Five-axis machine tool error measurement method based on ball arm instrument
阅读说明：本技术 一种基于球杆仪的五轴机床误差测量方法 (Five-axis machine tool error measurement method based on ball arm instrument ) 是由 张福民 姚思涵 蒋晓耕 郑继辉 曲兴华 于 2020-07-20 设计创作，主要内容包括：本发明公开了一种基于球杆仪的五轴机床误差测量方法,包括以下步骤：基于螺旋理论构建机床误差模型；建立机床Z轴与B轴匀速联动的数学模型,从而确保测量过程中球杆仪采集数据与实际运动同步,基于该数学模型进行机床代码计算；对机床误差进行测量。对球杆仪测得数据进行误差解耦,解得两轴联动测量过程中的几何误差。本发明方法实现了机床Z轴与B轴几何误差的同时测量,从而极大地提高了测量效率。(The invention discloses a five-axis machine tool error measuring method based on a ball arm instrument, which comprises the following steps of: constructing a machine tool error model based on a spiral theory; establishing a mathematical model for uniform-speed linkage of a Z axis and a B axis of the machine tool so as to ensure that the data collected by the ball arm instrument is synchronous with the actual motion in the measuring process, and calculating the machine tool code based on the mathematical model; and measuring the machine tool error. And (4) carrying out error decoupling on the measured data of the ball arm instrument, and solving the geometrical error in the two-axis linkage measurement process. The method realizes the simultaneous measurement of the geometrical errors of the Z axis and the B axis of the machine tool, thereby greatly improving the measurement efficiency.)
1. A five-axis machine tool error measuring method based on a ball arm instrument is characterized by comprising the following steps:
step 1, constructing a machine tool error model based on a spiral theory;
step 2, establishing a mathematical model for uniform-speed linkage of a Z axis and a B axis of the machine tool, so as to ensure that the data collected by the ball arm instrument is synchronous with the actual motion in the measuring process, and calculating the machine tool code based on the mathematical model;
step 3, measuring the machine tool error; and (4) carrying out error decoupling on the data measured by the ball rod instrument, and solving the geometrical error in the two-axis linkage measurement process.
2. The five-axis machine tool error measurement method based on the ball arm instrument as claimed in claim 1, wherein in the step 1, a machine tool error model is constructed based on a spiral theory, and the method comprises the following steps:
step 1.1, in the method of the invention, only the movements of the machine tool Z-axis and B-axis are involved, so the kinematic model of the machine tool is as follows:
wherein
step 1.2, introducing a geometric error into a machine tool model through left-multiplication error rotation; for the Z axis as an example, the geometric error can be expressed as:
whereinIs the error rotation quantity of the Z axis,
obtaining a geometric error model of the five-axis machine tool by left-multiplying the error rotation:
wherein
3. The five-axis machine tool error measurement method based on the ball rod instrument as claimed in claim 1, wherein in the step 2, a mathematical model for uniform-speed linkage of the Z axis and the B axis of the machine tool is established, so that the synchronization of the data collected by the ball rod instrument and the actual motion in the measurement process is ensured, and the machine tool code calculation is performed based on the mathematical model, and the method comprises the following steps:
step 2.1, in the measuring process, the Z axis performs linear reciprocating motion of 0 to +400, the B axis performs rotary motion of 0 to 90 degrees, a ball bar instrument with the rod length of 400mm is selected, and a machine tool coordinate system is defined in the rotary center of the B axis; in the measuring process, the distance between the tool cup of the main shaft of the ball arm apparatus and the tool cup of the base is ensured to be 400mm constantly so as to adapt to the length of the ball arm apparatus; z-axis displacement Z and B-axis rotation angle theta of machine toolBHave the following relationship between:
2.2, modeling the movement track of the cutter relative to a workpiece coordinate system in the process of linkage of the Z axis and the B axis based on a spiral theory, wherein a machine tool model is as follows:
wherein
step 2.3, the experiment for realizing the linkage of the Z axis and the B axis is carried outIn the process, the data acquired by the sphere bar instrument are synchronous with the actual motion, and the Z axis and the B axis need to be linked at a constant speed, so that the linkage track of the Z axis and the B axis is divided equally; using MATLAB to carry out simulation, obtaining a quarter circular arc with the radius of 400mm as the motion track of a machine tool cutter relative to a workpiece coordinate system, and dividing the circular arc equally according to a central angle, wherein the coordinate of an equant point corresponding to the central angle theta is (400sin theta, 400cos theta); meanwhile, the coordinate of the dividing point is (-400sin theta) according to the position of the tool relative to the coordinate system of the workpieceB，-Z-400cosθB) (ii) a In the Z-axis and B-axis linkage experiment, the angle theta and the B-axis rotation angle thetaBThere are cases where the absolute values are equal; the uniform linkage of the Z axis and the B axis can be realized by equally dividing the absolute value of the angle of the B axis.
