Robot control method, and robot system

Abstract

To provide a technique capable of accurately performing teaching while accurately performing distance measurement.SOLUTION: A method includes the steps of: (a) setting a movable stage installed at the tip of a robot arm to a first position, and thereby positioning a range finder installed on the movable stage to a range-finding position for measuring a distance to a workpiece; (b) performing distance measurement by the range finder, in a state in which the movable stage is set at the first position, and teaching using the result of the distance measurement; (c) setting the movable stage at a second position different from the first position, and thereby positioning an end effector installed on the movable stage to a work position for performing robot work on the workpiece; and (d) performing the robot work on the workpiece, in a state where the movable stage is set at the second position.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to a method for controlling a robot and a robot system.

Background Art

[0002] Patent Document 1 discloses a painting robot that performs painting by discharging paint from a nozzle onto a vehicle or vehicle part to be painted. In this prior art, distance measuring means for measuring the distance between the painting part of the object to be painted and the nozzle discharge surface of the head is used, and control is executed so that paint is discharged from the nozzle when the distance measured by the distance measuring means is within a specified range.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the above prior art, since there is a physical distance between the head and the distance measuring means, there is a problem that when the surface of the object is a curved surface, the distance between the object and the head cannot be accurately measured. Also, when teaching is performed while measuring the distance, there is a problem that accurate teaching cannot be performed.

Means for Solving the Problems

[0005] According to a first aspect of the present disclosure, a method for controlling a robot is provided. The method includes: (a) positioning a distance measuring device installed on a movable stage installed at a tip of a robot arm at a distance measuring position for measuring a distance to a workpiece by setting the movable stage installed at the tip of the robot arm to a first position; (b) performing distance measurement by the distance measuring device and executing teaching using the result of the distance measurement while the movable stage is set to the first position; (c) positioning an end effector installed on the movable stage at a working position for performing a robot operation on the workpiece by setting the movable stage to a second position different from the first position; and (d) executing the robot operation on the workpiece while the movable stage is set to the second position.

[0006] According to a second aspect of the present disclosure, a robot system is provided. The robot system includes a robot including a robot arm, a movable stage installed at a tip of the robot arm, a distance measuring device installed on the movable stage, an end effector installed on the movable stage, and a control device. The control device is configured to execute: (a) a process of positioning the distance measuring device at a distance measuring position for measuring a distance to a workpiece by setting the movable stage to a first position; (b) a process of performing distance measurement by the distance measuring device and executing teaching using the result of the distance measurement while the movable stage is set to the first position; (c) a process of positioning the end effector at a working position for performing a robot operation on the workpiece by setting the movable stage to a second position different from the first position; and (d) a process of executing the robot operation on the workpiece while the movable stage is set to the second position.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Mode for Carrying Out the Invention

[0008] FIG. 1 is an explanatory diagram showing an example of a robot system in an embodiment. This robot system 10 includes a robot 100, a robot controller 200 that controls the robot 100, an information processing apparatus 300, a teaching pendant 400, and a pedestal 500 on which a workpiece WK is placed. The information processing apparatus 300 is, for example, a personal computer.

[0009] In FIG. 1, three axes X, Y, and Z that define a rectangular coordinate system in a three-dimensional space are drawn. The X-axis and the Y-axis are horizontal axes, and the Z-axis is a vertical axis. In this example, the XYZ coordinate system is a robot coordinate system with a reference point preset in the robot 100 as the origin.

[0010] The robot 100 includes a base 110 and a robot arm 120. A moving device 610 including a movable stage 612 is attached to the tip 122 of the robot arm 120. An ink ejection device 620 as an end effector and a distance measuring device 630 are installed on the movable stage 612. Note that the ink ejection device 620 and the distance measuring device 630 may be fixed to the movable stage 612 via attachment auxiliary members.

