阅读说明：本技术 一种高精度工业机器人工具tcp标定方法 (High-precision industrial robot tool TCP calibration method ) 是由 吴玲珑 李仁飞 于 2021-08-24 设计创作，主要内容包括：本发明公开了一种高精度工业机器人工具TCP标定方法,包括设有1轴、2轴、3轴、4轴、5轴及6轴的六自由度机器人,利用安装在六自由度机器人末端的靶座、与测量靶座坐标的测量设备,对机器人工具TCP进行标定,六自由度机器人5轴、6轴的杆长小于其他各轴的杆长,所述测量设备为可测量空间坐标的仪器。本发明中TCP标定方法,减小了对机器人绝对定位精度的依赖,在机器人绝对定位精度较低时,也可以标定出具有较高精度的机器人工具TCP。(The invention discloses a high-precision industrial robot tool TCP calibration method which comprises a six-degree-of-freedom robot with 1 shaft, 2 shafts, 3 shafts, 4 shafts, 5 shafts and 6 shafts, wherein the robot tool TCP is calibrated by utilizing a target seat arranged at the tail end of the six-degree-of-freedom robot and measuring equipment for measuring coordinates of the target seat, the rod lengths of the 5 shafts and the 6 shafts of the six-degree-of-freedom robot are smaller than those of other shafts, and the measuring equipment is an instrument capable of measuring space coordinates. The TCP calibration method reduces the dependence on the absolute positioning accuracy of the robot, and can calibrate the robot tool TCP with higher accuracy when the absolute positioning accuracy of the robot is lower.)

1. A high-precision industrial robot tool TCP calibration method comprises the following steps: the method comprises a six-freedom-degree robot provided with 1 shaft, 2 shafts, 3 shafts, 4 shafts, 5 shafts and 6 shafts, and is characterized by comprising the following steps of calibrating a robot tool TCP by utilizing a target holder arranged at the tail end of the six-freedom-degree robot and measuring equipment for measuring coordinates of the target holder:

step 1, rotating 5 shafts of the six-degree-of-freedom robot to a zero position, keeping other shafts static, only rotating 6 shafts of the six-degree-of-freedom robot, measuring coordinate data of m positions in the rotating process of the 6 shafts of the six-degree-of-freedom robot by using measuring equipment, and recording the coordinate data as P_1,1、P_1,2、…、P_1,m；

Step 2, only rotating the 5 shafts of the six-freedom-degree robot, keeping other shafts still, measuring coordinate data of m positions of the six-freedom-degree robot in the 5-shaft rotating process by using measuring equipment, and recording the coordinate data as P_2,1、P₂,₂、…、P_2,m；

Step 3, fitting a space circle through the coordinate data in the step 1, and making a straight line in the direction of the center of the space circle and the normal direction of the plane where the space circle is located;

step 4, fitting a space circle again through the coordinate data in the step 2, and making another straight line in the direction of the center of the space circle and the normal direction of the plane where the space circle is located;

step 5, calculating the intersection point of the two straight lines obtained in the step 3 and the step 4, and using the intersection point P_b(x_b,y_b,z_b) Is a coordinate origin, 5-axis direction (a) of a six-degree-of-freedom robot_x,a_y,a_z) Is the z-axis and 6-axis direction (o) of the six-degree-of-freedom robot_x,o_y,o_z) Is the x-axis and the y-axis direction (n) is determined according to the right-hand rule_x,n_y,n_z) Establishing a coordinate system to obtain a pose matrix T of the coordinate system relative to the measuring equipment_bComprises the following steps:

step 6, establishing a pose transformation matrix T of the 5-axis six-degree-of-freedom robot and the 6-axis six-degree-of-freedom robot₅、T₆And obtaining a positive kinematic equation of the six-degree-of-freedom robot:

T_bT₅T₆P_tool＝P

wherein P is the coordinate value measured by the measuring device, P_toolIs a tool TCP;

step 7, calculating the value P of the tool TCP by using the least square method according to the coordinate data measured in the step 1 and the coordinate data measured in the step 2_tool：

In the formula, P_iFor coordinates measured by the i-th measuring device, T_5iIs a pose matrix T of 5 axes of the six-degree-of-freedom robot in the ith measurement_6iThe matrix is a pose matrix of 6 axes of the six-degree-of-freedom robot in the ith measurement, and n is the total number of measured coordinates.

