JP2017124468A - Method of controlling robot, method of manufacturing component, robot device, program, and recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately obtain a positional deviation of an end effector to a tip end link of a robot arm, without stopping the action of the robot arm.SOLUTION: A robot arm is actuated to start the movement of an end effector to an imaging device which picks up an image of an object in an imaging range (S3). While the end effector passes through the imaging range, in a rotary state in which a tip end link is rotated about a rotary shaft, the imaging device is made to pick up the image of the end effector(S4, S5, and S6). On the basis of a track of a center axis of the end effector in a picked up image, a positional deviation of a center axis of the end effector to the rotary shaft of the tip end link is calculated (S7).SELECTED DRAWING: Figure 4

Description

  The present invention relates to a technique for calculating a position shift of an end effector with respect to a distal end link to which an end effector is attached.

  The multi-joint robot arm is configured by connecting a plurality of links so as to swing or rotate at the joint. In particular, the tip link located at the tip of the robot arm is connected to another link so as to rotate at the joint. An end effector such as a robot hand is detachably attached to the tip link. As a result, the end effector can be exchanged according to the work content.

  When the end effector is replaced, the center axis of the end effector may be displaced with respect to the tip axis of the robot arm, that is, the rotation axis of the tip link, and the end effector may be attached to the robot arm. Therefore, when the parts are assembled with high accuracy using the robot, it is necessary to calibrate the position shift of the center axis of the end effector with respect to the tip axis of the robot arm, that is, the rotation axis of the tip link. That is, it is necessary to obtain the position shift of the center axis of the end effector with respect to the tip axis and reattach the end effector so as to cancel the position shift or correct the position command value (that is, the trajectory) of the robot arm.

  Conventionally, there has been proposed a method of causing a camera to image a mark of a measurement jig gripped by a robot hand as an end effector and measuring a positional deviation of the robot hand from a captured image (see Patent Document 1). In the method of Patent Document 1, the robot hand is temporarily stopped in front of the camera and imaging is performed by the camera. At this time, the mark of the measurement jig held by the robot hand is imaged by the camera at two positions where the rotation angle of the tip axis of the robot arm is 180 ° different, and the displacement of the robot hand is measured from the captured image. ing.

JP-A-10-340112

  However, in the method of Patent Document 1, it takes time to measure the positional deviation because the measurement jig is held by the robot hand and stopped in front of the camera for imaging. Further, since the measured positional deviation is greatly affected by the rotation accuracy of the robot hand, there is a problem that an error occurs in the measurement result. That is, even if the robot hand is intended to be rotated by 180 ° around the tip axis, it may actually deviate from 180 °, and an error in the rotation angle causes a decrease in measurement accuracy of the positional deviation.

  Accordingly, an object of the present invention is to obtain a position shift of the end effector with respect to the tip link of the robot arm with high accuracy without stopping the operation of the robot arm.

  The present invention relates to a robot control method in which a control unit controls an operation of a robot arm having a tip link to which an end effector is attached, and the control unit operates the robot arm so that a subject within an imaging range is obtained. A moving state in which the end effector is moved with respect to an image pickup apparatus that picks up an image, and a rotation state in which the control unit rotates the tip link about a rotation axis while the end effector passes through the image pickup range. The imaging step of causing the imaging device to image the end effector, and the control unit, based on the locus of the central axis of the end effector in the captured image obtained in the imaging step, the rotation axis of the tip link Misalignment calculating step of calculating the misalignment of the center axis of the end effector with respect to.

  According to the present invention, the position shift of the end effector with respect to the tip link of the robot arm can be obtained with high accuracy without stopping the operation of the robot arm.

It is a perspective view which shows the robot apparatus which concerns on embodiment. (A) is a schematic diagram which shows the front-end | tip part of the robot in embodiment. (B) is the top view which looked at the robot hand from the bearing surface side of the robot hand in embodiment. It is a block diagram which shows the structure of the control system of the robot apparatus which concerns on embodiment. It is a flowchart which shows the manufacturing method of the components which concern on embodiment. (A) is a schematic diagram which shows an example of the captured image which the movement locus | trajectory of the mark reflected in embodiment. (B) is a figure for demonstrating the position shift of the center axis | shaft of the robot hand with respect to the rotating shaft of a front end link in embodiment. It is a schematic diagram which shows another example of the captured image in which the movement locus | trajectory of the mark was reflected in embodiment. It is a schematic diagram which shows another example of the captured image which the movement locus | trajectory of the mark reflected in embodiment.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. FIG. 1 is a perspective view illustrating a robot apparatus according to an embodiment. The robot apparatus 100 includes a robot 200, a control device 400 that controls the operation of the robot 200, and a teaching pendant 600 as a teaching unit that teaches the operation of the robot 200 by a user operation. The robot apparatus 100 further includes a camera 500 serving as an imaging apparatus and an image processing apparatus 300 that processes an image acquired by the camera 500.

