Error compensation method for mechanical arm

Abstract

The invention discloses an error compensation method of a mechanical arm. The error compensation method comprises the following steps: arranging a first mechanical arm and a second mechanical arm, arranging an external sensing device, and arranging a first reference feature and a second reference feature; controlling the first mechanical arm to move a relative distance relative to the first reference feature to obtain a first relative position; and controlling the second mechanical arm to move the relative distance relative to the first reference feature to obtain a second relative position. And acquiring the difference between the first relative position and the second relative position by using the external sensing device, thereby acquiring first compensation data to compensate the error of the second mechanical arm relative to the second reference feature.

Description

Technical Field

[0001] The present invention relates to an error compensation method, and in particular to a method for reducing the error compensation of an external image device. Background Art

[0002] To correct the motion errors of different robotic arms in different spaces, an external camera is generally used to capture the differences in the motion points of the two robotic arms. However, the field of view of the external camera is limited and it cannot correct the differences in the motion points between different robotic arms in multiple different areas. For example, two robotic arms can have different motion postures and operate in multiple different areas, and the operating postures and areas are beyond the range of a single external camera. Figure 1 The schematic diagram of correcting the position of wafer boxes by using multiple external imaging devices is shown in the figure. The field of view 40 and 41 of the two external imaging devices 30 and 31 can only capture part of the area around the reference feature 10. For example, the external imaging device 30 can only capture wafer boxes 1 and 3 in the area above the reference feature 10, while the external imaging device 31 can only capture wafer boxes 2 and 4 in the area below the reference feature 10. In this way, when correcting the difference between the two robotic arms, relying on a single camera cannot capture the difference in the movement points of the two robotic arms. Figure 2 A schematic diagram of conventional methods for correcting motion points using multiple external imaging devices. If the positions of the four wafer cassettes 1-4 are changed to four motion points 21, 22, 23, and 24, the conventional method cannot rely on a single camera to correct for the discrepancies in motion points caused by mechanical errors between the two robotic arms. Therefore, multiple external cameras are typically added based on the motion areas to be corrected, making the point correction process between multiple robotic arms complex and costly.

[0003] In view of the above problems, the present invention proposes an error compensation method for a robotic arm to reduce the number of external imaging devices required. Summary of the Invention

[0004] An object of the present invention is to provide an error compensation method that reduces the number of external image devices required when correcting the difference or offset of motion points.

[0005] To achieve the aforementioned objectives, the present invention provides a method for compensating for an error in a robotic arm, comprising providing a first robotic arm and a second robotic arm, an external sensing device, and a first reference feature and a second reference feature. The first robotic arm is controlled to move a relative distance relative to the first reference feature to obtain a first relative position. The second robotic arm is controlled to move the relative distance relative to the first reference feature to obtain a second relative position. Furthermore, the external sensing device is used to obtain a difference between the first and second relative positions to obtain first compensation data to compensate for the error of the second robotic arm relative to the second reference feature.

[0006] Alternatively, a method for compensating for an error in a robotic arm according to the present invention includes providing a first robotic arm and a second robotic arm, an external sensing device, and a first reference feature. The first robotic arm is controlled to move a relative distance relative to the first reference feature to obtain a first relative position. The second robotic arm is controlled to move the relative distance relative to the first reference feature to obtain a second relative position. Furthermore, the external sensing device is used to obtain a difference between the first and second relative positions to obtain first compensation data to compensate for the error of the second robotic arm relative to the first reference feature.

[0007] A second reference feature is provided. The first robotic arm is controlled to move relative to the second reference feature by a relative distance to obtain a third relative position. The second robotic arm is controlled to move relative to the second reference feature by a relative distance to obtain a fourth relative position. An external sensing device is used to obtain a difference between the third relative position and the fourth relative position to obtain second compensation data to compensate for errors in different positions of the second robotic arm relative to the first reference feature. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 Schematic diagram of correcting the wafer box grabbing point for known multiple external imaging devices;

[0009] Figure 2 A schematic diagram of correcting motion points for known multiple external imaging devices;

