JP2019098409A - Robot system and calibration method - Google Patents

Abstract

To provide a robot system and a calibration method each of which enables work for calibration between a camera coordinate and a robot coordinate to be easily and quickly performed and enables mistake of the work to be reduced.SOLUTION: The robot system according to the present embodiment comprises: an imaging part that acquires first image data of a plurality of markers on a table; an imaging control part that acquires first camera coordinate values of the plurality of markers on the basis of the first image data; a robot control part that acquires first robot coordinate values of the plurality of markers when a calibration jig provided at a tip of an arm is positioned above the plurality of markers; and a memorizing part that acquires the first camera coordinate values and the first robot coordinate values from the imaging control part and the robot control part and memorizes a conversion equation derived by a calculating part that derives the conversion equation in which the coordinate values of the camera coordinate system are converted to the coordinate values of the robot coordinate system on the basis of the first camera coordinate values and the first robot coordinate values.SELECTED DRAWING: Figure 4

Description

  Embodiments in accordance with the present invention relate to robot systems and calibration methods.

  A robot system combining an industrial robot and a two-dimensional vision system is used. For example, first, the camera included in the two-dimensional vision system captures an image of a workpiece, and the two-dimensional vision system acquires coordinate values of the workpiece. Thereafter, the robot arm may move to perform work based on the acquired coordinate values of the workpiece. At this time, the reference of coordinates is different between the coordinates viewed from the camera (camera coordinates) and the coordinates viewed from the robot (robot coordinates). Therefore, the coordinate values of the same workpiece are different between the camera coordinates and the robot coordinates. Therefore, it is necessary to convert camera coordinates into robot coordinates. The work of introducing the determinant used for the operation of this transformation is called calibration work.

  However, this calibration work requires a long time since the number of operation steps is large and time-consuming. In addition, the operation procedure is complicated, and the user manually records data etc., so there are many operation errors.

JP, 2014-180720, A

  A robot system and calibration method capable of performing calibration work between camera coordinates and robot coordinates easily and quickly and reducing work errors.

  The robot system according to the present embodiment controls a robot having an arm, an imaging unit that acquires first image data of a plurality of markers on a table on which a workpiece can be placed, and an imaging unit, and is based on the first image data. And an imaging control unit that acquires first camera coordinate values of a plurality of markers in the camera coordinate system that is a coordinate system in an image captured by the imaging unit; and a robot that controls the calibration provided at the tip of the arm A robot control unit that acquires first robot coordinate values of a plurality of markers in a robot coordinate system that is a coordinate system based on a robot when the jig is positioned above the plurality of markers, an imaging control unit, and a robot A first camera coordinate value and a first robot coordinate value are obtained from the control unit, and a camera coordinate system is obtained based on the first camera coordinate value and the first robot coordinate value. And a storage unit that stores the conversion formula derived by the arithmetic unit for deriving a conversion equation for converting the coordinate values to coordinate values of the robot coordinate system.

BRIEF DESCRIPTION OF THE DRAWINGS The figure which shows an example of a structure of the robot system by 1st Embodiment. The figure which shows the coordinate acquisition of the tool coordinate system in a SCARA robot. Figure of the table and the plurality of markers, viewed from above the table. The block diagram which shows an example of the flow of data from acquisition of a robot coordinate value and a camera coordinate value to preservation of a conversion type. Flow chart showing an example of the operation of the robot system according to the first embodiment The figure which shows an example of a structure of the robot system by 2nd Embodiment. The figure which shows the coordinate acquisition of the tool coordinate system in a vertical articulated robot. The schematic diagram which shows the inclination of the table by 3rd Embodiment. FIG. 13 is a flow chart showing an example of the operation of the robot system according to the third embodiment. Flow chart showing an example of the operation of a robot system according to a modification

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings. This embodiment does not limit the present invention. In the specification of the application and the drawings, the same elements as those described above with reference to the drawings are denoted by the same reference numerals, and the detailed description will be appropriately omitted.

First Embodiment
FIG. 1 is a view showing an example of the configuration of a robot system 100 according to the first embodiment. The robot system 100 includes a SCARA robot 1, a robot controller 2, an operation unit 3, an imaging unit 5, a vision controller 6, a display unit 7, a terminal 8, an operation unit 9, and a LAN (Local Area Network). And a hub 10.

  The SCARA robot 1 as a robot has an arm, and in a normal operation, the arm is operated to hold or process a work placed on, for example, the table 4. At this time, the SCARA robot 1 determines the position of the arm or the like based on the image data captured by the imaging unit 5. When the camera coordinate system indicating the position in the image captured by the imaging unit 5 and the robot coordinate system indicating the position of the arm of the SCARA robot 1 deviate from each other, the SCARA robot 1 grips the workpiece accurately or processes it. Can not do it. Therefore, calibration is performed before normal operation. The calibration is to derive a conversion equation for converting coordinate values of the camera coordinate system into coordinate values of the robot coordinate system. The camera coordinate system is a coordinate system used to indicate the position in the image captured by the imaging unit 5. Here, the robot coordinate system is a coordinate system based on the tip of the arm of the SCARA robot 1. Thus, the robot coordinate system is used to indicate the position of the tip of the arm. The SCARA robot 1 is not limited to the SCARA robot, and may be a robot having a similar function.

