Mechanical arm and correction method thereof

Abstract

The invention provides a mechanical arm and a correction method thereof, a positioning device is applied to the mechanical arm, an asymmetric pattern is arranged on one side of a body of the positioning device, the mechanical arm moves the positioning device to a plurality of positions, a photographing device of a control system obtains a plurality of images of the asymmetric pattern, and the images are displayed on the positioning device. A control circuit of the control system obtains a center position of the positioning device according to a plurality of images, and the control system corrects a tool center point of the mechanical arm according to the center position to complete correction.

Description

Technical Field

[0001] The present invention relates to a mechanical arm and a calibration method thereof, and in particular to a method for calibrating the mechanical arm by using a positioning device. Background Art

[0002] With the advancement of industrial technology, the proportion of automation in factories has gradually increased, and many mechanical systems have emerged, among which robotic arms play a very important role.

[0003] Among the conventional calibration methods for robotic arms, there is a method that uses the principles and equipment of a laser tracker, which includes installing a laser interferometer on a tracking station that can rotate longitude and latitude angles. The laser light passes through the scanning mirror at the center of the dual-axis rotation on the tracking station and is directed to a target reflector on the robotic arm, and then reflected back along the original optical path. When the robotic arm moves, the reflected light spot also moves relatively. By using an optical position sensor, the direction of movement of the light spot can be detected, and the servo motor of the dual-axis rotation mechanism can be immediately driven to rotate the scanning mirror, thereby keeping the laser beam always tracking the spatial position of the target reflector. Ultimately, by measuring the radial position of the laser and the angle of the dual axis, the spatial position of the target reflector can be determined, but this method requires a long time for correction, and the equipment manufacturing precision requirements are high, which further leads to an increase in the process cost of using this correction method. Therefore, the industry and academia need a correction method with shorter correction time and lower cost.

[0004] In view of the above problems of the conventional technology, the present invention provides a robotic arm and a calibration method thereof, wherein a positioning device is applied to the robotic arm, and a plurality of images of the positioning device are used to calibrate the robotic arm. Summary of the invention

[0005] An object of the present invention is to provide a robot arm and a calibration method thereof, wherein a positioning device is applied to the robot arm so that the robot arm can automatically correct the tool center point (TCP) value and axial information.

[0006] In order to achieve the above-mentioned purposes and effects, the present invention provides a calibration method for a robotic arm, the steps of which include: locking one side of a locking accessory of a positioning device to a first tool of a robotic arm, setting an asymmetric pattern on one side of a body of the positioning device, the robotic arm moves the positioning device to a first position, a control system controls a photographic device to capture a first image of the asymmetric pattern, the robotic arm moves the positioning device to a second position, the control system controls the photographic device to capture a second image of the asymmetric pattern, the control system obtains a center position of the positioning device based on the first image and a second image, and the control system calibrates the robotic arm based on the center position, thereby quickly calibrating the tool center point of the robotic arm.

[0007] In order to achieve the above-mentioned purposes and effects, the present invention provides a calibration method for a robotic arm, the steps of which include: using a second tool of a robotic arm to clamp two sides of a grabbing member of a positioning device, an asymmetric pattern is set on one side of a body of the positioning device, the robotic arm moves the positioning device to a first position, a control system controls a photographic device to obtain a first image of the asymmetric pattern, the robotic arm moves the positioning device to a second position, the control system controls the photographic device to obtain a second image of the asymmetric pattern, the control system obtains a center position of the positioning device based on the first image and a second image, and calibrates the robotic arm based on the center position, thereby calibrating the tool center point of the robotic arm.

[0008] The present invention provides a calibration method for a robotic arm, the steps of which include: using a third tool of a robotic arm to adsorb one side of a body of a positioning device, setting an asymmetric pattern on the other side of the body, the robotic arm moves the positioning device to a first position, a control system controls a photographic device to obtain a first image of the asymmetric pattern, the robotic arm moves the positioning device to a second position, the control system controls the photographic device to obtain a second image of the asymmetric pattern, the control system obtains a center position of the positioning device based on the first image and a second image, and the control system calibrates the robotic arm based on the center position, thereby calibrating the tool center point of the robotic arm.

