Calibration device, calibration method, and calibration program

Abstract

To solve the problem that it is difficult to calibrate a scanner in a rotating direction in a conventional method.SOLUTION: The calibration device according to the present invention includes a scan processing unit 31 that scans a reference block having a circular contour portion 52 having a predetermined shape on a reference surface while moving a three dimensional sensor in a Y-axis direction orthogonal to a Z-axis extending in a scan signal emission direction of the three dimensional sensor to acquire three dimensional shape data of the reference surface, a circular contour extraction processing unit 33 that extracts a shape of the circular contour portion provided on the reference surface from the three dimensional shape data as an extracted circular contour shape, a distortion amount calculation processing unit 34 that calculates a distortion amount of the extracted circular contour shape with respect to a specified shape set in advance as a shape of the circular contour portion set in advance, and a rotation angle calculation processing unit (35) that calculates a yaw rotation angle of the three dimensional sensor around the Z-axis based on the distortion amount.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to a calibration device, a calibration method, and a calibration program, and more particularly to a calibration device, a calibration method, and a calibration program for calculating the tilt of the attitude of a scanner. [Background technology]

[0002] In a sensor that acquires shape data of an object using a work robot (multi-axis articulated robot) or the like, the state of attachment to the robot may deviate from the ideal state. Therefore, Patent Document 1 discloses an example of a method for measuring a workpiece using a sensor attached to a robot.

[0003] The workpiece measurement method described in Patent Document 1 discloses a method for measuring a workpiece using a wired or wireless measuring head attached to a machine tool, which is movable relative to the workpiece in three orthogonal axial directions or two orthogonal axial directions and can change its relative angular direction relative to the workpiece using one or more rotation axes, and which includes a three-dimensional offset. Specifically, the method measures the relative position of the measuring head relative to a reference object installed at an arbitrary position multiple times while changing the relative angular direction with the measuring head, calculates the three-dimensional offset of the measuring head from changes in the combination of the relative angular direction and relative position between the measuring head and the reference object, and then measures the workpiece using the three-dimensional offset of the measuring head itself. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5595798 specification Summary of the Invention [Problem to be solved by the invention]

[0005] However, with the technology described in Patent Document 1, although it is possible to calculate the offset between the mechanical coordinates of the measuring head and the measuring instrument coordinates of the measuring head from changes in the combination of the relative angular direction and relative position between the measuring head and the reference object, there is a problem in that it is not possible to correct, for example, a deviation in the mounting angle of the measuring head. [Means for solving the problem]

[0006] One aspect of the present invention is a calibration device comprising: a scanning processing unit that scans a reference block having a circular contour portion whose shape is predetermined on a reference surface while moving a three-dimensional sensor in a Y-axis direction perpendicular to a Z-axis extending in the direction of irradiation of a scan signal from the three-dimensional sensor, thereby acquiring three-dimensional shape data of the reference surface; a circular contour extraction processing unit that extracts the shape of the circular contour portion on the reference surface from the three-dimensional shape data as an extracted circular contour shape; a distortion amount calculation processing unit that calculates the amount of distortion of the extracted circular contour shape relative to a predetermined specified shape that is a predetermined shape of the circular contour portion; and a rotation angle calculation processing unit that calculates the yaw rotation angle of the three-dimensional sensor around the Z-axis based on the amount of distortion.

[0007] One aspect of the present invention is a calibration method that uses a computer to calculate the yaw rotation angle of a three-dimensional sensor around a Z axis extending in the direction of irradiation of a scan signal from the three-dimensional sensor, using a reference block having a circular contour portion with a predetermined shape on a reference surface.The calibration method causes a computer to perform the following steps: a scanning process that scans the reference block while moving the three-dimensional sensor in a Y axis direction perpendicular to the Z axis to obtain three-dimensional shape data of the reference surface; a circular contour extraction process that extracts the shape of the circular contour portion on the reference surface from the three-dimensional shape data as an extracted circular contour shape; a distortion amount calculation process that calculates the amount of distortion of the extracted circular contour shape relative to a predetermined specified shape that is a predetermined shape of the circular contour portion; and a rotation angle calculation process that calculates the yaw rotation angle based on the distortion amount.

[0008] One aspect of the present invention is a calibration program that calculates the yaw rotation angle of a three-dimensional sensor around a Z axis extending in the direction of irradiation of a scan signal from the three-dimensional sensor using a reference block having a circular contour portion whose shape is predetermined on a reference surface.The calibration program causes a computer to execute the following steps: a scanning process that scans the reference block while moving the three-dimensional sensor in a Y axis direction perpendicular to the Z axis to obtain three-dimensional shape data of the reference surface; a circular contour extraction process that extracts the shape of the circular contour portion on the reference surface from the three-dimensional shape data as an extracted circular contour shape; a distortion amount calculation process that calculates the amount of distortion of the extracted circular contour shape relative to a predetermined shape that is predetermined as the shape of the circular contour portion; and a rotation angle calculation process that calculates the yaw rotation angle based on the distortion amount.

