JP2012035329A - Method for calibrating six-axes home position of six-axes robot, control device of six-axes robot, method for calibrating seven-axes home position of seven-axes robot and control device of seven-axes robot - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for calibrating a sixth axis home position of a six axes robot for properly calibrating a home position of the sixth axis of the six axes robot without requiring installation of a large-sized detection instrument.SOLUTION: A laser measuring device for measuring a distance from a measuring object located on an upper side is installed on an installation surface and a measuring plate is mounted at an axial center of the sixth axis. When one end side of the measuring plate is located to be a first measuring point in a state of the six axes robot taking an attitude in which a second axis of the six axes robot is rotated by 90° with respect to an axial center of a first axis, a third axis is rotated in a direction of the installation surface so that an axial center of a forth axis is parallel to the axial center of the first axis, and a fifth axis is rotated so that an axial center of the sixth axis is parallel to the installation surface (S1), a first distance L1 up to the first measuring point is measured by the laser measuring device (S2). When the first axis is rotated, the other end side of the measuring plate is located to a second measuring point (S3) and a second distance L2 up to a second measuring point is measured by the laser measuring device (S4), an error angle Δθ6 of the sixth axis is determined by a (1) formula (S5) and the home position of the sixth axis is calibrated by using the error angle Δθ6 (S6).

Description

  The present invention relates to a method for calibrating a six-axis origin position in a six-axis robot, a control apparatus for a six-axis robot, a method for calibrating a seven-axis origin position in a seven-axis robot, and a control apparatus for a seven-axis robot.

For example, the calibration of the origin position of each axis in an articulated robot such as a 6-axis robot is basically performed at the factory before shipment from the factory, and after being shipped from the factory and installed at the installation site, the motor This is done at the installation site when the origin position is changed by exchanging the above. As a method of calibrating the origin position of each axis, there is a method of installing a large detection instrument (for example, see Patent Document 1) or a method of adding a special sensor for detection (for example, see Patent Documents 1 and 2). is there. Patent Documents 3 to 5 disclose methods and apparatuses for calibrating the origin positions of the 5-axis, 3-axis, and 2-axis without installing a large detection instrument for a 6-axis robot.
JP-A-6-304893 Japanese Patent Laid-Open No. 2003-220587 JP 2009-274186 A JP 2009-274187 A JP 2009-274188 A

  However, it may be difficult to secure a space for installing a large detection instrument. In addition, there is a situation where it is desired to avoid implementation of a method for adding a special sensor for detection because it causes an increase in cost. A method for calibrating the six-axis origin position of the six-axis robot in consideration of these circumstances has not been proposed in the past.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a 6-axis robot that can appropriately calibrate the 6-axis origin position for a 6-axis robot without having to install a large-sized detection instrument. To provide a 6-axis origin position calibration method, a 6-axis robot controller, a 7-axis robot 7-axis origin position calibration method and a 7-axis robot controller capable of appropriately calibrating the 7-axis origin position for a 7-axis robot is there.

  According to the 6-axis origin position calibration method of the 6-axis robot according to claim 1, the distance measuring means for measuring the distance to the measurement object located above is installed on the installation surface, and the measurement is performed on the 6-axis axis. Install the board. Then, two axes of the six-axis robot are rotated by π / 2 [rad] with respect to the axis of one axis, and three axes are arranged on the installation surface so that the four axes are parallel to the one axis. The measurement plate is positioned such that one end side of the measurement plate becomes the first measurement point in a state in which the orientation is rotated so that the six axes are parallel to the installation surface. First step) and a first distance L1 to the first measurement point is measured by the distance measuring means (second step).

