Keywords: PROFInet, TCP/IP, OPC, DCOM 1 Introduction With the rapid development of information technology, the development of automation technology is increasingly influenced by the principles and standards of information technology. Integrating information technology in the field of automation can provide solutions for global communication between internal automation systems. PROFInet communication technology, based on the industrial Ethernet communication standard, makes this integration possible. PROFInet, short for Process Field Net, is a fully open communication protocol between PROFIBUS and Ethernet, launched by PROFIBUS customers, manufacturers, and the System Integration Alliance. PROFInet is an automation solution based on real-time industrial Ethernet, including a complete set of high-performance and scalable solutions. It provides Ethernet migration services for PROFIBUS and various other fieldbus networks. The openness of the PROFInet standard ensures its long-term compatibility and scalability, thereby protecting users' investment and interests. PROFInet makes engineering, configuration, commissioning, operation, and maintenance more convenient, and can achieve seamless integration and connection with PROFIBUS and other fieldbus networks. Engineering practice has proven that using PROFInet communication technology when building an enterprise industrial control network can save nearly 15% of hardware investment. 2 PROFInet Communication Standard PROFInet provides open and consistent connectivity for office and automation applications. The PROFInet solution covers all operational phases of distributed automation systems and mainly includes the following aspects: (1) an open object model (structural model) for highly distributed automation systems; (2) an open, object-oriented runtime communication solution based on Ethernet (communication relationships between functional units); and (3) a manufacturer-independent engineering design solution (application development). The PROFInet solution can be simply and clearly described by the equation: PROFInet = PROFIBUS + open and consistent communication with PROFIBUS and the IT standard Ethernet. 2.1 Software Structure of PROFInet Devices The software of PROFInet devices covers the entire runtime communication of field devices. The modularly designed software contains several communication layers, each consistent with the system environment. The PROFInet software mainly includes an RPC (Remote Procedure Call) layer, a DCOM (Distributed Component Object Model) layer, and a layer specifically defined for PROFInet objects. PROFInet objects can be ACCO (Active Connection Control Object) devices, RT auto (Runtime Automation) devices, physical devices, or logical devices. The real-time data channel defined in the software provides real-time communication services between PROFInet objects and Ethernet. PROFInet connects to the operating system (such as WinCE) through the system interface and to the controller (such as a PLC) through the application interface. The PROFInet runtime software resides in a fixed directory structure, which can be divided into a core directory and a system application directory. If communication begins and the files in the core directory have not changed, some files in the system application directory must be rebuilt. All system applications point to the system interface and application interface to implement the various functions of the PROFInet device. The software structure of the PROFInet device can be described by Figure 1 as follows: [align=center][img=406,348]http://www.chuandong.com/uploadpic/THESIS/2008/4/2008040709403644614Y.jpg[/img] Figure 1 PROFInet device software structure[/align] The software structure of the PROFInet device determines that the PROFInet device can be accessed directly and transparently from the enterprise management level to the field level, and provides absolute support for the TCP/IP protocol. PROFInet technology enables enterprise users to easily extend and integrate existing systems, and is an optimized industrial Ethernet communication standard. 2.2 Porting PROFInet to Field Devices As an open resource, PROFInet software can be quickly and easily implemented in other device manufacturers' products by porting it to the TCP/IP protocol stack on the device. The specific process is as follows: First, connect the open resource's RPC interface to the TCP/IP protocol stack and the system integration in the device's operating system; then, integrate the PROFInet protocol stack's DCOM (Discrete Component Object Module) mechanism into the device's operating system; finally, implement device-specific DCOM applications for physical and logical device objects, runtime objects, and active control connection objects. When assembling a PROFInet device for a single component, a corresponding description must also be created using XML. The XML file of a PROFInet device should include the following data: (1) the name and ID number of the PROFInet device; (2) the IP address of the PROFInet device, the access method for diagnostic data, and the device connection method; (3) the hardware allocation of the PROFInet device, the device interface, and the variables, data types, and formats defined for each interface; (4) the storage address of the PROFInet device in the entire project. A PROFInet device encapsulates all its functions within its software and provides a variable interface to connect with other PROFInet devices. Each variable in the variable interface represents a specific sub-function, including run, input/output enable, reset, stop, stop, start, and error. A PROFInet device can encapsulate a controller, an actuator, or even a control network. Figure 2 shows a PROFInet device that encapsulates a PROFIBUS-DP control network. [align=center][img=428,189]http://www.chuandong.com/uploadpic/THESIS/2008/4/2008040709404122724A.jpg[/img] Figure 2 Encapsulation of a PROFInet device[/align] PROFInet devices communicate with each other via DCOM modules. Connections between PROFInet devices can be easily implemented in the graphical interface of the PROFInet device connection editor. The production process of a beverage manufacturer with four stages—rinsing, filling, sealing, and packaging—can be implemented by connecting four PROFInet devices in series (see Figure 3). [align=center]Figure 3 Connection of PROFInet Devices[/align] All device interfaces are uniformly defined in PROFInet, allowing for flexible combination and reuse without requiring users to consider the internal operating mechanisms of individual devices. Furthermore, PROFInet integrates the fail-safe communication standard PROFIsafe, meeting comprehensive safety requirements for personnel, equipment, and the environment, and can be used in fail-safe applications. 