TW201805129A - Calibration method for robot arm calibration system comprising a robot, a camera and a calibration member to define the coordinates and a rotation axis - Google Patents

Abstract

Provided is a calibration method for a robot arm calibration system, the robot arm calibration system includes a robot arm, a camera and a calibration member, the camera has a field of view, the calibration member has a calibration mark. The calibration method includes: controlling the robot arm to grab and move the calibration member, and driving the calibration mark of the calibration member to coincide with the reference mark within the field of view, and recording the coordinate of the robot arm as a first coordinate; controlling the robot arm to rotate to drive the calibration member for rotation by a predetermined angle in a calibration plane; controlling the movement of the robot arm to drive the calibration mark of the calibration member to coincide with the reference mark in the field of view, and recording the coordinate of the robot arm as a second coordinate; and according to the first coordinate and the second coordinate, the rotation axis of the robot arm on the calibration plane is calculated, so as to complete the calibration of the robot arm.

Description

Calibration method of robotic arm correction system

The invention relates to a calibration method; in particular, it relates to a calibration method for a robotic arm calibration system.

With the advancement of science and technology, the use of robotic arms to realize automated production and assembly processes has been commonly found in today's production lines. Among them, the mechanical coordinate system used to control the robotic arm is not the same as the image coordinate system of the image captured by the camera. Therefore, if you want to use the robotic arm for automated production and assembly, you need to adjust the mechanical coordinate system of the robotic arm and The image coordinates of the camera are appropriately converted, that is, the calibration of the robot arm.

Among them, please refer to FIG. 1 to introduce one of the common correction methods in the industry. The correction method is as follows: a correction point 1a is marked at the center of the gripper claw of the robot arm 1, and then the camera is moved in the field of view 2 of the camera The robotic arm 1 and three moving points 3a, 3b, and 3c corresponding to the correction points 1a of the robotic arm 1 in the image captured by the camera are respectively marked; then, these marked points 3a to 3c are further marked. The rotation axis of the robot arm 1 is calculated, so as to realize the correction of the robot arm.

However, when the robotic arm to be calibrated is relatively large, please refer to Figure 2. The field of view 4 restricted by the camera is limited, and the swing range of the robotic arm 5 cannot exceed the field of view 4 during calibration. When the robot arm 5 is calibrated, the amplitude of the robot arm 5 can be smaller, so that the rotation axis of the robot arm 5 calculated by the obtained marking points 6a to 6c will be relatively inaccurate, that is, the The actual axis of rotation of the robot arm 5 will cause considerable errors. Furthermore, when the robotic arm is relatively large, and it is intended to perform calibration with the conventional robotic arm calibration method, the robotic arm requires a large space for movement, which is not conducive to this calibration method in some narrow spaces. ongoing.

In other words, the conventional robotic arm calibration method still has many inconveniences and needs improvement.

In view of this, an object of the present invention is to provide a calibration method for a robotic arm calibration system, which can accurately and quickly calibrate a robotic arm.

In order to achieve the above-mentioned object, the present invention provides a calibration method for a robotic arm calibration system. The robotic arm calibration system includes a robotic arm, a camera, and a calibration member. The camera has a field of view and the calibration member has a Calibration mark; the calibration method includes the following steps: A. Control the robotic arm to grab the calibration piece; B. Control the robotic arm to move, move the calibration piece to the field of view of the camera, and make the calibration piece The calibration mark coincides with a reference mark in the field of view; C. Record the coordinate of the robot arm on the coordinate system of the robot arm in step B as a first coordinate; D. Control the rotation of the robot arm to drive the calibration part to Rotate a predetermined angle on a calibration plane; E. Control the movement of the robotic arm to move the calibration element to the field of view of the camera and make the calibration mark of the calibration element coincide with the reference mark in the field of vision; F In step E, the coordinate of the robot arm on the coordinate system of the robot arm is a second coordinate; G. According to the A second coordinate scale and calculates the rotation axis of the robot on the calibration plane.

The effect of the present invention is that by controlling the robotic arm to grasp the calibration part, aligning the calibration mark with the reference mark in the field of view, and controlling the robotic arm to rotate, to drive the calibration part to rotate on a calibration plane, and to drive the calibration part again The mark coincides with the reference mark, and the axis of rotation of the robot arm on the calibration plane can be obtained quickly and efficiently.