Next, one axis is rotated so that the other end of the measurement plate is positioned at the second measurement point (third step), and the second distance L2 to the second measurement point is measured by the distance measuring means (first step). 4 steps). Then, the six-axis error angle Δθ6 is expressed by the following equation:
Δθ6 = arctan {ΔL * cos (θ_def) / M} −θ6
If it is obtained (fifth step), the origin positions of the six axes are calibrated using the error angle Δθ6 (sixth step). Note that the distance M from the first measurement point to the second measurement point is R as the rotation radius from the axis of one axis to the first and second measurement points, and θ as the rotation angle of one axis in the third step. For example, M = R * θ. The above formula for calculating the error angle Δθ6 is, for the sake of simplicity, assuming that the angle θ_def made with respect to the normal line where the measurement direction stands on the ground plane is zero,
tan (θ6 + Δθ6) = ΔL / M
Because of the relationship.

  That is, the distance difference ΔL obtained by measuring the first distance L1 with the posture taken by the six-axis robot in the first step and measuring the second distance L2 after rotating the first axis in the third step is exclusively It is determined by the rotation angle of 6 axes (including the deviation if there is an origin position deviation) and is not affected by 1 to 5 axes. Therefore, even when the origin positions of the first to fifth axes are not calibrated, the six-axis error angle Δθ6 can be obtained, and the six-axis origin position can be calibrated.

According to the control apparatus for a six-axis robot according to claim 2, the position / posture control means rotates the two axes by π / 2 [rad] with respect to the axis of one axis, and the axis of the four axes has one axis. After rotating the three axes in the direction of the installation surface so as to be parallel to the axis of the axis and rotating the five axes so that the axis of the six axes is parallel to the installation surface, Is rotated by an arbitrary angle. Then, the origin position calibration means has a first distance L1 from the reference position to the first measurement point (before 1-axis rotation) of the measurement plate attached to the 6-axis axis, and the second measurement of the measurement plate from the reference position. When the second distance L2 to the point is obtained, the six-axis error angle Δθ6 is expressed by the following equation.
Δθ6 = arctan (ΔL / M) −θ6
The six-axis origin position is calibrated using the error angle Δθ6. Therefore, an effect similar to that of the first aspect can be obtained.

  According to the seven-axis origin position calibration method for the seven-axis robot according to the third aspect, the invention according to the first aspect can be applied to the seven-axis robot. That is, the 7-axis robot is generally configured to include 3 axes having axes that are orthogonal to these axes between the 2 and 4 axes corresponding to the 2 and 3 axes in the 6-axis robot. Therefore, the invention according to claim 1 can be applied to the seven-axis robot by replacing the three to six axes of the six-axis robot with the four to seven axes of the seven-axis robot. However, in this case, it is assumed that the origin positions of the three axes are already calibrated. Further, according to the control apparatus for the seven-axis robot according to the fourth aspect, the invention according to the second aspect can be applied to the seven-axis robot for the same reason as described above.

1 is a perspective view of a robot apparatus according to a first embodiment. Functional block diagram Schematic diagram showing the relationship of each axis flowchart State transition diagram (part 1) State transition diagram (part 2) (A) is the figure which looked at the axial center of 6 axes from the front, (b) is the figure which defines the positive / negative of the rotation direction of 6 axes. FIG. 7A equivalent view showing the second embodiment. FIG. 3A is a diagram corresponding to FIG. 3, and FIG. 5B is a diagram corresponding to FIG.

(First embodiment)
The first embodiment will be described below with reference to FIGS. As shown in FIG. 1, the robot apparatus 1 includes a vertical articulated robot (hereinafter referred to as a robot) 2, a control device (position / posture control means, origin position calibration means) 3 that controls the operation of the robot 2, and The teaching pendant 4 connected to the control device 3 is provided.

  The robot 2 includes a base 5, a shoulder portion 6 supported by the base 5 so as to be turnable in the horizontal direction, a lower arm 7 supported by the shoulder portion 6 so as to be turnable in the vertical direction, and a lower arm 7 A first upper arm 8 that is supported so as to be pivotable in a direction, a second upper arm 9 that is supported by a tip portion of the first upper arm 8 in a twistable manner, and a second upper arm 9. The wrist 10 is supported by being rotatable in the vertical direction, and the flange 11 is supported by the wrist 10 so as to be rotatable (twisting).

