KR100225882B1 - Method and measuring jig for tuning tcp of laser vision sensor mounted in articulated robot - Google Patents

Abstract

The present invention relates to a method for correcting the position and attitude of a sensor attached to an industrial robot and a measuring jig used therein. When trying to obtain the information necessary to use the robot by using the 3D coordinate values of the linear laser vision sensor, it is essential to find out the relative transformation relationship between the coordinate system of the end of the robot and the coordinate system of the sensor. In the conventional method, when attaching a tool or sensor to the end of a robot, the transformation of the coordinate system is found by contacting the tool or sensor with a known contact point. This method increases the risk depending on the precision of the operation of the robot and the contact of the tool or sensor to the contact point. In addition, this work must be done with great sophistication, which is very difficult for the operator of the production line to operate.

In the present invention, the transformation of the relative coordinate system between the robot and the linear laser vision sensor is simply moved four times using a specific measuring jig, the coordinate point of the measuring jig is measured using a linear laser vision sensor, and the coordinate point is presented above. The relative transformation between the coordinate system of the robot tip and the coordinate system of the laser vision sensor is found through the transformation of one coordinate system. The proposed method not only solves all the difficulties caused by the existing methods, but also ensures the simplicity and accuracy of operation, and is very convenient and useful in an automated process using a linear laser sensor attached to a robot.

Description

Position and posture correction method of sensor attached to industrial robot and measuring jig used

The present invention relates to a method and apparatus for correcting the position and attitude of a sensor attached to an industrial robot.

In general, in order to replace human work, industrial robots perform automation work using industrial robots. Since industrial robots can repeat the positions and postures taught once within the accuracy allowed by the robots, these functions are increasingly needed in production lines that require simple repetitive tasks.

In order to perform this automated task, the industrial robot has to receive the position and posture information about the work path in advance.

That is, the accuracy of the working path is primarily determined by the coordinate system of the industrial robot itself in the work by the industrial robot. Even if the coordinate system of the industrial robot itself is known, the tool or sensor mounted on the end of the industrial robot (usually 6 axes) If you do not know the exact position and position of the will not be able to perform the correct operation.

Most industrial robots use the information attached to the robot to move the robot to obtain the necessary posture and position of the work path. But this is a very difficult task.

Therefore, in recent years, a lot of methods have been carried out by attaching sensors to the end of the robot (usually 6 axes) to measure the position and posture of the current robot to obtain information about the robot's processing path required for actual work.

What is needed at this time is a method of converting the coordinate system of the tip of the robot and the coordinate system of the sensor proposed in the present patent. Only when there is a method of converting the coordinate system can the sensor's measurement data be converted into the robot's reference coordinate system, and the robot's position and posture data can be combined with the sensor's data.

When attaching a tool or a sensor to the end (6 axis) of the conventional industrial robot was calculated by moving the robot by hand to know the transformation of the coordinate system between each other. In this conventional method, when attaching a tool or sensor to the end of the robot, a known contact point is used to contact the tool or sensor therein to find the transformation relationship of the coordinate system. This method increases the risk depending on the precision of the operation of the robot and the contact of the tool or sensor to the contact point. In addition, this work must be done with great sophistication, which is very difficult for the operator of the production line to operate. Therefore, in order to use sensor data more easily, a module that automatically converts coordinates is necessary.

It is an object of the present invention to provide a method and apparatus for correcting the position and attitude of a sensor attached to an industrial robot to easily, easily and accurately correct the position and attitude of a tool or sensor attached to the end of an industrial robot.

Another object of the present invention is to eliminate the risk of contacting a tool or sensor with a contact point.

1 is an explanatory diagram showing the specification of a linear laser vision sensor used in the present invention.

Figure 2a is a perspective view of the measuring jig used in the present invention.

Figure 2b is a plan view of the measuring jig used in the present invention.

2C is a cross-sectional view taken along the line A-A of FIG. 2B.

3 is a relationship diagram between a robot and a sensor coordinate system.