[0009] According to one aspect of the present invention, the magnitude of the yaw rotation angle of the scanner is calculated from the amount of distortion of the circular contour shape of the reference block obtained by measurement due to the amount of deviation of the scanner in the yaw direction. [Effects of the Invention]

[0010] According to one aspect of the present invention, it is possible to calibrate the amount of deviation in the yaw rotation angle of the scanner. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic diagram of a working robot system according to a first embodiment. [Figure 2] 3A to 3C are diagrams illustrating a method for acquiring three-dimensional shape data used for calibration of the working robot system according to the first embodiment. [Figure 3] 4A to 4C are diagrams illustrating deviations in the rotation angle in the yaw direction of the scanner that occur in the working robot system according to the first embodiment. [Figure 4] FIG. 2 is a schematic diagram of a reference block according to the first embodiment. [Figure 5]10A and 10B are diagrams illustrating an extracted circular contour shape obtained when a reference block is scanned without misalignment between the Y axis of the control coordinate system and the Ys axis of the measurement coordinate system. [Figure 6] 10A and 10B are diagrams illustrating an extracted circular contour shape obtained when a reference block is scanned in a state where there is a misalignment between the Y axis of the control coordinate system and the Ys axis of the measurement coordinate system. [Figure 7] 10A and 10B are diagrams illustrating a relationship between the magnitude of a yaw rotation angle and an extracted circular contour shape according to the first embodiment. [Figure 8] 1 is a schematic diagram of a calibration device according to a first embodiment. [Figure 9] 4 is a flowchart illustrating the operation of the calibration device according to the first embodiment. [Figure 10] 5A to 5C are diagrams illustrating eccentricity used in calculating the amount of distortion of a circular contour shape according to the first embodiment. [Figure 11] 10A and 10B are diagrams illustrating a cross-sectional shape of a reference block according to a second embodiment. [Figure 12] FIG. 10 is a diagram illustrating the state of a scan signal in a first example of a reference block according to the second embodiment. [Figure 13] FIG. 10 is a diagram illustrating the state of a scan signal in a third example of a reference block according to the second embodiment. [Figure 14] FIG. 10 is a diagram illustrating the state of a scan signal in a comparative example of the reference block according to the second embodiment. [Figure 15] 10A and 10B are diagrams illustrating a cross-sectional shape of a modified example of the first example of the reference block according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] For clarity of explanation, the following description and drawings have been omitted and simplified as appropriate. Furthermore, each element shown in the drawings as a functional block performing various processes can be configured in hardware with a CPU (Central Processing Unit), memory, and other circuits, and in software with a program loaded into memory, etc. Therefore, those skilled in the art will understand that these functional blocks can be realized in various forms using only hardware, only software, or a combination thereof, and are not limited to any one of these. In addition, the same elements are designated by the same reference numerals in each drawing, and redundant explanations are omitted as necessary.

[0013] Furthermore, the above-described program includes a set of instructions (or software code) that, when loaded into a computer, causes the computer to perform one or more functions described in the embodiments. The program may be stored in a non-transitory computer-readable medium or a tangible storage medium. By way of example and not limitation, computer-readable media or tangible storage media include random-access memory (RAM), read-only memory (ROM), flash memory, solid-state drive (SSD) or other memory technology, CD-ROM, digital versatile disc (DVD), Blu-ray (registered trademark) disc or other optical disk storage, magnetic cassette, magnetic tape, magnetic disk storage or other magnetic storage device. The program may also be transmitted on a transitory computer-readable medium or communication medium. By way of example and not limitation, transitory computer-readable media or communication media include electrical, optical, acoustic, or other forms of propagated signals.

[0014] Embodiment 1 Hereinafter, embodiments of the present invention will be described with reference to the drawings. Fig. 1 is a schematic diagram of a working robot system 1 according to the first embodiment. As shown in Fig. 1, in the working robot system 1 according to the first embodiment, a work tool 20 is attached to a tool attachment part 11 provided at the tip of a robot arm 10. Also as shown in Fig. 1, the robot arm 10 is provided with a control part (for example, a robot controller 12).

[0015] Although the following description will be given using a working robot system as an application example, the present invention can also be applied to systems other than working robot systems, etc. For example, the present invention can be applied to sensors for machine tools including NC (Numerically Control) devices such as machining centers and multitasking machines.

[0016] The robot controller 12 operates the robot arm 10 based on work information data prepared in advance. In addition, if the work tool 20 has a sensor such as a three-dimensional sensor that acquires the three-dimensional shape of the workpiece, the robot controller 12 may transmit the three-dimensional shape measurement data of the workpiece acquired by the three-dimensional sensor to a host system.

[0017] In the work robot system 1, the work tool 20 is moved by the robot arm 10, and is operated at a position, angle, and speed suitable for the work to be performed on a workpiece placed on the workbench 40. Here, in the work robot system 1, tool attitude control information that instructs the attitude of the work tool 20 is generated within a work information data generation system (not shown) included in the host system, and is included in the work information data.

[0018] Here, various types of tools suitable for the work to be performed can be attached to work tool 20, such as welding, painting, drills, robotic hands, scanners, etc. In working robot system 1 according to the first embodiment, an example is described in which work tool 20 is equipped with both a welding tool and a scanner, but working robot system 1 also includes cases in which work tool 20 is equipped with only a scanner. Also, in working robot system 1 according to the first embodiment, an example is described in which a tool holder optimal for a welding tool that performs welding is applied as work tool 20, but the scope of application of working robot system 1 described in embodiment 1 is not limited to this.