[0011] As the moving device 610, for example, a single-axis stage capable of moving the movable stage 612 in a single-axis direction can be used. Also, a multi-axis stage capable of moving the movable stage 612 in two or more directions may be used. In the present embodiment, a single-axis stage is used as the moving device 610. The movable stage 612 may be called a "slider" or a "table". As the driving method of the moving device 610, a driving method using an electromagnetic motor and a ball screw can be used. Alternatively, an electromagnetic driving method or an ultrasonic driving method may be used. When using a ball screw mechanism, a reduction mechanism can be used in combination to withstand a large load. Stages using an electromagnetic driving method or an ultrasonic driving method can have a small size and a light weight although the force is small. Also, in a method of driving the movable stage 612 using a piezoelectric actuator like the ultrasonic driving method, the movable stage 612 can be moved without generating a large vibration in the end effector.

[0012] The ink ejection device 620 has an ink ejection head 622. The ink ejection head 622 performs printing by ejecting ink onto the printing area on the surface of the workpiece WK. It is preferable that the ink ejection head 622 can eject a plurality of types of ink to perform color printing. The printing area on the surface of the workpiece WK may not be a flat surface and may include a curved surface portion. As can be understood from this description, the robot system 10 of the present embodiment functions as a DTS (Direct To Shape) printing device that prints on the surface of a three-dimensional object.

[0013] As the end effector, any device or mechanism other than the ink ejection device 620 can be used. For example, as the end effector, a coating device for applying a liquid agent, a welding device for performing welding, a robot hand used for precision assembly, etc. can be used.

[0014] The distance measuring device 630 is a device that measures the distance to the surface of the workpiece WK. As the distance measuring device 630, for example, a laser displacement meter, an infrared sensor, an ultrasonic sensor, a stereo camera, etc. can be used. In this embodiment, a laser displacement meter is used as the distance measuring device 630.

[0015] Near the tip of the robot arm 120, a TCP (Tool Center Point) as a control point of the robot 100 is set. In the example of FIG. 1, the TCP is set near the surface of the ink ejection head 622. Note that the control point TCP can be set at an arbitrary position.

[0016] The robot arm 120 is sequentially connected by six joints J1 to J6. Among these joints J1 to J6, three joints J2, J3, and J5 are bending joints, and the other three joints J1, J4, and J6 are twisting joints. In this embodiment, a six-axis robot is illustrated, but a robot having an arbitrary robot arm mechanism having a plurality of joints can be used. Further, although the robot 100 of this embodiment is a vertical articulated robot, a horizontal articulated robot may be used.

[0017] The teaching process of the robot 100 is performed using the information processing device 300 or the teaching pendant 400. In the embodiments described below, the information processing device 300 is used to execute the teaching process. The functions of the "control device" of the present disclosure are realized using at least a part of the robot controller 200, the information processing device 300, and the teaching pendant 400.

[0018] FIG. 2 is a block diagram showing the functions of the information processing apparatus 300. The information processing apparatus 300 includes a processor 310, a memory 320, and an interface circuit 330. An input device 340 and a display device 350 are connected to the interface circuit 330, and a robot controller 200 is also connected thereto. The robot 100, the teaching pendant 400, the moving device 610, the ink ejection device 620, and the distance measuring device 630 are connected to the information processing apparatus 300 via the robot controller 200. However, some of these may be directly connected to the information processing apparatus 300.

[0019] The processor 310 has functions as a teaching processing unit 311 and a robot work execution unit 312. The teaching processing unit 311 creates a robot control program RP by performing teaching using the result of distance measurement by the distance measuring device 630. The robot work execution unit 312 executes robot work using the robot control program RP. In the present embodiment, the robot work is work of printing on the workpiece WK using the ink ejection device 620.

[0020] The functions of the teaching processing unit 311 and the robot work execution unit 312 are respectively realized by the processor 310 executing a computer program stored in the memory 320. However, part or all of the functions of the teaching processing unit 311 and the robot work execution unit 312 may be realized by a hardware circuit.

[0021] The memory 320 stores a robot control program RP created by teaching processing. The robot control program RP is composed of a plurality of instructions for operating the robot 100 and includes coordinate values of a plurality of teaching points.

