阅读说明：本技术 一种基于激光跟踪仪的机械臂校准方法及系统 (Mechanical arm calibration method and system based on laser tracker ) 是由 张娜 杨初 冯丽颖 成俊杰 陈晋龙 于 2020-12-21 设计创作，主要内容包括：本发明涉及一种基于激光跟踪仪的机械臂校准方法及系统,利用激光跟踪仪实时确定靶球的球心坐标,然后以空间任一点作为校准点,根据激光跟踪仪实时确定的球心坐标,利用5点工具坐标校准法通过调节机械臂使靶球以任意5种姿态示教校准点,完成工具坐标的校准,另外,建立上表面设有三个孔位的用户校准模块,根据激光跟踪仪实时确定的球心坐标,利用3点用户坐标校准法通过调节机械臂使靶球分别落入三个孔位内,并在孔位内对靶球进行调节,完成用户坐标的校准,通过机械臂的精密微调和激光跟踪仪的测量精度保证了机械臂的校准精度和校准重复度。(The invention relates to a mechanical arm calibration method and a system based on a laser tracker, which are characterized in that the center coordinates of a target ball are determined in real time by the laser tracker, then any point in space is used as a calibration point, according to the center coordinates determined in real time by the laser tracker, a 5-point tool coordinate calibration method is used for teaching the calibration point by adjusting the mechanical arm in any 5 postures, and the calibration of the tool coordinates is completed.)

1. A mechanical arm calibration system based on a laser tracker is characterized by comprising a tool calibration module, a user calibration module, the laser tracker and a control unit;

one end of the tool calibration module is connected with the tail end of the mechanical arm tool, and the other end of the tool calibration module is fixedly connected with a target ball of the laser tracker;

the laser tracker is in communication connection with the control unit; the laser tracker is used for determining the sphere center coordinates of the target sphere in real time and transmitting the sphere center coordinates to the control unit;

the control unit is used for taking any point in space as a calibration point, teaching the calibration point by adjusting the mechanical arm in any 5 postures according to the sphere center coordinate determined by the laser tracker in real time by using a 5-point tool coordinate calibration method, and completing the calibration of tool coordinates;

the user calibration module is positioned on a calibration plane; the upper surface of the user calibration module is provided with three hole sites; the hole sites are indicated by ORG, OX and OY, respectively; the ORG hole site is the origin of a user coordinate system; the OX hole site is any point in the positive direction of the X axis of the user coordinate system; the OY hole position is any point in the positive direction of the Y axis of the user coordinate system;

and the control unit is also used for enabling the target balls to fall into the three hole sites respectively by adjusting the mechanical arm by using a 3-point user coordinate calibration method according to the sphere center coordinates determined by the laser tracker in real time, and adjusting the target balls in the hole sites to finish the calibration of the user coordinates.

2. The laser tracker based arm calibration system of claim 1, wherein a central axis of said tool calibration module is collinear with a central axis of said tooling tip.

3. The laser tracker-based arm alignment system of claim 1, wherein said hole site has a diameter equal to a diameter of said target ball.

4. A method of calibrating a robotic arm based on a laser tracker, operating with a calibration system according to any of claims 1 to 3, characterized in that it comprises the steps of:

taking any point in space as a calibration point, taking a coordinate system of a laser tracker as a measurement coordinate system, and recording initial sphere center coordinates of the target sphere when the target sphere is positioned at the calibration point;

adjusting the mechanical arm to enable the target ball to teach the calibration point in any 5 postures according to the sphere center coordinate determined by the laser tracker in real time, and completing the calibration of the tool coordinate; in the teaching process of 5 postures, the corresponding sphere center coordinates when the target sphere reaches the calibration point are all the same as the initial sphere center coordinates;

taking a coordinate system of a laser tracker as a measurement coordinate system, and recording initial spherical center coordinates of the target ball when the target ball is respectively positioned at three hole sites on a user calibration module to obtain initial spherical center coordinates corresponding to the three hole sites respectively;

and respectively adjusting the mechanical arms to enable the target ball to fall into the hole sites according to the sphere center coordinates determined by the laser tracker in real time, adjusting the target ball in the hole sites until the sphere center coordinates of the target ball are the same as the initial sphere center coordinates corresponding to the hole sites, and completing the calibration of the user coordinates after the target ball is adjusted in all three hole sites.