[0010] Figure 3 A schematic diagram of compensating for the difference in the center points of two robotic arms according to the present invention;

[0011] Figure 4 A schematic diagram of a first embodiment of the present invention applied to correcting the position of a wafer box being grabbed;

[0012] Figure 5 A schematic diagram of a second embodiment of the present invention applied to correcting the position of a wafer cassette when gripping;

[0013] Figure 6 This is a schematic diagram of correcting the first motion point of the present invention;

[0014] Figure 7 This is a schematic diagram of correcting the second motion point according to the present invention;

[0015] Figure 8 A schematic diagram of correcting the third motion point according to the present invention; and

[0016] Figure 9 This is a schematic diagram of correcting the fourth motion point according to the present invention.

[0017]

Explanation of symbols

[0018] 1 wafer box

[0019] 2 wafer boxes

[0020] 3 wafer boxes

[0021] 4 wafer boxes

[0022] 10 Reference Features

[0023] 11 First reference feature

[0024] 12 Second reference feature

[0025] 13Third reference feature

[0026] 14 Fourth reference feature

[0027] 21 First Movement Point

[0028] 22 Second movement point

[0029] 23 The third movement point

[0030] 24 Fourth Movement Point

[0031] 30 External imaging device

[0032] 31 External imaging device

[0033] 32 external sensing devices

[0034] 40 vision range

[0035] 41 Field of View

[0036] 42 Extraction range

[0037] 51 First Robotic Arm

[0038] 52 base

[0039] 53 Second Robotic Arm

[0040] 54 base

[0041] 61 First Image Device

[0042] 62 Second image device

[0043] A0 first relative position

[0044] A1 sports position

[0045] A2 sports position

[0046] A3 sports position

[0047] A4 sports position

[0048] B0 second relative position

[0049] B1 sports position

[0050] B2 sports position

[0051] B3 sports position

[0052] B4 movement position

[0053] A00 first relative position

[0054] B11 Second relative position

[0055] B12 Third relative position

[0056] B13 Fourth relative position

[0057] B14 Fifth relative position

[0058] sq square area

[0059] sq0 center point

[0060] sq1 vertex

[0061] sq2 vertex

[0062] sq3 vertex

[0063] sq4 vertex DETAILED DESCRIPTION

[0064] The technical means and effects adopted by the present invention to achieve the above-mentioned objects are now described below with reference to embodiments and accompanying drawings.

[0065] See also Figure 3-4 , which is a schematic diagram of the present invention for compensating for the center point difference between two robotic arms, and a schematic diagram of a first embodiment of the present invention applied to correcting the position of a wafer cassette. The error compensation method includes providing a first robotic arm 51 and a second robotic arm 53, an external sensing device 32, and a first reference feature 11. If there are four wafer cassettes, a second reference feature 12, a third reference feature 13, and a fourth reference feature 14 are additionally provided. The first robotic arm 51 is controlled to move a relative distance relative to the first reference feature 11 to obtain a first relative position A0. The second robotic arm 53 is controlled to move the relative distance relative to the first reference feature 11 to obtain a second relative position B0. Furthermore, the external sensing device 32 is used to obtain the difference between the first relative position A0 and the second relative position B0, thereby generating first compensation data. In this way, the first compensation data can compensate for the difference in the center points of the first and second robotic arms 51, 53. This center point can be a tool center point (TCP) attached to each robotic arm.

[0066] The relative distance in the embodiment varies with the distance of the point to be corrected relative to the reference feature. Figure 3 The distance between the center point (such as A0) of the first robotic arm 51 and the first reference feature 11 is used as the relative distance, so that the second robotic arm 53 can move at the same relative distance, and the difference between the center point (such as B0) of the second robotic arm 53 and the center point of the first robotic arm 51 is obtained. Furthermore, a first imaging device 61 is set on the first robotic arm 51, and a second imaging device 62 is set on the second robotic arm 53. The first robotic arm 51 and the second robotic arm 53 respectively drive the first imaging device 61 and the second imaging device 62 to locate the first reference feature 11, the second reference feature 12, the third reference feature 13 and the fourth reference feature 14, so that the first robotic arm 51 and the second robotic arm 53 can move relative to the four reference features 11 to 14. In addition, due to the consideration of the drawing space, Figure 3 Only the first robotic arm 51 is shown. Figure 4 Only the second robotic arm 53 is shown, however, Figures 3-4 In the technical implementation process of the present invention, there will be a first robotic arm 51 and a second robotic arm 53. Among them, the first robotic arm 51 and the second robotic arm 53 each have a base 52, 54 to fix the position of the first robotic arm 51 and the second robotic arm 53.

