阅读说明：本技术 机器手臂的坐标校正方法 (Coordinate correction method of robot arm ) 是由 邵启焕 张启舜 于 2020-06-11 设计创作，主要内容包括：本发明提供一种机器手臂的坐标校正方法,包含步骤：(a)在机器手臂于工作空间中运作时,依据移动命令控制机器手臂进行移动,并利用三维测量装置取得机器手臂所到达的参考定位点；(b)依据参考定位点取得参考坐标系；(c)机器手臂离开工作空间,而在机器手臂回到工作空间中运作时,依据移动命令控制机器手臂进行移动,并利用三维测量装置取得机器手臂所到达的实际定位点；(d)依据实际定位点取得实际坐标系,并依据参考坐标系及实际坐标系计算取得坐标补正信息；以及(e)依据坐标补正信息调整机器手臂,使机器手臂维持运作于参考坐标系。(The invention provides a coordinate correction method of a robot arm, which comprises the following steps: (a) when the robot arm operates in the working space, the robot arm is controlled to move according to the movement command, and a three-dimensional measuring device is used for obtaining a reference positioning point reached by the robot arm; (b) acquiring a reference coordinate system according to the reference positioning point; (c) the robot arm leaves the working space, and when the robot arm returns to the working space to operate, the robot arm is controlled to move according to the movement command, and the three-dimensional measuring device is used for obtaining an actual positioning point reached by the robot arm; (d) acquiring an actual coordinate system according to the actual positioning point, and calculating to acquire coordinate correction information according to the reference coordinate system and the actual coordinate system; and (e) adjusting the robot arm according to the coordinate correction information to keep the robot arm operating in the reference coordinate system.)

1. A coordinate calibration method of a robot arm, wherein the robot arm is arranged on a movable carrying platform and operates in at least one working space, a three-dimensional measuring device is arranged in the working space, and the three-dimensional measuring device is constructed for measuring the position of the robot arm, the coordinate calibration method comprises the following steps:

(a) when the robot arm is moved by the movable carrying platform to operate in the working space, the robot arm is controlled to move according to a movement command, and the three-dimensional measuring device is used for obtaining at least three reference positioning points reached by the robot arm;

(b) calculating to obtain a rotation matrix and a translation vector according to the at least three reference positioning points, and calculating to obtain a corresponding reference coordinate system according to the rotation matrix and the translation vector;

(c) the robot arm is moved by the movable carrying platform to leave the working space, and when the robot arm returns to the working space to operate, the robot arm is controlled to move according to the movement command, and the three-dimensional measuring device is used for obtaining at least three actual positioning points reached by the robot arm;

(d) calculating to obtain a rotation matrix and a translation vector according to the at least three actual positioning points, further calculating to obtain a corresponding actual coordinate system, and then calculating to obtain coordinate correction information by comparing the rotation matrix and the translation vector of the reference coordinate system and the actual coordinate system; and

(e) adjusting the robot arm according to the coordinate correction information to maintain the robot arm operating in the reference coordinate system.

2. The method of claim 1, wherein the movement command comprises controlling the robot to move at least three times with different operations.

3. The coordinate correcting method of a robot arm as claimed in claim 1, wherein the equation of the rotation matrix of the robot arm is as follows:

wherein, P₀、P_xAnd P_yRepresenting three of the anchor points,andrepresenting unit vectors of the X, Y and Z axes, respectively, and R represents the rotation matrix of the robot arm.

4. The coordinate correcting method of a robot arm as claimed in claim 3, wherein the equation of the translation vector of the robot arm is as follows:

wherein P is_x0、P_y0And P_z0Representing the position of the gear point of the robot arm,representing the translation of the robot armAnd (5) vector quantity.

5. The method of claim 4, wherein a rotation matrix variation and a translation vector variation are calculated by comparing the rotation matrix and the translation vector of the reference coordinate system and the actual coordinate system, the coordinate correction information comprises the rotation matrix variation and the translation vector variation, and the equations of the rotation matrix variation and the translation vector variation are as follows:

wherein R andthe rotation matrix and the translation vector respectively represent the reference coordinate system,andrespectively representing the rotation matrix and the translation vector of the actual coordinate system, Δ R representing the variation of the rotation matrix,representing the translation vector variation.

