Electron beam equipment welding processing technology and equipment for dynamic tracking and online monitoring of welding seam

Abstract

According to the invention, dynamic tracking and on-line monitoring of the welding seam of the electron beam equipment in the welding field are realized. Backscattering electronic data are collected through the photoelectric conversion circuit, the signal threshold adjusting circuit and the AD module, signal amplification and signal conversion are conducted, the data are transmitted to the FPGA to be subjected to parallel high-speed data processing, and output image data are displayed on the display screen in real time through the HDMI module. Scanning control signals are given through the PL end, controlled through the PS end and output to the high-frequency scanning drive circuit through the DA module, and dynamic tracking welding of welding seams is achieved.

Description

Technical Field

[0001] The present invention relates to the fields of welding processing and electron optical imaging, and particularly to the phenomenon that during the electron beam welding process, the weld seam cannot be monitored in real time and dynamically tracked. A method of collecting backscattered electrons for data analysis is used to achieve the dynamic tracking and on-line monitoring and display technology of electron beam weld seams. Background Art

[0002] Electron beam welding refers to bombarding the welding surface in a vacuum or non-vacuum environment with an accelerated and focused electron beam, which plays an increasingly important role in the fields of aerospace, marine vessels, and automobile manufacturing. The 21st century has put forward new requirements for processing, and processing is developing towards high precision, high efficiency, low pollution, etc. Therefore, traditional processing methods are gradually phased out, while new processing methods such as laser processing and electron beam processing gradually show their advantages and have a rapid momentum to become the mainstream processing methods.

[0003] The electron beam processing technology realizes processing by emitting a high-energy electron beam from an electron gun and bombarding the surface of the workpiece. Therefore, many metals with high melting points that cannot be fusion-welded by traditional processing methods can be processed using an electron beam. Thanks to the adjustment of the high-frequency deflection system and the electron beam cathode acceleration voltage, the electron beam can complete deflection and energy adjustment within milliseconds, thus realizing the welding of dissimilar metals. The vacuum processing environment ensures that the weld seam will not oxidize, and at the same time, no solder needs to be added, ensuring the overall strength and stiffness after welding.

[0004] However, the processing environment of the electron beam must be a vacuum environment, and welding defects such as pores and cracks often occur during the welding process. Therefore, it is impossible to observe the processing effect closely and make dynamic adjustments. Therefore, proposing a new technology that can achieve dynamic tracking and on-line monitoring of electron beam weld seams without breaking the vacuum environment has become one of the important challenges that need to be solved urgently.

[0005] Dynamic tracking and on-line monitoring of weld seams are a new task that the electron beam welding industry urgently needs to solve.

[0006] First, it is very difficult to weld workpieces with complex geometric shapes. Some metal parts with complex geometric shapes in harsh outdoor environments are prone to cracks, resulting in unusability. However, directly scrapping due to only local damage will greatly increase costs. Therefore, in engineering, it is more inclined to repair the welds to enable continued use. However, curved surface welding is mainly manual welding. The most important drawback of manual welding is low processing efficiency. Workers cannot work continuously and intensively like machines. Moreover, the processing quality of manual welding is difficult to guarantee. Manual welding cannot ensure the same processing effect for each weld. The welding results will be uneven when a different person or the same person welds multiple times. Manual welding is usually carried out in space, and the high temperature during the welding process will cause oxidation of the weld, greatly reducing the strength and stiffness of the weld after completion.

[0007] Second, when using an electron beam device for processing, first, the working space needs to be evacuated to a vacuum by a vacuum pump group, and this process requires more than thirty minutes of preheating. At the same time, after the electron beam processing is completed, the working space cannot be opened immediately. The pump group needs to be opened to inject air to slowly restore it to atmospheric pressure before the processed workpiece can be taken out. Therefore, it is impossible to observe the workpiece and monitor the welding quality in the working area during the processing. If proper planning is not done before processing, processing errors will occur, affecting the processing quality and efficiency.

[0008] Third, electron beam processing is mainly applied to welds with a large depth-to-width ratio. The diameter of the electron beam spot is usually only 200 microns, so it can cut workpieces precisely like a precision scalpel and can also weld workpieces. In the actual processing process, we hope to be able to see the welding situation of the weld closely and make timely adjustments according to the welding situation. The welds will have different depths. In the rapid electron beam processing process, relying solely on manual real-time adjustment or programming the processing technology in advance according to the actual situation of the weld is a solution with a huge workload and difficult to implement. It is difficult to monitor the processing effect, the processing quality is difficult to guarantee, and post-weld treatment is required, seriously affecting the processing quality and low production efficiency.

