JP5667437B2 - Robot external axis measurement method, robot teaching data creation method, and robot controller - Google Patents

Description

  The present invention relates to a method for measuring an external axis of a robot that measures the relative position and orientation of a rotary axis or a linear axis of a positioner that grips a work on which the robot works, and teaching data generation of a robot that cooperates with the positioner The present invention relates to a method and a controller of a robot.

  Conventionally, an articulated robot is caused to perform operations such as welding and painting on a work gripped by a positioner. The positioner is a device that rotates or translates the workpiece. By cooperating with such a positioner, the robot can perform work on various parts of the workpiece from various directions.

  By the way, in order for the robot to perform the work with high accuracy on the workpiece gripped by the positioner, it is necessary to accurately measure the relative position and orientation of the rotation axis of the positioner or the linear movement axis with respect to the robot. For example, Patent Document 1 discloses a method of measuring a relative position and orientation with respect to a robot with respect to a rotation axis and a linear movement axis of a positioner. The rotation axis and linear motion axis of the positioner are called “robot external axes”.

  For example, in a positioner having a rotating shaft disclosed in Patent Document 1, in order to obtain a relative position and orientation of the rotating shaft of the positioner with respect to the robot, a predetermined position (by rotating around the rotating shaft as a center) is obtained. Measurement points are defined in the positioner section).

  In Patent Document 1, the position and orientation of the rotation shaft of the positioner is measured each time a measurement point is displaced a plurality of times by rotating a rotation angle by a predetermined angle around the rotation shaft and the measurement point is rotated by a predetermined angle. The tip point (end effector center point) of the measurement tool attached to the tip of the robot is manually aligned with the measurement point. The position (coordinates) of the measurement point is calculated based on the position (coordinates) of the tip point that is aligned with the measurement point. Then, the relative position and orientation of the rotation axis of the positioner with respect to the robot is calculated based on the calculated positions of the measurement points. This method is premised on that the robot (robot controller) has a function of calculating the position of the tip point of the measurement tool based on the posture (joint angle of each joint) at that time.

JP-A-8-129408

  However, based on the relative position and orientation of the rotation axis of the positioner with respect to the robot calculated by the method described in Patent Document 1, if the robot performs a work on the work gripped by the positioner, the work cannot be performed with high accuracy. There is. This is because the “error” of the robot is not fully considered.

  For example, in order to position the tip of the measurement tool at a certain target point, a posture control value (joint angle of each joint) that realizes the posture in which the tip of the measurement tool is placed at the target point is calculated by a computer or the like When the posture of the robot is controlled based on the calculated posture control value (when so-called off-line teaching is executed), the tip point of the measurement tool is positioned at a position shifted from the target point. That is, a positioning error. This positioning error is because the posture control value is not calculated considering all causes that affect the position of the tip point, such as the twist of the shaft of the motor driving the joint, the deflection of the link, the detection error of the encoder, etc. Arise.

  Further, for example, when the operator manually operates the teaching pendant to measure the position (coordinate value) of a certain target point, the tip point of the measuring tool is manually aligned with the target point. The position (coordinate value) of the tip point of the tool calculated by is deviated from the actual position of the target point. That is, a position measurement error. This position measurement error can be used to calculate the position of the tip of the measurement tool, which can affect the position of the tip such as torsion of the shaft of the motor that drives the joint, link deflection, and encoder detection error. This occurs because the calculation is based on the joint angle of each joint without considering the cause.

  However, it is virtually impossible to consider any cause that affects the position of the tip of the measuring tool.

  Therefore, when the relative position and orientation of the rotation axis of the positioner or the linear motion axis with respect to the robot is measured by the robot, and the robot performs the work with high accuracy on the workpiece gripped by the positioner based on the measurement result, It is necessary to fully consider both positioning errors and position measurement errors.

  Therefore, the present invention measures the relative position and orientation of the positioner relative to the rotation axis or linear movement axis of the robot by the robot, and the robot executes the work on the workpiece gripped by the positioner based on the measurement result. Therefore, it is an object of the present invention to realize highly accurate work on a workpiece by a robot by sufficiently considering both a positioning error and a position measurement error of the robot.

In order to solve the above-mentioned problem, according to the first aspect of the present invention,
A method for measuring an external axis of a robot that measures a relative position and orientation of a rotation axis or a linear movement axis of a positioner that grips a workpiece to be operated by the robot, which is an external axis of the robot,
The posture of the robot when the reference point of the robot is manually aligned with the measurement point defined at a predetermined position with respect to the rotation axis or the linear motion axis of the positioner, and the state where the reference point is aligned with the measurement point. Change to the measurement posture while maintaining,
As the measurement posture of the robot ,
(1) At each joint, a difference value between a joint value at the work posture when performing a work on a work gripped by the positioner and a joint value at the measurement posture;
(2) Based on predefined weight values for each joint,
Determine a posture with a high degree of similarity to the working posture ,
Calculate the position of the measurement point of the positioner by calculating the position of the reference point in the robot in the measurement posture state,
A method for measuring an external axis of a robot is provided that calculates the position and orientation of a rotation axis or a linear movement axis of the positioner based on the calculated position of the measurement point of the positioner .