  The shoulder portion 6, the lower arm 7, the first upper arm 8, the second upper arm 9, the wrist 10 and the flange 11 including the base 5 described above function as links of the robot 2, and each link excluding the base 5 Is rotatably connected to the lower link by a rotary joint. A flange (not shown) for gripping a workpiece can be attached to the flange 11 which is the most advanced link. In addition, the rotary joint that connects the links is provided with a reduction gear that reduces the rotation of the motor fixed to the previous link and transmits it to the next link.

  In the present embodiment, the joint axis of the rotary joint that connects between the base 5 that is the first link and the shoulder portion 6 that is the second link is one axis, and the shoulder portion 6 that is the second link, Two joint axes of the rotary joint connecting between the lower link 7 as the third link and between the lower arm 7 as the third link and the first upper arm 8 as the fourth link Three joint axes of the rotary joint to be connected, and four joint axes of the rotary joint connecting the first upper arm 8 being the fourth link and the second upper arm 9 being the fifth link. In addition, the five joint axes of the rotary joint connecting the second upper arm 9 as the fifth link and the wrist 10 as the sixth link, and the wrist 10 and the seventh link as the sixth link The joint axes of the rotary joint that connects with the flange 11 are shown as six axes.

  That is, as shown in FIG. 3, the robot 2 is a PUMA type robot having 6-axis vertical articulated joints. The 1-axis axis is perpendicular to the installation surface of the 6-axis robot, and the 2-axis axis is Orthogonal to 1 axis, 2 axes, 3 axes and 5 axes are parallel, 5 axes are the same as 4 axes and 6 axes The configuration is orthogonal at one point.

  As illustrated in FIG. 2, the control device 3 that controls the operation of the robot 2 includes a CPU 12, a drive circuit 13, and a position detection circuit 14. The CPU 12 is connected with a ROM 15 for storing a robot language for creating a system program and an operation program for the entire robot 2 and a RAM 16 for storing an operation program for the robot 2 and used for teaching work. Teaching pendant 4 is connected. As shown in FIG. 1, the teaching pendant 4 includes various operation units 4a and a display 4b.

  The position detection circuit 14 is for detecting the positions of the shoulder portion 6, the arms 7 to 9, the wrist 10 and the flange 11. The position detection circuit 14 is provided for each axis of the shoulder portion 6, the arms 7 to 9, the wrist 10 and the flange 11. A rotary encoder 18 provided in a motor 17 that is a drive source is connected. The position detection circuit 14 is based on the detection signal input from the rotary encoder 18, the rotation angle of the shoulder portion 6 with respect to the base 5, the rotation angle of the lower arm 7 with respect to the shoulder portion 6, and the first upper arm 8 with respect to the lower arm 7. The rotation angle, the rotation angle of the second upper arm 9 relative to the first upper arm 8, the rotation angle of the wrist 10 relative to the second upper arm 9, and the rotation angle of the flange 11 relative to the wrist 10 are detected, and the detected position is detected. Information is output to the CPU 12. The CPU 12 controls the operation of the shoulder unit 6, the arms 7 to 9, the wrist 10 and the flange 11 based on the operation program using the position detection information input from the position detection circuit 14 as a feedback signal. To do.

  Each link has three-dimensional coordinates. Among these, the coordinate system of the base 5 installed on the floor surface is a reference coordinate of the robot 2 as a stationary coordinate system as shown in FIG. Two coordinate axes Xb and Yb and one coordinate axis Zb in the vertical direction are defined. In the coordinate system of the other links, the position and orientation on the reference coordinates change due to the rotation of each rotary joint, and the CPU 12 receives the shoulder 6, the arms 7 to 9, the wrist 10, and the flange input from the position detection circuit 14. 11 based on the position detection information of each rotary joint and the length information of each joint stored in advance, the position and orientation of the coordinates of each joint are converted to the position and orientation on the reference coordinates by the coordinate conversion calculation function. Convert to and recognize.

