TWI710441B - Coordinate calibration method of manipulator - Google Patents

Abstract

The present disclosure provides a coordinate calibration method of a manipulator, comprising steps of: (a) controlling the manipulator to move according to a movement command when the manipulator operating in a work space, and utilizing a 3D (3-dimensional) measuring device to acquire the 3D coordinates of reference anchor points reached by the manipulator; (b) acquiring a reference coordinate system according to the reference anchor points; (c) the manipulator leaving the work space, controlling the manipulator to move according to a movement command when the manipulator going back to operate in the work space, and utilizing the 3D measuring device to acquire the 3D coordinates of actual anchor points reached by the manipulator; (d) acquiring an actual coordinate system according to the actual anchor points, and calculating a coordinate compensating information according to the reference and actual coordinate systems; and (e) adjusting the manipulator according to the coordinate compensating information so as to maintain the manipulator operating with the reference coordinate system.

Description

Coordinate correction method of robotic arm

This case is about a method of coordinate correction, especially a method of coordinate correction of a robotic arm.

Nowadays, the application of robots in various industries is becoming more and more extensive. During operation, the robot may be moved to and from different fields or workstations by the movement of the carrier, rather than fixedly operating at a specific workstation. In this case, if the robot moves to any workstation, it needs to re-establish the coordinate system and teach points to ensure the accuracy of the work. However, repeatedly establishing the coordinate system and teaching points will consume a lot of time, resulting in reduced work efficiency, and it is difficult to ensure that the coordinate system established every time is exactly the same, which may reduce the working accuracy of the robotic arm.

Therefore, how to develop a coordinate correction method that can improve the above-mentioned conventional robot arm is actually an urgent need.

The purpose of this case is to provide a coordinate correction method for a robotic arm, which uses a three-dimensional measuring device to establish a reference coordinate system for the working space. When the robotic arm returns to the working space after a temporary departure, the actual coordinate system is obtained through the three-dimensional measuring device, and The robot arm is adjusted according to the difference between the reference coordinate system and the actual coordinate system, so that the robot arm still operates in the reference coordinate system. In this way, there is no need to repeatedly establish a coordinate system and teach points, which can improve work efficiency, and since the robotic arm always operates in the reference coordinate system, the high precision of the robotic arm can be effectively ensured.

In order to achieve the above objective, the present application provides a method for coordinate calibration of a robotic arm, wherein the robotic arm is arranged on a movable stage and operates in at least one working space. The working space is provided with a three-dimensional measuring device, and the three-dimensional measuring device is built on the measuring machine. The position of the arm. The coordinate correction method includes the steps: (a) When the robot arm is moved by the movable stage to operate in the working space, the robot arm is controlled to move according to the movement command, and the three-dimensional measuring device is used to obtain at least three reference positions reached by the robot arm Point; (b) calculate the rotation matrix and translation vector based on at least three reference positioning points, and calculate the corresponding reference coordinate system based on the rotation matrix and translation vector; (c) the robot arm is moved by the movable stage and leaves the working space, When the robot arm returns to the working space, it controls the robot arm to move according to the movement command, and uses the three-dimensional measuring device to obtain at least three actual positioning points reached by the robot arm; (d) Calculate based on at least three actual positioning points Obtain the rotation matrix and translation vector, and then calculate and obtain the corresponding actual coordinate system, and then calculate and obtain the coordinate correction information by comparing the reference coordinate system and the rotation matrix and translation vector of the actual coordinate system; and (e) adjust the robot arm according to the coordinate correction information , To keep the robot arm operating in the reference coordinate system.

Some typical embodiments embodying the features and advantages of this case will be described in detail in the following description. It should be understood that this case can have various changes in different aspects, all of which do not depart from the scope of this case, and the descriptions and illustrations therein are essentially for illustrative purposes, rather than being constructed to limit the case.

In order to make it easier to understand the technology of this case, the following figures 1 and 2 will illustrate the specific aspects of the robotic arm, the movable stage, the three-dimensional measuring device and the working space in which they are located. However, it should be noted that the working space and three-dimensional The possible implementation of the measuring device is not limited to this. It is only necessary to ensure that the setting position of the 3D measuring device remains fixed, and the position/coordinates of the robotic arm can be measured in the working space.

