Arm robot

Abstract

An arm robot having a camera in an arm uses the camera to take images of a plurality of marker members, and determines positions thereof by processing the images. Next, the arm robot calculates a direction and an amount of shift of the determined positions from predetermined reference positions of the plurality of marker members, and determines a deformed portion of the arm based on the direction of shift. Furthermore, the arm robot corrects a control parameter corresponding to the determined deformed portion among a plurality of control parameters for controlling positions of the arm by kinematics, based on the calculated amount of shift.

Description

TECHNICAL FIELD

[0001] The present specification discloses an arm robot. BACKGROUND

[0002] In the past, an automatic teaching system has been proposed which is provided with a camera disposed near the front end portion of an arm and a marker plate formed with a plurality of markers, and which reads the coordinate values of predetermined points of the plurality of markers in the robot coordinate values in order by arranging the marker plate in the work area of the robot (for example, refer to Patent Document 1). This system captures the markers using the camera, and measures the positions of the markers by processing the image data of the markers. Next, the system calculates the offsets ΔX, ΔY in the XY directions of the measured positions of the markers and the center of gravity (reference point) of the markers registered in advance. The system repeatedly performs the following processing until the offsets ΔX, ΔY become equal to or less than the respective threshold values ax, ay: slightly moving the front end portion of the robot toward the center of gravity of the markers, measuring the positions of the markers using the camera, and calculating the offsets ΔX, ΔY, in the case where either of the calculated offsets ΔX, ΔY is greater than the respective threshold values ax, ay. Also, the system registers the position at this time as the correspondence information between the workpiece coordinate values and the robot coordinate values in the correction data table. Thereafter, the system repeatedly performs the above processing with respect to all of the markers (35 markers), and registers the correspondence information between the workpiece coordinate values and the robot coordinate values in the correction data table. In the case where the robot actually performs work, the transformation of the workpiece coordinate values to the robot coordinate values is performed using the correction data, and the movement of the robot is controlled.

[0003] PRIOR ART DOCUMENTS

[0004] Patent Document 1: Japanese Patent Application Laid-Open No. 4-4406 SUMMARY

[0005] PROBLEMS TO BE SOLVED BY THE INVENTION

[0006] In the above system, the correspondence information between the workpiece coordinate values and the robot coordinate values is registered in the correction data table. Therefore, in the case where the robot performs work at different work positions, many correction data are required in order to maintain the position accuracy of the arm well according to the work positions.

[0007] The main object of the present disclosure is to provide an arm robot which can maintain the position accuracy of the arm well even if the arm is deformed or the like.

[0008] MEANS FOR SOLVING THE PROBLEMS

[0009] The present disclosure employs the following means in order to achieve the above main object.

[0010] The arm robot of the present disclosure has an arm including a plurality of links connected via joint axes, and the gist thereof is that the arm robot is provided with:

[0011] a camera mounted to the arm;

[0012] a plurality of marker members;

[0013] a measurement unit that captures the plurality of marker members using the camera, and measures the positions of the plurality of marker members by processing captured images of the plurality of marker members;

[0014] a determination unit that calculates a direction and an amount of shift of the measured positions with respect to predetermined reference positions of the plurality of marker members, and determines a deformed portion of the arm based on the calculated direction of shift of the positions; and

[0015] a correction unit that corrects a control parameter corresponding to the determined deformed portion among a plurality of control parameters for controlling the positions of the arm by kinematics, based on the calculated amount of shift.

[0016] In the arm robot of the present disclosure in which the arm is provided with a camera, a plurality of marker members are captured using the camera, and the positions thereof are measured by processing captured images. Next, the arm robot calculates a direction and an amount of shift of the measured positions with respect to predetermined reference positions of the plurality of marker members, and determines a deformed portion of the arm based on the direction of shift of the positions. Furthermore, the arm robot corrects a control parameter corresponding to the determined deformed portion among a plurality of control parameters for controlling the positions of the arm by kinematics, based on the calculated amount of shift. Thus, a suitable control parameter corresponding to the deformed portion among a plurality of control parameters for controlling the positions of the arm by kinematics can be corrected by a suitable amount. As a result, an arm robot that can maintain the position accuracy of the arm well even when the arm is deformed or the like can be provided. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is an appearance perspective view of the arm robot of the present embodiment.