[0009] In one embodiment of the present invention, the other side of the locking accessory of the positioning device is connected to the other side of the body, a limiting hole is provided on one side of the locking accessory, and the first tool is inserted into the limiting hole to fix the locking accessory.

[0010] In one embodiment of the present invention, the other side of the locking component of the positioning device is connected to the other side of the body.

[0011] In one embodiment of the present invention, the photographic device captures the asymmetric pattern to obtain the first image and the second image, the control system is electrically connected to the photographic device and the robotic arm, the control system receives the first image and the second image, and a control circuit of the control system transmits a modified control signal to the robotic arm.

[0012] In an embodiment of the present invention, the center position of the positioning device corresponds to a tool center position of the first tool.

[0013] In an embodiment of the present invention, the center position of the positioning device corresponds to a tool center position of the second tool.

[0014] In an embodiment of the present invention, the center position of the positioning device corresponds to a tool center position of the third tool.

[0015] In one embodiment of the present invention, when the asymmetric pattern is cut in any axial direction, the cut parts are all different. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 :It is a calibration flow chart of the first embodiment of the present invention; FIG. 2A to FIG. 2B : It is a schematic diagram of the installation of the first embodiment of the present invention; FIG. 3A to FIG. 3B : It is a schematic diagram of the correction control of the first embodiment of the present invention; Figure 4 :It is a circuit diagram of an embodiment of the present invention; Figure 5 : It is a schematic structural diagram of a lock accessory according to a first embodiment of the present invention; Figure 6 :It is a calibration flow chart of the second embodiment of the present invention; Figure 7 : It is a schematic diagram of a clamping and positioning device according to a second embodiment of the present invention; Figure 8 : It is a schematic diagram of a grabbing member according to a second embodiment of the present invention; Fig. 9 :It is a calibration flow chart of the third embodiment of the present invention; and FIG. 10A to FIG. 10B : It is a schematic diagram of a suction positioning device according to the third embodiment of the present invention. Fig.11 : It is a schematic diagram of a positioning device according to an embodiment of the present invention.

Figure number comparison

[0017] In order to further understand and appreciate the structural features and effects of the present invention, a preferred embodiment and detailed description are provided as follows:

[0018] In view of the above-mentioned problems of conventional technology, the present invention is a calibration method for a robotic arm, which utilizes a positioning device with an asymmetric pattern to be installed on the tool end of the robotic arm. The robotic arm moves the positioning device to multiple positions, and uses a photographic device to photograph the asymmetric pattern of the positioning device, so as to utilize the multiple images of the asymmetric pattern to calibrate the robotic arm, thereby solving the problem that conventional robotic arm calibration is time-consuming and causes an increase in process costs.

[0019] See also Figure 1 , which is a calibration flow chart of the first embodiment of the present invention. As shown in the figure, this embodiment is a calibration method for a robotic arm, and the steps include:

[0020] Step S02: locking one side of the locking attachment of the positioning device to the first tool of the robot arm, and setting an asymmetric pattern on one side of the body of the positioning device;

[0021] Step S04: the robot arm moves the positioning device to a first position, and the control system controls the photographing device to obtain a first image of the asymmetric pattern;

[0022] Step S06: the robot arm moves the positioning device to a second position, and the control system controls the photographing device to obtain a second image of the asymmetric pattern;

[0023] Step S08: The control system obtains the center position of the positioning device according to the first image and the second image; and

[0024] Step S10: The control system calibrates the robot arm according to the center position.

[0025] See again Figure 1 See also Sections 2A to Figure 2B , FIG. 2A to FIG. 2B This is a schematic diagram of the installation of the first embodiment of the present invention. As shown in the figure, in this embodiment, a positioning device 10 includes a main body 12 and a locking accessory 14. An asymmetric pattern 122 is set on one side of the main body 12, wherein the asymmetric pattern 122 is similar to the shape of the English letter TM. However, the embodiment does not limit the shape of the asymmetric pattern 122. Other characters can also be designed as patterns for calibration, such as characters similar to OMRON. During calibration, the positioning device 10 is installed on a robotic arm 2. The installation referred to in the embodiment can be manually installing the positioning device 10 to the robotic arm 2; or the operator controls the robotic arm 2 so that the robotic arm 2 gradually approaches the positioning device 10 to combine the positioning device 10 with the robotic arm 2, wherein the operator's control can be manually changing the position of the robotic arm 2, or using a teach pendant (or controller) to change the position of the robotic arm 2. Furthermore, the installation method varies with the type of tool at the front end of the robotic arm 2 and the positioning device 10, such as Figure 2A The positioning device 10 can lock a columnar or needle-shaped tool, that is, after the first tool 3 is placed in the locking attachment 14 of the positioning device 10, the locking attachment 14 is rotated to lock the first tool 3, so as to combine the positioning device 10 with the robot arm 2. In addition, the locking attachment 14 can be a cylindrical or rectangular column in the embodiment; the tool in the embodiment can be a variety of tools, and the above are all optional matters.

