of a point to be measured, ensuring that the three target balls 203, 204 and 205 of the laser tracker on the optical pen measuring device 1 are all within the visual angle range of the laser tracker 3, and finally adjusting the first joint knob 303, the second joint knob 304 and the third joint knob 305 of the three-joint support 302 to fix the joint positions and keeping the state of the optical pen measuring device 1 unchanged in the measuring process;

step (3) measuring and collecting target balls of three laser trackers in the light pen measuring device 1 in a laser tracker measuring coordinate system F by using the laser tracker 3 ₁ Spatial position of lower, respectively denoted by p ₁ ，p ₂ ，p ₃ The measurement sequence is sequentially an upper left laser tracker target ball 205, an upper right laser tracker target ball 203 and a lower laser tracker target ball 204;

step (4) with p ₁ The point is taken as the origin of the coordinate system of the light pen measuring device 1, in p ₁ ，p ₂ The unit vector n in the direction of the line connecting the dots is the X-axis direction. With p ₁ ，p ₂ ，p ₃ The unit vector a of the plane normal vector is the Z-axis direction, and the unit direction vector o of the Y-axis is calculated by cross-multiplication of the vectors of the X-axis and the Y-axis.

Step (5), obtaining a coordinate system F of the optical pen measuring device according to the information ₂ Measuring coordinate system F in laser tracker ₁ The pose matrix H at this point is as follows:

step (6), the central point of the measuring head 202 in the optical pen measuring device 1 is in the coordinate system F of the optical pen measuring device ₂ P, the center point of the stylus 202 is in the laser tracker measurement coordinate system F ₁ The following positions are:

in the step (7), since the position vector obtained in the step (6) is only the center point position of the probe 202, and is not the contact point position of the probe 202 of the optical pen measuring device 1 and the structure to be measured, the following steps are required to compensate for further improvement of the measurement accuracy.

Step (7-1): the optical pen measuring device 1 is fixed on the upper surface of the industrial robot 2 through the magnetic suction device 301, and the three-joint support 302 is adjusted so that the measuring head 202 of the optical pen measuring device 1 is abutted against the inner edge or the outer edge of the point to be measured. Step (7-2): obtaining the position vector P of the center point of the measuring head 202 by the step (6), and taking Q as the actual contact point

Defining a system stylus deflection model as follows:

p _error ＝R*n (1)

wherein p is _error Is the compensation vector for the error of the stylus 202, and R is the average of the stylus 202The radius, n, is the direction vector of the contact point Q and the center point P of the stylus 202.

Step (7-3): the vector F of the contact force is derived from the output of the force sensor 209, from which the contact point Q and the measurement are determined

The direction vector n of the center point P of the head 202 is given by:

where F is the vector of the three-dimensional linear force read by the force sensor 209.

Step (7-4): the error generated by the optical pen measuring apparatus 1 can be compensated by obtaining a compensation vector for the error of the stylus 202 by substituting equation (2) into equation (1).

As shown in fig. 6, the method for measuring the positioning error of the industrial robot 2 based on the T-shaped light pen 101 in the light pen measuring device 1 is also as follows:

step 1, placing a laser tracker 3 at one side of an industrial robot 2, and directly fixing a T-shaped light pen 101 on the upper surface of the industrial robot 2 through screws;

step 2, respectively measuring and collecting the spatial positions of an upper left laser tracker target ball 205, an upper right laser tracker target ball 203 and a lower laser tracker target ball 204 in the T-shaped light pen 101 under a laser tracker measurement coordinate system F1 by using the laser tracker 3, and respectively recording the spatial positions as p ₁ ，p ₂ ，p ₃ The measurement sequence is sequentially an upper left laser tracker target ball 205, an upper right laser tracker target ball 203 and a lower laser tracker target ball 204;

step 3, with p ₁ The point is taken as the origin of the coordinate system of the light pen measuring device 1, in p ₁ ，p ₂ The unit vector n in the direction of the line connecting the dots is the X-axis direction. With p ₁ ，p ₂ ，p ₃ The unit vector a of the plane normal vector is the Z-axis direction, and the unit direction vector o of the Y-axis is calculated by cross-multiplication of the vectors of the X-axis and the Y-axis.