5. The method of claim 4, wherein the step of adjusting the robot arms respectively according to the coordinates of the center of sphere determined by the laser tracker in real time to make the target balls fall into the holes and adjusting the target balls in the holes until the coordinates of the center of sphere of the target balls are the same as the initial coordinates of the center of sphere corresponding to the holes is performed, and after the step of adjusting the target balls in all three holes is performed, the step of completing the calibration of the user coordinates specifically comprises the steps of:

marking the initial spherical center coordinates corresponding to the three hole positions as O (X, Y, z), X (X, Y, z) and Y (X, Y, z);

adjusting the mechanical arm to enable the target ball to fall into an ORG hole site according to the sphere center coordinate determined by the laser tracker in real time, recording the sphere center coordinate of the target ball at the moment, and judging whether the sphere center coordinate of the target ball is the same as O (x, y, z) or not to obtain a first judgment result;

if the first judgment result is negative, adjusting the target ball in the ORG hole site until the sphere center coordinate of the target ball is O (x, y, z);

if the first judgment result is yes, adjusting the mechanical arm to enable the target ball to fall into an OX hole site according to the sphere center coordinate determined by the laser tracker in real time, recording the sphere center coordinate of the target ball at the moment, judging whether the sphere center coordinate of the target ball is the same as X (X, y, z) or not, and obtaining a second judgment result;

if the second judgment result is negative, adjusting the target ball in the OX hole site until the sphere center coordinate of the target ball is X (X, y, z);

if the second judgment result is yes, adjusting the mechanical arm to enable the target ball to fall into an OY hole site according to the sphere center coordinate determined by the laser tracker in real time, recording the sphere center coordinate of the target ball at the moment, and judging whether the sphere center coordinate of the target ball is the same as Y (x, Y, z) or not to obtain a third judgment result;

if the third judgment result is negative, adjusting the target ball in the OY hole position until the sphere center coordinate of the target ball is Y (x, Y, z);

and if the third judgment result is yes, stopping adjusting, and completing the calibration of the user coordinate.

6. A method of calibrating a robotic arm based on a laser tracker, operating with a calibration system according to any of claims 1 to 3, characterized in that it comprises the steps of:

taking any point in space as a calibration point, taking a coordinate system of a laser tracker as a measurement coordinate system, and recording initial sphere center coordinates of the target sphere when the target sphere is positioned at the calibration point;

adjusting the mechanical arm to enable the target ball to teach the calibration point in any 5 postures according to the sphere center coordinate determined by the laser tracker in real time, and completing the calibration of the tool coordinate; in the teaching process of 5 postures, the corresponding sphere center coordinates when the target sphere reaches the calibration point are all the same as the initial sphere center coordinates;

taking a coordinate system of a laser tracker as a measurement coordinate system, recording initial sphere center coordinates of the target sphere when the target sphere is respectively positioned at three hole sites on a user calibration module, and recording the initial sphere center coordinates corresponding to the three hole sites as O (X, Y, z), X (X, Y, z) and Y (X, Y, z);

according to the sphere center coordinates determined by the laser tracker in real time, adjusting the mechanical arm to teach the target sphere to O (X, Y, z-m), X (X, Y, z-m) and Y (X, Y, z-m) respectively, and completing the calibration of user coordinates; where m is any positive value.

7. The method of calibrating a robotic arm based on a laser tracker of claim 6, wherein m is 50 mm.

Technical Field

The invention relates to the technical field of mechanical arm calibration, in particular to a calibration method and a calibration system for realizing tool coordinate calibration and user coordinate calibration of a mechanical arm based on a laser tracker.

