Robot tail end blade coordinate system calibration method and system based on axis measurement

Abstract

The invention belongs to the technical field of robot calibration, and particularly discloses a robot tail end blade coordinate system calibration method and system based on axis measurement. Comprising the steps that a robot clamps a calibration tool to move into a line laser measurement view; recording joint angles of a fifth axis and a sixth axis of the robot, and calculating a tail end coordinate system of the robot according to MDH parameters of the robot; the pose of a standard ball on the calibration tool is measured through line laser, and a calibration tool coordinate system is calculated; respectively rotating a fifth shaft and a sixth shaft of the robot, measuring the standard ball by linear laser, and establishing a joint coordinate system of the fifth shaft of the robot according to the motion trail of the standard ball; and calculating a robot tail end blade coordinate system according to the coordinate conversion relation. Calibration of the tail end workpiece of the six-axis industrial robot is converted into calibration of the tail end workpiece of the two-degree-of-freedom robot, the robot kinematic chain is greatly shortened, the precision of the tail end pose data of the robot is improved, and therefore calibration of the tail end workpiece can reach higher precision.

Description

Technical Field

[0001] The present invention belongs to the technical field of robot calibration, and more specifically, relates to a method and system for calibrating the coordinate system of the end blade of a robot based on axis measurement. Background Art

[0002] Blades are key components in aero-engines and are often under harsh working conditions of high temperature, high speed, and high load. Their profile accuracy and surface quality have a direct impact on the life and performance of the engine. Robotic grinding and polishing have the advantages of low cost, high automation, and high efficiency, and are gradually being applied to the grinding and polishing of aero-engine blades to replace manual labor. However, due to the manufacturing and installation errors of the blade fixture at the end of the robot, the actual position of the blade relative to the end of the robot deviates from the designed position, resulting in the deviation of the grinding and polishing trajectory. In the actual machining process, machining defects such as edge cutting and flat heads are likely to occur, making it difficult to meet the high-precision machining requirements of the blade profile. Therefore, it is necessary to quickly and accurately calibrate the workpiece coordinate system such as the end blade of the robot.

[0003] To solve the above problems, Patent Document CN109848989A discloses a method for automatically calibrating and detecting the execution end of a robot based on a ruby probe. An offline program is used to generate a calibration trajectory. In the actual workstation, the robot holds the workpiece, aligns with a fixed ruby probe, touches and explores the corresponding calibration points, obtains the conversion relationship between two sets of calibration points, and calculates the coordinate transformation matrix between the virtual coordinate system of the workpiece and the actual coordinate system of the workpiece based on this, realizing the automatic calibration of the end workpiece coordinate system. Patent Document CN110625600B discloses a method for calibrating the workpiece coordinate system at the end of a robot. The rough calibration of the end workpiece of the robot is realized by manually teaching the robot, and the fine calibration of the end workpiece of the robot is realized by compensating multiple times according to the deviation between the measured value and the theoretical value of the feature points, and the end workpiece coordinate system can be calibrated relatively accurately.

[0004] However, for the methods for calibrating the workpiece coordinate system at the end of the robot disclosed in Patent Document CN109848989A and Patent Document CN110625600B, it is necessary to use the robot kinematic model to calculate the actual measured coordinates of the feature points. Although both of these methods have realized the calibration of the end workpiece coordinate system, due to the low absolute positioning accuracy of the robot, the measurement accuracy of the feature points is low, which limits the improvement of the calibration accuracy of the end workpiece coordinate system and cannot meet the high-precision machining requirements of robot blade grinding and polishing. Summary of the Invention

[0005] In view of the above defects or improvement requirements of the prior art, the present invention provides a calibration method and system for the end-effector blade coordinate system of a robot based on axis measurement. By combining the characteristics of the six-axis robot itself and the characteristics of line laser measurement and calibration, the calibration of the end-effector workpiece of the six-axis industrial robot is converted into the calibration of the end-effector workpiece of a two-degree-of-freedom robot by fixing the first four axes of the six-axis industrial robot, greatly shortening the robot motion chain and improving the accuracy of the end-effector pose data, so that the calibration of the end-effector workpiece can achieve higher accuracy.

