CN106270940B - A kind of method of synchronous detection welding process electric image signal - Google Patents

Abstract

The invention relates to a method for synchronously detecting the image-electrical signal of the welding process. During the welding process, the image information of the welding process is collected by using an image acquisition card, and the electrical signal of the welding process is collected by a data acquisition card. The trigger signal triggers the image acquisition card and the data acquisition card to start the acquisition process at the same time. When the welding transfer arc is successfully ignited, the arc starting signal of the welding machine jumps from a low value to a high value. This signal can be used as a trigger judgment signal ; The external trigger signal that the camera starts collecting is the falling edge signal of the TTL pulse. The invention can unify the timing sequence of visual sensing and electrical signal measurement in the welding process.

Description

A Method for Synchronously Detecting Welding Process Image-Electric Signal

technical field

The invention belongs to the technical field of welding, and relates to a method for unifying the timing of visual sensing and electrical signal measurement in the welding process.

Background technique

The electrical signal in the welding process contains a wealth of information. It not only contains information about the performance of the welding power source, but also includes information about the welding quality, such as: core size, shape of the molten pool, penetration status, droplet transfer frequency and shape, etc. The detection of electrical signals in the welding process is of great significance to ensure the smooth progress of the welding process and the quality of the welded joints. The development of microcomputer and sensing technology makes it possible to use microcomputer to collect welding power voltage and current signals at high speed; at the same time, it is also possible to use microcomputer to process the signal in real time, and extract characteristic information reflecting the welding process from the detected electrical signal. Analyze the U-I curve diagram of the electrical signal during the welding process to judge the quality of the welded joint.

Compared with other welding sensors, the vision sensor has nothing to do with the welding circuit. It has the advantages of rich information, high sensitivity and measurement accuracy, good dynamic response characteristics, strong anti-interference ability of strong electric field and strong magnetic field, and no contact with the workpiece. It is suitable for various groove shapes, and can track the welding seam and control the welding conditions in real time at the same time, so it is the most promising welding sensing technology. At present, visual sensor and image processing technology have been used in the control of weld seam tracking, welding penetration, fusion width, protection effect, molten pool behavior, arc length, welding speed, dry elongation of welding wire, transition shape and frequency of droplet, It has been applied in temperature field monitoring, arc diagnosis and other fields.

However, during the welding process, the electrical signal acquisition process and the image signal acquisition process cannot be synchronized. This limits more precise analysis of both signals, leading to more reliable analysis results.

Contents of the invention

The invention provides a welding process signal acquisition synchronization method that unifies the visual sensing sequence and electrical signal measurement sequence in the welding process, so as to facilitate the computer to collect and detect the main parameters in the welding process, and facilitate the analysis of the main parameters and control. Technical scheme of the present invention is as follows:

A method for synchronously detecting the image-electric signal of the welding process. During the welding process, the image information of the welding process is collected by using the image acquisition card, and the electrical signal of the welding process is collected by the data acquisition card. When the welding arc starting process starts, a trigger signal is applied. Trigger the image acquisition card and the data acquisition card to start the acquisition process at the same time. When the welding transfer arc is successfully ignited, the arc starting signal of the welding machine jumps from a low value to a high value. This signal can be used as a trigger judgment signal; the camera starts The external trigger signal collected is the TTL pulse falling edge signal; the following synchronous trigger circuit is used:

Use the 555 integrated chip to generate a TTL signal with a frequency of 1KHz and send it to pin 1 of the 74LS00N NAND gate chip; the arcing signal U ₀ during welding is filtered and then input to the photocoupler PC817;

When the welding process arc signal U ₀ is zero, there is no conduction between pins 3 and 4 of PC 817, the voltage U ₂ input to pin 2 of the 74LS00N NAND gate chip is 0, and the 74LS00N NAND gate chip outputs a high potential U ₁ , the image acquisition card and the data acquisition card will not collect the signal;

When the welding process arc signal U ₀ is a high potential signal, the pins 3 and 4 of PC 817 are connected, and the voltage U ₂ input to pin 2 of the 74LS00N NAND gate chip is a high potential signal, and the data acquisition card starts to collect the welding process. At the same time, since pin 2 of the 74LS00N NAND gate chip is at a high level, the U ₁ signal output by pin 3 is inverse to the signal of pin 1, that is, a 1KHz TTL signal is output, triggering the camera to start capturing images.

The synchronous trigger circuit designed in the present invention can unify the timing of visual sensing and electrical signal measurement. Compared with the independent acquisition process of the two signal acquisition processes of electrical parameter signal and image in the experiment, the two acquisition processes are in Starting at the same time can make the two signals have a unified time sequence, so that the image signal and electrical parameter signal during the welding process can be accurately analyzed, and the phenomenon during the welding process can be analyzed more accurately.

Description of drawings

Fig.1 Schematic diagram of signal acquisition system in welding process

Figure 2 synchronous trigger circuit diagram:

detailed description

In the image capture system, the interference of the tail flame arc is eliminated by adding a filter, so that the liquid surface of the molten pool can be seen clearly. In order to obtain a complete and clear image of the small hole, an exhaust flame detection board can be installed at the bottom of the small hole on the back of the workpiece, and the position of the detection board can be adjusted to allow the camera to have a suitable viewing angle. In the welding process, the same welding process parameters are used to realize the penetration hole welding. Design a reliable small hole edge algorithm to extract the small hole edge. After calibrating the camera parameters, the actual size and center offset of the small hole can be calculated from the small hole pixel value in the image. In order to start the acquisition process of electrical parameter signal and image at the same time, the synchronization method adopted is: when the welding arc starting process starts, a trigger signal is applied to trigger the image acquisition card and data acquisition card, so that both start the acquisition process at the same time.

