JP2024098591A - Robot control method and robot system - Google Patents

Abstract

To provide a robot control method and a robot system capable of more surely detecting the attitude of an object and accurately carrying out work for the object.SOLUTION: The control method of a robot equipped with a work tool for carrying out work on an object comprises: a detection step of detecting the attitude of the object using image data and gravity-center data of the object; and a work step of controlling driving of the robot on the basis of the attitude of the object detected in the detection step and carrying out the work on the object. The work tool is an ink jet head, and the work is printing work on the object. The gravity-center data is acquired by using a force sensor.SELECTED DRAWING: Figure 6

Description

The present invention relates to a robot control method and a robot system.

Patent Document 1 describes a painting system that uses a robot equipped with a print head that sprays paint to paint vehicle body parts. In addition, in this type of painting system, a camera captures images of the robot and the vehicle body part, and detects the relative positions of the robot and the vehicle body part based on the images obtained.

Special Publication No. 2020-501892

However, when the relative positional relationship between the robot and the vehicle body part is detected based on images captured by a camera, as in the painting system of Patent Document 1, there is a risk that detection accuracy will decrease or detection errors will occur due to insufficient or excessive exposure of the camera, focus issues, color variations, color unevenness, etc.

A method for controlling a robot according to the present invention is a method for controlling a robot equipped with a work tool that performs work on an object, the method comprising the steps of:
a detection step of detecting a posture of the object using image data and center of gravity data of the object;
and a task step of controlling the drive of the robot based on the posture of the object detected in the detection step, and performing the task on the object.

The robot system of the present invention includes: a robot having a work tool that performs work on an object;
an imaging device for imaging the object;
a center-of-gravity position detection device on which the object is placed and which detects the center-of-gravity position of the object;
The robot has a control device that detects the posture of the object based on image data of the object acquired by the imaging device and the center of gravity position of the object detected by the center of gravity position detection device, and controls the operation of the robot based on the detection result.

FIG. 1 is a configuration diagram of a robot system according to a preferred embodiment. FIG. 2 is a plan view of the center-of-gravity position detection device as viewed from above. FIG. 13 is a plan view of a modified example of the center-of-gravity position detection device as viewed from above. FIG. 13 is a plan view of a modified example of the center-of-gravity position detection device as viewed from above. FIG. 2 is a diagram showing the configuration of a control device. 1 is a flowchart showing a method for controlling a robot.

The robot control method and robot system of the present invention will be described in detail below based on the embodiments shown in the attached drawings.

Figure 1 is a configuration diagram of a robot system according to a preferred embodiment. Figure 2 is a plan view of a center-of-gravity position detection device as viewed from above. Figure 3 is a plan view of a modified center-of-gravity position detection device as viewed from above. Figure 4 is a plan view of a modified center-of-gravity position detection device as viewed from above. Figure 5 is a configuration diagram showing the configuration of a control device. Figure 6 is a flowchart showing a method of controlling a robot.

The robot system 1 shown in FIG. 1 is a system that performs DTS (Direct To Shape) printing work, which prints print data such as desired characters, patterns, illustrations, etc. on a printing surface set on the surface of an object W. Such a robot system 1 has a center of gravity position detection device 2 that detects the position of the center of gravity G of the placed object W (hereinafter also referred to as the "center of gravity position"), a camera 3 as an imaging device that images the object W on the center of gravity position detection device 2, a robot 4 that performs printing work on the object W, and a control device 5 that detects the posture of the object W on the center of gravity position detection device 2 based on information obtained from the center of gravity position detection device 2 and the camera 3, and controls the operation of the robot 4 based on the detection result. Calibration of the center of gravity position detection device 2, the camera 3, and the robot 4 has already been performed, and the position of the object W in the image data captured by the camera 3 and the center of gravity position of the object W detected by the center of gravity position detection device 2 can be specified in the robot coordinate system set in the robot 4.

