CN113029001B - Linear displacement measuring device and method - Google Patents
Linear displacement measuring device and method Download PDFInfo
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- CN113029001B CN113029001B CN202110289414.0A CN202110289414A CN113029001B CN 113029001 B CN113029001 B CN 113029001B CN 202110289414 A CN202110289414 A CN 202110289414A CN 113029001 B CN113029001 B CN 113029001B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
Abstract
The invention belongs to the technical field of photoelectric displacement precision measurement, and discloses a high-precision linear displacement measuring device capable of eliminating cosine errors, which comprises: reading head, scale grating and output cable. Wherein, the reading head contains: the device comprises a transverse sensor, a longitudinal sensor, a parallel light source and a processing circuit; the scale grating includes: transverse code channels and longitudinal identification marked lines. The light emitted by the parallel light source irradiates the scale grating, and the pattern on the scale grating is mapped onto the image sensor on the reading head. The transverse sensor obtains transverse linear displacement by identifying transverse codes; the longitudinal sensor obtains longitudinal displacement by identifying the displacement variation of the longitudinal marked line; and the processing circuit synthesizes the transverse displacement and the longitudinal displacement to obtain the real displacement of the reading head. By adopting a two-dimensional displacement synthesis method, cosine errors caused by different axes of a measuring axis and a grating axis are effectively eliminated, and high-precision linear displacement measurement is realized.
Description
Technical Field
The invention belongs to the technical field of photoelectric displacement precision measurement, and particularly relates to a high-precision linear displacement measuring device and method capable of eliminating cosine errors.
Background
Digital displacement measurement is a high-precision measurement technology integrating light collection machines and electronics, and has become a key technology in the fields of industrial manufacturing, aerospace, military equipment and the like due to the advantages of high precision, high resolution, wide measurement range, easiness in butt joint with digital equipment and the like. With the increasing development of the production and manufacturing industry, higher requirements are put forward on the digital displacement measurement technology, which mainly comprises the following steps: high resolution and high measurement precision. Therefore, the research on the displacement measurement technology with high resolution and high precision is popular in the basic manufacturing research field and has important research value.
Along with the development of novel industrial equipment such as major axis digit control machine tool, traditional incremental displacement measurement equipment has been unable to satisfy the demand of manufacture equipment. Because the absolute linear displacement measurement has the characteristic of directly obtaining the position information when the numerical control system is powered on for the first time, the numerical control system can immediately enter a working state or continue to operate last time without return-to-zero operation, and the working efficiency of the equipment is greatly improved.
During the linear displacement measurement, when the measuring direction of the reading head has an angle with the measuring range direction of the linear grating, a cosine error exists at the moment. How to effectively eliminate cosine error and improve the accuracy of linear displacement measurement is an urgent problem to be solved.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention obtains accurate linear displacement measurement by synthesizing two-dimensional displacement. In order to achieve the purpose, the invention adopts the following specific technical scheme:
a linear displacement measuring device comprising: the scale grating reading device comprises a sliding guide rail, a reading head which is connected with the sliding guide rail in a sliding mode and a scale grating which is fixed on the sliding guide rail and positioned between measuring areas of the reading head;
the sliding guide rail is parallel to the extension direction of the scale grating and is vertical to the coding marking surface of the scale grating;
the reading head acquires the transverse displacement X and the longitudinal displacement delta Y by identifying the coding marked lines on the scale grating;
and calculating to obtain the measurement displacement D after cosine error elimination according to the transverse displacement X and the longitudinal displacement variable delta Y.
Preferably, the reading head comprises: the device comprises a transverse sensor, a longitudinal sensor perpendicular to the transverse sensor, a processing circuit, a parallel light source and a bracket;
the parallel light source is connected with the processing circuit through the bracket;
the transverse sensor and the longitudinal sensor are positioned on the lower side surface of the processing circuit and form a correlation with the parallel light source;
the processing circuit is used for receiving the image data of the transverse sensor and the longitudinal sensor and performing subdivision operation, decoding operation and calculation of the measurement displacement D.
The bracket is connected with the sliding guide rail in a sliding way.