[0009] Fourth, the shape and trend of the weld are irregular. In many cases, the weld does not occur along a straight line, and its trend is unpredictable, presenting an irregular curve. There may even be many branches on the basis of the main line, with different widths, depths, and shallows. Manual welding is difficult to complete, but machine welding is also difficult to operate. Therefore, being able to perform automatic tracking of the weld and constructing an online monitoring window for human-computer interaction are problems that the welding industry urgently needs to solve currently.

[0010] Regarding the above pain points, there is currently no technology for dynamic tracking and online monitoring of weld seams for electron beam equipment. Corresponding solutions have been proposed for other welding methods. For example, in robotic arm welding, a camera is installed. The camera captures the weld seam situation in the area to be welded currently, transmits the image at the current moment to the processor, and the algorithm will identify the weld seam and generate the welding trajectory of the robotic arm to achieve closed-loop dynamic tracking of the weld seam. The present invention proposes and adopts a technical method for online monitoring and dynamic tracking of weld seams for electron beam equipment, filling the current gap in the electron beam industry. Summary of the Invention

[0011] The present invention provides a technical method for electron beam welding processing to achieve dynamic tracking and online monitoring of weld seams. This technology can be directly transplanted onto any existing electron beam processing equipment, making the electron beam processing process intelligent, adaptive, and highly efficient. The electron beam processing is originally not picky about the materials of the workpieces to be processed, and this equipment will completely realize the automation of the processing process. To achieve the above object, the present invention adopts the following technical solutions:

[0012] First step, install a backscattered electron detector in the vacuum chamber of the processing area of the electron beam equipment. The probe is equipped with two stepping motors, which can realize the adjustment of the probe coordinate axis position and the deflection angle of the probe externally. This backscattered electron detector is the key to the source of weld seam data. When the electron beam hits the surface of the workpiece, a large number of electrons will be reflected. These electrons carry a lot of weld seam information. By extracting the information among them, the situation of the weld seam can be known. The probe has a laser rod. When the electrons hit the laser rod, it will emit light. Combining with optical fibers and a photoelectric conversion circuit, the optical signal of the backscattered electrons is converted into an electrical signal. This step is an important basis for all subsequent work to be carried out.

[0013] Second step, further process the obtained electrical signal. Adjust the brightness and contrast of the online monitoring image through a signal threshold adjustment circuit. The user can see the adjusted effect on the display, and the electrical signal of the signal threshold adjustment circuit will be transmitted to the AD module.

[0014] Third step, realize the signal transmission between the external circuit and the internal processor through a 12-bit AD analog-to-digital conversion module. This module converts the electrical signal into a digital signal. The digital signal output by the AD module will be transmitted to the PL end of the FPGA for Gaussian parallel data processing, filter the image data, filter out the salt-and-pepper noise and Gaussian noise existing in the image through median filtering and Gaussian filtering algorithms, and realize the filtering of the imaging signal in a pipeline manner.

[0015] The fourth step is to transmit the backscattered electron signal processed by FPGA on the PL side to the PS side. The PS side is a processor system, which processes the data and performs floating-point operations to optimize the weld details, thereby improving the welding quality and efficiency from the system level. After completing a cycle of data processing on the PS side, a new cycle of scanning is about to begin, and the PS side sends an enable signal to reset the counter. After the counter is reset, the electron beam spot is pulled back to the starting point of the scan, and the next cycle of scanning is performed at the starting point of the scan. The PS side controls each module through the GP interface and transmits the final generated weld position information back to the PL side. The overall control of data transmission is completed on the PS side, and the data transmission process is simulated online.

[0016] The fifth step is to transmit the data from the PS end to the PL end. At this time, the position information of the weld has been fully analyzed. Next, it is necessary to use this information to guide the electron beam welding work and the real-time HDMI display of the electron beam weld position. The PL end generates corresponding signals to control the high-frequency scanning drive module, dynamically adjust the electron beam energy distribution and scanning path through the high-frequency deflection system, track the weld position in real time, automatically generate trajectories along irregular curves and adjust the electron beam parameters to ensure that the electron beam accurately hits the center of the weld and repairs the cracks.