[Robot 4]
The robot 4 is a six-axis vertical articulated robot having six drive shafts. The robot 4 has a base 41 fixed to the floor surface, a robot arm 42 rotatably connected to the base 41, and a work tool 43 attached to the tip of the robot arm 42. The robot arm 42 has six arms 421, 422, 423, 424, 425, 426 rotatably connected to each other, and has six joints J1, J2, J3, J4, J5, and J6. Of these six joints J1 to J6, the joints J2, J3, and J5 are bending joints, and the joints J1, J4, and J6 are torsion joints. The work tool 43 is an inkjet head 431 for printing print data on the object W. Thus, in the robot system 1 of this embodiment, the work tool is the inkjet head 431, and the work performed on the object W is the printing work. This results in a robot system 1 specialized for printing work.

Although the robot 4 has been described above, the configuration of the robot 4 is not particularly limited. For example, it may be a SCARA robot, a dual-arm robot equipped with two of the above-mentioned robot arms 42, or the like. It may also be a self-propelled robot to which the base 41 is not fixed. The work performed on the target object W is also not particularly limited, and may be work other than printing work. The work tool is also not particularly limited, and can be changed as appropriate depending on the work content.

[Center of gravity position detection device 2]
The center-of-gravity position detection device 2 has an upper surface serving as a placement surface 20 on which an object W is placed. The center-of-gravity position detection device 2 detects the center of gravity of the object W placed on the placement surface 20, more specifically, the X-axis coordinate and the Y-axis coordinate of the center of gravity position in the robot coordinate system. As shown in Fig. 2, the center-of-gravity position detection device 2 of this embodiment is a force sensor 21. This allows the center of gravity of the object W to be detected with high accuracy.

In particular, the force sensor 21 is a six-axis force sensor capable of detecting six-axis components of an external force applied to the force sensor 21. The six-axis components consist of translational force (shear force) components in the X-axis, Y-axis, and Z-axis directions, and rotational force (moment) components around these three axes. The force sensor 21 has four piezoelectric devices 22 arranged at equal intervals (90° intervals) around a central axis, and a case that houses these piezoelectric devices 22. Each piezoelectric device 22 has a piezoelectric body such as a quartz element, and can extract the received force as an electrical detection signal by utilizing the piezoelectric effect of the piezoelectric body.

The force sensor 21 detects the six-axis components of the external force applied from the object W on the placement surface 20 by processing the detection signals output from each piezoelectric device 22. Then, it detects the center of gravity position of the object W based on each component. Note that it is not necessary to use all six-axis components to detect the center of gravity position. For example, the center of gravity position can be detected by using the rotational force component in the X-axis direction and the rotational force component in the Y-axis direction out of the six-axis components. Note that hereinafter, the center of gravity position detected by the center of gravity position detection device 2 is also referred to as "center of gravity data."

The center-of-gravity position detection device 2 has been described above, but the configuration of the center-of-gravity position detection device 2 is not particularly limited as long as it can acquire center-of-gravity data of the object W. For example, the center-of-gravity position detection device 2 shown in FIG. 3 has three pressure-sensitive sensors 25 arranged at equal intervals (120° intervals) around the central axis, and a mounting table 24 placed on the pressure-sensitive sensors 25, the upper surface of which is the mounting surface 20. The pressure-sensitive sensors 25 have a characteristic that their resistance value changes depending on the pressure received. Therefore, the center-of-gravity position detection device 2 can detect the center-of-gravity position of the object W on the mounting surface 20 using the resistance value of each pressure-sensitive sensor 25. The center-of-gravity position detection device 2 configured in this way can also detect the center-of-gravity position of the object W with high accuracy. The number and arrangement of the pressure-sensitive sensors 25 are not particularly limited.

For example, the center-of-gravity position detection device 2 shown in FIG. 4 has three load cells 26 arranged at equal intervals (120° intervals) around the central axis, and a mounting table 24 placed on the load cells 26, with the upper surface being the mounting surface 20. The load cells 26 can measure the load received. Therefore, the center-of-gravity position detection device 2 can detect the center-of-gravity position of the object W on the mounting surface 20 using the loads measured by each load cell 26. The center-of-gravity position detection device 2 configured in this way can also detect the center-of-gravity position of the object W with high accuracy. Note that the number and arrangement of the load cells 26 are not particularly limited.

[Camera 3]
1, the camera 3 is located directly above the center-of-gravity position detection device 2, and captures an image of the object W placed on the center-of-gravity position detection device 2 from directly above. However, the location of the camera 3 is not particularly limited as long as it can capture an image of the object W on the center-of-gravity position detection device 2. For example, the camera 3 may be located on the robot 4.

