However, vast differences exist between the relatively benign environment of the office and the plant, which includes dirt, electrical noise, power surges and explosive conditions.
To bridge these two environments, yet still provide consistent communications from field level to top level, Profibus International (www.profibus.com) has developed the Profinet standard for industrial Ethernet. Current products include Profinet-based controllers and proxies, which connect existing Profibus networks to Profinet. In early 2004, Siemens (www.siemens.com) plans to introduce Profinet field-level devices for distributed input/output (I/O) over Ethernet.
Work on a Profibus fieldbus standard for robust industrial networking began in Germany during the late 1980s with Profibus FMS (Fieldbus Message Specification). In 1993, the specification was configured as the faster Profibus DP (Decentralized Protocol), which is designed for high data transfer rates in automation systems with distributed I/O and field devices. Additional developments include Profibus PA for process automation, introduced in 1995, the Profidrive profile for motion control applications and the Profisafe profile for safety-related applications, both released in 2001. Profibus is a communications protocol as well as the physical means to connect and power remote field devices to controllers.
“Profibus can now be used in everything from micro-automation solutions to large process automation applications,” says Karsten Reese, Siemens product marketing manager for industrial networks. There are over 2,200 different Profibus products currently available from over 300 suppliers, and more than seven million Profibus nodes installed worldwide in about 750,000 applications, according to Profibus International.
Today, a typical discrete manufacturing application consists of drives, I/O devices, controllers and operator interfaces, all connected via a Profibus network that provides communications of up to 12 Mbaud with cycle times of 1-8 msec. The introduction of Profinet as a separate yet compatible protocol, will up transmission speed to 100 Mbaud with a high data throughput and cycle times up to 5 msec.
“The real advantage of Profinet comes in the next generation, with the scheduled 2004 release of field-level Profinet devices,” predicts Filomena Wardzel, Siemens Automation Solutions Business Manager. “We’ve taken industrial Ethernet to the next step by putting distributed intelligence down at the device level.” This forthcoming line of products will use Component-based Automation, with the Profinet kernel embedded in the device hardware. “Instead of having to program communications [for each device], users can configure and reuse the configuration in multiple places. It’s a ‘configure once, use many’ model,” Wardzell explains. “This is where Profinet adds significant value by providing the vertical integration needed to get data out of the device and into the MES [manufacturing execution systems].”
Profinet was developed using standard information technology protocols, such as TCP/IP, Microsoft Common Object Model (COM), Distributed COM (DCOM), Active-X and XML. For the end-user, this reduces engineering time and makes data more available for real-time decisions, Wardzell says.
Another advantage of Profinet, according to Reese, is the ability to use proxies to connect Profibus and other fieldbus networks to Ethernet. In this instance, the proxy acts as a translator. Explains Wardzel, “Something that speaks, for example, DeviceNet, comes through the proxy, and on the way out, it speaks Profinet.”
Five years out
Wardzel projects Profibus and Profinet will coexist and compliment each other for many years. “It will be a while before Ethernet is certified for industrial environments, such as those requiring intrinsic safety. Profibus will continue to serve those application areas, and others where it has strong benefits and an installed base. The automation world is not as cut-and-dried as the office world. While you can take a personal computer, plug it in anywhere and make it work, the same is not true for automation components.”
Profinet technology has had some early application success in the automotive, material handling and packaging markets. Future applications will leverage Profibus installations from factory automation through process control.