  The robot 200 and the control device 400 are connected by wiring such as signal lines. The camera 500 and the image processing apparatus 300 are connected by wiring such as signal lines. The control device 400 and the image processing device 300 are connected by wiring such as signal lines. The control device 400 and the teaching pendant 600 are connected by wiring such as signal lines. In addition, although communication of these apparatuses is performed by wire, you may be comprised so that it may be performed wirelessly.

  The robot 200 includes a vertical articulated robot arm 201 and a robot hand 202 as an end effector attached to the tip of the robot arm 201. A force sensor may be arranged between the tip of the robot arm 201 and the robot hand 202. In this case, the robot hand 202 is attached to the tip of the robot arm 201 via a force sensor.

  In the robot arm 201, a base portion (base end link) 210 fixed to the pedestal 150 and a plurality of links 211 to 216 that transmit displacement and force are connected to be able to swing (turn) or rotate at joints J1 to J6. Has been. In the present embodiment, the robot arm 201 is composed of six-axis joints J1 to J6, which are three axes that swing and three axes that rotate. Here, the swinging joint is called a swinging part, and the rotating joint is called a rotating part. The robot arm 201 includes six joints J1 to J6. The joints J1, J4, and J6 are rotating parts, and the joints J2, J3, and J5 are swinging parts.

  In the present embodiment, the link on the opposite side to the base portion (fixed end) 210, that is, the link (tip link, free end) 216 that is the tip of the robot arm 201 has a rotational axis (tip shaft) with respect to the link 215. ) It is configured to be rotatable around C1. That is, the joint J6 is a rotating part.

  The robot arm 201 is provided for each of the joints J1 to J6, and has a plurality (six) of joint drive devices (not shown) that drive the joints J1 to J6, respectively. Each joint driving device includes an electric motor (not shown), a speed reducer, a control board, and the like. The control board (joint control unit) controls the joint angle based on the input joint command value (angle command value). That is, the control board controls the rotation of the electric motor so that the joint angle approaches the joint command value.

  FIG. 2A is a schematic diagram illustrating the tip of the robot in the embodiment. FIG. 2B is a plan view of the robot hand viewed from the seating surface side of the robot hand in the embodiment.

  The robot hand 202 includes a base portion 220 and a plurality (three) of fingers 221 supported on the seating surface side of the base portion 220 so as to be opened and closed.

  The plurality of fingers 221 are driven by a driving device (not shown) so as to approach or separate from the central axis C2. An operation in which the plurality of fingers 221 move in the direction approaching the central axis C2 is a closing operation, and an operation in which the plurality of fingers 221 move in a direction away from the central axis C2 is an opening operation. The workpiece W1 that is the first workpiece can be gripped by closing the plurality of fingers 221, and the workpiece W1 can be gripped and released by opening the plurality of fingers 221.

  The robot hand 202 uses a plurality of fingers 221 to grip the work W1, thereby assembling the work (fitting part) W1 as the first work to the work (fitting part) W2 as the second work. Attached work can be performed. By this assembling operation, an assembly part composed of the workpiece W1 and the workpiece W2 is manufactured.

  The robot hand 202 can be attached to and detached from the link 216. Specifically, as shown in FIG. 2A, a holding mechanism 217 is provided at the tip of the link 216, and the robot hand 202 (base portion 220) is held by the holding mechanism 217, thereby the link 216. A robot hand 202 is attached to the robot. Therefore, an end effector suitable for the work content can be attached to the link 216. In this embodiment, it is assumed that the robot hand 202 is attached to the link 216 in order to perform assembly work.

  As shown in FIG. 2B, a mark MK is formed at the seating surface center of the base portion 220 of the robot hand 202 (a point intersecting the central axis C2 on the seating surface). The mark MK may be anything as long as the center position of the robot hand 202 can be identified. For example, various marks such as holes, protrusions, seals, reflecting materials, and light emitting members can be used. The shape of the mark MK may be anything as long as the center position of the robot hand 202 can be identified. For example, various shapes such as a circular shape and a cross shape can be used. The color of the mark MK is preferably a color that can be distinguished from other members. In the present embodiment, the mark MK is configured by coloring a circular recess hole in a color different from that of other members such as the fingers 221.

  As shown in FIG. 1, the camera 500 includes an image sensor 501 such as a charge coupled device (CCD) image sensor or a complementary metal oxide semiconductor (CMOS) image sensor. The camera 500 is fixed to the gantry 150 so as not to move with respect to the gantry 150 (the base portion 210 of the robot arm 201). The camera 500 captures an image of a subject within an imaging range (within an angle of view). In this embodiment, the robot hand 202 (that is, the mark MK) is the subject.