[0006] To achieve the above object, according to one aspect of the present invention, a calibration method for the end-effector blade coordinate system of a robot based on axis measurement is proposed, including the following steps:

[0007] S100: The robot holds the calibration tool and moves it into the field of view of the line laser measurement;

[0008] S200: Record the joint angles of the fifth and sixth axes of the robot, and calculate the end-effector coordinate system of the robot according to the MDH parameters of the robot;

[0009] S300: Use line laser measurement to calibrate the pose of the standard ball on the calibration tool, and calculate the calibration tool coordinate system;

[0010] S400: Rotate the fifth and sixth axes of the robot respectively, and use the line laser to measure the standard ball. Establish the joint coordinate system of the fifth axis of the robot according to the motion trajectory of the standard ball;

[0011] S500: Calculate the end-effector blade coordinate system of the robot according to the coordinate transformation relationship.

[0012] As a further preference, in step S200, according to the joint angles of the fifth and sixth axes and the MDH parameters of the robot, calculate the homogeneous coordinate transformation matrix of the end-effector coordinate system {End} relative to the fifth-axis joint coordinate system {Joint5}

[0013] As a further preference, the homogeneous coordinate transformation matrix The calculation formula includes:

[0014]

[0015]

[0016] In the formula, θ5, θ6 are the rotation angles of the fifth and sixth joints of the robot, a5, α5, d6 are the MDH parameters of the robot, cθ = cosθ, sθ = sinθ, cα = cosα, sα = sinα;

[0017] As a further preference, step S300 includes the following steps:

[0018] (301) The line laser measurement obtains three arcs A on the spherical surface of the standard ball i (i = 1, 2, 3), and the Taubin SVD and LM algorithms are used to fit the arcs to obtain the radius of the arcs and the center coordinates in the on-line laser coordinate system {Sensor} Given the radius R of the standard ball and the offset state of the ball center relative to the line laser, calculate the coordinates of the standard ball center in the coordinate system {Sensor}

[0019] (302) Given three points p in three-dimensional space i (i = 1, 2, 3), a coordinate system T can be uniquely determined;

[0020] (303) According to the coordinates from the three ball center coordinates a uniquely determined standard ball center coordinate system {Balls} can be established, and the homogeneous transformation matrix of the ball center coordinate system {Balls} relative to the line laser coordinate system {Sensor} is obtained

[0021] (304) According to the three ball center coordinates in the three-dimensional model of the calibration tool, the ball center coordinate system is also established, and the homogeneous transformation matrix of the ball center coordinate system {Balls} relative to the model coordinate system, i.e., the calibration tool coordinate system {Blade}, is obtained and the homogeneous transformation matrix of the calibration tool coordinate system {Blade} relative to the line laser coordinate system {Sensor} is calculated

[0022]

[0023] Preferably, the calculation model of the coordinates of the standard ball center in the coordinate system {Sensor} includes:

[0024]

[0025] Preferably, the calculation model of the coordinate system T in step (302) includes:

[0026]

[0027] In the formula, p1, p2, p3 are the three ball center coordinates for constructing the coordinate system, p c is the centroid of p i (i = 1, 2, 3), is the unit direction vector from the centroid p c to the point p i .

[0028] As a further preference, step 400 includes the following steps:

[0029] (401) Rotate the sixth axis of the robot, and the line laser measures the motion trajectory of the standard ball, and determines the axis of the sixth axis according to this motion trajectory;

[0030] (402) Rotate the fifth axis of the robot, and the line laser measures the motion trajectory of the standard ball, and determines the axis of the fifth axis according to this motion trajectory;

[0031] (403) Determine the joint coordinate system of the fifth axis of the robot according to the axis of the fifth axis and the axis of the sixth axis of the robot.

[0032] As a further preference, step (401) includes the following steps:

[0033] Independently rotate the sixth axis of the robot, and the line laser continuously collects the cross-sectional arc of the standard ball on the calibration tool at a set frequency. The Taubin SVD and LM algorithms are used to fit the arc and calculate the center coordinates of each arc. The center coordinates are the center motion trajectory points of the three standard balls, and these points form three space circles. Define the line passing through the center of the space circle and perpendicular to the plane where the space circle is located as the perpendicular bisector of the circle. Then the perpendicular bisectors of the three space circles are the axis of the sixth axis of the robot;

[0034] Preferably, the least squares method is used to fit the arc:

[0035]

[0036] In the formula, is the point set of the i-th space circle, (A i , B i , 1, D i ) are the plane equation coefficients of the space circle {C i}, and (A, B, 1, D) are the plane equation coefficients of the parallel plane P of the three space circles.