[0017] Step 6. In the ZYNQ system, the HDMI interface is connected to the PL end. After completing the acquisition of a frame of data, the PS end normalizes the frame data in DDR3 to pixel grayscale and transmits it to the AXI4-Stream to Video Out IP core through VDMA. The AXI4-Stream to Video Out IP core converts the data in AXI4-Stream format into the data format of video output, and transmits the video data to the HDMI driver module to realize real-time display of HDMI.

[0018] Step 7: Repeat steps 3 to 6 until the entire weld repair process is completed, and the real-time image of the welding can be seen on the display screen throughout the process.

[0019] The electron beam welding dynamic tracking and online monitoring technology works through the above modules and steps. The invention can effectively solve the problems currently faced by the welding industry. The beneficial effects of the invention are as follows:

[0020] Compared with the backscattered electron detectors currently used in the electron beam processing process, the scintillation crystal detector has advantages such as good signal-to-noise ratio, temperature resistance and suitability for high-voltage environments. It has better applicability and good sensitivity in the complex environment of the electron beam welding area. In addition, through optical fiber transmission, the photoelectric conversion amplifier circuit is placed away from the workpiece area, which effectively reduces the impact of space charge on the circuit system, thereby extending the service life of the circuit system.

[0021] The ZYNQ chip is mainly composed of a dual-core ARM processor, a high-speed interface AXI bus for the programmable logic unit (PL) to interact with the system. Compared with traditional FPGAs, it can efficiently process floating-point numbers using the NEON technology integrated in the ARM and perform optimized designs according to specific data processing requirements; compared with traditional ARM processor systems, it has strong parallel data processing capabilities and can also directly program the hardware circuit according to needs to reduce software execution operations and achieve high-speed data processing.

[0022] Backscattered electrons will be presented in the form of fluorescence with different brightnesses after colliding with the scintillation crystal. Designing a weak light signal conversion circuit with high sensitivity and gain can better capture and retain the detailed information of the weld surface morphology. The avalanche photodiode (APD) is a photoelectric conversion device based on the avalanche effect and has been widely used due to its advantages such as fast response speed and high sensitivity.

[0023] Design and simulation of the hardware drive module in the imaging system are implemented on the PL side, including the high-frequency scanning drive module, the weld data acquisition module, and the weld data processing and caching module. Finally, the overall control of data transmission is completed on the PS side, and the data transmission process is simulated online. The weld image is displayed in real time through HDMI, which can well monitor the electron beam welding situation.

[0024] The energy distribution and scanning path of the electron beam are dynamically adjusted through the high-frequency deflection system. The moving edge generates a trajectory along an irregular curve and adjusts the electron beam parameters to ensure that the electron beam accurately hits the center of the weld and repairs the crack.

[0025] The present invention adopts a closed-loop control architecture, aiming to improve the welding quality and efficiency through real-time monitoring, analysis, and adjustment. This architecture integrates three functions: monitoring, analysis, and execution, which run through the entire welding process to form a closed loop to achieve dynamic tracking of the weld. Description of the Drawings

[0026] Figure 1 This is a schematic diagram of an electron beam equipment welding process for realizing dynamic tracking and online monitoring of the weld of the present invention;

[0027] Reference numerals in the figure: 1, electron gun; 2, deflection coil; 3, electron beam weld scanning area; 4, backscattered electron detector; 5, optical fiber; 6, photoelectric signal conversion circuit; 7, signal threshold adjustment circuit; 8, AD acquisition data conversion; 9, ZYNQ main control system; 10, HDMI display module; 11, DA output data conversion; 12, high-frequency scanning drive circuit; Detailed Embodiment

[0028] The present invention will now be described in further detail with reference to the accompanying drawings. The above drawings are all simplified schematic diagrams, which only illustrate the basic structure of the present invention in a schematic manner. Therefore, they only show the components related to the present invention.

[0029] The present invention provides a welding processing technology and equipment design concept for electron beam equipment for dynamic weld tracking and on-line monitoring, including an electron gun 1, a deflection coil 2, an electron beam weld scanning area 3, a backscattered electron detector 4, an optical fiber 5, an optoelectronic signal conversion circuit 6, a signal threshold adjustment circuit 7, an AD acquisition data conversion 8, a ZYNQ main control system 9, an HDMI display module 10, a DA output data conversion 11, and a high-frequency scanning drive circuit 12.