  The table 4 can carry a plurality of markers 18 used for work or calibration. In normal operation, the work is on the table 4. Here, a plurality of markers 18 are on the table 4 because calibration is performed.

  In the calibration, a calibration jig 11 is provided at the tip of the arm of the SCARA robot 1. The calibration jig 11 is attached so as to be parallel to the Z axis 1 a of the SCARA robot 1. The tip of the calibration jig 11 is preferably sharp. This is because the accuracy of the calibration can be improved.

  A robot controller 2 as a robot control unit is connected to the SCARA robot 1. The robot controller 2 controls the SCARA robot 1. In addition, as will be described later with reference to FIG. 4, the robot controller 2 acquires robot coordinate values based on encoder information acquired from the SCARA robot 1. The encoder information is motor angle information from an encoder attached to a motor that moves each axis of the SCARA robot 1. The robot controller 2 converts this angle information into position information of the SCARA robot 1. Robot coordinate values are included in this position information. The robot controller 2 obtains the first robot coordinate values of the plurality of markers 18 in the robot coordinate system when the calibration jig 11 is positioned above the plurality of markers 18. The robot coordinate values are X and Y coordinate values of a two-dimensional plane (XY plane) in the robot coordinate system.

  The operation unit 3 is connected to the robot controller 2. The operation unit 3 enables the scalar robot 1 to be operated manually by the user.

  The imaging unit 5 is provided above the table 4 and captures an image of the table 4. The imaging unit 5 acquires first image data of the plurality of markers 18 by imaging the plurality of markers 18. The imaging unit 5 is, for example, a two-dimensional camera. The imaging unit 5 transmits the acquired first image data to the vision controller 6.

  A vision controller 6 as an imaging control unit is connected to the imaging unit 5. The vision controller 6 controls the imaging unit 5. Further, the vision controller 6 acquires first camera coordinate values of the plurality of markers 18 in the camera coordinate system based on the first image data. The camera coordinate values are X, Y coordinate values of a two-dimensional plane (XY plane).

  The display unit 7 is connected to the vision controller 6. The display unit 7 displays the image data captured by the imaging unit 5. The display unit 7 is also used to set the vision controller 6.

  The terminal 8 is provided outside the robot controller 2 and the vision controller 6. Since the terminal 8 is used for calibration, the terminal 8 may be removed from the robot system 100 in normal operation. The terminal 8 has an arithmetic unit 9. The terminal 8 is, for example, a personal computer.

  The calculation unit 9 may be configured by, for example, one or more CPUs (Central Processor Units) and / or logic LSIs (Large Scale Integration) or the like. The computing unit 9 sends a coordinate acquisition command to the robot controller 2 and the vision controller 6 by executing the calibration program. The robot controller 2 and the vision controller 6 receive the coordinate acquisition command and acquire the first camera coordinate value and the first robot coordinate value, respectively. Then, the calculation unit 9 acquires the first camera coordinate value and the first robot coordinate value from the vision controller 6 and the robot controller 2. Furthermore, in the calibration, on the basis of the first camera coordinate value and the first robot coordinate value, the calculation unit 9 derives a conversion equation for converting the coordinate value of the camera coordinate system into the coordinate value of the robot coordinate system. The calculation unit 9 sends the conversion equation obtained by the calibration to the robot controller 2. The conversion equation is used to convert coordinate values of the camera coordinate system into coordinate values of the robot coordinate system in normal operation. The calibration program is, for example, a robot program creation support tool "TSAssist (registered trademark)" manufactured by Toshiba Machine Co., Ltd., or the like. Further, the calculation unit 9 acquires an offset of a calibration jig 11 described later, and sets a tool coordinate system.

  The LAN hub 10 is connected to the robot controller 2, the vision controller 6 and the terminal 8. As a result, as shown in FIG. 4 described later, data of camera coordinate values and robot coordinate values can be transmitted and received. The LAN hub 10 may be, for example, a hub used for Ethernet (registered trademark) or the like. The robot system 100 may not have the LAN hub 10 if it is possible to transmit and receive data of camera coordinate values and robot coordinate values by another method.

  FIG. 2 is a diagram showing coordinate acquisition of a tool coordinate system in the SCARA robot 1. A tool coordinate system is a coordinate system which shows the position of the tip of a tool on the basis of the tip of the tool provided in the tip of an arm. The tool is a calibration jig 11 in calibration. The coordinate values of the tool coordinate system have offsets corresponding to the dimensions of the calibration jig 11 with respect to robot coordinate values based on the tip of the arm. By acquiring this offset and setting the tool coordinate system, robot coordinate values can be acquired from the coordinate values of the tool coordinate system. Therefore, before calibration, it is necessary to acquire an offset with the calibration jig 11 attached and to set a tool coordinate system. The set tool coordinate system is valid until all calibration operations are completed. When the dimensions of the calibration jig 11 are known from CAD data or the like, it may be possible to omit the acquisition of the offset in the setting of the tool coordinate system.