[0037] As a further preference, step (401) further includes the following steps:

[0038] The method of using projection transformation to fit the center of the space circle as a two-dimensional arc is adopted. Taking the plane P as the xoy plane and the normal vector (A, B, 1) T of the plane as the z-axis to establish a projection coordinate system T P , transform the space circle to the projection coordinate system, project it onto the xoy plane, and then fit the plane arc to obtain the center of the circle. The three-dimensional space coordinates of the center of the circle are obtained through coordinate transformation, and the direction of the axis of the sixth axis of the robot and the coordinates of a point on the axis

[0039]

[0040] Preferably, the three-dimensional space coordinates of the center of the circle:

[0041]

[0042] where is the coordinate of point in the projection coordinate system T P , fitCircle represents fitting an arc using the TaubinSVD and LM algorithms, is the coordinate of the center of the circle in the projection coordinate system T P , is the coordinate of the center of the circle in the line laser coordinate system.

[0043] As a further preference, step (403) includes the following steps:

[0044] According to the axes of the fifth and sixth axes of the robot, the homogeneous transformation matrix of the robot's fifth joint coordinate system {Joint5} relative to the line laser coordinate system {Sensor} can be obtained

[0045]

[0046] where p 56 is the intersection point of the axes of the fifth and sixth axes of the robot, is the direction of the axis of the sixth axis, is the direction of the axis of the fifth axis.

[0047] As a further preference, step 500 includes the following steps:

[0048] Calibrate the homogeneous transformation matrix of the tool coordinate system {Blade} relative to the line laser coordinate system {Sensor} according to the homogeneous transformation matrix of the robot's end coordinate system {End} relative to the robot's fifth axis joint coordinate system {Joint5} The homogeneous transformation matrix of the robot's fifth axis joint coordinate system {Joint5} relative to the line laser coordinate system {Sensor} Construct the homogeneous transformation matrix of the blade coordinate system relative to the robot's end coordinate system

[0049]

[0050] In the formula, is the homogeneous transformation matrix of the robot's fifth axis joint coordinate system {Joint5} relative to the line laser coordinate system {Sensor}.

[0051] According to another aspect of the present invention, there is also provided a calibration system for the robot end blade coordinate system based on axis measurement, including:

[0052] The first main control module is used to control the robot to clamp the calibration tool and move it into the line laser measurement field of view;

[0053] The second main control module is used to record the joint angles of the fifth and sixth axes of the robot, and calculate the robot end coordinate system according to the MDH parameters of the robot;

[0054] The third main control module is used to measure the pose of the standard ball on the calibration tool by line laser measurement, and calculate the calibration tool coordinate system;

[0055] The fourth main control module is used to rotate the fifth and sixth axes of the robot respectively, measure the standard ball by line laser, and establish the fifth axis joint coordinate system of the robot according to the movement trajectory of the standard ball;

[0056] The fifth main control module is used to calculate the robot end blade coordinate system according to the coordinate transformation relationship.

[0057] Generally speaking, compared with the prior art by the above technical solution conceived by the present invention, the following technical advantages are mainly possessed:

[0058] 1. By fixing the first four axes of the six-axis industrial robot, the present invention converts the calibration of the end workpiece of the six-axis industrial robot into the calibration of the end workpiece of a two-degree-of-freedom robot, greatly shortening the robot motion chain and improving the accuracy of the end pose data of the robot, so that the calibration of the end workpiece can reach a higher accuracy.

[0059] 2. By fitting the center trajectory of the standard ball during the rotation around the axis by line laser measurement to the fifth and sixth axis lines of the robot and calculating the robot coordinate system according to the axis, the present invention realizes the accurate measurement of the robot coordinate system.

[0060] 3. The present invention uses the designed calibration tool to replace the blade with a complex surface for measurement, simplifies the measurement process, and also improves the measurement accuracy.