[0019] In the working robot system 1 according to the first embodiment, the scanner mounting angle is calibrated, particularly when a scanner is attached alone as the work tool 20 or when a scanner is attached together with the work tool 20. Therefore, the working robot system 1 shown in FIG. 1 includes a calibration device 30. The calibration device 30 is included in the working robot system 1 so as to be able to communicate with the robot controller 12. The calibration device 30 calculates the amount of deviation in the scanner mounting angle, particularly the yaw rotation angle around the Z axis extending in the vertical direction. In the calibration process for calculating the deviation in the scanner's yaw rotation angle, the calibration device 30 sends operation commands for the robot arm 10 to the robot controller 12 and transmits and receives data to and from the scanner. Furthermore, in the calibration process in the working robot system 1, a reference block is used, and the deviation in the yaw rotation angle is calculated based on the amount of distortion of the circular contour shape obtained by scanning the reference block. The calibration process of the working robot system 1 using the calibration device 30 and the reference block is described in detail below.

[0020] FIG. 2 is a diagram illustrating a method for acquiring three-dimensional shape data used for calibrating the working robot system 1 according to the first embodiment. As shown in FIG. 2, in the working robot system 1 according to the first embodiment, a scanner 21 is attached to the tip of the tool mounting unit 11, and a reference block 50 is placed on the work table 40. The scanner 21 acquires shape data of the workpiece. One example of the scanner 21 is a laser scanner that acquires the unevenness of the target object as point cloud data. In the following description, the vertical direction from the tool mounting unit 11 toward the work table 40 is referred to as the Z axis, one of the axes perpendicular to the Z axis is referred to as the Y axis, and an axis perpendicular to both the Z axis and the Y axis is referred to as the X axis. In the following description, the direction in which the laser light transmitting unit and the laser light receiving unit of the scanner 21 are aligned is referred to as the X axis direction.

[0021] With reference block 50 placed on workbench 40, working robot system 1 emits a scan signal (e.g., laser light) from scanner 21 in the Z-axis direction, and scanner 21 receives the scan signal reflected from reference block 50, thereby acquiring point cloud data (hereinafter, this point cloud data will be referred to as three-dimensional shape data) that represents the three-dimensional shape of reference block 50. Working robot system 1 also acquires three-dimensional shape data that represents the overall shape of reference block 50 by repeating the scanning process while moving tool attachment part 11 at predetermined distance intervals in the Y-axis direction.

[0022] However, when scanner 21 is mounted, a yaw rotation angle around the Z axis (in other words, an angular deviation from the correct position in the Y axis direction) occurs. This yaw rotation angle will now be described with reference to FIG. 3. FIG. 3 is a diagram illustrating a deviation in the rotation angle in the yaw direction of scanner 21 that occurs in working robot system 1 according to the first embodiment. As shown in FIG. 3, in working robot system 1, the transmitter and receiver of scanner 21 are aligned, the X axis of the scanner (the X axis of the measurement coordinate system, hereinafter referred to as the Xs axis) defined in the direction of the longer side of scanner 21 coincides with the X axis of the control coordinate system of tool mounting unit 11, and the Y axis of the scanner (the Y axis of the measurement coordinate system, hereinafter referred to as the Ys axis) defined in the direction of the shorter side of scanner 21 coincides with the Y axis of the control coordinate system of tool mounting unit 11. This is set as the ideal mounting position of scanner 21. However, the actual mounting position may be deviated from this ideal position by a yaw rotation angle θy. In working robot system 1 including calibration device 30, the yaw rotation angle θy is calculated as the amount of deviation of the mounting position from the amount of distortion of the circular contour shape obtained using the reference block in the calibration process.

[0023] In other words, the yaw rotation angle θy is the amount of deviation between the first Y axis (e.g., Y axis) of the measurement coordinate system set in the three-dimensional sensor (e.g., scanner 21) and the second Y axis (e.g., Ys axis) of the control coordinate system of the robot arm 10 to which the three-dimensional sensor is attached.

[0024] Here, the reference block 50 will be described. Fig. 4 is a schematic diagram of the reference block 50 according to the first embodiment. The reference block 50 may have a recess or protrusion with a circular contour on its upper surface, the shape of which is scanned by the scanner 21, and the circular contour may be defined as the outer periphery contour of the reference block 50. In other words, the shape of the reference block shown in Fig. 4 is an example and is not intended to limit the shape of the reference block.

[0025] The reference block 50 illustrated in FIG. 4 is a cylindrical 3D block. A cylindrical through-hole is provided from the top surface of the cylindrical 3D block to the bottom surface. The top surface serves as the reference surface to be scanned by the scanner 21. This cylindrical through-hole serves as a recess provided in the reference surface of the cylindrical 3D block. The opening of this recess serves as a circular opening 51. The contour of the circular opening 51 serves as a circular contour portion 52.

[0026] Here, the relationship between the yaw rotation angle θy and the extracted circular contour shape will be described. FIG. 5 is a diagram illustrating the extracted circular contour shape obtained when a reference block is scanned with no misalignment between the Y axis of the control coordinate system and the Ys axis of the measurement coordinate system. FIG. 6 is a diagram illustrating the extracted circular contour shape obtained when a reference block is scanned with a misalignment between the Y axis of the control coordinate system and the Ys axis of the measurement coordinate system. Note that the scanner 21 is assumed to be a line scanner that outputs a laser line that scans the object along the Xs axis of the measurement coordinate system, and scans the entire object while shifting the laser line in a direction parallel to the Y axis of the control coordinate system using the robot arm 10.

[0027] As shown in Figure 5, when there is no misalignment between the Y axis of the control coordinate system and the Ys axis of the measurement coordinate system, that is, when the yaw rotation angle θy is 0°, the laser line of the scanner 21 is perpendicular to the Y axis of the control coordinate system, so the extracted circular contour shape accurately reflects the shape of the circular contour portion 52.