  Here, a plane parallel to the imaging surface of the camera 500 (sensor surface of the imaging sensor 501) is defined as an XY plane, and a direction perpendicular to the XY plane is defined as a Z-axis direction.

  FIG. 3 is a block diagram illustrating a configuration of a control system of the robot apparatus according to the embodiment. The image processing apparatus 300 and the control apparatus 400 are configured by a computer. That is, in this embodiment, each device is controlled by being distributed by a plurality of computers. Specifically, the image processing device 300 controls the imaging timing, shutter speed, and the like of the camera 500, and the control device 400 controls the operations of the robot arm 201 and the robot hand 202. These image processing apparatus 300 and control apparatus 400 constitute a control system 800.

  The image processing apparatus 300 includes a CPU (Central Processing Unit) 301. The image processing apparatus 300 includes a ROM (Read Only Memory) 302, a RAM (Random Access Memory) 303, and an HDD (Hard Disk Drive) 304 as storage units. The image processing apparatus 300 includes a recording disk drive 305 and interfaces 311 and 312. A ROM 302, a RAM 303, an HDD 304, a recording disk drive 305, and interfaces 311 and 312 are connected to the CPU 301 via a bus.

  The control device 400 includes a CPU 401. The control device 400 includes a ROM 402, a RAM 403, and an HDD 404 as storage units. In addition, the control device 400 includes interfaces 411 to 414. A ROM 402, RAM 403, HDD 404, and interfaces 411 to 414 are connected to the CPU 401 via a bus.

  The ROMs 302 and 402 store basic programs for operating the computer. The RAMs 303 and 403 are storage devices that temporarily store various data such as arithmetic processing results of the CPUs 301 and 401.

  The HDDs 304 and 404 are storage devices that store arithmetic processing results of the CPUs 301 and 401, various data acquired from the outside, and the like, and record programs 320 and 420 for causing the CPUs 301 and 401 to perform arithmetic processing described later. Is. The CPUs 301 and 401 execute the steps of the robot control method based on the programs 320 and 420 recorded (stored) in the HDDs 304 and 404. That is, in the present embodiment, the control unit 801 is configured by a plurality of CPUs 301 and 401 that execute the programs 320 and 420, respectively.

  The recording disk drive 305 can read various data and programs recorded on the recording disk 321.

  The camera 500 is connected to the interface 312. The captured image generated by the imaging of the camera 500 is output to the CPU 301 via the interface 312 and the bus. The CPU 301 can perform image processing on this captured image.

  The teaching pendant (TP) 600 is connected to the interface 412. The teaching pendant 600 designates teaching points for teaching the robot arm 201 by a user input operation. The teaching point data is output to the HDD 404 through the interface 412 and the bus.

  The HDD 404 can store teaching point data designated by the teaching pendant 600. The CPU 401 can read teaching point data set (stored) in the HDD 404. The HDD 404 stores a robot program in which an interpolation method between teaching points is specified.

  The robot arm 201 is connected to the interface 413. The robot hand 202 is connected to the interface 414. The CPU 401 outputs joint command value data to the robot arm 201 via the interface 413 to control the operation of each joint of the robot arm 201.

  Further, the CPU 401 controls the operation of the robot hand 202 by outputting drive command value data to the robot hand 202 via the interface 414.

  In this embodiment, the case where the computer-readable recording medium is the HDD 304 (404) and the program 320 (420) is stored in the HDD 304 (404) is described, but the present invention is not limited to this. The program 320 (420) may be recorded on any recording medium as long as it is a computer-readable recording medium. For example, as a recording medium for supplying the program 320 (420), a recording disk 321 shown in FIG. 3, an external storage device (not shown), or the like may be used. As a specific example, a flexible disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a CD-R, a magnetic tape, a non-volatile memory such as a USB memory, a ROM, or the like can be used as a recording medium.

  Here, a tool center point (TCP) is set at the tip of the robot arm 201, that is, the robot hand 202. TCP has three parameters (x, y, z) representing a position and three parameters (Rx, Ry, Rz) representing a posture, that is, six parameters (x, y, z, Rx, Ry, Rz). It can be regarded as one point on the task space. That is, the task space is a space defined by these six coordinate axes. A teaching point can be designated by this TCP.

  In addition, the teaching point can be specified by a joint angle (configuration). In this embodiment, since the robot arm 201 has six joints, the teaching point is represented by a configuration (θ1, θ2, θ3, θ4, θ5, θ6) indicating six parameters representing the joint angle, and the joint space. Above, it can be regarded as one point. That is, the joint space is a space defined by these six coordinate axes.

