阅读说明：本技术 圆柱坐标测量机转台误差辨识与补偿方法 (Error identification and compensation method for rotary table of cylindrical coordinate measuring machine ) 是由 张旭 杨康宇 朱利民 于 2020-06-09 设计创作，主要内容包括：本发明提供一种圆柱坐标测量机转台误差辨识与补偿方法,包括：在转台中心建立转台坐标系,根据转台几何误差变换矩阵,采用回转轴校准装置、激光干涉仪和球杆仪对六项几何误差进行辨识,操作过程如下：在转台中心建立转台坐标系,转台旋转角度时,得到对应的转台几何误差变换矩阵；分两步对圆柱坐标测量机转台的六项几何误差辨识：a)采用回转轴校准装置和激光干涉仪配合使用对误差项进行辨识；b)采用两个高度下的球杆仪安装位置共五种姿态辨识其余五项几何误差；经过以上两步,获得离散的角度六项几何误差表后,对于任意一个旋转角度,利用线性插值获得角度对应下的六项几何误差。本发明降低了操作难度。(The invention provides a method for identifying and compensating errors of a rotary table of a cylindrical coordinate measuring machine, which comprises the following steps: establishing a turntable coordinate system in the center of the turntable, and identifying six geometric errors by adopting a revolving shaft calibration device, a laser interferometer and a ball rod instrument according to a turntable geometric error transformation matrix, wherein the operation process is as follows: establishing a turntable coordinate system at the center of the turntable, and obtaining a corresponding turntable geometric error transformation matrix when the turntable rotates by an angle; identifying six geometric errors of a rotary table of the cylindrical coordinate measuring machine in two steps: a) identifying error items by matching a revolving shaft calibration device with a laser interferometer; b) identifying the other five geometric errors by adopting five postures of the installation positions of the ball arm instrument at two heights; after the discrete six-term geometric error table of the angle is obtained through the two steps, for any rotation angle, the six geometric errors corresponding to the angle are obtained through linear interpolation. The invention reduces the operation difficulty.)

1. A method for identifying and compensating errors of a rotary table of a cylindrical coordinate measuring machine is characterized by comprising the following steps: establishing a turntable coordinate system in the center of a turntable, and identifying 6 geometric errors by adopting a revolving shaft calibration device, a laser interferometer and a ball rod instrument according to a turntable geometric error transformation matrix, wherein the operation process is as follows:

establishing a turntable coordinate system O-X at the center of the turntable_RY_RZ_RAnd when the rotary table rotates by an angle theta, the corresponding rotary table geometric error transformation matrix is as follows:

identifying six geometric errors of a rotary table of the cylindrical coordinate measuring machine in two steps as follows: the six geometric errors are respectively the translational errors of the revolving shaft X, Y, Z in three directions_xc、_yc、_zcAnd X, Y, Z rotation error in three directions_xc、_yc、_zc；

a) Error term pair by matching use of rotating shaft calibration device and laser interferometer_zcPerforming identification;

b) identifying the other five geometric errors by adopting five postures of the installation positions of the ball arm instrument at two heights;

after the six discrete angle geometric error tables are obtained through the two steps, for any rotation angle alpha, firstly, the rotation angle alpha is adjusted to be in a range from 0 to 360 degrees periodically and is marked as beta, then two discrete angles theta nearest to the beta are searched, and the six geometric errors corresponding to the alpha angle are obtained through linear interpolation.

2. The method for identifying and compensating for errors in a turntable of a cylindrical coordinate measuring machine according to claim 1, wherein the specific process of step a is as follows:

step a1, mounting a rotary shaft calibration device on the rotary table, mounting the rotary shaft calibration device in the center of the rotary table, and fixing;

step a2, placing a laser interferometer to enable the laser interferometer and the revolving shaft calibration device to be at the same height, then placing an interference mirror between the revolving shaft calibration device and the laser interferometer to calibrate a light path;

step a3, starting the matched calibration software, communicating with the rotating shaft calibration device, controlling the rotary table to rotate according to a certain angle theta, rotating 360 degrees clockwise, and rotating 360 degrees anticlockwise;

step a4, collecting data in real time, and averaging the data under the same angle theta to obtain the data under the angle_zcTo this end, error terms of the turntable_zcAnd finishing the identification.

