Development of a Network Analyzer for PROFINET Standard

Transcription

1 Development of a Network Analyzer for PROFINET Standard Egidio Raimundo Neto, João Paulo Martins Semensato, Luiz Felipe Pereira Duarte, Marcelo Augusto Vilas Boas, Maria Teresa de Carvalho Silva, Alexandre Baratella Lugli and João Paulo Carvalho Henriques Keywords Industrial Network, Network Analyzer, PROFINET, frame. Abstract - This work presents the development of a network analyzer for PROFINET standard. A network analyzer using a low cost platform composed by a Raspberry Pi and a software developed in Python is present. This network analyzer is connected in a PROFINET industrial network to get all information that are transmitted and received by each element that is connected on. This information is separated in PROFINET frames and each part of the frame is identified. Is possible to identify the source address, destination address, frame ID, PROFINET IO data, cycle counter, data status and other information depending of the equipment type. To validate the analyzer efficiency, a real PROFINET network composed by a master and multiple slaves is implemented in a laboratory, and frames were identified from the master to all slaves and from all slaves to the master. Besides that, the real PROFINET network is implemented with elements from different companies to ensure that the network analyzer is compatible with any types of elements from any company. The results are presented and for future work is proposed the development of an intelligent system to classify faults and suggest actions for the network operator using artificial intelligence techniques. 1. Introduction The first experiments testing the connection and exchange of data between computers was done in 1965 by the American scientists Lawrence Roberts and Thomas Merril. These experiments originate the first networks, which underwent several technological innovations until reaching the current networks. With the technological improvements, the networks passed to be applied on the most distinct areas, being one of them the industrial sector, where they received the nomination of Industrial Networks [1]. PROFINET standard has become the leading Industrial Ethernet Standard in the market. This is globally established and future-oriented technology is supported by many product vendors, thus ensuring long-term availability and investment protection. The number of PROFINET devices in use in the market has increased above average in recent years: 20.9 million devices were installed by the end of 2017, and the number continues to growing [2]. The PROFINET standard uses the same Ethernet as offices and Information Technology (IT) departments. However, its capabilities have been enhanced to meet the far tougher conditions encountered in industrial applications. Whether the application involves factory automation, process automation, or drives, PROFINET standard is the first choice across the board. As technology that is standard in the automotive industry, widely spread in machine building, and well-proven in the food and packaging and logistics industries, PROFINET has found its way into all application areas [3]. Some advantages PROFINET are that all communication requirements covered, flexible network topology, increased availability, functional safety deeply integrated, and uniform integration on fieldbus systems. Currently there are several technologies of the Industrial Network in the market, which vary according to application and manufacturer. Therefore, PROFINET can be organized into different topologies and act on some different physical medium. Thus, this work presents the PROFINET characteristics, an example of practical application of PROFINET, the development and tests of a low cost

2 PROFINET analyzer. This practical application allows test the efficiency of the PROFINET analyzer that is the main contribution of this work. 2. Industrial Networks and Protocols 2.1.AS-I The Actuator Sensor Interface (AS-I) network is a very simple network that is usually connected to other higher-order ones such as (Process Fieldbus) PROFIBUS. This connection is possible using network gateways. Network gateways are devices that convert from one network to another, so that they can exchange information between them regardless of the type of architecture they use. The AS-I is also made up of controllers containing the network programming and configuration software, which play the role of the master. As a slave, this network includes sensors, actuators and I/O modules, as well as cables and AS-I source, and it is possible to implement repeaters and network terminators [4]. The communication in this network is carried out through the AS-I cable, which are unshielded cables that have two wires, in which the information and power are transferred to the slaves. The transmission of the digital data of this architecture goes through three stages, being telegram assembly, Manchester coding and Alternating Pulse Modulation (APM). It is also possible to organize the network in different topologies, as in the figure 1. Figure 1. AS-I Topologies: Star, Line, Bus and Tree. As time passed, there was a need to increase the numbers of slave networks that led to the appearance of two more versions of AS-I, so that it can then be found in three types 2.0, 2.1 and 3.0 [4] PROFIBUS The PROFIBUS is the fieldbus-based automation standard of PROFIBUS & PROFINET International (PI) [5]. Via a single bus cable, PROFIBUS links controller or control systems with decentralized field devices, as sensors and actuators, on the field level, and also enables consistent data exchange with higher ranking communication systems. Consistency of PROFIBUS is enabled by utilizing a single, standardized, and application-independent communication protocol, named PROFIBUS DP, which, without any difference, supports fieldbus solutions both in factory and process automation as well as in motion control and safetyrelated tasks. PROFIBUS combine application-specific modules for transmission, application and engineering to form complete PPROFIBUS solutions for specific market segments, as shown in figure 2.