2. The high-precision industrial robot tool TCP calibration method according to claim 1 is characterized in that: the steps of the space circle fitting method in the steps 2 and 3 are as follows,

based on fitting the coordinate data points of the same set to a plane equation,

let the plane equation be:

Z＝aX+bY+c

in the formula, X, Y, Z is the coordinate of any point in the plane, a, b, c in the equation are undetermined coefficients, and the objective function is obtained by using least square fitting:

in the formula, X_i、Y_i、Z_iIs the coordinate of the ith point in the plane;

obtaining the necessary condition of minimum value according to the objective function, further obtaining:

solving a linear equation set related to a, b and c to obtain a plane equation;

projecting the same group of coordinate data points onto the obtained plane, fitting a circle on the plane by using the projection points, and setting a circle equation as follows:

x²+y²+Ax+By+C＝0

in the formula, x and y are coordinates of any point on the circle, A, B, C is a coefficient to be determined, and a least square method is used for fitting to obtain an objective function:

in the formula, x_i、y_iThe coordinates of the ith point on the circle;

based on the requirement of obtaining minimum value of the objective function, further obtaining:

solving the linear system of equations described above with respect to A, B, C results in an equation for the spatial circle.

3. The high-precision industrial robot tool TCP calibration method according to claim 1 is characterized in that: the zero position in the step 1 refers to a 0-scale angle value corresponding to the 5 axis of the six-degree-of-freedom robot.

4. The high-precision industrial robot tool TCP calibration method according to claim 1 is characterized in that: the rod length of the 5-axis and 6-axis six-degree-of-freedom robot is smaller than that of each other axis.

5. The high-precision industrial robot tool TCP calibration method according to claim 1 is characterized in that: the measuring device is an instrument capable of measuring space coordinates.

Technical Field

The invention relates to the technical field of industrial robot tool TCP calibration, in particular to a calibration method of a high-precision industrial machine TCP.

Background

The robot tool TCP is the positional relationship of the robot tool coordinate system with respect to the robot end flange coordinate system. When the robot works, the position and posture of the working point under the robot tool coordinate system relative to the robot base coordinate system or the world coordinate system are calculated according to the tool TCP and the postures of the robot axes. The traditional TCP calibration method depends on the absolute positioning accuracy of each axis of the robot, so when the absolute positioning accuracy of the robot is low, the TCP calibrated by the traditional method contains large errors, and is difficult to apply to occasions with high accuracy requirements.

Disclosure of Invention

The invention aims to provide a high-precision industrial robot tool TCP calibration method which is simple to operate and convenient for achieving high-precision tool TCP calibration.

In order to solve the technical problems, the invention provides the following technical scheme: a high-precision industrial robot tool TCP calibration method comprises a six-degree-of-freedom robot with 1 shaft, 2 shafts, 3 shafts, 4 shafts, 5 shafts and 6 shafts, and a robot tool TCP is calibrated by using a target holder arranged at the tail end of the six-degree-of-freedom robot and measuring equipment for measuring coordinates of the target holder, and the method comprises the following steps:

step 1, rotating 5 shafts of the six-degree-of-freedom robot to a zero position, keeping other shafts static, only rotating 6 shafts of the six-degree-of-freedom robot, measuring coordinate data of m positions in the rotating process of the 6 shafts of the six-degree-of-freedom robot by using measuring equipment, and recording the coordinate data as P_1,1、P_1,2、…、P_1,m；

Step 2, only rotating the 5 shafts of the six-freedom-degree robot, keeping other shafts still, measuring coordinate data of m positions of the six-freedom-degree robot in the 5-shaft rotating process by using measuring equipment, and recording the coordinate data as P_2,1、P_2,2、…、P_2,m；

Step 3, fitting a space circle through the coordinate data in the step 1, and making a straight line in the direction of the center of the space circle and the normal direction of the plane where the space circle is located;

step 4, fitting a space circle again through the coordinate data in the step 2, and making another straight line in the direction of the center of the space circle and the normal direction of the plane where the space circle is located;

step 5, calculating the intersection point of the two straight lines obtained in the step 3 and the step 4, and using the intersection point P_b(x_b,y_b,z_b) Is a coordinate origin, 5-axis direction (a) of a six-degree-of-freedom robot_x,a_y,a_z) Is the z-axis and 6-axis direction (o) of the six-degree-of-freedom robot_x,o_y,o_z) Is the x-axis and the y-axis direction (n) is determined according to the right-hand rule_x,n_y,n_z) Establishing a coordinate system to obtainA position and posture matrix T of the coordinate system relative to the measuring equipment is obtained_bComprises the following steps:

step 6, establishing a pose transformation matrix T of the 5-axis six-degree-of-freedom robot and the 6-axis six-degree-of-freedom robot₅、T₆And obtaining a positive kinematic equation of the six-degree-of-freedom robot:

T_bT₅T₆P_tool＝P

wherein P is the coordinate value measured by the measuring device, P_toolIs a tool TCP;

step 7, calculating the value P of the tool TCP by using the least square method according to the coordinate data measured in the step 1 and the coordinate data measured in the step 2_tool：

In the formula, P_iFor coordinates measured by the i-th measuring device, T_5iIs a pose matrix T of 5 axes of the six-degree-of-freedom robot in the ith measurement_6iThe matrix is a pose matrix of 6 axes of the six-degree-of-freedom robot in the ith measurement, and n is the total number of measured coordinates.

Further, the spatial circle fitting method in step 2 and step 3 comprises the following steps:

fitting a plane equation according to the coordinate data points of the same group,

let the plane equation be

Z＝aX+bY+c

In the formula, X, Y, Z is the coordinate of any point in the plane, a, b, c in the equation are undetermined coefficients, and the objective function is obtained by using least square fitting:

in the formula, X_i、Y_i、Z_iIs the coordinate of the ith point in the plane;

obtaining the necessary condition of minimum value according to the objective function, further obtaining:

solving a linear equation set related to a, b and c to obtain a plane equation;

projecting the same group of coordinate data points onto the obtained plane, fitting a circle on the plane by using the projection points, and setting a circle equation as follows:

x²+y²+Ax+By+C＝0

in the formula, x and y are coordinates of any point on the circle, A, B, C is a coefficient to be determined, and a least square method is used for fitting to obtain an objective function:

in the formula, x_i、y_iThe coordinates of the ith point on the circle;

based on the requirement of obtaining minimum value of the objective function, further obtaining:

solving the linear system of equations described above with respect to A, B, C results in an equation for the spatial circle.

Further, the zero position in the step 1 refers to a 0-scale angle value corresponding to the axis 5 of the six-degree-of-freedom robot.

Further, the rod lengths of the 5-axis and 6-axis six-degree-of-freedom robot are smaller than those of other axes.

Further, the measuring device is an instrument capable of measuring space coordinates.

Compared with the prior art, the invention has the following beneficial effects:

1. measuring a plurality of coordinate data in the rotating process of the 5-axis and the 6-axis respectively through measuring equipment, and calculating a value of a tool TCP by using a least square method according to two groups of data coordinate points;

2. the rods of the two shafts of 5 shafts and 6 shafts of the six-degree-of-freedom robot are arranged relatively short, so that the two shafts of 5 shafts and 6 shafts have little influence on the error of the TCP, and the high-precision tool TCP calibration is achieved;

3. the method has simple operation process and subsequent data processing process, and is convenient for rapidly finishing the calibration of the TCP.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:

FIG. 1 is a schematic structural diagram of a six-degree-of-freedom robot and a measuring device according to the present invention;

FIG. 2 is a schematic diagram of the coordinate system establishment in step 5 of the present invention;

in the figure: 1. a six-degree-of-freedom robot; 101. 1, a shaft; 102. 2, a shaft; 103. 3, shafts; 104. 4 shafts; 105. 5, an axis; 106. 6 shafts; 2. a target holder; 3. and (4) measuring equipment.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Referring to fig. 1-2, the present invention provides the following technical solutions: a high-precision industrial robot tool TCP calibration method comprises a six-degree-of-freedom robot 1 provided with a 1-axis 101, a 2-axis 102, a 3-axis 103, a 4-axis 104, a 5-axis 105 and a 6-axis 106, and is characterized in that a target holder 2 arranged at the tail end of the six-degree-of-freedom robot and a measuring device 3 for measuring the coordinates of the target holder 2 are utilized to calibrate the robot tool TCP, and the method comprises the following steps:

step 1, mixingThe 5 shaft 105 of the six-freedom-degree robot 1 rotates to a zero position, other shafts are kept static, only the 6 shaft 106 of the six-freedom-degree robot 1 rotates, the measuring equipment 3 measures the coordinate data of m positions in the rotating process of the 6 shaft 106 of the six-freedom-degree robot 1 and records the coordinate data as P_1,1、P_1,2、…、P_1,m. In this step, "rotate the 5-axis 105 of the six-degree-of-freedom robot 1 to the zero position" means to rotate the 5-axis 105 to the corresponding 0-scale angle value.