[0028] On the other hand, as shown in Figure 6, if there is a misalignment between the Y axis of the control coordinate system and the Ys axis of the measurement coordinate system, that is, if the yaw rotation angle θy is not 0°, the laser line of the scanner 21 will be deviated from the direction perpendicular to the Y axis of the control coordinate system, and the extracted circular contour shape will be an ellipse that is a distorted version of the shape of the circular contour portion 52.

[0029] In working robot system 1, the shape of circular contour portion 52 of reference block 50 is set to a predetermined specified shape. In working robot system 1, the shape of the portion corresponding to circular contour portion 52 is extracted as an extracted circular contour shape from the three-dimensional shape data obtained using scanner 21. Calibration device 30 then calculates the yaw rotation angle θy of scanner 21 from the amount of distortion of the extracted circular contour shape relative to the specified shape.

[0030] Next, the relationship between distortion of the extracted circular contour shape and the yaw rotation angle θy will be described. FIG. 7 is a diagram illustrating the relationship between the magnitude of the yaw rotation angle and the extracted circular contour shape according to the first embodiment. As shown in FIG. 7, the specified shape of the circular contour portion 52 provided on the reference block 50 is close to a perfect circle. When the yaw rotation angle θy is 0 degrees (i.e., there is no deviation), the extracted circular contour shape nearly matches the specified shape. On the other hand, when the scanner 21 is mounted at an angle, the extracted circular contour shape becomes elliptical, and as the yaw rotation angle θy increases, the elliptical shape becomes increasingly flattened.

[0031] The calibration device 30 calculates the flattening of this extracted circular contour shape (hereinafter referred to as the distortion amount), and calculates the yaw rotation angle θy using a formula or a table that defines the relationship between this distortion amount and the yaw rotation angle θy. The calibration device 30 will be described in more detail below.

[0032] Fig. 8 is a schematic diagram of the calibration device according to the first embodiment. In Fig. 8, the robot controller 12 is also shown to explain the operation of the calibration device 30.

[0033] The calibration device 30 includes a scan processing unit 31 that scans a reference block 50 having a circular contour portion 52 of a predetermined shape on a reference surface by moving a three-dimensional sensor (e.g., a scanner 21) in a Y-axis direction perpendicular to a Z-axis extending in the direction of irradiation of a scan signal from the three-dimensional sensor to acquire three-dimensional shape data of the reference surface; a circular contour extraction processing unit 33 that extracts the shape of the circular contour portion 52 on the reference surface from the three-dimensional shape data as an extracted circular contour shape; a distortion amount calculation processing unit 34 that calculates the amount of distortion of the extracted circular contour shape relative to a specified shape that is predetermined as the shape of the circular contour portion 52; and a rotation angle calculation processing unit 35 that calculates the yaw rotation angle θy of the three-dimensional sensor around the Z-axis based on the distortion amount.

[0034] The circular contour is the contour of the opening of a circular recess provided on the reference surface.

[0035] Calibration device 30 can be realized by dedicated hardware that executes each process, or by a calibration program that causes a computer having a calculation unit that executes the program and a storage unit such as a memory to execute each process. In this case, the calibration program is a calibration program that calculates a yaw rotation angle θy of a three-dimensional sensor (e.g., scanner 21) about a Z axis extending in the direction of scan signal irradiation from a three-dimensional sensor using a reference block 50 having a circular contour portion 52 whose shape is predetermined on a reference surface. The calibration program instructs the computer to execute the following steps: a scanning process (step S1) that scans reference block 50 while moving the three-dimensional sensor in a Y axis direction perpendicular to the Z axis to acquire three-dimensional shape data of the reference surface; a circular contour extraction process (step S2) that extracts the shape of circular contour portion 52 on the reference surface from the three-dimensional shape data as an extracted circular contour shape; a distortion amount calculation process (step S3) that calculates the amount of distortion of the extracted circular contour shape with respect to a predetermined shape that is a predetermined shape of circular contour portion 52; and a rotation angle calculation process (step S4) that calculates the yaw rotation angle θy based on the amount of distortion.

[0036] The present embodiment can also be regarded as a calibration method. The calibration method according to the first embodiment is a calibration method that uses a computer to calculate a yaw rotation angle θy of a three-dimensional sensor (e.g., scanner 21) around a Z axis extending in the direction of scan signal irradiation of the three-dimensional sensor using a reference block 50 having a circular contour portion 52 whose shape is predetermined on a reference surface, and causes the computer to perform a scanning process (step S1) in which the reference block is scanned while the three-dimensional sensor is moved in a Y axis direction perpendicular to the Z axis to acquire three-dimensional shape data of the reference surface, a circular contour extraction process (step S2) in which the shape of circular contour portion 52 provided on the reference surface is extracted as an extracted circular contour shape from the three-dimensional shape data, a distortion amount calculation process (step S3) in which the amount of distortion of the extracted circular contour shape with respect to a specified shape that is predetermined as the shape of circular contour portion 52 that is predetermined, and a rotation angle calculation process (step S4) in which the yaw rotation angle θy is calculated based on the amount of distortion.

[0037] As shown in FIG. 8, the calibration device 30 includes a scan processing unit 31, a storage unit 32, a circular contour extraction processing unit 33, a distortion amount calculation processing unit , a rotation angle calculation processing unit , and a display unit .

