KR100225883B1 - 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 linear laser vision sensor attached to an industrial robot and a measuring jig used therein. In practice, when you operate a robot program, you need to know the exact TCP so that the correct operation is possible. However, the method of finding TCP is a very cumbersome task, which requires a lot of tricky teaching to find the position and posture of the tool or sensor, and its accuracy is inferior because it is purely dependent on the operator's eyes. . In particular, in the case of a linear laser vision sensor, the method of teaching to find the TCP is very difficult. According to the present invention, a measuring jig having three parallel lines and one diagonal line is positioned in front of the robot and the measurement is easily performed in a non-contact manner by using the geometric relationship of the measured value with respect to the specific measuring jig using the characteristics of the linear laser vision sensor. By doing so, TCP can be found quickly, accurately and easily.

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, when an arbitrary sensor or tool is attached to the end axis of the robot (usually 6 axes), the point indicating how much position and posture is attached from the coordinates of the end axis of the robot is called TCP (Tool Center Point). This TCP is very important for robot control.

The arm length of the robot itself is known, but the tool or sensor attached to the end shaft changes its size or shape every time it is changed, so the TCP must be changed.

In practice, when you operate a robot program, you need to know the exact TCP so that the correct operation is possible.

However, the method of finding TCP is a very cumbersome task, which requires a lot of tricky teaching to find the position and posture of the tool or sensor, and its accuracy is inferior because it is purely dependent on the operator's eyes. .

In particular, in the case of a linear laser vision sensor, the method of teaching to find the TCP is very difficult.

Therefore, in the case of the conventional linear laser vision sensor, in order to find TCP, a method of directly measuring the case of the sensor by using a ruler to find out how far and distorted from the center point of the end axis of the robot is used.

However, since this method has no choice but to rely on the eyesight of the operator, the measurement value is inaccurate, and there is a limit to measuring fine distortion, and there is a cumbersome problem of repeating the measurement and verification to verify it.

An object of the present invention is to provide an industrial robot that can quickly and accurately determine TCP by using a characteristic of a linear laser vision sensor to facilitate measurement in a non-contact manner by using a geometric relationship of measured values with respect to a specific measuring jig. It is to provide a TCP measuring method and a measuring jig used therein.

1 is a perspective view showing a relationship between a measuring jig and a linear laser vision sensor according to the present invention.

Figure 2 is a perspective view showing a geometric model of the measuring jig.

3 is a geometric diagram showing a vector relationship around two measurement points.

4 shows the geometric relationship of the vectors around two measurement points.

5 is a geometric diagram for obtaining an offset amount.

** description of the symbols for the main parts of the drawings **

10: linear laser vision sensor 20: measuring jig

21,22,23: parallel 24: diagonal

25,26: fixed plate

In order to achieve the object of the present invention, a linear laser vision sensor has an end axis of a measuring jig having three diagonal lines passing through three vertices of an equilateral triangle and a diagonal line connecting one end of a parallel line positioned above and the other end of a lower parallel side line. Positioning in front of the robot attached to the laser beam, irradiating a laser beam of the linear laser vision sensor to a jig to measure a point where the laser beam crosses each parallel line, and using the three measurement points Obtaining the amount of rotation between the two, and performing the translational movement only a constant distance in the x, y, z axis from the measuring point while fixing the rotation of the robot, the laser beam intersects the upper parallel and diagonal lines of the jig Measuring the points to be used, and using these measuring points, Obtaining a rotation amount, positioning the laser beam of the sensor at a right angle with the parallel line of the jig by using the rotation amount between the sensor and the end axis of the robot, and twice each of the laser beams in the x, y and z axis directions. Measuring the intersection point with respect to the parallel line, calculating the offset amount between the sensor and the robot end axis using the geometric relationship using these measurement points, and using the offset amount to calculate the translational motion between the sensor and the robot end axis. A method for correcting the position and attitude of a sensor attached to an industrial robot, comprising: three parallel lines passing parallel to three vertices of an equilateral triangle, and one end of a parallel line positioned at an upper side and the other end of a lower parallel line The measuring jig used to correct the position and attitude of the sensor attached to the industrial robot, characterized in that having a diagonal Is provided.

