Arm robot

Abstract

An arm robot in which a camera is provided to an arm, the arm robot imaging a plurality of mark members using the camera, processing captured images, and measuring the positions of the mark members. Moreover, the arm robot calculates an offset direction and an offset amount of the measured positions relative to pre-established reference positions of the plurality of mark members, and determines a location at which the arm deforms on the basis of the offset direction. The robot arm also corrects, on the basis of the calculated offset amount, a control parameter corresponding to the determined location of deformation from among a plurality of control parameters for controlling the position of the arm according to kinematics.

Description

Technical Field

[0001] This specification discloses an arm robot.

Background Art

[0002] Conventionally, an automatic teaching system has been proposed that includes a camera provided near the tip of an arm and a mark plate formed with a plurality of marks. The mark plate is placed in the working area of the robot, and the coordinate values of predetermined points of the plurality of marks are sequentially read in robot coordinate values via the camera (see, for example, Patent Document 1). This system captures an image of the mark with the camera, processes the image data of the mark, and measures the position of the mark. Subsequently, the system calculates the displacement amounts ΔX and ΔY in the XY directions between the measured position of the mark and the centroid (reference point) of the mark registered in advance. When either of the calculated displacement amounts ΔX and ΔY is greater than the respective threshold values αx and αy, the system finely moves the tip of the robot toward the centroid side of the mark until it becomes equal to or less than the threshold values αx and αy, measures the position of the mark with the camera, and repeats the process of calculating the displacement amounts ΔX and ΔY. Then, when the displacement amounts ΔX and ΔY become equal to or less than the threshold values αx and αy, the system registers the position at that time in the correction data table as the pair information between the work coordinate value and the robot coordinate value. Thereafter, the system repeats the above process for all the marks (35 marks) and registers the pair information between the work coordinate value and the robot coordinate value in the correction data table. When actually operating the robot, the conversion of the work coordinate value using the correction data to the robot coordinate value is performed, and the movement of the robot is controlled.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above-described system, pair information of work coordinate values and robot coordinate values is registered in the correction data table. Therefore, when causing the robot to perform work at a plurality of different work positions, in order to maintain good positional accuracy of the arm, a large number of correction data are required according to the work positions.

[0005] The main object of the present disclosure is to provide an arm robot that can maintain better positional accuracy of the arm even when deformation or the like occurs in the arm.

Means for Solving the Problem

[0006] The present disclosure has adopted the following means to achieve the above main object.

[0007] The arm robot of the present disclosure is an arm robot having an arm including a plurality of links connected via joint axes, a camera attached to the arm, a plurality of mark members, a measurement unit that images the plurality of mark members with the camera and processes an imaged image of the plurality of mark members to measure positions of the plurality of mark members, a determination unit that calculates a deviation direction and a deviation amount of the measured positions with respect to predetermined reference positions of the plurality of mark members, and determines a deformed portion of the arm based on the calculated deviation direction of the positions, a correction unit that corrects a control parameter corresponding to the determined deformed portion among a plurality of control parameters for kinematically controlling the position of the arm based on the calculated deviation amount, and is characterized by comprising the above.

[0008] In an arm robot equipped with a camera on the arm of the present disclosure, the camera images a plurality of mark members, processes the captured image, and measures their positions. Subsequently, the arm robot calculates the deviation direction and deviation amount of the measured positions of the plurality of mark members with respect to the predetermined reference positions, and determines the deformed portion of the arm based on the deviation direction. Then, the arm robot corrects, based on the calculated deviation amount, the control parameter corresponding to the determined deformed portion among the plurality of control parameters for kinematically controlling the position of the arm. As a result, among the plurality of control parameters for kinematically controlling the position of the arm, the appropriate control parameter corresponding to the deformed portion can be corrected by an appropriate amount. As a result, even if deformation or the like occurs in the arm, the arm robot can maintain good position accuracy of the arm.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

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Figure 8

Figure 9

Best Mode for Carrying Out the Invention

[0010] Next, embodiments for carrying out the present disclosure will be described with reference to the drawings.

[0011] FIG. 1 is an external perspective view of the arm robot according to this embodiment. FIG. 2 is a block diagram showing the electrical connection relationship between the robot body and the control device. The arm robot 10 is, for example, one that performs a predetermined operation on an object (workpiece). As shown in the figure, it includes a robot body 20, a control device 70 that controls the robot body 20, and a plurality of mark members 100 arranged around the robot body 20.