Preferably, the scale grating comprises N transverse coding marked lines and two parallel longitudinal identification marked lines;
the transverse coding marked lines are a group of rectangular light-transmitting marked lines which are coaxial and equidistant and are vertically arranged along the extension direction of the scale grating, and are used for realizing the measurement of the transverse displacement X;
the longitudinal identification marking is parallel to the extension direction of the scale grating and perpendicular to the transverse coding marking, and is used for measuring the longitudinal displacement variation delta Y.
Preferably, the lateral coding reticle comprises a wide reticle and a narrow reticle; the wide marked line represents a coded element '1', the narrow marked line represents a coded element '0', and absolute type coding is realized according to permutation and combination of pseudo-random sequence coding.
Preferably, the width of the wide reticle is not greater than L/N; the width of the narrow reticle is not more than L/2N, and L is the transverse measurement length of the scale grating.
Preferably, the center of the interval between the two longitudinal identification markings coincides with the center of the longitudinal sensor, so that it can be imaged completely on the longitudinal sensor; the interval between the two longitudinal identification marked lines is M.L/N, and M is an integer which is not zero.
Preferably, M ═ 4.
Preferably, the width of the longitudinal identification mark is not greater than 1 mm.
Preferably, the device further comprises a transmission cable which is connected with the reading head and outputs the measured displacement D obtained by calculation processing.
A linear displacement measurement method, comprising:
s1, identifying the coded values represented by the wide marked lines and the narrow marked lines collected by the linear displacement measuring device to obtain a coded value A of the transverse displacement X;
s2, establishing a coordinate system by taking the central point of the transverse sensor as a zero point, and acquiring a subdivision value B of the transverse displacement X, thereby obtaining the transverse displacement X;
s3, establishing a coordinate system by taking the central point of the longitudinal sensor as a zero point, and acquiring the longitudinal displacement Y, so as to acquire the longitudinal displacement variation delta Y:
ΔY＝Y-Y0 (1)
wherein, Y0When the transverse displacement X is equal to 0, calculating the obtained longitudinal displacement;
s4, calculating the measurement displacement D after cosine error elimination by using the following formula:
the invention can obtain the following technical effects:
1. cosine errors are eliminated through a two-dimensional displacement synthesis method, and the accuracy of linear displacement measurement is improved.
Drawings
FIG. 1 is a schematic view of a linear displacement measuring device according to an embodiment of the present invention;
FIG. 2 is a schematic view of a readhead according to one embodiment of this invention;
FIG. 3 is a schematic view of a section of a grating scale encoder reticle of one embodiment of the present invention;
FIG. 4 is a schematic diagram of the calculation of the amount of lateral displacement according to one embodiment of the present invention;
FIG. 5 is a schematic diagram of longitudinal displacement calculation according to one embodiment of the present invention;
FIG. 6 is a schematic diagram of cosine error compensation according to an embodiment of the present invention;
FIG. 7 is a flowchart of a method for calculating cosine error compensation according to an embodiment of the present invention.
Reference numerals:
a reading head 1, a transverse sensor 11, a longitudinal sensor 12, a processing circuit 13, a parallel light source 14, a bracket 15,
A sliding guide rail 2,
A scale grating 3, a transverse coding marking 31, a longitudinal identification marking 32,
A transmission cable 4.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not to be construed as limiting the invention.
The invention aims to provide a linear displacement measuring device and a method, which can obtain accurate linear displacement measurement by synthesizing two-dimensional displacement. The following will describe a linear displacement measuring device provided by the present invention in detail by way of specific embodiments.
As shown in the structure diagram of the device shown in fig. 1, a reading head 1 is slidably connected with a sliding guide rail 2, a scale grating 3 is fixed on the sliding guide rail 2 and is parallel to the extending direction of the sliding guide rail 2, and the encoding mark line surface of the scale grating 3 is perpendicular to the sliding guide rail 2; the reading head 1 acquires the transverse displacement X and the longitudinal displacement delta Y by identifying the coding marked lines on the scale grating 3.
With reference to fig. 2, the reading head 1 comprises a transverse sensor 11 and a longitudinal sensor 12, perpendicular to each other, both located on the lower side of a processing circuit 13, the processing circuit 13 being connected to a collimated light source 14 by means of a support 15, so that the transverse sensor 11 and the longitudinal sensor 12 are in a correlation with the collimated light source 14; the bracket 15 is connected with the sliding guide rail 2, so that the reading head 1 can move on the sliding guide rail 2; the processing circuit 13 is used for receiving the image data of the transverse sensor 11 and the longitudinal sensor 12 and performing subdivision operation, decoding operation and calculation of the measurement displacement D.