  To obtain an offset, the distance r of the XY plane from the tip of the arm to the tip of the calibration jig 11 and the coordinate value (X0, Y0) of the reference point at which the tip of the calibration jig 11 is positioned It is. The relationship between the unknowns r, X0, and Y0 can be obtained by one posture of the arm. Therefore, three unknowns r, X0, and Y0 can be obtained by the three attitudes. Furthermore, another posture is required to confirm the determined r, X0 and Y0. Therefore, the offset can be obtained from the four postures of the arm.

  FIG. 3 is a view of the table 4 and the plurality of markers 18 as viewed from above the table 4. The plurality of markers 18 are disposed within the imaging range 17 of the imaging unit 5 as shown in FIG. The size and shape of the marker 18 may be detected by the imaging unit 5.

  The plurality of markers 18 are arranged in three rows and three columns, as shown in FIG. Thereby, distortion of an image such as a fisheye lens caused by distortion of the lens of the imaging unit 5 can be corrected. The plurality of markers 18 is not limited to nine in three rows and three columns. For example, the plurality of markers 18 may be provided to form a two-dimensional plane, such as three points that are not on a straight line. Further, it is preferable that the plurality of markers 18 be arranged at equal intervals. This can improve the accuracy of the calibration. Moreover, it is preferable that the plurality of markers 18 be provided in a wide range within the imaging range 17. This enables calibration over a wide range. Further, the height of the marker 18 needs to be substantially the same as the height of the work.

  FIG. 4 is a block diagram showing an example of the flow of data from acquisition of robot coordinate values and camera coordinate values to storage of a conversion equation. The SCARA robot 1 includes an encoder 21. The robot controller 2 includes a position information acquisition unit 13, a data relay unit 19, and a storage unit 20. The calculation unit 9 includes a robot coordinate acquisition unit 14, a camera coordinate acquisition unit 15, and a conversion expression calculation unit 16.

  First, the flow of data when acquiring the first camera coordinate value will be described. The camera coordinate acquisition unit 15 transmits a camera coordinate acquisition command to the data relay unit 19 according to a user's command. The data relay unit 19 converts the camera coordinate acquisition command from the robot format to the vision format, and transmits it to the vision controller 6. When receiving the camera coordinate acquisition command, the vision controller 6 causes the imaging unit 5 to image the marker 18 and receives the first image data from the imaging unit 5. The vision controller 6 acquires a first camera coordinate value based on the first image data. The vision controller 6 transmits the first camera coordinate value to the data relay unit 19. The data relay unit 19 converts the first camera coordinate value from the vision format to the robot format, and transmits the first camera coordinate value to the camera coordinate acquisition unit 15. The camera coordinate acquisition unit 15 stores the first camera coordinate value. The camera coordinate acquisition unit 15 executes the above-described procedure for nine points of the marker 18. That is, the camera coordinate acquisition unit 15 acquires the first camera coordinate values for each point. The camera coordinate acquisition unit 15 transmits the first camera coordinate values for nine points to the conversion equation calculation unit 16. The above format conversion is required when the data format differs between the robot controller 2 and the vision controller 6. Therefore, when the data format is the same, the format may not be converted.

  Next, the flow of data when acquiring the first robot coordinate value will be described. The calibration jig 11 is positioned above the marker 18. The robot coordinate acquisition unit 14 transmits a robot coordinate acquisition command to the position information acquisition unit 13 according to a user's command. The position information acquisition unit 13 receives encoder information that the encoder 21 intermittently transmits. The position information acquisition unit 13 converts encoder information into position information of the scalar robot 1. When receiving the robot coordinate acquisition command, the position information acquisition unit 13 transmits X and Y coordinate values in the converted position information as the first robot coordinate value to the robot coordinate acquisition unit 14. The robot coordinate acquisition unit 14 stores the first robot coordinate values. The robot coordinate acquisition unit 14 executes the above-described procedure for nine points of the marker 18. That is, the positioning of the calibration jig 11 and the acquisition of the first robot coordinate value are performed for each marker 18. The robot coordinate acquisition unit 14 transmits the first robot coordinate values for nine points to the conversion equation calculation unit 16.

  Next, the conversion equation calculation unit 16 derives a conversion equation based on the first camera coordinate values for nine points and the first robot coordinate values for nine points. The conversion expression calculation unit 16 transmits the conversion expression to the storage unit 20. The storage unit 20 stores the received conversion formula.

  FIG. 5 is a flow chart showing an example of the operation of the robot system 100 according to the first embodiment. The flow of data shown in FIG. 4 corresponds to steps S60 to S100 in FIG.

  First, the user arranges the plurality of markers 18 in the imaging range 17 on the table 4 (S10). Next, the vision controller 6 registers the marker 18 (S20). For example, the vision controller 6 registers image recognition information of the marker 18. Next, the user attaches the calibration jig 11 to the tip of the SCARA robot 1 (S30). Next, the calculation unit 9 acquires the offset of the calibration jig 11 (S40), and sets the tool coordinate system.

