JP5531996B2 - 6-axis robot offset detection method - Google Patents

Description

  The present invention relates to a method for detecting an offset between axes of a six-axis robot that detects and corrects an offset between a first rotary joint having rotational axes in directions orthogonal to each other and second, third, and fifth rotary joints.

  When the 6-axis robot is given position data represented by fixed three-dimensional Cartesian coordinates, the 6-axis robot converts the position data into rotational joint angle data and moves the hand to the position indicated by the position data. It is configured. In this case, the link (arm) length, the angle between the rotation joint and the rotation axis of the next rotation joint (hereinafter referred to as the torsion angle), the link origin position and the motor origin due to machining errors or assembly errors of the robot components. If there is an error in the relationship with the position (hereinafter referred to as the motor origin position), or if the drive system bends (hereinafter simply referred to as bend) due to the additional torque acting on the drive system of each rotary joint, the position of the hand And the posture is displaced, and the absolute position accuracy is lowered.

  In order to improve the absolute position accuracy, various methods for correcting the rotation angle of the rotary joint in consideration of the above-described error and deflection have been considered so far. For example, Non-Patent Document 1 discloses a method of detecting an error regarding a link length and a twist angle and correcting the error. Patent Documents 1 to 4 disclose error detection and correction methods for the motor origin position. Regarding the deflection of the drive system, the load torque acting on the motor of each rotary joint is calculated from the mass of each link and the posture of each link, and further, the torsional deformation of the drive system is calculated from this load torque and the spring constant of the drive system. There is known a method of correcting the deflection of the drive system by obtaining an angle, obtaining a deflection angle of each link from the twist deformation angle, and obtaining a motor rotation angle that reduces the deflection angle of each link.

Japanese Patent Laid-Open No. 2003-220587 JP 2009-274186 A JP 2009-274187 A JP 2009-274188 A

Issued by the Japan Robot Industry Association Commissioned by the Ministry of International Trade and Industry, Institute of Industrial Science and Technology, 1997 Survey and research on standardization of intelligent robots for plants Result report Page 52 4.3.2.3 Paired-even identification method

  The inventor obtained the link length error, the torsion angle error, the motor origin position error, the deflection of the drive system using the above method for the 6-axis robot, and after correcting the rotation angle of each rotary joint from the results, An experiment was conducted to determine whether the hand moves to the position indicated in the position data. However, the result of this experiment did not satisfy the absolute position accuracy originally planned by the inventor. The inventor considered that the cause of the insufficient position accuracy was caused by errors other than link length error, torsion angle error, motor origin position error, and drive system deflection, and presumed that this was due to an offset error between axes.

  When the positions of the second, third, and fifth rotary joints after assembly are shifted from the normal positions in the direction of the rotation center line, the amount of shift is calculated as the second, third, and third positions relative to the rotation center line of the first rotation joint. 5 is represented by a deviation amount in the direction of the rotation center line of each rotary joint, and this deviation is referred to as the above-described offset between axes.

  If the second, third, and fifth rotary joints deviate from their normal positions due to processing errors and assembly errors of the robot components, the design origin of the coordinates of the second, third, and fifth links The relationship between the position and the rotation axis of each of the second, third, and fifth rotary joints is shifted, and as a result, the robot hand is shifted from the position represented by the position data by the offset between the axes. become. In addition, the deviation from the normal position of each of the second, third, and fifth rotary joints is corrected as a link length error.

However, at present, no proposal has been made on a method for measuring the offset between the axes and correcting the offset.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for measuring a deviation amount of an inter-axis offset in a 6-axis robot and correcting it, thereby improving the absolute position accuracy of the robot. There is.

(Claim 1)
In the first aspect of the present invention, first, a measurement point is provided at the tip of the robot arm, the robot arm is rotated around the rotation axis of the first rotary joint, and three or more positions on the rotation locus of the measurement point are set to 3 Measured by the dimension measurement means, and from this measurement result, the position of the rotation center of the measurement point and the normal of the plane including a plurality of positions on the rotation locus of the measurement point are obtained. A straight line parallel to the normal line passing through the Z axis, a reference line passing through the origin and orthogonal to the Z axis as an X axis, and a straight line passing through the origin and perpendicular to both the Z and X axes as a reference Define coordinates.

  Next, when any plural positions are selected on an arbitrary plane including the Z axis extended from the Z axis of the reference coordinates, the plural positions are set as movement target positions, and the hand is moved to the movement target position. The first position error of the motor driving the first to sixth links via the first to sixth drive systems including the rotation axes of the first to sixth rotation joints, The position error of the hand is not caused by the bending error of each rotation drive system 6, the position error due to the length error of each of the first to sixth links, and the angle error between the rotation axis of the next rotation joint and the next rotation joint. After performing the correction process, by rotating the rotation shaft of at least one of the second, third, and fifth rotation joints, the hand is moved to a plurality of movement target positions, and measurement is performed at each movement target position. The point position is measured by a three-dimensional measuring means, and the measured measurement is performed. Coordinate converting multiple position of a point to a position on the reference coordinate.

Thereafter, XY coordinate values on the reference coordinates at a plurality of measurement points are obtained, a plurality of XY coordinate values of the obtained measurement points are plotted on the XY plane of the reference coordinates, and a line segment connecting these plotted points is obtained. A measurement-dependent line segment is obtained, and the length of a perpendicular line drawn from the origin of the reference coordinates on a straight line obtained by extending the measurement-dependent line segment is obtained as a deviation amount. This deviation amount is the total offset amount between the axes of the second, third, and fifth rotary joints.
The absolute position accuracy can be improved by correcting the DH parameter, for example, based on the offset amount between the axes obtained as described above.

(Claim 2)
According to a second aspect of the present invention, in the first aspect, an arbitrary plurality of positions on an arbitrary plane including the Z axis extending from the Z axis of the reference coordinates are defined as the movement target positions, and the movement target positions on the one plane are determined. The movement of the hand to each of the above is performed on two planes extending in the opposite directions from the Z axis of the reference coordinate, and from the plane extending in one direction from the Z axis to the plane extending in the opposite direction. The hand movement is performed by reversing the robot arm by rotating the rotation axis of at least one of the second, third, and fifth rotation joints with the rotation axis of the first rotation joint fixed. It is characterized by.

The measurement dependence line segment that connects the positions of the measurement points when moving the hand to one of the multiple planes on one plane and the robot arm is inverted to move the hand to any multiple positions on the other plane The measurement-dependent line segment formed by connecting the positions of the measurement points when the is moved is a saddle located on a straight line. When not positioned on a straight line, a method for setting reference coordinates, a motor origin position error, deflection of each of the first to sixth rotary drive systems, or a length error of each of the first to sixth links Therefore, it is considered that there was an error in the technique for preventing the position error of the hand from occurring.
For this reason, according to the invention of claim 2, it is possible to confirm whether or not the offset amount between the axes is correctly obtained.

(Claim 3)
The invention of claim 3 is to move the hand to any of a plurality of movement target positions on the reference coordinate instead of the operation until determining the inter-axis offset amount after determining the reference coordinate in claim 1. Error of the origin position of each motor, deflection of each of the first to sixth rotation drive systems, length error of each of the first to sixth links, and the rotation axis between the rotation joint and the next rotation joint. The correction center line is corrected so that the position error of the hand does not occur due to the angle error, and the rotation center line of the rotation axis of the fifth rotation joint is the rotation center line of the rotation axis of each of the second and third rotation joints. While maintaining the parallel state, by rotating at least one rotation shaft of the first rotation joint and the second, third, and fifth rotation joints, the hand is moved to a plurality of movement target positions, and each movement is performed. Measure the position of the measurement point at the target position with the 3D measuring means. The coordinate of the measurement point measured at each movement target position is transformed to the position on the reference coordinate to obtain the coordinate value on the reference coordinate, and for each movement target position, the XY coordinates of the movement target position on the XY plane of the reference coordinate Plot the value and the XY coordinate value of the measurement point, move the length of the line segment from the origin of the reference coordinate to the movement target position on the XY plane as the target position radius, and move from the measurement point on the XY plane to the origin of the reference coordinate The length of the vertical line drawn down to the straight line passing through the target position is the offset error component, and for each moving target position, the relationship between the target position radius and the offset error component is calculated, and the target position radius is set on one of the two orthogonal axes. When plotting the offset error component on the other axis and plotting the straight line passing through these plotted points as the error line, the length of the perpendicular drawn from the origin of the graph to the error line is taken as the amount of deviation. Because, characterized in that the inter-axis offset amount of the sum of the calculated deviation amount the 2,3,5 rotation joint.
Even if it does in this way, the effect similar to Claim 1 can be acquired.

(Claim 4)
According to a fourth aspect of the present invention, both the forward bending posture of the robot arm and the backward bending posture in which the robot arm is inverted from the forward bending posture are performed.
By doing so, when plotting the relationship between the target position radius and the offset error component for each moving target position on the graph, the plotted points are positioned in a straight line between the forward bending position and the backward bending position. Whether or not the inter-axis offset is correctly obtained can be confirmed in the same manner as in the second aspect.

(Claim 5)
The invention of claim 5 deals with a case where it is difficult to accurately detect the position of the hand and provide the measurement point on the hand.
In the fifth aspect, the measurement point is provided at a position away from the rotation center axis of the sixth link so as to operate integrally with the sixth link. The reference coordinates are set by rotating the first link to an arbitrary angular position of 3 or more while holding the robot arm in an arbitrary posture, rotating the sixth link at each angular position, Three or more different positions on the rotation trajectory of the measurement point that rotates integrally are measured by the three-dimensional measuring means, and the measurement point on the rotation trajectory of the sixth link measured at each angular position of the first link is measured. The rotation center position of the measurement point at each angular position is obtained from a plurality of three or more positions, and the position of the rotation center of the measurement point is set as a virtual hand position for reference coordinate setting, and the obtained three or more virtual hand positions for reference coordinate setting are obtained. To obtain the center position of a circle passing through these reference coordinate setting virtual hand positions and the normal line of the plane including three or more reference coordinate setting virtual hand positions, and the center of the obtained circle is the origin and the origin is The normal through A reference coordinate is defined with a parallel straight line as the Z axis, an arbitrary straight line passing through the origin and orthogonal to the Z axis as an X axis, and a straight line passing through the origin and perpendicular to both the Z and X axes as the Y axis. .