3 Figure 2. PROFIBUS applications possibilities[2] To ensure correct interaction between the numerous devices of an automation solution, the basic device functions and services must match concerning communication, functionality and industry sector solutions. This uniformity is achieved application profiles which refer to device families or special industry sector requirements, as process automation (PA), Motion Control (PROFIdrive) or integration of HART devices (HART on PROFIBUS) [6]. In figure 3, PROFIBUS DP is in the central position and carries communication data between a controller and field devices, preferably in Factory Automation (FA). Downwards, a PROFIBUS PA string is connected through a coupler or linking device to enable typical process automation (PA) applications, as in a hazardous enviroments. Upwards, the controller is connected to PROFINET as system bus and interface to MES (Manufacturing Execution System) and ERP (Enterprise Resource Planning) levels. PA segments can also be connected directly to PROFINET using proxy technology [5]. Figure 3. PROFIBUS applications and interoperability with PROFINET [5]. The PROFIBUS is based on the Open System Interconnection (OSI) model, although its versions do not make use of all the 7 layers. Adaptation of this model, for example PROFIBUS DP uses the layer 1,2,3 and 7 while PROFIBUS PA uses 1,2 and 7. The PROFIBUS network can be found by working on two types of physical media: RS485 or fiber optics. In the DP version can be seen the use of two different types of cables, but both in purple color. This architecture is still highly flexible, being able to work with multiple masters and also be integrated with other networks such as the AS-I or PROFINET network, shown in the figure 4 and figure 5.

4 Figure 4. PROFIBUS and AS-I application [5]. Figure 5. PROFINET and PROFIBUS application [5]. 2.3.PROFINET The Globalization is opening up completely new growth opportunities for companies and researchers. Therefore, this also entails new challenges as standing up to global competition in the long run necessitates the rapid production of high quality as well as reliable maximum plant availability. Characteristics as flexibility, productivity and efficiency also represent decisive success factors for company, which can be optimized on the basis of PROFINET. The PROFINET is an open Industrial Ethernet-based standard developed and maintained by PI. The PROFINET is standardized in IEC and IEC and, as a universal communication technology, covers all requirements of automation technology. The PROFINET is totally switched Ethernet according to IEEE and is thus also open for application of all Ethernet technologies and parallel operation of multiple Ethernet protocols [7].

5 Some advantages of use PROFINET is that in Industrial Wireles LAN (IWLAN) ensures reduced maintenance costs, increased reliability as well as a high-performance communication. Only PROFINET allows the combination of safety and IWLAN. Also, safety-related communication via PROFIsafe ensures the reliable protection of persons, environment and plants. For PROFINET no special network components are required as standard switches and gateways can be used without restrictions, supports the expansion of network infrastructures as required, also during ongoing operation. The openness of PROFINET creates the basis for a uniform automation network for machines and plants to which both automation as well as conventional Ethernet devices can be connected. PROFINET is 100 percent Ethernet and supports TCP/IP. Amongst others, this facilitates the utilization of web technologies such as access to the field devices integrated web server. In addition to line structures, PROFINET also supports star, tree and ring structures. This results in a high degree of flexibility. The PROFINET network can be installed without any special expert and complies with all relevant requirements in industrial environments [8] Topologies The topologies that are supported by PROFINET standard are show in figure 6. Figure 6. PROFINET topologies [8]. The Line topology, which primarily connects field devices with integrated switches in the field, star topology with a central switch located in the control cabinet, ring topology, primarily for implementation of media redundancy, and tree topology, in which the topologies listed above are combined make PROFINET flexible and smart. The connection of PROFINET devices is carried out exclusively using switches as network components, which are often already integrated in the device. The nodes are connected by copper cable up to a distance of 100 m. For longer transmission distances, fiber-optic cables are used [7] Physical Medium The PROFINET standard uses shielded twisted pair and fiber optic as the physical medium. In some applications where the cables and the fibers characterize an obstacle, it is possible to use the wireless. The physical medium has the following characteristics in Table I.

6 Table I. PROFINET PHYSICAL MEDIUM CARACTERISTICS AND BIT RATES [7] Cable Type Bit Rate Maximum Range without repeaters Maximum number of elements Shielded twisted pair 10BASE-T 10 Mbps 100m 1024 Shielded twisted pair 100BASE-T Shielded twisted pair 1000BASE-T 100 Mbps 100m Mbps 1000m 1024 Optical Fiber 10BASE-FL 10 Mbps 2000m 1024 Optical Fiber 100BASE-FL 100 Mbps 2000m Devices PROFINET has three types of devices: controller (IO Controller), field modules (IO Device) and supervisory systems having the following characteristics [7]: Controller (IO Controller): Central system, where information is controlled; Field Modules (IO Device): Remote field devices that maintain communication with a controller; Supervisory systems: A graphical, programmable device that commission and has a diagnostic function in the network; Communication Modes PROFINET can operate in three distinct ways, two of them for real-time and one for non-real-time access, which operate as follows [7]: TCP / IP: This architecture is called Non-real time because the processing time is equal to 100ms. Used mainly in parameterization, configuration and diagnosis; Real-time RT: An architecture directly interconnects the Ethernet layer to the application. With the elimination of several levels of protocol, there is a reduction in the length of transmitted messages, requiring less time to transmit the information on the network. Its main objective is the cyclical transmission of data, such as alarm and event signals; Isochronous real-time (IRT): This configuration is used in applications where the processing time is very important, this time with variations smaller than 1us such as the control of robots (mechanical arms); Figure 7 illustrate applications for each communication mode.

