CN112016216A

CN112016216A - Method for determining press-fitting curve inflection point

Info

Publication number: CN112016216A
Application number: CN202010933216.9A
Authority: CN
Inventors: 潘延庆
Original assignee: Shanghai Xin Riwei Electronic Technology Co ltd
Current assignee: Shanghai Xin Riwei Electronic Technology Co ltd
Priority date: 2020-09-08
Filing date: 2020-09-08
Publication date: 2020-12-01
Anticipated expiration: 2040-09-08
Also published as: CN112016216B

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 clearly 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 is changed into 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, aiming at the problem that the press fitting inflection point in a pressure-displacement curve acquired by a servo press test is difficult to determine, and the press fitting inflection point is definitely identified.

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), taking the first point in the reading frame as a reference point, sequentially calculating the slopes of the reference point and the 1 st point, the 2 nd point, … th point and the Num point after the reference point, and if the Num slopes are all larger than a slope threshold k, judging the reference point as an inflection point; 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) stopping if finding the inflection point in the reading frame, wherein the following points do not participate in 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 basic shape diagram of a conventional 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

The data acquisition of the servo press controller is the conversion from analog quantity to digital quantity, the upper graph looks like a coherent curve, the 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 figure 3, then the scatter diagram in the key area is amplified, all the points are marked according to the acquisition sequence, the following description is convenient, each point is 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 figure 4, the corresponding point coordinate corresponding value is shown in table 1, a window area and two key parameters are introduced, the window area is the range in which a user wants to search the key points, and the window area is only searched in the range, similar to the square area in the previous three graphs, and the two parameters are continuous point Num judged by the slope threshold value, The slope threshold value k can be adjusted in different occasions, the value range of the general Num is 2-10, and the value range of the slope threshold value k is 0.5-10.

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 is outside the window and is not counted

(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 is 0.3 and 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, jumping to the next point E when k is larger than 8 and judging;

(5) calculating the slope of a CE connecting line of the reference point C and the point E, wherein k is 0.8 and is smaller 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, jumping to the next point G when k is larger than 1 and judging;

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

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

(9) calculating the slope of the GI connecting line of the reference point G and the point I, wherein k is 5, the two continuous points are more than 1, 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. 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. The method for determining the press-fitting curve inflection point as claimed in claim 1, wherein the number of the continuous points Num ranges from 2 to 10, and the slope threshold k ranges from 0.5 to 10.