[Control device 5]
The control device 5 is, for example, configured from a computer, and has a processor (CPU) for processing information, a memory communicatively connected to the processor, and an external interface for connecting to an external device. Various programs executable by the processor are stored in the memory, and the processor can read and execute the programs stored in the memory.

The control device 5 detects the posture of the object W on the center of gravity detection device 2 based on the center of gravity position of the object W detected by the center of gravity position detection device 2 and the image data acquired by the camera 3, and prints the print data on the object W by controlling the driving of the robot 4 based on the detected posture. As shown in FIG. 5, such a control device 5 has a print data storage unit 51 that stores the print data, a shape data storage unit 52 that stores shape data of the object W, a posture detection unit 53 that detects the posture of the object W, a print data correction unit 54 that aligns the print data with the object W and corrects the print data, and a robot control unit 55 that controls the driving of the robot 4.

The print data storage unit 51 stores print data to be printed on the printing surface of the object W. The shape data storage unit 52 stores shape data of the object W. The shape data is, for example, 3D CAD (Computer Aided Design) data of the object W. The shape data also includes the center of gravity position of the object W. In this way, by using CAD data as shape data and comparing this CAD data with image data acquired by the camera 3 as described below, the posture of the object W can be easily and accurately detected. However, the shape data is not particularly limited. For example, scan data obtained by 3D scanning the object W using a 3D scanner or the like may be used. Even if such scan data is used, the posture of the object W can be easily and accurately detected by comparing this scan data with image data acquired by the camera 3, as with CAD data.

The attitude detection unit 53 detects the attitude of the object W on the center-of-gravity position detection device 2 based on information obtained from the center-of-gravity position detection device 2 and the camera 3. This method will be described in detail below.

First, the center of gravity position detection device 2 detects the center of gravity of the object W placed on the placement surface 20. The method for detecting the center of gravity is as described above, and it can be detected from the rotational force component in the X-axis direction and the rotational force component in the Y-axis direction. The object W placed on the placement surface 20 is imaged by the camera 3 to obtain image data including the object W. Next, the posture detection unit 53 detects the posture of the object W by comparing the object W in the image data acquired by the camera 3 with the shape data of the object W stored in the shape data storage unit 52. Here, the object W in the image data may become unclear due to insufficient or excessive exposure of the camera 3, focus deviation, color variation, color unevenness, etc. Then, by comparing the unclear image data with the shape data, there is a risk of problems such as a decrease in detection accuracy of the posture of the object W, detection mistakes, and detection errors. Such problems lead to a decrease in printing accuracy and an increase in downtime.

Therefore, the posture detection unit 53 further uses the center of gravity data of the object W detected by the center of gravity position detection device 2 to suppress problems such as a decrease in detection accuracy, detection errors, and detection errors. For example, first, the posture detection unit 53 identifies multiple postures in which the center of gravity position of the object W coincides with the actual center of gravity position based on the shape data. Next, the posture detection unit 53 compares the identified multiple postures with the object W in the image data to detect the posture of the object W. According to this method, since the comparison target can be narrowed down in advance by the center of gravity position, the possibility of accurately detecting the posture of the object W even if the object W in the image data is unclear is increased. In this way, by using the center of gravity position of the object W to detect the posture of the object W, specifically, by detecting the posture of the object W based on the comparison result between the shape data and the center of gravity data and the comparison result between the shape data and the image data, the possibility of accurately detecting the posture of the object W is increased, and printing work can be performed with high accuracy. In addition, downtime due to detection errors and detection errors can be reduced, and printing work can be performed efficiently.

However, the method of detecting the posture of the object W is not particularly limited as long as it uses the image data acquired by the camera 3 and the center of gravity data acquired by the center of gravity position detection device 2. In addition, for example, a determination unit that determines whether the image data is sufficiently clear may be provided, and if the image data is clear, the posture of the object W may be detected using only the image data, and if the image data is unclear, the posture of the object W may be detected using the image data and the center of gravity data.