7 Figura 7. PROFINET Communication modes [8]. 2.4.Proposed System Network analyzer A low cost PROFINET network analyzer was developed using a Raspberry Pi and all algorithms were implemented using Python. The network analyzer function is get any PROFINET frame and provide this information for the user. The Python code based on the Socket library is capable to capture all transmitted packets traveling on the network. To filter this packets a function is used to select only PROFINET frames using the Ethernet Type as known as Ether-Type, in case of PROFINET the Ether-Type is 0x8892 [7]. Also, is possible to separate source and destination MAC addresses. All information about the frames is show in a terminal screen and the user can analyze and complain all. Figure 8 shows part of the main algorithm structure with the filter functions. Figure 8. Part of main algorithm structure. It is important note that the network analyzer needs to be connect on a manageable switch to have access to all packets that traffic on the network. To provide correct and properly information for the user, the next step is unpack the PROFINET packet. Figure 9 show another part of main algorithm with the functions to unpack and format the information before show it on the terminal screen.

8 Figure 9. Part of main algorithm structure Network Topology To evaluate the network analyzer performance, a practical network with devices from different companies is propose. Figure 10 show the network elements. A Programmable Logic Controller (PLC), two I/O (Input/Output) modules from different companies, a manageable switch, a Raspberry Pi and a monitor are used to implement the setup. Figure 10. Setup implementation. The elements setup, configuration and topology are show in figure 11. The network analyzer and manageable switch are transparent for the application in this case.

9 Figure 11. Setup configuration. 3. Tests and Results The network analyzer is able to show all Ethernet frames and the main information for each one as show in figure 12. The destination and source MAC addresses, the protocol Ether-Type and the frame data are show in real time on the monitor screen. Figure 12. Real time monitor screen. To validate the analyzer efficiency a comparison between the frames obtained with the network analyzer and a commercial software that is capable to unpack the information of any Ethernet frame types is use. Is important note that this commercial software are not able to segment the information and specify the content of each frame stretch.

10 Figure 13 shows a comparison between the upside with filtered information using the proposed network analyzer and the downside without information treatment obtained using a commercial software. Note that the total information is the same, but using the network analyzer is possible to separate the desired information in specific variables according with the user necessity. With the commercial software, the user needs to separate the information manually, and for this option a previous knowledge is need, to highlight and differentiate each frame stretch as show on downside. Figure 13. Comparison between the network analyzer and commercial software. To observe this in a dynamic information exchange the circled in red byte that represents the digital IO data of a module will be change. In this case, the master program sets a digital output of the IO module by true and a new frame after this is show in figure 14. Note that the information of this byte changes from 00h to 01h and the frames obtained with the network analyzer and the commercial software is the same. Figure 14. Comparison between the network analyzer and commercial software after byte change. Conclusions A low cost PROFINET network analyzer was developed using a Raspberry Pi and a Python code running in a Linux operational system. This analyzer is able to filter PROFINET packets on the Ethernet network and unpack the main information about this packets separating destination and source MAC addresses, Ether-Type code and the data frame. With this data is possible to identify all information transmitted and received by each network element. This network analyzer can help teachers and tutors during our classes and allows the contact of professionals and students with real time examples and applications.

11 The next step is implement more filter functions capable to extract specific information of each data frame. It will allow the use of this information to detect, analyze and treat fails on the network devices and medium. Other important step is use of artificial intelligence technologies to implement the previous step. In this way, an autonomous PROFINET network analyzer will help the system maintenance to provide fast troubleshoot and grow the system efficiency. References [1] Tanenbaum, A. S.; Whetherall, D. J; Computer Networks, 5 th ed., Prentice Hall, [2] Profibus International. (2018). Profinet Overview. Available online at [3] Profibus International. (2018). Profinet Case Studies. Available online at [4] Lugli, A. B. e Santos, M. M. D. Redes Industriais para Automação Industrial: AS-I, PROFIBUS e PROFINET. São Paulo, Editora Érica, 1st ed., [5] Profibus International. (2018). Profibus Overview. Available online at [6] Lugli, A. B.; Henriques, J. P. C. ; Santos, M. M. D. ; Silva, F. R.. Automation Integrated Using PROFIBUS and Supervisory System. International Journal of Innovative Computing, Information & Control, v. 12, p , [7] Popp, M.; Industrial communication with PROFINET, Profibus International, [8] Profibus International. (2018). Profinet Standard. Available online at