Integrated application of the hottest machine visi

Integrated application of machine vision and industrial automation system

machine vision market

machine vision, as one of the important components of industrial automation system, its technology and application are also increasingly mature with the development of automation industry. It is embodied in the continuous enhancement of image processing ability and speed, the improvement of optoelectronic device performance, the gradual unification of various standards and the relative reduction of price. According to the Market Research Report of AIA (automatic Imaging Association), the global machine vision market has exceeded US $7billion in 2006, and it is predicted that it will continue to grow in the next five years. However, as suppliers and integrators continue to promote machine vision applications to various fields, how to seamlessly integrate machine vision, a relatively independent function, into all kinds of automation equipment in various industries has encountered unprecedented challenges

application and challenges of machine vision

machine vision applications can be divided into two categories:

one is used in large-scale or high testing production lines, such as packaging, printing, sorting, etc., or in fields, nuclear power and other environments that are not suitable for human work, using machine vision to replace traditional manual measurement or testing, while achieving reliability, accuracy and automation that cannot be achieved under manual conditions

another kind of application is the professional equipment manufacturing that must use high-performance and precision machine vision components. The typical representative is the semiconductor manufacturing equipment that first led to the rise of the whole machine vision industry. From the classification and cutting of upstream wafer processing and manufacturing, to the printing and placement of terminal circuit boards, such devices rely on high-precision visual measurement to guide and locate moving parts. For example, if there is a positioning deviation in the solder paste printing process, and the problem is not found until the test after chip mounting, the cost of repair will be more than 100 times the original cost

however, in the above applications, the machine vision function is rarely regarded as an isolated system, but appears as an organic part of the whole automation system or equipment. It can really give full play to its advantages only when it is combined with other functions such as logic control, motion control, data acquisition, communication network and enterprise database management. To build a machine vision system, in addition to completing a series of processes from light source allocation to image processing software development, it is also facing the challenges brought by the functional integration with the above-mentioned complex automation systems. A single visual development software and hardware scheme often makes the overall development cycle, cost and uncertainty risk of the automation system borne by the manufacturer or integrator. The difficulty of integrating machine vision and automation system has greatly hindered its application in the relatively conservative field of industrial automation

solutions based on NI LabVIEW and machine vision system

facing the above challenges, NI LabVIEW software platform and its machine vision system provide a good solution

let's first look at the development and integration process of machine vision from the perspective of software: first, with the help of efficient and convenient configuration software vbai (machine vision generator applied to automatic detection) and comprehensive vision modules (covering the support of all systems and standards of cameras, providing hundreds of image processing functions such as pattern matching, OCR, particle analysis, two-dimensional bar code recognition), Users can verify different camera and light source settings, acquisition methods and image processing algorithms in an interactive development environment, and then automatically generate an executable Mo strengthened Fe-Cr-C surfacing material microstructure and mechanical property analysis program corresponding to LabVIEW. LabVIEW software platform has intuitive graphical development characteristics, which makes engineers focus more on function development rather than code writing. In the process of overall system development and integration, engineers can directly use the corresponding LabVIEW toolkit and modules to complete the functions of motion control, data acquisition, industrial communication and man-machine interface in the same way under the unified platform, and realize the connection and communication with various PACS (programmable automatic controllers), PLCs, industrial equipment, OPC clients and enterprise databases. For this development mode, both experienced integrators and junior developers can be liberated from the difficulties of development methods and platforms, drives and protocols, and physical communication and synchronization between equipment and materials of special and even private agricultural machinery corresponding to different equipment, which greatly reduces the difficulty and cost of system integration

from the perspective of hardware architecture, PC based machine vision system, due to its openness and flexibility, not only provides strong processing power, but also is easier to integrate with other functions. However, due to the reliability and volume of PC architecture, it can not fully meet the needs of industrial applications. The other way is embedded architecture, which is simple to use and highly reliable, but has relatively single function and poor integration. In order to solve these contradictions, Ni in its compact machine vision system (CVS), through the integration of LabVIEW real-time and FPGA technology, has unprecedented achieved the flexible customization and movement of i/o and communication protocols under the same embedded hardware platform, which can simultaneously collect and process three-way image signals, ensure the robustness and reliability of the system, and meet the application requirements in the harsh environment of industrial sites (Figure 1)

figure 1 Fig.1 Ni compact machine vision system

next, we will discuss how to integrate machine vision and multi domain functional applications by using open and flexible software and hardware platforms through two examples, so as to reduce the complexity of system integration and shorten the development cycle

