Method and system for intelligently avoiding grinding singular points of mechanical arm

Abstract

The invention belongs to the field of automatic machining, and relates to a method and system for intelligently avoiding a grinding singular point of a mechanical arm, and the system comprises a trajectory planning module capable of obtaining an initial grinding trajectory of the mechanical arm, a singular point avoiding module capable of obtaining a special grinding trajectory of the mechanical arm near the singular point, a grinding posture module and a mechanical arm control module; the polishing posture module can combine the initial polishing track with a special polishing track near the singular point and generate a complete polishing posture; the mechanical arm control module can control a mechanical arm to work through a command set composed of a complete polishing track and a corresponding polishing posture, the smoothness of the polishing process, the integrity of a to-be-polished piece and the safety of the polishing environment are achieved, the deflection angle of a polishing head does not need to be adjusted at any time in the polishing process, singular points can be effectively and automatically avoided, and the polishing efficiency is improved. And manual special treatment is not needed, the whole-process completely-intelligent grinding effect is achieved, and therefore whole-process intelligent grinding is achieved.

Description

Technical Field

[0001] The present invention relates to the field of automated machining technology, and in particular to a method and system for intelligently avoiding singular points in grinding by a robotic arm. Background Art

[0002] At present, my country generally uses skilled workers to manually complete the production of metal products using electric and pneumatic grinding tools. However, large castings are large in size, heavy in weight, small in batches, and non-standard. During the grinding process, workers need to adjust the deflection angle of the grinding head at any time according to the shape of the workpiece. At the same time, the existing automatic grinding method cannot avoid singular points, and it is necessary to manually handle the singular points that the robot arm cannot reach, and a fully intelligent grinding effect is not achieved.

[0003] Singularity usually refers to the situation where there is a problem with the robot's kinematic model in certain specific postures or joint positions, resulting in an infinite number of inverse kinematic solutions or the inability to calculate the inverse kinematic solution. This means that the robot's range of motion may be limited and it may not be able to cover a specific area or perform a specific task.

[0004] Based on this, the present invention is proposed. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention provides a method and system for intelligently avoiding singular points in grinding by a robotic arm, and the technical solution is as follows:

[0006] In a first aspect, a system for intelligently avoiding singular points in robot arm grinding includes a trajectory planning module, a singular point avoidance module, a grinding posture module, and a robot arm control module;

[0007] The trajectory planning module is used to plan the initial polishing trajectory suitable for the continuous movement of the robot arm from the point cloud data of the workpiece to be polished, and send the initial polishing trajectory to the polishing posture module;

[0008] The singular point avoidance module is used to process the singular points on the initial grinding trajectory, and change the grinding posture by adjusting the contact point between the grinding disc and the workpiece to be polished, so as to avoid the singular points; generate a special grinding trajectory located near the singular point, and merge the special grinding trajectory and the initial grinding trajectory into a complete grinding trajectory, and send it to the grinding posture module and the robot arm control module;

[0009] After receiving the complete polishing trajectory sent by the singular point avoidance module, the polishing posture module plans the corresponding polishing postures in sequence according to the sequence of points on the complete polishing trajectory, and sends the polishing posture at each point to the robot arm control module;

[0010] The robot arm control module receives the complete polishing trajectory sent by the singularity avoidance module and the polishing posture at each point sent by the polishing posture module, controls the robot arm to work according to the command set, and realizes a complete polishing process.

[0011] In a second aspect, a method for intelligently avoiding singular points in grinding by a robotic arm comprises the following steps:

[0012] First, the point cloud data of the workpiece to be polished is sent to the trajectory planning module. The trajectory planning module plans an initial polishing trajectory suitable for the continuous movement of the robot arm based on the point cloud data, and sends the initial polishing trajectory to the singularity avoidance module;

[0013] Then, the singular point avoidance module processes the singular point on the initial polishing trajectory to obtain a special polishing trajectory near the singular point, and merges the initial polishing trajectory with the special polishing trajectory into a complete polishing trajectory, and sends the complete polishing trajectory to the polishing posture module and the robot arm control module;

[0014] Finally, the grinding posture module plans the complete grinding posture according to the complete grinding trajectory and sends it to the robotic arm control module; the robotic arm control module controls the operation of the robotic arm according to the command set composed of the complete grinding trajectory and the corresponding grinding posture to realize the complete grinding process.