  In the present embodiment, the teaching point is specified in a task space or a joint space. The CPU 401 generates route (interpolation route) data of the robot arm 201 that interpolates between teaching points according to the interpolation method specified by the robot program. Here, as interpolation methods for interpolating between teaching points, there are various methods such as linear interpolation, circular interpolation, joint interpolation, Spline interpolation, B-Spline interpolation, and Bezier curve. The path data is a TCP trajectory of the robot arm 201 in the task space or a configuration trajectory of the robot arm 201 in the joint space.

  Then, the CPU 401 calculates trajectory data that defines the operation of the robot arm 201. The trajectory data of the robot arm 201 represents route data using time as a parameter. In this embodiment, it is a set of TCP position command values or configuration joint command values for each time (for example, every 1 ms). The position command value is represented by six parameters (x, y, z, Rx, Ry, Rz), and the joint command value is represented by six parameters (θ1, θ2, θ3, θ4, θ5, θ6). .

  When the trajectory data is a position command value, the CPU 401 finally converts the position command value into a joint command value indicating the joint angle of each joint J1 to J6 based on inverse kinematics. The operation of the robot arm 201 is controlled by outputting the joint command value to the control board of the joint driving device of each joint J1 to J6. When the trajectory data is a joint command value, the CPU 401 controls the operation of the robot arm 201 by outputting the joint command value to the control board of the joint driving device of each joint J1 to J6.

  As described above, the CPU 401 controls the position of the robot arm 201 using the trajectory data including the position command value or the joint command value.

  Next, a control method (manufacturing method of assembly parts) of the control unit 801 will be described. FIG. 4 is a flowchart illustrating a method for manufacturing a component according to the embodiment.

  In this embodiment, after the robot hand 202 is replaced, the robot 200 (robot hand 202) is caused to repeatedly perform the same operation. However, the central axis C2 of the robot hand 202 is different from the rotation axis C1 of the link 216. It may be mounted out of position. For this reason, the positional deviation of the central axis C2 of the robot hand 202 with respect to the rotation axis C1 of the link 216 is calculated at the time of the first work. Here, it is assumed that nothing is held by the robot hand 202 so that the camera 500 can image the mark MK of the robot hand 202. The robot hand 202 is attached to the link 216 in a state where the rotation axis C1 of the link 216 and the center axis C2 of the robot hand 202 are parallel.

  First, the CPU 401 inputs a robot program (S1). This robot program describes an operation for performing assembly work. As described above, this robot program describes a method for moving from one teaching point to another teaching point, that is, an interpolation method such as linear interpolation, circular interpolation, joint interpolation, or the like. In particular, it is assumed that the moving method of passing the robot hand 202 in front of the camera 500 is described by linear interpolation. That is, the robot program is described so as to linearly move from a certain first teaching point to a second teaching point in the vicinity of a position where the robot hand 202 acquires the workpiece W1. The CPU 401 calculates the trajectory data of the robot arm 201 based on the robot program (S2).

  Based on the trajectory data before correction, the CPU 401 is in a state where the seating surface of the base portion 220 of the robot hand 202 is parallel to the XY plane, that is, a state where the rotation axis C1 and the central axis C2 are perpendicular to the XY plane. Initially set the posture of the robot arm 201.

  Then, the CPU 401 operates the robot arm 201 based on the trajectory data before correction, and moves the robot hand 202 relative to the camera 500 (S3: movement process, movement process). Specifically, the CPU 401 rotates in the rotation stopped state in which the link 216 is stopped, and the robot hand 202 is in a direction horizontal to the XY plane and in a direction crossing the imaging range of the camera 500 (X-axis direction). The operation of the robot arm 201 is started so as to move. That is, the robot hand 202 (link 216) is moved in the X-axis direction horizontal to the XY plane in a state where the central axis C2 of the robot hand 202 is perpendicular to the XY plane.

  The rotation stop state of the link 216 is a state in which the angle of the joint J6 of the robot arm 201 maintains a constant reference angle (for example, 0 °). In the present embodiment, the CPU 401 controls the joints J1 to J5 other than the joint J6 so that the link 216 linearly moves in the horizontal direction with respect to the imaging surface (that is, the XY plane) of the camera 500.

  The CPU 401 sends a command to the CPU 301 to start imaging before the robot hand 202 (that is, the mark MK) enters the imaging range of the camera 500 or when it is within the imaging range. In response to this command, the CPU 301 causes the camera 500 to start imaging (S4: imaging process, imaging process). That is, the CPU 301 causes the camera 500 to image the robot hand 202 while the rotation of the link 216 is stopped while the robot hand 202 passes through the imaging range of the camera 500. The camera 500 transmits a captured image to the CPU 301 at a predetermined frame rate.

  Next, the CPU 401 switches to a rotation state in which the link 216 is rotated around the rotation axis C1 while the robot hand 202 (that is, the mark MK) is passing through the imaging range of the camera 500. That is, the CPU 401 starts rotation of the joint J6 of the robot arm 201 while the robot hand 202 passes through the imaging range of the camera 500 (S5). The CPU 301 causes the camera 500 to image the robot hand 202 in this rotating state. The camera 500 transmits a captured image to the CPU 301 at a predetermined frame rate.