[0026] In step S02 , firstly, one side of the locking attachment 14 of the positioning device 10 is locked to a first tool 3 of the robot arm 2 , so that the positioning device 10 is fixed to the first tool 3 . When the robot arm 2 moves, the first tool 3 drives the positioning device 10 to move.

[0027] Continuing from the above, in this embodiment, the first tool 3 can be a screwdriver, a hexagonal wrench, a drill bit or a welding gun head, so that the robot arm 2 can drive the first tool 3 to process the workpiece.

[0028] Continuing from the above, in this embodiment, the other side of the locking member 14 of the positioning device 10 is disposed on the other side of the main body 12 , so that the main body 12 and the locking member 14 are connected to each other.

[0029] See again Figures 1 to 2B , and see FIG. 3A to FIG. 3B as well as Figure 4 , FIG. 3A to FIG. 3B is a schematic diagram of the correction control of the first embodiment of the present invention, Figure 4 The circuit diagram of the first embodiment of the present invention is shown in the figure. In step 04, a control system 20 and a photographing device 22 are set. The photographing device 22 can be a camera or a video camera. The control system 20 includes a control circuit 24, and the control circuit 24 is electrically connected to the photographing device 22 and the robot arm 2. Before the calibration starts, the robot arm 2 can be moved to a detection position to detect whether the tool is offset. When the calibration starts, the robot arm 2 moves the positioning device 10 to a first position, that is, the robot arm 2 is first controlled to an initial calibration posture, so that the photographing device 22 obtains a first image P1 of the positioning device 10, that is, a first image P1 of the asymmetric pattern 122 of the positioning device 10 is captured.

[0030] See again Figures 1 to 4 As shown in the figure, in step 06, the robot arm 2 is controlled to move the positioning device 10 to a second position, and the camera 22 is used to capture a second image P2 of the positioning device 10, wherein the second position is different from the first position and can be a motion with different degrees of freedom (such as a single axial movement or rotation). In different embodiments, the robot arm 2 can be controlled to move the positioning device 10 to a plurality of positions, and the camera 22 can be used to obtain a corresponding number of images. The embodiment does not limit the number of the plurality of images, for example, a computing circuit 26 is used to compute the image data of 2, 3, 4 or up to 15 positioning devices 10.

[0031] See again Figure 1 as well as Figure 4In step 08, the control system 20 receives the data of the first image P1 and the second image P2 from the photographic device 22, and the control circuit 24 performs calculations based on the pattern difference between the first image P1 and the second image P2 to obtain a center position of the positioning device 10. For example, in the embodiment, the positioning device 10 includes an asymmetric pattern 122, so a calculation circuit 26 of the control circuit 24 can calculate the center position of the positioning device 10 based on the first image P1 and the second image P2. In different embodiments, the calculation circuit 26 can be independently set from the control circuit 24, or the calculation circuit 26 is set in the control circuit 24. In this way, the control circuit 24 (or the calculation circuit 26) receives the 15 images output by the photographic device 22, and the control circuit 24 (or the calculation circuit 26) calculates based on the pattern difference of the 15 images to further obtain a more accurate center position of the positioning device 10.

[0032] Continuing from the above, the asymmetric pattern 122 is a planar feature that is asymmetric in both vertical and horizontal directions, and can define the center position, X, Y and Z axes of the positioning device 10. Thus, the control system 20 can calibrate the robot arm 2 with the first image P1 and a second image P2 at different positions.