According to a second aspect of the invention,
For each of the multiple measurement postures of the robot that can align the reference point with the measurement point,
(1) For each joint, a first value is calculated as a difference value between the joint value at the work posture and the joint value at the measurement posture;
(2) For each joint, calculate the second value by multiplying the square value of the first value by the weight value,
(3) The second value of each joint is summed to calculate the third value,
The measuring method of the external axis of the robot according to the first aspect, wherein the measuring posture having the minimum third value is determined.

According to a third aspect of the invention,
The method for measuring an external axis of a robot according to the first or second aspect is provided in which the weight value is set to a larger value for a joint that greatly displaces the reference point of the robot when the joint value changes. The

According to a fourth aspect of the invention,
A robot teaching data creation method for creating teaching data of an articulated robot that performs work on a workpiece held by a positioner that rotates or translates the workpiece with respect to a rotation axis or a linear motion axis. ,
The positioner grips the positioner using the relative position and orientation of the rotation axis of the positioner or the linear motion axis calculated by the external axis measurement method of the robot according to any one of the first to third aspects. There is provided a robot teaching data creation method for creating teaching data for performing work on a workpiece.

According to a fifth aspect of the present invention,
A controller for an articulated robot that performs work on the workpiece held by a positioner that rotates or translates the workpiece with respect to a rotation axis or a linear movement axis,
Work posture data acquisition means for acquiring work posture data corresponding to the work posture of the robot when performing work on the workpiece;
Robot operation means for aligning the reference point of the robot with a measurement point defined at a predetermined position with respect to the rotation axis or linear motion axis of the positioner by the operation of the operator;
Measurement posture determination means for calculating the measurement posture of the robot in a state where the reference point is aligned with the measurement point based on the work posture data acquired by the work posture data acquisition means;
Measuring point position calculating means for calculating the position of the measurement point of the positioner in the state of the measuring attitude calculated by the measuring attitude determining means;
Measurement posture determination means, as the measurement posture,
(1) For each joint, a difference value between the joint value of the work posture data and the joint value at the measurement posture;
(2) Based on predefined weight values for each joint,
A robot controller is provided that determines a posture with a high degree of similarity to the working posture.

  According to the present invention, the measurement posture of the robot when measuring the relative position and posture of the positioner relative to the rotation axis or linear movement axis is the work posture when the work is performed on the workpiece held by the positioner. Therefore, the position measurement error and positioning error of the robot can be sufficiently offset. As a result, the robot can execute the work with high accuracy on the work gripped by the positioner.

The figure which shows schematically the robot equipment which concerns on embodiment of this invention Diagram for explaining the relationship between posture and position measurement error Diagram for explaining the relationship between position measurement error and positioning error The figure which shows the structure of the controller of the robot which concerns on embodiment of this invention. The figure which shows the flow which calculates the position of the measurement point of the positioner

  First, in order to better understand the present invention, the concept of the position / orientation measuring method of the positioner according to the present invention will be described.

  FIG. 1 schematically shows a robot facility according to an embodiment of the present invention. FIG. 1 shows how the position and orientation of the rotation axis (rotation center line) Ar of the positioner 12 is measured by the robot 10.

  A robot 10 shown in FIG. 1 is an articulated robot having joints 10a to 10f. By attaching a working tool such as a spray gun or a welding torch to a flange 10g at the tip, a painting work, a welding work, etc. The above operation is performed on the workpiece W. Here, the measurement tool 14 is attached to the flange 10g. The joints 10a, 10d, and 10f are torsional joints, and the joints 10b, 10c, and 10e are bending joints.

  The posture of the robot 10 is also controlled by the controller 16. Specifically, the controller 16 controls the posture of the robot 10 by controlling a motor (not shown) that drives the joints 10a to 10f of the robot 10 (adjusts the joint angle).

  The controller 16 also has a function of calculating the position of the tip point Pt of the measuring tool 14, specifically, for example, the coordinates of the tip point Pt in the base coordinate system ΣB defined in advance in the base B of the robot 10, for example. Yes. In this specification, “position” and “posture” refer to the position and posture in the base coordinate system ΣB.