[0067] See also Figure 3 , the external sensing device 32 includes an extraction range 42. The first reference feature 11 is set at a first position with reference to the position of the extraction range 42, the second reference feature 12 is set at a second position with reference to the position of the extraction range 42, and the third reference feature 13 is set at a third position with reference to the position of the extraction range 42, and the fourth reference feature 14 is set at a fourth position with reference to the extraction range 42. The first position, the second position, the third position, and the fourth position are located outside the extraction range 42 and enclose a square area sq, and are the four vertex positions of the square area sq, namely sq1, sq2, sq3, and sq4. In addition, in the embodiment, a center point sq0 of the square area sq is the position of the first relative position A0, so the relative distance can be the distance from the first reference feature 11 to the center point sq0. Furthermore, because the four reference features 11-14 enclose a square area sq, the distance from the second reference feature 12 to the center point sq0, the distance from the third reference feature 13 to the center point sq0, and the distance from the fourth reference feature 14 to the center point sq0 are equal to the distance from the first reference feature 11 to the center point sq0, and can all be considered relative distances. Furthermore, the reference feature can be a black and white checkerboard or other appropriate reference object, all of which are optional.

[0068] Furthermore, in addition to being set at four positions based on the extraction range 42, the first reference feature 11, the second reference feature 12, the third reference feature 13, and the fourth reference feature 14 can also be set at the first position, the second position, the third position, and the fourth position based on the position of the point to be corrected by the robotic arms 51 and 53, or can be set based on both the extraction range 42 and the position of the point to be corrected. All of these are embodiments. Figures 4 to 9 The various graphics in the figure are for auxiliary explanation and can be replaced with other different graphics, which is not limited to the embodiment.

[0069] See also Figure 1 When using a robotic arm to grab four wafer boxes, it is assumed that the positions of the four wafer boxes 1 to 4 are Figure 2 The positions of the first motion point 21, the second motion point 22, the third motion point 23, and the fourth motion point 24 are known. Therefore, if the conventional method is used, two external imaging devices 30 and 31 and a reference feature 10 must be set up to correct the four motion points 21, 22, 23, and 24 of the robot arm so that the four wafer boxes 1 to 4 can be properly grasped. In contrast, the error compensation method of the present invention changes the positions of the four wafer boxes 1 to 4, i.e., the positions of the four motion points 21, 22, 23, and 24, to the four reference features 11, 12, 13, and 14; Figure 2 The position of reference feature 10 is changed to the area for the robot arm to move, such as Figure 3 However, the number of reference features can vary depending on the number of objects being grasped, so the area in which the robot arm moves is not limited to a square. In other words, the embodiment does not limit the four reference features 11, 12, 13, and 14 to enclosing a square area sq. In other words, the reference features can enclose an area other than a square area.

[0070] See also Figure 4 , the present invention can use a single external sensing device 32 to extract the relevant point information of the four motion points 21, 22, 23, and 24 for correction. In addition, the first imaging device 61 and the second imaging device 62 can be a camera or a video camera, and the external sensing device 32 can be an infrared sensing device, or the external sensing device 32 can be replaced by an external imaging device which can also be a camera or a video camera, etc. Assuming Figure 2 The four moving points 21, 22, 23, and 24 are at the same distance from the reference feature 10. Figure 4The error compensation method of the present invention is described as follows: the same relative distance is set relative to four reference features 11, 12, 13, and 14. In other words, after setting up a first robot arm 51 and a second robot arm 53, setting up an external sensing device 32, and setting up first reference feature 11, second reference feature 12, third reference feature 13, and fourth reference feature 14, the first robot arm 51 is controlled to move a relative distance relative to first reference feature 11 to obtain a first relative position A00 (different symbols are used in different embodiments), the second robot arm 53 is controlled to move the same relative distance relative to first reference feature 11 to obtain a second relative position B11, the second robot arm 53 is controlled to move a relative distance relative to second reference feature 12 to obtain a third relative position B12, the second robot arm 53 is controlled to move a relative distance relative to third reference feature 13 to obtain a fourth relative position B13, and the second robot arm 52 is controlled to move a relative distance relative to fourth reference feature 14 to obtain a fifth relative position B14.