[0061] 4. The calibration tool and the blade of the present invention are clamped on the zero-point tooling with very high repeat installation accuracy, ensuring the reusability and reliability of the calibration results. Brief Description of the Drawings

[0062] Figure 1 is a flowchart of a calibration method for the robot end blade coordinate system based on axis measurement according to an embodiment of the present invention;

[0063] Figure 2 is a schematic diagram of the calibration tool according to an embodiment of the present invention;

[0064] Figure 3It is the calibration flow chart of the fifth-axis coordinate system of the robot involved in the embodiment of the present invention;

[0065] Figure 4 It is the schematic diagram of the robot calibration system involved in the embodiment of the present invention. Specific embodiments

[0066] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0067] As Figure 1 shown, a method for calibrating the coordinate system of the end blade of a robot based on axis measurement provided by an embodiment of the present invention, taking the ABB2600 industrial robot as an example, includes the following steps:

[0068] (1) The robot holds the calibration tool and moves it to the calibration pose so that the three standard balls on the calibration tool are located in the line laser measurement field of view. As Figure 2 shown, the calibration tool is installed on the zero-point tooling at the end of the robot, has the same tenon as the blade to ensure clamping consistency, and has three standard balls for line laser measurement.

[0069] (2) Calculate the coordinate system of the robot end at the calibration pose. Read the joint angles θ5 and θ6 of the fifth axis and the sixth axis from the robot controller, and calculate the homogeneous coordinate transformation matrix of the end coordinate system {End} relative to the fifth joint coordinate system {Joint5} according to the MDH parameters of the ABB 2600 robot The calculation formula is as follows:

[0070]

[0071] Among them, a i , α i , d i , θ i are the MDH parameters of the robot link i, cθ = cosθ, sθ = sinθ;

[0072] (3) Line laser measures the three standard balls on the calibration tool and calculates the calibration tool coordinate system. The line laser measures three arcs A on the spherical surface of the standard ball i (i = 1, 2, 3), and uses the TaubinSVD and LM algorithms to fit the arcs to obtain the radius of the arcs and the center coordinates in the line laser coordinate system {Sensor}Given the radius R of the known standard sphere and the offset state of the sphere center relative to the line laser, the coordinates of the standard sphere center in the coordinate system {Sensor} can be calculated.

[0073]

[0074] Given three points p in three-dimensional space i (i = 1, 2, 3), a coordinate system T can be uniquely determined:

[0075]

[0076] where pc is the centroid of p i (i = 1, 2, 3), and n p is the unit direction vector of the vector p. According to formula (4), from the coordinates of the three sphere centers a uniquely determined coordinate system {Balls} of the standard sphere center can be established, and the homogeneous transformation matrix of the coordinate system {Balls} of the sphere center relative to the line laser coordinate system {Sensor} can be obtained. According to the coordinates of the three sphere centers in the three-dimensional model of the calibration tool, the coordinate system of the sphere center is also established, and the homogeneous transformation matrix of the coordinate system {Balls} of the sphere center relative to the model coordinate system, that is, the calibration tool coordinate system {Blade}, can be obtained. Therefore, the homogeneous transformation matrix of the calibration tool coordinate system {Blade} relative to the line laser coordinate system {Sensor} can be calculated.

[0077]

[0078] (4) Calibrate the fifth joint coordinate system of the robot. The process is as Figure 3 shown. Rotate the fifth and sixth axes of the robot separately. Fit the axes of the fifth and sixth axes of the robot through the motion trajectory of the standard sphere, and determine the fifth joint coordinate system of the robot according to the axes. First, rotate the sixth axis of the robot alone, and the line laser continuously collects the cross-sectional arc of the standard sphere on the calibration tool at the set frequency; use the TaubinSVD and LM algorithms to fit the arc and calculate the coordinates of the corresponding sphere center for each arc through formula (3). The coordinates of the sphere center are the motion trajectory points of the centers of the three standard spheres, and these points form three space circles. Define the line passing through the center of the space circle and perpendicular to the plane where the space circle is located as the perpendicular bisector of the circle. Then the perpendicular bisectors of the three space circles are the axes of the sixth axis of the robot.