Each of the parallel lines and diagonal lines is fixed to both ends of the fixing plate facing each other.

Hereinafter, the TCP measuring method of the industrial robot according to the present invention and the measuring jig used therein will be described in detail according to the embodiments shown in the accompanying drawings.

1 is a perspective view showing the relationship between the sensor and the measuring jig attached to the end axis of the industrial robot according to the present invention, 1 is the end axis (6 axes) of the robot, 10 is a linear laser vision sensor attached to the end axis (1) 20 is the measuring jig.

The measuring jig 20 includes three parallel lines 21, 22, and 23 passing through three vertices of an equilateral triangle, and one end (right end in the drawing example) and a lower one side parallel line of the parallel line 21 located above. 22 has a diagonal line 24 connecting the other end (left side in the illustrated example), and the parallel lines 21, 22, 23 and the diagonal lines 24 are fixed at both ends to fixing plates 25 and 26 facing each other. Will be.

The parallel lines 21, 22 and 23 and the diagonal line 24 may be any wire rods that can be detected by the linear laser vision sensor 10, and the fixed plates 25 and 26 are the parallel lines ( As long as it can support 21, 22, 23 and diagonal line 24, anything may be sufficient. Although not shown, the fixing plates 25 and 26 are fixed to both ends of the support to maintain the gap therebetween.

In fixing the parallel lines 21, 22, 23 and the diagonal line 24 to the fixing plates 25 and 26, holes are formed in the fixing plates 25 and 26 to form an equilateral triangle having a length of about 30 mm and parallel lines 21 to the fixing plates 25 and 26. , 22, 23 and both ends of the diagonal (24) can be fitted and fixed, in addition to any method that can be fixed to the parallel lines (21, 22, 23) and diagonal (24) to the fixing plate (25, 26) It may be adopted.

In order to perform the position and attitude correction method of the sensor attached to the industrial robot according to the present invention, the measuring jig 20 is disposed in front of the robot in which the sensor 10 is attached to the end shaft. In this case, as shown in FIG. 1, the laser beam of the linear laser vision sensor 10 intersects all of the parallel lines 21, 22, 23, and the diagonal line 24, and the robot beam is moved as much as possible by moving the robot. 21, 22, 23), (24) to be perpendicular to each other.

When the laser beam of the linear laser vision sensor 10 is irradiated to the measuring jig 20 as shown in FIG. 2, the laser beam is perpendicular to each of the lines 21, 22, 23 and 24. The triangle formed by the points P1, P02, and P03 where the beam crosses each of the lines 21, 23, and 23 becomes an equilateral triangle, but the laser beam and the line 21 when the angle of the sensor 10 and the measuring jig 20 are inclined. The triangle formed by the points P1, P2, and P3 intersected by (22,23) becomes an isosceles triangle, not an equilateral triangle.

Measured values of these three points P1, P2, and P3 P ₁ ^s P ₂ ^s P ₃ ^s If so, the triangle represented in the coordinate system of the jig 20 using this P ₁ j P ₂ ^j P ₃ ^j The coordinate of can be expressed by the following equation (1).

The three points are used to define a vector such as three equations (2).

Similarly, defining the vector in the sensor coordinate system is shown in Equation 3.

This makes it possible to measure the amount of rotation between the jig and the sensor.

Next, while performing the translational motion only by a certain distance from the first measurement point to the X, Y, Z axis while fixing the rotation of the robot, it is measured three more times.

At this time, since the rotation is fixed, the translational motion of the robot end shaft and the translational motion of the sensor are the same. The translational momentum of the end axis of the robot is a known value and the translational momentum of the sensor can be obtained as follows.

Using the triangle on the side of the jig 20, that is, the triangle formed by the parallel lines 21 and the diagonal lines 24, the geometric correlation between the first measurement point and the next measurement point is shown in FIG.