In order to explain the present invention more clearly, a preferred embodiment is described in detail below with reference to the drawings. Please refer to FIG. 3, which is a basic structural diagram of a robotic arm calibration system 100 to which a preferred embodiment of the present invention is applied. The robotic arm calibration system 100 includes a base 10, a robotic arm 20, a camera 30, a The calibration platform 40, a central control computer 50, and a calibration member 60 (see FIG. 4).

The robot arm 20 is a multi-axis, multi-joint robot arm. In this embodiment, a six-axis robot arm is taken as an example. The robot arm 20 has a first end 22 and a second end 24. The first end 22 The second end 24 is fixed to the base 10, and the second end 24 is a free end, and has a clamping jaw 26 (refer to FIG. 4) for grasping the workpiece. The robotic arm 20 is connected to the central control computer 50 by signal and / or electrical connection, and is controlled by the central control computer 50 to act according to a coordinate system of the robotic arm. Wherein, the coordinate system of the robot arm may be a coordinate system such as a rectangular coordinate type, a cylindrical coordinate type, a polar coordinate type, etc., and for convenience of explanation, in this embodiment, a rectangular robot coordinate system is taken as an example. In addition, in other practical implementations, the robot arm 20 is not limited to a six-axis robot arm, and may be a three-axis, a four-axis, or a robot arm other than a four-axis.

The camera 30 can be set on a carrier (not shown) and can be controlled to adjust its shooting angle and shooting range (or field of view). For example, in this embodiment, the camera 30 is signal-connected and / or electrically connected to the central control computer 50, and can be controlled by the central control computer 50 to adjust its shooting angle, or it can be adjusted The optical axis direction, for example, in this embodiment, the optical axis system of the camera 30 is perpendicular to a plane of the calibration platform 40 and is perpendicular to the plane, and the camera 30 photographs the plane and A field of view 32 is defined on this plane (as shown in Figure 4). In this embodiment, the plane of the correction platform 40 is parallel to the XY plane in the world coordinate system, and the optical axis of the camera 30 is parallel to the Z axis in the world coordinate system and perpendicular to the The XY plane is used to correct the rotation axis of the robot arm 20 about a rotation axis parallel to the Z axis, but in other embodiments, it is not limited to this.

The correction platform 40 is mainly used to provide a low-noise background for the camera 30 to shoot. In other practical implementations, the correction platform 40 is not a necessary constituent element for the implementation.

The central control computer 50 is mainly used to control the operation of the robot arm 20 and the camera 30, that is, to control the robot arm 20 to move in the world coordinate system according to the robot arm coordinate system, and to receive feedback signals from the robot arm 20 (For example, touch feedback, pressure feedback signals, etc.); and can receive images in the field of view 32 captured by the camera 30 for processing, for example, establish a corresponding camera image coordinate system based on the field of view 32.

Hereinafter, an embodiment of the calibration method of the robot arm system of the present invention will be described. Please refer to FIG. 4. First, step A: The central control computer 50 controls the gripper 26 of the robot arm 20 to grasp the calibration piece. 60. The calibration element 60 has a calibration mark 62 for calibration purposes. For example, in this embodiment, the calibration element 60 is a flat-shaped object as an example, and the calibration mark 62 is provided. On a plane of the correction member 60, the correction mark 62 is a circle, but in other embodiments, it is not limited to this. In addition, in this embodiment, the gripper 26 of the robotic arm 20 grasps an edge position of the calibration member 60 and is relatively far from the position of the calibration mark 62. As a result, the mechanism described above is used for calibration. The arm 20 is less likely to block the image capturing path of the camera 30, so as to avoid the situation where the camera 30 cannot effectively capture the correction mark 62 and the position of the correction mark 62 cannot be effectively identified.

Next, step B: control the robotic arm 20 to move, and drive the correction member 60 to move into the field of view 32 of the camera 30, and make the correction mark 62 of the correction member 60 and a reference mark 34 in the field of view 32 coincide. Wherein, the reference mark 34 refers to a mark for alignment and calibration of the correction mark 62 of the correction member 60, which can be freely selected by the user on the image coordinate system of the camera 30 through the central control computer 50, in other words The reference mark 34 may be a specific point or block on the field of view 32 or based on a specific coordinate on its image coordinate system.

In this embodiment, the reference mark 34 is located at a photographing center position of the field of view 32 of the camera 30, that is, near the optical axis passing of the camera 30, where the photographing center is marked with The advantage of the reference mark 34 is that the errors caused by the image captured by the camera 30 near the optical axis are the lowest, so that a more accurate correction result can be obtained. In addition, in an embodiment, in order to further improve the accuracy of the correction, in step B, the robot arm 20 can be further controlled to rotate so that the plane of the correction member 60 having the correction mark 62 and the plane of the camera 30 The optical axis is vertical, or the plane of the correction element 60 having the correction mark 62 is parallel to the plane of the field of view 32, so that the camera 30 can accurately and correctly capture the correction mark 62 and facilitate the correction mark 62. Alignment and re-cooperation with reference mark 34.