Step 4, obtaining a T-shaped light pen coordinate system F according to the information ₃ Measuring coordinate system F in laser tracker ₁ The pose matrix H below is as follows:

step 5, knowing a default coordinate system F of the industrial robot ₄ Coordinate system F of T-shaped light pen ₃ Is H ₁ Thus the industrial robot defaults to the coordinate system F ₄ Measuring coordinate system F in laser tracker ₁ Pose matrix H of ₂ As follows:

and 6, controlling the industrial robot to move to a certain point in the space, and recording the position and posture in the industrial robot controller as H _N And indicating the command pose of the industrial robot, and setting the pose error of the industrial robot to be equal to H _N -H ₂ 。

I.e. the default coordinate system F of the industrial robot measured with the device of the invention ₄ Measuring coordinate system F in laser tracker ₁ Pose matrix H of ₂ Comprises the following steps:

therefore, the pose error of the industrial robot is Δ H ═ H _N -H ₂ And the position error of the industrial robot can be measured.

The device can realize the measurement of the structure size and the positioning error of the industrial robot, and effectively ensures the precision of the measured data by utilizing the advantages of large-range and high-precision measurement of the laser tracker.

The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above-mentioned embodiments, and all technical solutions belonging to the idea of the present invention belong to the protection scope of the present invention. It should be noted that modifications and embellishments within the scope of the invention may be made by those skilled in the art without departing from the principle of the invention.

Claims (6)

1. An optical pen measuring system for high-precision large-range measurement is characterized by comprising an industrial robot, a laser tracker and an optical pen measuring device;

the laser tracker is placed on one side of the industrial robot, and the light pen measuring device is fixed on the upper surface of the industrial robot;

the light pen measuring device comprises a T-shaped light pen and a magnetic suction device;

the magnetic suction device comprises a three-joint bracket and a magnetic suction base;

the T-shaped light pen is arranged at one end of the three-joint support, and the other end of the three-joint support is provided with the magnetic suction base;

each rotary joint of the three-joint support is fixed in position through a joint knob, and a knob is arranged on the magnetic suction base to control the magnetic suction device to be fixed in a designated position;

the T-shaped light pen comprises a T-shaped frame, three target balls of the laser tracker, three magnetic bases, a measuring head and a force sensor;

the three magnetic bases are distributed on the T-shaped frame in an isosceles triangle form, target balls of the three laser tracking instruments are adsorbed on the magnetic bases and are recorded as an upper left laser tracker target ball, an upper right laser tracker target ball and a lower laser tracker target ball according to the directions;

and a measuring head and a force sensor are arranged at the target ball end of the laser tracker under the T-shaped frame.

2. The method for measuring the dimension of a structure by using the optical pen measuring system according to claim 1, comprising the following steps:

the method comprises the following steps that (1) a laser tracker is placed on one side of an industrial robot, and a light pen measuring device is fixed on the upper surface of the industrial robot through a magnetic suction base;

adjusting the three-joint support to enable the measuring head to be attached to the inner edge or the outer edge of the point to be measured, ensuring that target balls of the three laser trackers are all within the visual angle range of the laser trackers, and finally adjusting joint knobs of the three-joint support to fix joint positions and keeping the state of the optical pen measuring device unchanged in the measuring process;

step (3) measuring and collecting target balls of three laser trackers by using the laser trackers respectively in a laser tracker measurement coordinate system F ₁ Spatial position of lower, respectively denoted by p ₁ ，p ₂ ，p ₃ The measurement sequence is sequentially a left upper laser tracker target ball, a right upper laser tracker target ball and a lower laser tracker target ball;

step (4) with p ₁ The point is used as the origin of the coordinate system of the light pen measuring device, and is p ₁ ，p ₂ A unit vector n in the direction of the connecting line of the points is the X-axis direction;