  Based on the posture of the robot 10, that is, based on the joint angles (bending angle and torsion angle) of each of the joints 10a to 10f, the controller 16 serves as a tip point of the measuring tool 14 as an end effector center point (claims). The position of Pt is calculated. For this purpose, an encoder (not shown) for detecting the joint angle is provided in each of the joints 10a to 10f. Further, in the storage device (not shown) of the controller 16, the link length of each of the links 10h to 10m, the distance from the tip point Pt of the measurement tool 14 to the flange 10g, etc. necessary for calculation of the position of the tip point Pt, etc. Data is stored.

  The positioner 12 has a work table 18 that rotates about a rotation axis Ar. A work W to be worked by the robot 10 is fixed to the work table 18 via a jig (not shown). Here, a marker 20 for measuring the position and orientation of the rotation axis Ar of the positioner 12 (relative position and orientation with respect to the robot 10) is attached. The distance from the measurement point Pm at the tip of the marker 20 to the rotation axis Ar is known and stored in the storage device of the controller 16 of the robot 10.

  The measurement point Pm is not limited to being defined at a predetermined position with respect to the rotation axis Ar via the marker 20. For example, it may be defined directly on the work table 18 that rotates about the rotation axis Ar.

  The position and orientation of the rotation axis Ar of the positioner 12 is measured by the operator manually operating the robot 10 via a teaching pendant (not shown), and the tip point Pt of the measurement tool 14 is set to the measurement point Pm of the marker 20. This is done by aligning. By calculating the position of the tip point Pt that is aligned with the measurement point Pm, the position of the measurement point Pm can be calculated. Then, the position and orientation of the rotation axis Ar can be calculated based on the calculated position of the measurement point Pm.

  Specifically, by rotating the work table 18 around the rotation axis Ar, the work table 18 takes a plurality of different postures, and the measurement points Pm of the marker 20 are measured for each different posture of the work table 18. The tip point Pt of the tool 14 is aligned. Then, the position of the measurement point Pm is calculated for each different posture of the work table 18. Since the distances from the calculated positions of the different measurement points Pm to the rotation axis Ar are the same, the position and orientation of the rotation axis Ar can be calculated geometrically. By calculating the position and orientation of the rotation axis Ar of the positioner 12 with respect to the robot 10, the robot 10 can perform work on the workpiece W whose posture is changed by the positioner 12.

  Based on the above, the features of the present invention will now be described.

  As described above, in order to measure the relative position and orientation of the rotation axis Ar of the positioner 12 with respect to the robot 10, it is necessary to calculate the position of the tip point Pt of the measurement tool 14. However, the position of the tip point Pt of the measurement tool 14 calculated by the controller 16 is different from the actual position of the tip point Pt.

  This is because, for example, all causes that affect the position of the tip point Pt, such as twisting of the rotating shaft of the motor that drives the joint, deflection of the link, ambient temperature, detection error of the encoder, etc. are fully considered. This is because the position of the tip point Pt cannot be calculated. Therefore, the relative position and orientation of the rotation axis Ar with respect to the robot 10 calculated by the method based on the position of the tip point Pt described above is different from the actual position and orientation, that is, includes a position measurement error.

  Therefore, the relative position and orientation of the rotation axis Ar of the positioner 12 with respect to the robot 10 is measured by the robot 10, and the robot 10 performs the work with high accuracy on the workpiece W gripped by the positioner 12 based on the measurement result. In this case, it is necessary to sufficiently consider the position measurement error of the robot 10.

In the present invention, in consideration of the position measurement error of the robot 10, the posture at the time of measurement of the robot 10 (hereinafter referred to as “measurement posture”) is clearly defined. The reason is when measuring the relative position and orientation relative to the robot 10 of the rotary shaft Ar of Pojishi ® Na 12 using robot 10, since position measurement error by the measurement posture of the robot 10 is different.

  For example, as shown in FIG. 2 schematically representing the robot equipment of FIG. 1, if the measurement posture is different, the controller 16 of the robot 10 calculates the position and posture of the rotation axis Ar of the positioner 12 with different position measurement errors. .

  FIG. 2A shows a state where the measurement tool 14 is oriented in the vertical direction (Z-axis negative direction) (a state where the tip portion extends from the joint 10e in the vertical direction) and the tip point Pt is the measurement point Pm of the marker 20. The measurement posture to be aligned is shown. On the other hand, FIG. 2B shows a state in which the tip Pt is the measurement point Pm in a state where the measurement tool 14 is oriented in the horizontal direction (X-axis positive direction) (a state where the portion extending from the joint 10e extends in the horizontal direction). The measurement posture to be aligned is shown. In the drawing, the solid line indicates the actual robot 10 and the positioner 12. On the other hand, the two-point difference line indicates the robot 10 and the positioner 12 in calculation.