[0012] In this embodiment, the robot body 20 is configured as a 5-axis vertical articulated robot. As shown in FIG. 1, this robot body 20 includes a base 21 installed on a workbench (not shown), and an arm 30 including a plurality of links (first to fifth links 31 to 35) connected in series via joint axes (first to fifth joint axes J1 to J5), and a camera 22 attached to the arm 30.

[0013] The first joint axis J1 that connects the base 21 and the first link 31 (base end link) extends in the vertical direction. The first link 31 can rotate left and right (horizontally pivot) about the vertical axis with respect to the base 21 by the first joint axis J1. The second joint axis J2 that connects the first link 31 and the second link 32, the third joint axis J3 that connects the second link 32 and the third link 33, and the fourth joint axis J4 that connects the third link 33 and the fourth link 34 each extend in the horizontal direction. The second link 32, the third link 33, and the fourth link 34 can rotate up and down about the horizontal axis by the corresponding joint axes J2, J3, and J4. The fifth joint axis J5 that connects the fourth link 34 and the fifth link 35 extends in a direction orthogonal to the fourth joint axis J4. The fifth link 35 can rotate with respect to the fourth link 34 by the fifth joint axis J5. Further, an end effector E is attached to the tip of the fifth link 35.

[0014] In this embodiment, a plurality of bolt holes penetrating in the axial direction of the third joint axis J3 are formed in the output member of the third joint axis J3 and the fastening portion 331 at the base of the third link 33. As shown in FIG. 1, the fastening portion 331 of the third link 33 is fastened to the output member of the third joint axis J3 so as to be rotatable with respect to the second link 32 by inserting a plurality of bolts B through the plurality of bolt holes.

[0015] Servo motors (first to fifth motors 41 to 45) for rotationally driving the corresponding joint axes and rotary encoders (first to fifth encoders 51 to 55) for detecting the rotational angles Θ1 to Θ5 of the corresponding servo motors are arranged on the first to fifth joint axes J1 to J5.

[0016] The camera 22 is attached to the fourth link 34. The camera 22 images an object (workpiece) and outputs the captured image to the control device 70. The control device 70 recognizes the position of the object by processing the captured image. Further, in this embodiment, the camera 22 images the mark member 100 and outputs the captured image to the control device 70. The control device 70 determines whether the arm 30 is deformed by processing the captured image, and corrects the position of the arm 30 based on the determination result. In this embodiment, three mark members 100 are installed around the robot body 20 at intervals in the circumferential direction.

[0017] As shown in Fig. 2, the control device 70 is configured as a microprocessor centered around the CPU 71. In addition to the CPU 71, it includes a ROM 72, an HDD 73 (storage device), a RAM 74, an input / output interface 75, and amplifiers 61 to 65 as drive circuits for the first to fifth motors 41 to 45. The control device 70 receives the angles Θ1, Θ2, Θ3, Θ4, Θ5 of the first to fifth joint axes J1 to J5, which are detection signals from the first to fifth encoders 51 to 55, via the corresponding amplifiers 61 to 65, and receives the imaging signal (image) from the camera 22 via the input / output interface 75. Further, drive currents (drive signals) from the control device 70 to the first to fifth motors 41 to 45 of the first to fifth joint axes J1 to J5 are output via the corresponding amplifiers 61 to 65. Furthermore, an input device 81 such as a mouse or a keyboard and an output device 82 such as a display are also connected to the control device 70.

[0018] Next, the operation of the arm robot 10 configured in this way will be described. The CPU 71 of the control device 70 first acquires the target position of the tip of the robot body 20. The target position of the tip is acquired, for example, by reading the data of a program created by an external computer. Subsequently, the CPU 71 calculates the angle command values θ1, θ2, θ3, θ4, θ5 of the first to fifth joint axes J1 to J5 for moving the tip to the target position by solving inverse kinematics with respect to the target position of the tip. Next, the CPU 71 performs feedback control calculation based on the deviation between the angles Θ1, Θ2, Θ3, Θ4, Θ5 and the angle command values θ1, θ2, θ3, θ4, θ5 so that the angles Θ1, Θ2, Θ3, Θ4, Θ5 of the first to fifth joint axes J1 to J5 detected by the first to fifth encoders 51 to 55 match the angle command values θ1, θ2, θ3, θ4, θ5 of the first to fifth joint axes J1 to J5, and calculates the torque command values Tm1*, Tm2*, Tm3*, Tm4*, Tm5* that are the torques to be output from the first to fifth motors 41 to 45. Then, the CPU 71 outputs control signals corresponding to the torque command values Tm1*, Tm2*, Tm3*, Tm4*, Tm5* to the corresponding amplifiers 61 to 65 respectively. As a result, torques corresponding to the torque command values Tm1*, Tm2*, Tm3*, Tm4*, Tm5* are output from the corresponding motors, and the tip of the arm robot 10 moves to the target position.

