CN112595238A - High-low speed compatible linear displacement increment precision measurement method - Google Patents

Abstract

The invention discloses a high-low speed compatible linear displacement increment precision measurement method. Compared with the traditional grating, the grating provided by the invention has the advantages that the manufacturing process complexity, the processing time and the cost are obviously reduced; compared with the traditional grating, the grating has a wider working condition speed range, namely, the grating can normally work under the working condition of higher/lower speed; the traditional fine and dense grating is converted into macroscopic large-interval grating stripes, so that the assembly and debugging complexity is effectively reduced, and the yield is improved; the invention provides a certain absolute positioning capability (absolute positioning, namely the distance from the current position to the zero point position can be directly obtained); the positioning pattern of the present invention is particularly suitable for non-transparent media, such as various metallic materials, which are resistant to impact and vibration.

Description

High-low speed compatible linear displacement increment precision measurement method

Technical Field

The invention relates to the technical field of linear displacement precision measurement, in particular to a high-low speed compatible linear displacement increment precision measurement method.

Background

The precision measurement of the plane moving distance is a common general requirement, is often applied to a closed-loop servo system of a numerical control machine tool, and can be used for detecting the linear displacement or the angular displacement. At present, the industrial field mainly adopts grating ruler measurement, which is also called as a grating ruler displacement sensor or a grating ruler sensor, and the grating ruler displacement sensor or the grating ruler sensor is a measurement feedback device which works by utilizing the optical principle of a grating.

The materials for manufacturing the grating mainly comprise the following 2 materials:

1. reticle glass ruler (effective measuring length used below 3 meters)

2. Reticle steel belt ruler (effective measuring length for more than 3 meters)

Under special working conditions with vibration, impact and high reliability requirements, non-vitreous materials can be used as far as possible. However, the precise metal grating has complex manufacturing process and higher cost. Besides, it has several problems:

1. the grating ruler can only perform incremental measurement of position offset compared with the previous position, namely, after the system is powered on for the first time, the current position cannot be obtained, zero position searching needs to be performed firstly, and then the current position can be obtained by accumulating historical movement data. After the system is powered off and the fault is restarted at any time, the above processes are repeated to obtain the current position information.

2. Measurement errors continue to accumulate. That is, once a positioning error occurs at a certain position, the error is always present and cannot be eliminated, and the positioning error cannot be recovered unless the positioning error passes through the zero position again.

3. The problems of positioning error and positioning failure are easy to occur at extremely high and extremely low moving speeds.

Disclosure of Invention

Aiming at the defects in the prior art, the high-low speed compatible linear displacement increment precision measurement method provided by the invention solves the problem that the precision measurement result of the plane moving distance is inaccurate.

In order to achieve the purpose of the invention, the invention adopts the technical scheme that: a high and low speed compatible linear displacement increment precision measurement method comprises the following steps:

s1, generating photoelectric signals by using the photoelectric tube A and the photoelectric tube B, moving the positioning pattern from a zero position, generating pulse signals after the photoelectric signals pass through the positioning pattern, determining the moving direction according to the time sequence of the pulse signals, accumulating the pulse signals by a measuring system, and setting the accumulated value of the current pulse signals as m;

s2, periodically shooting images through a CCD camera;

s3, taking a central image from the shot image, and sequentially obtaining key points P1, P2, P3 and P4 through an image processing algorithm;

s4, calculating the intersection ratio of the points P1, P2, P3 and P4, and further obtaining the ratio b of the distance of P1P2 to the distance of P1P 3;

s5, calculating the current displacement position of the positioning pattern according to the constant ratio principle, the accumulated value m of the pulse signals and the ratio b;

and S6, adjusting the current displacement position to be an absolute position, and taking the absolute position as a measurement result.

Further: the positioning pattern comprises a plurality of unit bodies, each unit body comprises a grating stripe which is vertically arranged, a straight line L1, a straight line L2 and a straight line L3 which are arranged in parallel are arranged below the grating stripes, the distance between the straight line L1 and the straight line L2 is equal to the distance between the straight line L2 and the straight line L3, the grating stripes are arranged at the right end of the straight line L1, the right end of the straight line L1 is connected with the left end of the straight line L2 through the straight line L, and the straight line L2 form a right-angled triangular grating.

Further: the distance between the straight line L1 and the straight line L2 and the distance between the straight line L2 and the straight line L3 are both a.

Further: the points P1, P2, P3 and P4 are on the same vertical line, and the points P1, P2, P3 and P4 intersect with the line L1, the line L2 and the line L3, respectively.

Further: the calculation formula of the current displacement position of the positioning pattern is as follows:

p＝a*m+b*m

in the above equation, p is the current displacement position of the positioning pattern.

Further: the position of the CCD camera is over against the positions of the photoelectric tube A and the photoelectric tube B.

The invention has the beneficial effects that:

1. compared with the traditional grating, the grating provided by the invention has the advantages that the manufacturing process complexity, the processing time and the cost are obviously reduced;

2. compared with the traditional grating, the grating has a wider working condition speed range, namely, the grating can normally work under the working condition of higher/lower speed;

3. the traditional fine and dense grating is converted into macroscopic large-interval grating stripes, so that the assembly and debugging complexity is effectively reduced, and the yield is improved;

4. the invention provides a certain absolute positioning capability (absolute positioning, namely the distance from the current position to the zero point position can be directly obtained);

5. the positioning pattern of the present invention is particularly suitable for non-transparent media, such as various metallic materials, which are resistant to impact and vibration.

