Robot hand-eye automatic calibration method

Abstract

The invention discloses a robot hand-eye automatic calibration method, which comprises the following steps of S100, mounting a calibration plate on a flange plate at the tail end of a robot, and enabling the center O of a coding area of the calibration plate to be collinear with a six-axis rotating shaft of the robot; s200, determining the distance d between the center of the flange plate and the center O of the coding region of the calibration plate, and the size of the coding region: the length l and the width w; s300, taking d as Z data of current tool data calibrated by the robot; s400, determining a camera view field area needing to be calibrated, and setting three image acquisition plane areas: an upper layer area TopArea, a middle area MidArea and a bottom layer area BotArea; according to the full-automatic hand-eye calibration method for the eyes outside the hands, manual participation is reduced or completely avoided through an automatic means, the calibration efficiency can be remarkably improved, and the consistency and high precision of the calibration process can be guaranteed.

Description

Technical Field

[0001] The invention belongs to the technical field of robot hand-eye calibration, and in particular relates to an automatic robot hand-eye calibration method. Background Art

[0002] Robot hand-eye calibration is an important part of the robot vision system. For the hand-eye joint calibration where the eye is outside the hand, its purpose is to determine the precise spatial relationship between the robot base coordinate system and the vision sensor (such as a 3D sensor). This relationship is critical to the accuracy and reliability of the robot when performing complex tasks such as precision assembly, grasping and placement.

[0003] Traditional hand-eye calibration methods usually rely on manual teaching trajectories, that is, the operator manually guides the robot end effector to move and records multiple key points, which are used to calculate the hand-eye transformation matrix. However, the manual teaching trajectory process has the following main problems:

[0004] First, it is inefficient: the manual teaching process consumes a lot of time and human resources, especially when multiple robots need to be calibrated or the calibration needs to be adjusted frequently.

[0005] The second is poor consistency: due to the different experience, technical level and working status of operators, the quality of the teaching trajectory may vary greatly, resulting in inconsistent calibration accuracy for different operators and inconsistent calibration accuracy for the same operator in different working conditions.

[0006] Third, the accuracy is limited: manual operation cannot guarantee that the same trajectory can be accurately repeated every time, especially in precision tasks, which will significantly affect the accuracy of the calibration results. Summary of the invention

[0007] In order to solve the problems in the prior art, the present invention proposes a robot hand-eye automatic calibration method, which reduces or completely avoids human participation through automated means, which can not only significantly improve the calibration efficiency, but also ensure the consistency and high precision of the calibration process.

[0008] The technical solutions adopted to achieve the above objectives are:

[0009] A robot hand-eye automatic calibration method comprises the following steps:

[0010] S100, connect the calibration plate to the end of the robot;

[0011] S200, determining the distance d between the center of the flange and the center O of the coding area of ​​the calibration plate, and the size of the coding area: length l, width w;

[0012] S300, taking d as the Z data of the current tool data for robot calibration, wherein the tool data is T={0, 0, d};

[0013] S400, determining the camera field of view area that needs to be calibrated, and setting three acquisition image plane areas: an upper area TopArea, a middle area MidArea, and a bottom area BotArea;

[0014] S500, planning the robot photo pose group: randomly generating 30 photo point poses in each plane area, and the target point generation formula is: Among them, m represents the top area TopArea, the middle area MidArea, and the bottom area BotArea, l m and w m Respectively represent the length and width of a layer area, C l and C w Respectively represent the length and width of the code point area;

[0015] S600, performing inverse kinematics on the target points generated in step S500 to obtain the robot's photo pose set J m , m represents the upper area TopArea, the middle area MidArea, and the bottom area BotArea;

[0016] S700: Screen the best photo position to obtain the best photo pose P mi ;

[0017] S800, sending the best photographic posture to the robot in sequence, and the robot carrying the calibration plate moves to each photographic position, triggering the camera to take photos, collect images, and record the current position of the robot;

[0018] S900, after the camera completes image acquisition, the relationship between the camera and the robot base coordinate system is calculated according to the acquired code point image and the corresponding robot position.

[0019] Furthermore, in step 100, a flange is provided at the end of the robot, and the calibration plate is mounted on the flange at the end of the robot, and the center O of the coding area of ​​the calibration plate is made to be colinear with the 6-axis rotation axis of the robot;

[0020] Furthermore, in step S400, it is necessary to determine whether the three selected plane areas are horizontal to the camera imaging plane.

[0021] Furthermore, in step S600, the target points generated in step S500 are subjected to inverse kinematics solution to obtain the robot joint angle corresponding to each target point, and then the target points that fail the inverse solution are eliminated to obtain the robot photography pose set J m .