  In the robot 2 described above, the calibration of the origin position of each axis is basically performed at the factory before shipment from the factory, and after being shipped from the factory and installed at the installation destination, the motor 17 and the like. This is done at the installation site when the origin position is changed by exchanging. The operation of this embodiment, that is, the procedure for calibrating the origin positions of the six axes will be described below with reference to FIGS.

  The CPU 12 stores and holds a control program for calibrating the origin positions of the six axes, and executes the control program to calibrate the origin positions of the six axes. Here, FIG. 4 shows processing performed by the CPU 12, and FIG. 5 shows an initial posture of the robot 2 for measuring the measurement point (1). In this posture, two axes are rotated 90 degrees (π / 2 [rad]) so that the lower arm 7 is parallel to the installation surface (coordinate axis Xb), and the first upper arm 8 and the second upper arm 9 are The three axes are rotated by 90 degrees with respect to the lower arm 7 so that the upper arms 8 and 9 are directed to the negative direction of the coordinate axis Zb so as to be perpendicular to the installation surface (the upper arms 8 and 9). The three axes may be rotated by 90 degrees with respect to the lower arm 7 so that is directed in the positive direction of the coordinate axis Zb). Further, the five axes are rotated by 90 degrees with respect to the second upper arm 9 so that the axis of the wrist 10; 6 axes is parallel to the installation surface (step S1; first step).

In this state, it is assumed that the axis direction of the six axes coincides with the coordinate axis Xb, and the rotation angle of the six axes may be an arbitrary angle θ6 [rad]. A rectangular measurement plate 19 is attached to the flange 11 at a known angle with respect to the installation surface of the robot. At this time, the angular rotation angles of the 1st to 6th axes are, for example, as follows.
(0, π / 2, π / 2, 0, -π / 2, θ6)

Further, for example, a laser measuring instrument (distance measuring means) 20 is arranged on the installation surface. The installation surface of the base 5 and the installation surface of the laser measuring instrument 20 do not necessarily have to be the same plane, and may be planes that are parallel to each other. For example, when taking the above posture, if the wrist 10 is positioned below the installation surface of the base 5 due to the length of the upper arms 8 and 9, the robot 2 is placed on the installation surface of the laser measuring instrument 20. A base having a predetermined height may be arranged, and the base 5 may be installed on the base.
The laser measuring instrument 20 is installed so as to measure the distance in the coordinate axis Zb direction. And in said attitude | position, the distance L1 to the measurement point (1) is measured by the laser measuring device 20 by making the one end side of the measurement board 19 into the measurement point (1) (step S2; 2nd process). For example, when viewed from above as shown in FIG. 5A, the left end side of the measurement plate 19 is set as the measurement point (1).

  Next, the measurement object by the laser measuring instrument 20 is rotated by an angle θ while fixing the 2nd to 6th axes so that the measurement point (2) is the right end side of the measurement plate 19 (step S3; (3rd process). At this time, the rotation direction of one axis shown in FIG. 6 is the counterclockwise direction. In this state, the distance L2 to the measurement point (2) is measured by the laser measuring instrument 20 (step S4; fourth step). The apparent rotation angle θ6 ′ of the six axes is the sum of the true rotation angle θ6 and the deviation angle Δθ6 of the origin, and the measurement plate 19 is inclined with respect to the installation surface by the rotation angle θ6 ′. There is a difference ΔL from L2 (see FIG. 7A). That is, if one axis is rotated from the posture in step S1 as in step S3, the rotation angle θ6 ′ can be measured without being affected by the first to fifth axes.

Therefore, when the distance between the measurement points (1) and (2) is M, the deviation Δθ6 [rad] is obtained from the following equation (step S5; fifth step).
Δθ6 = arctan (ΔL / M) −θ6 (1)
The distance M can be obtained from M = R * θ, where R is the radius of rotation from the axis of one axis to the first and second measurement points, and θ is the rotation angle of one axis in step S3. When the deviation Δθ6 is obtained, the origin positions of the six axes are calibrated based on the deviation Δθ6 (step S6; sixth step). For example, when the origins of the six axes are shifted in the positive direction shown in FIG. 7B as shown in FIG. 7A, calibration is performed by subtracting the obtained shift Δθ6.