[0018] Figure 2 is a block diagram showing the electrical connection relationship between the robot main body and the control device.

[0019] Figure 3 is an explanatory diagram explaining the original positions of the arm robot and the link coordinate systems set to each link of the arm.

[0020] Figure 4 is an explanatory diagram explaining the dimensions between each link of the arm robot.

[0021] Figure 5 is an explanatory diagram showing the coordinate transformation process of the link coordinate system.

[0022] Figure 6 Fig. 9 is an explanatory diagram showing a link parameter table.

[0023] Figure 7 Fig. 10 is a flowchart showing an example of an arm position correction process.

[0024] Figure 8 Fig. 11 is an explanatory diagram showing a position shift direction and a position shift amount when a mark is photographed in a state where the arm is deformed in a first deformation mode.

[0025] Figure 9 Fig. 12 is an explanatory diagram showing a position shift direction and a position shift amount when a mark is photographed in a state where the arm is deformed in a second deformation mode. DETAILED DESCRIPTION

[0026] Next, with reference to the accompanying drawings, a mode for carrying out the present disclosure will be described. Figure 1

[0027] Figure 1 Fig. 1 is an appearance perspective view of an arm robot of the present embodiment. Figure 2 Fig. 2 is a block diagram showing an electrical connection relationship between a robot main body and a control device. The arm robot 10, which performs a predetermined work on an object (workpiece), for example, has a robot main body 20, a control device 70 that controls the robot main body 20, and a plurality of mark members 100 arranged around the robot main body 20, as shown in the figure.

[0028] In the present embodiment, the robot main body 20 is configured as a 5-axis vertical multi-joint robot. As shown in the figure, the robot main body 20 has a base body 21 provided on a work table (not shown), 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 mounted to the arm 30. Figure 1

[0029] ​​The first joint shaft J1 that links the base 21 and the first link 31 (proximal link) to each other extends in the vertical direction. The first link 31 is able to turn left and right (horizontal swing) with the vertical axis as a fulcrum with respect to the base 21 through the first joint shaft J1. The second joint shaft J2 that links the first link 31 and the second link 32 to each other, the third joint shaft J3 that links the second link 32 and the third link 33 to each other, and the fourth joint shaft J4 that links the third link 33 and the fourth link 34 to each other respectively extend in the horizontal direction. The second link 32, the third link 33, and the fourth link 34 are able to turn up and down with the horizontal axis as a fulcrum through the corresponding joint shafts J2, J3, J4. The fifth joint shaft J5 that links the fourth link 34 and the fifth link 35 to each other extends in a direction orthogonal to the fourth joint shaft J4. The fifth link 35 is able to rotate with respect to the fourth link 34 through the fifth joint shaft J5. In addition, an end effector E is attached to the distal end portion of the fifth link 35.

[0030] In the present embodiment, a plurality of bolt holes that pass through in the axial direction of the third joint shaft J3 are formed in the fastening portion 331 of the proximal end portion of the third link 33. As shown in FIG. 6, the fastening portion 331 of the third link 33 is fastened to the output member of the third joint shaft J3 in a manner that is able to turn with respect to the second link 32 by inserting a plurality of bolts B into the plurality of bolt holes. Figure 1

[0031] The first to fifth joint shafts J1 to J5 are provided with a servo motor (first to fifth motors 41 to 45) that drives rotation of the corresponding joint shaft and a rotary encoder (first to fifth encoders 51 to 55) that detects the rotation angle Θ1 to Θ5 of the corresponding servo motor.