[0038] The scan processing unit 31 executes a scan process to acquire three-dimensional shape data of a reference surface by scanning a reference block 50 having a circular contour portion 52 whose shape is predetermined on the reference surface while moving the scanner 21 in a Y-axis direction perpendicular to a Z-axis extending in the direction of irradiation of a scan signal from the scanner 21. In the scan process, the scan processing unit 31 sends an instruction to the robot controller 12 to operate the robot arm 10, and also acquires point cloud data acquired by the scanner 21 and stores this point cloud data in the memory unit 32 as three-dimensional shape data.

[0039] The circular contour extraction processing unit 33 executes a circular contour extraction process to extract the shape of the circular contour portion 52 provided on the reference surface from the three-dimensional shape data stored in the storage unit 32 as an extracted circular contour shape.

[0040] The distortion amount calculation processor 34 executes a distortion amount calculation process to calculate the distortion amount of the extracted circular contour shape relative to a predetermined specified shape that is a predetermined shape of the circular contour portion. Fig. 8 shows an example in which the distortion amount calculation processor 34 includes data of the specified shape that has been acquired in advance as saved information.

[0041] Here, the larger the yaw rotation angle θy, the flatter the elliptical shape of the extracted circular contour shape becomes, and the distortion amount calculation processing unit calculates the eccentricity amount, which is the ratio between the radius of the extracted circular contour shape in the major axis direction and the midpoint in the major axis direction to the focus of the extracted circular contour shape, as the distortion amount.

[0042] The rotation angle calculation processor 35 executes a rotation angle calculation process to calculate the yaw rotation angle θy based on the distortion amount. More specifically, the rotation angle calculation processor derives the yaw rotation angle based on table information that predefines the relationship between the distortion amount and the yaw rotation angle θy, or a rotation angle calculation function that derives the yaw rotation angle using the distortion amount as a variable. The rotation angle calculation function is a function that is created in advance through prior verification work.

[0043] The display unit 36 ​​performs display processing to present the yaw rotation angle θy to the user as the required correction amount. Note that the display unit 36 ​​is one of the ways in which the calculated yaw rotation angle θy is used, and how the yaw rotation angle θy is used can be set arbitrarily depending on the specifications of the work robot system 1. For example, in a first use method, the operator adjusts the attachment state of the scanner 21 to the tool mount 11 based on the yaw rotation angle θy displayed on the display unit 36. In a second use method, the attachment state of the scanner 21 to the tool mount 11 is adjusted by a manipulator based on the yaw rotation angle θy displayed on the display unit 36. In a third use method, correction is performed by applying the yaw rotation angle θy as an offset amount to the control coordinate system of the robot arm 10.

[0044] Next, a detailed description will be given of the calibration process using the calibration device 30 according to the first embodiment. Fig. 9 is a flowchart illustrating the operation of the calibration device 30 according to the first embodiment.

[0045] As shown in FIG. 9, when the calibration device 30 according to the first embodiment starts the calibration process, it first scans the reference block 50 while moving the scanner 21 in the Y-axis direction perpendicular to the Z-axis, and performs a scanning process to obtain three-dimensional shape data of the reference surface of the reference block 50 (step S1).

[0046] Next, the calibration device 30 executes a circular contour extraction process to extract the shape of the circular contour portion 52 provided on the reference plane from the three-dimensional shape data acquired in step S1 as an extracted circular contour shape (step S2). After that, the calibration device 30 executes a distortion amount calculation process to calculate the amount of distortion of the extracted circular contour shape with respect to a specified shape that is preset as the shape of the circular contour portion 52 (step S3). Then, the calibration device 30 executes a rotation angle calculation process to calculate the yaw rotation angle θy based on the amount of distortion (step S4).

[0047] Here, an example of the distortion amount will be described with reference to Fig. 10. In the calibration device 30, the eccentricity amount is used as the distortion amount. Fig. 10 is a diagram for explaining the eccentricity used in calculating the distortion amount of a circular contour shape according to the first embodiment.

[0048] As shown in FIG. 10, the diameter of an ellipse in the direction in which the major axis Ax extends (the horizontal direction in FIG. 10) is different from the diameter in the direction in which the minor axis Ay extends (the vertical direction in FIG. 19). The intersection of the major axis Ax and the minor axis Ay is the center point C of the ellipse. In the example shown in FIG. 10, the center point C is the midpoint of the major axis Ax. If the point where the major axis Ax intersects with the circumference of the ellipse is defined as vertex V, the distance between the center point C and the vertex V is defined as a. Foci F1 and F2 can be defined on the major axis Ax. If a point on the circumference of the ellipse is defined as point P, the foci F1 and F2 are points where the sum of the distance between focus F1 and point P and the distance between focus F2 and point P is always constant. The distance between the center point C and focus F1 is defined as b. In such an ellipse, the eccentricity e is calculated by dividing the distance b by the distance a.

[0049] In the distortion calculation process in step S3, this eccentricity e is calculated as the distortion amount. However, since the distortion amount of an ellipse can be expressed using various indices other than eccentricity, the indices that can be used to calculate the distortion amount are not limited to eccentricity. Since eccentricity e can be calculated by division alone, it has the advantage of requiring less calculation.

[0050] The magnitude of this eccentricity e has a certain correlation with the yaw rotation angle θy. Therefore, the calibration device 30 creates in advance table information that defines the relationship between the amount of distortion (for example, eccentricity e) and the yaw rotation angle θy, or a rotation angle calculation function that derives the yaw rotation angle using the amount of distortion as a variable, and derives the yaw rotation angle θy using the table information or the rotation angle calculation function.