Figure 4 is a relationship diagram between the laser line and the measuring jig for explaining the process of obtaining the translational motion value of the sensor.

** Description of Symbols for Important Parts of Drawings **

10: linear laser vision sensor 20: measuring jig

21: semi-cylindrical groove 21a: edge

22: semi-conical groove 22a: edge

23,24: vertical axis 28: reference line

In order to achieve the object of the present invention, the circumferential groove and the semi-conical groove are formed at both ends of the industrial robot at the stand-off position by a predetermined distance from the linear laser vision sensor and have both side edges between the upper surface and the longitudinal axis at the bottom. Disposing a measuring jig having a reference line extending in a width direction on an upper surface at a boundary between the circumferential groove and the semi-conical groove; Irradiating a laser line of a linear laser vision sensor to the reference line to measure a point at which the laser line intersects the two edges and the longitudinal axis; Obtaining an incident angle (theta) of the laser line by comparing the area of the triangle by three points in the measuring step with the predetermined area of the measuring jig; Obtaining a translational motion value trans (S) of three different sensors by repeating the process of obtaining the relative coordinate system of the sensor by giving only the translational motion to the robot three times; Obtaining a rotational motion matrix Rot between the robot and the sensor by Equation 7 described below using translational motion values trans (R) of three robots which are already known during translational motion of the robot; Giving the robot a translational motion and a rotational motion to obtain a relative translational value trans (S) of the sensor; Equation 8 to be described later by using the translational motion value trans (S) of the sensor and the translational motion value trans (R) of the robot, the relative rotational motion value Rot (R) of the robot, and the rotational motion value Rot between the robot and the sensor. There is provided a method for correcting the position and posture of the sensor attached to the industrial robot, characterized in that it comprises ;;

In addition, the upper surface of the jig body formed in a rectangular size having a predetermined thickness in order to achieve the object of the present invention is formed to be connected to a semi-cylindrical groove 21 having a semi-cylindrical surface, a semi-conical groove having a semi-conical surface, A longitudinal axis is continuously formed at the center line portion of the semi-cylindrical groove 21 and the semi-conical groove so that the pair of edges and the longitudinal axis where the semi-cylindrical groove 21 and the upper surface meet form three parallel lines. The pair of edges where the upper surface meets is provided with a measuring jig for correcting the position and attitude of the sensor attached to the industrial robot, characterized in that configured to be bisected by the longitudinal axis.

The upper surface of the jig body is formed with a rectangular outline forming a semi-cylindrical groove 21 and a semi-conical groove circumscribed, the reference line is formed in the width direction on the boundary line of the semi-cylindrical groove 21 and the semi-conical groove.

Hereinafter, the position and attitude correction method and the device of the sensor attached to the industrial robot according to the present invention will be described in detail according to the embodiment shown in the accompanying drawings.

Figure 1 is an explanatory view showing the characteristics of the linear laser vision sensor used in the present invention, Figure 2a is a perspective view of the measuring jig used in the present invention, Figure 2b is a plan view of the measuring jig used in the present invention, Figure 2c is a view of Figure 2b AA line sectional drawing, FIG. 3 is a coordinate system diagram of a robot and a sensor, FIG. 4 is a diagram explaining the process of obtaining trans (S) which is a translational motion value of a sensor by this invention.

First, the linear laser vision sensor 10 employed in the present invention is a sensor capable of obtaining three-dimensional information on one laser line. As shown in FIG. 1, the laser window 11 and the CCD window 12 are shown. The laser beam emitted from the laser window 11 is irradiated to the object to be measured, and then the reflected beam is received by the CCD window 12 to detect the object to be measured. As shown in FIG. 1, the linear laser vision sensor 10 includes a field of measurement F having an arbitrary width of measurement W and a depth of measurement D. It is positioned so as to have a stand-off (S) by a predetermined distance between the object to be measured. P in FIG. 1 is a laser plane.

