CN111780967B

CN111780967B - Turntable transmission precision optical composite detection method capable of correcting eccentric error

Info

Publication number: CN111780967B
Application number: CN202010537298.5A
Authority: CN
Inventors: 何涛; 李润林; 杨雷; 孟庆芹; 万力
Original assignee: 724th Research Institute of CSIC
Current assignee: 724th Research Institute of CSIC
Priority date: 2020-06-12
Filing date: 2020-06-12
Publication date: 2022-04-05
Anticipated expiration: 2040-06-12
Also published as: CN111780967A

Abstract

The invention provides an optical composite detection method capable of correcting eccentric error for turntable transmission precision, which comprises the following specific steps: (a) respectively measuring the rotation angle value of the turntable to be measured after the turntable rotates a certain angle by using a laser tracker and an optical dial, and calculating the eccentric error at the moment; (b) calibrating an eccentricity error curve by using the obtained eccentricity error value to obtain an eccentricity error sine function expression when the optical dial is used for measurement; (c) only a series of rotation angles are measured by the optical scale, the readings of the optical scale are corrected by a functional expression of the eccentricity error, and finally the transmission error is calculated. The invention solves the problem of measurement error caused by eccentricity in the traditional optical scale measurement method through the composite detection of two optical methods. The method is suitable for detecting the transmission precision of the large-scale rotary table, does not need to occupy expensive equipment such as a laser tracker for a long time, and has the advantages of low cost, high efficiency, accuracy and the like.

Description

Turntable transmission precision optical composite detection method capable of correcting eccentric error

Technical Field

The invention relates to the field of transmission precision detection of rotary motion, in particular to a method for detecting azimuth transmission precision of a rotary support type rotary table.

Background

The turntable is a bearing mechanism containing various rotary motions, and the transmission precision of the turntable has important significance on the quality of the whole product. Conventional methods of measuring the accuracy of turntable drives typically use faceted prisms or optical scales. However, the former has a small angle measurement range, cannot perform measurement all around, and is mostly used for calibrating the indexing instrument. When the optical scale is installed, the center of the optical scale needs to be ensured to be positioned on the rotating shaft of the turntable, otherwise, an eccentric error is generated; or two detection probes need to be respectively arranged at two ends of the diameter of the optical scale, so that the detection cost is increased.

In recent years, with the development of detection technology, a detection method has been developed in which a normal direction of a reference surface mounted on a turntable and rotating together with the turntable is measured by using a three-coordinate measuring machine or a laser tracker to calculate a transmission error. The method has the advantages of high precision, but the detection efficiency is obviously lower than that of the traditional method, and the detection cost is far more expensive than that of the traditional method.

In view of the above, it is significant to provide an efficient and accurate detection method in the field of detection of transmission errors of a turntable at a low cost.

Disclosure of Invention

Aiming at the problems, the invention provides a low-cost, high-efficiency and accurate detection method, which meets the requirements of detection of the transmission error of the turntable in industrial production.

The technical scheme for realizing the invention is as follows:

an optical composite detection method for the transmission precision of rotary table with the function of correcting the eccentricity error features that the measured value of laser tracker is used to calibrate the eccentricity error curve of optical scale to obtain the sine function expression of the eccentricity error of the read value of optical scale, and the said expression is used to correct the read value of optical scale in subsequent measurement and finally calculate the transmission error. The method comprises the following specific steps:

(a) respectively measuring the rotation angle value of the turntable to be measured after the turntable rotates a certain angle by using a laser tracker and an optical dial, and calculating the eccentric error value at the moment;

(b) calibrating an eccentricity error curve by using the obtained eccentricity error value to obtain an eccentricity error sine function expression when the optical dial is used for measurement;

(c) only a series of rotation angles are measured by the optical scale, the readings of the optical scale are corrected by a functional expression of the eccentricity error, and finally the transmission error is calculated.

Further, in the step (a), after the optical scale and the laser tracker measurement reference frame are installed on the turntable to be measured, the initial reading of the optical scale is read

Then the turntable to be measured is rotated by a certain angle, and the rotation angle theta of the reference frame is measured by a laser tracker₀And reading the optical scale at that time

The eccentricity error value of the optical scale at this time is:

the rotation angle of the reference frame is obtained by collecting the rotation angle of a vector formed by connecting the circle centers of the two reference holes on the reference frame.