3 Implementation of PROFInet Communication Functions The implementation of PROFInet device communication functions is based on traditional Ethernet communication mechanisms (such as TCP or UDP), while also employing RPC and DCOM mechanisms for enhancement. DCOM can be considered an extension of COM technology for RPC-based distributed applications, allowing for optimized real-time communication mechanisms in applications with stringent real-time requirements. During operation, PROFInet devices are mapped as DCOM objects, and communication of DCOM objects is ensured through object protocol mechanisms. COM objects appear on the communication bus as PDUs defined by the DCOM protocol. The DCOM wiring protocol defines the object's identifier and methods with relevant interfaces and parameters, enabling standardized transmission of DCOM packets on the communication bus. For higher-level communication, PROFInet can utilize integrated OPC (OLE for Process Control) interface technology. 3.1 Basic Communication Methods of PROFInet PROFInet defines three different communication methods for different applications: standard communication using TCP/IP; real-time (RT) communication; and synchronous real-time (IRT) communication. PROFInet devices can select the appropriate communication method based on communication requirements. PROFInet uses Ethernet and TCP/IP protocols as its communication foundation, providing absolute support for TCP/IP communication in all situations. Since most factory automation applications have high requirements for real-time response time, PROFInet specifies an optimized real-time communication channel based on Ethernet Layer 2 to meet the real-time requirements of automation. This scheme greatly reduces the time occupied on the communication stack and improves the performance of automation data refresh. PROFInet not only minimizes the communication stack in the programmable controller but also optimizes data transmission over the network. Using the PROFInet communication standard, the system response time for real-time applications can be shortened to 5–10 ms. PROFInet also supports high-performance synchronous motion control applications, where it provides synchronous real-time (IRT) communication with a response time of less than 1ms for 100 nodes. This functionality is provided by the ERTEC synchronous real-time switching chip embedded on Layer 2. The PROFInet communication cycle is shown in Figure 4. [align=center][img=434,163]http://www.chuandong.com/uploadpic/THESIS/2008/4/20080407094049246462L.jpg[/img] Figure 4 PROFInet Communication Cycle[/align] A single communication cycle of a PROFInet device includes both IRT real-time communication and TCP/IP standard communication. PROFInet communication technology demonstrates its significant advantages in many applications. Engineering practice shows that in synchronous motion control applications, using PROFInet's IRT communication improves system performance by nearly 100 times compared to using a fieldbus solution. 3.2 Integration of PROFInet and OPC Since both PROFInet and OPC adopt the DCOM communication mechanism, PROFInet communication technology can be easily integrated with OPC interface technology to achieve data exchange at a higher communication level. OPC interface devices are widely used in the industrial control field. OPC interface technology defines two communication standards, OPC DA (Data Access) and OPC DX (Data Exchange), which are used to transmit real-time data and realize the exchange of data between heterogeneous control networks, respectively. Integrating the OPC DX interface into PROFInet can realize an open connection to other systems. The integration mechanism is as follows: (1) Based on the real-time communication mechanism of PROFInet, each PROFInet node can be addressed as an OPC server; (2) Each OPC server can be operated as a PROFInet node through the standard interface. The functionality of PROFInet is far superior to that of OPC. The integration of PROFInet technology and OPC interface technology can not only meet the requirements of real-time communication in the field of automation, but also realize interaction between systems at a higher level. 4 Application of PROFInet in the field of automation PROFInet is a superior communication technology and has been successfully applied to distributed intelligent control. PROFInet opens up new prospects for the implementation of distributed automation system architectures, enabling complete modularization of plant-wide engineering, including mechanical components, electrical/electronic components, and application software. PROFInet supports various network structures, minimizing wiring costs and ensuring high availability. Furthermore, specially designed industrial cables and durable connectors meet EMC and temperature requirements and are standardized, ensuring compatibility between different manufacturing equipment. PROFInet is not only applicable to distributed intelligent control but is also increasingly entering the field of process automation. In the field of process automation, PROFInet is developing into standards or solutions for addressing the issues of power supply to industrial Ethernet buses and the application of Ethernet in security. PROFIBUS fieldbuses integrated with PROFInet can provide superior solutions for industrial process automation (as shown in Figure 5): [align=center][img=426,238]http://www.chuandong.com/uploadpic/THESIS/2008/4/2008040709405262725C.jpg[/img] Figure 5 Application of PROFInet in the field of process automation[/align] Using PROFInet communication technology, not only can PROFIBUS field devices be integrated, but other types of fieldbus networks can also be integrated through proxy servers. Adopting this unified, future-oriented design concept, components within the factory can be pre-assembled and tested as independent modules, and then easily assembled into the entire system or reused in other projects. For example, for an automobile manufacturing company, the real-time solutions supported by PROFInet can fully meet the response time requirements of the body shop, paint shop, and assembly department. In mechanical engineering and engine and transmission production processes, such as lathe synchronization, PROFInet's real-time synchronization function can be used. [img=462,137]http://www.chuandong.com/uploadpic/THESIS/2008/4/2008040709405796343P.jpg[/img] 5 Conclusion PROFInet can guarantee a high degree of protection for existing system investments and give factories the advantage of innovative standards. Given the superiority of PROFInet communication technology, some manufacturers (such as Siemens and Schneider Electric) have already begun to provide PROFInet interfaces for their equipment. As a new generation of industrial Ethernet communication standard, PROFInet is entering field-level applications at an unprecedented speed.