4. The five-axis machine tool error measurement method based on the ball bar instrument as claimed in claim 1, wherein in the step 3, the machine tool error is measured, and the measured data of the ball bar instrument is subjected to error decoupling, and the method comprises the following steps:
step 3.1, before measurement, calibrating the tool cup of the main shaft of the sphere bar instrument and the tool cup of the base; placing a ball arm instrument base on the pan-tilt head, detecting the position of the ball arm instrument base by using a probe, and detecting the bias condition of the spindle tool cup by using a dial indicator;
3.2, performing a Z-axis and B-axis linkage experiment by compiling machine tool codes; in order to avoid collision between the main shaft of the machine tool and the ball arm instrument, the B shaft only rotates to minus 60 degrees from 0 degree;
3.3, decoupling geometric errors in the linkage process of the Z axis and the B axis; in the measuring process, the actual position of the cutter relative to the workpiece coordinate system is the actual club length of the club instrument;
wherein L isDBBNamely the club length data measured by the club instrument;
by substituting the measurement data of the ball arm apparatus, L can be constructedDBBOver-determined square with geometric errorA program group; the system of equations is simplified as function f (x):
solving an overdetermined equation set based on a particle swarm algorithm; the global optimal solution of the equation set is a geometric error numerical value obtained by error decoupling.
Technical Field
The invention relates to the technical field of five-axis machine tool error measurement, in particular to a five-axis machine tool error measurement method based on a ball arm instrument.
Technical Field
Compared with a three-axis machine tool, the five-axis machine tool is more complex in structure, extra geometric errors are introduced into the five-axis machine tool through the two rotating axes, and meanwhile, the linear axis and the rotating axes are also in error coupling, so that the precision of the machine tool is greatly influenced. Therefore, in order to ensure the accuracy of the machine tool, the geometric errors of the linear axis and the rotating axis need to be measured.
The existing error measurement method cannot simultaneously measure the errors of the linear shaft and the rotating shaft. Therefore, the method for efficiently measuring the errors of the linear shaft and the rotating shaft is provided, so that the simultaneous measurement of the linear shaft and the rotating shaft is realized.
Disclosure of Invention
The invention aims to provide a five-axis machine tool error measurement method based on a ball rod instrument, which can realize the measurement of the geometric errors of the Z axis and the B axis of a machine tool based on the ball rod instrument. The invention is beneficial to realizing the quick measurement of the machine tool error, thereby improving the measurement efficiency.
The five-axis machine tool error measuring method based on the ball arm instrument comprises the following steps:
step 1, constructing a machine tool error model based on a spiral theory.
And 2, establishing a mathematical model for the uniform-speed linkage of the Z axis and the B axis of the machine tool, so as to ensure that the data collected by the ball arm instrument is synchronous with the actual motion in the measuring process, and calculating the machine tool code based on the mathematical model.
And 3, measuring the error of the machine tool. And (4) carrying out error decoupling on the measured data of the ball arm instrument, and solving the geometrical error in the two-axis linkage measurement process.