  In the measurement posture shown in FIG. 2A, the rotation axis (calculation rotation axis) Arc1 of the positioner 12 calculated by the controller 16 is a direction (X axis) from the actual rotation axis Ar to the base B side of the robot 10. It shifts in the negative direction.

  The reason will be described. When the operator manually operates the robot 10 via the teaching pendant to align the tip point Pt of the measurement tool 14 with the measurement point Pm of the marker 20, as indicated by a two-dot chain line. The position of the measurement point (calculation measurement point) Pmc1 calculated by the controller 16 tends to deviate from the actual measurement point Pm toward the base B side of the robot 10. As a result, the rotation axis Arc1 calculated based on the position of the shifted measurement point Pmc1 shifts from the actual rotation axis Ar in the direction toward the base B of the robot 10. That is, a position measurement error in the direction from the actual rotation axis Ar to the base B side of the robot 10 occurs.

  In contrast, in the measurement posture shown in FIG. 2B, the rotation axis (calculation rotation axis) Arc2 of the positioner 12 calculated by the controller 16 is the base B side of the robot 10 from the actual rotation axis Ar. The direction is shifted to the opposite direction (X-axis positive direction).

  The reason will be explained. When the operator operates the robot 10 via the teaching pendant to align the tip point Pt of the measurement tool 14 with the measurement point Pm of the marker 20, as indicated by a two-dot chain line, The position of the measurement point (calculation measurement point) Pmc2 calculated by the controller 16 tends to deviate from the actual position of the measurement point Pm in a direction opposite to the direction on the base B side of the robot 10. As a result, the rotation axis Arc2 calculated based on the position of the shifted measurement point Pmc2 deviates from the actual rotation axis Ar in a direction opposite to the direction on the base B side of the robot 10. That is, a position measurement error in the direction opposite to the direction on the base B side of the robot 10 from the actual rotation axis Ar occurs.

  Thus, if the measurement postures are different, the controller 16 of the robot 10 calculates the position and posture of the rotation axis Ar of the positioner 12 with different position measurement errors.

  In consideration of the fact that the position measurement error is different when the measurement posture is different, in the present invention, the measurement posture is determined to be a posture similar to the work posture when working on the workpiece.

  FIG. 3A shows a rotation axis (calculation rotation axis) Arc1 of the positioner 12 measured by the robot 10 in the measurement posture shown in FIG. 2A (a state in which the portion extending from the joint 10e extends in the vertical direction). The state of the robot 10 that performs work on the workpiece W is shown based on FIG. On the other hand, FIG. 3B shows the rotation axis (calculated rotation axis) of the positioner 12 measured by the robot 10 in the measurement posture shown in FIG. 2B (the portion extending from the joint 10e extends in the horizontal direction). ) The state of the robot 10 that performs work on the workpiece W based on Arc2 is shown.

  The work posture of the robot 10 when performing work on the workpiece W is a posture similar to the measurement posture shown in FIG. 2A, that is, a posture in a state in which a portion extending from the joint 10e extends in the vertical direction.

  The work postures shown in FIGS. 3A and 3B are postures in which the tip point Pt ′ of the work tool is aligned with the work start point Pw of the work W. For example, when the work tool is a welding torch, the tip point Pt 'is the tip of the welding rod, and the work start point Pw is the welding start point. The position of the work start point Pw with respect to the rotation axis Ar is known and stored in the storage device of the controller 16.

  As shown in FIG. 3A, when the controller 16 controls the robot 10 to the working posture based on the calculated rotation axis Arc1, the work tool tip point Pt ′ is the work start point Pw of the work W. Is almost positioned. This is because the measurement posture and the working posture are postures in a state in which a portion extending from the joint 10e extends in the vertical direction as shown in FIGS. 2 (A) and 3 (A). .

  More specifically, as shown in FIG. 3A, the calculated rotation axis Arc1 is deviated from the actual rotation axis Ar in the direction toward the base B of the robot 10 (X-axis negative direction). When the controller 16 controls the robot 10 based on the calculated rotation axis Arc1, the tip point Pt 'is positioned at a position opposite to the base B side direction of the robot 10 from the calculated rotation axis Arc1. This is because, in the robot 10 whose posture is controlled by the controller 16, the motor shaft is twisted or the link is bent, and a positioning error occurs in which the tip point Pt ′ is shifted in the direction opposite to the direction of the base B side of the robot 10. It depends. As a result, the positioning error and the position measurement error with the opposite directions of the errors are almost offset, and the tip point Pt ′ of the work tool is almost at the work start point Pw of the work W as shown in FIG. Positioned.

  On the other hand, as shown in FIG. 3B, when the controller 16 controls the robot 10 to the working posture based on the calculated rotation axis Arc2, the tip point Pt ′ of the working tool is the workpiece W Is positioned at a position away from the work start point Pw. This is because, as shown in FIG. 2B and FIG. 3B, the measurement posture and the work posture are different and are not similar.