Background

With the development of science and technology, the application field of the robot is more and more extensive. In order to complete various work tasks, various different tools need to be installed on the tail end joints of the robot arms. Since the shape and size of the tool are different, the actual operating point of the robot arm changes from the default operating point (TCP point) after the tool is replaced or adjusted. For high precision robotic arm applications, it is often necessary to perform tool coordinate calibration to acquire the pose of the actual working point. The Anchuan mechanical arm provides a 5-point or 25-point tool coordinate calibration method, namely, 5 or 25 gestures are taught at the same position point based on a sharp point calibration piece, and tool coordinate calibration is completed. In addition, the robotic arm provides three coordinate systems: a geodetic coordinate system, a tool coordinate system and a user coordinate system. Generally, in the use control process of the mechanical arm, a user coordinate system is established to facilitate program control. The complex control problem in the base coordinate system can be easily solved by establishing a proper user coordinate system. User coordinate calibration is mainly used to determine the measurement coordinate system. The Anchuan mechanical arm provides a 3-point user coordinate calibration method, namely, based on a teaching origin (O point), an X-axis forward direction (X point) and a Y-axis forward direction (Y point) of a sharp point calibration piece, user coordinate calibration is completed, and a user coordinate system is established.

Under ideal conditions, errors caused by replacement and assembly of the tool can be corrected through tool coordinate calibration and user coordinate calibration, and the actual working point is controlled to move in a specified coordinate system. However, the positioning repeatability of the absolute position of the mechanical arm is poor, the sharp point alignment during calibration has human errors and other factors, and the tool coordinate and the user coordinate have large errors after calibration.

Disclosure of Invention

Based on the above problems, the present invention aims to provide a method and a system for calibrating a robot arm based on a laser tracker, which improve a tool calibration module and a user calibration module and improve the calibration accuracy of tool coordinates and user coordinates.

In order to achieve the purpose, the invention provides the following scheme:

a laser tracker based mechanical arm calibration system comprises a tool calibration module, a user calibration module, a laser tracker and a control unit;

one end of the tool calibration module is connected with the tail end of the mechanical arm tool, and the other end of the tool calibration module is fixedly connected with a target ball of the laser tracker;

the laser tracker is in communication connection with the control unit; the laser tracker is used for determining the sphere center coordinates of the target sphere in real time and transmitting the sphere center coordinates to the control unit;

the control unit is used for taking any point in space as a calibration point, teaching the calibration point by adjusting the mechanical arm in any 5 postures according to the sphere center coordinate determined by the laser tracker in real time by using a 5-point tool coordinate calibration method, and completing the calibration of tool coordinates;

the user calibration module is positioned on a calibration plane; the upper surface of the user calibration module is provided with three hole sites; the hole sites are indicated by ORG, OX and OY, respectively; the ORG hole site is the origin of a user coordinate system; the OX hole site is any point in the positive direction of the X axis of the user coordinate system; the OY hole position is any point in the positive direction of the Y axis of the user coordinate system;

and the control unit is also used for enabling the target balls to fall into the three hole sites respectively by adjusting the mechanical arm by using a 3-point user coordinate calibration method according to the sphere center coordinates determined by the laser tracker in real time, and adjusting the target balls in the hole sites to finish the calibration of the user coordinates.

Based on the calibration system, the invention provides a mechanical arm calibration method based on a laser tracker, which comprises the following steps:

taking any point in space as a calibration point, taking a coordinate system of a laser tracker as a measurement coordinate system, and recording initial sphere center coordinates of the target sphere when the target sphere is positioned at the calibration point;

adjusting the mechanical arm to enable the target ball to teach the calibration point in any 5 postures according to the sphere center coordinate determined by the laser tracker in real time, and completing the calibration of the tool coordinate; in the teaching process of 5 postures, the corresponding sphere center coordinates when the target sphere reaches the calibration point are all the same as the initial sphere center coordinates;

taking a coordinate system of a laser tracker as a measurement coordinate system, and recording initial spherical center coordinates of the target ball when the target ball is respectively positioned at three hole sites on a user calibration module to obtain initial spherical center coordinates corresponding to the three hole sites respectively;

and respectively adjusting the mechanical arms to enable the target ball to fall into the hole sites according to the sphere center coordinates determined by the laser tracker in real time, adjusting the target ball in the hole sites until the sphere center coordinates of the target ball are the same as the initial sphere center coordinates corresponding to the hole sites, and completing the calibration of the user coordinates after the target ball is adjusted in all three hole sites.