This correlation is shown in Equation 4 below.

t _s = P ₁ ^s + a ₁₂ ^s -P ₂ ^s

By measurement P ₁ ^s P ₂ ^s Know and a, b Since the vector is a known value from the design P ₁ ^s in P ₂ ^s Headed to a Vector a ₁₂ ^s If you find t _s Can be expressed.

here a ₁₂ ^s Can be obtained as shown in Equation 5 using the geometric relationship of the vectors around the two measurement points of FIG.

here

를 만들고 이를 이용하여 수학식 6과 같이 센서(10)와 로봇 끝축간의 회전 행렬 R₆ ^s 를 구한다.Three obtained like this t _s In a row

And use this to make a rotation matrix between the sensor 10 and the robot end axis, as shown in equation (6). R ₆ ^s Obtain

After obtaining the rotation matrix between the sensor and the jig in the same way as above, find the offset between the sensor and the robot end axis through the following process.

A mathematical method can be used to calculate the offset between the sensor and the robot's end axis, but in this case, the geometric method is used because it has too sensitive a measurement error.

First, since the rotation matrix between the end axis of the robot and the sensor is known, the robot is moved so that the laser beam B is perpendicular to the parallel lines 21, 22, and 23 of the jig 20, as shown in FIG. 5. Can be positioned to achieve.

The measurement is performed at this position, the sensor 20 is rotated at an angle and the second measurement is performed.

This can be calculated as follows from the geometric diagram of FIG. 5. At this time, all coordinate systems are displayed in the coordinate system of the first sensor.

next t _z Rotate 90 degrees around the y axis to find the y value of the sensor. t _z Becomes

In the same way as above, after the translational momentum in the x, z direction, the translational motion coincides with the x, z direction while the TCP of the robot coincides with the rotation, and then the translational motion in the y direction is 90 in the x direction. If the rotation is measured in degrees, the measured value in the y-axis direction translates into the y-direction t _z Becomes

As described above, according to the present invention, by using a jig having three parallel lines and one diagonal line, a difficult TCP of the linear laser vision sensor can be easily obtained in a single teaching, and accurate measurement is possible even through a rough teaching. do. In addition, the geometric approach enables accurate measurements at once without being affected by measurement errors.

Claims (3)

A measuring jig having three parallel lines passing parallel to three vertices of an equilateral triangle and a diagonal line connecting one end of an upper parallel line and the other end of a lower one parallel line is positioned in front of the robot with the linear laser vision sensor attached to the end axis. Steps, Irradiating a jig with the laser beam of the linear laser vision sensor and measuring a point where the laser beam intersects each parallel line; Obtaining the amount of rotation between the sensor and the jig using the three measurement points, Measuring the point where the laser beam intersects the upper parallel line and the diagonal line of the jig by measuring three times by performing a translational movement only by a predetermined distance from the measuring point on the x, y, z axis with the rotation of the robot fixed; Calculating the amount of rotation between the sensor and the end axis of the robot using geometric relations using these measurement points, Positioning the laser beam of the sensor at a right angle with the parallel line of the jig by using the amount of rotation between the sensor and the robot end shaft; measuring an intersection with respect to the parallel lines of the laser beam twice each of the x, y, and z-axis directions; Calculating the offset amount between the sensor and the robot end axis by using the geometric relationship using these measurement points, A method for correcting the position and posture of a sensor attached to an industrial robot, characterized by calculating the translational movement between the sensor and the robot end axis using the offset amount. It is used to correct the position and attitude of the sensor attached to the industrial robot, which has three parallel lines that pass three vertices of the equilateral triangle in parallel with each other, and a diagonal line connecting one end of the parallel line located on the upper side and the other end of the one parallel line on the lower side. Measuring jig made. The measuring jig used for correcting the position and attitude of the sensor attached to the industrial robot according to claim 2, wherein the parallel lines and the diagonal lines are fixed at both ends to a fixed plate facing each other.

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