[0032] The camera 22 is attached to the fourth link 34. The camera 22 photographs an object (workpiece) and outputs the photographed image to the control device 70. The control device 70 recognizes the position of the object by processing the photographed image. In the present embodiment, the camera 22 photographs the marker member 100 and outputs the photographed image to the control device 70. The control device 70 determines whether or not the arm 30 is deformed by processing the photographed image and corrects the position of the arm 30 on the basis of the determination result. In the present embodiment, three marker members 100 are provided at intervals in the circumferential direction around the robot main body 20.

[0033] As shown in FIG. 7, the marker member 100 is provided with a plurality of marker portions 101 that are arranged in the circumferential direction. The marker portions 101 are arranged at intervals in the circumferential direction. The marker portions 101 are arranged in the circumferential direction at intervals of 30 degrees. The marker portions 101 are arranged in the circumferential direction at intervals of 30 degrees. Figure 2 ​As shown, the control device 70 is configured as a microprocessor centered on the CPU 71, and in addition to the CPU 71, has a ROM 72, a HDD 73 (storage device), a RAM 74, an input / output interface 75, amplifiers 61 to 65 that are drive circuits for the first to fifth motors 41 to 45, and the like. With respect to the control device 70, detection signals from the first to fifth encoders 51 to 55, i.e., the angles Θ1, Θ2, Θ3, Θ4, Θ5 of the first to fifth joint axes J1 to J5, are input via the corresponding amplifiers 61 to 65, and a captured signal (image) from the camera 22 is input via the input / output interface 75. In addition, drive currents (drive signals) for the first to fifth motors 41 to 45 with respect to the first to fifth joint axes J1 to J5 are output from the control device 70 via the corresponding amplifiers 61 to 65. Furthermore, an input device 81 such as a mouse or keyboard, and an output device 82 such as a display are connected to the control device 70.

[0034] Next, the operation of the arm robot 10 thus configured will be described. The CPU 71 of the control device 70 first acquires a target position of the hand tip of the robot body 20. In addition, the target position of the hand tip is acquired, for example, by reading in data of a program created by an external computer. Next, the CPU 71 calculates angle command values θ1, θ2, θ3, θ4, θ5 of the first to fifth joint axes J1 to J5 for moving the hand tip to the target position by solving inverse kinematics with respect to the target position of the hand tip. Next, the CPU 71 calculates torques, i.e., torque commands Tm1*, Tm2*, Tm3*, Tm4*, Tm5*, that should be output from the first to fifth motors 41 to 45 by feedback control calculation based on the deviation of the angles Θ1, Θ2, Θ3, Θ4, Θ5 detected by the first to fifth encoders 51 to 55 from the angle command values θ1, θ2, θ3, θ4, θ5 in a manner such 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 coincide with the angle command values θ1, θ2, θ3, θ4, θ5 of the first to fifth joint axes J1 to J5. Furthermore, the CPU 71 outputs control signals corresponding to the torque commands Tm1*, Tm2*, Tm3*, Tm4*, Tm5* to the corresponding amplifiers 61 to 65. As a result, torques corresponding to the torque commands Tm1*, Tm2*, Tm3*, Tm4*, Tm5* are output from the corresponding motors, and the hand tip of the arm robot 10 moves to the target position.

[0035] Figure 3 is an explanatory view that explains the home position of the arm robot and the link coordinate system set for each link of the arm. As shown in Figure 3As shown, the coordinate systems of the links have a base coordinate system Σ0and link coordinate systems Σ1to Σ5. The base coordinate system Σ0is set to the base 21. The link coordinate system Σ1is set to the first link 31 (first joint axis J1). The link coordinate system Σ2is set to the second link 32 (second joint axis J2). The link coordinate system Σ3is set to the third link 33 (third joint axis J3). The link coordinate system Σ4is set to the fourth link 34 (fourth joint axis J4). The link coordinate system Σ5is set to the fifth link 35 (fifth joint axis J5) which is the hand tip. Each coordinate system sets a state in which 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 original position. Further, in Figure 3 X0, X1, X2, X3, X4, X5 are X axes of the respective coordinate systems. Y0, Y1, Y2, Y3, Y4, Y5 are Y axes of the respective coordinate systems. Z0, Z1, Z2, Z3, Z4, Z5 are Z axes of the respective coordinate systems.

