PROFINET offers a distributed I/O capability that is similar to PROFIBUS but it offers more flexibility, more power, more opportunities and hence has far greater automation potential.
Because it’s based on Ethernet, PROFINET facilitates the integration of manufacturing operations enterprise-wide, helping realize compelling business advantages. PROFINET can even integrate existing fieldbus networks easily (see right) helping protect existing investments as plants migrate towards an Ethernet future.
PROFINET is the automation standard of PROFIBUS&PROFINET International (PI). PROFINET is 100% Ethernet-compatible as defined in IEEE Standards. With PROFINET, the following minimum data communication requirements are automatically established:
• 100 Mbps data communication with copper or fiber optic transmission (100 Base TX and 100 Base FX)
• Full duplex transmission
• Switched Ethernet
• Auto negotiation (negotiating of transmission parameters)
• Auto crossover (sending and receiving lines are crossed in the switch)
• Wireless communication (WLAN and Bluetooth)
PROFINET uses UDP/IP as the higher level protocol for demand oriented data exchange. UDP (User Datagram Protocol) contains the no secure, connectionless broadcast communication in conjunction with IP.
In parallel to UDP/IP communication, cyclic data exchange in PROFINET is based on a scalable real-time concept.
EMBRACING THE BEST OF FIELDBUSES
PROFINET does not offer a direct process automation connection because the fieldbus solution provided by PROFIBUS PA already delivers a highly successful alternative. Instead, PI offers an easy way to integrate existing PROFIBUS PA networks into PROFINET. Not only does this allow current investments to be fully utilized, it also means PROFINET can become the platform for enterprise-wide integration of process plants so that ERP and MES functions can be more effective.
Connectivity between PROFINET and PROFIBUS PA is achieved using a ‘proxy’ or ‘black-box’ solution for connecting the two networks (see above – click image to get a larger version).
The ‘proxy’ solution is one of the strongest differentiators for PROFINET. It can be used to include other networks in a PROFINET system and proxies exist for PROFIBUS PA and most major fieldbus competitors.
AUTOMATION POWER, RIGHT ACROSS THE ENTERPRISE
PROFINET offers a distributed I/O capability that is similar to PROFIBUS but it includes more flexibility, more power, more opportunities and hence far greater automation potential.
PROFINET’s basic communications services support three modes of operation, each aimed at different automation sectors. They can be used independently, or in combination, one of the factors making PROFINET so modular and flexible and ideal for all aspects of factory automation.
PROFINET fully supports TCP/IP communications while delivering a scalable real time solution. This ability to fully support all required applications areas – the ability to ‘talk’ across networks and upwards into IT, plus the real time functionality needed for factory floor automation and motion control – ensures that PROFINET can meet all the needs of manufacturing, enterprise-wide.
REASONS FOR USING PROFINET
- Seamless enterprise-wide integration, global accessibility.
- Unlimited node count, powerful capabilities, greater scalability.
- Full TCP/IP, internet and web compatibility, with real-time determinism
- Ethernet cabling eases installation, and familiar IT and Internet tools help during operation, maintenance and diagnostics.
- Wireless and functional safety easily added.
- Protects investments in plant and people by easily integrating all popular automation networks.
- Strategic links with PROFIBUS include common infrastructure, common engineering platforms, common quality assurance and common application profiles.
- Modular, flexible, comprehensive – use only what you need now.
- Easily extended and expanded as enterprise needs change.
Power and communication via a single cable
Like conventional 4-20 mA or HART communication technologies, fieldbus technology supports the simultaneous transmission of power and communication data via a single cable, even in potentially explosive atmospheres. Furthermore, with wiring overheads significantly reduced, it meets the requirements for simpler and safer installation and boasts all the benefits of digital transmission.
IEC 61158-2 defines MBP (Manchester-encoded, Bus Powered), as a transmission technology satisfying all requirements of and developed specifically for the needs of process automation. This transmission technology makes it possible to supply power to the connected devices directly via the bus medium. MBP is characterized by the following features:
- Transfer rate: 31.25 kbps
- Transmission technology: Half duplex, synchronous, self clocking, with Manchester biphase L encoding
- CRC (cyclic redundancy check)
- Data security: Preamble, failsafe start-end delimiters
- Cable: Shielded, twisted pair line (type A or type B)
- Topology: Line and tree topology with termination; combined topology possible
- Number of stations: Up to 32 stations per segment
- Ignition protection: Several methodologies and technologies
- Explosion protection is implemented via power limiting of the incoming bus supply as well as installation components in the field. Live maintenance on field devices during plant operation is made possible, for example, by means of intrinsically safe explosion protection. The easiest way to verify intrinsic safety of a segment is to use the FISCO model. In this case, since all components used comply with FISCO standards simple comparisons of power voltage and current eliminate further calculations.
PROFIBUS PA offers quite flexible installation concepts which, thanks to the advanced installation technologies available on the market, can lead to incredibly robust systems. In principle, all topologies are supported.
However, in practice, the trunk & spur topology has established itself as the de facto standard due to the fact that it is so clear and easy to understand and maintain. The total length of a segment in the most ideal situation must not exceed 1,900 meters.
Transmission conditions for PROFIBUS PA can be optimized by using type A cable consisting of a single shielded, twisted pair. All segments must be terminated correctly with terminating resistors (“T”). These terminations are very important for reliable operation due to their effect on signal quality.
PROFINET considers both the networking of Ethernet communication and the supply of devices with 24-volt voltage and 400-volt power.
a) Communication (PROFINET data)
PROFINET supports the following topologies for Ethernet communication:
- Line topology, which can be connected to a ring and links the preferential terminals to integrated switches in the field.
- Star topology, which requires a central switch located preferably in the control cabinet.
These two topologies can be combined to form complex tree topologies.
In this case, the PROFINET line topology represents a distinguishing feature since extended lines comparable to PROFIBUS can be realized with PROFINET technologies.
b) Voltage supply 24 V, power 400 V
Line and star topologies are supported for supplying devices with 24 volts. The 24-volt voltage supply and Ethernet communication can also be combined with a hybrid plug connector and cable.
Line and star topologies are also supported for supplying devices with 400-volt power.
By the end of 2008 an audited figures of 1,600,000 PROFINET nodes were installed, a 40% growth over 2007. These are widely spread, with the biggest market penetration being in European, North American and Asian countries.
- WATER EXTRACTION (BELGIUM)
- COGNAC (FRANCE)
- MARINE (NETHERLANDS)
- Production monitoring and material flow tracking system (Poland)
- “Plug and Play” – PROFINET in action at VW Wolfsburg (Germany)
Web link: www.profibus.com ;