Figure 1 is a schematic diagram of the three-dimensional structure of the robotic arm, working space, and three-dimensional measurement device of the preferred embodiment of the present invention, and Figure 2 is a schematic diagram of the three-dimensional structure of the three-dimensional measurement device of Figure 1. As shown in Figures 1 and 2, the working platform 2 represents the working space where the three-dimensional measuring device 3 is located. The three-dimensional measuring device 3 is fixed on the working platform 2, and the robot arm 1 is set on the 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 equipped with components or devices that move the robot arm 1 during operation. Here, for the convenience of explaining the process of establishing coordinates, only the three-dimensional measurement on the working platform 2 is shown in the figure. Device 3. The robot arm 1 may be, for example, but not limited to, a six-axis robot arm or a SCARA robot arm. The three-dimensional measuring device 3 is constructed to measure the position/coordinate of the robotic 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 robotic arm 1, and is driven by the robotic arm 1 to move or rotate synchronously. The three measurement modules 33 are all disposed on the base 32, and each measurement module 33 includes a measurement structure 34 and a position sensor. The three measurement structures 34 of the three measurement modules 33 move in the X-axis, Y-axis and Z-axis directions respectively, and all contact the spherical body 31. The position sensor is configured to sense the moving distance of the measurement structure 34 when the corresponding measurement structure 34 is pushed by the spherical body 31, and the position sensor may be, for example, but not limited to, constituted by an optical ruler.

Please refer to Fig. 3, which is a schematic flow chart of the coordinate correction method of the robot arm according to the preferred embodiment of the present application. First, when the robot arm 1 is moved to the working space (for example: the work platform 2) by the movable stage 5, the robot arm 1 is controlled to move according to the movement command, and the three-dimensional measuring device 3 is used to obtain at least the reach of the robot arm 1 Three reference positioning points (step S1). The movement command may, for example, but not limited to, include controlling the robot arm 1 to move at least three times with different operation actions. Then, a reference coordinate system is established based on the at least three reference positioning points (step S2). Then, the robot arm 1 is moved by the movable stage 5 to leave the working space. When the robot arm 1 returns to the working space, it controls the robot arm 1 to move according to the movement command, and uses the three-dimensional measuring device 3 to obtain the position of the robot arm 1. At least three actual positioning points reached (step S3), wherein the number of actual positioning points is the same as the number of reference positioning points. Then, the actual coordinate system is obtained according to at least three actual positioning points, and the 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 to keep the robot arm 1 operating in the reference coordinate system (step S5).

It can be seen that when the robot arm 1 moves to the working space for the first time, a reference coordinate system is established. After the reference coordinate system is established, even if the robot arm 1 moves to another workspace or field, when the robot arm 1 returns to the workspace where the reference coordinate system has been established, the robot arm can be quickly adjusted by comparing the reference coordinate system with the actual coordinate system 1. The robot arm 1 can still operate in the originally established reference coordinate system, without the need to re-establish the coordinate system and teach points, thereby greatly improving the efficiency and accuracy of the robot arm 1.

Please refer to Figures 1 to 3 again. The above three measurement structures 34 define the measurement space along the movable distances corresponding to the respective axial directions (X-axis, Y-axis and Z-axis). In step S1 of the coordinate correction method And in step S3, 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 step S1 to step S3 of the coordinate correction method are the three-dimensional coordinates of the center of the sphere 31 measured by the three-dimensional measuring device 3.

The spherical body 31 is detachably connected to the robot arm 1, so the robot arm 1 can be connected to the spherical body 31 only when there is a need to establish or correct the coordinate system, so as to perform the coordinate correction method shown in FIG. 3. Moreover, the robotic arm 1 can be assembled to the spherical body 31 only when the demand measurement site is used. Specifically, the robotic arm 1 can be assembled to the spherical body 31 only in steps S1 to S3 of the coordinate correction method.

In some embodiments, the robotic arm 1 is connected to the tool 4, and the tool 4 is driven by the robotic arm 1 to operate on the work platform 2. Among them, when the robotic arm 1 is connected to the tool 4, the robotic arm 1 also It can be connected to the spherical body 31 of the three-dimensional measuring device 3 at the same time. As a result, when the robot arm 1 performs coordinate system calibration, there is no need to remove the tool 4 before calibration, so after the calibration is completed, there is no need to reinstall the tool 4 and perform corresponding adjustments, which can save calibration procedures and time-consuming, and indirectly upgrade the machine Work efficiency of arm 1

The following will illustrate how to obtain coordinate system and coordinate correction information.