6. The method of claim 1, wherein the three-dimensional measuring device comprises:

the spherical body is detachably assembled on the robot arm and is driven by the robot arm to synchronously move or rotate;

a base; and

three measuring modules, which are arranged on the base, wherein each measuring device comprises a measuring structure and a position sensor, the three measuring structures of the three measuring modules move in the X-axis direction, the Y-axis direction and the Z-axis direction respectively and are in contact with the spherical body, the position sensor is configured to measure the moving distance of the measuring structure when the corresponding measuring structure is pushed by the spherical body,

wherein, the three measuring structures respectively define a measuring space along the movable distance corresponding to each axial direction, in the step (a) and the step (c), the spherical body is driven by the robot arm to move in the measuring space, and the sensing results of the three position sensors reflect the three-dimensional coordinates of the spherical body.

7. The method as claimed in claim 6, wherein the robot arm is coupled to a tool, the tool is driven by the robot arm to operate, and the robot arm is detachably coupled to the spherical body of the three-dimensional measuring device when coupled to the tool.

8. The method of claim 6, wherein the robot arm is connected to the spherical body of the three-dimensional measuring device only in the steps (a) to (c).

9. The method of claim 6, wherein the at least three reference positioning points and the at least three actual positioning points are three-dimensional coordinates of the spherical center of the spherical body measured by the three-dimensional measuring device in the steps (a) to (c).

10. The method of claim 1, wherein the robot is a six-axis robot or a selective compliance assembly robot.

Technical Field

The invention relates to a coordinate correction method, in particular to a coordinate correction method of a robot arm.

Background

Nowadays, robots are increasingly used in various industries. The robot may be moved by the carrier to and from different fields or workstations during operation, rather than stationary to a particular workstation. In this case, if the robot moves to any workstation, the coordinate system needs to be re-established and taught to ensure the working accuracy. However, it takes a lot of time to repeatedly establish the coordinate system and teach the robot arm, which results in a reduction in work efficiency, and it is difficult to ensure that the coordinate system established each time is identical, which may cause a reduction in work accuracy of the robot arm.

Therefore, how to develop a coordinate calibration method for improving the above-mentioned robot arm in the prior art is an urgent need.

Disclosure of Invention

The invention aims to provide a coordinate correction method of a robot arm, which establishes a reference coordinate system of a working space through a three-dimensional measuring device, obtains an actual coordinate system through the three-dimensional measuring device when the robot arm returns to the working space after being temporarily separated, and adjusts the robot arm according to the difference between the reference coordinate system and the actual coordinate system so that the robot arm still keeps operating in the reference coordinate system. Therefore, the coordinate system and the teaching point do not need to be repeatedly established, the working efficiency can be improved, and the high precision of the robot arm can be effectively ensured because the robot arm always operates in the reference coordinate system.

To achieve the above objective, the present invention provides a coordinate calibration method for a robot arm, wherein the robot arm is disposed on a movable stage and operates in at least one working space, and a three-dimensional measuring device is disposed in the working space and configured to measure a position of the robot arm. The coordinate correction method comprises the following steps: (a) when the robot arm is moved by the movable carrying platform to operate in a working space, the robot arm is controlled to move according to the movement command, and at least three reference positioning points reached by the robot arm are obtained by using the three-dimensional measuring device; (b) calculating to obtain a rotation matrix and a translation vector according to at least three reference positioning points, and calculating to obtain a corresponding reference coordinate system according to the rotation matrix and the translation vector; (c) the robot arm is moved away from the working space by the movable carrying platform, and when the robot arm returns to the working space to operate, the robot arm is controlled to move according to the movement command, and at least three actual positioning points reached by the robot arm are obtained by using the three-dimensional measuring device; (d) calculating to obtain a rotation matrix and a translation vector according to at least three actual positioning points, further calculating to obtain a corresponding actual coordinate system, and then calculating to obtain coordinate correction information by comparing the rotation matrix and the translation vector of the reference coordinate system and the actual coordinate system; and (e) adjusting the robot arm according to the coordinate correction information to keep the robot arm operating in the reference coordinate system.

The invention has the beneficial effects that the invention provides a coordinate correction method of the robot arm, which establishes a reference coordinate system of a working space through a three-dimensional measuring device, obtains an actual coordinate system through the three-dimensional measuring device when the robot arm returns to the working space after being temporarily separated, and adjusts the robot arm according to the difference between the reference coordinate system and the actual coordinate system, so that the robot arm still maintains to operate in the reference coordinate system. Therefore, the coordinate system and the teaching point do not need to be repeatedly established, the working efficiency can be improved, and the high precision of the robot arm can be effectively ensured because the robot arm always operates in the reference coordinate system.

Drawings

Fig. 1 is a schematic perspective view of a robot arm, a working space and a three-dimensional measuring device according to a preferred embodiment of the invention.