Drawings

FIG. 1 is a schematic diagram of the relative positions of a photocell, a positioning pattern, and a CCD camera according to the present invention;

FIG. 2 is a schematic view of a positioning pattern according to the present invention;

FIG. 3 is a partial enlarged view of the positioning pattern of the present invention;

FIG. 4 is a schematic diagram showing the specific positions of points P1, P2, P3 and P4 in the present invention.

Detailed Description

The following description of the embodiments of the present invention is provided to facilitate the understanding of the present invention by those skilled in the art, but it should be understood that the present invention is not limited to the scope of the embodiments, and it will be apparent to those skilled in the art that various changes may be made without departing from the spirit and scope of the invention as defined and defined in the appended claims, and all matters produced by the invention using the inventive concept are protected.

As shown in fig. 1, a high-low speed compatible linear displacement increment precision measurement method includes the following steps:

s1, generating photoelectric signals by using the photoelectric tube A and the photoelectric tube B, moving the positioning pattern from a zero position, generating pulse signals after the photoelectric signals pass through the positioning pattern, determining the moving direction according to the time sequence of the pulse signals, accumulating the pulse signals by a measuring system, and setting the accumulated value of the current pulse signals as m;

s2, periodically shooting images through a CCD camera;

s3, taking a central image from the shot image, and sequentially obtaining key points P1, P2, P3 and P4 through an image processing algorithm;

s4, calculating the intersection ratio of the points P1, P2, P3 and P4, and further obtaining the ratio b of the distance of P1P2 to the distance of P1P 3;

s5, calculating the current displacement position of the positioning pattern according to the constant ratio principle, the accumulated value m of the pulse signals and the ratio b;

and S6, adjusting the current displacement position to be an absolute position, and taking the absolute position as a measurement result.

As shown in fig. 2, the positioning pattern includes a plurality of unit bodies, each unit body includes a vertically arranged grating stripe, a straight line L1, a straight line L2 and a straight line L3 are arranged below the grating stripe, a distance between the straight line L1 and the straight line L2 is equal to a distance between the straight line L2 and the straight line L3, the grating stripe is arranged at the right end of the straight line L1, the right end of the straight line L1 is connected with the left end of the straight line L2 through the straight line L, and the straight line L2 form a right-angled triangular grating.

The unit cells can be increased/decreased in the pattern of fig. 1 according to the length of the displacement to be measured.

When a transmission mode is adopted on a transparent medium such as glass, the grating stripes are black shading areas. In the non-transparent material trade, the grating stripe region is the cut "hole".

The position of the CCD camera is over against the positions of the photoelectric tube A and the photoelectric tube B. Including general lighting, ensuring that the CCD camera can collect clear images, and generating relative motion between the positioning pattern and the photoelectric tube and CCD camera as shown in FIG. 2 (the photoelectric tube and CCD camera are fixed generally)

As shown in fig. 3, the distance between the straight line L1 and the straight line L2 is a, and the distance between the straight line L2 and the straight line L3 is a. If there is a point P on the straight line L and its perpendicular projection point on L2 is PV, the following relationship holds:

as shown in fig. 4, the points P1, P2, P3 and P4 are on the same vertical line, and the points P1, P2, P3 and P4 intersect with the straight line L1, the straight line L2 and the straight line L3, respectively.

The positioning pattern used in the present invention can be made by a higher precision machine tool, commercial/home printing equipment. May be implemented on transparent/non-transparent media.

Claims (6)

1. A high and low speed compatible linear displacement increment precision measurement method is characterized by comprising the following steps:

s1, generating photoelectric signals by using the photoelectric tube A and the photoelectric tube B, moving the positioning pattern from a zero position, generating pulse signals after the photoelectric signals pass through the positioning pattern, determining the moving direction according to the time sequence of the pulse signals, accumulating the pulse signals by a measuring system, and setting the accumulated value of the current pulse signals as m;

s2, periodically shooting images through a CCD camera;

s3, taking a central image from the shot image, and sequentially obtaining key points P1, P2, P3 and P4 through an image processing algorithm;

s4, calculating the intersection ratio of the points P1, P2, P3 and P4, and further obtaining the ratio b of the distance of P1P2 to the distance of P1P 3;

s5, calculating the current displacement position of the positioning pattern according to the constant ratio principle, the accumulated value m of the pulse signals and the ratio b;

and S6, adjusting the current displacement position to be an absolute position, and taking the absolute position as a measurement result.

2. The high-low speed compatible linear displacement increment precision measurement method according to claim 1, wherein the positioning pattern comprises a plurality of unit bodies, each unit body comprises a vertically arranged grating stripe, a parallel straight line L1, a parallel straight line L2 and a parallel straight line L3 are arranged below the grating stripe, the distance between the straight line L1 and the straight line L2 is equal to the distance between the straight line L2 and the straight line L3, the grating stripe is arranged at the right end of the straight line L1, the right end of the straight line L1 is connected with the left end of the straight line L2 through a straight line L, and the straight line L2 form a right-angle triangular grating.

3. The high-low speed compatible linear displacement increment precision measurement method according to claim 2, characterized in that the distance between the straight line L1 and the straight line L2 and the distance between the straight line L2 and the straight line L3 are both a.

4. The high-low speed compatible linear displacement increment precision measurement method according to claim 3, characterized in that the points P1, P2, P3 and P4 are on the same vertical line, and the points P1, P2, P3 and P4 intersect with the line L1, the line L2 and the line L3 respectively.

5. The high-low speed compatible linear displacement increment precision measurement method according to claim 4, characterized in that the calculation formula of the current displacement position of the positioning pattern is as follows:

p＝a*m+b*m

in the above equation, p is the current displacement position of the positioning pattern.

6. The high-low speed compatible linear displacement increment precision measurement method according to claim 1, characterized in that the position of the CCD camera is over against the positions of a photoelectric tube A and a photoelectric tube B.

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