[0015] As a further solution of the present invention, the implementation process of the singularity avoidance module is as follows:

[0016] The grinding posture at the singular point in the initial grinding trajectory is taken as the initial state. At this time, the grinding point is point P. While keeping the contact angle θ between the grinding disc and the workpiece to be polished unchanged, the grinding disc is rotated counterclockwise or clockwise with the direction perpendicular to the workpiece to be polished at the grinding point as the rotation axis. The grinding point remains unchanged, and the center coordinate of the grinding disc changes from point O to point O1. Each rotation rotates by an angle in units of α to traverse the entire circumference. The circumference refers to the motion trajectory of the center of the grinding disc during the rotation process. After each rotation, it is determined whether the current robot arm posture can pass through the singular point according to inverse kinematics. If it can pass through the singular point, the actual rotation angle is recorded as kα, where k is the number of rotations. After avoiding the singular point, the grinding disc is rotated clockwise or counterclockwise to the original state to continue grinding.

[0017] As a further solution of the present invention, the calculation formula of the polishing posture is as follows:

[0018]

[0019] Among them, T i Represents the i-th trajectory point in the point cloud data (Tx, Ty, Yz) T The polished posture matrix;

[0020] XPx represents the X-axis component of the coordinate system where the trajectory point is located in the base coordinate system, XPy represents the Y-axis component of the coordinate system where the trajectory point is located in the base coordinate system, and XPz represents the Z-axis component of the coordinate system where the trajectory point is located in the base coordinate system;

[0021] YPx represents the X-axis component of the Y-axis of the coordinate system where the trajectory point is located in the base coordinate system, YPy represents the Y-axis component of the Y-axis of the coordinate system where the trajectory point is located in the base coordinate system, and YPz represents the Z-axis component of the Y-axis of the coordinate system where the trajectory point is located in the base coordinate system;

[0022] ZPx represents the X-axis component of the coordinate system where the trajectory point is located in the base coordinate system, ZPy represents the Y-axis component of the coordinate system where the trajectory point is located in the base coordinate system, and ZPz represents the Z-axis component of the coordinate system where the trajectory point is located in the base coordinate system;

[0023] n represents the number of point cloud data, assuming that n point cloud data are obtained from the workpiece;

[0024] The orientation of the end of the robot arm can be determined by the three unit principal vectors [X B ,Y B ,Z B ] is described by a 3×3 matrix composed of direction cosines relative to the base coordinate system A; that is, the coordinate transformation rotation matrix of the robot end coordinate system B in the base coordinate system A

[0025]

[0026] A X B Represents the component of the X-axis of the robot end coordinate system B in the base coordinate system A; A Y B Represents the component of the Y axis of the robot end coordinate system B in the base coordinate system A; A Z B represents the component of the Z axis of the robot end coordinate system B in the base coordinate system A; r11, r21..., r23, r33 are the components of the projection of each unit vector of the robot end coordinate system B in the unit direction of the base coordinate system A;

[0027] If the coordinates of the grinding point are o(o x ,o y ,o z ), the projection line of the line connecting the grinding point and the grinding disc center on the grinding point tangent plane is defined as the y-axis, the normal line perpendicular to the tangent plane on the grinding point is defined as the z-axis, the grinding disc radius is r, the contact angle between the grinding disc and the workpiece to be polished is θ, then the coordinate of the grinding disc center is o'(o x ,o y+r cosθ,o z +r sinθ), according to the rotation matrix It can be obtained that the robot arm posture matrix when reaching the grinding point is T1:

[0028]

