CN-119407072-B - Sand wire cutting bent wire servo control method based on visual detection

CN119407072BCN 119407072 BCN119407072 BCN 119407072BCN-119407072-B

Abstract

The invention discloses a sand line cutting bent wire servo control method based on visual detection, which belongs to the technical field of sand line cutting and comprises the steps of calibrating a sand line angle after verticality calibration to be a zero angle gamma, setting an expected return straight angle theta and a bent wire limiting angle alpha. Uploading the visual detection image of the sand line processing area to an upper computer analysis program, and setting the included angle between the sand line and the zero angle line in the image as a wire bending angle. When the angle of the processed bent wire is increased and exceeds the set bent wire limiting angle alpha, the lower computer is controlled to disconnect the sampling circuit, the feeding of the machine tool is stopped, the wire conveying system is kept to work, and the sand wire is continuously straightened. When the bent wire angle is smaller than the expected return straight angle theta, the lower computer is controlled to conduct the sampling circuit, and feeding of the machine tool is continued. According to the invention, the bending angle is used as a feedback signal, and the feeding start and stop of the machine tool are realized by controlling the on-off of the sampling circuit, so that the bending servo control is realized. The method can effectively reduce the processing error caused by wire bending and the problem of wire breakage caused by wire bending.

Inventors

LIU ZHIDONG
ZENG XIONGHUI
XIA SIWEI

Assignees

南京航空航天大学

Dates

Publication Date: 20260508
Application Date: 20241204

Claims (10)

1. A sand line cutting curved wire servo control method based on visual detection is characterized in that: (a) Initializing parameters and connections of the industrial CMOS camera to ensure that the camera correctly collects and analyzes images; (b) Setting three angle parameters of a zero angle gamma, an expected return angle theta and a limiting angle alpha as the basis of feeding control of the sand wire cutting machine, wherein the zero angle gamma is an angle taking the angle between the sand wire and the vertical direction at the moment as the basis after the perpendicularity of the sand wire is calibrated, the expected return angle theta, the limiting angle alpha and the wire bending angle are all deviation angles of the sand wire and the zero angle gamma under a certain wire bending degree, and mathematical comparison among the expected return angle theta, the limiting angle alpha and the wire bending angle is the absolute value of the angle for comparison; (c) When the sand wire cutting machine tool is continuously fed for processing, the industrial CMOS camera continuously collects images and analyzes the angle deviation between the bent wire angle and the zero angle gamma of the sand wire in the images; (d) The wire bending angle of the sand wire is continuously compared with the limit angle alpha, when the wire bending angle is smaller than the limit angle alpha, an upper computer sends a command to a lower computer, and the sampling voltage is required to be larger than the conduction threshold voltage of the sampling circuit so as to keep the sand wire cutting machine tool to continuously feed; (e) The wire bending angle of the sand wire is continuously compared with the limit angle alpha, when the wire bending angle is larger than or equal to the limit angle alpha, an upper computer sends a command to a lower computer, the sampling voltage is required to be smaller than the conduction threshold voltage of the sampling circuit so as to ensure that the sand wire cutting machine tool stops feeding, and a wire conveying system needs to keep continuously working; (f) The continuous operation of the wire conveying system can gradually reduce the wire bending angle, when the wire bending angle is reduced to be smaller than the expected return straight angle theta, the upper computer sends a command to the lower computer, and the sampling voltage is required to be larger than the conduction threshold voltage of the sampling circuit so as to ensure that the sand wire cutting machine tool continues to feed; (g) Continuously collecting, analyzing and processing the curved wire image of the sand wire, and controlling the start and stop of feeding of the sand wire cutting machine tool according to the analysis result until the processing is completed.
2. The sand wire cutting bent wire servo control method according to claim 1, wherein the connection of the industrial CMOS camera and the upper computer is configured before processing, and the position of the industrial CMOS camera is determined, so that the bent wire angle of the sand wire can be continuously collected under a good light source.
3. The sand wire cutting curved wire servo control method according to claim 1, comprising an image graying processing unit, an image binarization processing unit, a contour detection unit and a noise processing unit, wherein the sand wire curved wire image is continuously subjected to acquisition, graying, contour extraction and noise reduction.
4. The method for servo control of the curved wire of the sand wire cutting machine according to claim 1, wherein the method is characterized in that after a curved wire image of the sand wire is collected, immediately analyzing and processing, and sending a signal for controlling the start and stop of the cutting machine of the sand wire to a lower computer, wherein the sampling rate of the curved wire image of the sand wire must be greater than 25 pieces/second, the processing speed of the curved wire image of the sand wire must be greater than or equal to the collecting speed of the curved wire image of the sand wire, and the response speed of the lower computer should be far greater than the processing speed of the curved wire image of the sand wire, so that the change condition of the sand wire can be recorded in real time and feedback can be made.
5. The method according to claim 1, wherein only contour analysis and edge analysis of the position of the sand wire should be analyzed during the sand wire bending image processing, and other positions should be distinguished or isolated.
6. The method for servo control of the curved wire of the sand wire cutting according to claim 1, wherein setting the angle parameters for controlling the curved wire of the sand wire comprises collecting the angle between the sand wire and the vertical direction in the image of the curved wire of the sand wire once after the sand wire is aligned to be vertical, determining the angle as the zero angle gamma of the sand wire, setting an angle value as the basis for limiting the maximum value of the curved wire degree, and setting an angle value as the judgment basis for determining the return straight angle theta of the sand wire.
7. The sand wire cutting bent wire servo control method according to claim 1, wherein the zero angle γ should be small enough to judge the positive and negative of the bent wire angle, the desired return angle θ should be greater than or equal to the zero angle γ, and the limit angle α should be significantly greater than the desired return angle θ.
8. The sand wire cutting bent wire servo control method according to claim 1 is characterized in that when the bent wire angle is smaller than a limiting angle alpha, the sampling voltage of the sand wire cutting machine tool can be continuously larger than or equal to the conducting threshold voltage of a sampling circuit, so that the sand wire cutting machine tool can continuously feed and process, and when the bent wire angle is larger than or equal to the limiting angle alpha, the sampling voltage of the sand wire cutting machine tool is smaller than the conducting threshold voltage of the sampling circuit, the sand wire cutting machine tool stops feeding and keeps the wire conveying system continuously working.
9. The method for servo control of wire bending of a sand wire cutting machine according to claim 1, wherein the industrial CMOS camera is used for acquiring wire bending images of the sand wire in at least two directions in a plane in which an X feed direction and a Y feed direction of the sand wire cutting machine are located.
10. The method of claim 1, wherein the sampling circuit is provided with a voltage stabilizing element as a switch for turning on or off the circuit, and the sampling circuit is one of a control basis for feeding speed or starting and stopping of the wire-cut machine.

