CN112016216B - Method for determining press-fitting curve inflection point - Google Patents

Abstract

The invention relates to a method for determining a press-mounting curve inflection point, which determines a key area according to the shape of a pressure-displacement curve acquired by a servo press test; reading bottom layer data in a servo press controller, amplifying scattered points in a key area to obtain discrete single points, and marking each point in the key area according to an acquisition sequence; setting the size of a reading frame and the moving mode of a reading area, and setting two parameters of a continuous point Num and a slope threshold k for slope threshold judgment; and putting the reading frame into an enlarged key area, sequentially interpreting the slopes of the two points, performing inflection point interpretation, and definitely identifying the press-mounting inflection point. The method realizes automatic identification of the machine, accurately acquires the required data and forms a statistical evaluation standard; the amount of statistical data is reduced and the accuracy of adjusting the process data is improved.

Description

Method for determining press-fitting curve inflection point

Technical Field

The invention relates to the technical field of press fitting detection, in particular to a method for determining a press fitting curve inflection point.

Background

In the application of the servo press, some key position points are often required to be found on a pressure-displacement curve, for example, a certain key position is pressed, or a certain position stop block is touched, which is called as an inflection point in the industry, and then the next press mounting action is performed. And the servo press controller determines the original data of the key points, namely a curve formed by pressure and displacement data acquired in real time, and finally, the determination process of the key points becomes a curve shape discrimination calculation method.

As shown in fig. 1 and 2, a common pressure displacement curve is in a simplified basic shape, and visual observation shows that the change of feeling is steep and gentle, which are subjective recognition results of human eyes, but the machine cannot realize standardization and quantification, so that the quality of a press fitting result cannot be automatically discriminated.

Disclosure of Invention

The invention provides a method for determining the press fitting inflection point, which aims at solving the problem that the press fitting inflection point in a pressure-displacement curve acquired by servo press test is difficult to determine and definitely identifies the press fitting inflection point.

The technical scheme of the invention is as follows: a method for determining a press-fitting curve inflection point specifically comprises the following steps: 1) Determining a key area according to the shape of a pressure-displacement curve acquired by a servo press test;

2) Reading bottom layer data in a servo press controller, amplifying scattered points in a key area to obtain discrete single points, and marking each point in the key area according to an acquisition sequence;

3) Setting the size of a reading frame and the moving mode of a reading area, and setting two parameters of a continuous point Num and a slope threshold k for slope threshold judgment;

4) Performing inflection point interpretation, which comprises the following specific steps:

4.1 Putting the reading frame into the key area amplified in the step 2), sequentially calculating the 1 st point, the 2 nd point, \ 8230after the reference point and the first point in the reading frame as the reference point, and judging the reference point as an inflection point if the Num slopes are all larger than a slope threshold value k; if the slope of the reference point and the nth point after the reference point is less than the slope threshold k, judging the nth point as a new reference point, wherein n is more than 1 and less than or equal to Num;

4.2 Stop if an inflection point is found in the fetch box, the following points do not participate in the calculation; if no inflection point is found in the window area, the window is moved to the next position in the key area according to the moving mode, and the steps are repeated for judgment until the inflection point is found.

The value range of the continuous point Num is 2-10, and the value range of the slope threshold k is 0.5-10.

The invention has the beneficial effects that: the invention relates to a method for determining the inflection point of a press-fitting curve, which realizes automatic identification of a machine, accurately acquires required data and forms a statistical evaluation standard; the amount of statistical data is reduced and the accuracy of adjusting the process data is improved.

Drawings

FIG. 1 is a simplified diagram of a general pressure-displacement curve;

FIG. 2 is a simplified diagram of a conventional pressure-displacement curve in a basic shape;

FIG. 3 is a diagram illustrating a method for determining a corner of a press-fitting curve according to the present invention;

fig. 4 is a diagram of a method for determining a press-fitting inflection point according to the present invention.