  The method of acquiring the offset of the calibration jig 11 will be described. The user sets a reference point at an arbitrary position such as above the corner of the marker 18. The user operates the SCARA robot 1 so that the tip of the calibration jig 11 is positioned above the reference point. Then, the user operates the SCARA robot 1 so as to change the posture of the arm. The user repeats this operation, and operates the SCARA robot 1 so that the position of the tip of the calibration jig 11 matches the position above the reference point in four different postures. The calculation unit 9 acquires an offset from the position information of each of the four postures of the arm.

  Next, the user aligns the calibration jig 11 above the marker 18 using the operation unit 3 (S50). Next, the calculation unit 9 acquires a first robot coordinate value according to a command of the user (S60). Next, the user operates the SCARA robot 1 so that the imaging unit 5 can capture the marker 18. Arithmetic unit 9 acquires the first camera coordinate value according to the user's command (S70). If the first camera coordinate values and the first robot coordinate values have not been acquired for all the markers 18 (NO in S80), steps S50 to S70 are executed in the next marker 18. When the first camera coordinate values and the first robot coordinate values are acquired for all the markers 18 (YES in S80), the calculation unit 9 derives a conversion formula (S90). Next, the calculation unit 9 transmits the conversion equation to the robot controller 2, and the storage unit 20 stores the conversion equation (S100).

  Alternatively, the first robot coordinate values may be acquired (S50, S60) after the acquisition of the first camera coordinate values (S70). In addition, as in steps S50 to S80, the present invention is not limited to acquiring the first camera coordinate value and the first robot coordinate value for each of the markers 18. For example, the robot coordinate acquisition unit 14 shown in FIG. 4 acquires and stores nine first robot coordinate values, and then the camera coordinate acquisition unit 15 acquires and stores nine first camera coordinate values. It is also good.

  As described above, the robot system 100 according to the first embodiment acquires the first camera coordinate values of the plurality of markers 18 based on the imaging unit 5 that acquires the first image data of the plurality of markers and the first image data. A robot controller 2 for acquiring first robot coordinate values of a plurality of markers 18 when the vision controller 6 for acquisition and the calibration jig 11 are positioned above the plurality of markers 18, a vision controller 6 and a robot controller A conversion equation for acquiring the first camera coordinate value and the first robot coordinate value from 2 and converting the coordinate value of the camera coordinate system into the coordinate value of the robot coordinate system based on the first camera coordinate value and the first robot coordinate value And a storage unit for storing the conversion formula derived by the computing unit 9 for deriving.

  Thereby, the calculation unit 9 automatically obtains the first camera coordinate value and the first robot coordinate value from the vision controller 6 and the robot controller 2 and derives a conversion equation. Therefore, the calibration work can be performed more easily and quickly than when the user manually writes down the first camera coordinate value and the first robot coordinate value and inputs the calculated conversion equation to the robot controller. And, work errors can be reduced.

  Note that although the above-described calculation unit 9 is provided outside the vision controller 6 and the robot controller 2, the vision controller 6 or the robot controller 2 may have the function of the calculation unit 9. That is, the vision controller 6 or the robot controller 2 may automatically obtain the first camera coordinate value and the first robot coordinate value to derive a conversion equation.

Second Embodiment
FIG. 6 is a view showing an example of the configuration of a robot system 100 according to the second embodiment. The second embodiment differs from the first embodiment in that the SCARA robot 1 is a vertical articulated robot 12.

  The calibration jig 11 is mounted parallel to the sixth axis 12 a of the vertical articulated robot 12. In order to acquire an offset by calculation similar to the SCARA robot 1, the Euler angles of the A, B, and C axes are set to 0 degrees.

  The other configuration of the robot system 100 according to the second embodiment is the same as the corresponding configuration of the robot system 100 according to the first embodiment, and thus the detailed description thereof will be omitted.

  FIG. 7 is a diagram showing coordinate acquisition of the tool coordinate system in the vertical articulated robot 12. As shown in FIG. In the SCARA robot 1, the coordinate value of the XY plane changes according to the angle of the arm. Coordinate values in the Z-axis direction are changed not by the angle of the arm but by moving the Z-axis 1a of the SCARA robot 1 up and down. Therefore, the offset can be obtained by determining the distance r of the XY plane and the coordinate values of the reference point of the XY plane. On the other hand, in the vertical articulated robot 12, the coordinate value of the XYZ space changes according to the angle of the arm. Therefore, it is necessary to obtain the distance r in the XYZ space and the coordinate values (X0, Y0, Z0) of the reference point in the XYZ space. That is, there are one more unknown number than the scalar robot 1. Therefore, the computing unit 9 according to the second embodiment differs from the first embodiment in that the offset is obtained from the positional information of the five postures of the arm.

  The robot system 100 according to the second embodiment can obtain the same effects as the robot system 100 according to the first embodiment.

Third Embodiment
After completion of the calibration, the plurality of markers 18 are removed from the table 4 and the work is placed on the table 4. When the table 4 is inclined, a shift may occur between the coordinate value of the workpiece converted from the camera coordinate value to the robot coordinate value and the coordinate value of the actual workpiece.