Next, after the calibration mark 62 and the reference mark 34 of the calibration member 60 are overlapped, step C is performed: In step B described above, the coordinate of the robot arm 20 on the coordinate system of the robot arm is a first coordinate. For example, in this embodiment, the coordinates of the robot arm 20 are captured by the central control computer 50 and recorded as the first coordinates (X ₁ , Y ₁ , Z ₁ , Rx ₁ , Ry ₁ , Rz ₁ ) (or called First token).

Next, step D is executed: the robot arm 20 is controlled to rotate, and the correction member 60 is driven to rotate a predetermined angle on a correction plane. For example, in this embodiment, the correction plane is determined according to the rotation axis of the robot arm 20, for example, in this embodiment, the Z axis rotation axis of the robot arm is adjusted. The correction is therefore based on the XY plane in the world coordinate system as an example. In addition, in this embodiment, preferably, the predetermined angle is selected as 180 degrees. As shown in FIG. 6, the robotic arm 20 is controlled to rotate and drives the correction member 60 to rotate 180 degrees on the calibration plane. At this time, the correction mark 62 of the correction member 60 is deviated from the reference mark 34.

Next, as shown in FIG. 7, execute step E: control the robotic arm 20 to move the correction member 60 to move within the field of view 32 of the camera 30, and make the correction mark 62 and the field of view 32 of the correction member 60. The reference mark 34 in is coincident.

Then, after the calibration mark 62 and the reference mark 34 of the calibration member 60 are overlapped, step F is performed: In step E described above, the coordinate of the robot arm 20 on the coordinate system of the robot arm is a second coordinate. For example, in this embodiment, the coordinates of the robot arm 20 are captured by the central control computer 50 and recorded as the second coordinates (X ₂ , Y ₂ , Z ₂ , Rx ₂ , Ry ₂ , Rz ₂ ) (or called Second coordinate value).

,

,

,

,

,

）。藉此，透過本發明之機械手臂係統的校正方法，便可快速且有效地找出機械手臂20於特定平面（如本實施例當中的XY平面）上進行旋轉的旋轉軸心，藉以完成機械手臂的校正。Finally, step G is performed: the rotation axis of the robot arm 20 on the calibration plane is calculated according to the first coordinate and the second coordinate. For example, in this embodiment, since the correction plane of the robotic arm 20 is an XY plane, and the rotation axis of the robotic arm 20 when rotating in step D is parallel to the Z axis, so the robotic arm 20 The coordinate system of the rotation axis rotating on the XY plane is the first coordinate (X ₁ , Y ₁ , Z ₁ , Rx ₁ , Ry ₁ , Rz ₁ ) and the second coordinate (X ₂ , Y ₂ , Z ₂ , Rx ₂ , Ry ₂ , Rz ₂ ) are collinear, and the coordinate system of the rotation axis is the midpoint between the first coordinate and the second coordinate. The rotation axis of the rotation axis is (

,

,

,

,

,

). Thereby, through the calibration method of the robot arm system of the present invention, the rotation axis center of the robot arm 20 rotating on a specific plane (such as the XY plane in this embodiment) can be quickly and efficiently found, thereby completing the robot arm. Correction.

It is worth mentioning that, in other practical implementations, if the axis of rotation of the robot arm 20 on other planes is to be rotated, for example, the robot arm 20 is rotated by a rotation axis parallel to the X (Y) axis For the axis correction, the optical axis of the camera 30 can be adjusted to be parallel to the X (Y) axis in the world coordinate system, and the plane of the adjustment and correction platform 40 can be parallel to the YZ (XZ) plane in the world coordinate system. The plane is corrected as the correction plane in the correction method of the present invention, and the rotation axis coordinates of the robot arm 20 rotating on the YZ (XZ) plane can also be obtained quickly and accurately. In addition, in the foregoing step of causing the correction member to rotate a predetermined angle on a correction plane, the predetermined angle is not limited to 180 degrees, and in one embodiment, it may also be 30 degrees, 60 degrees, or 90 degrees. The angle is used as the predetermined angle to correct the robot arm. In addition, when a predetermined angle other than 180 degrees is selected, the first and second coordinates can be regarded as the endpoint coordinates of the two bottom angles of an isosceles triangle, and the predetermined angle is the top angle of the isosceles triangle. (Inner angle of the vertex), so that after knowing the endpoint coordinates and apex angle of the two bottom corners of the isosceles triangle, the vertex coordinates of the isosceles triangle can be obtained, and the vertex coordinates are the parallel movement of the robot arm The axis of rotation of the plane of the isosceles triangle is coordinated.