[0079] Use the least squares method to fit the plane of the space circle:

[0080]

[0081] where is the point set of the i-th space circle, (A i,B i ,1,D i ) are the coefficients of the plane equation of the space circle {C i}, and (A, B, 1, D) are the coefficients of the plane equation of the parallel plane P of the three space circles. The center of the space circle is fitted by the method of projecting and transforming it into a two-dimensional circular arc. Taking the plane P as the xoy plane and the normal vector (A, B, 1) of the plane T as the z-axis to establish the projection coordinate system T P , transform the space circle into the projection coordinate system, project it onto the xoy plane, and then fit the plane circular arc to obtain the center of the circle, and obtain the three-dimensional space coordinates of the center of the circle through coordinate transformation:

[0082]

[0083] Among them, is the point 's coordinates in the projection coordinate system T P , fitCircle represents fitting the circular arc using the TaubinSVD and LM algorithms, is the center coordinate of the projection coordinate system T P , is the center coordinate in the line laser coordinate system. Thus, the direction of the sixth axis of the robot can be determined and the coordinates of a point on the axis

[0084]

[0085] Then, rotate the fifth axis of the robot alone, and the line laser continuously collects the standard ball cross-sectional circular arc on the calibration tool at the set frequency; processing the circular arc data by the above method can obtain the direction of the fifth axis of the robot and the coordinates of a point on the axis According to the axes of the fifth and sixth axes of the robot, the homogeneous transformation matrix of the robot's fifth joint coordinate system {Joint5} relative to the line laser coordinate system {Sensor} can be obtained

[0086]

[0087] Among them, p 56 is the intersection of the fifth axis and the sixth axis of the robot.

[0088] (5) Calculate the blade coordinate system according to the coordinate relationship. In steps (2), (3), and (4), the homogeneous transformation matrix of the robot's end coordinate system {End} relative to the robot's fifth joint coordinate system {Joint5} is obtained respectively Homogeneous transformation matrix for calibrating the tool coordinate system {Blade} relative to the line laser coordinate system {Sensor} Homogeneous transformation matrix for the robot's fifth joint coordinate system {Joint5} relative to the line laser coordinate system {Sensor} As Figure 4 shown, it is a schematic diagram of the coordinate system and coordinate transformation of the calibration system. The homogeneous transformation matrix of the calibration tool coordinate system (i.e., the blade coordinate system) relative to the robot's end coordinate system is:

[0089]

[0090] According to another aspect of the present invention, there is also provided a calibration system for the blade coordinate system at the end of a robot based on axis measurement, including:

[0091] The first main control module is used to control the robot to hold the calibration tool and move it into the line laser measurement field of view; the second main control module is used to record the joint angles of the robot's fifth and sixth axes, and calculate the robot's end coordinate system according to the MDH parameters of the robot; the third main control module is used to use the line laser measurement to calibrate the pose of the standard ball on the calibration tool and calculate the calibration tool coordinate system; the fourth main control module is used to rotate the robot's fifth and sixth axes respectively, and use the line laser to measure the standard ball, and establish the robot's fifth axis joint coordinate system according to the standard ball movement trajectory; the fifth main control module is used to calculate the robot's end blade coordinate system according to the coordinate transformation relationship.

[0092] Among them, the second main control module is further used to perform the following steps:

[0093] Calculate the homogeneous coordinate transformation matrix of the end coordinate system {End} relative to the fifth axis joint coordinate system {Joint5} according to the joint angles of the fifth and sixth axes and the MDH parameters of the robot

[0094] The homogeneous coordinate transformation matrix The calculation formula includes:

[0095]

[0096] In the formula, θ5, θ6 are the rotation angles of the robot's fifth and sixth joints, a5, α5, d6 are the MDH parameters of the robot, cθ = cosθ, sθ = sinθ, cα = cosα, sα = sinα.

[0097] Based on any of the above embodiments or a combination of multiple embodiments, the third main control module is further used to perform the following steps:

[0098] (301) Use the line laser measurement to obtain three arcs A on the surface of the standard ball i(i = 1, 2, 3), the Taubin SVD and LM algorithms are used to fit the circular arc to obtain the radius of the circular arc and the center coordinates in the online laser coordinate system {Sensor} Given the radius R of the standard sphere and the offset state of the sphere center relative to the line laser, calculate the coordinates of the standard sphere center in the coordinate system {Sensor}

[0099] (302) Given three points p in three-dimensional space i (i = 1, 2, 3) can uniquely determine a coordinate system T;

[0100] (303) According to the coordinates From the three sphere center coordinates A uniquely determined standard sphere center coordinate system {Balls} can be established, and the homogeneous transformation matrix of the sphere center coordinate system {Balls} relative to the line laser coordinate system {Sensor} can be obtained