  Then, when a plurality of arbitrary positions on an arbitrary plane extending from the Z axis of the reference coordinates are set as movement target positions and the hand is moved to each of the movement target positions on the one plane, Due to the origin position error of each motor, the deflection of each of the first to sixth rotation drive systems, the length error of each of the first to sixth links, and the error in the angle between the rotation joint and the rotation axis of the next rotation joint After performing correction processing so as not to cause a hand position error, the rotation center line of the rotation axis of the fifth rotation joint is in parallel with the rotation center lines of the rotation axes of the second rotation joint and the third rotation joint. The hand is moved to each of a plurality of movement target positions by rotating the rotation shaft of at least one of the second, third, and fifth rotation joints while being held, and the sixth link is provided at each movement target position. To rotate the sixth phosphorus The three or more different positions on the rotation locus of the measurement point rotated by the rotation of the three points are measured by the three-dimensional measuring means, and 3 on the rotation locus of the measurement point by the rotation of the sixth link measured at each movement target position. The rotation center position of the measurement point is obtained from the above positions, and this is used as the virtual hand position for offset calculation. These virtual hand positions for offset calculation are coordinate-converted to positions on the reference coordinates, and a plurality of virtual hands for offset calculation are obtained. The XY coordinate value on the reference coordinate of the position is obtained, the XY coordinate value of the obtained virtual hand position for offset calculation is plotted on the XY plane of the reference coordinate, and a line segment connecting these plotted points is defined as a measurement dependent line segment. The length of the perpendicular drawn from the origin of the reference coordinates to the straight line obtained by extending the measurement dependent line segment is obtained as a deviation amount, and the obtained deviation amount is calculated as the total inter-axis off of the second, third, and fifth rotary joints. Characterized by the Tsu bet amount.

(Claim 6)
The invention of claim 6 is the robot according to claim 5, wherein the robot arm is reversed and moved to a movement target position on one plane opposite to the movement target position on one plane. It can be confirmed whether or not is correctly obtained.

(Claim 7)
According to a seventh aspect of the present invention, in place of the operation until the inter-axis offset amount is obtained after determining the reference coordinates in the fifth aspect, the hand is moved to a plurality of arbitrary movement target positions of the reference coordinates. Error of the above-mentioned motor origin position, bending of each of the first to sixth rotation drive systems, length error of each of the first to sixth links, and between the rotation axis of the rotation joint and the next rotation joint After performing a correction process so that a position error of the hand due to an angle error does not occur, the rotation center line of the rotation axis of the fifth rotation joint is parallel to the rotation center line of the rotation axis of each of the second and third rotation joints. By rotating the rotation shafts of at least two of the first rotation joint and the second, third, and fifth rotation joints while maintaining this state, the hand is rotated with the rotation shaft of the sixth rotation joint. The rotation center line is parallel to the rotation center line of the rotation axis of the first rotation joint The three or more different positions on the rotation trajectory of the measurement point rotated by rotating the sixth link at each movement target position and rotating the sixth link at each movement target position. The rotation center position of the measurement point is obtained from a plurality of positions on the rotation locus of the measurement point measured by the three-dimensional measurement means and measured at each movement target position, and this is used as the virtual hand position for offset calculation. The coordinates of the virtual hand position for offset calculation at the position are transformed to the position on the reference coordinate, the coordinate values on the reference coordinate of the plurality of virtual hand positions for offset calculation are obtained, and for each movement target position on the XY plane of the reference coordinate Plot the XY coordinate value of the movement target position and the XY coordinate value of the offset calculation virtual hand position, and draw a line from the origin of the reference coordinates to the movement target position on the XY plane. And the length of the perpendicular to the straight line passing through the origin of the reference coordinates and the moving target position on the XY plane from the virtual hand position for offset calculation on the XY plane as an offset error component, For each movement target position, the relationship between the target position radius and the offset error component is plotted on a graph with the movement target position radius on one of the two orthogonal axes and the offset error component on the other axis. When the straight line connecting the points is defined as the error straight line, the length of the perpendicular line drawn from the origin of the graph to the error straight line is obtained as a deviation amount, and the obtained deviation amount is the total axis of the second, third, and fifth rotary joints. This is characterized in that the amount of offset is set as the intermediate offset amount.

(Claim 8)
The invention of claim 8 is characterized in that, in claim 7, the operation of moving the hand to a plurality of arbitrary movement target positions of the reference coordinates is performed in both the forward bending posture and the backward bending posture of the robot arm.
By doing so, when plotting the relationship between the target position radius and the offset error component for each moving target position on the graph, the plotted points are positioned in a straight line between the forward bending position and the backward bending position. It can be confirmed whether or not the offset between the axes is correctly obtained depending on whether or not to do so.

The perspective view of the robot apparatus which shows one Embodiment of this invention Sectional view showing the outline of the rotary joint Side view of the robot with the rotation axis of each rotary joint set to the origin position Perspective view showing coordinates set for each link Table showing DH parameters Table showing specific values of DH parameters Block diagram showing the controller Perspective view of flange part Process diagram showing the procedure of the present invention Perspective view for explaining setting of reference coordinates Explanatory drawing of deflection of rotary drive system Perspective view showing the movement target position Side view showing the forward bending state of the robot Side view showing back-bending state of robot The figure which shows the simultaneous conversion matrix for converting a camera coordinate into a reference coordinate Explanatory drawing for obtaining the offset amount between axes The figure which shows the 2nd Embodiment of this invention Explanatory drawing for obtaining the offset amount between axes The perspective view of the flange part which shows the 3rd Embodiment of this invention Perspective view for explaining setting of reference coordinates Side view showing the flange position at the target position

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a 6-axis vertical multi-rotation joint type robot apparatus 1. The robot apparatus 1 includes a 6-axis vertical articulated robot (hereinafter simply referred to as a robot) 2, a control apparatus (robot control means) 3 that controls the operation of the robot 2, and a robot 2 connected to the control apparatus 3. Is provided with a teaching pendant (manual operation means) 4.

  The robot 2 includes a shoulder (first link) 7, a lower arm (second link) 8, a first arm constituting a robot arm 6 with respect to a base (base link) 5 fixed to an installation surface such as a factory floor. The upper arm (third link) 9, the second upper arm (fourth link) 10, the wrist arm (fifth link) 11, and the flange (first link) 12 are connected to the first to sixth rotary joints J1. To J6 (not shown in FIG. 1) are sequentially connected.

  That is, the shoulder 7 is connected to the base 5 by the first rotary joint J1 so as to be pivotable in the horizontal direction around the first axis Lc-1, and the lower arm 8 is connected to the tip of the shoulder 7 by the second rotary joint J2. The first upper arm 9 is supported so as to be pivotable in the vertical (vertical) direction around the two axes Lc-2, and the first upper arm 9 is vertically moved around the third axis Lc-3 by the third rotary joint J3 at the tip of the lower arm 8. The second upper arm 10 is supported so as to be rotatable about the fourth axis Lc-4 by the fourth rotary joint J4 at the distal end portion of the first upper arm 9, and the wrist arm 11 is supported. Is supported at the tip of the second upper arm 10 by a fifth rotary joint J5 so as to be pivotable in the vertical direction about the fifth axis Lc-5, and the flange 12 is supported on the wrist arm 11 by a sixth rotary joint J6. Supports rotation by twisting around the axis Lc-6 It is.

  The outline of the first to sixth rotary joints J1 to J6 is shown in FIG. As shown in FIG. 2, the rotary joints J <b> 1 to J <b> 6 of each of the links 7 to 12 include a rotary shaft 14 that is rotatably supported by a previous-stage link via a bearing 13, and the next-stage link is connected to the rotary shaft 14. They are connected directly or via a joint material. The rotary shaft 14 is rotationally driven by a servo motor 15 as a drive source fixed to the previous-stage link via a speed reducer, for example, a gear speed reducer 16, and the rotation of the rotary shaft 14 causes the next-stage link to turn or twist. It is designed to rotate.

  Here, the first axis Lc-1 to the sixth axis Lc-6 correspond to the rotation center line Lc of the rotary shaft 14 of each of the first to sixth rotary joints J1 to J6. The directivity directions of the first axis Lc-1 to the sixth axis Lc-6 are as follows. That is, the first axis Lc-1 that is the rotation center of the shoulder 7 is orthogonal to the installation surface, and the second axis Lc-2 that is the rotation center of the lower arm 8 is parallel to the direction orthogonal to the first axis Lc-1. That is, assuming that the base 5 is installed on the floor of a factory, for example, the first axis Lc-1 is set to be perpendicular (vertical) to the installation floor and the second axis Lc-2 is set to be horizontal. The third axis Lc-3 that is the rotation center of the first upper arm 9 is parallel or horizontal to the second axis Lc-2, and the fourth axis Lc-4 that is the rotation center of the second upper arm 10. Is parallel to the direction orthogonal to the third axis Lc-3, the fifth axis Lc-5, which is the rotation center of the wrist arm 11, is orthogonal to the fourth axis Lc-4, and the sixth axis Lc, which is the rotation center of the flange 12. -6 is defined in a direction orthogonal to the fifth axis Lc-5.

  When the shoulder 7, the lower arm 8, the first upper arm 9, the second upper arm 10, the wrist arm 11, and the servo motor 15 that drives each rotary shaft 14 of the flange 12 are at the origin position, the shoulder 7, lower The arm 8, the first upper arm 9, the second upper arm 10, the wrist arm 11 and the flange 12 are at the origin position. Here, when the shoulder 7, the lower arm 8, the first upper arm 9, the second upper arm 10, the wrist arm 11 and the flange 12 are all at the origin position, the robot arm 6 is vertical as shown in FIG. The posture is upward (the lower arm 8, the first upper arm 9, the second upper arm 10, and the wrist arm 11 are vertical). Then, each servo motor 15 rotates in the positive (plus) direction and the reverse (minus) direction from the origin position, so that the shoulder 7, the lower arm 8, the first upper arm 9, the second upper arm 10, and the wrist arm. 11 and the flange 12 also rotate in the positive (plus) direction and the reverse (minus) direction from the origin position.