  More specifically, as shown in FIG. 3B, the calculated rotational axis Arc2 is shifted from the actual rotational axis Ar in a direction opposite to the direction on the base B side of the robot 10 (X-axis positive direction). Yes. When the controller 16 controls the robot 10 based on the calculated rotation axis Arc2, the tip point Pt 'is shifted from the calculated rotation axis Arc2 in a direction opposite to the direction on the base B side of the robot 10. This is because, in the robot 10 whose posture is controlled by the controller 16, the motor shaft is twisted or the link is bent, and a positioning error occurs in which the tip point Pt ′ is shifted in the direction opposite to the direction of the base B side of the robot 10. It depends. As a result, since the error directions are the same, the positioning error and the position measurement error are not canceled out, and the tip point Pt ′ of the work tool becomes the work start point of the work W as shown in FIG. Positioning is greatly deviated from Pw in the direction opposite to the direction on the base B side of the robot 10.

  In order to determine a measurement posture similar to the work posture, in the present invention, a degree of similarity (similarity) with respect to the work posture is calculated for each of a plurality of measurement postures, and a posture with a good calculated similarity is measured. And decide. The “plurality of measurement postures” will be described with reference to FIG. 1 as an example. A plurality of postures where the tip point Pt of the measurement tool 14 can be aligned with the measurement point Pm of the marker 20, that is, the measurement points Pm. An attitude that can measure the position.

Formula 1 is an equation for calculating the similarity D (J _i , J _s ) of the measurable posture J _{i with} respect to the work posture J _s (corresponding to “third value” in the claims). A smaller value of the similarity D (J _i , J _s ) means that the measurable posture J _i is similar to the work posture J _s , that is, suitable for the measurement posture.

In Equation 1, the parameter k indicates a joint number. k = 1 corresponds to joint 10a, k = 2 to joint 10b, k = 3 to joint 10c, k = 4 to joint 10d, k = 5 to joint 10e, and k = 6 to joint 10f Correspond. The parameter w _k is a weight value for the joint with the joint number k. The parameters q _{i, k} are the joint angles of the joint with the joint number k in the measurable posture J _i . The parameters q _{s and k} are the joint angles of the joint with the joint number k in the working posture J _s .

For example, the weight value w _k defined for each of the joints 10 a to 10 f is set to a smaller value as the joint is closer to the tip of the robot 10. Specifically, as the joint greatly displace the tip point Pt of the measurement tool 14 when the joint angle is changed, the weighting value w _k is set to a large value.

With such a weight value w _k , the measurable posture J _i having the minimum similarity D (J _i , J _s ) among the plurality of measurable postures J _i (that is, the measurable posture J _i determined as the measurement posture _). ) is a relatively large contributes joint displacement of the tip point Pt of the measurement tool 14 substantially coincides with the joint angle of the joint angle working posture J _s, relatively to the displacement of the tip point Pt of the measurement tool 14 small joint angle in contributing joint is the joint angle different from such orientation of the working posture J _s.

The reason for this will be described. Both the positioning error and the position measurement error are greatly influenced by the joint that greatly contributes to the position of the tip of the robot 10 in the direction and amount of the error. Therefore, if the joint angles of such joints differ greatly between the work posture and the measurement posture, the error direction and the amount of error differ greatly, and the positioning error and the position measurement error cannot be sufficiently offset. Therefore, the weight value w of the joint having a larger contribution to the displacement of the distal end point Pt of the measurement tool 14 is determined so that the measurement posture in which the position measurement error that can sufficiently offset the positioning error in the working posture J _s is determined. _k is set to a large value.

As a specific numerical value of the weight value w _k , for example, an eigenvalue of an inverse matrix of the Jacobian matrix can be used. Equation 2 is an equation of motion using a Jacobian matrix.

  The velocity vector of the tip point is a velocity vector of the tip point of the robot (for example, the center point of the flange 10g at the tip of the robot 10).

When the inverse of the Jacobian matrix is applied to both sides of Equation 2, Equation 3 is obtained.

  The eigenvalue of the inverse Jacobian matrix corresponds to the distribution of each joint that determines the joint velocity vector. That is, it is possible to obtain a solution in which a joint corresponding to a large eigenvalue moves greatly and a joint corresponding to a small eigenvalue moves small. A joint corresponding to a large eigenvalue, that is, a joint that moves greatly, can be interpreted as making a large contribution to the velocity vector at the tip of the robot, so the eigenvalue of the inverse matrix of the Jacobian matrix can be used as the weight value.

  Up to this point, the present invention has been described conceptually. Embodiments according to the present invention will be described below.

  FIG. 4 is a schematic configuration diagram of the controller 16 of the robot 10.