[0030] First, an electron beam current is emitted by the electron gun 1. When the electron beam passes through the deflection coil 2, since an electric current is passed through the circuit, the deflection coil 2 will generate a uniform magnetic field in this area. This magnetic field will deflect the electron beam, and the direction of the electron beam, as shown in the figure, will change like the red electron beam. When the electron beam hits the weld surface, secondary electrons and backscattered electrons on the weld surface layer will escape from the workpiece surface due to external bombardment. These electrons will be captured by the nearby backscattered electron detector 4. When the backscattered electrons hit the scintillation crystal on the backscattered electron detector, a weak optical signal will be generated. These optical signals are transmitted along the optical fiber 5 to the optoelectronic signal conversion circuit 6.

[0031] The optoelectronic conversion circuit 6 first amplifies the signal through an avalanche diode APD, converts the weak optical signal into a current signal, and then converts the current signal into a voltage signal through an operational amplifier circuit. However, at this time, the voltage signal is very weak and there are a large number of ripples. Therefore, a decoupling circuit is used to eliminate the noise, and a dual-cross amplifier is used to amplify the signal, and the voltage signal is output to the signal threshold adjustment circuit 7. The signal threshold adjustment circuit 7 adjusts the brightness and contrast of the weld information. The pre-processed data will be converted into a digital signal through the AD acquisition data conversion 8, and the digital signal is transmitted to the ZYNQ main control system 9 for high-speed parallel algorithm processing.

[0032] The ZYNQ main control system 9 is divided into a PL side and a PS side. Digital signals are sent to the weld seam data processing module on the PL side for data processing. Then, the processed data is transmitted by the DMA through the AXI interconnect module and the S_AXI_HP high-speed interface to the DDR3 memory on the PS side for storage. After completing the acquisition of data for one cycle, the PS side normalizes the frame data in the DDR3 into pixel grayscales and transmits it to the AXI4-Stream to Video Out IP core through the VDMA. The AXI4-Stream to Video Out IP core converts the data in the AXI4-Stream format into weld position information vector data to guide the electron beam welding in the next cycle. At the same time, the processed data passes through the HDMI module 10, and the buffered data is read out as streaming image data using the VDMA. Then, a timing control generator is needed to generate timing signals corresponding to the streaming image data. After the VDMA reads the image data buffered in the DDR3, AXI-Stream streaming image data is obtained. After converting the streaming image data into synchronous pixel and video timing signals through the AXI4-Stream to Video Out IP core, it can be displayed through the HDMI.

[0033] The processed digital signals are then output through the DA data conversion 11 to convert the digital signals into voltage signals. The high-frequency scanning drive circuit 21 responds quickly to the voltage signals and follows them well, transmitting the current signals to the deflection coil 2, and using the analyzed data to guide the electron beam to hit the exact middle of the weld seam in the next cycle. When the electron beam welding process ends, the electron beam performs raster scanning on the weld seam area 3 with a small beam current to continue obtaining the weld seam position, and the above operations are repeated until the weld seam is welded.

[0034] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, making equivalent substitutions or changes should be covered within the protection scope of the present invention.

Claims

1. An electron beam welding process and device for dynamic tracking and online monitoring of welds, characterized in that: include: ZYNQ main control system, AD conversion module, DA conversion module, high-frequency scanning drive circuit, backscattered electron detector, photoelectric conversion circuit, signal conditioning circuit and HDMI display module. The backscattered electron detector is located inside the vacuum chamber. It is responsible for converting the backscattered electron signal generated by the interaction between the electron beam and the sample during the deflection scanning process into an optical signal, and transmitting the optical signal to the area away from the workpiece through the optical fiber to the signal processing system outside the vacuum chamber. The signal conditioning circuit amplifies and filters the analog signal for collection by the AD conversion module. After the data is processed by ZYNQ's high-speed parallel processing, the position information of the weld is recorded, and the deflection scanning signal is output at the same time, the position information of the weld is continuously updated, and the working position of the electron beam in the next cycle is guided. This part of the data is simultaneously transmitted to the DMA for caching. First, the cached data needs to be read out as streaming image data using VDMA, and secondly, the timing controller needs to generate the timing signal corresponding to the streaming image data. After VDMA reads the image data cached in DDR3, the AXI-Stream streaming image data is obtained. After the streaming image data is converted into synchronized pixel and video timing signals through the AXI4-Stream to Video Out IP core, it can be displayed through HDMI. The data information processed by ZYNQ is converted by DA digital-to-analog conversion and then driven by the high-frequency scanning drive circuit to drive the deflection coil, guiding the electron beam to deflect so that it can hit the middle of the weld to achieve welding. At the same time, ZYNQ continuously sends scanning signals to guide the electron beam to scan the weld position in the area to be welded. Thanks to the high-frequency deflection circuit, the above process can be completed within milliseconds, and the frequency of this process is much greater than the refresh rate of the human eye, so it seems to be carried out at the same time, but in fact the electron beam has been repeating the same process to slowly complete the repair of the weld.