  As shown in FIG. 4, three-dimensional coordinates R1 to R6 are defined for the shoulder 7, the lower arm 8, the first upper arm 9, the second upper arm 10, the wrist arm 11 and the flange 12, respectively. . The origins O1 to O6 of these coordinates R1 to R6 are the first axis Lc that is the rotation center line of the shoulder 7, the lower arm 8, the first upper arm 9, the second upper arm 10, the wrist arm 11 and the flange 12. -1 to the sixth axis Lc-6 are determined at predetermined positions, and the Z1 to Z6 axes that are the Z axes of the coordinates R1 to R6 coincide with the first axis Lc-1 to the sixth axis Lc-6. .

  In addition, among the coordinates R1 to R6, the X1 axis that is the X axis of the coordinate R1 of the shoulder 7 is horizontal, and a common perpendicular line (shown by a line in FIG. 1) of the first axis Lc-1 and the second axis Lc-2. .), The Y1 axis, which is the Y axis, is horizontal, and is determined in the direction determined by the outer product of the vectors of the Z1 axis and the Y1 axis (a direction orthogonal to both the Z1 axis and the Y1 axis). ing. The X2 to X6 axes that are the remaining X coordinates of R2 to R6 are coordinates in a state where the lower arm 8, the first upper arm 9, the second upper arm 10, the wrist arm 11 and the flange 12 are moved to the origin position. R1 is defined in a direction parallel to the X1 axis, and Y2 to Y6 axes, which are Y axes, are determined in a direction obtained by an outer product of vectors of Z2 to Z6 axes and Y2 to Y6 axes (see FIG. 4). . In addition, the plus directions of the X1 to X6 axes, the Y1 to Y6 axes, and the Z1 to Z6 axes are directions indicated by arrows in FIG.

  Coordinates R0 and Rf are also defined on the tip surface of the flange 12 which is the tip of the base 5 and the robot arm 6. While the coordinates R1 to R6 change positions and orientations with the rotation of the shoulder 7, the lower arm 8, the first upper arm 9, the second upper arm 10, the wrist arm 11 and the flange 12, the base A coordinate R0 of 5 is immobile and is a robot coordinate. The origin O0 of the robot coordinate R0 is located on the first axis Lc-1 that is the rotation center line of the shoulder 7, and in this embodiment is determined at a position that coincides with the origin O1 of the coordinate R1. Further, the Z0 axis that is the Z axis coincides with the first axis Lc-1, and the X0 axis that is the X axis and the Y0 axis that is the Y axis are the coordinates R1 of the shoulder 7 when the shoulder 7 is at the origin position. It corresponds to the X1 axis and the Y1 axis.

  The coordinate Rf of the front end surface of the flange 12 is the hand coordinate, and the origin Of is the intersection of the sixth axis Lc-6 and the front end surface of the flange 12, that is, the front end forming the circle of the flange 12 as shown in FIG. The Zf axis that is the Z axis coincides with the sixth axis Lc-6, and the Xf axis that is the X axis and the Yf axis that is the Y axis are X6 of the coordinate R6 of the flange 12. It is determined in parallel with the axis and the Y6 axis. The center P of the front end surface of the flange 12 is set to the hand that is the front end of the robot arm 6.

  Among the coordinates R0 to R6 and Rf described above, the origins O1 to O6 and Of of the coordinates R1 to R6 and Rf excluding the robot coordinate R0 are one plane including the X1 axis and the Z1 axis of the coordinate R1 in this embodiment. When (vertical plane) is assumed, it is located on this one plane.

  The mutual relationship between the coordinates R0 to R6 and Rf defined as described above is indicated by a well-known DH parameter. FIG. 5 summarizes the DH parameters in a table. For example, for the J1 row, the coordinate R1 is translated a1 in the X1 axis direction, not translated in the Y1 axis direction, and d1 parallel in the Z1 axis direction. After the movement, if the X1 axis is rotated about the twist angle −π / 2, the coordinate R2 is obtained. For example, for the J6 line, the coordinate R6 is set in the X6 axis direction and the Y6 axis direction. It shows that the hand coordinates Rf can be obtained by performing d6 translation in the Z6 axis direction without translation. The relationship between the robot coordinate R0 and the coordinate R1 of the shoulder 7 is not shown in FIG. 5 because the coordinate R1 coincides with the robot coordinate R0 when the shoulder 7 is at the origin position. FIG. 6 shows specific numerical examples of a, b, and d.

  As shown in FIG. 7, the control device 3 includes a CPU (control means) 17, a drive circuit (drive means) 18, and a position detection circuit (position detection means) 19. The CPU 17 is connected to a ROM 20 for storing various data such as a robot language and DH parameters for creating a system program and an operation program for the entire robot 2, and a RAM 21 for storing the operation program for the robot 2. The teaching pendant 4 used when performing work or the like is connected. As shown in FIG. 1, the teaching pendant 4 includes various operation units 4a and a display 4b made of liquid crystal.

  The position detection circuit 19 is connected to a rotary encoder 22 as a rotation sensor coupled to a rotation shaft (not shown) of each servo motor 15. The position detection circuit 19 detects the rotation angles of the shoulder 7, the lower arm 8, the first upper arm 9, the second upper arm 10, the wrist arm 11, and the flange 12 based on the rotation angle detection information of each rotary encoder 22. Then, the rotation angle detection information is given to the CPU 17.

  When the CPU 17 is given the position of the hand on the robot coordinate R0 (the position of the origin Of of the hand coordinate Rf) and the posture (the direction of the Xf axis and the Yf axis of the hand coordinate Rf), the CPU 17 A well-known calculation method of inverse kinematics using a Jacobian matrix is used to calculate the rotation angles of the shoulder 7, the lower arm 8, the first upper arm 9, the second upper arm 10, the wrist arm 11 and the flange 12 that take a posture. Ask for. Conversely, when the rotation angles of the shoulder 7, the lower arm 8, the first upper arm 9, the second upper arm 10, the wrist arm 11 and the flange 12 are given, the order in which coordinate conversion is used from these rotation angles. The position and posture of the hand on the robot coordinate R0 can be obtained by a well-known calculation method of kinematics. As is well known, the DH parameter indicating the mutual relationship between the coordinates R0 to R6 and Rf is used for the calculation by the inverse kinematics and forward kinematics calculation methods.

  When the CPU 17 obtains the target position of the hand from the operation program, the shoulder 7, the lower arm 8, the first upper arm 9, the second upper arm 10, the wrist arm 11 and the flange 12 are obtained from the target position of the hand. A target operation angle is calculated, and an operation command based on the target operation angle is given to the drive circuit 18. The drive circuit 18 drives each servo motor 15 based on the given operation command. At this time, the CPU 17 uses the rotation angle detection information of the shoulder 7, the lower arm 8, the first upper arm 9, the second upper arm 10, the wrist arm 11 and the flange 12 given from the position detection circuit 19 as feedback information. The servo motor 15 is feedback controlled.

  By the way, as described above, the shoulder 7, the lower arm 8, the first upper arm 9, the second upper arm 10, the wrist arm 11 and the flange 12, the coordinates R1 to R6, and the origins O1 to O6 of the hand coordinates Rf. , Of are present on a vertical plane including the X1 axis and the Z1 axis of the coordinate R1 of the shoulder 7. Therefore, if the robot 2 is assembled with high precision, the center P of the tip surface of the flange 12 that is the hand coincides with the origin Of of the hand coordinates Rf, and the shoulder 7, the lower arm 8, the first upper arm 9, If the second upper arm 10, the wrist arm 11 and the flange 12 are rotated by the target operation angle, the hand is correctly moved to the target position.

  However, the position of each rotary shaft 14 of the rotary joints J2, J3, J5 of the lower arm 8, the first upper arm 9, and the wrist arm 11 due to manufacturing errors and assembly errors of the components of the robot 2 is the second axis Lc. -2, the third axis Lc-3, and the fifth axis Lc-5 are displaced in the direction of the normal position and an error (inter-axis offset) occurs, the actual hand (the center P of the front end surface of the flange 12) ) Is deviated from the origin of the designed hand coordinates Rf.

  Then, even if the shoulder 7, the lower arm 8, the first upper arm 9, the second upper arm 10, the wrist arm 11 and the flange 12 are rotated by the target operating angle, the actual movement position of the hand is determined as the rotational joint J2. , J3 by the sum of the offsets between the axes 14 (when the fifth axis Lc-5 is vertical), or by the sum of the offsets between the axes 14 of the rotary joints J2, J3, J5 ( When the fifth axis Lc-5 is horizontal), the fifth axis Lc-5 is shifted in the horizontal direction from the target position.

  Since the distance from the rotation center line Lc-5 to the hand is short, it is considered that the offset between the axes of the rotary joint J5 alone is small, and the sum of the offsets between the rotary axes 14 of the rotary joints J2 and J3 and the rotary joint It is considered that there is almost no difference from the sum of the offsets between the axes of J2, J3, and J5.

  The method of the present invention estimates the sum of the offsets between the rotary shafts 14 of the rotary joints J2, J3, and J5, corrects the DH parameter by the estimated offset between axes, and sets the actual movement position of the hand to the target position. Try to get as close as possible.

  In the method of the present invention, when the teaching pendant 4 is operated to move the hand to a plurality of target positions, the actual movement position of the hand is measured by the three-dimensional measuring instrument (three-dimensional measuring means) 23 shown in FIG. A deviation amount from the target position is obtained, and an offset between the axes is estimated from the deviation amount. In this case, the deviation between the actual movement position of the hand and the target position is caused by factors other than the offset between the axes, that is, the deflection of the rotary drive system of each rotary joint J1 to J6, the origin position error of each servo motor 15, and each link 7 This is also caused by a length error of -12 and a torsional angle error between the rotary shafts 14 of the rotary joints J1 to J6, so that it is necessary to perform correction processing in advance so as not to cause a position error due to these factors.