[0033] Continuing from the above, after the asymmetric pattern 122 is cut in any axial direction, the cut parts of the asymmetric pattern 122 are all different, so that the asymmetric pattern 122 forms self-asymmetry in any axial direction.

[0034] See again Figure 1 as well as Figure 4In step 10, after the control circuit 24 obtains the center position of the positioning device 10, the control circuit 24 of the control system 20 corrects the TCP value (i.e., the value of the tool center point) and the tool axial information stored in the control system 20 according to the center position, and then sends a control signal 242 to the robot arm 2, so that the robot arm 2 can correctly move the first tool 3 to different positions. In this way, after the positioning device 10 and the robot arm 2 are combined, the control system 20 and the robot arm 2 run a calibration program, and modify the old TCP value and tool axial information of the first tool 3 to the TCP value and tool axial information of the first tool 3 after the offset, and perform the task with the offset TCP value and tool axial information. In other words, the control system 20 originally controls the robot arm 2 according to the initial setting value (e.g., the initial tool center point, or the first tool center point) of the first tool 3, and after the first tool 3 is offset, it controls the robot arm 2 according to the offset setting value (e.g., the offset tool center point, or the second tool center point) of the first tool 3. Therefore, the robot arm 2 changes from moving according to the initial tool center point to moving according to the offset tool center point. The calibration procedure of the present invention can also be applied to embodiments where the first tool 3 is replaced with a different tool; and the robot arm 2 moves according to the offset tool center point, which should still be in an appropriate state or a state where the tool can still perform the task; in addition, the position of the initial tool center point is different from the position of the offset tool center point.

[0035] Continuing from the above, the center position of the positioning device 10 is installed (or combined) to correspond to a tool center position of the first tool 3, and the offset of the first tool 3 can be calculated by adding a plurality of different postures of the robot arm 2, so as to obtain an offset compensation value. In this way, the control system 20 modifies the initial TCP value and axial information of the first tool 3 according to the offset compensation value to the offset TCP value and axial information. In other words, the control system 20 modifies the movement of the robot arm 2 according to the center position of the positioning device 10, that is, outputs different (or modified) control signals 242 to control the movement of the robot arm 2.

[0036] See also Figure 5 , which is a schematic diagram of the locking accessory structure of the first embodiment of the present invention. As shown in the figure, in this embodiment, the other side of the locking accessory 14 of the positioning device 10 is arranged on the other side of the main body 12, and a limiting hole 142 is set on one side of the locking accessory 14. The first tool 3 of the robot arm 2 is inserted into the limiting hole 142 to fix the positioning device 10 (that is, the locking accessory). For example, the positioning device 10 is screwed to the first tool 3 by the limiting hole 142 with a thread.

[0037] Please refer to Figures 6-7, which are a calibration flow chart of the second embodiment of the present invention and a schematic diagram of the clamping and positioning device of the second embodiment of the present invention. As shown in the figure, the steps of the second embodiment include:

[0038] Step S22: clamping two sides of the gripping member of the positioning device with a second tool of the robot arm, and setting an asymmetric pattern on one side of the body of the positioning device;

[0039] Step S24: the robot arm moves the positioning device to the first position, and the control system controls the photographing device to obtain a first image of the positioning device;

[0040] Step S26: the robotic arm moves the positioning device to a second position, and the control system controls the photographing device to obtain a second image of the positioning device;

[0041] Step S28: The control circuit of the control system obtains the center position of the positioning device according to the first image and the second image; and

[0042] Step S30: calibrating the robot arm according to the center position of the positioning device.

[0043] See again Sections 3A to Figure 3B and Figures 6-7. As shown in the figure, the difference between this embodiment and the above-mentioned first embodiment is that a robotic arm 2 clamps a grabbing member 15 of a positioning device 11 with a second tool 4, and the positioning device 11 includes a main body 12 and the grabbing member 15. As in the above-mentioned first embodiment, an asymmetric pattern 122 is also provided on one side of the main body 12, and the positioning device 11 is installed on the robotic arm 2 during calibration. In step S22, the robotic arm 2 first clamps the two sides of the grabbing member 15 of the positioning device 11 with the second tool 4, so that the positioning device 11 is fixed to the second tool 4. When the robotic arm 2 moves the second tool 4, the second tool 4 drives the positioning device 11 to move. Steps S24 to S28 of this embodiment are similar to steps S04 to S08 of the above-mentioned first embodiment (Steps 3A to S28). Figure 3B ).