3. The method for identifying and compensating for errors in a turntable of a cylindrical coordinate measuring machine according to claim 1, wherein the specific process of step b is as follows:

step b 1: the ball rod instrument is arranged in the center of the rotary table and is parallel to the Z axis, and the initial position coordinate of the ball at the rotary table end of the ball rod instrument is set as P₁＝(0 0 z₁) (ii) a For each angle theta_jModeling is carried out according to geometric errors of the rotating shaft, and theoretical corresponding point coordinates can be obtained

obtaining the following components:

therefore, the ball rod instrument is respectively arranged along the X-axis direction, the Y-axis direction and the Z-axis direction to obtain the ball height Z of the rotary table end of the ball rod instrument₁Error e in the lower three directions_x1、e_y1、e_z1Can obtain_zc＝e_z1；

Step b2, increasing the height of the ball at the end of the rotating table of the ball arm apparatus, and recording as z₂While still on the center line of the rotation axis, the cue instrument is installed along the X-axis and Y-axis directions, respectively, for each angle theta_jObtaining the ball height z of the ball rod instrument turntable₂Error e in lower X-axis and Y-axis directions_x2And e_y2：

Step b3, for each angle θ_jAnd simultaneously solving the other five geometric errors under the rotation angle by the above formulas (2) - (5) as follows:

Technical Field

The invention relates to the technical field of precision measurement, in particular to a method for identifying and compensating errors of a rotary table of a cylindrical coordinate measuring machine.

Background

The traditional three-coordinate measuring machine can detect the size, the shape and the position of parts and has wide application in the machining and measuring fields of mechanical manufacturing, automobile production line, aerospace and the like. However, for the measurement of revolving body parts, such as engine sleeves, aero-engine blades and the like, a cylindrical coordinate measuring machine can be constructed, the cylindrical coordinate measuring machine comprises two translational shafts and a rotating shaft for measurement, and compared with the traditional three-coordinate measuring machine which is directly provided with a rotary table and is changed into a four-shaft coordinate measuring machine for measurement of revolving body parts, the cylindrical coordinate measuring machine only comprises three motion shafts, one translational shaft is omitted, the structure is more compact, and the cylindrical coordinate measuring machine is more economical.

Because a translation shaft is lacked, the difficulty of identifying geometric errors of the rotary table is high. A great number of previous methods for identifying and compensating geometric errors of the rotary table are based on the fact that the device has X, Y, Z three translational axes, so that data can be conveniently obtained from three spatial directions. The typical equipment is a five-axis numerical control machine tool which is provided with two rotary tables, a ball rod instrument is an instrument which is very important for identifying geometric errors, and high requirements are placed on the real-time position of the ball rod instrument in various identification methods, for example, the ball rod instrument is ensured to be parallel to coordinate axes in real time in the rotating process of the rotary tables, and a cylindrical coordinate measuring machine only needs the ball rod instrument to compensate for 6 geometric errors of the rotary tables of the cylindrical coordinate measuring machine due to the fact that the rotary tables only have two translational axes.

Disclosure of Invention

In order to overcome the defects of high requirements for identifying the real-time position of the geometric error of the turntable of the ball rod instrument, and the like, the turntable error identification and compensation method for the cylindrical coordinate measuring machine is provided.

The embodiment of the invention adopts the technical scheme that:

a method for identifying and compensating errors of a rotary table of a cylindrical coordinate measuring machine comprises the following steps: establishing a turntable coordinate system in the center of the turntable, and identifying six geometric errors by adopting a revolving shaft calibration device, a laser interferometer and a ball rod instrument according to a turntable geometric error transformation matrix, wherein the operation process is as follows:

establishing a turntable coordinate system O-X at the center of the turntable_RY_RZ_RAnd when the rotary table rotates by an angle theta, the corresponding rotary table geometric error transformation matrix is as follows:

identifying six geometric errors of a rotary table of the cylindrical coordinate measuring machine in two steps as follows: the six geometric errors are respectively the translational errors of the revolving shaft X, Y, Z in three directions_xc、_yc、_zcAnd X, Y, Z rotation error in three directions_xc、_yc、_zc；

a) Error term pair by matching use of rotating shaft calibration device and laser interferometer_zcPerforming identification;

b) identifying the other five geometric errors by adopting five postures of the installation positions of the ball arm instrument at two heights;

after the six discrete angle geometric error tables are obtained through the two steps, for any rotation angle alpha, firstly, the rotation angle alpha is adjusted to be in a range from 0 to 360 degrees periodically and is marked as beta, then two discrete angles theta nearest to the beta are searched, and the six geometric errors corresponding to the alpha angle are obtained through linear interpolation.