2a to 2c shows a measurement jig for position and attitude correction of the sensor attached to the industrial robot according to the present invention, the measuring jig 20 is the size of a rectangle (20 × 50 cm) having a predetermined thickness (for example 4 cm). It is formed in the upper surface, the semi-cylindrical groove (21) 21 having a predetermined length (for example 6 cm) as a semi-cylindrical surface of a predetermined diameter (for example 6 cm), and the diameter of the bottom surface is the semi-cylindrical groove (21, 21) And a semiconical groove 22 having a semi-conical surface having a predetermined height (for example, 40 cm) and having a predetermined height (for example, 40 cm) are formed to be connected to each other. Lines 23 and 24 are successively formed so that the pair of edge portions 21a and the longitudinal axis 23 where the semi-cylindrical groove 21 and the upper surface meet form three parallel lines, and the semi-conical groove 22 and the upper surface. The pair of edges 22a that meet each other is configured to be bisected by the longitudinal axis 24.

In addition, the upper surface of the measuring jig 20 is formed with a rectangular outline (25, 26, 27) circumscribed to the semi-cylindrical groove (21) and the semi-conical groove (22), the semi-cylindrical groove (21) ) And the reference line 28 is formed in the width direction on the boundary line of the half cone groove 22.

The longitudinal axis 23, 24, the outline 25, 26, 27 and the reference line 28 are preferably formed as grooves having a depth and a width of about 1 mm.

Hereinafter, the principle of the position and attitude correction of the sensor attached to the industrial robot according to the present invention.

When the linear laser vision sensor 10 as described above is mounted at the end of the robot (typically 6 axes), it is assumed that the robot and the sensor 10 that know the coordinate system of the end are rigidly attached. The relative coordinate system between the robot end and the sensor 10 to be obtained may be represented by a rotation transformation matrix Rot and a translation transformation matrix trans.

The rotation transformation matrix Rot is a 3 * 3 matrix and the translation transformation matrix trans is a 3 * 1 matrix.

As shown in FIG. 3, the coordinate system of the robot end at the initial position of the robot is called H ₁ , and the position of the sensor at this time is called S ₁ . In addition, the coordinate system of the robot end at the position after moving the robot is called H ₂ and the position of the sensor 10 at this time is called S ₂ . When the robot is moved, the relative rotation transformation matrix of the robot end coordinate system at the initial position of the robot and the later position of the robot at the robot end is called Rot (R) and the translation transformation matrix is called trans (R). The relative rotation transformation matrix of the sensor coordinate system and the translation coordinate matrix Rot (S) is called trans (S).

이라고 하고, 움직인 후의 측정한 좌표값을 S₂좌표계를 기준으로

라고 하면 로봇의 처음 위치 좌표계 H₁에서 다음의 수학식 1이 성립된다.And the coordinate value measured using the linear laser vision sensor 10 at the initial position of the robot based on the S ₁ coordinate system

The coordinate value measured after moving is based on the S ₂ coordinate system.

In this case, the following Equation 1 is established in the first position coordinate system H ₁ of the robot.

Similarly, the following equation (2) holds in the coordinate system H ₂ of the robot after the movement.

When Equation 2 is substituted by Equation 1, Equation 3 is obtained.

This Equation 3 is summarized as Equation 4 below.

Equation 4 is equivalent to Equation 5 as seen from the sensor coordinate system S ₁ .

Therefore, the following equation (6) is established by the relational expressions of equations (4) and (5).

The relative conversion relationship between the robot and the sensor to be obtained is calculated by this equation (6). That is, if only the translational motion without rotational motion is given at the position of the first robot, the second relational expression of Equation 6 is simplified as in Equation 7 below and the rotational translation matrix Rot is obtained by Equation 7.

trans (S) = Rot ^-1 * trans (R)

Using the rotation transformation matrix Rot obtained, the translation transformation matrix trans is obtained by Equation 8, which is a variation of the second relational expression of Equation 6.

trans = (Rot (R) -I) ^-1 * (Rot * trans (S) -trans (R))

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Hereinafter, a method of obtaining a translation transformation matrix trans and a rotation transformation matrix Rot in the present invention will be described.