[0036] Figure 4 is an explanatory view which explains the dimensions between the links of the arm robot. Figure 5 is an explanatory view which shows a coordinate transformation procedure of the link coordinate system. Figure 6 is an explanatory view which shows a link parameter table used in the above-mentioned inverse kinematics calculation. In the figure, each link parameter a i-1 , b i-1 , d i-1 , α i , θ i of the ith link (i = 1, 2, 3, 4, 5) is a parameter for transformation from the coordinate system Σ i-1 to the coordinate system Σ i . Here, a i-1 represents a distance in the X i-1 axis direction between the origin of the coordinate system Σ i-1 and the origin of the coordinate system Σ i . b i-1 represents a distance in the Y i-1 axis direction between the origin of the coordinate system Σ i-1 and the origin of the coordinate system Σ i . α i represents a rotation angle of the coordinate system Σ i-1 around the X i-1 axis. d i-1 represents a distance in the Z axis i direction between the origin of the coordinate system Σ i-1 after the coordinate system Σ i-1 is rotated around the X i-1 axis by α i-1 and the origin of the coordinate system Σ i . θ i represents a rotation angle of the coordinate system Σ i-1 around the Yi-1 The axis rotates α i-1 The rotation angle around the Z axis after i The transformation matrix of the arm as a whole 0 T5 can be calculated using the relationship between the coordinate systems based on the link parameter table i-1 T i (i = 1, 2, 3, 4, 5) by the following equation (1). The relationship (matrix) between the coordinate systems i-1 T i can be calculated by the following equation (2). The origin angle bias for performing origin alignment of the first to fifth encoders 51 to 55 is included in dθ1, dθ2, dθ3, dθ4, dθ5 of the link parameters θ i The inverse kinematics for calculating the angle command values θ1, θ2, θ3, θ4, θ5 of the respective joints that move the hand tip to the target position includes the origin angle bias and is solved.

[0037] [Num 1]

[0038] 0 T5 = T1 0 T1 1 T2 2 T3 3 T4 4 T5...(1)

[0039]

[0040] Next, the operation when deformation occurs in the arm 30 due to interference with an obstacle or the like will be described. Figure 7 is a flowchart showing an example of arm position correction processing performed by the CPU 71 of the control device 70.

[0041] When the arm position correction processing is performed, the CPU 71 first captures the marks M1 to M3 marked on the upper surfaces of the three marker members 100 with the camera 22, respectively (step S100). Next, the CPU 71 determines the positions of the three marks M1 to M3 by processing the captured images (step S110). Also, the CPU 71 calculates the position offset direction and the position offset amount of the determined marks M1 to M3 with respect to the reference positions by obtaining the difference between the predetermined reference positions of the respective marks M1 to M3 and the determined positions of the marks M1 to M3 (step S120).

[0042] Next, the CPU 71 determines the deformation mode of the arm 30 based on the position offset direction of each marker M1 to M3 (step S130). In this embodiment, as deformation modes of the arm 30, multiple deformation modes are defined, for example, including a first deformation mode in which the second link 32 is twisted relative 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 mode in which the third link 33 is offset circumferentially about the third joint axis J3. Here, the first deformation mode is mainly likely to occur when the arm 30 collides with an interfering object when the arm 30 rotates horizontally. In this case, as Figure 8 As shown in FIG. 1 , the positional deviation direction appears in the circumferential direction centered on the first joint axis J1. In addition, the second deformation mode is likely to occur mainly when the arm 30 collides with an interfering object when the arm 30 is extended. In this case, Figure 9 As shown, the positional deviation directions occur in the radial direction centered on the first joint axis J1. Deformation mode determination is performed as follows: For each deformation mode of the arm 30, the positional deviation directions of the markers M1 to M3 measured by the camera 22 are previously determined through experiments or other means and registered in the HDD 73 (storage device). After the positional deviation directions of the markers M1 to M3 are measured, the measured positional deviation directions are compared with the directions of each of the multiple registered deformation modes. This allows the location of deformation to be identified when deformation of the arm 30 occurs.