[0071] Next, the external sensing device 32 is used to obtain the difference between the first relative position A00 and the second relative position B11, and first compensation data (the first data or only one data item may be referred to as the first compensation data) is calculated to compensate for the motion error of the second robot arm 53 relative to the fourth reference feature 14. The external sensing device 32 is used to obtain the difference between the center point (i.e., A00) and the third relative position B12, and second compensation data is calculated to compensate for the motion error of the second robot arm 53 relative to the third reference feature 13. The external sensing device 32 is used to obtain the difference between the center point and the fourth relative position B13, and third compensation data is calculated to compensate for the motion error of the second robot arm 53 relative to the second reference feature 12. Finally, the external sensing device 32 is used to obtain the difference between the center point and the fifth relative position B14, and fourth compensation data is calculated to compensate for the motion error of the second robot arm 53 relative to the first reference feature 11.

[0072] In accordance with the above, the present invention Figure 4 The four reference features 11, 12, 13, and 14 replace Figure 2 The four movement points 21, 22, 23, 24, which replace Figure 1The positions of the four wafer boxes 1 to 4 are determined by the position of the second robot arm 53. Therefore, when compensating for the motion error of the second robot arm 53 relative to the fourth reference feature 14, the grasping error of the second robot arm 53 relative to the wafer box 4 in the lower left corner is compensated. Similarly, when compensating for the motion error of the second robot arm 53 relative to the third reference feature 13, the grasping error of the second robot arm 53 relative to the wafer box 3 in the upper left corner is compensated. When compensating for the motion error of the second robot arm 53 relative to the second reference feature 12, the grasping error of the second robot arm 53 relative to the wafer box 2 in the lower right corner is compensated. When compensating for the motion error of the second robot arm 53 relative to the first reference feature 11, the grasping error of the second robot arm 53 relative to the wafer box 1 in the upper right corner is compensated. Therefore, the error compensation method of the present invention can reduce the setting of external imaging devices when correcting the offset of the motion point.

[0073] In addition, the first, second, third, and fourth in the description are only used to describe different objects, and do not limit the position or arrangement order of the objects. Figure 4 If the positions of the reference features are changed to the first reference feature 11 on the upper right, the second reference feature 12 on the lower left, the third reference feature 13 on the upper left, and the fourth reference feature 14 on the lower right, the description of the compensation will be in the order of claims 1 and 6 in the claims. In other words, the embodiment does not limit the compensation order of the error compensation method. Furthermore, when there are only two wafer cassettes, Figure 4 The number of reference features can be changed to two. Figure 5 , which is a schematic diagram of a second embodiment of the present invention applied to correcting the position of a wafer cassette. The second robotic arm 53 is controlled to move a relative distance relative to the first reference feature 11 to obtain a second relative position B11. The second robotic arm 53 is controlled to move a relative distance relative to the second reference feature 12 to obtain a third relative position B12. Furthermore, the external sensing device 32 is used to obtain the difference between the first relative position (i.e., A00) and the second relative position B11, and the difference between the first relative position (i.e., A00) and the third relative position B13, to obtain second compensation data and third compensation data to compensate for the error of the second robotic arm 53 relative to the second reference feature 12 and the first reference feature 11.