[0022] FIG. 3 is an explanatory diagram showing the states during teaching execution and during robot work execution. During teaching execution, the teaching processing unit 311 positions the distance measuring device 630 at a distance measuring position for measuring the distance to the workpiece WK by moving the movable stage 612 and setting it at the first position. The movable stage 612 is movable left and right in FIG. 3 along the moving direction Dm which is a one-axis direction. The distance measuring position of the distance measuring device 630 is a position where a virtual straight line extending in the measuring direction Ds of the distance measuring device 630 passes through the work target position Pw on the surface of the workpiece WK. The measuring direction Ds of the distance measuring device 630 is the direction from the reference position Ps of the distance measuring device 630 toward the measurement object. For example, when a laser displacement meter is used as the distance measuring device 630, the reference position Ps of the distance measuring device 630 corresponds to the position of the light receiving sensor. The teaching process is executed using the result of distance measurement by the distance measuring device 630 in a state where the movable stage 612 is set at such a first position.

[0023] During robot work execution, the robot work execution unit 312 positions the ink ejection device 620, which is an end effector, at a work position for performing robot work on the workpiece WK by moving the movable stage 612 from the first position to the second position. The work position of the ink ejection device 620 is a position where a virtual straight line extending in the reference direction De of the ink ejection device 620 passes through the work target position Pw on the surface of the workpiece WK. The reference direction De of the ink ejection device 620 is the direction from the reference position Pe of the ink ejection device 620 toward the work target position Pw of the workpiece WK. This reference direction De is parallel to the measuring direction Ds of the distance measuring device 630. The reference position Pe of the ink ejection device 620 is a position that serves as a reference for the work by the ink ejection device 620. Specifically, the reference position Pe of the ink ejection device 620 corresponds to the center position on the surface of the ink ejection head 622. The reference direction De of the ink ejection device 620 is parallel to the measuring direction Ds of the distance measuring device 630. In the present embodiment, the work target position Pw of the workpiece WK corresponds to the center position of the ink ejection area where ink is simultaneously ejected by the ink ejection head 622. Printing as robot work is executed in a state where the movable stage 612 is set at such a second position.

[0024] As can be understood from FIG. 3, the moving direction Dm of the movable stage 612 is set in a direction perpendicular to the reference direction De in which the ink ejection device 620 moves toward the workpiece WK when performing robot work. During teaching, by setting the movable stage 612 to the first position, the distance measuring device 630 is positioned at a distance measuring position for measuring the distance to the workpiece WK. During robot work, by moving the movable stage 612 from the first position to the second position, the ink ejection device 620 is positioned at a work position for performing work on the workpiece WK. As a result, teaching can be accurately performed while accurately measuring the distance. Further, teaching can be executed while moving the robot arm 120 along the same locus as the movement locus TR of the robot arm 120 during robot work.

[0025] The moving direction Dm of the movable stage 612 is preferably a direction perpendicular to or parallel to the rotational axis direction of the rotary joint J6 at the outermost end of the robot arm 120. In this way, regardless of the joint displacement of the rotary joint J6, the ink ejection device 620 and the distance measuring device 630 can be easily positioned at their respective appropriate positions.

[0026] FIG. 4 is an explanatory diagram showing an enlarged state during teaching execution. The origin position Pref of the distance measuring device 630 is a position where the distance measurement value Ls output from the distance measuring device 630 becomes 0, and can be initialized to an arbitrary position. In the example of FIG. 4, the origin position Pref of the distance measuring device 630 is initialized to a height equal to the surface position of the work WK. Further, the distance Le from the reference position Pe of the ink ejection device 620 to the surface of the work WK is equal to the set distance G suitable for ink ejection. In other words, the distance measuring device 630 is zero-point corrected so that its distance measurement value Ls indicates the difference between the set distance G suitable for ink ejection and the actual distance Le. The set distance G suitable for ink ejection is a so-called head gap, and an appropriate value is set in advance according to the type of the ink ejection device 620 and the attributes of the printing object. Generally, the set distance between the end effector and the work is set to a value according to the type of the end effector. Even when the origin position Pref of the distance measuring device 630 is initialized to a position at a different height from that in FIG. 4, it is possible to calculate the distance Le from the ink ejection device 620 to the work WK during robot operation according to the distance measurement value Ls from the distance measuring device 630 to the work WK.

[0027] As can be understood from the above description, the position of the teaching point set in teaching is preferably determined such that the distance Le from the ink ejection device 620 to the work WK calculated according to the distance measurement value Ls from the distance measuring device 630 to the work WK becomes equal to the set distance G suitable for robot operation. In this way, teaching can be executed so that the distance Le between the ink ejection device 620 and the work WK during robot operation becomes the desired set distance G.