[0101] (304) According to the three sphere center coordinates in the three-dimensional model of the calibration tool, the sphere center coordinate system is also established, and the homogeneous transformation matrix of the sphere center coordinate system {Balls} relative to the model coordinate system, that is, the calibration tool coordinate system {Blade}, is obtained And calculate the homogeneous transformation matrix of the calibration tool coordinate system {Blade} relative to the line laser coordinate system {Sensor}

[0102]

[0103] Preferably, the calculation model of the coordinates of the standard sphere center in the coordinate system {Sensor} includes:

[0104]

[0105] Preferably, the calculation model of the coordinate system T in step (302) includes:

[0106]

[0107] In the formula, p1, p2, p3 are the three sphere center coordinates for constructing the coordinate system, and p c is p i (i = 1, 2, 3) is the centroid, is from the centroid p c pointing to the point p i is the unit direction vector.

[0108] Based on any of the above embodiments or a combination of multiple embodiments, the fourth main control module is further configured to execute the following steps:

[0109] (401) Rotate the sixth axis of the robot, and the line laser measures the motion trajectory of the standard sphere. Determine the axis of the sixth axis according to this motion trajectory.

[0110] During this process, rotate the sixth axis of the robot alone. The line laser continuously collects the cross-sectional arcs of the standard sphere on the calibration tool at a set frequency, and uses the Taubin SVD and LM algorithms to fit the arcs and calculate the center coordinates of the sphere corresponding to each arc. The center coordinates are the motion trajectory points of the centers of the three standard spheres, and these points form three space circles. Define the straight line passing through the center of the space circle and perpendicular to the plane where the space circle is located as the perpendicular bisector of the circle. Then, the perpendicular bisectors of the three space circles are the axes of the sixth axis of the robot.

[0111] Preferably, use the least squares method to fit the arc:

[0112]

[0113] In the formula, is the point set of the i-th space circle, (A i , B i , 1, D i ) are the plane equation coefficients of the space circle {C i}, and (A, B, 1, D) are the plane equation coefficients of the parallel plane P of the three space circles.

[0114] In addition, use the method of projecting and transforming into a two-dimensional arc to fit the center of the space circle. Take the plane P as the xoy plane, and the normal vector (A, B, 1) T of the plane as the z-axis to establish a projection coordinate system T P . Transform the space circle to the projection coordinate system, project it onto the xoy plane, then fit the plane arc to obtain the center of the circle, and obtain the three-dimensional space coordinates of the center of the circle through coordinate transformation. Determine the direction of the axis of the sixth axis of the robot according to the three-dimensional space coordinates of the center of the circle and the coordinates of a point on the axis

[0115]

[0116] Preferably, the three-dimensional space coordinates of the center of the circle:

[0117]

[0118] Among them, is the coordinate of the point in the projection coordinate system T P , fitCircle represents using the Taubin SVD and LM algorithms to fit the arc, is the center coordinate of the circle in the projection coordinate system T P , It is the center coordinate in the line laser coordinate system.

[0119] (402) Rotate the fifth axis of the robot, measure the motion trajectory of the standard ball with the line laser, and determine the axis of the fifth axis according to this motion trajectory. The calculation steps of this process are the same as those of (401) and will not be described here.

[0120] (403) Determine the joint coordinate system of the fifth axis of the robot according to the axis of the fifth axis and the axis of the sixth axis of the robot.

[0121] In this process, according to the axes of the fifth axis and the sixth axis of the robot, the homogeneous transformation matrix of the fifth joint coordinate system {Joint5} of the robot relative to the line laser coordinate system {Sensor} can be obtained.

[0122]

[0123] Among them, p 56 is the intersection point of the axis of the fifth axis and the axis of the sixth axis of the robot, is the direction of the axis of the sixth axis, is the coordinate of a point on the axis of the sixth axis, is the direction of the axis of the fifth axis, is the coordinate of a point on the axis of the fifth axis.

[0124] Based on any of the above embodiments or a combination of multiple embodiments, the fifth main control module is further configured to perform the following steps:

[0125] Calibrate the homogeneous transformation matrix of the tool coordinate system {Blade} relative to the line laser coordinate system {Sensor} according to the homogeneous transformation matrix of the robot end coordinate system {End} relative to the fifth axis joint coordinate system {Joint5} of the robot. The homogeneous transformation matrix of the fifth axis joint coordinate system {Joint5} of the robot relative to the line laser coordinate system {Sensor} Construct the homogeneous transformation matrix of the blade coordinate system relative to the robot end coordinate system.