[0043] Furthermore, if CPU71 determines that the position offset direction calculated in step S120 is inconsistent with the directions of all deformation modes ("No" in step S140), it determines that no correctable deformation has occurred in the arm 30 (step S150), does not set the correction value for correcting the position of the arm 30, and ends the arm position correction processing.

[0044] On the other hand, if the CPU 71 determines that the position deviation direction calculated in step S120 is consistent with the direction of any deformation mode, it adjusts the link parameters corresponding to the deformation mode that matches based on the position deviation amount calculated in step S120 (step S160), and ends the arm position correction process. In the arm robot 10 of this embodiment, when the measured position deviation direction is consistent with the direction of the first deformation mode, the link parameter dθ1 (refer to Figure 6 ) is adjusted in the direction of eliminating the positional deviation. In addition, when the positional deviation direction is consistent with the direction of the second deformation mode, the link parameter dθ3 of the third link 33 (refer to Figure 6 ) is adjusted in a direction that eliminates the positional deviation. Thus, even if arm 30 is deformed due to collision with an interfering object, for example, the position of arm 30 can be controlled with high precision by correcting the position of arm 30 in a direction corresponding to the deformed portion and by an amount corresponding to the deformation.

[0045] Here, the correspondence between the main elements of the embodiments and the main elements of the present disclosure recited in the claims is 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 marker 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 processing correspond to a measurement section, the CPU 71 of the control device 70 that executes the processes of steps S130, S140 of the arm position correction processing corresponds to a determination section, and the CPU 71 of the control device 70 that executes the processes of steps S160, S170 of the arm position correction processing corresponds to a correction section. In addition, the first link 31 corresponds to a base end link, the second link 32 corresponds to a link connected to the base end link, and the first joint axis J1 corresponds to a vertical axis. In addition, the arm 30 corresponds to a vertical multi-joint arm, the third link 33 corresponds to at least one link, and the fastening portion 331 corresponds to a fastening portion.

[0046] In addition, the present disclosure is not limited at all to the above-described embodiments, and can be implemented in various forms as long as it falls within the technical scope of the present disclosure, which is self-evident.

[0047] For example, in the above-described embodiment, the marker member 100 is provided three at intervals in the circumferential direction around the robot body 20. However, the marker member 100 can be provided as long as it is within a region that can be imaged by the camera 22. In addition, the number of marker members 100 can be four or more, or two or less.

[0048] In the above-described embodiment, the arm 30 is configured as a vertical multi-joint arm, but can be configured as any other type of multi-joint arm as long as it is an arm in which a plurality of links are connected via joint axes. In addition, the number of joint axes is not limited to five, and can be four or less, or six or more.

[0049] As described above, the arm-type robot of the present disclosure has an arm including a plurality of links connected via joint axes, and the gist thereof is that the above-described arm-type robot is provided with: a camera mounted to the above-described arm; a plurality of marker members; a measurement section that images the above-described plurality of marker members using the above-described camera, and measures the positions of the plurality of marker members by processing the imaged images of the plurality of marker members; a determination section that calculates the direction and amount of shift of the measured positions with respect to predetermined reference positions of the plurality of marker members, and determines a deformed portion of the above-described arm based on the calculated direction of shift of the positions; and a correction section that corrects a control parameter corresponding to the determined deformed portion among a plurality of control parameters for controlling the position of the above-described arm by kinematics, based on the calculated amount of shift.