[0029] At the singular point, when traversing to find the angle that can pass through the singular point, a new rotation matrix R is synthesized based on the original rotation matrix z (kα)=,

[0030]

[0031] That is, the rotation matrix at the singular point is Through the grinding posture calculation formula, the rotated grinding posture matrix is ​​obtained

[0032] Substitute the grinding posture matrix T2 and the grinding disc center coordinate O' into the inverse kinematics equation:

[0033] q=f -1 (O,T), where q=[q1,q2,...,q m ] represents the angle of each joint, q m represents the angle of the mth joint, where m represents the number of joints of the robot; f -1 represents the inverse kinematics equation;

[0034] Solve the kinematic equations that satisfy the robot. If a unique solution can be found, it means that the number of traversal searches at this time can enable the robot to avoid this singular point. If there is no solution or multiple solutions are found, it means that the robot is unreachable at this time, and the robot cannot avoid this singular point, and further traversal searches are required.

[0035] Compared with the prior art, the beneficial effects of the present invention are:

[0036] 1) The trajectory planning module of the present invention can obtain the initial grinding trajectory of the robot arm.

[0037] 2) The singularity avoidance module of the present invention can obtain a special grinding trajectory of the robot arm near the singularity point.

[0038] 3) The polishing posture module of the present invention can combine the initial polishing trajectory with the special polishing trajectory near the singular point and generate a complete polishing posture.

[0039] 4) The robot arm control module of the present invention can control the operation of the robot arm through a command set consisting of a complete grinding trajectory and corresponding grinding postures, thereby achieving the smoothness of the grinding process, the integrity of the workpiece to be polished and the safety of the grinding environment. During the grinding process, there is no need to adjust the deflection angle of the grinding head at any time, and singular points can be effectively and automatically avoided. No special manual processing is required, thereby achieving a fully intelligent grinding effect, thereby realizing full-process intelligent grinding. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is a schematic diagram of the initial state of the grinding disc, where the angle between the grinding disc and the plane where the grinding point is located is θ;

[0041] Figure 2 This is a schematic diagram of the grinding disc and the plane where the grinding point is located, maintaining an angle θ when the grinding disc is in a rotating state;

[0042] Figure 3 This is a schematic diagram of a state where the grinding disc is rotated and the angle between the center of the rotating grinding disc and the center of the original grinding disc is kα. DETAILED DESCRIPTION

[0043] The present invention is described in detail below in conjunction with specific embodiments. The embodiments described below are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0044] Example 1

[0045] A system for intelligently avoiding singular points in robot arm grinding, comprising a trajectory planning module, a singular point avoidance module, a grinding posture module, and a robot arm control module;

[0046] The trajectory planning module is used to plan the most efficient, convenient and most suitable initial polishing trajectory for the continuous movement of the robot arm based on the point cloud data of the workpiece to be polished, and send the initial polishing trajectory to the polishing posture module;

[0047] The singular point avoidance module is used to process the singular points on the initial grinding trajectory, and change the grinding posture by adjusting the contact point between the grinding disc and the workpiece to be polished, so as to avoid the singular points; generate a special grinding trajectory located near the singular point, and merge the special grinding trajectory and the initial grinding trajectory into a complete grinding trajectory, and send it to the grinding posture module and the robot arm control module;

[0048] After receiving the complete polishing trajectory sent by the singular point avoidance module, the polishing posture module plans the corresponding polishing postures in sequence according to the sequence of points on the complete polishing trajectory, and sends the polishing posture at each point to the robot arm control module;

[0049] The robot arm control module receives the complete polishing trajectory sent by the singularity avoidance module and the polishing posture at each point sent by the polishing posture module, controls the robot arm to work according to the command set, and realizes a complete polishing process.