[0126]

[0127] In the formula, is the homogeneous transformation matrix of the fifth axis joint coordinate system {Joint5} of the robot relative to the line laser coordinate system {Sensor}.

[0128] In summary, by fixing the first four axes of the six-axis industrial robot, the present invention converts the calibration of the workpiece at the end of the six-axis industrial robot into the calibration of the workpiece at the end of a two-degree-of-freedom robot, greatly shortening the robot motion chain and improving the accuracy of the pose data at the end of the robot, so that the calibration of the workpiece at the end can achieve higher accuracy.

[0129] Those skilled in the art can easily understand that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A calibration method for the coordinate system of the end - effector blade of a robot based on axis measurement, characterized in that It includes the following steps: S100: The robot holds the calibration tool and moves it into the line laser measurement field of view; S200: Record the joint angles of the fifth and sixth axes of the robot, and calculate the coordinate system of the robot end according to the MDH parameters of the robot; S300: Use line laser measurement to calibrate the pose of the standard ball on the calibration tool and calculate the coordinate system of the calibration tool; S400: Rotate the fifth and sixth axes of the robot respectively, measure the standard ball with line laser, and establish the joint coordinate system of the fifth axis of the robot according to the movement trajectory of the standard ball; S500: Calculate the coordinate system of the end blade of the robot according to the coordinate transformation relationship.

2. The calibration method for the coordinate system of the end blade of a robot based on axis measurement according to claim 1, characterized in that, In step S200, according to the joint angles of the fifth axis and the sixth axis and the MDH parameters of the robot, calculate the homogeneous coordinate transformation matrix of the end coordinate system {End} relative to the fifth axis joint coordinate system {Joint5} 3. The calibration method of the robot end blade coordinate system based on axis measurement according to claim 2, characterized in that The homogeneous coordinate transformation matrix The calculation formula of It includes: In the formula, θ5 and θ6 are the rotation angles of the fifth and sixth joints of the robot, a5, α5, and d6 are the MDH parameters of the robot, cθ = cosθ, sθ = sinθ, cα = cosα, sα = sinα.

4. A calibration method for the end - effector blade coordinate system of a robot based on axis measurement according to claim 1, characterized in that, Step S300 includes the following steps: (301) The line laser measurement obtains three arcs A on the spherical surface of the standard ball i (i = 1, 2, 3), and the Taubin SVD and LM algorithms are used to fit the arcs to obtain the radii of the arcs and the center coordinates in the on-line laser coordinate system {Sensor} Given the radius R of the standard ball and the offset state of the ball center relative to the line laser, calculate the coordinates of the standard ball center in the coordinate system {Sensor} (302) Given three points p in three-dimensional space i (i = 1, 2, 3) can uniquely determine a coordinate system T; (303) According to the coordinates From the coordinates of the centers of three balls A uniquely determined standard ball center coordinate system {Balls} can be established, and the homogeneous transformation matrix of the ball center coordinate system {Balls} relative to the line laser coordinate system {Sensor} can be obtained (304) Similarly establish a ball center coordinate system based on the three ball center coordinates in the three-dimensional model of the calibration tool, and obtain the homogeneous transformation matrix of the ball center coordinate system {Balls} relative to the model coordinate system, i.e., the calibration tool coordinate system {Blade} And calculate the homogeneous transformation matrix of the calibration tool coordinate system {Blade} relative to the line laser coordinate system {Sensor} Preferably, the calculation model of the coordinates of the center of the standard ball in the coordinate system {Sensor} includes: Preferably, the calculation model of the coordinate system T in step (302) includes: wherein, p1, p2, p3 are the coordinates of the centers of three spheres for constructing a coordinate system, and p c is the centroid of p i (i = 1, 2, 3), is the unit direction vector pointing from the centroid p c to the point p i .

5. A calibration method for the end - effector blade coordinate system of a robot based on axis measurement according to claim 1, characterized in that, Step 400 includes the following steps: (401) Rotate the sixth axis of the robot, measure the movement trajectory of the standard ball with line laser, and determine the axis of the sixth axis according to this movement trajectory; (402) Rotate the fifth axis of the robot, measure the movement trajectory of the standard ball with line laser, and determine the axis of the fifth axis according to this movement trajectory; (403) Determine the joint coordinate system of the fifth axis of the robot according to the axis of the fifth axis and the axis of the sixth axis of the robot.