[0022] Furthermore, in step S700, the joint change ΔJ between each layer group photo position and the initial position J0 is calculated.mi ;

[0023] ΔJ mi =(J0-J i ), i=1~30

[0024] Where m represents the top area TopArea, the middle area MidArea, and the bottom area BotArea; ΔJ mi Indicates the change in the robot joints at the photo-taking position in a certain layer area;

[0025] Then for ΔJ mi The maximum joint change was used as the screening condition, and ΔJ mi Sort in descending order to get ΔSort_J mk , and mark the corresponding P of each joint change in descending order mi :

[0026] ΔSort_J mk = sort(‖ΔJ mi ‖),i=1~30

[0027] Where m represents the top area TopArea, the middle area MidArea, and the bottom area BotArea; ΔJ mi Indicates the change in the robot joints at the photo-taking position of a certain layer area;

[0028] Finally, according to the first 24 (8 photo positions per layer) selected data sets of changes Δopt_J mk Find the corresponding photo pose P mi , where Δopt_J mk =ΔSort_J mk , k=1~8, m represents the upper area TopArea, the middle area MidArea, and the bottom area BotArea.

[0029] Furthermore, in step S800, the robot moves with the calibration plate, records the current robot end tool data posture P, and records the current robot joint angle J0.

[0030] Furthermore, in step S800, when the robot moves with the calibration plate, the calibration plate should be placed in the middle of the middle area, and the images of the coding points captured by the camera should be clear.

[0031] The beneficial effects of the present invention are as follows: the fully automatic hand-eye calibration method with the eye outside the hand provided by the present invention reduces or completely avoids manual participation through automated means, which can not only significantly improve the calibration efficiency, but also ensure the consistency and high precision of the calibration process, thereby avoiding the problem of low calibration accuracy caused by inconsistent manual operation levels in the prior art. DETAILED DESCRIPTION

[0032] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0033] The following is further described in conjunction with specific embodiments:

[0034] A robot hand-eye automatic calibration method comprises the following steps:

[0035] S100, installing the calibration plate on the end flange of the robot so that the center O of the encoding area of ​​the calibration plate is colinear with the 6-axis rotation axis of the robot.

[0036] S200, determine the distance d between the center of the flange and the center O of the coding area of ​​the calibration plate, and the size of the coding area: length l, width w.

[0037] S300 , taking d as the Z data of the current tool data for robot calibration, wherein the tool data is T={0, 0, d}.

[0038] S400, determining the camera field of view area that needs to be calibrated, and setting three image acquisition plane areas: an upper area TopArea, a middle area MidArea, and a bottom area BotArea, and ensuring that the three selected plane areas are horizontal to the camera imaging plane.

[0039] S500, planning the robot photo pose group: randomly generating 30 photo point poses in each plane area, and the target point generation formula is: Among them, m represents the top area TopArea, the middle area MidArea, and the bottom area BotArea, l m and w m Respectively represent the length and width of a layer area, C l and C w Respectively represent the length and width of the code point area.

[0040] S600, perform inverse kinematics on the target points generated in step S500 to obtain the robot joint angle corresponding to each target point, and remove the target points that fail the inverse solution to obtain the robot photo pose set J m , m represents the upper area TopArea, the middle area MidArea, and the bottom area BotArea;

[0041] S700, optimal photo position screening: In order to solve the hand-eye joint with higher accuracy during the robot and camera calibration process, it is usually necessary to ensure that the robot joints at each photo position maintain a large range of motion as much as possible. Therefore, the joint change ΔJ between each layer group photo position and the initial position J0 is calculated first. mi ;

[0042] ΔJ mi =(J0-J i ), i=1~30

[0043] Where m represents the top area TopArea, the middle area MidArea, and the bottom area BotArea; ΔJ mi Indicates the change in the robot joints at the photo-taking position of a certain layer area;

[0044] Then for ΔJ mi The maximum joint change was used as the screening condition, and ΔJ mi Sort in descending order to get ΔSort_J mk , and mark the corresponding P of each joint change in descending order mi :

[0045] ΔSort_J mk = sort(‖ΔJ mi ‖),i=1~30

[0046] Where m represents the top area TopArea, the middle area MidArea, and the bottom area BotArea; ΔJ mi Indicates the change in the robot joints at the photo-taking position of a certain layer area;

[0047] Finally, according to the first 24 (8 photo positions per layer) selected data sets of changes Δopt_J mk Find the corresponding photo pose P mi , where Δopt_J mk =ΔSort_J mk , k=1~8, m represents the upper area TopArea, the middle area MidArea, and the bottom area BotArea.

[0048] S800, send the best photo pose to the robot in sequence, and the robot carrying the calibration plate moves to each photo position, triggering the camera to take photos, collect images, and record the current robot position. The robot moves with the calibration plate, so that the calibration plate is placed in the middle of the middle area, and the image of the coded points collected by the camera is clear, and the current robot end tool data pose P is recorded, and the current robot joint angle J0 is recorded.