Detailed Description

Data acquisition of a servo press controller is conversion from analog quantity to digital quantity, a coherent curve is seen in an upper graph, bottom layer data in the controller is actually a series of discrete single points, for example, if the sampling rate is 1kHz, 1000 sampling points can be recorded in one second, as shown in fig. 3, a scatter diagram in a key area is amplified, all the points are marked according to the acquisition sequence, the following description is convenient, all the points are named sequentially by using English letters (1000 points are acquired by 1S, and the points cannot be named by using English letters), as shown in fig. 4, corresponding point coordinate corresponding values are shown in table 1, a window area and two key parameters are introduced, the window area is a range in which a user wants to search for the key points, and is only searched in the range, similar to a box area in the previous three graphs, the two parameters are a continuous point number Num judged by a slope threshold value and a slope threshold value k, the two parameters are adjustable in different occasions, generally, the value range of the Num is between 2 and 10, and the value range of the slope threshold value is between 0.5 and 10.

TABLE 1

	x(mm)	y(kN)
			A	0.5	1.5
B	1.2	1.5
			C	1.5	1.6
D	1.6	2.4
			E	2.0	2.0
F	2.2	2.4
			G	2.6	2.4
H	2.7	2.6
			I	2.72	3
J	2.75	4

The following detailed description will be given by taking the number Num of consecutive points as two points and the slope k as 1:

(1) Point A outside the window, no calculation

(2) B is the first point of the entering window, and B is set as a reference point;

(3) Calculating the slope of a BC connecting line of the reference point B and the next point C, wherein k =0.3 is smaller than 1, discarding the point B, and taking the point C as the reference point;

(4) Calculating the slope of the CD connecting line of the new reference point C and the next point D, wherein k =8 is larger than 1, and jumping to the next point E for judgment;

(5) Calculating the slope of a CE connecting line of the reference point C and the point E, wherein k =0.8 is less than 1, and the slope does not satisfy two continuous points, discarding the point C and taking the point E as the reference point;

(6) Calculating the slope of the EF connecting line of the new datum point E and the next point F, wherein k =2 is greater than 1, and jumping to the next point G for judgment;

(7) Calculating the slope of the EG connecting line of the reference point E and the point G, wherein k =0.6 and is less than 1, and the slope does not meet two points, discarding the point E, and taking the point G as the reference point;

(8) Calculating the slope of a GH connecting line between the new reference point G and the next point H, jumping to the next point I when k =2 is greater than 1, and judging;

(9) Calculating the slope of the GI connecting line of the reference point G and the point I, wherein k =5, the condition that two continuous points are more than 1 is met, and the reference point G at the moment is determined as an inflection point;

(10) Stopping when finding the inflection point, and not participating in calculation by the following points;

(11) If no inflection point is found in the window area, the window is moved to the next position, and the steps are repeated for judgment.

The algorithm is clear and definite, can be digitalized and standardized, is suitable for being adopted by any press-fitting control instrument, can finely adjust the final searching position by changing the number Num of continuous points and the slope threshold k at the initial stage of industrial field debugging, and writes and stores the two parameters after meeting the process requirements as a link of a standard production process.

Claims (1)

1. A method for determining a press-fitting curve inflection point is characterized by comprising the following steps:

1) Determining a key area according to the shape of a pressure-displacement curve acquired by a servo press test;

2) Reading bottom layer data in a servo press controller, amplifying scattered points in a key area to obtain discrete single points, and marking each point in the key area according to an acquisition sequence;

3) Setting the size of a reading frame and the moving mode of a reading area, and setting two parameters of a continuous point Num and a slope threshold k for slope threshold judgment;

4) Performing inflection point interpretation, which comprises the following specific steps:

4.1 Putting the reading frame into the key area amplified in the step 2), sequentially calculating the slope of the reference point and the 1 st point after the reference point by taking the first point in the reading frame as the reference point, and judging the slope of a connecting line between the 1 st point after the reference point as a new reference point and the 1 st point after the new reference point if the slope is less than a slope threshold k; judging the slope of the connecting line between the reference point and the 2 nd point after the reference point if the slope of the connecting line between the reference point and the 1 st point after the reference point is greater than a slope threshold k, judging the reference point as an inflection point if the slope of the connecting line between the reference point and the 2 nd point after the reference point is still greater than the slope threshold k, and judging the slope of the connecting line between the reference point and the 2 nd point after the reference point as a new reference point and the slope of the connecting line between the reference point and the 1 st point after the new reference point if the slope of the connecting line between the reference point and the 2 nd point after the reference point is less than the slope threshold k;

4.2 Stop if an inflection point is found in the fetch box, the following points do not participate in the calculation; if no inflection point is found in the window area, the window is moved to the next position in the key area according to the moving mode, and the steps are repeated for judgment until the inflection point is found.

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