  The controller 16 of the robot 10 includes a posture control unit 50 that controls the posture of the robot 10, a tip point position calculation unit 52 that calculates the tip point position of the measurement tool 14, and a robot when working on the workpiece W. The work posture data acquisition unit 54 that acquires 10 work posture data, the measurement posture calculation unit 56 that calculates the measurement posture when measuring the measurement points of the marker 20, and external signals (control signals) to the positioner 12. An external signal output unit 58 for outputting, an external shaft position / orientation calculating unit 60 for calculating the position / orientation of the rotation axis Ar (external shaft) of the positioner 12, and a storage unit 62 are provided.

  The controller 16 also has a teaching pendant 64 for an operator to manually operate the robot 10.

  The posture control unit 50 controls the posture of the robot 10 by changing the joint angles of the joints 10 a to 10 f by controlling the motors 70 a to 70 f that drive the joints 10 a to 10 f of the robot 10.

  The tip point position calculation unit 52 calculates the position of the tip point Pt of the measurement tool 14 based on the detection values of the encoders 72a to 72f that detect the joint angles of the robot joints 10a to 10f. The link length of the links 10 h to 10 m, the distance from the tip point Pt of the measurement tool 14 to the flange 10 g, and the like necessary for calculation at the position of the tip point Pt are stored in the storage unit 62.

  The work posture data acquisition unit 54 is configured to acquire work posture data created by, for example, an offline teaching tool. The off-line teaching tool uses, for example, the CAD data of the robot 10, the positioner 12, and the workpiece W to teach data (operation program) of the robot 10 that performs work on the workpiece W gripped by the positioner 12 on a computer. ) Is a tool to create. The controller 16 is configured to be able to control the robot 10 based on teaching data created by an offline teaching tool. The work posture data acquisition unit 54 is, for example, a device that can read from and write to a storage medium, and receives teaching data as work posture data by reading the teaching data stored in the storage medium.

  In addition or alternatively, the work posture data acquisition unit 54 may acquire the work posture data by online teaching. An operator manually operates the robot 10 to be in a working posture via the teaching pendant 64, and obtains working posture data based on detection values of the encoders 72a to 72f in the robot 10 in the working posture state by manual operation.

  When teaching data (operation program) of the robot 10 when working on the workpiece W already exists, the working posture data acquisition unit 54 may acquire the working posture data from the teaching data.

  The measurement posture calculation unit 56 is configured to calculate the measurement posture of the robot 10 that measures the position of the measurement point Pm of the marker 20 of the positioner 12 based on the work posture data acquired by the work posture data acquisition unit 54. Yes. As described above, a measurement posture similar to the work posture corresponding to the work posture data is calculated.

  The external signal output unit 58 is configured to output an external signal to the positioner 12. Specifically, a control signal for rotating the work table 18 around the rotation axis Ar is output. Details will be described later.

  The external shaft position / orientation calculation unit 60 is configured to calculate a relative position / orientation of the rotation axis Ar of the positioner 12 with respect to the robot 10. Details will be described later.

  Next, the flow of a method for calculating the relative position and orientation of the rotation axis Ar of the positioner 12 with respect to the robot 10 by the controller 16 will be described with reference to FIG.

  First, as shown in FIG. 5, as a first step (step S <b> 1), the measurement tool 14 is attached to the flange 10 g at the tip of the robot 10. Further, a marker 20 is attached to the work table 18 of the positioner 12 (see FIG. 1).

  Next, in step S2, the tip 20 Pt of the measurement tool 14 attached to the flange 10g of the robot 10 is manually set via the teaching pendant 64 of the operator, and the marker 20 attached to the work table 18 of the positioner 12. Align to the measurement point Pm. Note that the posture in the alignment state at this time is changed in a later step, and may be any posture. For example, as shown in FIG. 2 (B), the posture may be a state in which a portion extending from the joint 10e extends in the horizontal direction.

  In subsequent step S3, the work posture data acquisition unit 54 acquires the work posture data.

In step S <b> 4, the measurement posture calculation unit 56 calculates a measurement posture when calculating the position of the measurement point Pm of the marker 20 based on the work posture data acquired by the work posture data acquisition unit 54. Specifically, first, as described above, the work posture data for each of a plurality of postures (measurable postures J _i ) in a state where the tip point Pt of the measurement tool 14 is aligned with the measurement point Pm of the marker 20. The degree of similarity D (J _i , J _s ) shown in Formula 1 with respect to the work posture J _s corresponding to is calculated. Then, the measurable posture J _i having the smallest value of the calculated similarity D (J _i , J _s ) is determined as the measurement posture.