  FIG. 8 is a schematic view showing the inclination of the table 4 according to the third embodiment. FIG. 8 is a view seen from the Y-axis direction. The table 4 is inclined at an angle θo from the plane P perpendicular to the optical axis 22 of the imaging unit 5. The plane P is at a position away from the imaging unit 5 by the focal length ZL of the imaging unit 5 in the Z-axis direction. It is assumed that the work is at point S on the table 4. The imaging unit 5 images a workpiece and acquires second image data of the workpiece. The vision controller 6 acquires a second camera coordinate value of the workpiece based on the second image data. The vision controller 6 acquires, as a second camera coordinate value, a point Sf which is an intersection point of a straight line connecting the point O of the imaging unit 5 and the point S and the plane P. The robot controller 2 converts the second camera coordinate value into a workpiece conversion coordinate value of a workpiece by a conversion formula. This workpiece conversion coordinate value is also the point Sf. Therefore, as shown in FIG. 8, when the table 4 is inclined, a deviation of coordinate values occurs between the point S which is the actual position of the workpiece and the point Sf which is the workpiece conversion coordinate value. In this case, the SCARA robot 1 may not be able to grip the workpiece.

  In the first embodiment and the second embodiment, the deviation of the coordinate values due to the inclination of the table 4 is not taken into consideration. On the other hand, in the third embodiment, as described below, a corrected coordinate value in which the deviation of the coordinate value due to the inclination of the table 4 is corrected is calculated.

  In calibration, a pressure sensor is provided on the top of the plurality of markers 18 or at the tip of the calibration jig 11. The pressure sensor detects that the calibration jig 11 contacts the marker 18 when the calibration jig 11 is displaced in the vertical direction. The pressure sensor may be connected to the robot controller 2 and send the robot controller 2 that the calibration jig 11 has touched the marker 18. The sensor is not limited to the pressure sensor, and may be a sensor that can detect that the calibration jig 11 contacts the marker 18.

  The robot controller 2 acquires vertical robot coordinate values when the pressure sensor detects that the calibration jig 11 has been brought into contact with the plurality of markers 18. The vertical robot coordinate values indicate the heights of the plurality of markers 18 in the Z-axis direction perpendicular to the robot coordinate system, which is a two-dimensional plane (XY plane). The vertical robot coordinate values are not used for calibration.

  In the normal operation, the robot controller 2 calculates a three-dimensional plane equation of the table 4 based on the first robot coordinate values and the vertical robot coordinate values at the markers 18 for nine points.

  On the other hand, the robot controller 2 calculates a straight line O-Sf connecting the point O and the point Sf. The robot controller 2 calculates an intersection point of the plane equation of the table 4 and the straight line O-Sf as a workpiece correction coordinate value of the workpiece. That is, the robot controller 2 calculates a workpiece correction coordinate value based on the plane equation of the table 4 and the workpiece conversion coordinate value. The workpiece correction coordinate value calculated in this manner is the coordinate value of the point S.

  The other configuration of the robot system 100 according to the third embodiment is the same as the corresponding configuration of the robot system 100 according to the first embodiment, and thus the detailed description thereof will be omitted.

  Next, calculation of workpiece correction coordinate values will be described.

  The plane equation of Table 4 is ax + by + cz + d = 0, the coordinate value of point O is (xv, yv, zv), the coordinate value of point Sf is (xsf, ysf, zsf), and the coordinate value of point S is (xsc, ysc, zsc) The coordinate values (xv, yv, zv) of the point O are measured when the imaging unit 5 is attached. The X and Y components (xsf, ysf) of the point Sf are workpiece transformation coordinate values. The Z component zsf of the point Sf is zv + ZL as shown in FIG. The focal length ZL is also measured when the imaging unit 5 is attached.

The direction vector of the straight line O-Sf is expressed by Equation 1.

Therefore, the equation of the straight line O-Sf is expressed by Equation 2.

Assuming that the equation 2 is the equation 3, the equation 3 is expressed by the equations 4, 5, and 6.

Substituting equations 4, 5 and 6 into the above-described plane equation, t is obtained as represented by equation 7.

By substituting this t into the equations 4, 5 and 6, the coordinate value (xsc, ysc, zsc) of the point S which is the workpiece correction coordinate value can be calculated.

  FIG. 9 is a flow chart showing an example of the operation of the robot system 100 according to the third embodiment.

  Steps S10 to S60 in FIG. 9 are the same as steps S10 to S60 shown in FIG. 5 in the first embodiment. After acquiring the first robot coordinate values (S60), the user moves the calibration jig 11 in the Z direction. Thus, the robot controller 2 acquires vertical robot coordinate values (S65). Further, steps S70 to S100 in FIG. 9 are the same as steps S70 to S100 shown in FIG. 5 in the first embodiment.