  The three-dimensional measuring instrument 23 includes, for example, a three-dimensional measuring instrument (for example, Toyo Technica Co., Ltd .; robot calibration ROCAL system) provided with three CCD cameras. Note that the three-dimensional measuring instrument 23 may be a laser tracker or the like. In order to detect the position of the hand of the robot arm 6 by the three-dimensional measuring device 23, a light emitting diode 24 as a measurement point is provided at the center P of the distal end surface of the flange 12, as shown in FIG. In this case, the flange 12 has a center hole 12a formed in the flange 12, and the center P of the front end surface of the flange 12 exists on the center line of the center hole 12a. The light emitting diode 24 is correctly positioned at the center (hand) P of the front end surface of the flange 12 so as to be flush with the front end surface of the flange 12. Note that a small hole 12b is formed in the flange 12 at a position separated from the center hole 12a, and a straight line connecting the center points of the center hole 12a and the small hole 12b is determined to be the Xf axis of the hand coordinate Rf. It has been.

  The measurement position of the light emitting diode 24 by the three-dimensional measuring instrument 23 is indicated by a position on the three-dimensional coordinates (hereinafter referred to as camera coordinates) Rc preset in the three-dimensional measuring instrument 23 by the measurement control device 25 formed of a personal computer. . The distance represented by one scale of the camera coordinates Rc is determined to be equal to the distance when the hand moves by a distance corresponding to one scale of the robot coordinates R0. Therefore, the length of one scale of the robot coordinates R0 and the length of one scale of the camera coordinates Rc represent the same distance.

  Now, the method of the present invention is performed according to the procedure shown in FIG. First, the position of the robot coordinate R0 on the camera coordinate Rc and the directions of the X0 axis, the Y0 axis, and the Z0 axis of the robot coordinate R0 are unknown. Therefore, in this embodiment, the reference coordinate Rb is set on the camera coordinate Rc as a coordinate to replace the robot coordinate R0 (step S1 in FIG. 9). This reference coordinate Rb is set using the teaching pendant 4.

  Here, the function of the teaching pendant 4 will be described. The teaching pendant 4 includes a shoulder 7, a lower arm 8, a first upper arm 9, a second upper arm 10, a wrist arm 11, and a servo motor 15 for the flange 12. The shoulder 7, the lower arm 8, the first upper arm 9, the second upper arm 10, the wrist arm 11, and the flange 12 are rotated in desired forward and reverse directions from their respective origin positions by individually rotating by a desired angle. It is configured to be able to rotate by an angle.

  Further, the teaching pendant 4 can designate the position and orientation of the hand with the robot coordinate R0. When the position and orientation on the robot coordinate R0 is designated with the teaching pendant 4, the CPU 17 of the robot apparatus 1 The rotation angles of the shoulder 7, the lower arm 8, the first upper arm 9, the second upper arm 10, the wrist arm 11 and the flange 12 are calculated, and each servo motor 15 is driven so as to be the rotation angle. As a result, the hand moves so as to take the designated position and posture.

  Further, when it is desired to know the position and posture of the hand of the current robot arm 6, if an operation to that effect is performed, the CPU 17 causes the shoulder 7, the lower arm 8, the first upper arm 9, the second upper arm 10, and the wrist. The position and posture of the hand are calculated from the rotation angles of the arm 11 and the flange 12, and the display 4a of the teaching pendant 4 displays the position and posture of the hand on the robot coordinate R0.

  In order to set the reference coordinate Rb on the camera coordinate Rc, first, the operation unit 4a of the teaching pendant 4 is operated, and the fifth axis Lc-5 that is the rotation center line of the rotation shaft 14 of the fifth rotation joint J5 is determined. The robot arm 6 is maintained in a state parallel to the second axis Lc-2 and the third axis Lc-3 that are the rotation center lines of the rotary shaft 14 of the second and third rotary joints J2 and J3, that is, in a horizontal state. To any position. The posture of the robot arm 6 at this time is such a posture that the light emitting diode 24 moves on one rotation locus when the robot arm 6 is rotated about the first axis Lc-1, that is, the light emitting diode 24 is In this embodiment, as shown in FIG. 13, the lower arm 8 and the first upper arm 9 are rotated from the vertically upward state in FIG. The flange 12 is held obliquely downward (the forward bending posture in which the robot arm 6 falls to the front side of the shoulder 7 (the positive side of the X0 axis)). With this posture, the shoulder 7 is centered on the first axis Lc-1 until the shoulder 7 reaches a desired angle, preferably a position of plus 90 °, a position of 0 ° (origin position), and a position of minus 90 °. Rotate 180 degrees or more including

  Then, the light emitting diode 24 as a reference coordinate setting measurement point follows a circular rotation locus E around the first axis Lc-1 as shown in FIG. The positions on the rotation locus E are measured at a plurality of positions d1, d2,. The measurement control unit 25 obtains the position Ob of the rotation center of the light emitting diode 24 from the plurality of positions d1, d2,... Dn on the rotation locus E of the light emitting diode 24 measured by the three-dimensional measuring instrument 23 by the least square method. Then, a normal Lv of one plane including the rotation locus E of the light emitting diode 24 is obtained. The rotation center position Ob is defined as the origin of the reference coordinate Rb, and a straight line passing through the origin Ob and parallel to the normal Lv (in the same direction) is defined as the Zb axis (Z axis) of the reference coordinate Rb.

  Further, an arbitrary straight line passing through the origin Ob and orthogonal to the Zb axis, for example, a straight line connecting the position P0 of the light emitting diode 24 and the origin Ob when the shoulder 7 is rotated to the origin position is the Xb axis of the reference coordinate Rb. (X axis), a straight line orthogonal to both axes is obtained from the outer product of the Zb axis and Xb axis vectors, and the straight line is defined as the Yb axis (Y axis) of the reference coordinate Rb. The length of one scale on the reference coordinate Rb is determined to be the same as the length of one scale on the camera coordinate Rc.

  As described above, the reference coordinate Rb is set on the camera coordinate Rc. In the reference coordinate Rb set in this way, the Zb axis is on the first axis Lc-1 and thus on the Z0 axis of the robot coordinate R0, and the XbYb plane is parallel to the X0Y0 plane. If there is no inter-axis offset, the Xb axis and Yb axis are parallel to the X0 axis and Y0 axis of the robot coordinate R0. However, when there is an offset between the axes, the position P0 of the light emitting diode 24 when the shoulder 7 is rotated to the origin position is shifted in the X0Y0 direction by the offset between the axes, so that the Xb axis and Yb axis are the X0 axis and Y0. It is not parallel to the axis but tilts according to the offset between the axes as shown in FIG. When the reference coordinate Rb is set, if the position of the hand is on the X0Y0 plane, the XbYb plane coincides with the X0Y0 plane.

  After setting the reference coordinates Rb, a vertical plane including the Zb axis is assumed, and a plurality of positions in the single plane are determined as movement target positions. Specifically, in this embodiment, as shown in FIGS. 10 and 12, an arbitrary extension line A1 extending from the Zb axis (origin b) is set on the XbYb plane of the reference coordinate Rb, and the Zb axis An extension line A2 extending in the direction opposite to the arbitrary extension line A1 is set. The one extension line A1 and the other extension line A2 become one straight line A passing through the Zb axis, and this straight line A is located in one plane including the Zb axis. The arbitrary extension line A1 is designated by an angle formed with the Xb axis. For example, in order to set a straight line with an angle formed with the Xb axis plus 30 °, the shoulder 7 is rotated plus 30 ° from the origin. In this embodiment, a plurality of such straight lines A are set (only one is shown in FIGS. 10 and 12), and one straight line A is parallel to the Xb axis.

  Then, arbitrary plural positions are selected on each of the extension lines A1 and A2. Therefore, arbitrary plural positions selected on the extension lines A1 and A2 exist in one vertical plane including the Zb axis. A plurality of arbitrarily selected positions are indicated by small white circles in FIG. As will be described later, the hand of the robot arm 6 is moved to a plurality of positions arbitrarily selected on each straight line A in order to obtain an offset between axes.

  Here, the plurality of positions selected on the straight line A are positions specified by the (Xb, Yb, Zb) coordinate values of the reference coordinates Rb, but the movement target position of the hand operated by the teaching pendant 4 is the robot coordinates R0. The (X0, Y0, Z0) coordinate value is specified. For this reason, it is necessary to obtain the relationship between the robot coordinate R0 and the reference coordinate Rb. In this embodiment, since the Zb axis coincides with the Z0 axis, the position of the light emitting diode 24 on the Z0 axis when the reference coordinate Rb is obtained is the position on the Z0 axis of the XbYb plane of the reference coordinate Rb (this position Is Za).

  As described above, the Xb axis and the Yb axis are inclined with respect to the X0 axis and the Y0 axis when there is an inter-axis offset, but the inclination angle is unknown. However, if there is no inter-axis offset, the Xb axis and Yb axis are parallel to the X0 axis and Y0 axis. Therefore, when there is no inter-axis offset, the robot coordinate R0 is translated to Za along the Z0 axis. And the reference coordinate Rb.

  Then, from the relationship between the reference coordinate Rb and the robot coordinate R0 when there is no offset between the axes, if the hand is moved by designating each of the movement target positions with the three-dimensional coordinate value at the robot coordinate R0, The actual movement position is shifted in the XbYb direction from the movement target position on the reference coordinate Rb obtained as described above in the XbYb direction. Therefore, the deviation amount of the axis offset is obtained from the deviation amount. It is something that can be done. Accordingly, in the following description, it is assumed that there is no offset between axes, the Zb axis of the reference coordinate Rb is on the Z0 axis of the robot coordinate R0, and the Xb axis and Yb axis are parallel to the robot coordinate X0 axis and Y0 axis.

  Prior to moving the hand of the robot arm 6 to a plurality of positions selected on the straight lines A1 and A2, errors other than the offset between axes (deflection of the rotational drive system, origin position error of the servo motor 15, twist) A process of eliminating the movement position error of the hand due to the angle error and the link length error is performed.