[0074] Apart from Figure 3 Correction of the tool center point of the robot arm, Figures 4-5 Correcting the grasping point of the object, the error compensation method of the present invention can also be used to correct the points of two robotic arms in different spaces. Figure 5Assume that a point to be corrected (assuming the first motion point 21) of the second robotic arm 53 is located on a first side of the second reference feature 12, and the first reference feature 11 is located on a second side of the point to be corrected. The first robotic arm 51 is controlled to move a relative distance relative to the first reference feature 11 to obtain a first relative position (assuming A00), and the second robotic arm 53 is controlled to move a relative distance relative to the first reference feature 11 to obtain a second relative position (assuming B11). Thus, the difference between the first relative position (assuming A00) and the second relative position (assuming B11) is obtained using the external sensing device 32 to generate first compensation data to compensate for the error of the point to be corrected (assuming the first motion point 21) of the second robotic arm 53 relative to the second reference feature 12. In other words, the present invention eliminates the need for an additional external sensing device at the motion point 21 to compensate for the error between the first and second robotic arms 51, 53 at the motion point 21 relative to the second reference feature 12. Further explanation follows.

[0075] like Figure 6 , which is a schematic diagram of the present invention correcting the first motion point. The point to be corrected is not necessarily the center point of the robot arm, it may be other motion points. For example, Figure 2 The first motion point 21 of the present invention is controlled by the first robotic arm 51 to move a preset distance relative to the fourth reference feature 14 to obtain a motion position A1. The second robotic arm 53 is controlled to move the preset distance relative to the fourth reference feature 14 to obtain a motion position B1. The external sensing device 32 is then used to extract the difference between the motion position A1 and the motion position B1, that is, to obtain the error of different positions relative to the reference feature 10 (or the first reference feature 11). For example, Figure 3 After the error (difference between A0 and B0) relative to the first reference feature 11 is obtained, it is the ninth item; Figure 6 The embodiment obtains the errors (differences between A1 and B1 ) at different positions relative to the first reference feature 11 , which is claim 10 .

[0076] Similarly, if Figure 7 , which is a schematic diagram of the present invention correcting the second motion point. After controlling the first robotic arm 51 and the second robotic arm 53 to move relative to the third reference feature 13, the difference between the motion position A2 and the motion position B2 can be obtained, that is, the error relative to other positions of the reference feature 10 (such as the second motion point 22) can be obtained. Figure 8, which is a schematic diagram of the present invention correcting the third motion point. After controlling the first robotic arm 51 and the second robotic arm 53 to move relative to the second reference feature 12, the difference between the motion position A3 and the motion position B3 can be obtained, that is, the error relative to other positions of the reference feature 10 (such as the third motion point 23) can be obtained. Figure 9 , which is a schematic diagram of the present invention correcting the fourth motion point. After controlling the first robotic arm 51 and the second robotic arm 53 to move relative to the first reference feature 11, the difference between the motion position A4 and the motion position B4 can be obtained, that is, the error relative to other positions of the reference feature 10 (such as the fourth motion point 24) can be obtained.

[0077] Therefore, by exchanging the concept of general motion point positions with reference feature positions, the motion point positions in four different spaces around the reference feature are converted to positions within a confined space. In this way, the error compensation method of the present invention can reduce the need for external imaging devices when correcting the differences in motion point positions. Figure 3 The size of the square area sq is determined by the sensing capabilities (or imaging range, or imaging capability) of the external sensor device (or external imaging device). Therefore, given the same specifications of the external device (i.e., sensor device or imaging device), the error compensation method of the present invention can significantly reduce the cost of the external device and increase the spatial range and number of points that can be corrected.

[0078] In summary, the present invention provides a method for compensating for an error in a robotic arm, including providing a first robotic arm and a second robotic arm, an external sensing device, and a first reference feature and a second reference feature. The first robotic arm is controlled to move a relative distance relative to the first reference feature to obtain a first relative position. The second robotic arm is controlled to move the relative distance relative to the first reference feature to obtain a second relative position. Furthermore, the external sensing device is used to obtain a difference between the first and second relative positions to generate first compensation data to compensate for the error of the second robotic arm relative to the second reference feature.