In general, since a linear laser vision sensor changes a measurement point for measuring a robot as it moves, it is impossible to obtain a trans (S) value, which is a relative translational motion of the sensor.

Therefore, in the present invention, the relative translational motion value trans (S) of the sensor can be obtained using the measuring jig as described above.

In order to obtain the relative translational motion value trans (S) of the sensor, the laser line of the linear laser vision sensor 10 is first aligned with the reference line 28 of the measuring jig 20.

As described above, when the robot makes only the translational movement without rotating the laser line, the laser line always moves in a state perpendicular to the longitudinal axes 23 and 24 of the measuring jig 20.

At this time, even if the laser line is aligned perpendicular to the longitudinal axis 23, 24 of the measuring jig 20, the incident angle of the laser line to the surface of the measuring jig 20 may not be perpendicular to the plane of the measuring jig 20. Since it may be possible, theta value is first obtained as shown in FIG.

In obtaining the theta value, since the dimensions of the surface machined on the measuring jig 20 are already known, the longitudinal axis 23 and the semi-cylindrical groove 21 of the measuring jig 20 are measured using the measuring point measured at the position of the robot. The area of the triangle formed by any one of the edges 21a of both sides is obtained, and this area is equal to the square of the vertical plane of the measuring jig 20 by the cosine of theta. Theta value can be calculated | required by ratio of the reference area of the measurement jig 20 and the measurement area which are known.

As shown in FIG. 4, the coordinate of the _first measured point P ₁ of the sensor is referred to as (0, y ₁ , z ₁ ), and the coordinate of the point P ₂ measured by the sensor 10 after moving the robot is (0 , y ₂ , z ₂ ), the relative distance value of P ₂ and P ₁ is measured using the measuring jig 20.

Since the movement of the robot is fixed to move parallel to the longitudinal axis 23, 24 of the measuring jig 20, the distance value of P ₁ and P ₂ can be obtained by the proportional relationship of the triangle.

Thus when P ₁ as determined with a distance value of P ₂ L ₁ vector value of P ₁ and P ₂ of the first coordinate system of the sensor is L ₂ to L _3, z axis in the x-axis.

The value for the y-axis has the same value as y ₁ measured in the initial coordinate system because the robot moves in parallel with the longitudinal axis of the measuring jig 20.

L ₃ is L ₁ * cos (theta) The vector values of P ₁ and P ₂ for the first sensor coordinate system are (L ₁ * sin (theta), y ₁ , L ₁ * cos (theta)) to be.

Also, for the first sensor coordinate system, since the vector from P ₂ to the later sensor coordinate system does not change the rotation of the first sensor coordinate system and the later sensor coordinate system, the value for the x-axis is '0' and the value for the y-axis is y ₁ -y ₂ The value for the z-axis is -z ₂ . That is, the values of the vectors P ₂ to A ₂ for the first sensor coordinate system are (0, y ₁ -Y ₂ , -z ₂ ). Therefore, trans (S), which is the translational motion value of the desired relative sensor, can be obtained from A ₁ and P ₁ vectors, P ₁ and P ₂ vectors, and P ₂ and A ₂ vectors.

Next, only the translational motion is given to the robot to measure the semi-conical groove 22 of the measuring jig 20. In this way, by measuring the semi-conical groove 22 by the translational motion to obtain the relative coordinate system of the sensor using the measuring jig 20 in the above-described method.

This process is repeated three times for different positions of the semiconical groove 22 to obtain the translational motion value trans (S) of each sensor.

At this time, since the translational motion value of the robot is known in the robot coordinate system, the rotational motion matrix of the robot and the sensor is obtained by Equation 7 above.

Next, the position and attitude of the sensor can be changed by obtaining a translational motion matrix of the robot and the sensor according to Equation 8 using the rotational motion matrix of the robot and the sensor.