The invention also provides another mechanical arm calibration method based on the laser tracker, which comprises the following steps:

taking any point in space as a calibration point, taking a coordinate system of a laser tracker as a measurement coordinate system, and recording initial sphere center coordinates of the target sphere when the target sphere is positioned at the calibration point;

adjusting the mechanical arm to enable the target ball to teach the calibration point in any 5 postures according to the sphere center coordinate determined by the laser tracker in real time, and completing the calibration of the tool coordinate; in the teaching process of 5 postures, the corresponding sphere center coordinates when the target sphere reaches the calibration point are all the same as the initial sphere center coordinates;

taking a coordinate system of a laser tracker as a measurement coordinate system, recording initial sphere center coordinates of the target sphere when the target sphere is respectively positioned at three hole sites on a user calibration module, and recording the initial sphere center coordinates corresponding to the three hole sites as O (X, Y, z), X (X, Y, z) and Y (X, Y, z);

according to the sphere center coordinates determined by the laser tracker in real time, adjusting the mechanical arm to teach the target sphere to O (X, Y, z-m), X (X, Y, z-m) and Y (X, Y, z-m) respectively, and completing the calibration of user coordinates; where m is any positive value.

According to the specific embodiment provided by the invention, the invention discloses the following technical effects:

the invention provides a mechanical arm calibration method and system based on a laser tracker. And determining the sphere center coordinates of the target sphere in real time by using a laser tracker. Then, any point in the space is taken as a calibration point, the calibration point is taught by the target ball in any 5 postures by adjusting the mechanical arm by using a 5-point tool coordinate calibration method according to the sphere center coordinate determined by the laser tracker in real time, the calibration of the tool coordinate is completed, the consistency of the calibration points in the 5 postures during the calibration of the tool coordinate is ensured by means of the high-accuracy space positioning capability of the laser tracker, the absolute positioning error and the artificial error of the mechanical arm are eliminated, and the calibration precision and the calibration repeatability of the mechanical arm can be improved. In addition, a user calibration module is established, three hole sites are arranged on the upper surface of the user calibration module, target balls are enabled to fall into the three hole sites respectively by adjusting the mechanical arm through a 3-point user coordinate calibration method according to the real-time determined spherical center coordinate of the laser tracker, the target balls are adjusted in the hole sites, calibration of user coordinates is completed, and the calibration precision and the calibration repeatability of the mechanical arm are guaranteed through the precise fine adjustment of the mechanical arm and the measurement precision of the laser tracker.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.

Fig. 1 is a schematic structural diagram of a tool calibration module according to the present invention.

Fig. 2 is a connection diagram of the laser tracker and the control unit provided by the invention.

Fig. 3 is a schematic diagram of a tool coordinate calibration process provided by the present invention.

Fig. 4 is a schematic position diagram of a user coordinate system and a geodetic coordinate system provided by the present invention.

Fig. 5 is a schematic structural diagram of a user calibration module provided in the present invention.

FIG. 6 is a schematic diagram of user coordinate calibration provided by the present invention.

FIG. 7 is a flowchart of a calibration method according to the present invention.

FIG. 8 is a flowchart of a method for calibrating user coordinates according to the present invention.

FIG. 9 is a flowchart of another calibration method provided by the present invention.

Description of the symbols:

1-a tool calibration module; 2-target ball; 3-a user calibration module; 4-laser tracker; 5-a control unit.

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.

The invention aims to provide a mechanical arm calibration method and system based on a laser tracker, which improve a tool calibration module and a user calibration module and improve the calibration accuracy of tool coordinates and user coordinates.

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.

Example 1:

the embodiment is used for providing a mechanical arm calibration system based on a laser tracker, and the calibration system comprises a tool calibration module 1, a user calibration module 3, a laser tracker 4 and a control unit 5;

as shown in fig. 1, one end of the tool calibration module 1 is connected to the end of the robot tool, and the other end is fixedly connected to the target ball 2 of the laser tracker 4. In particular, the tool calibration module 1 may hold the target ball 2 of the laser tracker 4. The central axis of the tool calibration module 1 and the central axis of the tool end are located on the same straight line, namely the tool calibration module 1 and the tool end are axially consistent and symmetrical. The length of the tool calibration module 1 should be as short as possible while maintaining structural stability.