Description

Sand wire cutting bent wire servo control method based on visual detection Technical Field The invention relates to the technical field of servo control of numerical control machine tools, in particular to a sand wire cutting machine tool bent wire servo control method based on visual detection. Background The sand wire cutting technology is a high-precision material processing method and is widely applied to precision processing of hard and brittle materials such as semiconductors, photovoltaics, sapphires and the like. This technique utilizes fine diamond particles embedded in a wire to physically cut the material by a high-speed moving sand line. Since the sand line is a flexible cutting tool, wire bending during processing is unavoidable, and the effect of the wire bending is often negative. When the cutting line is bent, the cutting path may deviate from a predetermined design trajectory, resulting in an increase in cutting size and shape errors. This is not acceptable for the manufacture of products such as semiconductor wafers, photovoltaic wafers, etc. that require high precision. Curved cut lines may cause waviness, scratches or other irregular surface defects to the cut surface, which not only affect the appearance of the product, but may also reduce its performance, particularly in optical applications. At present, the common detection method is indirect detection, for example, by establishing a model of deflection and cutting resistance of the sand line, and a light projection detection method based on a curved wire detection method for detecting the position of the sand line is provided. The operation scheme of the detection control system is designed based on the pressure detection between the sand line and the workpiece in the processing process, and the operation scheme comprises pressure information acquisition, transmission, processing, feedback control and the like, so that the sand line bending quantity can be detected and controlled in real time in the processing process. These methods do not intuitively exhibit the degree of wire bending and are difficult to put into practical use in the processing field. There are also some methods for directly detecting the bending degree, and the prior art (see patent inventor: luo Fuyuan, a wire cutting bending detection method based on auxiliary parallel electrodes, CN 110434415B) provides a method for placing a wire or ribbon auxiliary electrode parallel to the cutting wire right behind the cutting direction of the cutting wire, and determining whether the cutting wire is bent or not by measuring the change of the resistance between the cutting wire and the auxiliary electrode. The technology only carries out qualitative analysis on the bending degree of the sand line, quantitative and accurate detection cannot be carried out, and the technology does not carry out further feedback control after detecting the bent wire. Disclosure of Invention The invention aims to: The invention provides a sand line cutting wire bending servo control method based on visual detection, which is used for solving the problems of high difficulty in detecting the wire bending state of a sand line, non-visual detection angle, no targeted feedback control and the like. Specifically, the invention monitors the bending state of the sand line in real time by introducing a high-precision visual detection system, and feeds back the detection result to a servo control system. The servo control system dynamically adjusts the start and stop of feeding of the machine tool according to the visual detection data, and ensures that the wire rod is always kept in an ideal state, thereby improving the cutting precision and stability. The method can improve the cutting precision of the sand wire cutting and the surface quality of the workpiece, and reduce the wire breakage problem caused by overlarge wire bending angle of the sand wire. In order to achieve the purpose, the following technical scheme is adopted: The visual detection-based sand wire cutting bent wire servo control method has the working flow shown in figure 1, and comprises the steps of firstly initializing and configuring an industrial CMOS camera to be connected with an upper computer, selecting at least two proper camera positions in different directions, and ensuring that the camera is focused on a sand wire. When an industrial CMOS camera acquires a picture, the picture is subjected to gray level processing, binarization processing, contour detection, noise reduction processing and angle analysis, and then an image is acquired again. Setting a zero angle gamma, an expected return angle theta and a limiting angle alpha as the basis of feeding control of the sand line cutting machine tool according to the cutting precision and requirements. And when the wire bending angle is greater than or equal to the limiting angle alpha, the lower computer controls the supply voltage to be smaller than the threshold voltage of the