[0044] Continuing from the above, the second tool 4 of the robot arm 2 can be a gripper-type tool, such as a pneumatic gripper, a hydraulic gripper, and an electric gripper, which is not limited to the present embodiment.

[0045] Continuing from the above, in step S30 of this embodiment, after the control circuit 24 obtains the center position of the positioning device 10, the control circuit 24 compensates the relevant values ​​of the robot arm 2 according to the center position to complete the calibration. The remaining technical contents are as described in the above embodiment and will not be repeated here.

[0046] See also Figure 8: It is a schematic diagram of a grabbing member of the second embodiment of the present invention. As shown in the figure, the grabbing member 15 is a rectangular parallelepiped structure and is for the second tool 4 to grab. The grabbing member 15 can be other shapes, such as a circular body, a square body or other curved structures.

[0047] See also Fig. 9 , which is a calibration flow chart of the third embodiment of the present invention. As shown in the figure, a calibration method for a robotic arm includes the following steps:

[0048] Step S42: using a third tool of the robot arm to absorb one side of the body of the positioning device, and setting an asymmetric pattern on the other side of the body;

[0049] Step S44: the robot arm moves the positioning device to the first position, and the control system controls (or drives) the photographing device to obtain a first image of the positioning device (or the asymmetric pattern);

[0050] Step S46: the robot arm moves the positioning device to a second position, and the control system controls (or drives) the photographing device to obtain a second image of the positioning device (or the asymmetric pattern);

[0051] Step S48: The control circuit of the control system obtains the center position of the positioning device according to the first image and the second image; and

[0052] Step S50: The control circuit of the control system calibrates (or compensates) the relevant values ​​of the robot arm according to the center position.

[0053] See again Sections 3A to Figure 3B , Fig. 9 And see FIG. 10A to FIG. 10B , FIG. 10A to FIG. 10B Schematic diagram of the suction positioning device of the third embodiment of the present invention. As shown in the figure, the difference between this embodiment and the first embodiment is that a robot arm 2 uses a third tool 5 to absorb one side of a body 17 of a positioning device 13, and the positioning device 13 includes the body 17, and one side of the body 17 includes Fig.11A concentric circle 172 pattern is shown, but the positioning devices 10 and 11 of other embodiments do not need to include a concentric circle 172 pattern. As in the first embodiment described above, an asymmetric pattern 122 is set on the other side of the main body 17. During calibration, the operator picks up the center of the concentric circle 172 pattern of the positioning device 13 for the third tool 5 to adsorb and install it on the robot arm 2. In step S42, the robot arm 2 first adsorbs the main body 17 of the positioning device 13 with the third tool 5 so that the positioning device 13 is combined with the third tool 5. After that, the robot arm 2 starts the calibration procedure, that is, when the robot arm 2 moves the third tool 5, the third tool 5 drives the positioning device 13 to move. Steps S44 to S48 of this embodiment are similar to steps S04 to S08 of the first embodiment described above (steps 3A to S48 of the present embodiment are similar to steps S04 to S08 of the first embodiment described above (steps 3A to S42 of the present embodiment). Figure 3B ).

[0054] Continuing from the above, in step S50 of the present embodiment, after the control circuit 24 obtains the center position of the positioning device 13, the control circuit 24 of the control system 20 compensates the relevant values ​​or / and information of the robot arm 2 according to the center position to complete the calibration (or complete the compensation). That is, it is possible to compensate only the TCP value without compensating the data of the tool axis, or only compensate the data of the tool axis without compensating the TCP value, wherein the types of signals, values, data, information or messages are only used for technical description and are not intended to limit the content of the present invention. Furthermore, steps 04 to 10, steps 24 to 30 and steps 44 to 50 are the calibration procedures (also referred to as compensation procedures) of the robot arm 2, and the robot arm 2 automatically corrects (or automatically modifies, or automatically compensates) the TCP value or / and the information of the tool axis, and the operator does not need to intervene in the procedure.

[0055] Continuing from the above, the center position of the positioning device 13 corresponds to a tool center position of the third tool 5 , so that the relevant values ​​of the robot arm 2 can be modified through a calibration process (or compensation process).