In step S5, the controller 16 measures the orientation calculation unit 56 in Step 4 is a measurement posture calculated, to change through the orientation control section 50. At this time, when the tip point Pt of the measurement tool 14 is aligned with the measurement point Pm of the marker 20 while the joint angle of the joints 10a to 10f is adjusted , the position is aligned in step 2 Is changed to a measurement posture. For example, the measurement posture shown in FIG.

In step S <b> 6, the controller 16 calculates the position of the tip point Pt of the measurement tool 14 attached to the robot 10 in the measurement posture in step 5 via the tip point position calculation unit 52.

In step S7, the co cement roller 16 based on the position of the tip point Pt of the measurement tool 14 calculated in step 6, to calculate the measurement point Pm of the marker 20.

  The controller 16 executes steps S <b> 2 to S <b> 7 shown in FIG. 5 for each posture of the different work table 18. Therefore, the controller 16 rotates the work table 18 of the positioner 12 by a predetermined amount about the rotation axis Ar via the external signal output unit 58 every time steps S2 to S7 are completed. Then, the controller 16 announces the operator, for example, via the teaching pendant 64 so as to align the tip point Pt of the measurement tool 14 with the measurement point Pm of the marker 20.

  When steps S2 to S7 are executed for each posture of the different work table 18, the positions of different measurement points Pm are calculated. Since the distance from the measurement point Pm to the rotation axis Ar is constant and known (stored in the storage unit 62), the external axis position / orientation calculation unit 60 of the controller 16 determines the positions of a plurality of different measurement points Pm. Based on the above, the position and orientation of the rotation axis Ar of the positioner 12 are calculated.

  The relative position and orientation of the rotation axis Ar of the positioner 12 calculated by such a flow with respect to the robot 10 is output (provided) to the outside of the controller 16 as, for example, relative position and orientation data. For example, it is provided to an offline teaching tool. Thus, the offline teaching tool creates teaching data for causing the robot 10 to work with high accuracy on the workpiece W gripped by the positioner 12 based on the provided relative position and orientation data of the rotation axis Ar of the positioner 12. can do. As a result, the controller 16 that has received the teaching data from the off-line teaching tool can cause the robot 10 to execute a highly accurate operation.

  Further, the relative position and orientation of the rotation axis Ar of the positioner 12 with respect to the robot 10 is calculated periodically, for example, before starting the work on the work W, and the work on the work W is determined based on the calculation result. The teaching data stored in the storage unit 62 of the controller 16 can be updated. Accordingly, the controller 16 can cause the robot 10 to perform a highly accurate operation based on the teaching data stored in the storage unit 62.

  According to the present embodiment, when the relative position and orientation of the rotation axis Ar of the positioner 12 with respect to the robot 10 is measured, the measurement posture of the robot 10 performs work on the workpiece W held by the positioner 12. Therefore, the position measurement error and positioning error of the robot 10 can be sufficiently offset. As a result, the robot 10 can perform the work on the workpiece W gripped by the positioner 12 with high accuracy.

  Although the present invention has been described with reference to the above-described embodiments, the present invention is not limited to the above-described embodiments.

  For example, in the case of the above-described embodiment, the positioner 12 changes the posture of the workpiece W by rotating the workpiece W around the rotation axis Ar, but the present invention is not limited to this.

  For example, the positioner may translate the workpiece W along the linear motion axis. In this case, a measurement point is defined at a predetermined position with respect to the linear motion axis. For example, a measurement point is defined by attaching a marker to a work table that translates along a linear motion axis.

  If the position of the measurement point is moved a plurality of times along the linear motion axis and the position of the measurement point is calculated in the same manner as in the above-described embodiment each time the measurement point is moved, A correct position and orientation can be calculated.

Further, in the case of the above-described embodiment, the similarity of the measurable posture with respect to the working posture is calculated by the equation shown in Equation 1, but is not limited thereto. In Equation 1, the joint angle q _i measurable posture J _{i, k} and working posture J _s joint angles q _s, the difference between _k (corresponding to the "first value" described in claims) is , Squares are applied to all joints (k = 1 to n), but this is not restrictive. For example, in greatly contributes joint displacement of the tip point Pt of the measurement tool 14, measurable posture J _i of the joint angle q _{i, k} and working posture J _s joint angles q _s, the difference between _k 3 cube Mr. May be.

  Furthermore, in the case of the above-described embodiment, the controller calculates the measurement posture of the robot and the relative position and posture of the rotation axis of the positioner or the linear motion axis with respect to the robot, but this is not a limitation. For example, a computer connected to the controller may calculate the measurement posture of the robot and the relative position and posture of the rotation axis of the positioner or the linear motion axis with respect to the robot.

  For example, the computer obtains the CAD data of the robot and the positioner and the work posture data (teaching data that teaches the work posture) of the robot, and uses these data to teach the measurement posture (measurement posture) as described above. Teaching data) to be calculated. Then, the computer outputs the calculated teaching data to the controller.