[0019] Figure 3 is an explanatory diagram for explaining the home position of the arm robot and the link coordinate systems set for each link of the arm. As shown in Figure 3, each link coordinate system has a base coordinate system Σ0 and link coordinate systems Σ1 to Σ5. The base coordinate system Σ0 is set on the base 21. The link coordinate system Σ1 is set on the first link 31 (the first joint axis J1). The link coordinate system Σ2 is set on the second link 32 (the second joint axis J2). The link coordinate system Σ3 is set on the third link 33 (the third joint axis J3). The link coordinate system Σ4 is set on the fourth link 34 (the fourth joint axis J4). The link coordinate system Σ5 is set on the fifth link 35 (the fifth joint axis J5) which is the end effector. Each coordinate system has the state where the second link 32, the third link 33, the fourth link 34, and the fifth link 35 extend in a substantially straight line as the home position. Also, in Figure 3, X0, X1, X2, X3, X4, X5 are the X axes of their respective coordinate systems. Y0, Y1, Y2, Y3, Y4, Y5 are the Y axes of their respective coordinate systems. Z0, Z1, Z2, Z3, Z4, Z5 are the Z axes of their respective coordinate systems.

[0020] Figure 4 is an explanatory diagram for explaining the dimensions between each link of the arm robot. Figure 5 is an explanatory diagram showing the coordinate transformation procedure of the link coordinate system. Figure 6 is an explanatory diagram showing the link parameter table used for the calculation of the inverse kinematics described above. In the figure, each link parameter a i-1 , b i-1 , d i-1 , α i , θ i is a parameter for converting from the coordinate system Σ i-1 to the coordinate system Σ i . Here, a i-1 is the distance in the X i-1 axis direction between the origin of the coordinate system Σ i and the origin of the coordinate system Σ i-1 . b i-1 is the distance in the Y i-1 axis direction between the origin of the coordinate system Σ i and the origin of the coordinate system Σ i-1 . α i is the rotation angle around the X i-1 axis of the coordinate system Σ i-1 . di-1 is the coordinate system Σ i-1 rotated about the X i-1 axis by α i-1 only, and the distance between the origin of the coordinate system Σ i-1 after rotation and the origin of the coordinate system Σ i in the Z-axis i direction is shown. θ i is the rotation angle about the Z-axis i-1 after rotating the coordinate system Σ i-1 about the X i-1 axis by α i only. The transformation matrix 0 T5 of the entire arm represents the relationship i-1 between each coordinate system according to the link parameter table i T i-1 (i = 1, 2, 3, 4, 5) and can be obtained by the following equation (1). The relationship (matrix) i-1 T i between each coordinate system can be obtained by the following equation (2). For the link parameters θ i dθ1, dθ2, dθ3, dθ4, dθ5, the origin angle offsets for aligning the origins of the first to fifth encoders 51 to 55 are included, and the above-described inverse kinematics for calculating the angle command values θ1, θ2, θ3, θ4, θ5 of each joint for moving the end effector to the target position are solved including the origin angle offset.

[0021]

Equation

[0022] Next, the operation when the arm 30 is deformed due to interference with an obstacle or the like will be described. FIG. 7 is a flowchart showing an example of the arm position correction process executed by the CPU 71 of the control device 70.

[0023] When the arm position correction process is executed, the CPU 71 first images the marks M1 to M3 attached to the upper surfaces of the three mark members 100 using the camera 22 (step S100). Subsequently, the CPU 71 measures the positions of the three marks M1 to M3 by processing the captured images (step S110). Then, the CPU 71 calculates the direction and amount of displacement of the measured marks M1 to M3 with respect to the reference positions by taking the difference between the predetermined reference positions of the respective marks M1 to M3 and the measured positions of the marks M1 to M3 (step S120).