[0051] As described above, by using the calibration device 30 according to the first embodiment, it is possible to calculate the amount of deviation of the rotation angle (yaw rotation angle θy) around the Z axis between the measurement coordinate system set for the scanner 21 and the control coordinate system set for the robot arm 10. Then, by adjusting the mounting state of the scanner 21 based on the magnitude of this yaw rotation angle θy, it becomes possible to perform calibration that eliminates the deviation between the measurement coordinate system and the control coordinate system and eliminates distortion in the three-dimensional shape data acquired by the scanner 21. Embodiment 2 In the second embodiment, a detailed description will be given of the reference block 50. An example of the appearance of the reference block 50 is shown in FIG.

[0052] In the example shown in FIG. 4 , the reference block 50 is a three-dimensional block having a bottom surface that contacts the workbench and a top surface that faces the bottom surface and is parallel to the bottom surface. The top surface includes a recess with a circular contour. The recess has a cylindrical shape with a constant depth from the top surface to the bottom surface. The corners of the contour of the top surface of the recess are configured so that two surfaces meet at an acute or obtuse angle. The corners of the contour of the top surface of the recess are defined by tapered ends with a reduced diameter so that the diameter is smaller than the diameter of the cylindrical shape. The corners of the contour of the top surface of the recess are defined by tapered ends with an increased diameter so that the diameter is larger than the diameter of the cylindrical shape. The recess is a through-hole that penetrates from the top surface to the bottom surface. The top surface of the reference block 50 serves as the reference surface whose shape is acquired by the scanner 21.

[0053] 4, the recess is in the form of a through hole penetrating from the top surface side to the bottom surface side, but the recess may be a depression having a bottom. When the recess is provided as a depression, the bottom of the depression is preferably flat.

[0054] When a device using laser light as a scanning signal is used as the scanner 21, diffused reflection of light occurs at right-angle corners in the reference block 50, which can cause noise to be recorded in the point cloud data. Therefore, it is preferable to provide a tapered surface on the circular contour portion 52 of the reference block 50, from which the extracted circular contour shape is extracted. Therefore, FIG. 11 shows first to third examples of reference blocks 50 with tapered surfaces and a comparative example of a reference block 50 without a tapered surface. FIG. 11 is a diagram illustrating the cross-sectional shape of the reference block 50 according to the second embodiment. FIG. 11 is a cross-section of the reference block 50 taken along line IX-IX in FIG. 4.

[0055] 11, the contour of the opening on the top surface of the recess has a tapered surface with a reduced diameter so that the diameter is smaller than the diameter of the cylindrical shape that will become the recess. In the second example, the contour of the opening on the top surface of the recess has a tapered surface with an expanded diameter so that the diameter is larger than the diameter of the cylindrical shape that will become the recess. In the comparative example, the circular contour portion 52 forms a right angle with the top surface and the cylindrical shape.

[0056] The reflection of laser light (e.g., scan signal) near the circular contour portion 52 in the first example, second example, and comparative example will be described with reference to Figs. 12 to 14. Fig. 12 is a diagram illustrating the state of the scan signal in the first example of the reference block 50 according to the second embodiment. Fig. 13 is a diagram illustrating the state of the scan signal in the second example of the reference block 50 according to the second embodiment. Fig. 14 is a diagram illustrating the state of the scan signal in the comparative example of the reference block 50 according to the second embodiment.

[0057] 12 to 14, scanner 21 has a transmitter 22 and a light receiver 23. Scanner 21 receives reflected light of laser light emitted from transmitter 22 with light receiver 23, and outputs the distance to the point of reflection as point cloud data.

[0058] 12, in the first example, the circular contour portion 52 exists at the tip of a sharply pointed shape. Therefore, diffuse reflection of the laser light is suppressed at the tip portion that forms the circular contour portion 52, and therefore noise caused by diffuse reflection of the laser light is suppressed.

[0059] 13, in the second example, the two surfaces that meet at the corner where the circular outline portion 52 is set form an obtuse angle. Therefore, even if diffuse reflection of the laser light occurs, it does not reach the light receiving portion 23, thereby suppressing noise.

[0060] As shown in Figure 14, in the comparative example, the corners forming the circular contour portion 52 are right angles, so the laser light that hits the periphery of the circular contour portion 52 is diffusely reflected, and the diffusely reflected light is likely to reach the light receiving unit 23, resulting in a lot of noise being included in the point cloud data.

[0061] Thus, from the viewpoint of noise suppression, the shape of the reference block according to the first example is preferable. This has been confirmed by verification as a favorable tendency from the viewpoint of noise suppression.

[0062] To improve the accuracy of the extracted circular contour shape, it is preferable to make the size of circular contour portion 52 as large as possible so that it is included in the scannable range of scanner 21. Furthermore, if circular contour portion 52 is set closer to the inner circle of reference block 50 than to the outer periphery, the efficiency of reflection of laser light to light receiving portion 23 of scanner 21 is relatively increased, thereby improving the extraction accuracy of the extracted circular contour shape.

[0063] Furthermore, in the first and second examples, the shape of the tapered surface may be either flat or curved. Therefore, FIG. 15 shows a modified example of the first example in which the tapered surface is curved. FIG. 15 is a diagram illustrating the cross-sectional shape of a modified example of the first example of the reference block according to the second embodiment. FIG. 15 is a cross-section of the reference block 50 taken along line IX-IX in FIG. 4. In the modified example of the first example shown in FIG. 15, the tapered surface of the first example is curved into a concave shape. By using a curved tapered surface in this way, the angle of the circular contour portion 52 can be made more acute, which has been verified to be preferable from the standpoint of noise suppression.