[0050] Example 2

[0051] A method for intelligently avoiding singular points in grinding by a robotic arm comprises the following steps:

[0052] First, the point cloud data of the workpiece to be polished is sent to the trajectory planning module. The trajectory planning module plans an initial polishing trajectory suitable for the continuous movement of the robot arm based on the point cloud data, and sends the initial polishing trajectory to the singularity avoidance module;

[0053] Then, the singular point avoidance module processes the singular point on the initial polishing trajectory to obtain a special polishing trajectory near the singular point, and merges the initial polishing trajectory with the special polishing trajectory into a complete polishing trajectory, and sends the complete polishing trajectory to the polishing posture module and the robot arm control module;

[0054] Finally, the grinding posture module plans the complete grinding posture according to the complete grinding trajectory and sends it to the robotic arm control module; the robotic arm control module controls the operation of the robotic arm according to the command set composed of the complete grinding trajectory and the corresponding grinding posture to realize the complete grinding process.

[0055] The implementation process of the singularity avoidance module is as follows:

[0056] The grinding posture at the singular point in the initial grinding trajectory is taken as the initial state. At this time, the grinding point is point P. When the contact angle θ between the grinding disc and the workpiece to be polished is kept unchanged, as follows: Figure 1 As shown in the figure, the grinding disc is rotated counterclockwise or clockwise with the direction perpendicular to the workpiece at the grinding point as the rotation axis. The grinding point remains unchanged, and the center coordinate of the grinding disc changes from point O to point O1, as shown in the figure. Figure 2 As shown; each rotation is rotated by an angle of α, traversing the entire circumference, where the circumference refers to the motion trajectory of the center of the grinding disk during the rotation process; after each rotation, the inverse kinematics is used to determine whether the current robot arm posture can pass through the singularity point. If it can pass through the singularity point, the actual rotation angle is recorded as kα, where k is the number of rotations, such as Figure 3 As shown; after avoiding the singular point, rotate the grinding disc clockwise or counterclockwise to its original state and continue grinding.

[0057] The calculation formula of the grinding posture is as follows:

[0058]

[0059] Among them, Ti Represents the i-th trajectory point in the point cloud data (Tx, Ty, Yz) T The polished posture matrix;

[0060] XPx represents the X-axis component of the coordinate system where the trajectory point is located in the base coordinate system, XPy represents the Y-axis component of the coordinate system where the trajectory point is located in the base coordinate system, and XPz represents the Z-axis component of the coordinate system where the trajectory point is located in the base coordinate system;

[0061] YPx represents the X-axis component of the Y-axis of the coordinate system where the trajectory point is located in the base coordinate system, YPy represents the Y-axis component of the Y-axis of the coordinate system where the trajectory point is located in the base coordinate system, and YPz represents the Z-axis component of the Y-axis of the coordinate system where the trajectory point is located in the base coordinate system;

[0062] ZPx represents the X-axis component of the coordinate system where the trajectory point is located in the base coordinate system, ZPy represents the Y-axis component of the coordinate system where the trajectory point is located in the base coordinate system, and ZPz represents the Z-axis component of the coordinate system where the trajectory point is located in the base coordinate system;

[0063] n represents the number of point cloud data, assuming that n point cloud data are obtained from the workpiece;

[0064] The orientation of the end of the robot arm can be determined by the three unit principal vectors [X B ,Y B ,Z B ] is described by a 3×3 matrix composed of direction cosines relative to the base coordinate system A; that is, the coordinate transformation rotation matrix of the robot end coordinate system B in the base coordinate system A

[0065]

[0066] A X B Represents the component of the X-axis of the robot end coordinate system B in the base coordinate system A; A Y B Represents the component of the Y axis of the robot end coordinate system B in the base coordinate system A; A Z B represents the component of the Z axis of the robot end coordinate system B in the base coordinate system A; r11, r21..., r23, r33 are the components of the projection of each unit vector of the robot end coordinate system B in the unit direction of the base coordinate system A;