6. A calibration method for the end - effector blade coordinate system of a robot based on axis measurement according to claim 5, characterized in that, Step (401) includes the following steps: Rotate the sixth axis of the robot alone, the line laser continuously collects the cross-sectional arc of the standard ball on the calibration tool at a set frequency, uses the Taubin SVD and LM algorithms to fit the arc and calculate the center coordinates corresponding to each arc. The center coordinates are the center movement trajectory points of the three standard balls. These points form three space circles. Define the straight line passing through the center of the space circle and perpendicular to the plane where the space circle is located as the perpendicular bisector of the circle. Then the perpendicular bisectors of the three space circles are the axes of the sixth axis of the robot; Preferably, use the least squares method to fit the arc: In the formula, is the point set of the i-th spatial circle, (A i , B i , 1, D i ) are the plane equation coefficients of the spatial circle {C i}, and (A, B, 1, D) are the plane equation coefficients of the parallel plane P of the three spatial circles.

7. A calibration method for the end - effector blade coordinate system of a robot based on axis measurement according to claim 6, characterized in that, Step (401) also includes the following steps: The method of using the projection transformation to fit the center of a spatial circle into a two-dimensional circular arc. Taking plane P as the xoy plane and the normal vector (A, B, 1) of the plane as the z-axis to establish a projection coordinate system T T Transform the spatial circle to the projection coordinate system, project it onto the xoy plane, then fit the planar circular arc to obtain the center of the circle, and obtain the three-dimensional spatial coordinates of the center of the circle through coordinate transformation. Determine the direction of the sixth axis of the robot according to the three-dimensional spatial coordinates of the center of the circle P and the coordinates of a point on the axis Preferably, the three-dimensional space coordinates of the center of the circle: Among them, is the point in the projection coordinate system T P under the coordinates, fitCircle represents using the TaubinSVD and LM algorithms to fit the circular arc, is the center coordinate of the projection coordinate system T P under, is the center coordinate in the line laser coordinate system.

8. A calibration method for the end-effector blade coordinate system of a robot based on axis measurement according to claim 5, characterized in that, Step (403) includes the following steps: According to the axes of the fifth and sixth axes of the robot, the homogeneous transformation matrix of the robot's fifth joint coordinate system {Joint5} relative to the line laser coordinate system {Sensor} can be obtained Among them, p 56 is the intersection point of the fifth axis axis and the sixth axis axis of the robot, is the direction of the sixth axis axis, is the direction of the fifth axis axis.

9. A calibration method for the coordinate system of the end-effector blade of a robot based on axis measurement according to claim 1, characterized in that, Step 500 includes the following steps: According to the homogeneous transformation matrix of the robot end coordinate system {End} relative to the robot's fifth-axis joint coordinate system {Joint5} Calibrate the homogeneous transformation matrix of the tool coordinate system {Blade} relative to the line laser coordinate system {Sensor} The homogeneous transformation matrix of the robot's fifth-axis joint coordinate system {Joint5} relative to the line laser coordinate system {Sensor} Construct the homogeneous transformation matrix of the blade coordinate system relative to the robot end coordinate system In the formula, is the homogeneous transformation matrix of the robot's fifth-axis joint coordinate system {Joint5} relative to the line laser coordinate system {Sensor}.

10. A calibration system for the end - effector blade coordinate system of a robot based on axis measurement, characterized in that, It includes: The first main control module is used to control the robot to hold the calibration tool and move it into the line laser measurement field of view; The second main control module is used to record the joint angles of the fifth and sixth axes of the robot, and calculate the coordinate system of the robot end according to the MDH parameters of the robot; The third main control module is used to use line laser measurement to calibrate the pose of the standard ball on the calibration tool and calculate the coordinate system of the calibration tool; The fourth main control module is used to rotate the fifth and sixth axes of the robot respectively, measure the standard ball with line laser, and establish the joint coordinate system of the fifth axis of the robot according to the movement trajectory of the standard ball; The fifth main control module is used to calculate the coordinate system of the end blade of the robot according to the coordinate transformation relationship.

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