2. The electron beam welding process and device for dynamic tracking and online monitoring of weld seams as claimed in claim 1, characterized in that: The ZYNQ master control system is an integrated embedded system developed by Xilinx. It integrates the ARM Cortex-A series processors and field programmable gate arrays (FPGAs) to achieve high-performance computing and programmability of hardware logic on a single chip.

3. The electron beam welding process and device for dynamic tracking and online monitoring of weld seams as claimed in claim 1, characterized in that: The backscattered electron detector is mainly composed of two modules, backscattered electron collection and optical signal transmission, and a component base. The backscattered electron collection module includes a YAG scintillation crystal, a reflective lens and a focusing cup; the optical signal transmission module mainly includes a focusing lens, a light guide lens and an optical fiber.

4. The electron beam equipment welding process and device for dynamic tracking and online monitoring of weld seams as claimed in claim 1, characterized in that: The high-frequency scanning drive circuit, after the scanning signal sent by the ZYNQ main control system is converted by the DA module, needs to be amplified by the high-frequency scanning drive circuit to drive the deflection scanning coil. By applying current to the scanning coil, an electromagnetic lens is formed to realize the deflection control of the electron beam. The high-frequency scanning drive circuit is a key module for realizing high-speed scanning of the electron beam. The circuit can realize dynamic following of high-frequency signals, and can follow frequency signals up to 60KHz without overshoot.

5. The electron beam welding process and device for dynamic tracking and online monitoring of weld seams as claimed in claim 1, characterized in that: The HDMI display module, a digital interface standard for transmitting high-definition video signals and audio signals, adopts the same transmission principle as DVI and transmits audio and video data in differential signal mode through the TMDS (Transition Minimized Differential Signaling) standard. This design uses the HDMI digital transmission standard to design an HDMI driver module to display the backscattered electron image processed by the system in real time through the display.

6. The electron beam welding process and device for dynamic tracking and online monitoring of weld seams as claimed in claim 1, characterized in that: The AD analog-to-digital conversion module and the DA digital-to-analog conversion module are important data conversion modules for the electron gun welding system to communicate with the ZYNQ main control system. The output of the DAC is updated according to the rising edge of the clock. The DAC of each channel has an independent 14-bit data input port, WRT write enable and CLK clock signal line. The AD conversion module is controlled by the PL end clock. When the rising edge of the clock arrives, the AN9238 starts to convert the collected signal. The output digital signal is read in parallel in the channel through the PL end weld data acquisition module.

7. The electron beam equipment welding process and device for dynamic tracking and online monitoring of weld seams as claimed in claim 1, characterized in that: The photoelectric conversion circuit first converts the weak light signal of the backscattered electrons hitting the laser rod into a current signal, and then directly connects the output electrical signal to the operational amplifier circuit to convert the current signal into a voltage signal. At this time, the voltage signal is small and has a lot of interference, so a decoupling circuit is used to eliminate noise, and the signal is amplified through a dual-span amplifier to facilitate further signal processing by the FPGA.

8. The electron beam equipment welding process and device for dynamic tracking and online monitoring of weld seams as claimed in claim 1, characterized in that: The signal conditioning circuit adjusts the weld signal in a timely manner. Different capacitor and resistor combinations can achieve a maximum gain amplification of 21 times. The bandwidth gain provided by the operational amplifier is much larger than the gain-bandwidth product in the circuit, so that the detailed features of the weld surface morphology can be retained, which is more helpful for analyzing the weld position. The circuit gain is determined by the ratio of an adjustable resistor to a fixed resistor. By adjusting the resistance of the adjustable resistor connected to the circuit, the contrast of the signal can be adjusted to improve the welding quality.

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