  The controller controls the robot in a state in which the tip point of the measurement tool is aligned with the measurement point of the marker in advance by the manual operation of the worker based on the teaching data received from the computer. After controlling to the working posture, the controller calculates the position of the tip point of the measurement tool, and further calculates the position of the marker measurement point based on the position of the tip point of the measurement tool. The calculated measurement point position data is output to a computer. Then, the computer calculates the relative position and orientation of the rotation axis of the positioner or the linear motion axis with respect to the robot based on the position data of the measurement points received from the controller.

  Finally, supplementally, in the case of the above-described embodiment, as shown in FIG. 1, the robot 10 includes torsional joints 10a, 10d, and 10f and bending joints 10b, 10c, and 10e. It is clear that the present invention can be applied even to a robot having a joint.

  In the present invention, “similar” includes “same”. In other words, the measurement posture when measuring the position of the measurement point Pm may be the same posture as the work posture with respect to the workpiece W. The above embodiment will be described as an example. When the position of the measurement point Pm of the marker 20 and the work start point Pw of the workpiece W are the same with respect to the rotation axis Ar of the positioner 12, the measurement posture is the same as the work posture. It becomes the posture of.

  The present invention measures the relative position and orientation of a positioner that rotates or translates a workpiece with respect to a rotation axis or a linear motion axis, but the position and orientation of the workpiece cannot be changed. When the position of an arbitrary point on the workpiece is measured by a robot that performs work on the workpiece, the present invention is also applicable.

10 Robot 10a to 10f Joint 12 Positioner Ar Rotation axis Pt Reference point (tip point)
Pm Measuring point W Workpiece

Claims (5)

A method for measuring an external axis of a robot that measures a relative position and orientation of a rotation axis or a linear movement axis of a positioner that grips a workpiece to be operated by the robot, which is an external axis of the robot,
The posture of the robot when the reference point of the robot is manually aligned with the measurement point defined at a predetermined position with respect to the rotation axis or the linear motion axis of the positioner, and the state where the reference point is aligned with the measurement point. Change to the measurement posture while maintaining,
As the measurement posture of the robot ,
(1) At each joint, a difference value between a joint value at the work posture when performing a work on a work gripped by the positioner and a joint value at the measurement posture;
(2) Based on predefined weight values for each joint,
Determine a posture with a high degree of similarity to the working posture ,
Calculate the position of the measurement point of the positioner by calculating the position of the reference point in the robot in the measurement posture state,
A method for measuring an external axis of a robot that calculates the position and orientation of a rotation axis or a linear movement axis of a positioner based on the calculated position of a measurement point of the positioner . For each of the multiple measurement postures of the robot that can align the reference point with the measurement point,
(1) For each joint, a first value is calculated as a difference value between the joint value at the work posture and the joint value at the measurement posture;
(2) For each joint, calculate the second value by multiplying the square value of the first value by the weight value,
(3) The second value of each joint is summed to calculate the third value,
The method for measuring an external axis of a robot according to claim 1, wherein a measurement posture having a minimum third value is determined.   The method for measuring an external axis of a robot according to claim 1 or 2, wherein the weight value is set to a larger value for a joint that greatly displaces the reference point of the robot when the joint value changes. A robot teaching data creation method for creating teaching data of an articulated robot that performs work on a workpiece held by a positioner that rotates or translates the workpiece with respect to a rotation axis or a linear motion axis. ,
A relative position / orientation of the rotation axis or linear motion axis of the positioner calculated by the method for measuring the external axis of the robot according to any one of claims 1 to 3 is used for a workpiece gripped by the positioner. A teaching data creation method for a robot that creates teaching data for performing work on the robot. A controller for an articulated robot that performs work on the workpiece held by a positioner that rotates or translates the workpiece with respect to a rotation axis or a linear movement axis,
Work posture data acquisition means for acquiring work posture data corresponding to the work posture of the robot when performing work on the workpiece;
Robot operation means for aligning the reference point of the robot with a measurement point defined at a predetermined position with respect to the rotation axis or linear motion axis of the positioner by the operation of the operator;
Measurement posture determination means for calculating the measurement posture of the robot in a state where the reference point is aligned with the measurement point based on the work posture data acquired by the work posture data acquisition means;
Measuring point position calculating means for calculating the position of the measurement point of the positioner in the state of the measuring attitude calculated by the measuring attitude determining means;
Measurement posture determination means, as the measurement posture,
(1) For each joint, a difference value between the joint value of the work posture data and the joint value at the measurement posture;
(2) Based on predefined weight values for each joint,
A robot controller that determines a posture with a high degree of similarity to the working posture.

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