Step 2, only rotating the 5 shafts 105 of the six-degree-of-freedom robot 1, keeping other shafts still, measuring the coordinate data of m positions in the rotating process of the 5 shafts 105 of the six-degree-of-freedom robot 1 by the measuring equipment 3, and recording the coordinate data as P_2,1、P_2,2、…、P_2,m；

Step 3, fitting a space circle through the coordinate data in the step 1, and making a straight line in the direction of the center of the space circle and the normal direction of the plane where the space circle is located;

step 4, fitting a space circle again through the coordinate data in the step 2, and making another straight line in the direction of the center of the space circle and the normal direction of the plane where the space circle is located;

step 5, calculating the intersection point of the two straight lines obtained in the step 3 and the step 4, and using the intersection point P_b(x_b,y_b,z_b) A 5-axis direction (a) of the six-degree-of-freedom robot 1 as a coordinate origin_x,a_y,a_z) Is in the z-axis and 6-axis directions (o)_x,o_y,o_z) Is the x-axis and the y-axis direction (n) is determined according to the right-hand rule_x,n_y,n_z) Establishing a coordinate system base5 (as shown in fig. 2), a pose matrix T of base5 with respect to measuring device 3 may be obtained_bComprises the following steps:

step 6, establishing a pose transformation matrix T of the 5-axis 105 of the six-degree-of-freedom robot 1 and the 6-axis 106 of the six-degree-of-freedom robot 1₅、T₆To obtain the normal motion of the six-freedom-degree robot 1The kinetic equation:

T_bT₅T₆P_tool＝P

where P is the coordinate value measured by the measuring device 3, P_toolA tool TCP is to be solved;

step 7, calculating the value P of the tool TCP by using the least square method according to the coordinate data measured in the step 1 and the coordinate data measured in the step 2_tool:

In the formula, P_iFor the coordinates measured by the i-th measuring device 3, T_5iIs a pose matrix T of 5 axes of the six-degree-of-freedom robot 1 in the ith measurement_6iIs a position and posture matrix of 6 axes of the six-freedom-degree robot 1 in the ith measurement, and n is the total number of measured coordinates.

Meanwhile, the spatial circle fitting method in the step 2 and the step 3 comprises the following steps:

fitting a plane equation according to the coordinate data points of the same group,

let the plane equation be:

Z＝aX+bY+c

x, Y, Z in the equation is the coordinate of any point in the plane, a, b and c in the equation are undetermined coefficients, and the objective function is obtained by using least square fitting:

in the formula, X_i、Y_i、Z_iIs the coordinate of the ith point in the plane;

obtaining the necessary condition of minimum value according to the objective function, further obtaining:

namely, it is

Solving a linear equation set related to a, b and c to obtain a plane equation;

projecting the same group of coordinate data points onto the obtained plane, fitting a circle on the plane by using the projection points, and setting a circle equation as follows:

x²+y²+Ax+By+C＝0

in the formula, x and y are coordinates of any point on the circle, A, B, C is a coefficient to be determined, and a least square method is used for fitting to obtain an objective function:

in the formula, x_i、y_iThe coordinates of the ith point on the circle;

based on the requirement of obtaining minimum value of the objective function, further obtaining:

namely, it is

Solving the linear system of equations described above with respect to A, B, C results in the equation for the circle, and thus the fitted spatial circle in steps 2 and 3.

The measuring device 3 is an instrument capable of measuring space coordinates and is used for measuring space coordinate data of the target holder 2 at each position, and after the measuring device 3 is erected, six shafts of the six-degree-of-freedom robot 1 need to be rotated to appropriate positions, so that the point position coordinate data can be conveniently measured by the external measuring device 3 in the step 2 and the step 3.

The TCP calibration method does not depend on the precision of the front four axes of the six-degree-of-freedom robot 1, the rod lengths of the 5-axis 105 and the 6-axis 106 of the six-degree-of-freedom robot are far shorter than those of other axes, and the rod lengths of the two axes of the 5-axis 105 and the 6-axis 106 are set to be shorter, so that the error influence of the 5-axis 105 and the 6-axis 106 on TCP is small, and the high-precision tool TCP calibration is achieved. In addition, the method is simple in operation and subsequent data processing, the TCP precision can reach within +/-0.2 mm, the method for calibrating the TCP reduces the dependence on the absolute positioning precision of the robot, and when the absolute positioning precision of the robot is low, a robot tool TCP with high precision can be calibrated.

It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.

Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.