  The rotation operation of the link 216 is an operation that is not described in the robot program for performing the assembly operation. In other words, since the correction data for correcting the trajectory data has not yet been acquired in one operation at the beginning of the repetitive operation, the link 216 is added to the operation based on the trajectory data before correction calculated in step S2. Rotate. Specifically, the link 216 is rotated around the rotation axis C1 while causing the rotation axis C1 of the link 216 to move linearly in the X-axis direction, and the camera 500 captures an image.

  Then, the CPU 401 rotates the link 216 one or more rotations, preferably three or more rotations within the imaging range of the camera 500, and completes imaging when the robot hand 202 (mark MK) is out of the imaging range. To In response to this command, the CPU 301 causes the camera 500 to complete imaging (S6).

  After completing the imaging, the CPU 401 causes the rotation angle of the link 216 that has been rotated to follow the joint command value of the original trajectory data.

  The CPU 301 generates one captured image in which the movement trajectory of the mark MK is reflected from the plurality of captured images obtained by the imaging processing in steps S4 to S6. The CPU 301 records a captured image in which the movement trajectory of the mark MK is reflected in a storage device such as the HDD 304.

  FIG. 5A is a schematic diagram illustrating an example of a captured image in which a moving locus of a mark is reflected in the embodiment. The captured image IM has a movement trajectory T0 composed of a partial trajectory T1 of the mark MK in the rotation stop state E1 in which the rotation of the link 216 is stopped and a partial trajectory T2 of the mark MK in the rotation state E2 in which the link 216 is rotated. It is reflected.

  In the present embodiment, when the partial trajectories T1 and T2 are imaged, the movement speed of the link 216 in the X-axis direction is constant, while when the partial trajectory T1 is imaged, the rotation of the link 216 is stopped and when the partial trajectory T2 is imaged. The rotation speed of the link 216 is constant. FIG. 5A shows a case where the moving speed of the rotation axis C1 of the link 216 in the X-axis direction is the same as the speed of the mark MK when the partial locus T2 is imaged.

  Next, the CPU 301 calculates the positional deviation of the central axis C2 of the robot hand 202 with respect to the rotation axis C1 of the link 216 based on the locus of the central axis C2 of the robot hand 202 in the captured image, that is, the movement locus T0 of the mark MK ( S7: Misregistration calculation step). This positional deviation includes a positional deviation amount and a positional deviation direction.

  The CPU 301 sends the misregistration data to the CPU 401, and the CPU 401 records the misregistration data acquired from the CPU 301 in a storage device such as the HDD 404 (S8).

  The CPU 401 corrects the trajectory data of the robot arm 201 obtained in step S2 using the positional deviation data (S9: correction process, correction process). That is, after acquiring the positional deviation data, the CPU 401 operates the robot arm 201 based on the corrected trajectory data. Therefore, the CPU 401 operates the robot arm 201 in accordance with the corrected trajectory data, causes the robot hand 202 to grip the workpiece W1, and performs assembly work for assembling the workpiece W1 to the workpiece W2 (S10: Work). Process, work process).

  As described above, the robot control method is executed through steps S1 to S9, that is, the assembly part manufacturing method is executed through steps S1 to S10.

  Hereinafter, the positional deviation calculation process (the positional deviation calculation process) in step S7 will be specifically described. In FIG. 5A, the robot hand 202 moves linearly in the X-axis direction, and the state in which the rotation angle of the joint J6 stops from the reference angle (for example, 0 °) is changed to the rotation state. The captured image IM which image | photographed a mode that it is is illustrated. The trajectory T0 indicates the movement trajectory of the center point of the mark MK.

  First, the CPU 301 obtains a swing width (2 × R0) of the trajectory T0 (partial trajectory T2) with respect to a direction (Y-axis direction) orthogonal to the moving direction (X-axis direction) of the rotation axis C1 in the captured image. Then, the CPU 301 calculates a positional deviation amount R0 of the center axis C2 of the robot hand 202 with respect to the rotation axis C1 of the link 216 based on the swing width (2 × R0).

  More specifically, the CPU 301 analyzes the image and calculates lines (broken lines) L1 passing through the upper limit peaks P1, P3, and P5 of the trajectory T0 (partial trajectory T2). Further, the CPU 301 performs image analysis to calculate a line (broken line) L2 passing through the lower limit peaks P2, P4, and P6 of the trajectory T0 (partial trajectory T2). Next, the CPU 301 calculates an intermediate line (one-dot chain line) L3 between the straight line L1 and the straight line L2. Here, the straight line L3 means the locus of the rotation axis C1 of the joint J6. Next, the CPU 301 calculates the distance (2 × R0) between the straight line L1 and the straight line L2 in the vertical direction (Y-axis direction) of the straight line L3, and multiplies this by 1/2 to calculate the positional deviation amount R0. .