  Next, the robot controller 2 calculates the plane equation of the table 4 based on the first robot coordinate value and the vertical robot coordinate value (S110). Next, the imaging unit 5 captures an image of a workpiece to obtain second image data. The vision controller 6 acquires a second camera coordinate value based on the second image data (S120). Next, the robot controller 2 receives the second camera coordinate value from the vision controller 6. The robot controller 2 converts the second camera coordinate values into workpiece conversion coordinate values by the conversion formula (S130). The robot controller 2 calculates a workpiece correction coordinate value in which the deviation of the coordinate value due to the inclination of the table 4 is corrected based on the plane equation of the table 4 and the workpiece conversion coordinate value (S140).

  In addition, for a shift in the Z-axis direction between the point S and the point Sf, for example, when a tool for gripping a workpiece by suction is provided, the shift in the Z-axis direction can be reduced by providing a spring mechanism on the tool. It can be absorbed. Also, for example, in robot teaching, the Z component corresponding to the X and Y components can be programmed.

  As described above, according to the robot system 100 according to the third embodiment, the robot controller 2 is perpendicular to the robot coordinate system, which is a two-dimensional plane, when the calibration jig 11 is brought into contact with the plurality of markers 18. Vertical robot coordinate values indicating the heights of the plurality of markers 18 in the direction are acquired. The robot controller 2 calculates the plane equation of the table 4 based on the first robot coordinate value and the vertical robot coordinate value. The robot controller 2 calculates the workpiece correction coordinate value of the workpiece in which the deviation of the coordinate value due to the inclination of the table 4 with respect to the plane P perpendicular to the optical axis 22 of the imaging unit 5 is corrected based on the plane equation and the workpiece conversion coordinate value. .

  Thereby, the robot controller 2 can position the workpiece correction coordinate value in which the deviation of the coordinate value due to the inclination of the table 4 is corrected. Therefore, even if the table 4 is inclined from the plane P, the SCARA robot 1 can grip the work.

  The third embodiment can be applied to the first embodiment and the second embodiment.

(Modification)
The modification of the third embodiment is different from the third embodiment in that it is determined whether or not the workpiece correction coordinate value is to be computed before the workpiece correction coordinate value is computed.

  In FIG. 8, it is assumed that a point Af to a point Cf in the plane P is the imaging range 17 of the imaging unit 5. The angles θa and θc which are the angles of the imaging range 17 are the same angle. The image data does not fall outside the range from point A to point C in Table 4. Therefore, when the user views the image data, the point Af (point A) and the point Cf (point C) are the farthest portions from the optical axis 22 of the imaging unit 5 on the table 4.

  Further, the point at which the optical axis 22 intersects the table 4 is a point Q. When point Q, point S and point C are compared, as the distance from the optical axis 22 increases, the deviation of the coordinate value due to the inclination of the table 4 increases. The robot controller 2 according to the modification compares the deviation of the coordinate values with the positioning accuracy of the SCARA robot 1 at the farthest point (point A, point C) where the deviation of the coordinate values is maximum. From the result of this comparison, the robot controller 2 determines whether to calculate a workpiece correction coordinate value.

  The positioning accuracy is the variation width of the coordinate values of the SCARA robot 1 whose position is actually controlled when positioning is performed at a certain coordinate value. The positioning accuracy is, for example, stored in advance in the storage unit 20. For example, it is assumed that the positioning accuracy is ± 0.1 mm. When the maximum deviation of the coordinate values due to the inclination of the table 4 exceeds the range of ± 0.1 mm, the deviation of the coordinate values due to the inclination of the table 4 is so large that it can not be ignored. In this case, the robot controller 2 calculates a workpiece correction coordinate value. On the other hand, when the maximum deviation of the coordinate values due to the inclination of the table 4 is so small as to fall within the range of ± 0.1 mm, the deviation of the coordinate values due to the inclination of the table 4 is so small that it can be ignored. In this case, the robot controller 2 does not calculate the workpiece correction coordinate value.

  The farthest part is selected by the user from the end of the imaging range 17 in FIG. For example, assuming that the position of the optical axis 22 is at the center of the imaging range 17, the user selects the top, bottom, left, and right at the end of the imaging range 17 as the farthest part. Moreover, it is also possible to make a determination using a plurality of farthest parts.

  In the following, it is assumed that the user selects point Af in FIG. 8 as the farthest part.

  The imaging unit 5 acquires the third image data of the table 4 by imaging the table 4.

  The robot controller 2 acquires the third camera coordinate value of the farthest point (point Af) from the optical axis 22 on the table 4 based on the third image data. The robot controller 2 converts the third camera coordinate value into the farthest converted coordinate value of the farthest portion (point Af) by the conversion equation.

  The robot controller 2 calculates a straight line O-Af connecting the point O and the point Af. The robot controller 2 calculates the intersection point of the plane equation of the table 4 and the straight line O-Af as the farthest part corrected coordinate value of the farthest part. That is, the robot controller 2 calculates the farthest part correction coordinate value based on the plane equation of the table 4 and the farthest part conversion coordinate value. The farthest part correction coordinate value calculated in this manner is the coordinate value of the point A.

  The coordinate value (xac, yac, zac) of the point A which is the farthest part correction coordinate value is the farthest part conversion coordinate instead of the workpiece conversion coordinate value (xsf, ysf) in the expressions 4, 5, 6, 7. It can be calculated by using the values (xaf, yaf).