Further, the specific process of step a is as follows:

step a1, mounting a rotary shaft calibration device on the rotary table, mounting the rotary shaft calibration device in the center of the rotary table, and fixing;

step a2, placing a laser interferometer to enable the laser interferometer and the revolving shaft calibration device to be at the same height, then placing an interference mirror between the revolving shaft calibration device and the laser interferometer to calibrate a light path;

step a3, starting the matched calibration software, communicating with the rotating shaft calibration device, controlling the rotary table to rotate according to a certain angle theta, rotating 360 degrees clockwise, and rotating 360 degrees anticlockwise;

step a4, collecting data in real time, and averaging the data under the same angle theta to obtain the data under the angle_zcTo this end, error terms of the turntable_zcAnd finishing the identification.

Further, the specific process of step b is:

step b 1: the ball rod instrument is arranged in the center of the rotary table and is parallel to the Z axis, and the initial position coordinate of the ball at the rotary table end of the ball rod instrument is set as P₁＝(0 0 z₁) (ii) a For each angle theta_jModeling is carried out according to geometric errors of the rotating shaft, and theoretical corresponding point coordinates can be obtainedAnd the actual coordinate pointAnd P₁The relationships of (a) and (b) are respectively:

obtaining the following components:

therefore, the ball rod instrument is respectively arranged along the X-axis direction, the Y-axis direction and the Z-axis direction to obtain the ball height Z of the rotary table end of the ball rod instrument₁Error e in the lower three directions_x1、e_y1、e_z1Can obtain_zc＝e_z1；

Step b2, increasing the height of the ball at the end of the rotating table of the ball arm apparatus, and recording as z₂While still on the center line of the rotation axis, the cue instrument is installed along the X-axis and Y-axis directions, respectively, for each angle theta_jObtaining the ball height z of the ball rod instrument turntable₂Error e in lower X-axis and Y-axis directions_x2And e_y2：

Step b3, for each angle θ_jAnd simultaneously solving the other five geometric errors under the rotation angle by the above formulas (2) - (5) as follows:

the invention has the advantages that:

1) six geometric errors are divided into two parts for identification, and since the precision of the rotating shaft calibration device is +/-1 arc second, the error items_zcThe identification precision is very high.

2) The ball of the ball rod instrument close to the rotary table is arranged on the axis of the rotary table, and theoretical derivation proves that the installation error basically has no influence on the identification precision, so the operation difficulty is lower.

3) The method can be directly used for compensating the precision of the rotary table after identifying the geometric error of the rotary table.

Drawings

Fig. 1 is a schematic diagram of establishing a coordinate system of a turntable according to an embodiment of the present invention.

FIG. 2 is a diagram of error terms in an embodiment of the present invention_zcSchematic diagram of the identification device.

FIG. 3 shows z in an embodiment of the present invention₁The installation of the height ball arm lowering instrument is schematically shown in three directions.

Detailed Description

The invention is further illustrated by the following specific figures and examples.

The embodiment of the invention provides a method for identifying and compensating errors of a rotary table of a cylindrical coordinate measuring machine, which comprises the following steps:

firstly, a machine coordinate system O-X is established according to a cylindrical coordinate measuring machine_MY_MZ_MDefining two translation axes as X axis and Z axis, respectively, and establishing rotary table coordinate system O-X at rotary table center_RY_RZ_RThe structure is shown in figure 1;

based on a small-error deformation assumption and a rigid homogeneous coordinate transformation principle, a geometric error model of the rotary table is established, and when the rotary table rotates by a certain angle theta, a corresponding geometric error transformation matrix of the rotary table is as follows:

wherein_xc、_yc、_zcRespectively the translational errors of the revolving shaft X, Y, Z in three directions,_xc、_yc、_zcrotation errors in three directions of the rotating shaft X, Y, Z are respectively;

identifying six geometric errors of a rotary table of the cylindrical coordinate measuring machine in two steps as follows:

a) error term pair by matching use of rotating shaft calibration device and laser interferometer_zcPerforming identification;

b) identifying the other five geometric errors by adopting five postures of the installation positions of the ball arm instrument at two heights;

for error term_zcA revolving shaft calibration device and a laser interferometer are matched for use to carry out identification; as shown in fig. 2; the specific process of the step a is as follows:

step a1, mounting the rotating shaft calibration device 2 on the rotary table 1, mounting the rotating shaft calibration device 2 in the center of the rotary table 1 by using a dial indicator, and screwing a clamp for fixing;

step a2, placing the laser interferometer 3 to enable the laser interferometer 3 and the revolving shaft calibration device 2 to be at the same height, then placing the interference mirror 4 between the revolving shaft calibration device 2 and the laser interferometer 3 to calibrate the optical path;

step a3, starting the matched calibration software, communicating with the rotating shaft calibration device through Bluetooth, controlling the rotating table to rotate according to a certain angle theta (such as 10 degrees), clockwise rotating 360 degrees, and then anticlockwise rotating 360 degrees;

step a4, collecting data in real time, and averaging the data under the same angle theta to obtain the data under the angle_zcTo this end, error terms of the turntable_zcAnd finishing the identification.

The remaining five errors are primarily associated with the Z coordinate, as shown in FIG. 3; the specific process of the step b is as follows:

step b 1: the ball rod instrument 5 is arranged in the center of the rotary table 1 and is parallel to the Z axis, and the initial position coordinate of the ball at the end of the rotary table of the ball rod instrument (the end of the ball rod instrument rotates along with the rotary table) is set as P₁＝(0 0 z₁) (ii) a For each angle theta_j(θ_jThe angle interval between the two points is consistent with the angle interval in the step a), and the theoretical corresponding point coordinate can be obtained by modeling according to the geometric error of the rotating shaft(upper right index i represents ideal) and the actual coordinate point

And P₁The relationships of (a) and (b) are respectively:

obtaining the following components:

therefore, the ball rod instrument is respectively arranged along the X-axis, the Y-axis (the direction of the ball rod instrument is vertical to the XZ plane) and the Z-axis direction, and the ball-end height Z of the turntable of the ball rod instrument can be obtained₁Error e in the lower three directions_x1、e_y1、e_z1Obviously, five errors cannot be found at a time, but can be obtained_zc＝e_z1；

Step b2, increasing the height of the ball at the turntable of the ball bar instrument through the cushion block 6, and recording as z₂While still on the center line of the rotation axis, the cue instrument is installed along the X-axis and Y-axis directions, respectively, for each angle theta_jThe ball height z of the ball rod instrument turntable end can be obtained₂Error e in lower X-axis and Y-axis directions_x2And e_y2：

Step b3, for each angle θ_jAnd simultaneously solving the other five geometric errors under the rotation angle by the above formulas (2) - (5) as follows:

the method provided by the embodiment has low requirements on the installation position of the ball arm instrument, and the test difficulty is reduced; the following theoretical derivation proves that the Y-axis direction error can be accurately measured only by approximately ensuring that the ball arm instrument is vertical to the XZ plane; at a height z₁For example, assume that the installation error of the center coordinates of the rotating end of the ball bar apparatus is: (dx dy dz), then the actual position is:^rP＝(dx dy z₁+ dz), for each angle θ_jModeling according to geometric errors of the rotating shaft and theoretically corresponding point coordinatesAnd the actual coordinate pointThe relationship is as follows:

as can be seen from the above equation, since the geometric errors are all relatively small quantities, and the terms related to the mounting errors dx, dy, and dz are all second-order small quantities, they are negligible, which reduces the actual position requirements for mounting the cue instrument.

After the six discrete angle geometric error tables are obtained through the processes, for any rotation angle alpha, firstly, the rotation angle alpha is periodically adjusted to be in a range from 0 to 360 degrees and is marked as beta, then two discrete angles theta nearest to the beta are searched, and the six geometric errors corresponding to the alpha angle are obtained through linear interpolation.

Finally, it should be noted that the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting, and although the present invention has been described in detail with reference to examples, it should be understood by those skilled in the art that modifications or equivalent substitutions may be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, which should be covered by the claims of the present invention.