The print data correction unit 54 positions the print data relative to the print surface of the object W according to the posture of the object W detected by the posture detection unit 53. The print data correction unit 54 also corrects the print data based on the shape of the print surface so that the print data is printed neatly on the print surface of the object W. Specifically, because the print data is two-dimensional data, if the print surface is curved or bent three-dimensionally, the print data will be distorted or extend beyond the print surface if it is printed as is on the print surface. Therefore, the print data correction unit 54 corrects the print data so that the print data is printed neatly on the three-dimensional print surface.

The robot control unit 55 controls the driving of the robot 4 to print the print data corrected by the print data correction unit 54 on the printing surface of the object W.

The robot system 1 has been described above. Next, the control method of the robot 4, i.e., the printing work using the robot 4, will be described based on the flowchart shown in FIG. 6. The control method of the robot 4 includes a detection step S1 in which the posture of the object W is detected using image data and center of gravity data of the object W, and a work step S2 in which the driving of the robot 4 is controlled based on the posture of the object W detected in the detection step S1, and a printing work is performed on the object W.

[Detection step S1]
In the detection step S1, first, in step S11, the object W is placed on the placement surface 20 of the center-of-gravity position detection device 2. This step may be performed by an operator or by another robot system. Next, in step S12, the control device 5 acquires print data to be printed on the print surface of the object W from a host computer (not shown) or the like, and stores the acquired print data in the print data storage unit 51. Next, in step S13, the control device 5 acquires shape data of the object W from a host computer (not shown) or the like, and stores the acquired shape data in the shape data storage unit 52. The order of steps S11, S12, and S13 is not limited.

Next, in step S14, the camera 3 captures an image of the object W on the center of gravity position detection device 2. Next, in step S15, the control device 5 acquires the image data obtained in step S14 from the camera 3. Next, in step S16, the center of gravity position detection device 2 detects the center of gravity position of the object W to obtain center of gravity data. Next, in step S17, the control device 5 acquires the center of gravity data obtained in step S16 from the center of gravity position detection device 2. Next, in step S18, the control device 5 detects the posture of the object W on the center of gravity position detection device 2 using the image data and center of gravity data, for example, as described above. Note that the order of steps S14, S15, S16, and S17 is not limited.

[Work step S2]
In the work step S2, first, in step S21, the control device 5 performs positioning of the printing surface of the object W and the printing data based on the posture of the object W detected in step S18, and corrects the printing data as necessary. The correction contents are as described above. Next, in step S22, the drive of the robot 4 is controlled based on the positioning and correction performed in step S21, and the printing data is printed on the printing surface of the object W.

Next, in step S23, the control device 5 checks whether the object W has another printing surface. If it does not, the printing operation is terminated. Conversely, if it does have another printing surface, in step S24, it is determined whether printing on the other printing surface is possible without changing the posture of the object W. If printing is possible, the process returns to step S21, and printing is performed on the other printing surface. On the other hand, if printing is not possible, the process changes the posture of the object W on the center of gravity position detection device 2 in step S25. The method of changing the posture is not particularly limited, and may be performed by a worker or another robot system, for example. Then, the process returns to step S14, and printing on the other printing surface is started.

According to the above-described control method for the robot 4, the posture of the target object W is detected using center of gravity data in addition to shape data, making it difficult for mistakes or detection errors to occur in detecting the posture of the target object W. This increases the likelihood that the posture of the target object W can be detected accurately, and printing work on the target object W can be performed with high accuracy. In addition, downtime due to detection mistakes and detection errors can be reduced, allowing printing work to be performed efficiently.

The above describes the control method for the robot 4 and the robot system 1. As described above, the control method for the robot 4 is a control method for the robot 4 equipped with the work tool 43 that performs work on the object W, and includes a detection step S1 in which the posture of the object W is detected using image data and center of gravity data of the object W, and a work step S2 in which the robot 4 is driven and the work is performed on the object W based on the posture of the object W detected in the detection step S1. According to this method, the posture of the object W is detected using center of gravity data in addition to shape data, so that posture detection errors and detection errors of the object W are unlikely to occur. Therefore, the possibility of accurately detecting the posture of the object W is increased, and printing work on the object W can be performed accurately. In addition, downtime due to detection errors and detection errors can be reduced, and printing work can be performed efficiently.

As described above, the work tool 43 is an inkjet head 431, and the work is printing on an object W. This makes the robot 4 specialized for printing work.

