JPH04238205A - Welding position detecting device - Google Patents

Abstract

PURPOSE:To detect a welding position with high precision by preventing the detection error of the welding position caused by the mixing of image noise due to secondary reflection or spattering light at the time of welding via a laser beam. CONSTITUTION:The fan-shaped light is cast on the welding section of a work, the reflected light is received by an imaging camera, a feature point is extracted to detect a weld position, the average value and the difference of the image intensity for each scanning data are calculated, and the weld position is detected from the maximum value.

Description

[Detailed description of the invention]

[Purpose of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a welding position detection device used in a laser welding machine.

0002

2. Description of the Related Art When welding with a laser welding machine, the welding position is detected. In this case, in order to follow the position of the weld line that has changed due to processing errors, positioning accuracy, thermal strain during welding, etc. of the workpiece, a camera is attached to the welding progress direction of the laser head, and the weld line imaged by the camera is The image is processed at high speed, its position is detected, and the irradiation position of the laser beam is corrected. In particular, in laser welding, the beam diameter of the laser beam is small and the butt part of the workpiece is narrow, so it is necessary to precisely align the irradiation point of the laser beam with the weld line. To detect a weld line when welding with such a laser welding machine, an optical cutting method is used as an optical image input method.

In FIG. 4 showing a weld line detection section of a conventional laser welding machine, an irradiation section 20 such as a laser beam irradiates a fan-shaped light f onto a welded section of a workpiece 10, and an imaging camera or the like The image is observed by the image input section 30, the welding line is detected by the data processing device 40, and the position is sent to a drive section (not shown) of the laser welding head 50.

In the data processing device 40, the analog image signal s1 is converted into a digital image signal s2 by an analog-to-digital conversion means 41. The position measuring means 44 measures the time from the start of one scanning line and outputs it as a position signal s5. The image brightness/distance holding means 45 stores the maximum value of the digital image signal s2 in one scanning line and the position signal s5 at that time, and stores them as image brightness data s6 and image position data. Output as s7. The welding line detection means 46 is 1
Image brightness data s6 and image position data s7 for the screen
After accumulating the data, welding line detection is performed and welding position data s8 is output.

[0005]

[Problems to be Solved by the Invention] FIG. 5(a) shows an observed optical section image. Here, since the scanning line of the image signal is in the horizontal direction in the figure, the signal strength of the scanning line at the P position is
b) However, as mentioned above, the signal strength when the image signal strength is maximum is taken as the luminance, and the position at that time is taken as the image position, so if noise due to secondary reflection or sputtering light enters the image signal, As shown in FIG. 5(b), the brightness and position of the image were detected incorrectly, and the weld line could not be detected correctly.

[0006] Noise removal using a high frequency cut filter can be considered, but it is not sufficiently effective if the noise is not pulse-like, and cannot be used if the optically sectioned image is narrow because it becomes difficult to detect the image.

An object of the present invention is to accurately detect the position of a welding line and promptly correct it to weld the workpiece even when noise is mixed into the input image due to the surface reflection state of the workpiece or lighting conditions. The object of the present invention is to obtain a welding position detection device capable of detecting welding positions. [Structure of the invention]

[0008]

[Means for Solving the Problems] The present invention, as shown in FIG. 1, irradiates a fan-shaped light onto a butt welded part of a workpiece, processes an image signal of a camera that images the welded part, and processes the welded part. In a laser welding machine that detects a welding line and corrects an irradiation position of a laser beam for welding the workpiece, a signal delaying means for delaying a digital image signal s2 obtained from an image signal of the camera; A brightness measuring means performs average and difference calculations of image brightness using the digital image signal s2 and the delayed digital image signal s3, and a brightness measuring means calculates the average and difference of image brightness using the digital image signal s2 and the delayed digital image signal s3, and predicts the time from the start of one scanning line of the image signal. A position measuring means for determining a position, a maximum value of the output of the brightness measuring means during one scanning line time of the image signal, and brightness/position retention of an image that holds the output of the position measuring means when the maximum value is generated. This welding position detection device is provided with a means to obtain the welding position from the held signal, thereby accurately detecting the welding position without being influenced by the proof or the surface condition of the workpiece.

[0009]

[Operation] The irradiation unit 20 irradiates the welding portion of the work 10 with fan-shaped light f. The welding position detection device 40 detects the welding position from the image signal s1 observed by the camera 30, drives the welding head 50, and corrects the welding position.

[0010] The analog-to-digital conversion means 41 converts the analog image signal s1 into a digital image signal s2. The signal delay means 42 delays the digital image signal s2 for a certain period of time and outputs the delayed digital image signal s3. The brightness measuring means 43 performs average calculation and difference calculation using the digital image signal s2 and the delayed digital image signal s3, and outputs a brightness signal s4. The position measuring means 44 counts the time from the start of scanning for each scanning line, and generates a position signal s.
Output as 5. The image brightness/distance holding means 45 is 1
The maximum value of the brightness signal s4 in the scanning is detected and held for each scanning line, and the position signal s5 at that time is held, and these are used as image brightness data s6 and image position data s7.
Output as . Welding line detection means 46 accumulates one screen's worth of image brightness data s6 and image position data s7, then detects welding lines and outputs welding position data s8.

[0011]

Embodiment FIG. 2 is an embodiment specifically showing the main parts of the welding position detection device of the present invention.