with p ₁ ，p ₂ ，p ₃ A unit vector a of the formed plane normal vector is in the Z-axis direction, and a unit direction vector o of the Y-axis is obtained by vector cross-multiplication calculation of the X-axis and the Y-axis;

step (5) obtaining a coordinate system F of the optical pen measuring device according to the step (4) ₂ Measuring coordinate system F in laser tracker ₁ The pose matrix H at this point is as follows:

step (6), obtaining the coordinate system F of the central point of the measuring head in the light pen measuring device ₂ The central point of the measuring head is in a measuring coordinate system F of the laser tracker ₁ The following positions are:

step (7) of measuring the central point of the measuring head obtained in the step (6) in a measuring coordinate system F of the laser tracker ₁ And compensating the lower position to obtain the position of the contact point of the measuring head of the optical pen measuring device and the structure to be measured.

3. The structure dimension measuring method according to claim 2, wherein the step (7) includes:

step (7-1): fixing the optical pen measuring device on the upper surface of the industrial robot through the magnetic suction device, and adjusting the three-joint support to enable the measuring head to be attached to the inner edge or the outer edge of the point to be measured;

step (7-2): obtaining a position vector P of the measuring head central point in the step (6), and defining a system measuring head deviation model by taking Q as a position vector of an actual contact point;

step (7-3): obtaining a vector F of the contact force through the output of the force sensor, and determining a direction vector n of the contact point Q and the measuring head central point P;

step (7-4): substituting the direction vector n into the system measuring head deviation model to obtain the system measuring head deviation, namely a compensation vector of measuring head errors, and compensating errors generated by the optical pen measuring device.

4. A structure dimension measuring method according to claim 3, wherein said step (7-2) defines a system gauge head deviation model as follows:

p _error ＝R*n (1)

wherein p is _error Is the compensation vector of the error, R is the average radius of the stylus, and n is the direction vector of the contact point Q and the stylus center point P.

5. The structure dimension measuring method according to claim 4, wherein the step (7-3) determines the direction vector n of the contact point Q and the gauge head center point P as follows:

where F is the vector of the three-dimensional linear force read by the force sensor.

6. An industrial robot positioning error measuring method implemented by the optical pen measuring system according to claim 2, characterized by comprising the steps of:

step 1, placing a laser tracker on one side of an industrial robot, and directly fixing a T-shaped light pen on the upper surface of the industrial robot through screws;

step 2, respectively measuring and collecting target balls of three laser trackers by using the laser trackers in a laser tracker measurement coordinate system F ₁ Spatial position of lower, respectively denoted by p ₁ ，p ₂ ，p ₃ The measurement sequence is sequentially an upper left laser tracker target ball, an upper right laser tracker target ball and a lower laser tracker target ball;

step 3, with p ₁ The point is used as the origin of the coordinate system of the light pen measuring device, and is p ₁ ，p ₂ A unit vector n in the direction of the connecting line of the points is the X-axis direction; with p ₁ ，p ₂ ，p ₃ A unit vector a of the formed plane normal vector is in the Z-axis direction, and a unit direction vector o of the Y-axis is obtained by vector cross-multiplication calculation of the X-axis and the Y-axis;

step 4, obtaining a T-shaped light pen coordinate system F based on the step 3 ₃ Measuring coordinate system F in laser tracker ₁ The pose matrix H at this point is as follows:

step 5, knowing a default coordinate system F of the industrial robot ₄ Coordinate system F of T-shaped light pen ₃ Is H ₁ Thus the industrial robot defaults to the coordinate system F ₄ Measuring coordinate system F in laser tracker ₁ Pose matrix H of ₂ Comprises the following steps:

and 6, controlling the industrial robot to move to a certain point in the space, and recording the position and posture in the industrial robot controller as H _N And indicating the command pose of the industrial robot, and setting the pose error of the industrial robot to be equal to H _N -H ₂ 。

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