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What is PROFIBUS?
Introduction to PROFIBUS
PROFIBUS, short for Process Field Bus, is a standardized protocol for communication via fieldbus in automation technology. Unveiled in 1989 by the German Federal Department for Education and Research, its goal was to provide a robust, efficient and flexible communications protocol for a multitude of industrial applications. It was later developed in the 1990s by Siemens, establishing a vital communication channel between various equipment within a factory, thereby facilitating production and optimizing the use of resources.
The importance of PROFIBUS in the industrial sector is notable. It is designed to efficiently meet the varied needs of automated installations. Its versatility explains why PROFIBUS is widely used in various industrial sectors, ranging from automotive to cement plants, food processing and water treatment.
Advantages of PROFIBUS
Efficient communication between industrial equipment is one of the major advantages offered by PROFIBUS. By connecting various measurement equipment to control systems such as automation, regulation and supervision, it facilitates the coordination and optimization of industrial processes. In addition, PROFIBUS is available in three variants, Profibus-FMS (Fieldbus Message Specification), Profibus-DP (Decentralized Peripheral) and Profibus-PA (Process Automation), each adapted to specific needs in industrial communication in automation, thus ensuring flexibility and adaptability to the changing requirements of industrial environments.
Improved production and optimized use of resources are also key advantages of PROFIBUS. By enabling smooth and reliable communication between equipment, PROFIBUS helps minimize downtime, increase productivity and optimize resource utilization, resulting in more efficient operations and improved profitability.
What are the key components of PROFIBUS?
Profibus-FMS
Profibus-FMS, where FMS stands for Fieldbus Message Specification, is an early implementation of the PROFIBUS protocol designed around 1987, enabling peer-to-peer communication between PROFIBUS programmable logic controllers (PLCs) (masters). This variant was more complex and intended for highly communicative tasks, providing non-deterministic communication between PROFIBUS masters. Profibus-FMS was suitable for cell- and field-oriented data exchange.
Although Profibus-FMS has largely been replaced by industrial Ethernet communications, at its peak it facilitated communication between programmable controllers and PCs with complex messages, serving as the basis for advanced industrial communications.
PROFIBUS DP
Profibus DP (Decentralized Peripherals) is a newer version than FMS, designed for communication between the control level of a process automation system (PLC) and the decentralized periphery in the field. It is capable of reaching speeds of up to 12 Mbit/s, facilitating fast and reliable communication between the different components of an industrial system. The physical layer of PROFIBUS DP is RS-485, making it suitable for handling robust communications in diverse industrial environments.
PROFIBUS DP is widely used to connect controllers to peripherals such as sensors and actuators in various industrial installations, enabling real-time data collection and precise process control.
PROFIBUS PA
Profibus PA (Process Automation) is designed as an alternative to 4-20 mA analog cabling, and defines a secure communication protocol based on the seven layers of the OSI model, while taking over the services of the DP protocol for management applications field sensor/actuator instrumentation. It uses a physical layer called Manchester Encoded Bus Powered (MBP) to facilitate communication between devices in industrial environments.
PROFIBUS PA is particularly useful in the process industry where it enables reliable and secure communication between measurement and control devices, thereby facilitating the automation of industrial processes. It is widely used to connect measurement equipment with control systems in process engineering applications, providing an effective solution for resource management and productivity improvement.
What is the difference between PROFIBUS and PROFINET
Comparison with PROFINET
PROFIBUS and PROFINET, although originating from the same organization, are two separate, widely deployed automation protocols, each with their own unique characteristics. PROFIBUS is a classic serial fieldbus, often characterized by single-pair, purple-colored RS-485 cables. It operates at a speed of 12 megabits per second and supports Master/Slave communication. On the other hand, PROFINET is an industrial Ethernet standard, typically characterized by green industrial Ethernet cables, operating at a speed of 100 megabits per second and supporting Supplier/Client type communication.
The choice between PROFIBUS and PROFINET depends on the specific needs of an installation. PROFINET, with its faster and flexible communication, is generally preferred for applications requiring high bandwidth and easy integration with existing IP networks. On the other hand, PROFIBUS may be more suitable for existing installations with serial communication needs.
Transition to PROFINET
Migration from PROFIBUS to PROFINET is a process that can be simple or complex depending on the specific installation configuration. There are established strategies to ease this transition while minimizing disruption.
The first step traditionally consists of establishing communication between PROFIBUS (or other fieldbus) networks and Ethernet (PROFINET) networks using PROFIBUS to PROFINET proxies. These proxies allow transparent communication between the two networks, making the transition easier.
When planning the migration, it is crucial to consider the complexity of project management, particularly in terms of equipment compatibility, staff training and upgrading existing infrastructure. Migrating to PROFINET provides a seamless upgrade to existing installations and has the benefit of leveraging the open nature and flexibility of the future-proof PROFINET standard.
How to implement PROFIBUS?
Norms and Standards
PROFIBUS is a standardized and open digital communication system, applicable in various areas of manufacturing and process automation. Although there is no exhaustive list of international and regional standards, it is essential that PROFIBUS implementations adhere to the specifications set forth by the PROFIBUS & PROFINET International (PI) organization.
Deployment of the PROFIBUS Network
The deployment of the PROFIBUS network requires particular attention to cabling. For PROFIBUS PA, for example, shielded twisted pairs are used for both power and communication, and its physical network structure complies with IEC-61158-2, with high network data rate of 31.25 kbit/s. The PROFIBUS DP standard, on the other hand, is often characterized by purple-colored single-pair RS-485 cables, with standard DB9 or M12 connectors, and operates at a speed of 12 megabits per second.
Access and Communication
Communication on the PROFIBUS network is primarily done using the master/slave method, where a master device controls and initiates communication with slave devices on the network. This method allows efficient management of traffic on the network, thus ensuring reliable and real-time communication between the different connected devices. Additionally, versions like PROFIBUS DP V1 support cyclic communication and message communication, thus enabling enhanced features like a motion control network with PROFIBUS DP V2.
This implementation of PROFIBUS, although standardized, provides sufficient flexibility to adapt to the specific requirements of various industrial applications, thus making PROFIBUS suitable for a wide range of deployment and communication scenarios in the industrial automation sector .
What is the future of PROFIBUS?
PROFIBUS continues to evolve to meet changing industry requirements. Current trends are directing the evolution of PROFIBUS toward field automation, integrating security features into the network, and toward interconnecting PROFIBUS networks to a backbone network via TCP-IP protocols. Continuing technical developments ensure that PROFIBUS remains a future-ready industrial communications system, with a particular emphasis on integration with other industrial technologies and standards such as Industrial Ethernet and PROFINET.
With the progression towards Industry 4.0, the integration of PROFIBUS with other technologies such as PROFINET and Internet of Things (IoT) will continue to evolve, providing expanded possibilities for industrial automation and optimized industrial process management.
Conclusion
The crucial role of PROFIBUS in industrial automation and communication between equipment is undeniable. Its ability to adapt to the varied requirements of automated installations, while providing robust and efficient communication, makes it a preferred choice for professionals in the sector. Additionally, the different variants of PROFIBUS, namely Profibus-FMS, Profibus-DP, and Profibus-PA, enrich its versatility and enable wide application in various industrial sectors.
The constant evolution of PROFIBUS, including its integration with other technologies such as PROFINET and the Internet of Things (IoT), as well as its readiness to embrace the challenges of Industry 4.0, demonstrates its continued relevance in an industrial environment rapidly evolving. The transition to PROFINET, for example, symbolizes a logical step towards leveraging Ethernet technologies, paving the way for faster communications and easier integration with existing IP networks.