  First, the bending of the rotational drive system refers to bending in the twisting direction due to the transmission torque from the rotating shaft of the servo motor 15 to the rotating shaft 14 of the rotary joints J1 to J6 through the gear reduction device 16. It is assumed that the rotating shaft 14 does not bend in an arc shape in the axial direction. The deflection of the rotational drive system can be obtained from the torque acting on the rotational drive system and the spring constant of the rotational drive system. Among them, the spring constant is known in the robot 2, and its value is stored in advance in the ROM 20 of the control device 3. The torque acting on the rotational drive system is considered for the second axis Lc-2, the third axis Lc-3, and the fifth axis Lc-5 (the first axis Lc-2, the fourth axis Lc-3, the sixth axis Lc). -5 does not receive a large torque and does not cause bending that causes an absolute position error.)

  As shown in FIG. 11, the torque acting on the rotary drive system can be obtained by the product of the mass W of the link L supported by the rotary shaft 14 and the distance D from the rotary shaft 14 to the center of the link L. And when moving the hand of the robot arm 6 to the arbitrary plural positions selected on the straight line A, the fifth axis Lc-5 is held in parallel with the second and third axes Lc-2, Lc-3, for example, The shoulder 7, the second upper arm 10, the wrist arm 11, and the flange 12 are not rotated, but only the lower arm 8 and the first upper arm 9 are rotated to move the hand to an arbitrary plurality of positions. The rotation angles of the second upper arm 10, the lower arm 8, the first upper arm 9, the wrist arm 11 and the flange 12 when moving to the position are read from the teaching pendant 4, and the second axis Lc- 2, the torque acting on the third axis Lc-3 and the fifth axis Lc-5 is calculated, and the deflection (angle) α of these rotary drive systems is obtained (step S2 in FIG. 9).

  Then, the rotation angle of the servo motor 15 is increased or decreased by the obtained bending α of the rotational drive system so as to be equivalent to the case where no bending occurs. In other words, in FIG. 11, assuming that the position of the link indicated by the solid line is the movement target position when the rotation drive system is not considered to be the deflection, and the position indicated by the broken line is the actual movement position when the rotation drive system is deflected, the servo The rotation angle of the motor 15 is decreased by the deflection α. As a result, the link reaches the movement target position indicated by the solid line in a state where the rotational drive system is bent.

  The motor origin position error is detected by, for example, the methods disclosed in Patent Documents 1 to 4. Further, the twist angle error and the link length error are detected by the direction disclosed in Non-Patent Document 1, for example. The method of Non-Patent Document 1 measures the rotation trajectory of the hand when the robot arm 6 is rotated about each of the first axis Lc-1 to the sixth axis Lc-6 with a three-dimensional measuring instrument, The position of the center of rotation and the normal of one plane including the rotation locus are calculated. Since the length of each link is obtained from the position of the rotation center and the direction of each axis is obtained from the direction of the normal line, the link length error and the torsion angle error can be obtained from the length of the link and the axial direction. (Step S3 in FIG. 9).

  Then, the DH parameter is corrected based on the obtained motor origin position error, link length error and torsion angle error so that these errors do not appear as absolute position errors (step S4 in FIG. 9).

  After performing the above processing, the teaching pendant is operated, and first, the X1 axis of the coordinate R1 of the shoulder 7 is aligned with one desired extension line A1 among the plurality of extension lines. For this purpose, the shoulder 7 is rotated from the origin position by an angle formed by the Xb axis (same as the X0 axis) and the extension line A1 when there is no inter-axis offset. Accordingly, the hand can be moved to a plurality of movement target positions arranged on the straight lines A1 and A2 by rotating the rotary shafts 14 of the second rotary joint J2 and the third rotary joint J3.

  Therefore, by rotating only the rotary shaft 14 of the second rotary joint J2 and the third rotary joint J3, the fifth axis Lc-5 is parallel to the second and third axes Lc-2 and Lc-3, that is, horizontal. A plurality of movement targets arbitrarily selected on the straight lines A1 and A2 by rotating only the lower arm 8 (second axis LC-2) and the first upper arm 9 (third axis Lc-3). Move your hand to the position. At this time, the rotation angle of the servo motor 15 is adjusted according to the bending of the rotary drive system previously obtained for each movement target position.

  When the hand is moved to a plurality of movement target positions arbitrarily selected on the straight lines A1 and A2, the robot arm 6 moves the second, third, and fifth rotary joints J2, 3, and 5 as shown in FIG. By rotating at least the rotating shafts 14 of the second and third rotary joints J2 and J3 in one direction, the posture is bent forward from the shoulder 7 toward one side (forward bending posture) on one straight line A1. When the hand is moved to the movement target position and the hand is moved to the movement target position on the other extension line A2, the robot arm 6 has at least one of the second, third, and fifth rotary joints J2, 3, and 5. By rotating the rotary shafts 14 of the second and third rotary joints J2 and J3 in the other direction, as shown in FIG. 14, the posture is reversed and falls from the shoulder 7 to the other side (robot arm 6 Back-bending posture when the body fell to the rear side of shoulder 7 In moving the hand.

Then, each time the hand is moved to the movement target position, the position of the light emitting diode (offset measurement measurement point) 24 is measured by the three-dimensional measuring instrument 23 (step S5 in FIG. 9).
Since the position measured by the three-dimensional measuring instrument 23 is the position of the camera coordinate Rc, it is converted to the position of the reference coordinate Rb. This conversion is performed by the simultaneous conversion matrix shown in FIG. 15 (step S6 in FIG. 9).

  Thereafter, the error of each actual movement position with respect to the movement target position is determined by converting the Xb, Yb, and Zb coordinate values at the reference coordinate Rb (the Xb, Yb coordinate values of the movement target position are X0, Y0 on the robot coordinate R0). The Zb coordinate value is the same as the coordinate value, and is divided into an error in the Zb-axis direction and an error on the XbYb plane.

  FIG. 16 shows errors on the XbYb plane for a plurality of movement target positions arranged on the straight lines A1 and A2 that coincide with the Xb axis. Here, for simplification of explanation, it is assumed that the straight lines A1 and A2 are straight lines that coincide with the Xb axis. In FIG. 16, the white circle indicates the movement target position on the robot coordinate R0, the black circle indicates the movement target position on the reference coordinate Rb, and the x mark indicates the actual movement position of the hand.

  When moving the hand to the movement target position, pre-processing was performed so that no error occurred in the movement position due to bending of the rotation drive system, motor origin error, link length error, and torsion angle error. It is considered that the error with respect to the movement position is caused by the offset between the axes. The error caused by the offset between the axes is that the movement target position is on the X0 axis, and the actual movement position is shifted from the movement target position by the offset between the axes and is aligned on a straight line (until it is not aligned accurately on the straight line). Will also be distributed along a straight line). Therefore, a line segment connecting the actual movement positions of the movement target positions determined on the straight lines A1 and A2 is created on the XbYb plane, and the line segment is defined as a measurement dependent line segment B. When the shortest distance between the extended straight line Bb and the origin Ob (the length of the perpendicular line from Ob to Bb) is obtained, this shortest distance becomes the inter-axis offset F (step S7 in FIG. 9).

  In this case, when the robot arm 6 is bent forward and moved to the movement target position on the extension line A1, the measurement dependence line segment B connecting the actual movement positions and the robot arm 6 are bent backward on the extension line A2. If the measurement dependence line segment B connecting the actual movement positions when moving to the movement target position of the line is not a single straight line (including the fact that it is not aligned in the vicinity of a single straight line) Since it is considered that there was an inconvenience somewhere in the process, in this case, the process starts again from the first step S1. In this way, by setting the movement target position on the two extension lines A1 and A2, it becomes possible to detect a problem in implementation.

  Actually, the inter-axis offset F is obtained in the same manner as described above for the movement target position determined on the same straight line other than the straight lines A1 and A2 coincident with the Xb axis. Also in this case, the actual movement position of the hand should be aligned in a straight line.

  Similarly, the shortest distance from the origin Ob is also measured for the measurement-dependent straight line B formed by connecting the actual movement positions of the movement target positions determined on the straight line A other than the straight line A that coincides with the Xb axis. The shortest distance between each measurement-dependent straight line B and the origin Ob should be the same for any measurement-dependent straight line B, but in practice, it is often not always the same due to a measurement error or the like. In such a case, the average of the shortest distance between the measurement dependent straight line B and the origin Ob is obtained to obtain the offset between the axes. As a result, the offset between axes can be obtained more accurately.

  The inter-axis offset obtained as described above is the sum of the inter-axis offsets generated in the second axis Lc-2, the third axis Lc-3, and the fifth axis Lc-5, and it is analyzed which axis is the offset. Can not. For this reason, among the HD parameters shown in FIG. 5, the value of the offset between axes is added to any of the d columns of J2 and J3 or added separately to the d columns of J2 and J3. Since the fifth axis Lc-5 can take any angle from horizontal to vertical by the rotation of the fourth axis Lc-4, if the inter-axis offset is distributed to the column d of J5, the absolute position accuracy is reduced. I will let you. For this reason, the offset between axes is not distributed to the column d of J5.

  In order to check whether the absolute position accuracy has been improved by adding the value of the offset between axes in either the d column of J2 or J3 or in the d column of J2 or J3, the offset between axes is set. Using the added DH parameter, a plurality of target positions were determined on the Xb axis, and the hand was moved to the target position in the same manner as described above, and an experiment was performed to measure the actual movement position.

  As a result, the position error on the XbYb plane decreased from 0.67 mm to 0.17 mm. The position error in the Zb axis direction also decreased from 0.9 mm to 0.06 mm. From this, it can be said that the position error is reduced from 1.12 mm to 0.18 mm in the three-dimensional direction of XbYbZb.

  As described above, according to the present embodiment, the offset between the axes can be quantitatively grasped, and the DH parameter is corrected by the offset between the axes so that there is no error due to the offset between the axes, or the error does not occur as much as possible. The absolute position accuracy can be increased.