In a preferred embodiment of the present invention, referring to fig. 3, the scale grating 3 with a transverse measurement length L comprises N transverse coding markings 31 and two parallel longitudinal identification markings 32; the transverse coding marked lines 31 are a group of rectangular light-transmitting marked lines which are coaxial and equidistant and are vertically arranged along the extension direction of the scale grating 3; the longitudinal identification markings 32 are parallel to the direction of extension of the scale grating 3 and perpendicular to the transverse coding markings 31.
In another embodiment of the present invention, the parallel light emitted from the parallel light source 14 passes through the coding mark on the scale grating 3, the image of the horizontal coding mark 31 is mapped onto the horizontal sensor 11, and the image of the vertical identification mark 32 is mapped onto the vertical sensor 12, so as to realize projection imaging.
With continued reference to FIG. 3, horizontal code markings 31 include a wide marking representing coding element "1" and a narrow marking representing coding element "0", wherein the width of the wide marking is no greater than L/N; the width of the narrow marked line is not more than L/2N, and absolute type coding is realized according to permutation and combination of pseudo-random sequence coding.
The longitudinal identification markings 32 are two mutually parallel light-transmitting markings, the length of which is the same as that of the scale grating 3; the centers of the two longitudinal identification markings 32 should be as far as possible coincident with the centers of the longitudinal sensors 12 so that the longitudinal sensors 12 should be able to completely cover the two longitudinal identification markings 32.
In a preferred embodiment of the present invention, the width of the longitudinal identification mark 32 is not greater than 1mm, and the interval between two longitudinal identification marks 32 is M · L/N, where M is an integer different from zero.
In a preferred embodiment of the present invention, M ═ 4.
Fig. 6 shows the principle of cosine error compensation of the present invention, that is, according to the lateral displacement X and the longitudinal displacement variation Δ Y, the real measured displacement D is synthesized, and the cosine error is eliminated, and a method for measuring a linear displacement according to the present invention is described with reference to fig. 7:
firstly, the processing circuit 13 identifies the "1" and "0" coding values represented by the current marking according to the "width" and "narrow" of the marking in the collected image of the transverse coding marking 31, and then obtains a decoding value A of the transverse displacement X by looking up a table;
secondly, obtaining a subdivision value B of the transverse displacement X;
in a preferred embodiment of the present invention, as shown in the principle of lateral displacement calculation in fig. 4, a coordinate system is established with the center point of the lateral sensor 11 as a zero point, wherein the x-axis of the coordinate system is the pixel position of the lateral sensor 11 and the y-axis is the gray scale value. a is1And a2The centroids of the adjacent graticules on both sides of the coordinate axis, respectively, the lateral displacement component value B can be expressed as:
where η is a quantization value, and the larger the value of η, the larger the subdivision factor can be achieved.
According to the linking of the decoded value A and the subdivided value B, the lateral displacement X can be obtained.
Thirdly, acquiring the longitudinal displacement Y, and acquiring the longitudinal displacement variation delta Y according to the longitudinal displacement Y:
in a preferred embodiment of the present invention, as shown in the schematic diagram of longitudinal displacement amount calculation shown in fig. 5, the longitudinal direction sensor 12 acquires an image of the longitudinal direction identification mark 32, and sends the image information to the processing circuit 13, and calculates the centroid position of the longitudinal direction identification mark 32.
And establishing a coordinate system by taking the central point of the longitudinal sensor 12 as a zero point, wherein the x axis of the coordinate system is the pixel position of the longitudinal sensor 12, and the y axis is a gray value. Assuming that the centers of mass of the two longitudinal recognition index lines 32 are b1 and b2, respectively, the longitudinal displacement amount Y can be expressed as:
when the transverse displacement X is zero, the calculated longitudinal displacement is Y0(ii) a When the displacement is located at other positions, the calculated longitudinal displacement is Y; then, the amount of change in longitudinal displacement is:
ΔY＝Y-Y0 (1)
finally, according to the calculated transverse displacement amount X and longitudinal displacement amount Δ Y, the true measurement displacement amount after cosine error elimination can be obtained as follows:
the measured displacement amount D is outputted by the transmission cable 4.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.