[0028] FIG. 5 is a flowchart showing the processing procedures of teaching and robot operation. In step S11, the teaching processing unit 311 positions the movable stage 612 at the first position for teaching. As a result, as shown in FIG. 3, the distance measuring device 630 is positioned at the distance measuring position for measuring the distance to the work WK.

[0029] Steps S12 to S14 are executed by the teaching processing unit 311. In step S12, the teaching processing unit 311 executes teaching processing to set a plurality of teaching points.

[0030] FIG. 6 is an explanatory diagram showing an example of an operation screen for teaching processing. The teaching processing window W10 includes a robot selection field RF for selecting a robot type, a program selection field PF for specifying the program name of an operation program, a confirmation mode execution button EB, a confirmation mode stop button SB, a robot display window W11, and a jog operation window W12.

[0031] The robot display window W11 is a screen for displaying a simulation image of the robot 100. As the simulation image, either a three-dimensional image or a two-dimensional image can be selectively displayed. In a state where the three-dimensional image of the robot 100 is displayed, the user can arbitrarily change the viewing direction and the display magnification of the image by operating the mouse within the robot display window W11. In this example, a simulation image of the workpiece WK is also arranged within the robot display window W11. However, the robot display window W11 may be omitted.

[0032] The jog operation window W12 is a screen for the user to input a jog operation. The jog operation window W12 includes a coordinate system selection field CF for selecting a coordinate system, a coordinate value field VF1 for specifying six coordinate values corresponding to the selected coordinate system, a head gap display section HG for displaying the head gap, a teaching point field TF for specifying a teaching point to be edited, a teaching point setting button B1, and an end button B2. On the right side of the coordinate value field VF1, an increment / decrement button CB1 for increasing or decreasing the coordinate value is arranged. On the right side of the teaching point field TF, an increment / decrement button CB2 for increasing or decreasing the number of the teaching point is arranged.

[0033] On the head gap display unit HG, a distance index value indicating the distance Le between the ink ejection head 622 and the work WK described in FIG. 4 is displayed. As the distance index value, for example, the difference between the set distance G of the head gap and the actual distance Le, that is, the head gap error, is displayed. As described above, the distance measuring device 630 is zero-point corrected so that its distance measurement value Ls indicates the difference between the set distance G of the head gap and the actual distance Le. Therefore, the distance measurement value Ls is displayed on the head gap display unit HG. Alternatively, as the distance index value, the value of the distance Le between the ink ejection head 622 and the work WK may be displayed. In this way, during teaching, if a distance index value indicating the distance Le between the ink ejection head 622 and the work WK is displayed on the control device, it is possible to set the teaching point while checking whether the head gap has an appropriate value. However, the display of the distance index value may be omitted.

[0034] Note that in step S12, the positions of the respective teaching points may not be set such that the head gap becomes equal to the set distance G, and the positions of the respective teaching points may be temporarily set. In this case, the positions of the respective teaching points are corrected in the following steps S13 and S14.

[0035] In step S13, the teaching processing unit 311 operates the robot arm 120 to traverse a plurality of teaching points, and acquires the results of distance measurement at the plurality of teaching points. In this step S13, the movable stage 612 is at the position during teaching shown in FIGS. 3 and 4, and distance measurement using the distance measuring device 630 is performed.

[0036] In step S14, the teaching processing unit 311 corrects the positions of the respective teaching points using the results of distance measurement. Specifically, as described with reference to FIG. 4, the position of the teaching point is corrected such that the distance Le from the ink ejection device 620 to the workpiece WK calculated according to the distance measurement value Ls from the distance measurement device 630 to the workpiece WK becomes equal to the set distance G suitable for the robot operation. Thus, by correcting a plurality of temporarily set teaching points, the distance between the ink ejection device 620 and the workpiece WK during the robot operation can be adjusted to the desired set distance G. The correction of the teaching points in step S14 may be gradually performed while repeatedly executing the operation of traversing a plurality of teaching points a plurality of times. That is, while slightly correcting the position of the teaching point by one operation, the distance between the ink ejection device 620 and the workpiece WK during the robot operation may finally be made equal to the desired set distance G.