(Second Embodiment)
FIG. 17 shows a second embodiment of the present invention. In this embodiment, the reference coordinate Rb is obtained in the same manner as in the first embodiment, but the method of obtaining the offset amount between axes is different.
In this embodiment, when an arbitrary plurality of positions are set as movement target positions and the hand is moved to the plurality of positions, an inter-axis offset is obtained based on the difference between the movement target position and the actual movement position of the hand. It is a thing. That is, assuming that the inter-axis offset is “0”, an arbitrary plurality of positions on the reference coordinate Rb are selected as the movement target positions. Since the inter-axis offset is set to “0”, the Xb and Yb coordinate values on the reference coordinate Rb and the X0 and Y0 coordinate values on the robot coordinate R0 are the same.

  In FIG. 17, a plurality of positions selected as the movement target positions are indicated by black circles. Among these, the movement of the hand to the movement target position with the Xb coordinate value on the plus side (right side of the Yb axis) is performed in the forward bending posture of the robot arm 6 and to the movement target position on the minus side (left side of the Yb axis). The movement of the hand is assumed to be performed in a backward bending posture of the robot arm 6.

  As in the first embodiment, prior to moving the hand of the robot arm 6 to a plurality of selected movement target positions, each error other than the offset between axes (deflection of the rotational drive system, origin position of the servo motor 15). A process of eliminating the movement position error of the hand due to an error, a torsion angle error, and a link length error is performed.

  Thereafter, the hand is moved to a plurality of selected movement target positions. The movement at this time is performed by rotating the rotary shaft 14 of the second and third rotary joints J2 and J3 among the first rotary joint J1 and the second, third and fifth rotary joints J2, J3 and J5. In order to hold the fifth axis Lc-5 horizontally, the rotary shaft 14 of the fourth rotary joint J4 is not rotated. Then, the position of the light emitting diode 24 is measured by the three-dimensional measuring instrument 23 at each movement target position.

  Since the position measured by the three-dimensional measuring instrument 23 is the position of the camera coordinate Rc, it is converted to the position of the reference coordinate Rb. The measurement positions of the light emitting diodes 24 at the respective movement target positions are indicated by crosses in FIG.

  In order to obtain the offset between axes from the movement target position and the position of the light emitting diode 24, the XbYb coordinate value of the movement target position (same as the X0Y0 coordinate value) as shown by a black circle on the XbYb coordinate plane of the reference coordinate Rb as shown in FIG. And the measurement position of the light emitting diode 24 are plotted, the length of the line segment from the origin Ob to the movement target position is set as the target position radius D0, and the line is lowered from the measurement position of the light emitting diode 24 to a straight line passing through the origin Ob and the movement target position. Let the length of the vertical line be an offset error component M0. Then, as shown in FIG. 18, a graph is created with the target position radius D0 on the horizontal axis and the offset error component M0 on the vertical axis, and the target position radius D0 and offset error for each moving target position are created on this graph. A relationship with the component M0 is plotted, and a straight line passing through these plotted points is defined as an error straight line G. When a perpendicular is drawn from the origin of the graph to the error straight line G, the length of this perpendicular becomes the total inter-axis offset amount F of the second, third, and fifth rotary joints.

(Third embodiment)
19 to 21 show a third embodiment of the present invention. Hereinafter, parts different from the first embodiment will be described. In this embodiment, the light emitting diode 24 is not attached to the hand (the center of the front end surface of the flange 12), but at an arbitrary position radially away from the rotation center line Lc-6 of the sixth rotary joint J6. It is attached.

In this embodiment, as shown in FIG. 19, the support base 26 to which the light emitting diode 24 is attached is attached to the distal end surface of the flange 12 at an arbitrary position away from the center P.
In order to set the reference coordinate Rb on the camera coordinate Rc, first, the fifth axis Lc-5 that is the rotation center line of the rotation shaft 14 of the fifth rotation joint J5 is rotated by the second and third rotation joints J2 and J3. In a state parallel to the second axis Lc-2 and the third axis Lc-3 that are the rotation center lines of the shaft 14, that is, in a horizontal state, and the center P of the flange 12 extends in the horizontal direction from the first axis Lc-1. Hold in any distant position. In the present embodiment, the wrist arm 11 is held in a vertically downward posture as shown in FIG. And the shoulder 7 is rotated centering | focusing on the 1st axis | shaft Lc-1 with this attitude | position. The shoulder 7 is stopped at arbitrary angular positions in the middle of the rotation, and the flange 11 is rotated at the stop positions. Note that the posture of the wrist arm 11 is not particularly required to be vertically downward.

  Then, since the light emitting diode 24 also rotates integrally with the rotation of the flange 11, the camera coordinates Rc of the light emitting diode 24 by the three-dimensional measuring instrument 23 at any three or more different positions on the rotation locus of the light emitting diode 24. Measure the upper position.

  Then, the center of the rotation locus of the light emitting diode 24 is obtained from three or more positions on the rotation locus of the light emitting diode 24 measured at each stop angle position of the shoulder 7. The center C1, C2,... Cn of the rotation locus of the light emitting diode 24 at each stop angle position of the shoulder 7 is located on the rotation center line Lc-6 of the rotation shaft 14 of the sixth rotation joint J6, and a virtual hand for setting reference coordinates. It is considered as a position.

  Since these reference coordinate setting virtual hand positions C1, C2,... Cn are located on one circular locus, the center of a circle passing through the reference coordinate setting virtual hand positions C1, C2,. Then, a normal Lv of one plane including the circle is obtained. Then, the circle center Ob is defined as the origin of the reference coordinate Rb, and a straight line passing through the origin Ob and parallel to the normal Lv is defined as the Zb axis of the reference coordinate Rb.

  Further, an arbitrary straight line passing through the origin Ob and orthogonal to the Zb axis, for example, a straight line connecting the position Pc of the light emitting diode 24 and the origin Ob when the shoulder 7 is rotated to the origin position is the Xb axis of the reference coordinate Rb. (X axis), a straight line orthogonal to both axes is obtained from the outer product of the Zb axis and Xb axis vectors, and the straight line is defined as the Yb axis (Y axis) of the reference coordinate Rb. As described above, the reference coordinate Rb is set on the camera coordinate Rc.

  After setting the reference coordinate Rb, as in the first embodiment, a plurality of straight lines A including straight lines A1 and A2 are determined, and a plurality of arbitrary movement target positions are determined on the straight lines A1 and A2, respectively, to obtain an offset between axes. . Prior to this, processing for eliminating the movement position error of the hand due to each error other than the offset between axes (deflection of the rotational drive system, origin position error of the servo motor 15, torsion angle error, link length error) is performed.

  Next, the hand of the robot arm 6 is moved to the selected arbitrary plural positions. At this time, the wrist arm 11 may have any posture, but in this embodiment, as in the case of setting the reference coordinate Rb, as shown in FIG. 21, the Z6 axis of the flange coordinate R6 is vertically downward as shown in FIG. The rotary shafts 14 of the second, third, and fifth rotary joints J2, J3, and J5 are moved so as to move while maintaining a vertically downward posture (the sixth axis Lc-6 is parallel to the first axis Lc-1). It shall be rotated and moved to the movement target position.

  And the flange 11 is rotated in the state which moved the hand to each movement target position. Then, since the light emitting diode 24 also rotates integrally with the rotation of the flange 11, any three or more different positions on the rotation locus of the light emitting diode 24 are measured by the three-dimensional measuring instrument 23. Then, the center position (virtual hand position for offset calculation) of the rotation locus of the light emitting diode 24 is obtained from the three or more positions on the rotation locus of the measured light emitting diode 24, and the virtual hand position for offset calculation is obtained as camera coordinates. The coordinates are converted from Rc to reference coordinates Rb. The Xb and Yb coordinate values of the virtual hand position for offset calculation are the same as the Xb and Yb coordinate values of the hand because the wrist arm 11 is vertically downward.

  After the hand is moved to a plurality of movement target positions on the straight lines A1 and A2 in this way to obtain the offset calculation virtual hand position, a plurality of offset calculation virtual hand positions are obtained as in the first embodiment. If the length of the perpendicular line drawn from the origin Ob to the extended line of the connecting line is obtained as the amount of deviation, this amount of deviation becomes the inter-axis offset.

  If the wrist arm 11 is vertically downward, the virtual hand position for offset calculation is the same as the Xb and Yb coordinate value hand of the hand, but the fifth axis Lc-5 is the second, third axis Lc-2, Lc. If it is parallel to −3, the posture of the wrist arm 11 does not have to be vertically downward. That is, since the movement to the movement target position is performed while keeping the fifth axis Lc-5 that is the rotation center line of the wrist arm 11 horizontal, the wrist arm 11 moves to the fifth axis Lc-5 at each movement target position. The virtual hand position for offset calculation is located on a line parallel to the X0 axis (a straight line Bb parallel to the X0 axis in FIG. 16) no matter how it rotates around the axis. This is because there is no change in the amount of offset.

(Fourth embodiment)
In the fourth embodiment, as in the third embodiment, the support base 26 to which the light emitting diodes 24 are attached is attached to the distal end surface of the flange 12 at an arbitrary position away from the center (hand) P. is there. The reference coordinate Rb is obtained in the same manner as in the third embodiment. The difference from the third embodiment is in how to obtain the offset between axes.

  In the present embodiment, the inter-axis offset is obtained by the same method as in the second embodiment. That is, a plurality of arbitrary movement target positions (positions on the robot coordinate R0) are selected on the plus side (the right side of the Yb axis in FIG. 17) and the minus side (the left side of the Yb axis in FIG. 17) of the Xb coordinate value. In addition, for a plurality of selected movement target positions, the movement position error of the hand due to each error other than the offset between axes (deflection of the rotation drive system, origin position error of the servo motor 15, torsion angle error, link length error) is eliminated. Process.

  Thereafter, the hand is moved to a plurality of selected movement target positions. At this time, the fifth axis Lc-5 is parallel to the second and third axes Lc-2 and Lc-3, the wrist arm 11 is vertically downward, that is, the Z6 axis of the flange coordinate R6 is vertically downward (the sixth axis Lc-6 At least two of the first rotary joint J1 and the second, third, and fifth rotary joints J2, J3, and J5 so that the position of the rotary joint J1 and the second rotary joint J2, J3, and J5 is maintained. In this embodiment, the rotation shafts 14 of the second, third, and fifth rotary joints J2, J3, and J5 are rotated.