  The robot controller 2 compares the difference between the farthest part conversion coordinate value and the farthest part correction coordinate value with the positioning accuracy of the SCARA robot 1.

  When the difference between the farthest part conversion coordinate value and the farthest part correction coordinate value exceeds the range of the positioning accuracy, the robot controller 2 calculates the work correction coordinate value as in the third embodiment. In this case, the robot controller 2 sets the workpiece correction coordinate value as the coordinate value of the workpiece.

  On the other hand, when the difference between the farthest part conversion coordinate value and the farthest part correction coordinate value is within the range of the positioning accuracy, the robot controller 2 does not calculate the work correction coordinate value. In this case, the robot controller 2 sets the workpiece conversion coordinate value as the coordinate value of the workpiece.

  The other configuration of the robot system 100 according to the modification is the same as the corresponding configuration of the robot system 100 according to the third embodiment, and thus the detailed description thereof will be omitted.

  FIG. 10 is a flowchart showing an example of the operation of the robot system 100 according to the modification.

  Steps S10 to S60, S65, and S70 to S130 in FIG. 10 are the same as steps S10 to S60, S65, and S70 to S130 shown in FIG. 9 in the third embodiment.

  Next, the imaging unit 5 captures an image of the table 4 and acquires third image data. The vision controller 6 acquires a third camera coordinate value based on the third image data (S132). Next, the robot controller 2 receives the third camera coordinate value from the vision controller 6. The robot controller 2 converts the third camera coordinate value to the farthest part converted coordinate value by the conversion formula (S134). Next, the robot controller 2 calculates the farthest-portion corrected coordinate value in which the deviation of the coordinate value due to the inclination of the table 4 is corrected based on the plane equation of the table 4 and the farthest-portion converted coordinate value (S136). Next, the robot controller 2 compares the difference between the farthest portion conversion coordinate value and the farthest portion correction coordinate value with the positioning accuracy of the SCARA robot 1 (S138). If the difference between the farthest part conversion coordinate value and the farthest part correction coordinate value exceeds the positioning accuracy (YES in S138), the robot controller 2 calculates a work correction coordinate value (S140). Step S140 in FIG. 10 is similar to step S140 shown in FIG. 9 in the third embodiment. The robot controller 2 sets the workpiece correction coordinate value as the coordinate value of the workpiece. If the difference between the farthest part conversion coordinate value and the farthest part correction coordinate value is within the range of the positioning accuracy (NO in S138), the robot controller 2 does not calculate the work correction coordinate value, and the first replacement coordinate value Is the coordinate value of the work.

  As described above, according to the robot system 100 according to the modification, the robot controller 2 corrects the deviation of the coordinate value due to the inclination of the table 4 based on the plane equation and the farthest part transformed coordinate value. Calculate the far part correction coordinate value. The robot controller 2 compares the difference between the second permuted coordinate value and the farthest part corrected coordinate value with the positioning accuracy of the SCARA robot 1. When the difference between the second substituted coordinate value and the farthest part correction coordinate value exceeds the positioning accuracy, the robot controller 2 calculates the work correction coordinate value of the workpiece, and sets the workpiece correction coordinate value as the coordinate value of the workpiece. When the difference between the second replacement coordinate value and the farthest part correction coordinate value is within the range of the positioning accuracy, the robot controller 2 sets the workpiece conversion coordinate value as the coordinate value of the workpiece.

  Thus, the robot controller 2 can not perform the correction when the correction is unnecessary.

  In the third embodiment, the robot controller 2 calculates a workpiece correction coordinate value for each workpiece without making a determination. Since calculation of the work correction coordinate value takes a processing time, if the inclination of the table 4 is small and the correction is unnecessary, the cycle time is unnecessarily lengthened.

  On the other hand, in the modification, the robot controller 2 does not calculate the work correction coordinate value when it is determined that the inclination of the table 4 is small and the correction is unnecessary before the calculation of the work correction coordinate value. Thereby, the cycle time when the correction is unnecessary can be made shorter than in the third embodiment.

  At least a part of the calibration method according to the present embodiment may be configured by hardware or may be configured by software. When configured by software, a program for realizing at least a part of the functions of the method may be stored in a recording medium such as a flexible disk or a CD-ROM, and read by a computer for execution. The recording medium is not limited to a removable medium such as a magnetic disk or an optical disk, and may be a fixed recording medium such as a hard disk drive or a memory. In addition, a program for realizing at least a part of the functions of the data processing method may be distributed via a communication line (including wireless communication) such as the Internet. Furthermore, the program may be encrypted, modulated, compressed, or stored in a recording medium via a wired line or a wireless line such as the Internet or may be distributed.

  While certain embodiments of the present invention have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the invention. These embodiments can be implemented in other various forms, and various omissions, replacements, and modifications can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the invention described in the claims and the equivalents thereof as well as included in the scope and the gist of the invention.

