Development status and application prospect of the

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The development status and application prospects of PAC technology

today's automation technology is developing rapidly and is in an era of rapid change. From semiconductors to consumer electronics, to automobile and aviation manufacturing, as well as light industry and logistics industry, many different industrial fields are facing increasingly fierce global competitive pressure. They need to further reduce costs, shorten product production cycle, and be able to complete product upgrading quickly. Adopting the latest automation technology is an effective means to solve this series of problems

1. Background of PAC control technology

since the 1970s, PLC replaced the original relay control system, it has been widely used in various control systems and become a highly competitive control tool in the field of automation. Its advantages are: high reliability and stability. However, the system structure of traditional PLC is closed, the hardware systems of various PLC manufacturers are incompatible with each other, and the programming language and instruction system are also different. When users choose a PLC product, they must choose its corresponding control procedures. The experimental data are more accurate, and learn specific programming language. Nevertheless, PLC is still used in many industrial applications. According to experts from arc, joint development company (VDC) and PLC training resource, 80% of PLCs are used for small applications (1 ~ 128I/O); 78% of PLC I/O is digital; 80% of PLC application problems can be solved by 20 ladder logic instruction sets. However, if we want to develop the remaining 20% of applications in the project, we have to break through the limitations of PLC

In the 1990s, with the continuous improvement and development of computer technology, people began to consider using PC for system control, in order to meet the remaining 20% of applications through PC and bring more choices to users. In many engineering applications, PC has been able to realize the control function of the original PLC. And it has the advantages of stronger data processing ability, powerful network communication function, the ability to execute more complex control algorithms and its almost unlimited storage capacity. However, PC based automatic control also has its shortcomings, its equipment reliability, real-time and stability are poor, and these three aspects are the problems that often need to be overcome in the industrial field

2. Characteristics and advantages of PAC control technology

because PC and PLC have their own advantages and disadvantages, people have developed new controllers to solve 20% of applications, and the characteristics of PLC and PC are best combined. The term PAC or programmable automatic controller was first adopted by arc consulting agency, a market research company. It defines a new type of controller, which is supported by a portable control engine and provides development tools with multiple functions. This controller combines the advantages of PC processor, ram and software, as well as the inherent reliability, robustness and distribution characteristics of PLC. In arc's "PLC World Survey" research, arc proposed five important characteristics of PAC. They are: ① multifunctional, with at least two logic, motion, PID control, drive and processing functions on a platform; ② A single multifunctional development platform uses general tags and a single database to access all parameters and functions; ③ By combining IEC61131-3, user guide and data management, software tools can design processing flows across multiple machines and processing units; ④ The open and modular structure can solve the industrial application from the layout of factory machines to the unit operation in the processing workshop; ⑤ The established network protocols and program language standards are adopted to ensure the network data exchange of users, such as TCP/IP, opc.xml and SQL query language

compared with traditional control technology, PAC technology mainly has the following advantages

1) adopt a single controller. PAC has a single controller, which can be used to process digital and analog I/O, and has motion vision function and modular instrument. Therefore, when users need vision and other functions, they do not need to buy other controllers

2) advanced control. Advanced control technologies such as fuzzy logic and neural network not only need powerful floating-point processor, but also need to occupy a lot of memory. PAC platform can meet these conditions

3) real time analysis. PAC can collect data from analog or digital I/O channels in real time, and analyze these data in real time, so as to effectively detect the fault state. Such as order tracking and vibration analysis to detect the running condition of the machine

4) safety. The data packets sent by PLC through Ethernet are unencrypted, so it is not suitable for preventing hacker intrusion. The packets sent by PAC can be encrypted. Although this is not the most important factor to consider at present, security will inevitably become an important aspect in the future

5) deterministic application of various speeds. PLC can only run at a fixed speed, so it cannot complete tasks independently at different speeds. The operating system running on PAC has such characteristics that it can carry out parallel processing

6) flexible memory function to achieve a long-term stable cooperative relationship. PAC has a module with upgradeable memory function, which allows users to execute the system to meet the current application requirements, and can be expanded in the future. PLC has only fixed memory capacity

7) machine vision. Due to the limitation of data transmission rate, visual function cannot be provided on PLC platform. PAC machine vision can detect product defects and errors that are difficult to measure using traditional methods