  Further, the CPU 301 obtains an offset amount A0 of the partial locus T1 with respect to the straight line L3 (center position of the swing width (2 × R0)). Then, the CPU 301 calculates a positional deviation direction (angle) θ0 of the central axis C2 of the robot hand 202 with respect to the rotation axis C1 of the link 216 based on the offset amount A0 and the positional deviation amount R0 as the positional deviation.

  FIG. 5B is a diagram for explaining the positional deviation of the central axis of the robot hand with respect to the rotation axis of the tip link in the embodiment. Specifically, referring to FIGS. 5A and 5B, first, the CPU 301 calculates a distance (offset amount) A0 in the vertical direction (Y-axis direction) between the partial locus T1 and the straight line L3. To do. Next, the CPU 301 calculates the position shift direction (position shift angle) θ0 = arcsin (A0 / R0) from the offset amount A0 and the position shift amount R0 when the angle of the joint J6 is the reference angle (0 °). Calculate Here, the angle of the joint J6 is the angle of the link 216 with respect to the link 215. The angle of the joint J6 when the partial trajectory T1 is imaged is set as a reference angle. Therefore, the misalignment direction θ0 is an angle with respect to the reference angle. By this calculation, the position shift direction (position shift angle) θ0 of the central axis C2 of the robot hand 202 with respect to the rotation axis C1 of the link 216 when the partial trajectory T1 is imaged is obtained.

  As described above, according to the present embodiment, the displacement amount R0 and the displacement angle θ0 of the central axis C2 of the robot hand 202 can be obtained with high accuracy from the trajectory T0 while operating the robot arm 201. As a result, since the positional deviation of the robot hand 202 can be measured without stopping the operation of the robot 200 (that is, the robot arm 201) during the assembly operation (part manufacture), the tact time can be reduced.

  Further, since the mark MK is given to the robot hand 202, a special measurement jig is not necessary. Furthermore, by measuring the distance between the peaks of the trajectory T0 of the mark MK from the captured image IM, the positional deviation amount R0 can be measured with high accuracy without being affected by the rotational accuracy of the link 216. Also, the displacement direction θ0 can be measured with high accuracy based on the measurement result of the trajectory T0.

  Further, since the offset direction A0 and the offset amount R0 of the partial trajectory T1 can be obtained from the captured image IM and calculated based on these values A0 and R0, the calculation load is small and the trajectory can be quickly obtained. Data can be corrected. As a result, the operation of the robot arm 201 can be quickly corrected, and the tact time can be reduced.

  Further, since the trajectory data is corrected, there is no need for expensive parts for mounting the robot hand 202 to the robot arm 201 with high accuracy, and the cost can be reduced.

  In the above description, the case where the speed of the mark MK when the link 216 is rotated and the movement speed of the rotation axis C1 of the link 216 in the X-axis direction is the same has been described. And the speeds of each other may be different. FIG. 6A and FIG. 6B are schematic diagrams illustrating another example of a captured image in which a moving locus of a mark is reflected in the embodiment.

  FIG. 6A illustrates a case where the speed of the mark MK when the link 216 is rotated is faster than the moving speed of the rotation axis C1 of the link 216 in the X-axis direction. FIG. 6B illustrates a case where the speed of the mark MK when the link 216 is rotated is slower than the moving speed of the rotation axis C1 of the link 216 in the X-axis direction. In any case, the peaks P1 to P6 can be extracted from the captured image IM, and the positional deviation amount R0 can be obtained.

  In the above description, the case where the robot arm 201 is operated so that the link 216 linearly moves with respect to the imaging surface (XY plane) of the camera 500 has been described in step S3. However, the present invention is not limited to this. Absent. In step S3, the robot arm 201 may be operated so that the link 216 moves circularly (that is, circular interpolation) with respect to the imaging surface (XY plane) of the camera 500. For example, the joints J2 to J5 may be fixed (stopped) and the joint J1 may be rotated to cause the camera 500 to image the robot hand 202.

  FIG. 7 is a schematic diagram illustrating still another example of the captured image in which the movement locus of the mark is reflected in the embodiment. FIG. 7 illustrates a captured image IM when the link 216 is moved in an arc. In step S <b> 7, the CPU 301 calculates the positional deviation of the central axis C <b> 2 of the robot hand 202 with respect to the rotation axis C <b> 1 of the link 216 from the captured image IM shown in FIG. 7 based on the trajectory T <b> 0 of the mark MK. More specifically, the CPU 301 analyzes the image and calculates an arc line (broken line) L1 passing through the upper limit peaks P1, P3, and P5 of the trajectory T0 (partial trajectory T2). Further, the CPU 301 performs image analysis to calculate an arc line (broken line) L2 passing through the lower limit peaks P2, P4, and P6 of the trajectory T0 (partial trajectory T2). In this case, the upper and lower peaks need to be at least 3 points each. Therefore, it is necessary to image the partial trajectory T2 by rotating the link 216 three or more times.