In the step 1, a five-axis machine tool geometric error model is established based on a spiral theory, and the method comprises the following steps:
step 1.1, in the method of the invention, only the movements of the machine tool Z-axis and B-axis are involved, so the kinematic model of the machine tool is as follows:
wherein
And step 1.2, introducing a geometric error into the machine tool model by left-multiplying the error rotation. Taking the Z axis as an example, the geometric error can be expressed as:
wherein
Obtaining a geometric error model of the five-axis machine tool by left-multiplying the error rotation:
wherein
Further, a mathematical model for uniform-speed linkage of the Z axis and the B axis of the machine tool is established in the step 2, so that the synchronization of the data collected by the ball rod instrument and the actual motion in the measuring process is ensured, and the machine tool code calculation is carried out based on the mathematical model, and the method comprises the following steps:
step 2.1, in the measuring process, the Z axis performs linear reciprocating motion of 0 to +400, and the B axis performs return motion of 0 to 90 degreesRotating and selecting a ball bar instrument with the length of 400mm, wherein a machine tool coordinate system is defined in a B-axis rotation center. In the measuring process, the distance between the tool cup of the main shaft of the ball arm apparatus and the tool cup of the base is ensured to be 400mm constantly so as to adapt to the length of the ball arm apparatus. Z-axis displacement Z and B-axis rotation angle theta of machine toolBHave the following relationship between:
2.2, modeling the movement track of the cutter relative to a workpiece coordinate system in the process of linkage of the Z axis and the B axis based on a spiral theory, wherein a machine tool model is as follows:
whereinThe position of a machine tool cutter relative to a workpiece coordinate system in a Z-axis and B-axis linkage experiment is as follows:
and 2.3, in order to realize the synchronization of the data collected by the ball arm instrument and the actual motion in the Z-axis and B-axis linkage experiment process, the Z-axis and the B-axis need to be linked at a constant speed, so that the linkage tracks of the Z-axis and the B-axis are equally divided. And (3) simulating by using MATLAB to obtain a quarter circular arc with the radius of 400mm of the motion track of the machine tool cutter relative to the workpiece coordinate system, and equally dividing the circular arc according to the central angle, wherein the coordinate of an equally divided point corresponding to the central angle theta is (400sin theta, 400cos theta). Meanwhile, the coordinate of the dividing point is (-400sin theta) according to the position of the tool relative to the coordinate system of the workpieceB，-Z-400cosθB)。
In the Z-axis and B-axis linkage experiment, the angle theta and the B-axis rotation angle thetaBThere are cases where the absolute values are equal. The Z axis can be realized by equally dividing the absolute value of the angle of the B axisIs linked with the B shaft at a constant speed. Calculating to obtain the distance d between every two points in the linkage process of the Z axis and the B axisZB0.6981mm, a uniform motion of the measuring path is effectively achieved.
Further, the machine tool error is measured in step 3. The method comprises the following steps of performing error decoupling on measured data of the ball arm instrument, solving a geometric error in the two-axis linkage measurement process, and comprising the following steps:
and 3.1, calibrating the tool cup of the main shaft of the sphere bar instrument and the tool cup of the base before measurement. The ball arm instrument base is placed on the pan-tilt head, the position of the ball arm instrument base is detected by the probe, and the bias condition of the spindle tool cup is detected by the dial indicator.
And 3.2, compiling machine tool codes to perform a Z-axis and B-axis linkage experiment. In order to avoid collision between the main shaft of the machine tool and the ball arm instrument, the B shaft only rotates from 0 degree to-60 degrees.
And 3.3, decoupling the geometric errors in the linkage process of the Z axis and the B axis. In the measuring process, the actual position of the cutter relative to the workpiece coordinate system is the actual club length of the club instrument.
Wherein L isDBBNamely the club length data measured by the club instrument.
By substituting the measurement data of the ball arm apparatus, L can be constructedDBBAnd geometric error. The system of equations is reduced to function f (x).
And solving an overdetermined equation set based on a particle swarm algorithm. The global optimal solution of the equation set is a geometric error numerical value obtained by error decoupling.
The invention relates to a five-axis machine tool error measuring method based on a ball arm instrument, which has the following specific beneficial effects:
according to the invention, the geometric errors of the Z axis and the B axis of the machine tool are measured simultaneously, so that the measurement efficiency is greatly improved. Compared with the traditional error measurement method, the method has the advantages of high measurement precision and good practicability.
Drawings
FIG. 1 is a diagram of a five-axis machine tool.
FIG. 2 is a schematic view of Z-axis geometric errors.
FIG. 3 is a schematic view of the linkage relationship between the Z axis and the B axis.
FIG. 4 is a schematic diagram of a measurement experiment in an embodiment of the method of the present invention.
FIG. 5 is a graph of ball bar measurement data for an example of the method of the present invention.
FIG. 6 is a flowchart of an error decoupling method in an embodiment of the method of the present invention.
Detailed Description
The invention is further described with reference to the following figures and specific examples.
FIG. 1 is a schematic diagram of a five-axis machine tool, which is taken as an example to illustrate the method of the present invention.