The acquisition system is shown in Figure 1. The current image sensor is the GS3-U3-41C6NIR camera produced by Gray point, and the No. 8 filter of the welding cap is used to eliminate the interference of the tail flame arc. When a small hole penetrating the workpiece is formed, the bottom of the small hole emits a tail flame, and the dynamic behavior of the penetrating small hole can be observed from the back of the workpiece. An exhaust flame detection board is installed at the bottom of the small hole on the back of the workpiece. Adjusting the position of the detection board can allow the camera to have a suitable viewing angle.

In the data acquisition and control system, the NI 6002 data acquisition card is used, which can provide eight analog input channels with 16-bit resolution and 50kS/second sampling rate, and also includes 13 I/O lines, a Basic counter for edge counting with two analog output channels. The welding process parameter acquisition and control system is written using NI LabView software. The current output signal is sent by the NI6002 acquisition card, and connected to the welding machine control power supply through the isolation module to output the welding current of arbitrary waveform. In the data acquisition link, the current Hall sensor sends back the welding current signal; the tail flame sensor monitors the penetration state of the small hole, and the voltage sensor obtains the tail flame voltage induction signal. These electrical signals are transferred to the computer after being converted by the NI 6002 acquisition card, and fed back to the data acquisition and process control system to control the welding and perforation process.

In the welding experiment, two kinds of signals need to be collected, the electric parameter signal is collected by the data acquisition card, and the image is collected by the camera. These two acquisition processes are independent of each other and each has its own timing. In order to make the two signals have a unified time series, the two acquisition processes need to be started at the same time. The synchronization method adopted is: when the welding arc starting process starts, a trigger signal is applied to trigger the image acquisition card and the data acquisition card, so that both start the acquisition process at the same time. When the welding transfer arc is successfully ignited, the arc starting signal of the welding machine jumps from a low value (0V) to +24V, and this signal can be used as a trigger judgment signal. However, the external trigger signal for the camera to start collecting is the TTL pulse falling edge signal, and the data acquisition card NI 6002 starts collecting when it receives a high potential signal. In order to realize this trigger function, a synchronous trigger circuit is designed, as shown in Figure 2.

The working principle of the trigger circuit is:

(1) The 555 integrated chip generates a TTL signal with a frequency of 1KHz and sends it to pin 1 of the 74LS00N NAND chip; the arc signal U ₀ (Arc on Signal) in the welding process is filtered and then input to the photocoupler PC817.

(2) When the transfer arc is not ignited, U ₀ is zero, there is no conduction between pins 3 and 4 of PC 817, it is regarded as an open circuit, and the voltage of pin 2 of the input NAND gate is 0. In this way, U ₁ is high potential, U ₂ is 0, neither the image acquisition card nor the data acquisition card will collect signals.

(3) When the transfer arc starts, U ₀ is a high potential signal of +24V, and the pin 3 and pin 4 of PC 817 are turned on, which is regarded as a short circuit, and the voltage of pin 2 of the input NAND gate is high potential, that is, U ₂ is a high-potential signal, and the data acquisition card starts to collect the electrical signal of the welding process; at the same time, because the pin 2 of the NAND gate is at a high level, the U ₁ signal output by pin 3 is in the opposite phase to the signal of pin 1, that is, Output 1KHz TTL signal to trigger the camera to start collecting pinhole images.

The first falling edge of U ₁ may lag behind the rising edge of U ₂ , and the lag is less than one U ₁ signal pulse period (1ms), that is, the start moment of image acquisition may lag behind the electrical parameter acquisition moment. This short-term phase lag will not affect the actual processing effect and can be ignored.

The synchronous trigger circuit can unify the timing of visual sensing and electrical signal measurement. Compared with the independent acquisition process of the two signal acquisition processes of electrical parameter signal and image in the experiment, starting the two acquisition processes at the same time can The two signals have a unified time sequence, so that the image signal and electrical parameter signal in the welding process can be accurately analyzed, and the phenomenon in the welding process can be analyzed more accurately.

Claims (1)

1. a kind of method of synchronous detection welding process image-electric signal, in welding process, is gathered using image pick-up card and welded Termination process image information, welding process electrical signal is gathered using data collecting card, when welding Igniting pattern starts, apply and touch Signal, trigger image pick-up card and data collecting card, the two is started gatherer process simultaneously, when welding transferred arc successful ignition Afterwards, machine initial arc signal jumps to high level by low value, and this signal can be used as triggering to judge signal；Video camera starts collection External trigger signal is TTL pulse trailing edge signal；Using following synchronous trigger circuit：

1 pin of the TTL signal feeding 74LS00N NAND gate chips that frequency is 1KHz is produced using 555 integrated chips；Welding process Starting the arc signal U₀Input optocoupler part PC817 after after filtering；

As welding process starting the arc signal U₀It is not turned between the pin 3 and 4 for being zero, PC 817, input 74LS00N NAND gates chip 2 The voltage U of pin₂High potential U is exported for 0,74LS00N NAND gates chip₁, image pick-up card and data collecting card are believed all without collection Number；

As welding process starting the arc signal U₀For high potential signal, turned between PC 817 pin 3 and 4, input 74LS00N with it is non- The voltage U of the door pin of chip 2₂For high potential, data collecting card starts to gather the electric signal of welding process；Simultaneously as 74LS00N 2 pin of NAND gate chip are high level, the U of 3 pin output₁Signal and 1 pin signal inversion, that is, output 1KHz TTL signal, Triggering video camera starts to gather image.