Fig. 2 is a schematic perspective view of the three-dimensional measuring apparatus of fig. 1.

Fig. 3 is a flowchart illustrating a method for calibrating coordinates of a robot according to a preferred embodiment of the invention.

The reference numbers are as follows:

1: robot arm

2: working platform

3: three-dimensional measuring device

31: spherical body

32: base seat

33: measuring module

34: measuring structure

4: tool with a locking mechanism

5: movable carrying platform

S1, S2, S3, S4, S5: steps of the coordinate correction method

Detailed Description

Some exemplary embodiments that embody features and advantages of the invention will be described in detail in the description that follows. As will be realized, the invention is capable of other and different modifications and its several details are capable of modifications in various obvious respects, all without departing from the scope of the invention, and the description and drawings are to be regarded as illustrative in nature, and not as restrictive.

In order to make the present invention easier to understand, fig. 1 and fig. 2 are used to illustrate a specific embodiment of a robot arm, a movable stage, and a three-dimensional measuring device and a working space thereof, however, it should be noted that possible embodiments of the working space and the three-dimensional measuring device are not limited thereto, and it is only necessary to ensure that the installation position of the three-dimensional measuring device is kept fixed and the position/coordinate of the robot arm can be measured in the working space.

Fig. 1 is a schematic perspective view of a robot arm, a working space and a three-dimensional measuring device according to a preferred embodiment of the invention, and fig. 2 is a schematic perspective view of the three-dimensional measuring device in fig. 1. As shown in fig. 1 and 2, a working space of the three-dimensional measuring device 3 is represented by a working platform 2, the three-dimensional measuring device 3 is fixed on the working platform 2, the robot arm 1 is arranged on a movable stage 5, and the robot arm 1 is driven by the movable stage 5 to move synchronously therewith. Of course, in practical applications, the working platform 2 will also be provided with elements or devices for the robot arm 1 to interact with during operation, and for the sake of convenience, the three-dimensional measuring device 3 on the working platform 2 is only shown in the figure. The robot arm 1 may be, for example, but not limited to, a six-axis robot arm or a selective compliance assembly robot arm (SCARA robot arm). The three-dimensional measuring device 3 is configured to measure the position/coordinate of the robot arm 1, and includes a spherical body 31, a base 32, and three measuring modules 33. The spherical body 31 is detachably assembled to the robot arm 1 and is driven by the robot arm 1 to move or rotate synchronously. Three measurement modules 33 are disposed on the base 32, wherein each measurement module 33 includes a measurement structure 34 and a position sensor. The three measuring structures 34 of the three measuring modules 33 move in the X-axis, Y-axis and Z-axis directions, respectively, and are all in contact with the spherical body 31. The position sensor is configured to sense the moving distance of the measuring structure 34 when the corresponding measuring structure 34 is pushed by the spherical body 31, wherein the position sensor may be, for example, but not limited to, an optical ruler.

Referring to fig. 3, fig. 3 is a flowchart illustrating a coordinate calibration method of a robot arm according to a preferred embodiment of the invention. First, when the robot arm 1 is moved to a work space (e.g., the work platform 2) by the movable stage 5, the robot arm 1 is controlled to move according to the movement command, and at least three reference positioning points reached by the robot arm 1 are obtained by the three-dimensional measuring device 3 (step S1). The movement command may for example, but not exclusively, comprise controlling the robot arm 1 to make at least three movements with different operational movements. Then, a reference coordinate system is established according to the at least three reference positioning points (step S2). Then, the robot arm 1 is moved away from the working space by the movable stage 5, and when the robot arm 1 returns to the working space, the robot arm 1 is controlled to move according to the movement command, and at least three actual positioning points reached by the robot arm 1 are obtained by using the three-dimensional measuring device 3 (step S3), wherein the number of the actual positioning points is the same as the number of the reference positioning points. Then, an actual coordinate system is obtained according to the at least three actual positioning points, and coordinate correction information is calculated according to the reference coordinate system and the actual coordinate system (step S4). Finally, the robot arm 1 is adjusted according to the coordinate correction information, so that the robot arm 1 maintains the operation in the reference coordinate system (step S5).

It follows that the reference coordinate system is established when the robot arm 1 is initially moved to the working space. After the reference coordinate system is established, even if the robot arm 1 moves to other working spaces or fields, when the robot arm 1 returns to the working space in which the reference coordinate system is established, the robot arm 1 can be quickly adjusted by comparing the reference coordinate system with the actual coordinate system, so that the robot arm 1 can still operate in the originally established reference coordinate system without re-establishing the coordinate system and teaching points, and therefore, the working efficiency and precision of the robot arm 1 can be greatly improved.