[0037] Note that, when the distance from the distance measurement device 630 to the workpiece WK is set to an appropriate value in step S12, steps S13 and S14 can be omitted.

[0038] When the teaching process is completed, the process proceeds to step S15 in FIG. 5, and the robot operation execution unit 312 positions the movable stage 612 at the second position for the robot operation. As a result, as shown in FIG. 3, the ink ejection device 620 is positioned at the working position for performing printing on the workpiece WK.

[0039] In step S16, the robot operation execution unit 312 executes the robot operation. In the present embodiment, printing is performed on the surface of the workpiece WK. When executing the printing, as described with reference to FIG. 3, the ink ejection device 620 is positioned at the working position for ejecting ink onto the workpiece WK. Also, during the robot operation, it is preferable that the ink ejection device 620 is fixed at the working position without moving the movable stage 612, and the operation of the robot arm 120 and the printing by the ink ejection device 620 are performed.

[0040] As described above, during teaching execution, the movable stage 612 is set to the first position, thereby positioning the distance measuring device 630 at a distance measuring position for measuring the distance to the workpiece WK. Also, during robot work execution, the movable stage 612 is set to a second position different from the first position, thereby positioning the ink ejection device 620 as an end effector at a work position for performing robot work on the workpiece WK. Therefore, teaching can be accurately performed while accurately measuring the distance. Also, teaching can be executed while moving the robot arm 120 along the same trajectory as the movement trajectory of the robot arm 120 during robot work.

[0041] · Other forms: The present disclosure is not limited to the above-described embodiments, and can be realized in various forms without departing from the gist thereof. For example, the present disclosure can also be realized by the following aspects. The technical features in the above-described embodiments corresponding to the technical features in each of the following aspects can be appropriately replaced or combined in order to solve some or all of the problems of the present disclosure, or to achieve some or all of the effects of the present disclosure. Also, if the technical feature is not described as essential in this specification, it can be appropriately deleted.

[0042] (1) According to a first aspect of the present disclosure, a method for controlling a robot is provided. The method includes: (a) positioning a distance measuring device installed on a movable stage installed at a tip of a robot arm at a distance measuring position for measuring a distance to a workpiece by setting the movable stage to a first position; (b) performing distance measurement by the distance measuring device and executing teaching using the result of the distance measurement while the movable stage is set to the first position; (c) positioning an end effector installed on the movable stage at a working position for performing a robot operation on the workpiece by setting the movable stage to a second position different from the first position; and (d) executing the robot operation on the workpiece while the movable stage is set to the second position. According to this method, teaching can be accurately performed while accurately measuring the distance. Further, teaching can be executed while moving the robot arm along the same trajectory as the movement trajectory of the robot arm during the robot operation.

[0043] (2) In the above method, when the direction in which the end effector faces the workpiece when performing the robot operation is defined as the reference direction of the end effector, the movable stage may be configured to move in a direction perpendicular to the reference direction of the end effector. According to this method, the distance measuring position of the distance measuring device during teaching and the working position of the end effector during execution of the robot operation can be set at appropriate positions, respectively.

[0044] (3) In the above method, the position of the teaching point set in the teaching may be determined such that the distance from the end effector to the workpiece during the robot operation, which is calculated according to the measured value of the distance from the distance measuring device to the workpiece, is equal to a set distance suitable for the robot operation. According to this method, teaching can be executed such that the distance between the end effector and the workpiece during the robot operation becomes a desired set distance.

[0045] (4) In the above method, the step (b) may include: (b1) a step of temporarily setting a plurality of teaching points; (b2) a step of operating the robot arm so as to trace the plurality of teaching points and obtaining the results of the distance measurement by the distance measuring device at the positions of the plurality of teaching points; and (b3) a step of correcting the positions of the respective teaching points so that the distance during the robot operation from the end effector to the workpiece at each teaching point is equal to the set distance, using the results of the distance measurement at the plurality of teaching points. According to this method, by correcting the temporarily set plurality of teaching points, the distance between the end effector and the workpiece during robot operation can be adjusted to a desired set distance.

[0046] (5) In the above method, the end effector may include an ink ejection head, and the robot operation may be a process of performing printing on a printing area including a curved surface portion of the surface of the workpiece using the ink ejection head. According to this method, direct-to-shape printing can be accurately performed.