[0064] The material of the reference block 50 is not particularly limited, but a material with a low thermal expansion coefficient is preferable because it can adapt to changes in environmental temperature. An example of such a material is a ceramic material. Furthermore, for practical purposes, a material that combines a low thermal expansion coefficient with high workability is more preferable, such as a metal or an alloy. Examples of metals include iron and aluminum. Examples of alloys include carbon-containing metals such as SUS (Steel Use Stainless) and carbon steel.

[0065] As explained above, the circular contour 52 of the reference block 50 can suppress diffuse reflection of laser light by ensuring that the two surfaces that make up the corners of the circular contour 52 meet at an acute or obtuse angle. Preventing diffuse reflection of laser light in this way prevents noise from distorting the shape of the circular contour 52 represented in the three-dimensional shape data. Suppressing noise contained in the three-dimensional shape data in this way can improve the accuracy of the yaw rotation angle θy calculated based on the extracted circular contour shape.

[0066] The present invention is not limited to the above-described embodiments, and can be modified as appropriate without departing from the spirit of the present invention. For example, a person skilled in the art can easily conceive of implementing the present invention by appropriately combining the features described in each embodiment.

[0067] Finally, the embodiments of the present invention will be summarized with reference to the drawings etc. As shown in Figs. 1 to 15, the embodiments of the present invention are described below.

[0068] (Appendix 1) a scan processing unit (31) that scans a reference block (50) having a circular contour portion (52) whose shape is predetermined on a reference surface while moving the three-dimensional sensor (21) in a Y-axis direction perpendicular to a Z-axis extending in a scan signal irradiation direction of the three-dimensional sensor (21), thereby acquiring three-dimensional shape data of the reference surface; a circular contour extraction processing unit (33) that extracts the shape of a circular contour portion (52) provided on the reference surface from the three-dimensional shape data as an extracted circular contour shape; a distortion amount calculation processing unit (34) that calculates a distortion amount of the extracted circular contour shape relative to a predetermined specified shape that is a predetermined shape of the circular contour portion (52); a rotation angle calculation processing unit (35) that calculates a yaw rotation angle (θy) of the three-dimensional sensor (21) around the Z axis based on the distortion amount; A calibration device comprising:

[0069] (Appendix 2) 2. The calibration program according to claim 1, wherein the circular contour portion (52) is a contour of an opening of a circular recess provided on the reference surface.

[0070] (Appendix 3) The extracted circular contour shape becomes a flattened ellipse as the yaw rotation angle (θy) increases, The calibration program according to claim 1 or 2, wherein the distortion amount calculation processing unit (34) calculates the amount of eccentricity, which is the ratio of the radius of the extracted circular contour shape in the major axis direction and the midpoint of the major axis direction to the focus of the extracted circular contour shape, as the distortion amount.

[0071] (Appendix 4) The calibration program according to any one of appendices 1 to 3, wherein the rotation angle calculation processing unit (35) derives the yaw rotation angle (θy) based on table information that predefines the relationship between the distortion amount and the yaw rotation angle (θy), or based on a rotation angle calculation function that derives the yaw rotation angle (θy) using the distortion amount as a variable.

[0072] (Appendix 5) The calibration program according to any one of appendices 1 to 4, wherein the yaw rotation angle (θy) is the deviation between a first Y-axis of a measurement coordinate system set in the three-dimensional sensor (21) and a second Y-axis of a control coordinate system of a robot arm to which the three-dimensional sensor (21) is attached.

[0073] (Appendix 6) 6. The calibration program according to any one of appendices 1 to 5, further comprising a display process for presenting the yaw rotation angle (θy) to a user as a required correction amount.

[0074] (Appendix 7) A calibration method for calculating a yaw rotation angle (θy) of a three-dimensional sensor (21) around a Z axis extending in a scan signal irradiation direction of the three-dimensional sensor (21) using a reference block (50) having a circular contour portion (52) whose shape is predetermined on a reference surface, using a computer, the method comprising: a scanning process (S1) of scanning the reference block (50) while moving the three-dimensional sensor (21) in a Y-axis direction perpendicular to the Z-axis, and acquiring three-dimensional shape data of the reference surface; a circular contour extraction process (S2) for extracting the shape of the circular contour portion (52) provided on the reference surface from the three-dimensional shape data as an extracted circular contour shape; a distortion amount calculation process (S3) for calculating a distortion amount of the extracted circular contour shape relative to a predetermined shape that is a predetermined shape of the circular contour portion (52); a rotation angle calculation process (S4) for calculating the yaw rotation angle (θy) based on the distortion amount; A calibration method in which the computer performs the following.

[0075] (Appendix 8) A calibration program for calculating a yaw rotation angle (θy) of a three-dimensional sensor (21) around a Z axis extending in a scan signal irradiation direction of the three-dimensional sensor (21) using a reference block (50) having a circular contour portion (52) whose shape is predetermined on a reference surface, the program comprising: a scanning process (S1) of scanning the reference block (50) while moving the three-dimensional sensor (21) in a Y-axis direction perpendicular to the Z-axis, and acquiring three-dimensional shape data of the reference surface; a circular contour extraction process (S2) for extracting the shape of the circular contour portion (52) provided on the reference surface from the three-dimensional shape data as an extracted circular contour shape; a distortion amount calculation process (S3) for calculating a distortion amount of the extracted circular contour shape relative to a predetermined shape that is a predetermined shape of the circular contour portion (52); a rotation angle calculation process (S4) for calculating the yaw rotation angle (θy) based on the distortion amount; A calibration program that causes a computer to execute the following.