[0024] Next, the CPU 71 determines the deformation pattern of the arm 30 based on the displacement directions of the respective marks M1 to M3 (step S130). In the present embodiment, as the deformation pattern of the arm 30, for example, a first deformation pattern in which the second link 32 is twisted with respect to the line connecting the center of the second joint axis J2 and the center of the third joint axis J3, and a second deformation pattern in which the third link 33 is displaced in the circumferential direction of the third joint axis J3 are defined as a plurality of deformation patterns. Here, the first deformation pattern is likely to occur mainly when the arm 30 collides with an interfering object when the arm 30 rotates horizontally. In this case, as shown in FIG. 8, the displacement direction is represented in the circumferential direction centered on the first joint axis J1. Also, the second deformation pattern is likely to occur mainly when the arm 30 collides with an interfering object when the arm 30 is extended. In this case, as shown in FIG. 9, the displacement direction is represented in the radial direction centered on the first joint axis J1. The determination of the deformation pattern is performed for each deformation pattern of the arm 30 by obtaining in advance, through experiments or the like, the displacement directions of the marks M1 to M3 measured by the camera 22 and registering them in the HDD 73 (storage device). When the displacement directions of the marks M1 to M3 are measured, the measured displacement directions are compared with the directions of the plurality of registered deformation patterns. Thereby, when the arm 30 is deformed, it becomes possible to specify the deformed portion.

[0025] Then, when the CPU 71 determines that the displacement direction calculated in step S120 does not match the direction of any of the deformation patterns ( "NO" in step S140), it determines that no correctable deformation has occurred in the arm 30 (step S150), and ends the arm position correction process without setting a correction value for correcting the position of the arm 30.

[0026] On the other hand, when the CPU 71 determines that the displacement direction calculated in step S120 matches the direction of any of the deformation patterns, it adjusts the link parameters corresponding to the corresponding deformation pattern based on the displacement amount calculated in step S120 (step S160), and ends the arm position correction process. In the arm robot 10 of the present embodiment, when the measured displacement direction matches the direction of the first deformation pattern, the link parameter dθ1 of the first link 31 (see FIG. 6) is adjusted in the direction that cancels out the displacement amount. Also, when the displacement direction matches the direction of the second deformation pattern, the link parameter dθ3 of the third link 33 (see FIG. 6) is adjusted in the direction that cancels out the displacement amount. As a result, even if the arm 30 is deformed due to a collision with an interfering object or the like, the position of the arm 30 can be controlled with high accuracy by correcting the position of the arm 30 by an amount corresponding to the deformation amount in the direction corresponding to the deformed portion.

[0027] Here, the correspondence between the main elements of the embodiment and the main elements of the present disclosure described in the claims will be described. That is, in the present embodiment, the first to fifth joint axes J1 to J5 correspond to joint axes, the first to fifth links 31 to 35 correspond to links, the arm 30 corresponds to an arm, the camera 22 corresponds to a camera, the mark member 100 and the CPU 71 of the control device 70 that executes the processes of steps S100 to S120 of the arm position correction process correspond to a measurement unit, the CPU 71 of the control device 70 that executes the processes of steps S130 and S140 of the arm position correction process corresponds to a determination unit, and the CPU 71 of the control device 70 that executes the processes of steps S160 and S170 of the arm position correction process corresponds to a correction unit. Further, the first link 31 corresponds to the base-end link, the second link 32 corresponds to the link connected to the base-end link, and the first joint axis J1 corresponds to the vertical axis. Further, the arm 30 corresponds to a vertically articulated arm, the third link 33 corresponds to at least one link, and the fastening portion 331 corresponds to a fastening portion.

[0028] It should be noted that the present disclosure is not limited to the above-described embodiment at all, and it goes without saying that the present disclosure can be implemented in various aspects as long as it belongs to the technical scope of the present disclosure.

[0029] For example, in the above-described embodiment, the three mark members 100 are provided at intervals in the circumferential direction around the robot body 20. However, the mark member 100 may be installed within the area that can be imaged by the camera 22. Further, the number of mark members 100 installed may be four or more, or two or less.

[0030] In the above-described embodiment, the arm 30 is configured as a vertically articulated arm. However, as long as it is an arm in which a plurality of links are connected via joint axes, such as a horizontally articulated arm, it may be configured as any other type of articulated arm. Further, the number of joint axes is not limited to five, and may be four or less, or six or more.

[0031] As described above, the arm robot of the present disclosure is an arm robot having an arm including a plurality of links connected via joint axes, a camera attached to the arm, a plurality of mark members, a measurement unit that images the plurality of mark members with the camera and processes an imaged image of the plurality of mark members to measure positions of the plurality of mark members, a determination unit that calculates a deviation direction and a deviation amount of the measured positions with respect to predetermined reference positions of the plurality of mark members and determines a deformed portion of the arm based on the calculated deviation direction of the positions, and a correction unit that corrects, based on the calculated deviation amount, a control parameter corresponding to the determined deformed portion among a plurality of control parameters for kinematically controlling the position of the arm. This is the gist of the present disclosure.