  As described above, according to the present embodiment, the laser measuring instrument 20 that measures the distance from the measurement object positioned above is installed on the installation surface, and the measurement plate 19 is attached to the six axes. Then, the two axes of the robot 2 are rotated 90 degrees with respect to the axis of one axis, the three axes are rotated in the direction of the installation surface so that the axis of the four axes is parallel to the axis of the one axis, When the one end side of the measuring plate 19 is positioned to be the first measurement point in a state where the five axes are rotated so that the six axes are parallel to the installation surface, the laser measuring instrument The first distance L1 to the first measurement point is measured by 20. Next, when one axis is rotated so that the other end side of the measurement plate 19 becomes the second measurement point, and the second distance L2 to the second measurement point is measured by the laser measuring instrument 20, a six-axis error is obtained. The angle Δθ6 is obtained by the equation (1), and the origin positions of the six axes are calibrated using the error angle Δθ6.

  That is, the distance difference ΔL between the two obtained by measuring the first distance L1 in the posture taken by the robot 2 in the first step and measuring the second distance L2 after rotating one axis in the third step is: Since it is determined solely by the rotation angle θ6 ′ of 6 axes (including the origin position deviation if there is any deviation), it is not affected by the 1st to 5th axes. Therefore, even if the origin positions of the first to fifth axes are not calibrated, the six-axis error angle Δθ6 can be obtained and the six-axis origin position can be calibrated.

(Second embodiment)
FIG. 8 shows a second embodiment. The same parts as those of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted. Hereinafter, different parts will be described. FIG. 8 is a diagram corresponding to FIG. 7 of the first embodiment, which is assumed to be irregular, but installed so that the measurement axis of the laser measuring instrument 20 is inclined with respect to the normal of the installation surface. Show the case. At this time, if the inclination angle is θ_def, the deviation Δθ6 may be obtained by changing the equation (1) to the equation (2).
Δθ6 = arctan {ΔL * cos (θ_def) / M−θ6} (2)
Here, if the inclination angle θ_def in the equation (2) is set to 0 [rad], it coincides with the equation (1).

FIG. 8 shows a case where the measurement point (1) is the left end side (when viewed from the front) of the measurement plate 19. At this time, the direction in which one axis is rotated in step S3 is opposite to FIG. The measurement point (2) is on the right end side of the measurement plate 19 (when viewed from the front).
As described above, according to the second embodiment, even when the measurement axis of the laser measuring instrument 20 is installed so as to be inclined with respect to the normal line of the installation surface, the same as in the first embodiment. The origin of 6 axes can be calibrated by obtaining the deviation Δθ6.

(Third embodiment)
FIG. 9 shows a third embodiment, in which the first embodiment is applied to a seven-axis robot. FIG. 9A is a diagram corresponding to FIG. 3 of a general seven-axis robot. As described above, the 7-axis robot is configured to include 3 axes having an axis perpendicular to these axes between the 2 and 4 axes corresponding to the 2 and 3 axes in the 6-axis robot. . Therefore, the origin position calibration method of the first embodiment can be applied to the 7 axis origin position calibration method of the 7 axis robot by replacing the 3 axis to 6 axis of the 6 axis robot with the 4 axis to 7 axis of the 7 axis robot. . However, in this case, it is assumed that the origin positions of the three axes are already calibrated.

The present invention is not limited to the embodiments described above or shown in the drawings, and the following modifications or expansions are possible.
For example, the posture of the robot in the first step may be set as follows.

(Θ1, π / 2, π / 2, θ4, π / 2, θ6)
(Θ1, π / 2, -π / 2, θ4, π / 2, θ6)
(Θ1, π / 2, -π / 2, θ4, -π / 2, θ6)
Note that θ1 and θ4 are arbitrary. Of course, θ1, θ4, and θ6 may be set to 0 [rad].