As shown in fig. 2, the laser tracker 4 is communicatively connected to the control unit 5. When the laser tracker 4 is used for measurement, the target ball 2 needs to be tracked, and the center position of the target ball 2 is captured in real time. The laser tracker 4 is used for determining the center coordinates of the target ball 2 in real time and transmitting the center coordinates to the control unit 5. The laser tracker 4 employs a leica real-time laser tracker AT 930. The mechanical arm adopts an Anchuan 6-axis mechanical arm MH 24.

The control unit 5 is used for taking any point in space as a calibration point, teaching the calibration point of the target ball 2 in any 5 postures by adjusting the mechanical arm by using a 5-point tool coordinate calibration method according to the sphere center coordinate determined by the laser tracker 4 in real time, and completing the calibration of the tool coordinate;

specifically, as shown in fig. 3, the calibration process of the tool coordinate calibration may include: any point in the space is set as a calibration point, the target ball 2 is positioned at the position of the calibration point, the coordinate system of the laser tracker 4 is used as a measurement coordinate system, and the target ball 2 is tracked by the laser tracker 4 to determine the sphere center coordinates (X, Y, Z) when the target ball 2 is positioned at the calibration point. Then, the robot arm is adjusted by a 5-point tool coordinate calibration method based on the center coordinates determined in real time by the laser tracker 4, so that the calibration points are taught to the target ball 2 in 5 postures, and the center coordinates (X, Y, Z) in the coordinate system of the laser tracker 4 are always kept constant when the target ball 2 is located at the calibration points regardless of the posture at which the target ball reaches the calibration points. Because the positioning accuracy of the laser tracker 4 is very high, the calibration can be well ensured to be carried out at the same position point in 5 calibration steps.

The calibration of the tool coordinate provided by the embodiment can ensure that the calibration points under 5 postures are consistent during the calibration of the tool coordinate by means of the high-accuracy space positioning capability of the laser tracker 4, and the absolute positioning error and the human error of the mechanical arm are eliminated.

And (3) carrying out tool coordinate calibration for multiple times by using the spatial different position points as calibration points, wherein the teaching data of the TCP points are shown in the table 1.

TABLE 1 TCP Point repeatability comparison

As can be seen from table 1, compared with the calibration method using the laser tracker 4 and the target ball 2, the calibration method using the laser tracker 4 and the calibration method using the tip calibration module can ensure that the calibration points reached each time are the same point, thereby overcoming the human error and other factors in the alignment of the tip points during calibration, and further improving the calibration accuracy and the calibration repeatability of the TCP.

The user coordinate system calibration is mainly used for determining the measurement coordinate system. When the calibration plane is inconsistent with the geodetic coordinate system (for example, an included angle exists), a measurement coordinate system can be established through user coordinate calibration, and writing of a subsequent control program is facilitated. As shown in fig. 4, the coordinate system is directly positioned in the user coordinate system with the calibration plane as the reference, the center of the calibration plane is the coordinate origin, the two sides of the calibration plane are respectively in the X direction and the Y direction, and then the mechanical arm is controlled to move in the user coordinate system, so that the error of the inconsistency between the calibration plane and the geodetic coordinate system can be eliminated. For this purpose, user coordinates need to be calibrated.

The user calibration module 3 is located on the calibration plane, the user calibration module 3 has strict flatness, smooth finish and consistent height, and the difference between the user calibration module 3 and the calibration plane is the thickness of the user calibration module 3. As shown in fig. 5, the upper surface of the user calibration block 3 is provided with three holes, the diameter of the holes is equal to the diameter of the target ball 2, preferably, the diameter of the holes is exactly equal to the diameter of the target ball 2, i.e. the deviation between the diameters is small, so that the holes can be closely matched with the target ball 2. The hole positions are respectively expressed by ORG, OX and OY, wherein the ORG hole position is the origin of the user coordinate system, the OX hole position is any point in the forward direction of the X axis of the user coordinate system, and the OY hole position is any point in the forward direction of the Y axis of the user coordinate system.