[0079] The above description is only for the convenience of illustrating the embodiments of the present invention. The scope of the present invention is not limited to the embodiments. Any changes made according to the present invention without departing from the spirit of the present invention shall fall within the scope of the patent application of the present invention.

Claims

1. A method for compensating an error of a robotic arm, comprising: Setting a first robotic arm and a second robotic arm; Setting up an external sensing device; Setting a first reference feature and a second reference feature; Controlling the first robotic arm to move a relative distance relative to the first reference feature to obtain a first relative position; and Controlling the second robotic arm to move the relative distance relative to the first reference feature to obtain a second relative position; The external sensing device is used to obtain a difference between the first relative position and the second relative position to obtain first compensation data to compensate for an error of the second robot arm relative to the second reference feature.

2. The error compensation method for a robotic arm according to claim 1, wherein: The point to be corrected of the second robotic arm is located on a first side of the second reference feature; the first reference feature is located on a second side of the second reference feature relative to the point to be corrected; the first robotic arm is controlled to move the relative distance relative to the first reference feature to obtain the first relative position; the second robotic arm is controlled to move the relative distance relative to the first reference feature to obtain the second relative position; and the external sensing device is used to obtain the difference between the first relative position and the second relative position to obtain the first compensation data to compensate for the error of the point to be corrected of the second robotic arm relative to the second reference feature.

3. The error compensation method for a robotic arm according to claim 2, wherein: The first reference feature, the second reference feature, the third reference feature and the fourth reference feature are respectively set at a first position, a second position, a third position and a fourth position according to the position of the point to be calibrated by the robot arm.

4. The error compensation method for a robotic arm according to claim 3, wherein: The second robotic arm is controlled to move the relative distance relative to the second reference feature to obtain a third relative position; the second robotic arm is controlled to move the relative distance relative to the third reference feature to obtain a fourth relative position; and the second robotic arm is controlled to move the relative distance relative to the fourth reference feature to obtain a fifth relative position.

5. The error compensation method for a robotic arm according to claim 3, wherein: The center of an area enclosed by the first position, the second position, the third position, and the fourth position includes a center point, and the relative distance is the distance from the first reference feature to the center point.

6. The error compensation method for a robotic arm according to claim 5, wherein: The external sensing device is used to obtain a difference between the center point and the third relative position, and second compensation data is calculated to compensate for the motion error of the second robot arm relative to the first reference feature; the external sensing device is used to obtain a difference between the center point and the fourth relative position, and third compensation data is calculated to compensate for the motion error of the second robot arm relative to the fourth reference feature; and the external sensing device is used to obtain a difference between the center point and the fifth relative position, and fourth compensation data is calculated to compensate for the motion error of the second robot arm relative to the third reference feature.

7. The error compensation method of a robotic arm according to claim 6, comprising: Disposing a first imaging device on the first robotic arm; and Disposing a second imaging device on the second robotic arm; in, The first imaging device and the second imaging device locate the first reference feature, the second reference feature, the third reference feature, and the fourth reference feature.

8. The error compensation method for a robotic arm according to claim 6, wherein: Positions of the first reference feature, the second reference feature, the third reference feature, and the fourth reference feature are set according to the extraction range of the external sensing device.

9. A method for compensating an error of a robotic arm, comprising: Setting a first robotic arm and a second robotic arm; Setting up an external sensing device; Set the first reference feature; Controlling the first robotic arm to move a relative distance relative to the first reference feature to obtain a first relative position; and Controlling the second robotic arm to move the relative distance relative to the first reference feature to obtain a second relative position; The external sensing device is used to obtain a difference between the first relative position and the second relative position, thereby obtaining first compensation data to compensate for an error of the second robot arm relative to the first reference feature.

10. The error compensation method of a robotic arm as claimed in claim 9, comprising: Set the second reference feature; Controlling the first robotic arm to move the relative distance relative to the second reference feature to obtain a third relative position; controlling the second robotic arm to move the relative distance relative to the second reference feature to obtain a fourth relative position; The external sensing device is used to obtain a difference between the third relative position and the fourth relative position to obtain second compensation data to compensate for errors of the second robot arm at different positions relative to the first reference feature.

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