  Then, at each movement target position, the flange 11 is rotated, and any three or more different positions on the rotation locus of the light emitting diode 24 are measured by the three-dimensional measuring instrument 23. The center position (offset calculation virtual hand position) of the rotation locus of the light emitting diode 24 is obtained from three or more positions on the rotation locus of the light emitting diode 24, and the offset calculation virtual hand position is determined from the camera coordinates Rc. Coordinates are converted to coordinates Rb.

  Thereafter, the movement target position and the offset calculation virtual hand position (corresponding to the measurement position of the light emitting diode 24 in FIG. 17) are plotted on the XbYb coordinate plane of the reference coordinate Rb, and the line segment from the origin Ob to the movement target position is plotted. A length similar to that of FIG. 18 is created by setting the length as the target position radius D0 and the length of the perpendicular line drawn from the virtual hand position for offset calculation passing through the origin Ob and the movement target position as the offset error component M0. In this graph, the relationship between the target position radius D0 and the offset error component M0 is plotted for each moving target position, and a straight line passing through these plotted points is defined as an error straight line G. A perpendicular is drawn from the origin of the graph to this error line G, and the length of this perpendicular is obtained as the total inter-axis offset amount F of the second, third, and fifth rotary joints.

  In the present embodiment, if the sixth axis Lc-6, which is the rotation center line of the sixth rotation joint J6, is not parallel to the first axis Lc-1, that is, not vertical, the Xb, Yb coordinates of the virtual hand position for offset calculation Since the value changes depending on the inclination angle of the rotation center Lc-6, and the offset error component M0 also changes accordingly, the sixth axis Lc-6, which is the rotation center of the sixth rotation joint J6, is vertical (Lc-6 is Lc−). (Parallel to 1) is a matter necessary to make the Xb and Yb coordinate values of the virtual hand position for offset calculation the same as the Xb and Yb coordinate values of the hand.

(Other embodiments)
The present invention is not limited to the embodiments described above and shown in the drawings, and the following modifications or expansions are possible.
The Xb axis of the reference coordinate Rb is not necessarily parallel to the X0 axis. What is necessary is just to set to the arbitrary straight lines which pass through the origin Ob. In this case, the reference is obtained by obtaining the relationship between the reference coordinate Rb and the robot coordinate R0 based on the angle between the arbitrary straight line (Xb axis) and the X0 axis (rotation angle from the origin position of the shoulder 7) and performing coordinate conversion. The position on the coordinate Rb and the position on the robot coordinate R0 may be converted to each other.

  In the first embodiment, an arbitrary extension line A1 extending from the Zb axis is set on the XbYb plane of the reference coordinate Rb, and an extension line A2 extending from the Zb axis in the direction opposite to the arbitrary extension line A1 is set. In addition, any plurality of positions on each of the extension lines A1 and A2 is set as the movement target position. This is because any plurality of positions in one plane (vertical plane) including the Zb axis is selected as the movement target position. Also good. The reason is that when the hand is moved to the movement target position, the difference between the movement target position and the actual movement position of the hand in the Xb axis direction and the Yb axis direction is the Zb coordinate value if the XbYb coordinate value is the same. This is because even if they are different, the same value is shown. In this case, when moving the hand to a plurality of movement target positions, depending on the selection of the movement target position, the rotation shaft 14 of one rotation joint among the second, third, and fifth rotation joints J2, J3, and J5 is rotated. Then, the hand can be moved to the movement target position.

  In the first embodiment, when moving the hand from the straight line A1 (plane extending in one direction from the Zb axis) to the movement target position of the straight line A2 (plane extending in the opposite direction from the Zb axis), the selected position of the movement target position is used. If the rotary shaft 14 of one of the second, third, and fifth rotary joints J2, J3, and J5 is rotated, the robot arm 6 can be reversed to move the hand to the movement target position. it can.

  In the second embodiment, when the hand is moved to a plurality of arbitrarily selected movement target positions, all of the second, third and fifth rotary joints J2, J3 and J5, or the rotation axes of any two rotary joints 14 may be rotated, but depending on the selection position of the movement target position, in addition to the first rotary joint J1, the rotation axis of one of the second, third, and fifth rotary joints J2, J3, and J5 If the hand 14 is rotated, the hand can be moved to the movement target position. That is, the rotation shaft of at least one rotary joint may be rotated.

  In the third embodiment, when the hand center is moved to the movement target position while maintaining the posture in which the rotation center line Lc-6 of the sixth rotation joint J6 is parallel to the rotation center line Lc-1 of the first rotation joint J1, Depending on the selected movement target position, the hand can be moved to the movement target position by moving any two of the second, third, and fifth rotation joints J2, J3, and J5.

  In the fourth embodiment, the sixth axis Lc-6 that is the rotation center line of the sixth rotation joint J6 is parallel to the first axis Lc-1 that is the rotation center line of the first rotation joint J1. Can be moved to the movement target position depending on the movement target position by rotating the rotation shafts 14 of at least two of the second, third, and fifth rotation joints J2, J3, and J5.

  In the drawings, 3 is a control device, 5 is a base (base link), 6 is a robot arm, 7 is a shoulder (first link), 8 is a lower arm (second link), and 9 is a first upper arm (third). Link), 10 is a second upper arm (fourth link), 11 is a wrist arm (fifth link), 12 is a flange (sixth link), 23 is a three-dimensional measuring instrument (three-dimensional measuring means), and 24 is A light emitting diode (measurement point) is shown.

Claims (8)