、

及

，據此，機器手臂1之旋轉矩陣R如等式 (4) 所示。

(1)

(2)

(3)

(4) 而後可根據旋轉矩陣R計算取得平移向量

，如等式 (5) 所示，

(5) 其中P _x0、P _y0及P _z0為機器手臂1之檔點位置。藉此，可依據旋轉矩陣及平移向量建立參考座標系。於一些實施例中，機器手臂1自參考定位點P ₀沿X軸移動以獲取參考定位點P _x，機器手臂1自參考定位點P ₀沿Y軸移動以獲取參考定位點P _y。 When the robotic arm 1 moves according to the movement command, the three-dimensional measuring device 3 can be used to measure the three-dimensional coordinates of the three reference positioning points. Through equations (1), (2) and (3), the three reference positioning points can be used P ₀ , P _x and P _y get the unit vector of X axis, Y axis and Z axis

,

and

According to this, the rotation matrix R of the robot arm 1 is shown in equation (4).

(1)

(2)

(3)

(4) Then the translation vector can be calculated according to the rotation matrix R

, As shown in equation (5),

(5) Among them, P _x0 , P _y0 and P _z0 are the gear position of robot arm 1. In this way, a reference coordinate system can be established based on the rotation matrix and the translation vector. In some embodiments, the robot arm 1 moves from the reference anchor point P ₀ along the X axis to obtain the reference anchor point P _x , and the robot arm 1 moves from the reference anchor point P ₀ along the Y axis to obtain the reference anchor point P _y .

及平移向量

。通過等式 (6) 及 (7)，可計算取得旋轉矩陣變化量

及平移向量變化量

。

(6)

(7) And if the robotic arm 1 moves to another working space or field, when the robotic arm 1 returns to the working space where the reference coordinate system has been established, the robotic arm 1 is controlled to move according to the movement command, and the three-dimensional measuring device 3 measures three The three-dimensional coordinates of the actual anchor point. Refer to the aforementioned equations (1) to (5), the rotation matrix of the current robotic arm 1 can be calculated

And translation vector

. Through equations (6) and (7), the rotation matrix change can be calculated

And translation vector change

.

(6)

(7)

Use the change of the rotation matrix and the change of the translation vector as the coordinate correction information, and adjust the robotic arm 1 accordingly, so that the robotic arm 1 can operate in the originally established reference coordinate system without requiring the robotic arm 1 to operate in reality In the coordinate system and re-teach points.

In summary, this case provides a method for coordinate correction of a robotic arm, which uses a three-dimensional measuring device to establish a reference coordinate system for the working space. When the robotic arm returns to the working space after a temporary departure, the actual coordinate system is obtained through the three-dimensional measuring device , And adjust the robot arm according to the difference between the reference coordinate system and the actual coordinate system, so that the robot arm still operates in the reference coordinate system. In this way, there is no need to repeatedly establish a coordinate system and teach points, which can improve work efficiency, and since the robotic arm always operates in the reference coordinate system, the high precision of the robotic arm can be effectively ensured. In addition, when the robotic arm is connected to the tool, the robotic arm can also be connected to the spherical body of the three-dimensional measuring device at the same time. In this way, when the robot is calibrated, there is no need to remove the tool before calibration, so after the calibration is completed, there is no need to reinstall the tool to perform corresponding adjustments, which can save calibration procedures and time-consuming, and indirectly improve the working efficiency of the robot.

It should be noted that the above is only a preferred embodiment for explaining the case, and the case is not limited to the described embodiment. The scope of the case is determined by the scope of the patent application attached. Moreover, this case can be modified in many ways by those who are familiar with this technology, but it is not deviated from the protection of the scope of the patent application.

1: Robotic arm 2: Work platform 3: Three-dimensional measuring device 31: spherical body 32: Pedestal 33: Measurement module 34: Measurement structure 4: tools 5: Movable stage S1, S2, S3, S4, S5: steps of coordinate correction method

Figure 1 is a schematic diagram of the three-dimensional structure of the robotic arm, the working space and the three-dimensional measuring device of the preferred embodiment of the present invention.

