The Profibus User Organization presented Profinet in 2000 as its solution for industrial automation based on Industrial Ethernet. Since 2003 Profinet is integrated in the IEC 61158. Profinet is based on Ethernet-TCP/IP and uses established IT standards. It includes Real-Time Ethernet capabilities for the requirements of fast data transmission.
In the Profinet concept two different types are distinguished: - Profinet CBA (Component Based Automation) is effective in distributed automation plants; it is ideal for intelligent field devices and automation devices with programmable functionality.
- Profinet IO (Input/Output) integrates distributed field devices by a central control system in factory automation.
Profinet uses Ethernet at three different performance levels for communication purposes:- TCP/IP for Profinet CBA transfers (non-time critical data for plant set-up with response time under 100 ms);
- SRT (Soft Real Time) for transmission of time-critical process data within the production plant at a clock rate of up to 10 ms;
- IRT (Isochronous Real Time) for time synchronized application especially for motion control applications, which allows a clock rate of 1 ms.
Profinet IO: Profinet IO allows direct interfacing of decentralized field devices on the Ethernet. This supports flat communication hierarchies in automation. All the devices used are connected in a consistent network structure and therefore provide open communication throughout the entire production system. The signals from the field devices (decentralized peripherals) are processed directly in the assigned controller. Configuration is performed via a device description file (GSD), which already proved successful in Profibus DP. Integration of the decentralized field devices is an optimal add-on to distributed automation. A combination of the two can be implemented in a Profinet network at any time.
The established field bus systems (e. g. Profibus, Interbus, CAN) will remain in future plants on the field device level. They guarantee the protection of existing investments and can be constructed at very reasonable prices.
Communication between the control and device level is realized by interface modules. Profinet offers two methods of integrating fieldbus systems: - Integration of fieldbus devices via so-called proxies. In this case the proxy represents the lower-level field devices on the Ethernet. Using the proxy concept, Profinet offers a fully transparent transition from existing to newly installed devices.
- Integration of complete fieldbus applications via a gateway-module. A fieldbus segment represents a self-contained component. The representative of this component is the Profinet device, which at a lower level operates a fieldbus. The complete functionality of a lower-level fieldbus is transmitted by the gateway.
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