  Next, the CPU 301 calculates an intermediate line (one-dot chain line) L3 between the arc line L1 and the arc line L2. Here, the arc line L3 means the locus of the rotation axis C1 of the joint J6. Next, the CPU 301 calculates the distance (2 × R0) between the straight line L1 and the straight line L2 in the direction (radial direction) perpendicular to the arc line L3, and multiplies this by 1/2 to calculate the positional deviation amount R0. To do.

  Further, the CPU 301 obtains the offset amount A0 of the partial locus T1 with respect to the arc line L3 (the center position in the radial direction of the swing width (2 × R0)). Then, the CPU 301 calculates the positional deviation direction θ0 of the central axis C2 of the robot hand 202 relative to the rotation axis C1 of the link 216 based on the offset amount A0 and the positional deviation amount R0 as the positional deviation. Thus, even if the link 216 is moved in an arc, the positional deviation of the robot hand 202 can be obtained with high accuracy.

  The present invention is not limited to the embodiment described above, and many modifications are possible within the technical idea of the present invention. In addition, the effects described in the embodiments of the present invention only list the most preferable effects resulting from the present invention, and the effects of the present invention are not limited to those described in the embodiments of the present invention.

  A program that realizes one or more functions of the above-described embodiments is supplied to a system or apparatus via a network or a storage medium, and is also realized by a process in which one or more processors in a computer of the system or apparatus read and execute the program Is possible. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

  Moreover, although the above-mentioned embodiment demonstrated the case where the front end link 216 moved linearly or circularly, it is not limited to this. The operation may be performed by combining linear movement and circular movement. In addition, any movement may be performed without being limited to these moving methods. In this case, the locus of the center of the joint J6 is obtained by drawing an approximate curve from the peak of the locus, and the amount of displacement and the displacement direction. May be calculated.

  In the above-described embodiment, the case where the distal link 216 is moved at a constant speed has been described. However, the present invention is not limited to this, and the movement speed may be changed. Moreover, although the case where the rotational speed of the distal end link 216 is also constant has been described, the rotational speed may change.

  In the above-described embodiment, the case where the link 216 is switched from the rotation stop state to the rotation state during the imaging of the robot hand 202 by the camera 500 has been described. However, the present invention is not limited to this. The link 216 may be switched from the rotation state to the rotation stop state, and the rotation state and the rotation stop state may be alternately performed once or more.

  In the above-described embodiment, the case where the robot arm 201 is a vertical articulated robot arm has been described. However, the present invention is not limited to this. The robot arm 201 may be various robot arms such as a horizontal articulated robot arm, a parallel link robot arm, and an orthogonal robot.

  In the above-described embodiment, the case where the mark MK is given to the robot hand 202 has been described. However, the present invention is not limited to this, and the case where the mark is given to the grasped object that the robot hand 202 holds. There may be. In this case, the mark may be formed on the grasped object so that the mark is positioned on the central axis C2 of the robot hand 202. In this case, it is necessary to cause the robot hand 202 to grasp the grasped object with high accuracy. Therefore, it is simple and preferable to give the mark MK to the robot hand 202 as in the above-described embodiment.

  In the above-described embodiment, the assembling work has been described as the work performed by the robot 200, but the present invention is not limited to the assembling work. The end effector may be a tool or a robot hand that holds the tool, and may perform various operations such as a screwing operation and an adhesive application operation. In this case, a mark may be given to the tool.

  Further, although the case where the mark MK is given on the central axis of the robot hand 202 has been described, if the locus of the position of the central axis of the robot hand can be obtained based on the member of the robot hand on the captured image, May not be given. Of course, it is preferable to add a mark because the calculation load is small.

  Moreover, although the above-mentioned embodiment demonstrated the case where the control part 801 was comprised by the some computer (CPU), the control part may be comprised by one computer (CPU).

  In the above-described embodiment, the case where the trajectory data is corrected based on the calculated positional deviation has been described. However, the present invention is not limited to this, and the positional deviation of the robot hand relative to the tip link itself may be corrected. In this case, a slide mechanism for sliding the robot hand on the tip link may be provided, and the positional deviation may be eliminated by the slide mechanism.

  In the above-described embodiment, the case has been described in which imaging processing is performed while the robot arm 201 is being operated based on the uncorrected trajectory data created by a robot program that performs assembly work and the like. However, the present invention is not limited to this. For example, a robot program for imaging the robot hand 202 may be created separately, and the imaging process may be performed while the robot arm 201 is operated based on the trajectory data created by the robot program.