[0076] (Appendix 9) A three-dimensional block having a bottom surface that contacts a work table and a top surface that faces the bottom surface and is parallel to the bottom surface, The top surface is provided with a recess having a circular contour, The recess has a cylindrical shape with a certain depth from the top surface to the bottom surface, A reference block (50) in which a corner constituting the outline of the opening on the top surface side of the recess is configured so that two surfaces meet to form an acute angle or an obtuse angle.

[0077] (Appendix 10) A reference block (50) as described in Appendix 9, wherein the corners that form the outline of the opening on the top surface side of the recess are defined by the end of a tapered shape with a reduced diameter so that the diameter is smaller than the diameter of the cylindrical shape.

[0078] (Appendix 11) A reference block (50) as described in Appendix 9, wherein the corners that form the outline of the opening on the top surface side of the recess are defined by the end of a tapered portion of an expanded diameter shape so that the diameter is larger than the diameter of the cylindrical shape.

[0079] (Appendix 12) 11. The reference block (50) according to claim 9 or 10, wherein the recess is a through-hole that penetrates from the top surface to the bottom surface. [Explanation of symbols]

[0080] 1. Working robot system 10 Robotic Arm 11 Tool mounting part 12 Robot Controller 20 Work Tools 21 Scanner 22 Transmitter 23 Light receiving part 30 Calibration Device 31 Scan processing section 32 Storage section 33 Circular contour extraction processing unit 34 Distortion amount calculation processing unit 35 Rotation angle calculation processing unit 36 Display section 40 Workbench 50 Reference Blocks 51 Circular opening 52 Circular contour section

Claims

1. a scanning processing unit that scans a reference block having a circular contour portion with a predetermined shape on a reference surface while moving the three-dimensional sensor in a Y-axis direction perpendicular to a Z-axis extending in a direction in which the three-dimensional sensor emits a scan signal, thereby acquiring three-dimensional shape data of the reference surface; a circular contour extraction processing unit that extracts the shape of a circular contour portion provided on the reference plane from the three-dimensional shape data as an extracted circular contour shape; a distortion amount calculation processing unit that calculates a distortion amount of the extracted circular contour shape relative to a predetermined specified shape that is a predetermined shape of the circular contour portion; a rotation angle calculation processing unit that calculates a yaw rotation angle of the three-dimensional sensor around the Z axis based on the distortion amount; A calibration device comprising:

2. 2. The calibration device according to claim 1, wherein the circular contour portion is a contour of an opening of a circular recess provided on the reference surface.

3. The extracted circular contour shape becomes a flattened elliptical shape as the yaw rotation angle increases, 2. The calibration device according to claim 1, wherein the distortion amount calculation processing unit calculates, as the distortion amount, an eccentricity amount that is a ratio between a radius of the extracted circular contour shape in a major axis direction and a midpoint of the major axis direction to a focus of the extracted circular contour shape.

4. 2. The calibration device according to claim 1, wherein the rotation angle calculation processing unit derives the yaw rotation angle based on table information that predefines a relationship between the distortion amount and the yaw rotation angle, or based on a rotation angle calculation function that derives the yaw rotation angle using the distortion amount as a variable.

5. 2. The calibration device according to claim 1, wherein the yaw rotation angle is a deviation between a first Y-axis of a measurement coordinate system set in the three-dimensional sensor and a second Y-axis of a control coordinate system of a robot arm to which the three-dimensional sensor is attached.

6. The calibration device according to claim 1 , further comprising a display unit that displays the yaw rotation angle as a required correction amount to a user.

7. A calibration method using a computer to calculate a yaw rotation angle of a three-dimensional sensor around a Z axis extending in a scan signal irradiation direction of the three-dimensional sensor, using a reference block having a circular contour portion with a predetermined shape on a reference surface, the method comprising: a scanning process of scanning the reference block while moving the three-dimensional sensor in a Y-axis direction perpendicular to the Z-axis, and acquiring three-dimensional shape data of the reference surface; a circular contour extraction process for extracting the shape of the circular contour portion provided on the reference surface from the three-dimensional shape data as an extracted circular contour shape; a distortion amount calculation process for calculating a distortion amount of the extracted circular contour shape relative to a predetermined specified shape that is a predetermined shape of the circular contour portion; a rotation angle calculation process for calculating the yaw rotation angle based on the distortion amount; A calibration method in which the computer performs the following.

8. A calibration program for calculating a yaw rotation angle of a three-dimensional sensor around a Z axis extending in a scan signal irradiation direction of the three-dimensional sensor using a reference block having a circular contour portion with a predetermined shape on a reference surface, a scanning process of scanning the reference block while moving the three-dimensional sensor in a Y-axis direction perpendicular to the Z-axis, and acquiring three-dimensional shape data of the reference surface; a circular contour extraction process for extracting the shape of the circular contour portion provided on the reference surface from the three-dimensional shape data as an extracted circular contour shape; a distortion amount calculation process for calculating a distortion amount of the extracted circular contour shape relative to a predetermined specified shape that is a predetermined shape of the circular contour portion; a rotation angle calculation process for calculating the yaw rotation angle based on the distortion amount; A calibration program that causes a computer to execute the following.

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