Further, the values of the eccentricity error curve in the step (b) at different measuring points can be expressed by a sine function as:

wherein a is the magnitude of the function and,

for measuring point angle values, i.e. the reading of an optical scale,

is the initial phase of the sine function, i.e., the initial reading of the optical scale in step (a). From the calculated eccentricity error value in step (a), the magnitude of the error curve can be calculated:

the eccentricity error curve can then be expressed as:

further, in the step (c), only the optical scale is used for measuring the corresponding angle value of the output end when the input end rotates for a certain angle until the output end rotates for more than 360 degrees; correcting the reading of the output optical scale using the expression of the decentering error function obtained in step (b). If the reading is

Then, the correction value after eliminating the eccentricity error can be calculated by the following formula:

and calculating the corresponding transmission error according to the corrected value after the eccentric error is eliminated.

The invention firstly uses the measured value of the laser tracker to calibrate the eccentricity error curve when the optical scale is measured, and then corrects the actual measured value according to the obtained eccentricity error function expression, thereby solving the problem of measurement error caused by eccentricity in the traditional optical scale measuring method through the composite detection of the two optical methods. The method is suitable for detecting the transmission precision of the large-scale rotary table, does not need to occupy expensive equipment such as a laser tracker for a long time, and has the advantages of low cost, high efficiency, accuracy and the like.

Drawings

FIG. 1 is a graph of eccentricity error.

Fig. 2 is a schematic diagram of detection of transmission accuracy of the rotary table.

Wherein: 1: a turntable; 2: a laser tracker measuring reference frame; 3: an output end optical scale; 4: an output end probe; 5: an input end optical scale; 6: an input end probe; 7: a coupling; 8: a reference hole 1; 9: a reference hole 2.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and examples.

The method comprises the following steps:

1. a measurement reference frame 2 is attached to the work surface of the turntable 1, and an optical scale 3 is attached to the reference frame 2. The output end probe 4 is placed below the optical scale 3 to ensure that the numerical value on the optical scale 3 can be clearly read. The position of the optical scale 3 and the probe 4 cannot be adjusted in all subsequent measurements.

2. And establishing a measurement coordinate system by using a laser tracker, wherein an X-Y plane of the coordinate system is a working plane of the turntable. In the method shown in FIG. 2, the vector direction formed from the reference hole 1 to the reference hole 2 on the measuring reference frame 2 is collected by a laser tracker

. At the same time reading the reading of the probe 4 at that time

。

3. The turntable is rotated by about 90 degrees, and the vector direction formed by the reference hole 1 to the reference hole 2 is collected by a laser tracker

And calculated by measurement software

And

angle theta formed by projection on X-Y plane₀. Reading the reading of the probe 4 at that time

From this, the eccentricity error at this time is calculated as:

4、as shown in FIG. 1, the expression of the sine function according to the eccentricity error curve

At this time

For the initial phase of the eccentricity function, the amplitude of the sine function can be calculated as:

the sinusoidal function expression for eccentricity error can thus be established as:

where delta represents the error in eccentricity and where,

are measured values of different measuring points.

5. The optical scale 5 is mounted on the input shaft by a coupling 7, and the output end probe 6 is placed below the optical scale 5. Selecting a position convenient for reading as a starting point of detection, reading out the numerical value on the optical scales of the input end and the output end when the input end rotates a certain angle until the output end rotates more than 360 degrees, and recording the data of the starting point and all the measuring points.

6. And correcting the measured value in the step 5 by using the eccentricity error curve obtained in the step 4. The correction value after the elimination of the eccentricity error can be calculated by the following formula:

wherein

For each measuring point to measureThe obtained output shaft optical dial reading value.

7. The theoretical output angle value can be calculated according to the transmission ratio of the transmission chain, the corrected measured value is compared with the theoretical value, and the difference value is the transmission error.

Claims

1. A turntable transmission precision optical composite detection method capable of correcting eccentric errors is characterized in that:

step (a): mounting a measuring reference frame and an optical scale on a turntable to be measured;

step (b): reading initial readings of optical scales

And the rotating angle theta of the rotating platform measured by the laser tracker after the rotating platform to be measured rotates about 90 degrees₀And the reading of the optical scale at that time

Step (c): sinusoidal function expression for establishing eccentricity error

Wherein

Angle values for different measurement points;

step (d): reading all the measuring point data of the turntable from the starting point to the point rotating by more than 360 degrees by using an optical dial, and calculating a correction value after eliminating the eccentric error, wherein the calculation formula is

Wherein

Reading values of the output shaft optical dial measured on each measuring point;

a step (e): and comparing the corrected measured value with the theoretical output angle value, and calculating the difference value to obtain the transmission error.

2. The turntable transmission precision optical composite detection method capable of correcting the eccentricity error according to claim 1, is characterized in that: the rotation angle theta of the rotary table measured by the laser tracker in the step (b)₀The angle measurement method is obtained by collecting an included angle formed by the projection of a direction vector formed by the connection line of the centers of circles of two reference holes on a measurement reference frame on a rotating plane.