Figure 2 is a schematic diagram of the three-dimensional structure of the three-dimensional measuring device of Figure 1.

Figure 3 is a schematic flow chart of the coordinate correction method of the robotic arm of the preferred embodiment of the present invention.

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

Claims (10)

A method for coordinate correction of a robotic arm, wherein the robotic arm is arranged on a movable stage and operates in at least one working space, and a three-dimensional measuring device is arranged in the working space, and the three-dimensional measuring device is constructed to measure the robot arm Position, the coordinate correction method includes steps: (a) When the robotic arm is moved by the movable stage to operate in the working space, control the robotic arm to move according to a movement command, and use the three-dimensional measuring device to obtain at least three references reached by the robotic arm location point; (b) Calculate and obtain a rotation matrix and a translation vector based on the at least three reference positioning points, and calculate and obtain a corresponding reference coordinate system based on the rotation matrix and the translation vector; (c) The robotic arm is moved by the movable stage to leave the working space, and when the robotic arm returns to the working space to operate, the robotic arm is controlled to move according to the movement command, and the three-dimensional measuring device is used to obtain At least three actual positioning points reached by the robotic arm; (d) Calculate and obtain a rotation matrix and a translation vector based on the at least three actual positioning points, and then calculate and obtain a corresponding actual coordinate system, and then compare the reference coordinate system and the rotation matrix and the translation of the actual coordinate system Vector, calculate and obtain a standard correction information; and (e) Adjust the robotic arm according to the coordinate correction information to keep the robotic arm operating in the reference coordinate system. The coordinate correction method according to claim 1, wherein the movement command includes controlling the robot arm to move at least three times with different operation actions. The coordinate correction method according to claim 1, wherein the equation of the rotation matrix of the robot arm is as follows:

；

；

；

; Among them, P ₀ , P _x and P _y represent the three anchor points,

,

and

Respectively represent the unit vectors of the X axis, Y axis and Z axis, and R represents the rotation matrix of the robot arm. The coordinate correction method according to claim 3, wherein the equation of the translation vector of the robot arm is as follows:

; Where P _x0 , P _y0 and P _z0 represent the gear position of the robot arm,

Represents the translation vector of the robot arm. The coordinate correction method according to claim 4, wherein a rotation matrix change amount and a translation vector change amount are calculated by comparing the reference coordinate system and the rotation matrix of the actual coordinate system and the translation vector, and the coordinate correction The information includes the change of the rotation matrix and the change of the translation vector. The equations of the change of the rotation matrix and the change of the translation vector are as follows:

；

; Where R and

Respectively represent the rotation matrix and the translation vector of the reference coordinate system,

and

Respectively represent the rotation matrix and the translation vector of the actual coordinate system,

Represents the change of the rotation matrix,

Represents the amount of change in the translation vector. The coordinate correction method according to claim 1, wherein the three-dimensional measuring device comprises: A spherical body, detachably assembled to the robotic arm, and driven by the robotic arm to move or rotate synchronously; A base; and Three measuring modules are arranged on the base. Each of the measuring devices includes a measuring structure and a position sensor. The three measuring structures of the three measuring modules are on the X axis, Y axis, and Move in the Z-axis direction 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. Three of the measurement structures define a measurement space along the movable distance corresponding to each axis. In step (a) and step (c), the spherical body is driven by the robotic arm to move in the measurement space Move, the sensing results of the three position sensors reflect the three-dimensional coordinates of the spherical body. The coordinate correction method according to claim 6, wherein the robotic arm is assembled to a tool, the tool is driven by the robotic arm to operate, and the robotic arm is detachably assembled to the tool when assembled to the tool The spherical body of the three-dimensional measuring device. The coordinate correction method according to claim 6, wherein the robotic arm is assembled with the spherical body of the three-dimensional measuring device only in the steps (a) to (c). The coordinate correction method according to claim 6, wherein in the step (a) to the step (c), the at least three reference positioning points and the at least three actual positioning points are the three-dimensional measuring device measured The three-dimensional coordinates of the center of the sphere. The coordinate correction method according to claim 1, wherein the robotic arm is a six-axis robotic arm or a SCARA robotic arm.

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