[0056] In summary, the present invention provides a calibration method for a robotic arm, which is to correctly combine a specific position of a positioning device (such as a locking position, a grasping position, and an adsorption position) with the robotic arm, and move the positioning device to a plurality of positions so that a camera or a video camera can capture the positioning device itself or a pattern thereon, and then use the image difference of the pattern plus the arm posture to calibrate the robotic arm. In addition, it is also possible to correctly control the movement of the robotic arm without using the asymmetric pattern of the positioning device, such as using the surrounding boundaries of the positioning device to obtain an offset compensation value, that is, using the surrounding boundaries of the positioning device to obtain the center position of the positioning device, and modifying the calculation method, which is also a feasible design option. Among them, the aforementioned embodiment uses the center position as a technical description. If other positions of the positioning device (i.e., non-center positions) are used for calibration, it also belongs to the concept of the present invention. Therefore, the present invention solves the problem that the conventional calibration method requires a long time and the equipment required for calibration is more complex, resulting in increased costs.

[0057] The order of execution of each step in the above embodiment does not mean the order of execution. The order of execution of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment of the present application.

[0058] The above is only a preferred embodiment of the present invention and is not intended to limit the scope of the present invention. All equivalent changes and modifications to the shape, structure, characteristics and spirit described in the claims of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A calibration method for a robotic arm, characterized in that: The steps include: A tool for mounting a positioning device on a robot arm, the positioning device comprising an asymmetric pattern; The robot arm moves the positioning device to a first position, and a control system controls a photographing device to obtain a first image of the asymmetric pattern; The robot arm moves the positioning device to a second position, and the control system controls the photographic device to obtain a second image of the asymmetric pattern; The control system calculates a center position of the positioning device according to the first image and a second image; and The control system calibrates the mechanical arm according to the positioning device.

2. The method for calibrating a robot arm as claimed in claim 1, characterized in that: in, The tool includes a first tool, and the tool for installing the positioning device on the robotic arm includes the first tool for locking one side of a locking accessory of the positioning device to the robotic arm, and the asymmetric pattern is set on one side of a body of the positioning device; a control circuit of the control system obtains a center position of the positioning device based on the first image and the second image; and the control circuit of the control system calibrates the robotic arm based on the center position of the positioning device.

3. The method for calibrating a robot arm as claimed in claim 2, characterized in that: The other side of the locking accessory of the positioning device is arranged on the other side of the main body, and a limiting hole is arranged on one side of the locking accessory. The first tool is inserted into the limiting hole to fix the locking accessory.

4. The method for calibrating a robot arm as claimed in claim 1, characterized in that: in, The tool comprises a second tool, and the tool for installing the positioning device on the mechanical arm comprises clamping two sides of a grasping member of the positioning device with the second tool of the mechanical arm.

5. The method for calibrating a robot arm as claimed in claim 4, characterized in that: The other side of the grabbing member of the positioning device is arranged on the other side of the main body, and the asymmetric pattern is arranged on one side of the main body of the positioning device.

6. The method for calibrating a robot arm as claimed in claim 1, characterized in that: in, The tool includes a third tool, and the tool for installing the positioning device on the robot arm includes using the third tool of the robot arm to adsorb one side of a body of the positioning device, a concentric circle pattern is set on the one side of the body, and the asymmetric pattern is set on the other side of the body.

7. The method for calibrating a robot arm as claimed in claim 1, characterized in that: The photographic device captures the asymmetric pattern to obtain the first image and the second image. A control circuit of the control system is electrically connected to the photographic device and the robotic arm. The control circuit receives the first image and the second image, and transmits a modified control signal to the robotic arm.

8. The method for calibrating a robot arm as claimed in claim 1, characterized in that: The center position of the positioning device corresponds to a tool center position of the tool.

9. The method for calibrating a robot arm as claimed in claim 1, characterized in that: The asymmetric pattern is cut along any axis, and the cut parts are all different.

10. A robotic arm, characterized in that: It contains: a first tool center point, which is an initial tool center point of a tool; and a second tool center point, an offset tool center point of the tool relative to the first tool center point; Wherein, the robot arm moves according to the center point of the offset tool.

Images