The above embodiments of the present invention should not be construed as limiting the scope of the present invention. Any other corresponding changes and modifications made according to the technical idea of the present invention should be included in the protection scope of the claims of the present invention.
Claims (8)
1. A linear displacement measuring device, comprising: the scale grating measuring device comprises a sliding guide rail, a reading head which is connected with the sliding guide rail in a sliding mode and a scale grating which is fixed on the sliding guide rail and located between measuring areas of the reading head;
the sliding guide rail is parallel to the extension direction of the scale grating and is vertical to the coding reticle plane of the scale grating;
the reading head acquires transverse displacement X and longitudinal displacement delta Y by identifying the coding marked lines on the scale grating;
calculating to obtain a measurement displacement D after cosine error elimination according to the transverse displacement X and the longitudinal displacement variable delta Y;
the reading head comprises: the device comprises a transverse sensor, a longitudinal sensor perpendicular to the transverse sensor, a processing circuit, a parallel light source and a bracket;
the parallel light source is connected with the processing circuit through the bracket;
the transverse sensor and the longitudinal sensor are positioned on the lower side face of the processing circuit and are in an opposite relation with the parallel light source;
the processing circuit is used for receiving the image data of the transverse sensor and the longitudinal sensor to perform subdivision operation, decoding operation and calculation of a measurement displacement D;
the bracket is connected with the sliding guide rail in a sliding way;
the scale grating comprises N transverse coding marked lines and two parallel longitudinal identification marked lines;
the transverse coding marked lines are a group of rectangular light-transmitting marked lines which are coaxial and equidistant and are vertically arranged along the extension direction of the scale grating, and are used for measuring the transverse displacement X;
the longitudinal identification marking is parallel to the extension direction of the scale grating and perpendicular to the transverse coding marking, and is used for measuring longitudinal displacement variation delta Y.
2. The linear displacement measurement device of claim 1, wherein the lateral coding reticle comprises a wide reticle and a narrow reticle; the wide marked line represents a coded element '1', the narrow marked line represents a coded element '0', and absolute type coding is realized according to permutation and combination of pseudo-random sequence coding.
3. The linear displacement measuring device of claim 2, wherein the width of the wide gauge line is no greater than L/N; the width of the narrow graticule is not more than L/2N, and L is the transverse measurement length of the scale grating.
4. The linear displacement measuring device of claim 3, wherein the center of separation of the two longitudinal identification markings coincides with the center of the longitudinal sensor, enabling complete imaging thereof on the longitudinal sensor; the interval between the two longitudinal identification marked lines is M.L/N, and M is an integer which is not zero.
5. The linear displacement measuring device of claim 4, wherein M-4.
6. The linear displacement measuring device of claim 5, wherein the width of the longitudinal identification markings is no greater than 1 mm.
7. The linear displacement measuring device of claim 6, further comprising a transmission cable connected to the reading head for outputting the calculated measured displacement D.
8. A linear displacement measuring method, comprising:
s1, identifying the coded values represented by the wide marked lines and the narrow marked lines collected by the linear displacement measuring device according to any one of claims 1 to 7 to obtain a coded value A of the transverse displacement X;
s2, establishing a coordinate system by taking the central point of the transverse sensor as a zero point, and acquiring a subdivision value B of the transverse displacement X, thereby obtaining the transverse displacement X;
s3, establishing a coordinate system by taking the central point of the longitudinal sensor as a zero point, and acquiring a longitudinal displacement Y, so as to acquire the longitudinal displacement variation delta Y:
ΔY＝Y-Y0 (1)
wherein, Y0When the transverse displacement X is equal to 0, calculating the obtained longitudinal displacement;
s4, calculating the measurement displacement D after cosine error elimination by using the following formula:
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| US20040123684A1 (en) * | 2002-12-17 | 2004-07-01 | Excel Precision Corporation | Digital scale for linear or rotary stage |
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| CN103994723A (en) * | 2014-06-10 | 2014-08-20 | 广东工业大学 | Macro and micro composite grating ruler measurement system based on vertical and horizontal transformation amplification segmentation |
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