As mentioned above, the center of gravity data is acquired using the force sensor 21. This allows the center of gravity data to be detected with high accuracy.

As described above, the center of gravity data may be obtained using the pressure sensor 25. This allows the center of gravity data to be detected with high accuracy.

As described above, the image data is acquired by capturing an image of the object W with the camera 3. This makes it easy to acquire the image data.

As described above, the system has shape data that contains information about the shape and center of gravity of the object W, and in the detection step S1, the posture of the object W is detected based on the results of comparing the shape data with the center of gravity data and the results of comparing the shape data with the image data. This makes it possible to easily and accurately detect the posture of the object W.

As mentioned above, the shape data is CAD data. This allows the orientation of the target object W to be identified easily and accurately.

As mentioned above, the shape data may be data obtained by 3D scanning the object W. This makes it possible to easily and accurately identify the posture of the object W.

As described above, the robot system 1 includes a robot 4 equipped with a work tool 43 that performs work on the object W, a camera 3 as an imaging device that images the object W, a center of gravity position detection device 2 on which the object W is placed and that detects the center of gravity of the object W, and a control device 5 that detects the posture of the object W based on the image data of the object W acquired by the camera 3 and the center of gravity position of the object W detected by the center of gravity position detection device 2, and controls the operation of the robot 4 based on the detection result. With this configuration, the posture of the object W is detected using center of gravity data in addition to shape data, so that posture detection errors and detection errors of the object W are unlikely to occur. Therefore, the possibility of accurately detecting the posture of the object W is increased, and printing work on the object W can be performed accurately. In addition, downtime due to detection errors and detection errors can be reduced, and printing work can be performed efficiently.

The robot control method and robot system of the present invention have been described above based on the illustrated embodiment, but the present invention is not limited to this. The configuration of each part can be replaced with any configuration having a similar function. In addition, any other components or any other processes may be added to the present invention.

1...Robot system, 2...Center of gravity position detection device, 20...Placement surface, 21...Force sensor, 22...Piezoelectric device, 24...Placement base, 25...Pressure sensor, 26...Load cell, 3...Camera, 4...Robot, 41...Base, 42...Robot arm, 421...Arm, 422...Arm, 423...Arm, 424...Arm, 425...Arm, 426...Arm, 43...Work tool, 431...Inkjet head, 5...Control device, 51...Print data storage unit, 52...Shape data storage unit, 53...Posture momentum detection unit, 54...print data correction unit, 55...robot control unit, G...center of gravity, J1...joint, J2...joint, J3...joint, J4...joint, J5...joint, J6...joint, S1...detection step, S11...step, S12...step, S13...step, S14...step, S15...step, S16...step, S17...step, S18...step, S2...work step, S21...step, S22...step, S23...step, S24...step, S25...step, W...object

Claims (9)

A method for controlling a robot equipped with a work tool that performs work on an object, comprising the steps of:
a detection step of detecting a posture of the object using image data and center of gravity data of the object;
a task step of controlling the drive of the robot based on the posture of the object detected in the detection step, and performing the task on the object. the working tool is an inkjet head,
The robot control method according to claim 1 , wherein the task is a printing task on the object. The method for controlling a robot according to claim 1 or 2, in which the center of gravity data is acquired using a force sensor. The robot control method according to claim 1 or 2, in which the center of gravity data is acquired using a pressure sensor. The method for controlling a robot according to claim 1 or 2, wherein the image data is acquired by capturing an image of the object with a camera. shape data having information about the shape and center of gravity of the object;
3. The robot control method according to claim 1, wherein in the detection step, a posture of the object is detected based on a comparison result between the shape data and the center of gravity data and a comparison result between the shape data and the image data. The robot control method according to claim 6, wherein the shape data is CAD data. The robot control method according to claim 6, wherein the shape data is data obtained by 3D scanning the object. A robot having a work tool for performing work on an object;
an imaging device for imaging the object;
a center-of-gravity position detection device on which the object is placed and which detects the center-of-gravity position of the object;
a control device that detects the posture of the object based on image data of the object acquired by the imaging device and the center of gravity position of the object detected by the center of gravity position detection device, and controls the drive of the robot based on the detection result.

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