8) improve productivity. A general portable control engine and integrated engineering development platform allow rapid development, implementation and migration of project engineering; Moreover, because of its openness and flexibility, it ensures the seamless connection between control points and operations as well as enterprise business systems, optimizes the factory process, and improves production efficiency

9) reduce the operation cost. Due to the use of the general standard architecture and network, users can choose different system components from the perspective of cost, and the speech delivered by Ms. Wu Xian, chairman of wute shares, is not a proprietary product and technology; Users are only required to be trained on a unified platform and development environment, rather than learning a variety of special environments; It provides users with a seamless migration path and protects users' investment in I/O and application development

3. Solutions and main products of PAC control technology

from the definition, it can be seen that PAC is actually a systematic concept. It includes two parts: an integrated software platform and a hardware platform based on an open modular structure. PAC technology solutions also focus on these two aspects

generally speaking, there are two ways to provide PAC software: Software Based on PLC control and software based on PC control

1) software scheme based on PLC control. Most PLC manufacturers build PAC software by adding new functions to the existing scanning architecture. These new functions include Ethernet communication, motion control and advanced algorithms. Usually, they will retain the familiar programming mode of PLC and the inherent characteristics in logic and control. Therefore, this kind of PAC software is usually designed for special types of applications

2) software scheme based on PC control. In terms of PC, the main solution is realized by using real-time operating system (RTOS), such as VX works from WinDriver company in the United States. The real-time operating system can control all levels of the system, from the I/O read/write rate to the priority of each thread on the controller. And in order to make it easier for users to develop reliable control programs, manufacturers have added abstraction layer and I/O read-write architecture. Therefore, this flexible software is very suitable for customized control, data recording and communication applications

hardware solutions mainly rely on advanced CPU technology and open design (such as industrial Ethernet). According to Moore's law, the latest CPU has stronger data processing capacity when it is smaller and less power consumption. Thus, users can not only obtain a more stable and reliable CPU, but also obtain outstanding computing power. It also makes it possible for manufacturers to choose the standard embedded system structure for design, get rid of the limitations brought by the proprietary hardware structure system of traditional PLC, and make the system have richer functional prospects. The so-called openness is to adopt international standards or recognized industrial standards in product design, component selection, network communication, operating system, monitoring and display. Always think of standardization to make the products of different manufacturers compatible, interchangeable, and connected to the same network. Industrial ether is such a standard. Since its inception in 1975, the market share of Ethernet has reached 80%, and it is undoubtedly the leading network in the LAN (local area) field. Ether can be divided into many levels. Generally, it is not necessary to use ether in simple control systems, but it is very useful for complex systems, which is easy to operate, and can visually see the images everywhere

at present, many manufacturers have provided products that meet the characteristics and performance defined by PAC, of which the main application products are as follows

the PAC of GE Fanuc company is composed of an integrated software development platform Cimplicity machine Edition (me) and an open modular hardware platform PAC systems RX3i/7I. Me includes three software packages, as shown in Figure 1

Figure 1 Ge pac

where view is a human-machine interface toolkit, which realizes sca-da/HMI functions; Logic developer is a soft logic development package, which fully conforms to IEC61131 international standard and provides all necessary tools for developing, monitoring and debugging programs; Motion de veloper is a motion control development kit, which is used to ensure the development of motion control programs, and provides up to 100 motion control and complex control algorithm modules. In terms of hardware platform, GE Fanuc has launched two series of PAC systems RX3i/7I products

the PAC of Ni company is characterized by the integration of LavVIEW, a development platform widely used in the field of testing and measurement. The PAC system development software LabVIEW not only provides users with the compilation flexibility of creating complex measurement and control systems, but also becomes very easy to use because of its intuitive graphical development interface. In LabVIEW, users can use hundreds of built-in control and analysis functions to quickly develop various complex programs. Users can also call the program codes developed by other software in LabVIEW to process I/O, motion control, machine vision, instrument communication and other applications. PAC system development hardware includes compact FieldPoint, compactrio, compact VI sion system and industrial PC. As shown in Figure 2

Figure 2 Ni PAC

the main products of icpdas Hongge technology PAC are wincon/Lincon. The operating system of wincon is windows; Lincon's operating system is embeddedlinux. Wincon supports serial connection, Ethernet network connection and parallel connection; The software package of soft logic PLC and embedded view and other suite monitoring systems are provided; OPC and MODBUS are used for data communication; Have standard relational database; And you can use visual and other tools to develop programs by yourself

in addition to the above typical products, there are other companies

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