[0067] If the coordinates of the grinding point are o(o x ,o y ,o z), the projection line of the line connecting the grinding point and the grinding disc center on the grinding point tangent plane is defined as the y-axis, the normal line perpendicular to the tangent plane on the grinding point is defined as the z-axis, the grinding disc radius is r, the contact angle between the grinding disc and the workpiece to be polished is θ, then the coordinate of the grinding disc center is o'(o x ,o y +r cosθ,o z +r sinθ), according to the rotation matrix It can be obtained that the robot arm posture matrix when reaching the grinding point is T1:

[0068]

[0069] At the singular point, when traversing to find the angle that can pass through the singular point, a new rotation matrix R is synthesized based on the original rotation matrix z (kα)=,

[0070]

[0071] Here, k can also be considered as the number of searches during traversal;

[0072] That is, the rotation matrix at the singular point is Through the grinding posture calculation formula, the rotated grinding posture matrix is ​​obtained

[0073] Substitute the grinding posture matrix T2 and the grinding disc center coordinate O' into the inverse kinematics equation:

[0074] q=f -1 (O,T), where q=[q1,q2,...,q m ] represents the angle of each joint, q m represents the angle of the mth joint, where m represents the number of joints of the robot; f -1 represents the inverse kinematics equation;

[0075] Solve the kinematic equations that satisfy the robot. If a unique solution can be found, it means that the number of traversal searches at this time can enable the robot to avoid this singular point. If there is no solution or multiple solutions are found, it means that the robot is unreachable at this time, and the robot cannot avoid this singular point, and further traversal searches are required.

[0076] In addition, it should be understood that those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment may also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A system for intelligently avoiding singular points in robot arm grinding, characterized by: Including trajectory planning module, singularity avoidance module, polishing posture module, and robotic arm control module; The trajectory planning module is used to plan the initial polishing trajectory suitable for the continuous movement of the robot arm from the point cloud data of the workpiece to be polished, and send the initial polishing trajectory to the polishing posture module; The singular point avoidance module is used to process the singular points on the initial grinding trajectory, and change the grinding posture by adjusting the contact point between the grinding disc and the workpiece to be polished, so as to avoid the singular points; generate a special grinding trajectory located near the singular point, and merge the special grinding trajectory and the initial grinding trajectory into a complete grinding trajectory, and send it to the grinding posture module and the robot arm control module; After receiving the complete polishing trajectory sent by the singular point avoidance module, the polishing posture module plans the corresponding polishing postures in sequence according to the sequence of points on the complete polishing trajectory, and sends the polishing posture at each point to the robot arm control module; The robot arm control module receives the complete polishing trajectory sent by the singularity avoidance module and the polishing posture at each point sent by the polishing posture module, controls the robot arm to work according to the command set, and realizes a complete polishing process.

2. The method for intelligently avoiding singular points in grinding by a robotic arm as claimed in claim 1, characterized in that: The following steps are involved: First, the point cloud data of the workpiece to be polished is sent to the trajectory planning module. The trajectory planning module plans an initial polishing trajectory suitable for the continuous movement of the robot arm based on the point cloud data, and sends the initial polishing trajectory to the singularity avoidance module; Then, the singular point avoidance module processes the singular point on the initial polishing trajectory to obtain a special polishing trajectory near the singular point, and merges the initial polishing trajectory with the special polishing trajectory into a complete polishing trajectory, and sends the complete polishing trajectory to the polishing posture module and the robot arm control module; Finally, the grinding posture module plans the complete grinding posture according to the complete grinding trajectory and sends it to the robotic arm control module; the robotic arm control module controls the operation of the robotic arm according to the command set composed of the complete grinding trajectory and the corresponding grinding posture to realize the complete grinding process.