The control unit 5 is further configured to adjust the mechanical arm to enable the target balls 2 to fall into the three hole sites respectively according to the sphere center coordinates determined by the laser tracker 4 in real time by using a 3-point user coordinate calibration method, and adjust the target balls 2 in the hole sites to complete calibration of the user coordinates.

Specifically, the calibration process of the user coordinate calibration may include: before calibration, the target ball 2 is firstly placed in three hole sites on the user calibration module 3, coordinates of the center of the target ball 2 in a coordinate system of the laser tracker 4 when the target ball 2 is respectively located in three hole sites of ORG, OX and OX are obtained by the laser tracker 4, and the coordinates of the center of the ball are respectively recorded as O (X, Y, z), X (X, Y, z) and Y (X, Y, z). Then connecting the target ball 2 to the tool calibration module 1, precisely adjusting the mechanical arm to enable the target ball 2 to fall into an ORG hole position on the user calibration module 3, and precisely fine-adjusting the target ball 2 to enable the sphere center coordinate of the target ball 2 to be O (x, y, z), thereby completing the calibration of the origin coordinate of the user coordinate system; precisely adjusting the mechanical arm to enable the target ball 2 to fall into an OX hole position on the user calibration module 3, precisely fine-adjusting the target ball 2 to enable the sphere center coordinate of the target ball 2 to be X (X, y, z), and completing the positive calibration of the X axis of the user coordinate system; and precisely adjusting the mechanical arm to enable the target ball 2 to fall into an OY hole position on the user calibration module 3, precisely fine-adjusting the target ball 2 to enable the center coordinates of the target ball 2 to be Y (x, Y, z), and completing the positive calibration of the Y axis of the user coordinate system, thereby completing the calibration of the user coordinate. Due to the adoption of the laser tracker 4 for positioning, the repeatability of the spatial position can be well ensured.

However, in the actual operation process, the mechanical arm is adjusted to make the target ball 2 just fall into the corresponding hole of the user calibration module 3, so that the implementation process has certain difficulty, and the embodiment also provides another process for user coordinate calibration, and the calibration plane is flexibly moved by the laser tracker 4 to realize user coordinate calibration. The method specifically comprises the following steps: and placing the user calibration module 3 on a calibration plane, and acquiring coordinates of the sphere center of the target ball 2 in a coordinate system of the laser tracker 4 when the target ball 2 is respectively positioned at three hole sites of ORG, OX and OX by using the laser tracker 4, and recording the coordinates of the sphere center as O (X, Y, z), X (X, Y, z) and Y (X, Y, z). Then, the Z values of the three coordinates are subtracted by 50mm to obtain three new coordinate points O ' (X, Y, Z), X ' (X, Y, Z) and Y ' (X, Y, Z), which form a virtual user reference plane, as shown in fig. 6. And connecting the target ball 2 with the tool calibration module 1, and moving the mechanical arm to O ' (X, Y, z), X ' (X, Y, z) and Y ' (X, Y, z) teaching respectively to finish the calibration of the user coordinates. After calibration, the XOY plane of the calibrated user coordinate system is moved downwards by 50mm along the Z-axis, and then the user coordinate system based on the user calibration plane can be established.

The precision fine adjustment of the mechanical arm and the measurement precision of the laser tracker 4 ensure that the coordinate difference is less than 10 mu m when the mechanical arm teaches the same point. The calibration of the user coordinate system based on the laser tracker 4 can better ensure that the established user coordinate system is as consistent as possible. After recalibration of the robot arm, the laser tracker 4 is used to describe the consistency of the operating coordinate system after two calibrations, as shown in table 2.