[0032] According to the arm robot of the present disclosure provided with a camera on the arm, among a plurality of control parameters for kinematically controlling the position of the arm, an appropriate control parameter corresponding to a deformed portion can be corrected by an appropriate amount. As a result, even if deformation or the like occurs in the arm, it is possible to obtain an arm robot that can maintain good position accuracy of the arm.

[0033] In such an arm robot of the present disclosure, a proximal link among the plurality of links of the arm is connected to a base via a vertical axis, and the determination unit may determine that a link connected to the proximal link is deformed when the deviation direction includes a component in the circumferential direction of the vertical axis. By doing so, even when the arm interferes with an interfering object when the arm pivots about the vertical axis, it is possible to control the position of the arm with high accuracy.

[0034] Also, in the arm robot of the present disclosure, the arm is a vertically articulated arm, and at least one of the plurality of links of the vertically articulated arm has a fastening portion fastened to the joint axis by a bolt inserted in a direction parallel to the joint axis. When the deviation direction includes a radial component of the vertical axis, the determination unit may determine that the fastening portion is deformed. In this way, even when the arm interferes with an interfering object when the arm extends, it is possible to control the position of the arm with high accuracy.

[0035] Furthermore, in the arm robot of the present disclosure, the plurality of mark members may be installed at intervals in the circumferential direction around the vertical axis. In this way, it is possible to more accurately determine the deformed portion (position deviation direction) and the amount of deformation (position deviation amount) of the arm with a small number of mark members.

[0036] Also, in the arm robot of the present disclosure, three mark members may be installed as the plurality of mark members. In this way, it is possible to more accurately determine the deformed portion (position deviation direction) and the amount of deformation (position deviation amount) of the arm with a small number of mark members.

[0037] Note that the present disclosure is in the form of an arm robot, but it may also be in the form of a method for correcting the position deviation of the arm.

Industrial Applicability

[0038] The present disclosure can be used in the manufacturing industry of arm robots and the like.

Explanation of Reference Numerals

[0039] 10 Arm robot, 20 Robot body, 21 Base, 22 Camera, 31 First link, 32 Second link, 33 Third link, 34 Fourth link, 35 Fifth link, 41 First motor, 42 Second motor, 43 Third motor, 44 Fourth motor, 45 Fifth motor, 51 First encoder, 52 Second encoder, 53 Third encoder, 54 Fourth encoder, 55 Fifth encoder, 61 - 65 Amplifiers, 70 Control device, 71 CPU, 72 ROM, 73 HDD, 74 RAM, 75 Input / output interface (I / F), 81 Input device, 82 Output device, 100 Mark member, M1 - M3 Marks, B Bolt, 331 Fastening part, E End effector.

Claims

1. An arm robot having an arm including a plurality of links connected via a joint axis, a camera attached to the arm, a plurality of mark members, a measurement unit that images the plurality of mark members with the camera and processes an imaged image of the plurality of mark members to measure positions of the plurality of mark members, a determination unit that calculates a deviation direction and a deviation amount of the measured positions with respect to predetermined reference positions of the plurality of mark members, and determines a deformed portion of the arm by comparing the calculated deviation direction of the positions with each of directions of a plurality of registered deformation patterns, a correction unit that corrects a control parameter corresponding to the determined deformed portion among a plurality of control parameters for kinematically controlling the position of the arm based on the calculated deviation amount, An arm robot comprising the above.

2. The arm robot according to claim 1, wherein a base link among the plurality of links of the arm is connected to a base via a vertical axis, and the determination unit determines that a link connected to the base link is deformed when the deviation direction includes a component in the circumferential direction of the vertical axis. An arm robot.

3. The arm robot according to claim 2, wherein the arm is a vertically articulated arm, and at least one link among the plurality of links of the vertically articulated arm has a fastening portion fastened to the joint axis by a bolt inserted in a direction parallel to the joint axis, and the determination unit determines that the fastening portion is deformed when the deviation direction includes a component in the radial direction of the vertical axis. An arm robot.

4. The arm robot according to claim 2 or 3, wherein the plurality of mark members are installed at intervals in the circumferential direction around the vertical axis. An arm robot.

5. The arm robot according to any one of claims 1 to 4, wherein three mark members are installed as the plurality of mark members. An arm robot.

Images