In this process, the relative translational motion value of the sensor is obtained by measuring the half cone groove 22 by moving only once while simultaneously giving the robot a translational motion and a rotational motion.

In this case, since the coordinate system of the second sensor is distorted with a rotational motion with respect to the first coordinate system, the second sensor coordinate system is rotated in the same manner as the first coordinate system with the first relation of Equation 6.

When the second sensor coordinate system is rotated in this way, the relative translational motion value trans of the sensor can be calculated as the measuring point of the semiconical groove 22.

That is, the relative translational motion of the robot and the sensor can be obtained by using Equation 8 using the translational motion value of the sensor and the relative translational motion value of the robot, the relative rotational motion value of the robot, and the rotational motion value between the robot and the sensor. It becomes possible.

As described above, according to the present invention, when trying to obtain the information necessary to use the robot by using the three-dimensional coordinate value of the linear laser vision sensor, in finding out the relative transformation relationship between the coordinate system of the end of the robot and the coordinate system of the sensor By moving the robot only 4 times and measuring the coordinate point of the measuring jig using the linear laser vision sensor and converting the coordinate system using the measured coordinate point, the relative transformation relationship between the coordinate system of the robot tip and the coordinate system of the linear laser vision sensor can be found. It is possible to solve all the problems in the conventional method as well as to ensure the simplicity and accuracy of the operation. This invention is a very convenient and useful method in an automated process using a linear laser vision sensor attached to a robot.

Claims (3)

At the end of the industrial robot is formed a circumferential groove and a semi-conical groove having both edges between the upper surface and a longitudinal axis at the bottom at a stand-off position from the linear laser vision sensor at a predetermined distance. Arranging a measuring jig having a reference line extending in a width direction on an upper surface at a boundary portion; Irradiating a laser line of a linear laser vision sensor to the reference line to measure a point at which the laser line intersects the two edges and the longitudinal axis; Obtaining an incident angle (theta) of the laser line by comparing the area of the triangle by three points in the measuring step with the predetermined area of the measuring jig; Obtaining a translational motion value trans (S) of three different sensors by repeating the process of obtaining the relative coordinate system of the sensor by giving only the translational motion to the robot three times; Obtaining a rotational motion matrix Rot between the robot and the sensor according to Equation 7 using the translational motion value trans (R) of three robots already known during the translational motion of the robot; Giving the robot a translational motion and a rotational motion to obtain a relative translational value trans (S) of the sensor; Equation 8 using the translational motion value trans (S) of the sensor and the translational motion value trans (R) of the robot, the relative rotational motion value Rot (R) of the robot and the rotational motion value Rot between the robot and the sensor. Obtaining a relative translational motion value trans between the robot and the sensor; and a method for correcting the position and posture of the sensor attached to the industrial robot. Equation 7 trans (S) = Rot ^-1 * trans (R) Equation 8 trans = (Rot (R) -I) ^-1 * (Rot * trans (S) -trans (R)) A semicylindrical groove 21 having a semi-cylindrical surface and a semi-conical groove having a semi-conical surface are connected to the upper surface of the jig body formed in a rectangular size having a predetermined thickness, and these semi-cylindrical grooves 21 and half A longitudinal axis is continuously formed at the center line of the conical groove so that the pair of edges and the longitudinal axis where the semi-cylindrical groove 21 and the upper surface meet form three parallel lines, and the pair of edges where the semi-conical groove and the upper surface meet is the longitudinal axis Measuring jig for correcting the position and attitude of the sensor attached to the industrial robot, characterized in that configured to be bisected by. According to claim 2, the upper surface of the jig body is formed with a rectangular outline forming a semi-cylindrical groove 21 and a semi-conical groove, the reference line is formed on the boundary line between the semi-cylindrical groove 21 and the semi-conical groove. Measuring jig for position and attitude correction of the sensor attached to the industrial robot, characterized in that formed in the width direction.

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