Referring to fig. 1 to 3, the movable distances of the three measurement structures 34 along the respective axial directions (X-axis, Y-axis, and Z-axis) define a measurement space, in steps S1 and S3 of the coordinate calibration method, the spherical body 31 is driven by the robot arm 1 to move in the measurement space, and the sensing results of the three position sensors reflect the three-dimensional coordinates of the spherical body 31. In some embodiments, the reference positioning point and the actual positioning point in steps S1-S3 of the coordinate calibration method are three-dimensional coordinates of the sphere center of the spherical body 31 measured by the three-dimensional measuring device 3.

The spherical body 31 is detachably coupled to the robot arm 1, so that the robot arm 1 may be coupled to the spherical body 31 only when there is a need to establish or correct a coordinate system, so as to perform the coordinate correction method shown in fig. 3. Further, the robot arm 1 may be coupled to the spherical body 31 only when the positioning point needs to be measured, and specifically, the robot arm 1 may be coupled to the spherical body 31 only in steps S1 to S3 of the coordinate calibration method.

In some embodiments, the robot arm 1 is connected to the tool 4, and the tool 4 is driven by the robot arm 1 to operate on the working platform 2, wherein when the robot arm 1 is connected to the tool 4, the robot arm 1 can also be connected to the spherical body 31 of the three-dimensional measuring device 3. Therefore, when the robot arm 1 performs coordinate system correction, the tool 4 does not need to be removed before correction, and therefore, after correction is completed, the tool 4 does not need to be reinstalled and corresponding adjustment is performed, so that the correction process and the consumed time can be saved, and the working efficiency of the robot arm 1 is indirectly improved.

How to acquire the coordinate system and the coordinate correction information will be exemplified below.

When the robot arm 1 moves according to the movement command, the three-dimensional measurement device 3 can be used to measure and obtain three-dimensional coordinates of three reference positioning points, and the equations (1), (2) and (3) can be used to obtain three reference positioning points P₀、P_xAnd P_yObtaining unit vectors of X-axis, Y-axis and Z-axisAndaccordingly, the rotation matrix R of the robot arm 1 is as shown in equation (4).

Then, the translation vector can be obtained according to the calculation of the rotation matrix RAs shown in the equation (5),

wherein P is_x0、P_y0And P_z0Is the position of the gear position of the robot arm 1. Therefore, a reference coordinate system can be established according to the rotation matrix and the translation vector. In some embodiments, the robot arm 1 is self-referencing to the positioning point P₀Moving along the X axis to obtain a reference positioning point P_xThe robot arm 1 self-referencing the location point P₀Moving along the Y axis to obtain a reference positioning point P_y。

If the robot arm 1 moves to other working spaces or fields, when the robot arm 1 returns to the working space with the established reference coordinate system, the robot arm 1 is controlled to move according to the movement command, and the three-dimensional measuring device 3 is used for measuring and obtaining three-dimensional coordinates of three actual positioning points. Referring to the aforementioned equations (1) to (5), the rotation matrix of the current robot arm 1 can be calculatedAnd translation vectorFrom equations (6) and (7), the rotation matrix variation and the translation vector variation can be calculated

The rotation matrix variation and the translation vector variation are used as coordinate correction information, and the robot arm 1 is adjusted accordingly, so that the robot arm 1 can operate in the originally established reference coordinate system without operating the robot arm 1 in the actual coordinate system and re-teaching points.

In summary, the present invention provides a coordinate calibration method for a robot arm, which establishes a reference coordinate system of a working space through a three-dimensional measuring device, obtains an actual coordinate system through the three-dimensional measuring device when the robot arm returns to the working space after temporarily separating, and adjusts the robot arm according to a difference between the reference coordinate system and the actual coordinate system, so that the robot arm still maintains operation in the reference coordinate system. Therefore, the coordinate system and the teaching point do not need to be repeatedly established, the working efficiency can be improved, and the high precision of the robot arm can be effectively ensured because the robot arm always operates in the reference coordinate system. In addition, when the robot arm is coupled to the tool, the robot arm may be simultaneously coupled to the spherical body of the three-dimensional measuring apparatus. Therefore, when the robot arm is used for correction, a tool does not need to be detached before correction, and therefore after correction is completed, the tool does not need to be reinstalled to perform corresponding adjustment, so that the correction process and the consumed time can be saved, and the working efficiency of the robot arm is indirectly improved.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that the scope of the invention is defined by the appended claims. And that the invention may be modified in various ways by those skilled in the art without departing from the scope of the appended claims.