  Further, in the above-described embodiment, the case where the positional deviation is calculated only when the robot hand 202 is replaced has been described. However, it may be performed every time the assembling work is performed.

  In the above-described embodiment, the case where the robot hand 202 is imaged even in the rotation stop state has been described. However, the robot hand 202 may be imaged only in the rotation state. In this case, the position shift direction (angle) of the central axis C2 of the robot hand 202 can be obtained from the joint command value of the joint J6 at the peak of the locus waveform.

  In the above-described embodiment, the case where the camera 500 captures an image at a predetermined frame rate has been described. However, the present invention is not limited to this. When the robot hand 202 (mark MK) is imaged, the locus of the mark MK may be imaged with the shutter kept open.

DESCRIPTION OF SYMBOLS 100 ... Robot apparatus, 201 ... Robot arm, 202 ... Robot hand (end effector), 216 ... Link (tip link), 500 ... Camera (imaging device), 801 ... Control part, C1 ... Rotation axis, C2 ... Center axis

Claims (13)

The control unit is a robot control method for controlling the operation of a robot arm having a tip link to which an end effector is attached,
A moving step in which the control unit moves the end effector with respect to an imaging device that images the subject within the imaging range by operating the robot arm;
An imaging step for causing the imaging device to image the end effector in a rotating state in which the control unit rotates the tip link about a rotation axis while the end effector passes through the imaging range;
The control unit calculates a positional deviation of the central axis of the end effector with respect to the rotation axis of the distal end link based on a locus of the central axis of the end effector in the captured image obtained in the imaging process. And a robot control method.   The robot control method according to claim 1, further comprising a correction step in which the control unit corrects trajectory data defining the operation of the robot arm based on the positional deviation calculated in the positional deviation calculating step. In the misregistration calculation step, the control unit as the misregistration,
The position shift amount of the center axis of the end effector with respect to the rotation axis of the tip link is calculated based on a swing width of the locus with respect to a direction orthogonal to the moving direction of the rotation axis in the captured image. The robot control method described. In the imaging step, the control unit further causes the imaging device to image the end effector in a rotation stopped state in which the end link is stopped while the end effector passes through the imaging range.
As the positional deviation,
Based on the offset amount of the partial trajectory imaged in the stopped state of the trajectory with respect to the center position of the deflection width and the positional deviation amount, the positional deviation direction of the central axis of the end effector with respect to the rotation axis of the tip link The robot control method according to claim 3, wherein:   In the moving step, the control unit moves the end effector horizontally with respect to the imaging surface of the imaging device in a state where the central axis of the end effector is perpendicular to the imaging surface of the imaging device. The robot control method according to claim 1, wherein the robot arm is operated.   The robot control method according to claim 1, wherein the locus is a movement locus of a mark located on a central axis of the end effector.   The robot control method according to claim 6, wherein the mark is attached to the end effector.   The robot control according to any one of claims 1 to 7, wherein, in the moving step, the control unit operates the robot arm so that the tip link moves linearly with respect to an imaging surface of the imaging device. Method.   The robot control according to any one of claims 1 to 7, wherein, in the moving step, the control unit operates the robot arm so that the tip link moves in an arc with respect to an imaging surface of the imaging device. Method. A moving step in which a control unit moves a robot arm to move an end effector attached to a tip link of the robot arm with respect to an imaging device that images a subject in an imaging range;
An imaging step for causing the imaging device to image the end effector in a rotating state in which the control unit rotates the tip link about a rotation axis while the end effector passes through the imaging range;
The control unit calculates a positional deviation of the central axis of the end effector with respect to the rotation axis of the distal end link based on a locus of the central axis of the end effector in the captured image obtained in the imaging process. Process,
A correction step in which the control unit corrects the trajectory data defining the operation of the robot arm with the positional deviation calculated in the positional deviation calculating step;
A work manufacturing method comprising: a work process in which the control unit operates the robot arm according to the trajectory data corrected in the correction process, and causes the end effector to perform a work to manufacture the part. A robot arm having a tip link rotatable about a rotation axis;
An end effector attached to the tip link;
An imaging device for imaging a subject within an imaging range;
A control unit for controlling the operation of the robot arm,
The controller is
A movement process of operating the robot arm to move the end effector relative to the imaging device;
An imaging process for causing the imaging device to image the end effector in a rotational state in which the end link is rotated around a rotation axis while the end effector passes through the imaging range;
A positional deviation calculation process for calculating a positional deviation of the central axis of the end effector with respect to the rotation axis of the distal end link based on a locus of the central axis of the end effector in the captured image obtained by the imaging process. Robot device to do.   The program for making a computer perform each process of the robot control method of any one of Claims 1 thru | or 9.   A computer-readable recording medium on which the program according to claim 12 is recorded.

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