A 6-axis robot in which first to sixth links constituting a robot arm are sequentially connected to a base link fixed to a mounting surface by first to sixth rotary joints, The rotation center line of the rotation axis of the second rotation joint connecting the second link to one link is orthogonal to the rotation center line of the rotation axis of the first rotation joint connecting the first link to the base link. The rotation center line of the rotation axis of the third rotation joint connecting the third link to the second link is parallel to the rotation center line of the rotation axis of the second rotation joint, The rotation center line of the rotation axis of the fourth rotation joint connecting the fourth link to the link is parallel to the direction perpendicular to the rotation center line of the rotation axis of the third rotation joint, and the fourth link The fifth rotary joint connecting the fifth link The rotation center of the rotation shaft of the sixth rotation joint that connects the sixth link to the fifth link so that the rotation center line of the rotation shaft is parallel to the direction orthogonal to the rotation center line of the rotation shaft of the fourth rotation joint. A line is set in parallel to a direction perpendicular to the rotation center line of the rotation axis of the fifth rotation joint, and
The coordinates of the first to sixth links are set on the rotation center lines of the rotation axes of the first to sixth rotary joints, respectively, and the tip of the sixth link is the forefront of the robot arm. In a 6-axis robot in which the center of rotation of the surface is the hand and the coordinates of the hand are set at the same position,
A measuring point is provided on the hand, and a three-dimensional measuring means capable of measuring a three-dimensional position of the measuring point is provided,
The robot arm is held in an arbitrary posture in which the rotation center line of the rotation axis of the fifth rotation joint is kept parallel to the rotation center lines of the rotation axes of the second rotation joint and the third rotation joint. The arm is rotated around the rotation axis of the first rotary joint, and three or more different positions of the measurement points that move on the circular rotation locus by this rotation are measured by a three-dimensional measuring means,
From the measured three or more positions on the rotation locus of the measurement point, the center position of the rotation locus of the measurement point and the normal of the plane including the three or more positions on the rotation locus of the measurement point are obtained. The center of the rotation locus of the measurement point is the origin, the straight line passing through the origin and parallel to the normal is the Z axis, the arbitrary straight line passing through the origin and perpendicular to the Z axis is the X axis, and the origin is Through which a reference coordinate having a Y axis as a straight line perpendicular to both the Z and X axes is defined;
Determining any plurality of positions on any one plane including the Z axis extending from the Z axis of the reference coordinates as movement target positions, and moving the hand to each of the movement target positions on the one plane; When
Origin position errors of the motors driving the first to sixth links via the first to sixth rotary drive systems including the rotation axes of the first to sixth rotary joints; The position error of the hand does not occur due to the deflection of each sixth rotational drive system, the length error of each of the first to sixth links, and the angle error between the rotation joint and the rotation axis of the next rotation joint. After performing correction processing on
Of the second, third, and fifth rotary joints, the rotation center line of the rotation shaft of the fifth rotation joint is maintained parallel to the rotation center line of the rotation shaft of each of the second and third rotation joints. After rotating the rotation shaft of the first rotation joint to a position where the hand can be moved to the movement target position by rotating the rotation shaft of at least one rotation joint, the rotation shaft of the first rotation joint By rotating the rotation axis of the at least one rotary joint among the second, third, and fifth rotary joints in a fixed state, the hand is moved to each of the plurality of movement target positions to move each of the plurality of movement target positions. Measure the position of the measurement point at the target position by the three-dimensional measuring means,
The XY coordinate value on the reference coordinate is obtained by converting the position of the measurement point measured at each moving target position to the position on the reference coordinate, and the obtained XY coordinate value is placed on the XY coordinate plane of the reference coordinate. The line segment connecting the plotted points is plotted as a measurement dependent line segment, and the length of the perpendicular line drawn from the origin of the reference coordinates is obtained as a deviation amount on a straight line obtained by extending this measurement dependent line segment,
A method for detecting an inter-axis offset of a robot, wherein the obtained deviation amount is set as a total inter-axis offset amount of the second, third, and fifth rotary joints. The method for detecting an offset between axes of a robot according to claim 1,
The operation of determining any plurality of positions on any one plane including the Z axis extending from the Z axis of the reference coordinates as the movement target positions and moving the hand to each of the movement target positions on the one plane is The movement of the hand from two planes extending in opposite directions from the Z-axis of the reference coordinates to the plane extending in the opposite direction from the plane extending in one direction from the Z-axis, The robot arm is reversed by rotating the rotation axis of at least one of the second, third, and fifth rotation joints in a state where the rotation axis of the first rotation joint is fixed. A method for detecting an offset between axes of a robot. In the method for detecting the offset between axes of the robot according to claim 1, instead of the operation until determining the offset between axes after determining the reference coordinates,
When the hand is moved to any of a plurality of movement target positions on the reference coordinates,
Origin position errors of the motors driving the first to sixth links via the first to sixth rotary drive systems including the rotation axes of the first to sixth rotary joints; The position error of the hand does not occur due to the deflection of each sixth rotational drive system, the length error of each of the first to sixth links, and the angle error between the rotation joint and the rotation axis of the next rotation joint. After performing correction processing on
The first rotation joint and the second, third, and third rotation joints are maintained in a state in which the rotation center line of the rotation shaft of the fifth rotation joint is parallel to the rotation center lines of the rotation axes of the second and third rotation joints. The hand is moved to each of the plurality of movement target positions by rotating the rotation axis of at least one of the five rotation joints, and the position of the measurement point is determined by the three-dimensional measurement means at each movement target position. Measure and
Obtaining a coordinate value on the reference coordinate by converting the position of the measurement point measured at each movement target position to a position on the reference coordinate;
For each movement target position, the XY coordinate value of the movement target position and the XY coordinate value of the measurement point are plotted on the XY plane of the reference coordinates, and the movement target on the XY plane from the origin of the reference coordinates. The length of the line segment to the position is set as the target position radius, and the length of the perpendicular line drawn from the measurement point on the XY plane to the straight line passing through the origin of the reference coordinates and the movement target position is used as an offset error component. ,
For each moving target position, the relationship between the target position radius and the offset error component is plotted in a graph in which the target position radius is taken on one of two orthogonal axes and the offset error component is taken on the other axis. Then, when a straight line passing through these plotted points is taken as an error straight line, the length of the perpendicular drawn from the origin of the graph to the error straight line is obtained as a deviation amount,
A method for detecting an inter-axis offset of a robot, wherein the obtained deviation amount is set as a total inter-axis offset amount of the second, third, and fifth rotary joints. The method for detecting an offset between axes of a robot according to claim 3,
The operation of moving the hand to any of a plurality of movement target positions of the reference coordinates,
By rotating the rotation axes of at least the second and third rotary joints in the second, third, and fifth rotary joints in one direction and the other direction with the rotary axis of the first rotary joint fixed. A method for detecting an offset between axes of a robot, wherein the robot arm is operated in both a forward bending posture in which the robot arm is tilted to one side from the first link and a backward bending posture in which the robot arm is tilted to the other side. A 6-axis robot in which first to sixth links constituting a robot arm are sequentially connected to a base link fixed to a mounting surface by first to sixth rotary joints, The rotation center line of the rotation axis of the second rotation joint connecting the second link to one link is orthogonal to the rotation center line of the rotation axis of the first rotation joint connecting the first link to the base link. The rotation center line of the rotation axis of the third rotation joint connecting the third link to the second link is parallel to the rotation center line of the rotation axis of the second rotation joint, The rotation center line of the rotation axis of the fourth rotation joint connecting the fourth link to the link is parallel to the direction perpendicular to the rotation center line of the rotation axis of the third rotation joint, and the fourth link The fifth rotary joint connecting the fifth link The rotation center of the rotation shaft of the sixth rotation joint that connects the sixth link to the fifth link so that the rotation center line of the rotation shaft is parallel to the direction orthogonal to the rotation center line of the rotation shaft of the fourth rotation joint. A line is set in parallel to a direction perpendicular to the rotation center line of the rotation axis of the fifth rotation joint, and
The coordinates of the first to sixth links are set on the rotation center line of the rotation axis of each of the first to sixth rotation joints, and the rotation axis of the sixth rotation joint of the sixth links. In a 6-axis robot in which the coordinates of the hand are set at the same position with the predetermined position existing on the rotation center line as the hand,
A measurement point that operates integrally with the sixth link is provided at a position away from the rotation center axis of the sixth link, and a three-dimensional measurement means that can measure the three-dimensional position of the measurement point is provided,
The first link is maintained while maintaining the robot arm in an arbitrary posture in which the rotation center line of the rotation axis of the fifth rotation joint is parallel to the rotation center lines of the rotation axes of the second and third rotation joints. Are rotated to three or more arbitrary angular positions different from each other, and the sixth link is rotated at each angular position to rotate integrally with the sixth link. Is measured by a three-dimensional measuring means,
The position of the rotation center of the measurement point at each angular position is obtained from a plurality of three or more positions on the rotation locus of the measurement point by the rotation of the sixth link measured at each angular position of the first link. The position of the rotation center of the measurement point is set as a reference coordinate setting virtual hand position, and the center position of a circle passing through these reference coordinate setting virtual hand positions from the obtained three or more reference coordinate setting virtual hand positions, and three or more The normal of the plane including the reference coordinate setting virtual hand position is obtained, the center of the obtained circle is the origin, the straight line parallel to the normal passing through the origin is the Z axis, and the Z passing through the origin is the Z An arbitrary straight line orthogonal to the axis is defined as the X axis, and a reference coordinate is defined with the straight line passing through the origin and orthogonal to both the Z and X axes as the Y axis.
When a plurality of arbitrary positions on an arbitrary plane extending from the Z axis of the reference coordinates are set as movement target positions, and the hand is moved to each of the movement target positions on the one plane,
Origin position errors of the motors driving the first to sixth links via the first to sixth rotary drive systems including the rotation axes of the first to sixth rotary joints; The position error of the hand does not occur due to the deflection of each sixth rotational drive system, the length error of each of the first to sixth links, and the angle error between the rotation joint and the rotation axis of the next rotation joint. After performing correction processing on
Of the second, third, and fifth rotary joints, the rotation center line of the rotation axis of the fifth rotation joint is maintained parallel to the rotation center lines of the rotation axes of the second rotation joint and the third rotation joint. After rotating the rotation shaft of the first rotation joint to a position where the hand can be moved to the movement target position by rotating the rotation shaft of at least one rotation joint, the rotation shaft of the first rotation joint By rotating the rotation shaft of the at least one rotary joint among the second, third, and fifth rotary joints in a fixed state, and moving the hand to each of the plurality of movement target positions; and Rotating the sixth link at each movement target position and measuring three or more different positions on the rotation trajectory of the measurement point rotated by the rotation of the sixth link by a three-dimensional measuring means,
The rotation center position of the measurement point is obtained from a plurality of three or more positions on the rotation locus of the measurement point measured at each movement target position, and this is used as the virtual hand position for offset calculation. Coordinate conversion to a position on the reference coordinates, to obtain XY coordinate values on the reference coordinates of a plurality of offset calculation virtual hand positions,
The XY coordinate value of the calculated virtual hand position for offset calculation is plotted on the XY plane of the reference coordinate, and a line segment connecting these plotted points is defined as a measurement dependent line segment. Obtain the length of the perpendicular drawn from the origin of the reference coordinates as a deviation amount,
A method for detecting an inter-axis offset of a robot, wherein the obtained deviation amount is set as a total inter-axis offset amount of the second, third, and fifth rotary joints. The method for detecting an offset between axes of a robot according to claim 5,
The operation of determining any plurality of positions on any one plane developed from the Z-axis of the reference coordinates as movement target positions and moving the hand to each of the movement target positions on the one plane is The two planes extending in the opposite directions from the Z axis are performed, and the transition from one plane to the other plane is performed while the rotation axis of the first rotary joint is fixed. A method for detecting an offset between axes of a robot, wherein the robot arm is reversed by rotating a rotation axis of at least one of the three or five rotation joints. Instead of the operation until the inter-axis offset amount is obtained after determining the reference coordinates in claim 5,
When the hand is moved to an arbitrary plurality of movement target positions of the reference coordinates,
Origin position errors of the motors driving the first to sixth links via the first to sixth rotary drive systems including the rotation axes of the first to sixth rotary joints; The position error of the hand due to the deflection of each sixth rotational drive system, the length error of each of the first to sixth links, and the angle error between the rotation joint and the rotation axis of the next rotation joint does not occur. After performing the correction process,
The first rotation joint and the second and third rotation joint lines are maintained in a state in which the rotation center line of the rotation shaft of the fifth rotation joint is parallel to the rotation center line of the rotation shaft of each of the second and third rotation joints. By rotating the rotation shafts of at least two of the five rotation joints, the rotation center line of the rotation shaft of the sixth rotation joint is rotated around the rotation center line of the rotation shaft of the first rotation joint. Rotation trajectory of the measurement point that moves in parallel with the plurality of movement target positions and rotates the sixth link at each movement target position to rotate integrally with the sixth link Measure three or more different positions on the top with a three-dimensional measuring means,
The rotation center position of the measurement point is obtained from a plurality of positions on the rotation locus of the measurement point measured at each movement target position, and this is used as the virtual hand position for offset calculation, and the offset calculation at each obtained movement target position is performed. A coordinate conversion of the virtual hand position to the position on the reference coordinate to obtain an XY coordinate value on the reference coordinate of a plurality of virtual hand positions for offset calculation;
For each movement target position, the XY coordinate value of the movement target position and the XY coordinate value of the virtual hand position for offset calculation are plotted on the XY plane of the reference coordinate, and the origin of the reference coordinate is plotted on the XY plane. The length of the line segment to the movement target position is set as a target position radius, and the offset calculation virtual hand position on the XY plane passes through the origin of the reference coordinates and the movement target position on the XY plane. The length of the perpendicular line drawn as a straight line is used as the offset error component,
For each moving target position, the relationship between the target position radius and the offset error component is a graph in which the moving target position radius is taken on one of the two orthogonal axes and the offset error component is taken on the other axis. When the straight line connecting the plotted points is plotted as the error line, the length of the perpendicular line drawn from the origin of the graph to the error line is obtained as the deviation amount,
A method for detecting an inter-axis offset of a robot, wherein the obtained deviation amount is set as a total inter-axis offset amount of the second, third, and fifth rotary joints. The method for detecting an offset between axes of a robot according to claim 7,
The operation of moving the hand to any of a plurality of movement target positions of the reference coordinates,
By rotating the rotation axes of at least the second and third rotary joints in the second, third, and fifth rotary joints in one direction and the other direction with the rotary axis of the first rotary joint fixed. A method for detecting an offset between axes of a robot, wherein the robot arm is operated in both a forward bending posture in which the robot arm is tilted to one side from the first link and a backward bending posture in which the robot arm is tilted to the other side.

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