The timing at which the measurement plate 19 is attached to the flange 11 may be before the processing shown in FIG. 4 is executed, and may be any timing as long as it is before the execution of step S2.
The 7-axis robot of the third embodiment is also calibrated in a state where the measurement axis of the laser measuring instrument 20 is tilted with respect to the normal of the installation surface as in the second embodiment. May be.
The distance measuring means is not limited to the laser measuring instrument 20, and the method for measuring the distance is arbitrary.
The calculation formulas shown in the above embodiments are based on the premise that the angle is represented by the arc method [rad]. However, even when the power method is used, the same result can be obtained by matching with the arc method. Therefore, the origin deviation of the 6-axis or 7-axis may be obtained in the same manner using a calculation formula in which the angle is expressed by the frequency method.

  In the drawings, 2 is a robot (6-axis robot, articulated robot), 3 is a control device (position / posture control means, origin position calibration means), and 20 is a laser measuring instrument (distance measurement means).

Claims (4)

The axis of 1 axis is orthogonal to the installation surface of the 6 axis robot, the axis of 2 axes is orthogonal to the axis of 1 axis, and the axis of 2 axes, 3 axes and 5 axes are A method of calibrating the origin positions of the six axes of a six-axis robot configured such that the five axes are parallel to each other and perpendicular to the four axes and the six axes.
On the installation surface, a distance measuring means for measuring the distance to the measurement object located above is installed,
A measuring plate is attached to the 6-axis shaft center,
Two axes are rotated by π / 2 [rad] with respect to the axis of one axis, and three axes are rotated in the direction of the installation surface so that the axis of four axes is parallel to the axis of one axis. One end side of the measuring plate in a direction orthogonal to the six-axis axis is in the state of rotating the five axes so that the axis of the axis is parallel to the installation surface. A first step to be positioned to be a measurement target (first measurement point);
A second step of measuring a first distance L1 to the first measurement point by the distance measuring means;
A third step of rotating one axis and positioning the other end side of the measurement plate in the orthogonal direction to be a measurement target (second measurement point) of the distance measurement unit;
A fourth step of measuring a second distance L2 to the second measurement point by the distance measuring means;
The distance from the first measurement point to the second measurement point is M, the difference between the first distance L1 and the second distance L2 is ΔL, the rotation angle of six axes is θ6, and the distance measurement means measures the distance. When the angle formed by the measurement direction with respect to the normal line standing on the ground plane is θ_def (the unit of the angle is [rad]), the six-axis error angle Δθ6 is expressed by the following equation:
Δθ6 = arctan {ΔL * cos (θ_def) / M} −θ6
A fifth step to be obtained,
6. A 6-axis origin position calibration method for a 6-axis robot, comprising a sixth step of calibrating the origin position of 6 axes using the error angle Δθ6. The axis of 1 axis is orthogonal to the installation surface of the 6 axis robot, the axis of 2 axes is orthogonal to the axis of 1 axis, and the axis of 2 axes, 3 axes and 5 axes are A control device for a 6-axis robot, which is parallel to each other and configured so that the 5-axis axis is orthogonal to the 4-axis axis and the 6-axis axis at the same point,
Two axes are rotated by π / 2 [rad] with respect to the axis of one axis, and three axes are rotated in the direction of the installation surface so that the axis of four axes is parallel to the axis of one axis. A position / posture control means for rotating one axis by an arbitrary angle after taking a measurement posture by rotating the five axes so that the axis of the shaft is parallel to the installation surface;
The measuring plate attached to the 6-axis axis is positioned in the normal direction standing on the reference position set on the installation surface side before the position / posture control means rotates one axis. One end side of the measurement plate in the direction orthogonal to the axis of the six axes is a first measurement point, and the position / posture control means is positioned in the normal direction at a position after the position / posture control means has rotated one axis. The other end side in the orthogonal direction as a second measurement point,