1 SCARA ROBOT, 2 ROBOT CONTROLLER, 3 OPERATING UNIT, 4 TABLE, 5 IMAGING UNIT, 6 VISION CONTROLLER, 7 DISPLAY UNIT, 8 TERMINAL, 9 CALCULATION UNIT, 11 CALIBRATION JIG, 18 MARKER, 20 STORAGE UNIT, 22 OPTICAL AXIS , P plane, ZL focal length

Claims (9)

A robot having an arm,
An imaging unit that acquires first image data of a plurality of markers on a table on which a workpiece can be placed;
An imaging control unit that controls the imaging unit and acquires, based on the first image data, first camera coordinate values of the plurality of markers in a camera coordinate system that is a coordinate system in an image imaged by the imaging unit When,
The plurality of markers in a robot coordinate system, which is a coordinate system based on the robot, when the robot is controlled and a calibration jig provided at the tip of the arm is positioned above the plurality of markers. A robot control unit that acquires a first robot coordinate value of
The first camera coordinate value and the first robot coordinate value are acquired from the imaging control unit and the robot control unit, and the coordinate value of the camera coordinate system is calculated based on the first camera coordinate value and the first robot coordinate value. A storage unit configured to store the conversion formula derived by an operation unit configured to derive a conversion formula to be converted into coordinate values of the robot coordinate system. The imaging unit acquires second image data of the work;
The imaging control unit acquires a second camera coordinate value of the work based on the second image data,
The robot system according to claim 1, wherein the robot control unit converts the second camera coordinate value into a workpiece conversion coordinate value of the workpiece according to the conversion formula. The robot control unit is a vertical robot coordinate value indicating heights of the plurality of markers in a direction perpendicular to the robot coordinate system, which is a two-dimensional plane, when the calibration jig contacts the plurality of markers. Get
The robot system according to claim 2, wherein the robot control unit calculates a plane equation of the table based on the first robot coordinate value and the vertical robot coordinate value.   The robot control unit calculates a workpiece correction coordinate value of the workpiece in which the deviation of the coordinate value due to the inclination of the table with respect to the vertical plane of the optical axis of the imaging unit is corrected based on the plane equation and the workpiece conversion coordinate value. The robot system according to claim 3. The plane equation is ax + by + cz + d = 0, the coordinate value of the imaging unit is (xv, yv, zv), the workpiece transformation coordinate value is (xsf, ysf), the focal length of the imaging unit is ZL, zv + ZL is zsf, the work correction coordinate value (xsc, ysc, zsc) is calculated by the following equation

The robot system according to claim 4. The imaging unit acquires third image data of the table,
The imaging control unit acquires a third camera coordinate value of a farthest part from the optical axis of the imaging unit on the table based on the third image data.
The robot control unit converts the third camera coordinate value into the farthest converted coordinate value of the farthest part according to the conversion formula,
The robot control unit corrects the deviation of the coordinate value due to the inclination of the table with respect to the vertical plane of the optical axis of the imaging unit based on the plane equation and the farthest part conversion coordinate value. Calculate the part correction coordinate value,
The robot control unit compares the difference between the farthest part conversion coordinate value and the farthest part correction coordinate value with the positioning accuracy of the robot.
When the difference exceeds the positioning accuracy, the robot control unit corrects the deviation of the coordinate value due to the inclination of the table with respect to the vertical plane of the optical axis of the imaging unit based on the plane equation and the workpiece conversion coordinate value. Calculating a workpiece correction coordinate value of the workpiece, and setting the workpiece correction coordinate value as a coordinate value of the workpiece;
The robot system according to claim 3, wherein when the difference is within the range of the positioning accuracy, the robot control unit sets the workpiece conversion coordinate value as the coordinate value of the workpiece. The plane equation is ax + by + cz + d = 0, the coordinate value of the imaging unit is (xv, yv, zv), the workpiece transformation coordinate value is (xsf, ysf), the focal length of the imaging unit is ZL, zv + ZL is zsf, the work correction coordinate value (xsc, ysc, zsc) is calculated by the following equation

Assuming that the farthest part conversion coordinate value is (xaf, yaf), zv + ZL is zaf, and the farthest part correction coordinate value (xac, yac, zac) is calculated by the following equation

The robot system according to claim 6.   The robot system according to any one of claims 1 to 7, wherein the plurality of markers are arranged in three rows and three columns. A robot having an arm, an imaging unit for imaging a table on which a workpiece can be placed, an imaging control unit for controlling the imaging unit, a robot control unit for controlling the robot, and an image captured by the imaging unit And a storage unit for storing a conversion formula for converting coordinate values of a camera coordinate system which is a coordinate system of the above into coordinate values of a robot coordinate system which is a coordinate system based on the robot. ,
When the calibration jig provided at the tip of the arm is positioned above the plurality of markers on the table, the robot control unit uses the first robot coordinate values of the plurality of markers in the robot coordinate system. Acquired,
Acquiring, by the imaging unit, first image data of the plurality of markers;
The imaging control unit acquires first camera coordinate values of the plurality of markers in the camera coordinate system based on the first image data,
A computing unit that obtains the first camera coordinate value and the first robot coordinate value from the imaging control unit and the robot control unit, and derives the conversion equation based on the first camera coordinate value and the first robot coordinate value Storing the conversion equation derived by the storage unit in the storage unit.

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