[0047] (6) In the above method, the movable stage may be driven by a piezoelectric actuator. According to this method, the movable stage can be moved without generating large vibrations in the end effector.

[0048] (7) According to a second aspect of the present disclosure, a robot system is provided. This robot system includes a robot including a robot arm, a movable stage installed at the tip of the robot arm, a distance measuring device installed on the movable stage, an end effector installed on the movable stage, and a control device. The control device is configured to execute: (a) a process of positioning the distance measuring device at a distance measuring position for measuring the distance to a workpiece by setting the movable stage to a first position; (b) a process of performing distance measurement by the distance measuring device and executing teaching using the result of the distance measurement while the movable stage is set to the first position; (c) a process of positioning the end effector at a work position for performing robot work on the workpiece by setting the movable stage to a second position different from the first position; and (d) a process of executing the robot work on the workpiece while the movable stage is set to the second position.

[0049] The present disclosure can also be realized in various other forms. For example, it can be realized in the form of a robot system including a robot and a robot control device, a computer program for realizing the functions of the robot control device, a non-transitory storage medium recording the computer program, and the like.

Description of Reference Numerals

[0050] 10…Robot system, 100…Robot, 110…Base, 120…Robot arm, 122…Tip, 200…Robot controller, 300…Information processing device, 310…Processor, 311…Teaching processing unit, 312…Robot work execution unit, 320…Memory, 330…Interface circuit, 340…Input device, 350…Display device, 400…Teaching pendant, 500…Mount, 610…Moving device, 612…Movable stage, 620…Ink ejection device, 622…Ink ejection head, 630…Distance measuring device

Claims

1. A method for controlling a robot, comprising: (a) positioning a distance measuring device installed on a movable stage installed at a tip of a robot arm at a distance measuring position for measuring a distance to a workpiece by setting the movable stage installed at the tip of the robot arm to a first position; (b) performing distance measurement by the distance measuring device and executing teaching using the result of the distance measurement while the movable stage is set to the first position; (c) positioning an end effector installed on the movable stage at a working position for performing a robot operation on the workpiece by setting the movable stage to a second position different from the first position; (d) executing the robot operation on the workpiece while the movable stage is set to the second position. A method comprising the above steps.

2. The method according to claim 1, wherein when a direction in which the end effector faces the workpiece when performing the robot operation is defined as a reference direction of the end effector, the movable stage is configured to move in a direction perpendicular to the reference direction of the end effector.

3. The method according to claim 1, wherein a position of a teaching point set in the teaching is determined such that a distance from the end effector to the workpiece during the robot operation, which is calculated according to a measured value of the distance from the distance measuring device to the workpiece, is equal to a set distance suitable for the robot operation.

4. The method according to claim 3, wherein step (b) includes: (b1) provisionally setting a plurality of teaching points; (b2) operating the robot arm to traverse the plurality of teaching points and obtaining results of the distance measurement by the distance measuring device at positions of the plurality of teaching points; (b3) correcting positions of the respective teaching points using the results of the distance measurement at the plurality of teaching points so that the distance from the end effector to the workpiece during the robot operation at each teaching point is equal to the set distance. A method including the above steps.

5. The method according to claim 1, wherein the end effector includes an ink ejection head, and the robot operation is a process of performing printing on a printing area including a curved surface portion of a surface of the workpiece using the ink ejection head.

6. The method according to claim 1, wherein the movable stage is driven by a piezoelectric actuator, the method.

7. A robot system, comprising a robot including a robot arm, a movable stage installed at the tip of the robot arm, a distance measuring device installed on the movable stage, an end effector installed on the movable stage, a control device, wherein the control device is configured to perform (a) a process of positioning the distance measuring device at a distance measuring position for measuring the distance to the workpiece by setting the movable stage to a first position; (b) a process of performing distance measurement by the distance measuring device and executing teaching using the result of the distance measurement while the movable stage is set to the first position; (c) a process of positioning the end effector at a working position for performing robot work on the workpiece by setting the movable stage to a second position different from the first position; (d) a process of executing the robot work on the workpiece while the movable stage is set to the second position. A robot system configured as described above. ​

Images