The first distance from the reference position to the first measurement point is L1, the second distance from the reference position to the second measurement point is L2, and the distance from the first measurement point to the second measurement point is M. , Where the difference between the first distance L1 and the second distance L2 is ΔL and the rotation angle of the six axes is θ6 (the unit of the angle is [rad]), the error angle Δθ6 of the six axes is expressed by the following equation:
Δθ6 = arctan (ΔL / M) −θ6
And a home position calibration unit that calibrates the home position of the 6 axes using the error angle Δθ6. The axis of 1 axis is orthogonal to the installation surface of the 6 axis robot, the axis of 2 axes is orthogonal to the axis of 1 axis, the axis of 3 axes is orthogonal to the axis of 2 axes, 2 axes The 6-axis axis, the 4-axis axis, and the 6-axis axis are parallel to each other, and the 6-axis axis is orthogonal to the 5-axis axis and the 7-axis axis at the same point. A method for calibrating the origin positions of seven axes in an axis robot,
On the installation surface, a distance measuring means for measuring the distance to the measurement object located above is installed,
Attach the measuring plate to the center of 7 axes,
Two axes are rotated by π / 2 [rad] relative to the axis of one axis, and four axes are rotated in the direction of the installation surface so that the axis of five axes is parallel to the axis of one axis. In a state where the six axes are rotated so that the axis of the shaft is parallel to the installation surface, one end side of the measurement plate in the direction orthogonal to the axis of the seven axes is connected to the distance measuring means. A first step to be positioned to be a measurement target (first measurement point);
A second step of measuring a first distance L1 to the first measurement point by the distance measuring means;
A third step of rotating one axis and positioning the other end side of the measurement plate in the orthogonal direction to be a measurement target (second measurement point) of the distance measurement unit;
A fourth step of measuring a second distance L2 to the second measurement point by the distance measuring means;
The distance from the first measurement point to the second measurement point is M, the difference between the first distance L1 and the second distance L2 is ΔL, the rotation angle of the seven axes is θ7, and the distance measuring means measures the distance. If the angle formed by the measurement direction with respect to the normal line standing on the ground plane is θ_def (the unit of the angle is [rad]), the seven-axis error angle Δθ7 is expressed by the following equation:
Δθ7 = arctan {ΔL * cos (θ_def) / M} −θ7
A fifth step to be obtained,
A 7-axis origin position calibration method for a 7-axis robot, comprising a sixth step of configuring an origin position of 7 axes using the error angle Δθ7. The axis of 1 axis is orthogonal to the installation surface of the 6 axis robot, the axis of 2 axes is orthogonal to the axis of 1 axis, the axis of 3 axes is orthogonal to the axis of 2 axes, 2 axes The 6-axis axis, the 4-axis axis, and the 6-axis axis are parallel to each other, and the 6-axis axis is orthogonal to the 5-axis axis and the 7-axis axis at the same point. A control device for an axis robot,
Two axes are rotated by π / 2 [rad] relative to the axis of one axis, and four axes are rotated in the direction of the installation surface so that the axis of five axes is parallel to the axis of one axis. A position / posture control means for rotating one axis by an arbitrary angle after taking a measurement posture by rotating the five axes so that the axis of the shaft is parallel to the installation surface;
The measuring plate attached to the 7-axis axis is positioned in a normal direction standing on a reference position set on the installation surface side before the position / posture control means rotates one axis. One end side of the measurement plate in a direction orthogonal to the axis of the seven axes is a first measurement point, and the position / posture control means is positioned in the normal direction at a position after the position / posture control means has rotated one axis. The other end side in the orthogonal direction as a second measurement point,
The first distance from the reference position to the first measurement point is L1, the second distance from the reference position to the second measurement point is L2, and the distance from the first measurement point to the second measurement point is M. , Where the difference between the first distance L1 and the second distance L2 is ΔL and the rotation angle of the seven axes is θ7 (the unit of the angle is [rad]), the error angle Δθ7 of the seven axes is expressed by the following equation:
Δθ7 = arctan (ΔL / M) −θ7
And a home position calibration unit that calibrates the home position of the 7 axes using the error angle Δθ7.

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