In the step 1, a five-axis machine tool geometric error model is established based on a spiral theory, and the method comprises the following steps:
step 1.1, in the method of the invention, only the movements of the machine tool Z-axis and B-axis are involved, so the kinematic model of the machine tool is as follows:
whereinAndrepresenting the initial position of the tool and workpiece relative to the machine coordinate system in an ideal case,
And step 1.2, introducing a geometric error into the machine tool model by left-multiplying the error rotation. Taking the Z axis as an example, the geometric error can be expressed as:
whereinIs the error rotation quantity of the Z axis,andindicating the direction error of the Z-axis in the a-axis and the B-axis as shown in fig. 2.
Obtaining a geometric error model of the five-axis machine tool by left-multiplying the error rotation:
wherein
Step 2, establishing a mathematical model for uniform-speed linkage of a Z axis and a B axis of the machine tool so as to ensure that the data collected by the ball arm instrument is synchronous with the actual motion in the measuring process, and calculating the machine tool code based on the mathematical model, wherein the mathematical model comprises the following steps:
and 2.1, in the measurement process, the Z axis performs linear reciprocating motion of 0 to +400, the B axis performs rotary motion of 0 to 90 degrees, a ball bar instrument with the rod length of 400mm is selected, and a machine tool coordinate system is defined in the rotary center of the B axis, as shown in the attached figure 3. In the measuring process, the distance between the tool cup of the main shaft of the ball arm apparatus and the tool cup of the base is ensured to be 400mm constantly so as to adapt to the length of the ball arm apparatus. Z-axis displacement Z and B-axis rotation angle theta of machine toolBHave the following relationship between:
2.2, modeling the movement track of the cutter relative to a workpiece coordinate system in the process of linkage of the Z axis and the B axis based on a spiral theory, wherein a machine tool model is as follows:
wherein
and 2.3, in order to realize the synchronization of the data collected by the ball arm instrument and the actual motion in the Z-axis and B-axis linkage experiment process, the Z-axis and the B-axis need to be linked at a constant speed, so that the linkage tracks of the Z-axis and the B-axis are equally divided. And (3) simulating by using MATLAB to obtain a quarter circular arc with the radius of 400mm of the motion track of the machine tool cutter relative to the workpiece coordinate system, and equally dividing the circular arc according to the central angle, wherein the coordinate of an equally divided point corresponding to the central angle theta is (400sin theta, 400cos theta). Meanwhile, the coordinate of the dividing point is (-400sin theta) according to the position of the tool relative to the coordinate system of the workpieceB，-Z-400cosθB)。
In the Z-axis and B-axis linkage experiment, the angle theta and the B-axis rotation angle thetaBThere are cases where the absolute values are equal. The uniform linkage of the Z axis and the B axis can be realized by equally dividing the absolute value of the angle of the B axis. Calculating to obtain the distance d between every two points in the linkage process of the Z axis and the B axisZB0.6981mm, a uniform motion of the measuring path is effectively achieved.
And 3, measuring the machine tool error. The method comprises the following steps of performing error decoupling on measured data of the ball arm instrument, solving a geometric error in the two-axis linkage measurement process, and comprising the following steps:
and 3.1, calibrating the tool cup of the main shaft of the sphere bar instrument and the tool cup of the base before measurement. The ball arm instrument base is placed on the pan-tilt head, the position of the ball arm instrument base is detected by the probe, and the bias condition of the spindle tool cup is detected by the dial indicator.
And 3.2, writing machine tool codes, and performing a Z-axis and B-axis linkage experiment shown in the attached figure 4. In order to avoid collision between the main shaft of the machine tool and the ball arm instrument, the B shaft only rotates from 0 degree to-60 degrees, and the experimental result is shown in figure 5.
And 3.3, decoupling the geometric errors in the linkage process of the Z axis and the B axis. In the measuring process, the actual position of the cutter relative to the workpiece coordinate system is the actual club length of the club instrument.
Wherein L isDBBNamely the club length data measured by the club instrument.
By substituting the measurement data of the ball arm apparatus, L can be constructedDBBAnd geometric error. The system of equations is reduced to function f (x).
Solving an over-determined equation set based on a particle swarm algorithm, wherein the flow of the error decoupling method is shown in the attached figure 6. The global optimal solution of the equation set is a geometric error numerical value obtained by error decoupling.
The invention finally obtains 6 geometric errors of the Z axis and the B axis of the machine tool. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention, as any modifications, equivalent substitutions, improvements and the like, which are within the spirit and principle of the invention, are intended to be covered by the scope of the invention.