TABLE 2 post-calibration differences of user coordinates

The mechanical arm calibration system based on the laser tracker 4 provided by the embodiment is characterized in that a design tool calibration module 1 is connected to the tail end of a tool. And (4) by means of the laser tracker 4, taking any point in the space as a calibration point, teaching the point in 5 postures, and completing the tool coordinate calibration. Designing a user calibration module 3 with ORG, OX and OY hole sites, placing the target ball 2 in the ORG, OX and OY hole sites, and acquiring coordinates of each position through a laser tracker 4. The target ball 2 is then placed at the end of the tool calibration module 1, the robot arm is moved to O ' (X, Y, z), X ' (X, Y, z) and Y ' (X, Y, z) teaching respectively, and user coordinate calibration is performed. A virtual user coordinate system is established through the above process. Assuming that the thickness of the user coordinate calibration module is lmm, the XOY surface of the calibrated user coordinate system is moved downwards (50+ l) mm along the Z-axis, and then a user coordinate system based on a calibration plane can be established, i.e. the actual user coordinate system, so that the calibration of the user coordinate and the tool coordinate is realized, the calibration process of the mechanical arm is realized, and the calibration precision and the repeatability are high.

Example 2:

the present embodiment is configured to provide a method for calibrating a robot arm based on a laser tracker, which works with the calibration system described in embodiment 1, and as shown in fig. 7, the calibration method includes the following steps:

step 101: taking any point in space as a calibration point, taking a coordinate system of a laser tracker 4 as a measurement coordinate system, and recording initial sphere center coordinates of the target sphere 2 when the target sphere is positioned at the calibration point;

step 102: according to the sphere center coordinates determined by the laser tracker 4 in real time, adjusting the mechanical arm to enable the target sphere 2 to teach the calibration point in any 5 postures, and completing the calibration of the tool coordinates; in the teaching process of 5 postures, the corresponding sphere center coordinates when the target sphere 2 reaches the calibration point are all the same as the initial sphere center coordinates;

step 103: taking a coordinate system of a laser tracker 4 as a measurement coordinate system, and recording initial spherical center coordinates of the target ball 2 at three hole sites on a user calibration module 3 respectively to obtain initial spherical center coordinates corresponding to the three hole sites respectively;

step 104: according to the sphere center coordinates determined by the laser tracker 4 in real time, the mechanical arms are respectively adjusted to enable the target balls 2 to fall into the hole sites, the target balls 2 are adjusted in the hole sites until the sphere center coordinates of the target balls 2 are the same as the initial sphere center coordinates corresponding to the hole sites, and after the target balls 2 are adjusted in the three hole sites, the calibration of the user coordinates is completed.

According to the mechanical arm calibration method based on the laser tracker, the center coordinates of the target ball are determined in real time by the laser tracker, calibration points are taught by adjusting the mechanical arm in any 5 postures by using a 5-point tool coordinate calibration method according to the center coordinates determined in real time by the laser tracker, calibration of tool coordinates is completed, the target ball falls into three hole sites respectively by adjusting the mechanical arm by using a 3-point user coordinate calibration method, the target ball is adjusted in the hole sites, calibration of the user coordinates is completed, the consistency of the calibration points during calibration is ensured by means of the high-accuracy space positioning capacity of the laser tracker, absolute positioning errors and human errors of the mechanical arm are eliminated, and the calibration precision and the calibration repeatability of the mechanical arm can be improved.

Specifically, as shown in fig. 8, the step 104 may include:

step 1041: marking the initial spherical center coordinates corresponding to the three hole positions as O (X, Y, z), X (X, Y, z) and Y (X, Y, z);

step 1042: adjusting the mechanical arm to enable the target ball 2 to fall into an ORG hole site according to the sphere center coordinate determined by the laser tracker 4 in real time, recording the sphere center coordinate of the target ball 2 at the moment, and judging whether the sphere center coordinate of the target ball 2 is the same as O (x, y, z) or not to obtain a first judgment result;

step 1043: if the first judgment result is negative, adjusting the target ball 2 in the ORG hole site until the sphere center coordinate of the target ball 2 is O (x, y, z);

step 1044: if the first judgment result is yes, adjusting the mechanical arm to enable the target ball 2 to fall into an OX hole site according to the sphere center coordinate determined by the laser tracker 4 in real time, recording the sphere center coordinate of the target ball 2 at the moment, judging whether the sphere center coordinate of the target ball 2 is the same as X (X, y, z) or not, and obtaining a second judgment result;