[0050] According to the arm-type robot of the present disclosure in which the arm is provided with a camera, a suitable control parameter corresponding to a deformation site among a plurality of control parameters for controlling the position of the arm by kinematics can be corrected in a suitable amount. As a result, an arm-type robot that can maintain the position accuracy of the arm well even when the arm is deformed or the like can be provided.

[0051] In such an arm-type robot of the present disclosure, it can also be that a proximal end link of the plurality of links of the arm is connected to the base via a plumb axis, and in a case where the offset direction includes a component in the circumferential direction of the plumb axis, the determination unit determines that the link connected to the proximal end link of the arm is deformed. In this way, in a case where the arm interferes with the interference object when the arm pivots about the plumb axis as a fulcrum, the position of the arm can also be controlled with high accuracy.

[0052] In addition, in the arm-type robot of the present disclosure, it can also be that the arm is a vertical multi-joint arm, at least one link of the plurality of links of the vertical multi-joint arm has a fastening portion that is fastened to a joint axis by a bolt that is inserted through in a direction parallel to the joint axis, and in a case where the offset direction includes a component in the radial direction of the plumb axis, the determination unit determines that the fastening portion is deformed. In this way, in a case where the arm interferes with the interference object when the arm is stretched, the position of the arm can also be controlled with high accuracy.

[0053] Furthermore, in the arm-type robot of the present disclosure, it can also be that the plurality of marker members are arranged at intervals in the circumferential direction around the plumb axis. In this way, the deformation site (position offset direction) and the deformation amount (position offset amount) of the arm can be determined more accurately with fewer marker members.

[0054] In addition, in the arm-type robot of the present disclosure, it can also be that three marker members are provided as the plurality of marker members. In this way, the deformation site (position offset direction) and the deformation amount (position offset amount) of the arm can be determined more accurately with fewer marker members.

[0055] In addition, the present disclosure is configured as an arm-type robot, but can also be configured as an arm position offset correction method.

[0056] Industrial applicability

[0057] The present disclosure can be used in the manufacturing industry of arm-type robots and the like.

[0058] Explanation of reference signs

[0059] 10-arm robot, 20 robot main 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 marker member, M1-M3 markers, B bolt, 331 fastening portion, E end effector.

Claims

1. An arm-type robot having an arm including a plurality of links connected via joint axes, the arm-type robot comprising: a camera mounted on the arm; multiple marking components; a measuring unit that uses the camera to capture images of the plurality of marker members and processes the captured images of the plurality of marker members to measure positions of the plurality of marker members; a determination unit that calculates a direction and an amount of deviation of the measured position relative to predetermined reference positions of the plurality of marking members, and determines a deformed portion of the arm by comparing the calculated deviation direction of the position with directions of each of a plurality of deformation patterns registered in advance; and The correction unit 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 offset.

2. The arm-type robot according to claim 1, wherein: The base end link of the plurality of links of the arm is connected to the base body via a vertical shaft. When the offset direction includes a component in the circumferential direction of the vertical axis, the determination unit determines that the link connected to the link at the base end has deformed.

3. The arm-type robot according to claim 2, wherein: The arm is a vertical multi-jointed arm, At least one of the plurality of links of the vertical multi-jointed arm has a fastening portion fastened to the joint axis by a bolt inserted in a direction parallel to the joint axis. When the offset direction includes a component in the radial direction of the vertical axis, the determination unit determines that the fastening portion has been deformed.

4. The arm-type robot according to any one of claims 2 or 3, wherein: The plurality of marking members are provided around the vertical axis at intervals in the circumferential direction.

5. The arm-type robot according to any one of claims 1 to 3, wherein: Three marking members are provided as the plurality of marking members.

6. The arm-type robot according to claim 4, wherein: Three marking members are provided as the plurality of marking members.

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