It is also mentioned that the calibration method of the conventional robotic arm mostly uses the end point of the robotic arm (similar to the second end in this embodiment) as the calibration mark for the camera to shoot when the robotic arm moves and rotates. However, In the above method, when the robot arm rotates, the robot arm itself can easily block the calibration mark provided on itself, so that the camera cannot effectively identify and track the location of the calibration mark. In contrast, the correction method of the present invention uses a robotic arm to grab another correction piece provided with a correction mark. Therefore, the correction piece protrudes from the robotic arm in multiple directions and viewing angles, and is not easy to be grasped by the robotic arm. Therefore, during the correction, it is less likely that the camera cannot track and recognize the correction marks, and has the advantage of less restrictions on the correction conditions.

The above description is only the preferred and feasible embodiment of the present invention. The calibration method of the robotic arm system of the present invention is not limited to the calibration of the rotation axis of the robotic arm in the XY, YZ, and XZ planes. In practice, the equivalent changes in applying the description of the present invention and the scope of patent application should be included in the patent scope of the present invention.

1‧‧‧ robotic arm
1a‧‧‧correction point
2‧‧‧field of vision
3a, 3b, 3c‧‧‧‧marked points
4‧‧‧ field of view
5 robotic arm
6a, 6b, 6c ‧‧‧ marked points [the present invention]
100‧‧‧ Robotic Arm Calibration System
10‧‧‧ base
20‧‧‧ Robotic arm
22‧‧‧ the first end
24‧‧‧ the second end
26‧‧‧Jaw
30‧‧‧Camera
32‧‧‧field of vision
34‧‧‧Reference mark
40‧‧‧ Calibration platform
50‧‧‧ Central Control Computer
60‧‧‧correction
62‧‧‧correction mark

Figure 1 is a schematic diagram of a conventional calibration robot arm. Figure 2 is a schematic diagram of a conventional calibration robot arm. FIG. 3 is a structural diagram of a robotic arm correction system according to a preferred embodiment of the present invention. FIG. 4 to FIG. 7 are schematic diagrams of performing the calibration method of the foregoing preferred embodiment of the present invention.

34‧‧‧Reference mark

60‧‧‧correction

62‧‧‧correction mark

Claims (7)

A calibration method for a robotic arm calibration system. The robotic arm calibration system includes a robotic arm, a camera, and a calibration piece. The camera has a field of view and the calibration piece has a calibration mark. The calibration method includes the following steps: : A. Control the robotic arm to grab the correction piece; B. Control the robotic arm to move, move the correction piece to the field of view of the camera, and make the correction mark of the correction piece and a reference in the field of view The marks are coincident; C. The coordinate of the robot arm on the coordinate system of the robot arm in the recording step B is a first coordinate; D. Control the rotation of the robot arm to drive the calibration member to rotate a predetermined angle on a calibration plane; E Control the movement of the robot arm, drive the correction element to move into the field of view of the camera, and make the correction mark of the correction element coincide with the reference mark in the field of vision; F. Record step E. The coordinate on the arm coordinate system is a second coordinate; G. According to the first coordinate and the second coordinate, Calculate the axis of rotation of the robot arm on the calibration plane. The calibration method of the robotic arm calibration system according to claim 1, wherein the reference mark is located at a photographing center of a field of view of the camera. The calibration method of the robotic arm calibration system according to claim 1, wherein the calibration plane is perpendicular to the optical axis of the camera. The calibration method of the robotic arm calibration system according to claim 1, wherein the robotic arm grasps an edge position of the calibration member and is far away from a position of the calibration mark. The calibration method of the robotic arm calibration system according to claim 1, wherein the calibration member has a plane, and the calibration mark is disposed on the plane; in step B, it further includes controlling the robot arm to rotate so that the calibration member The plane is perpendicular to the optical axis of the camera. The calibration method of the robotic arm calibration system according to claim 1, wherein the predetermined angle is 180 degrees. The calibration method of the robotic arm calibration system according to claim 1, wherein in step G, a coordinate of a rotation axis of the robotic arm on the calibration plane is a midpoint between the first coordinate and the second coordinate.