automatic semiconductor wafer classification system based on LabVIEW and synchronous machine vision, motion control and data acquisition

in the semiconductor manufacturing industry, wafers must be carefully classified according to their thickness (THK), full thickness error (TTV), bow, warp and other electrical and physical parameters before cutting, so as to meet strict tolerance requirements. In order to ensure the measurement accuracy, the traditional single point measurement method needs to consume a lot of testing time. To this end, gigamat technologies of the United States has developed a new generation of full scan automatic classification equipment (Figure 2) to improve throughput and meet the accuracy and repeatability requirements under single point test, which is a considerable technical challenge

figure 2 automatic semiconductor wafer classification system

the new fully automatic wafer classification system makes full use of the LabVIEW platform and its supporting toolkit. The system is divided into two working steps: wafer alignment and measurement. The alignment process uses the line scan image acquisition method and 3-axis motion control. Through synchronous image acquisition and chassis rotation rate, the image acquisition of the whole wafer of 6million pixels is completed in 1 second. The center position, flatness and other characteristics of the wafer are judged by using LabVIEW visual algorithm, and the wafer position is adjusted accordingly to achieve complete matching with the parameter measurement platform. The measurement steps require that the resolution of the measurement of the distance between the upper and lower surfaces is less than 0.0001mm. The solution is to use the Ni motion control tool to generate a smooth arc and spiral trajectory combination under the LabVIEW platform, accurately control the position of the rotating wafer, use the Ni data acquisition card to complete the high-speed and high-density measurement of the probe synchronously carried out by multiple channels, record the corresponding position in real time, and then carry out relevant calculation and processing to obtain various parameter information, Finally, the classification results are obtained

in addition to the above core capacity reduction and enterprise transformation and upgrading steps, the system also includes: touch screen human-machine interface; Wafer elevator control based on RS-485 communication; Digital i/o control for light source, machine power and vacuum equipment; And connect with Microsoft Access database to realize the digital processing of machining process. These functions are all developed under the LabVIEW platform. The manager of gigmat commented that "without the synchronization of LabVIEW and Ni machine vision, motion control and data acquisition products, this project cannot be economically feasible"

Ni compact machine vision system helps automotive spark plug detection meet the repeatability standard of 6Sigma

the eccentricity and electrode spacing of automotive spark plug are the key indicators to determine its performance. In the past, a leading automotive spark plug manufacturer has been measuring it manually. Because of the low measurement accuracy, it must adopt too strict product tolerance zone restrictions, resulting in unnecessary production requirements and production reduction. In order to ensure reliable quality control, faster inspection speed and improved output, the manufacturer decided to establish a full scan size quantitative system based on machine vision

the system is composed of IEEE 1394 camera, ring light source, rugged Ni CVS embedded machine vision system and LabVIEW software development platform. The collected spark plug image is transmitted to CVS through the live wire, and special algorithms such as real-time circular edge detection are run on it. Through the control of under sampling, the balance point between accuracy and processing time is found, and the measurement accuracy reaches 0.01mm, which fully meets the 6Sigma standard. Subsequently, CVS communicates with PLC, relays and other equipment on the production line through its digital port to complete the automatic elimination of nonconforming products without manual intervention. The whole system is connected to the factory Ethernet and can be used for remote parameter configuration, calibration and product information recording. Due to the improvement of test accuracy, the tolerance range is widened, and the output and efficiency are greatly improved

conclusion

machine vision application is developing from simple image acquisition, processing and analysis, result judgment and output at the beginning to become one of the important components of automation system. However, compared with manual detection, machine vision also has its particularity, which is reflected in its flexibility and adaptability to a certain extent. If it is not handled properly, even the introduction of a seemingly small new function may lead to the redesign of the system. Facing the integration, flexibility and difficulties of machine vision, the ideal industrial software development environment LabVIEW has become a very good choice for user development platform. Using the rich analysis and processing algorithms contained in the machine vision module, users can customize and develop or simply upgrade the corresponding visual functions according to their specific needs, and can also realize the development of motion control, programmable automatic controller, data acquisition and other equipment and functions in this unified image development method, as well as the seamless connection with the three-party PLC, industrial equipment and database software, So as to complete the development and integration of automation system including machine vision function. Thanks to this system architecture, manufacturers can more easily introduce machine vision functions into their production lines, reducing the average value of - X - 1 group of measured values manufactured by their equipment; The technical difficulty is in line with the trend of machine vision towards the integration of automation systems. (end)