3. The method for intelligently avoiding singular points in grinding by a robotic arm according to claim 2, characterized in that: The implementation process of the singularity avoidance module is as follows: The grinding posture at the singular point in the initial grinding trajectory is taken as the initial state. At this time, the grinding point is point P. While keeping the contact angle θ between the grinding disc and the workpiece to be polished unchanged, the grinding disc is rotated counterclockwise or clockwise with the direction perpendicular to the workpiece to be polished at the grinding point as the rotation axis. The grinding point remains unchanged, and the center coordinate of the grinding disc changes from point O to point O1. Each rotation rotates by an angle of α as a unit to traverse the entire circumference. The circumference refers to the motion trajectory of the center of the grinding disc during the rotation process. After each rotation, it is determined whether the current robot arm posture can pass through the singular point according to inverse kinematics. If it can pass through the singular point, the actual rotation angle is recorded as kα, where k is the number of rotations. After avoiding the singularity point, rotate the grinding disc clockwise or counterclockwise to its original state and continue grinding.

4. The method and system for intelligently avoiding singular points in grinding by a robotic arm according to claim 3, characterized in that: The calculation formula of the grinding posture is as follows: Among them, T i Represents the i-th trajectory point in the point cloud data (Tx, Ty, Yz) T The polishing posture matrix; XPx represents the X-axis component of the coordinate system where the trajectory point is located in the base coordinate system, XPy represents the Y-axis component of the coordinate system where the trajectory point is located in the base coordinate system, and XPz represents the Z-axis component of the coordinate system where the trajectory point is located in the base coordinate system; YPx represents the X-axis component of the Y-axis of the coordinate system where the trajectory point is located in the base coordinate system, YPy represents the Y-axis component of the Y-axis of the coordinate system where the trajectory point is located in the base coordinate system, and YPz represents the Z-axis component of the Y-axis of the coordinate system where the trajectory point is located in the base coordinate system; ZPx represents the X-axis component of the coordinate system where the trajectory point is located in the base coordinate system, ZPy represents the Y-axis component of the coordinate system where the trajectory point is located in the base coordinate system, and ZPz represents the Z-axis component of the coordinate system where the trajectory point is located in the base coordinate system; n represents the number of point cloud data, assuming that n point cloud data are obtained from the workpiece; The orientation of the end of the robot arm can be determined by the three unit principal vectors [X B ,Y B ,Z B ] is described by a 3×3 matrix composed of direction cosines relative to the base coordinate system A; that is, the coordinate transformation rotation matrix of the robot end coordinate system B in the base coordinate system A A X B Represents the component of the X-axis of the robot end coordinate system B in the base coordinate system A; A Y B Represents the component of the Y axis of the robot end coordinate system B in the base coordinate system A; A Z B represents the component of the Z axis of the robot end coordinate system B in the base coordinate system A; r11, r21..., r23, r33 are the components of the projection of each unit vector of the robot end coordinate system B in the unit direction of the base coordinate system A; If the coordinates of the grinding point are o(o x ,o y ,o z ), the projection line of the line connecting the grinding point and the grinding disc center on the grinding point tangent plane is defined as the y-axis, the normal line perpendicular to the tangent plane on the grinding point is defined as the z-axis, the grinding disc radius is r, the contact angle between the grinding disc and the workpiece to be polished is θ, then the coordinate of the grinding disc center is o'(o x ,o y +rcosθ,o z +rsinθ), according to the rotation matrix It can be obtained that the robot arm posture matrix when reaching the grinding point is T1: At the singular point, when traversing to find the angle that can pass through the singular point, a new rotation matrix R is synthesized based on the original rotation matrix z (kα), That is, the rotation matrix at the singular point is Through the grinding posture calculation formula, the rotated grinding posture matrix is ​​obtained Substitute the grinding posture matrix T2 and the grinding disc center coordinate O' into the inverse kinematics equation: q=f -1 (O,T), where q=[q1,q2,...,q m ] represents the angle of each joint, q m represents the angle of the mth joint, where m represents the number of joints of the robot; f -1 represents the inverse kinematics equation; Solve the kinematic equations that satisfy the robot. If a unique solution can be found, it means that the number of traversal searches at this time can enable the robot to avoid this singular point. If there is no solution or multiple solutions are found, it means that the robot is unreachable at this time, and the robot cannot avoid this singular point, and further traversal searches are required.

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