step 1045: if the second judgment result is negative, adjusting the target ball 2 in the OX hole site until the sphere center coordinate of the target ball 2 is X (X, y, z);

step 1046: if the second judgment result is yes, adjusting the mechanical arm to enable the target ball 2 to fall into an OY hole site according to the sphere center coordinate determined by the laser tracker 4 in real time, recording the sphere center coordinate of the target ball 2 at the moment, and judging whether the sphere center coordinate of the target ball 2 is the same as Y (x, Y, z) or not to obtain a third judgment result;

step 1047: if the third judgment result is negative, adjusting the target ball 2 in the OY hole position until the sphere center coordinate of the target ball 2 is Y (x, Y, z);

step 1048: and if the third judgment result is yes, stopping adjusting, and completing the calibration of the user coordinate.

In this embodiment, the calibration of the user coordinates is performed according to the order of the origin of coordinates, the X axis, and the Y axis, but in the implementation process, the calibration may be performed according to any order, which is not limited in this embodiment. By using the method, the target balls are enabled to fall into three hole sites respectively by adjusting the mechanical arm by using a 3-point user coordinate calibration method according to the sphere center coordinates determined by the laser tracker in real time, the target balls are adjusted in the hole sites, the calibration of the user coordinates is completed, the consistency of calibration points during calibration is ensured by means of the high-accuracy space positioning capacity of the laser tracker, the absolute positioning error and the artificial error of the mechanical arm are eliminated, and the calibration precision and the calibration repeatability of the mechanical arm can be improved.

Example 3:

since the implementation process of adjusting the mechanical arm to make the target ball 2 just fall into the corresponding hole of the user calibration module 3 has a certain difficulty in the actual operation process, this embodiment is used to provide another method for performing user coordinate calibration, and the calibration method works with the calibration system described in embodiment 1, as shown in fig. 9, and the calibration method includes the following steps:

step 201: taking any point in space as a calibration point, taking a coordinate system of a laser tracker 4 as a measurement coordinate system, and recording initial sphere center coordinates of the target sphere 2 when the target sphere is positioned at the calibration point;

step 202: according to the sphere center coordinates determined by the laser tracker 4 in real time, adjusting the mechanical arm to enable the target sphere 2 to teach the calibration point in any 5 postures, and completing the calibration of the tool coordinates; in the teaching process of 5 postures, the corresponding sphere center coordinates when the target sphere 2 reaches the calibration point are all the same as the initial sphere center coordinates;

step 203: taking a coordinate system of a laser tracker 4 as a measurement coordinate system, recording initial sphere center coordinates of the target ball 2 at three hole positions on a user calibration module 3, and recording the initial sphere center coordinates corresponding to the three hole positions as O (X, Y, z), X (X, Y, z) and Y (X, Y, z);

step 204: according to the sphere center coordinates determined by the laser tracker 4 in real time, adjusting the mechanical arm to enable the target sphere 2 to teach to O (X, Y, z-m), X (X, Y, z-m) and Y (X, Y, z-m) respectively, and completing the calibration of user coordinates; where m is any positive value.

Wherein m may be 50 mm.

According to the calibration method provided by the embodiment, when the user coordinates are calibrated, the implementation process that the mechanical arm is adjusted to enable the target ball 2 to just fall into the corresponding hole of the user calibration module 3 has certain difficulty in the actual operation process, so that the mechanical arm is adjusted to enable the target ball 2 to respectively reach O (X, Y, z-m), X (X, Y, z-m) and Y (X, Y, z-m) teaching according to the sphere center coordinates determined by the laser tracker 4 in real time, the calibration of the user coordinates is completed, the implementation difficulty of the calibration method is low, the absolute positioning error and the human error of the mechanical arm can be well eliminated, and the calibration precision and the calibration repeatability of the mechanical arm are improved.

The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other.

The principles and embodiments of the present invention have been described herein using specific examples, which are provided only to help understand the method and the core concept of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the above, the present disclosure should not be construed as limiting the invention.