The synchronization separator 44b detects the timing of the start of one scanning line and generates a horizontal synchronization signal SYN. register 45
Clear b. The oscillator 44a generates a clock signal CLP of a constant frequency, updates the register 43b for storing luminance calculation data, increments the position measurement counter 44c, and enables the comparator 45a for determining the maximum luminance.
do bull. The counter 44c receives the position signal s5 by counting the clock signal CLP from the start of one scanning line.
occurs.

[0013] Analog-to-digital conversion means 41, which is constituted by an A/D converter or the like, converts the analog image signal s1 into a digital image signal s2. The signal delay means 42 is constituted by a shift register or the like, and receives the clock signal CL.
A delayed digital signal s3a obtained by delaying the digital image signal s2 by a time Ta and a delayed digital signal s3b delayed by a time Tb are output. ROM that stores calculation tables
The arithmetic unit 43a, which includes the following, inputs the digital image signal s2, delayed digital image signal s3a, delayed digital image signal s3b, and brightness signal s4, and outputs a calculation result signal sx according to the following equation (1). sx=s4 +s2 −2×s3a+s3b…(1)

[
Furthermore, with the above configuration, these signals can be expressed as a function of t in units of clock signal CLP as follows. However, Ta and Tb are the clock numbers corresponding to the delay times Ta and Tb. From equations (1) and (2), the calculation result signal sx is

00
15] sx(t)=s4 (t)+s2 (t)-2×s2
(t-Ta)+s2 (t-Tb)


...(3). Using the conditions of formula (2), formula (3
) from t=0 to t=N+Tb+1,

[0016] This is the clock timing N
+Tb+1, the brightness signal s4 output from the brightness measuring means 43 is at the timing N of the digital image signal s2.
The value is obtained by subtracting the sum from timing N to N+Ta from the sum from +Ta+1 to N+Tb. That is, the difference between the average values of the sections Ta and Tb-Ta is determined.

The image brightness/position holding means 45 is composed of a comparator 45a and a register 45b. The comparator 45a outputs the value of the brightness signal s4 and the brightness data s6 of the image.
When the brightness signal s4 is larger than the brightness data s6, the value of the brightness signal s4 and the position signal s5 are compared.
The value of is latched into the register 45b. This operation is performed in synchronization with the clock signal CLP. As a result, the image brightness/position holding means 45 stores the image brightness data s6 and the image position data s7 at the time when scanning of one scanning line is completed.
Brightness data and position data when the value of brightness signal s4 is maximum
Output data.

The above image signal processing process is shown in FIG. FIG. 3(a) is an optically sectioned image with noise due to secondary reflection and sputtering. FIG. 3(b) shows the digital image signal and luminance signal of the scanning line indicated by the arrow P in FIG. 3(a). Since the average calculation is performed, it is not affected by pulse-like noise such as spatter, and the difference calculation is used to calculate the brightness of the light section image without being affected by noise such as secondary reflected light that is close to the light section image. The location can be extracted.

[0019]

As described above, according to the present invention, fan-shaped light is irradiated onto the butt-jointed portion of the workpiece, and the signal from the camera that images the welded portion is processed by the image processing device to detect the weld line of the welded portion. death,
In a laser welding machine that corrects the irradiation position of the laser beam for welding a workpiece, average calculation and difference calculation in the scanning line direction are performed in the image processing process to extract the brightness and position of the light-cut image. Since the welding line is detected and the position of the laser head is quickly corrected, a laser welding machine that can accurately weld along the welding line without being affected by image noise such as secondary reflection or spatter is obtained. be able to.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of main parts of a welding position detection device of the present invention.

FIG. 2 is a block diagram showing an embodiment of the present invention.

FIG. 3 is a characteristic diagram for explaining the operation of the above embodiment.

FIG. 4 is a configuration diagram of main parts of conventional welding position detection scanning.

FIG. 5 is a characteristic diagram for explaining the operation of a conventional welding position detection device.

[Explanation of symbols]

10...Work 2
0...Irradiation section 30...Image input section
40...Data processing device 41...Analog-digital conversion means 42...Signal delay means 43...Brightness measurement means 43a...
Arithmetic unit 43b...register
44... Position measuring means 44a... Transmitter
44b...Sync separator 44c...Counter
45... Image brightness/distance holding means 45a... Comparator 45b... Register 46... Welding line detection section 5
0...Welding head f...Fan-shaped light
s1...analog image signal s2...digital image signal s3, s3a, s3b...delayed digital image signal s4...luminance signal s5...position signal s
6... Image brightness data s7... Image distance data s8... Welding position data s43a...
Operation result signal s44a...clock signal
s44b...Horizontal synchronization signal s45a...Comparison result signal

Claims (1)

[Claims] Claim 1: A fan-shaped light is irradiated onto a butt welded part of a workpiece, an image signal from a camera that captures an image of the welded part is processed to detect a welding line of the welded part, and the workpiece is welded. A laser welding machine that corrects the irradiation position of a laser beam, a signal delaying means for delaying a digital image signal obtained from an image signal of the camera, and using the digital image signal and the delayed digital image signal. brightness measuring means for calculating the average and difference of image brightness; position measuring means for determining the position on the screen by measuring time from the start of one scanning line of the image signal; and one scanning line time of the image signal. image brightness/position holding means for holding the maximum value of the output of the brightness measuring means and the output of the position measuring means when the maximum value is generated, and the welding position is determined from the held signal. A welding position detection device characterized by obtaining.