[0049] S900. After the camera completes image acquisition, the relationship between the camera and the robot base coordinate system can be calculated based on the acquired coded point image and the corresponding robot position.

[0050] After the camera completes image acquisition, it can obtain each photographic pose P and the coded point image under each photographic pose. According to the eye-outside-hand calibration method, the pose relationship between the calibration plate and the robot base coordinate system is finally solved, and then converted into the AX=XB equation. The mature and public solution method calibrateHandeye() in OpenCV can be used to solve the relationship between the camera and the robot base coordinate system.

[0051] The fully automatic hand-eye calibration method with eye outside the hand provided by the present invention reduces or completely avoids manual participation through automated means, which can not only significantly improve the calibration efficiency, but also ensure the consistency and high precision of the calibration process, thereby avoiding the problem of low calibration accuracy caused by inconsistent manual operation levels in the prior art.

[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein, but these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A robot hand-eye automatic calibration method, characterized in that: The steps include: S100, connect the calibration plate to the end of the robot; S200, determining the distance d between the center of the flange and the center O of the coding area of ​​the calibration plate, and the size of the coding area: length l, width w; S300, taking d as the Z data of the current tool data for robot calibration, wherein the tool data is T={0, 0, d}; S400, determining the camera field of view area that needs to be calibrated, and setting three acquisition image plane areas: an upper area TopArea, a middle area MidArea, and a bottom area BotArea; S500, planning the robot photo pose group: randomly generating 30 photo point poses in each plane area, and the target point generation formula is: Among them, m represents the top area TopArea, the middle area MidArea, the bottom area BotArea, lm and w m Respectively represent the length and width of a layer area, C l and C w Respectively represent the length and width of the code point area; S600, performing inverse kinematics on the target points generated in step S500 to obtain the robot's photo pose set J m , m represents the upper area TopArea, the middle area MidArea, and the bottom area BotArea; S700: Screen the best photo position to obtain the best photo pose P mi ; S800, sending the best photographic posture to the robot in sequence, and the robot carrying the calibration plate moves to each photographic position, triggering the camera to take photos, collect images, and record the current position of the robot; S900, after the camera completes image acquisition, the relationship between the camera and the robot base coordinate system is calculated according to the acquired code point image and the corresponding robot position.

2. A robot hand-eye automatic calibration method according to claim 1, characterized in that: In step 100, a flange is provided at the end of the robot, and the calibration plate is mounted on the flange at the end of the robot, and the center O of the encoding area of ​​the calibration plate is made to be colinear with the 6-axis rotation axis of the robot.

3. The method for automatic hand-eye calibration of a robot according to claim 1, characterized in that: In step S400, it is necessary to determine whether the three selected plane areas are horizontal to the camera imaging plane.

4. The method for automatic hand-eye calibration of a robot according to claim 1, characterized in that: In step S600, the target points generated in step S500 are subjected to inverse kinematics solution to obtain the robot joint angle corresponding to each target point, and then the target points that fail the inverse solution are eliminated to obtain the robot shooting pose set J m .

5. The method for automatic hand-eye calibration of a robot according to claim 1, characterized in that: In step S700, the joint change ΔJ between each layer group photo position and the initial position J0 is calculated. mi ; ΔJ mi =(J0-Ji ) , i=1~30 Where m represents the top area TopArea, the middle area MidArea, and the bottom area BotArea; ΔJ mi Indicates the change in the robot joints at the photo-taking position of a certain layer area; Then for ΔJ mi The maximum joint change was used as the screening condition, and ΔJ mi In descending order, we get ASort_J mk , and mark the corresponding P of each joint change in descending order mi : ΔSort_J mk =sort(||ΔJ mi ||),i=1~30 Where m represents the top area TopArea, the middle area MidArea, and the bottom area BotArea; ΔJ mi Indicates the change in the robot joints at the photo-taking position of a certain layer area; Finally, according to the first 24 (8 photo positions per layer) selected data sets of changes Δopt_J mk Find the corresponding photo pose P mi , where Δopt_J mk =ΔSort_J mk , k=1~8, m represents the upper area TopArea, the middle area MidArea, and the bottom area BotArea.

6. The method for automatic hand-eye calibration of a robot according to claim 1, characterized in that: In the step S800, the robot moves with the calibration plate, records the current robot end tool data posture P, and records the current robot joint angle J0.

7. The method for automatic hand-eye calibration of a robot according to claim 6, characterized in that: In step S800, when the robot moves with the calibration plate, the calibration plate should be placed in the middle of the middle area, and the image of the coding points collected by the camera should be clear.

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