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Industrial Ethernet Book Issue 76 / 17
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Web-based plant operation using PC-based automation

PC controllers and high-speed EtherCAT networking energize control and process engineering. A highperformance 30,000A power supply unit sets new performance and energy efficiency standards for welding plants in metal working applications and for microwave equipment in the semiconductor industry.


Overview of the system hardware architecture

Through optical bypasses, fiber switch technology increases the tolerance of fiber optic networks regarding both single and multi-point failures and limits the effects of a brownout or complete system outage.

Aixcon PowerSystems is a specialist in control technology for power electronics and manufactures complete systems used, for example, to produce longitudinal seam welding of composite pipes.

Using high-speed Ethernet networking to integrate all automation components including I/Os, PLCs and servo drives into a system-wide fieldbus, the entire operation of the plant is web-based. The result is an operating concept that is totally platform independent and can optionally be run via a Windows PC, Linux, Apple, iPad or iPhone.

Heating of titanium sections

A recent project to develop and produce a power supply system for a °hot stretcher" highlights the challenges of developing these systems. A hot stretcher is a type of plant in which titanium sections are machined and formed under the influence of heat without impairing their material characteristics.

Sections are fixed in the hot stretcher, heated based on an exactly defined temperature curve, formed (turned and drawn) and then cooled. The specifications must be followed precisely to prevent degrading the properties of titanium such as its strength, thickness and ductility.

Electricity is used for heating the material in a hot stretcher based on defined temperature profiles. To heat a titanium section with a length of around 4 m and a cross-section of around 50 cm2 to 620°C in 60 seconds requires an electrical current of around 17,320 A. Aixcon's task was to develop and produce such a powerful current source. The dimensions of this 'power supply unit' are impressive. Three control cabinet panels are capable of delivering an impressive total of 30,000 A. Each panel has 10 power units, each with its own controller and rectifier for three power transistors with 333 A each. The system uses a 480 V/400 A 3-phase power supply.


Three control cabinet panels are capable of delivering a total of 30,000 A for the hot stretcher.

Automation and control concept

The specifications required to efficiently automate and operate this plant included development, parameterization and archiving of the recipes (current curves) in a database, archiving of the actual process data (quality verification) and set value generation for the current source controllers.

Using an Ethernet-based machine network as the basis for communications, the system required real-time transfer of the set values from the PLC to the controllers, and fast online visualization of the process. One additional goal was platform-independent visualization of the process and production data using both the iPad and iPhone.

These requirements were solved and implemented with an innovative automation and operating concept, based on implementing a database server, a TwinCAT PLC on a C6920 Industrial PC plus EtherCAT and EtherCAT I/O terminals which are used to transfer the set values and remaining process data. A Panel PC with CP-Link 3 is utilized for visualizing online process information at the machine, drawing information over the network from both the database server and PLC server. All of the web-based, platform-independent visualization was created using Java Script.


Plant operations are completely web-based and can be run via a Windows PC, Linux, Apple, iPad or iPhone.

PC control and visualization

A PLC generates the set values for the process based on the recipes stored on the database server. The EtherCAT machine control network is used for transferring the values to the Aixcon controller boards and for logging the signals, temperatures and states that are relevant for system control and monitoring.

Each panel has an EtherCAT I/O station. Online visualization of the whole process takes place directly at the plant via a CP-Link 3 client. This technology replaces the previous image transfer that used DVI with an interference- free, simple to install and cost-effective Ethernet cable. The ability to use the Ethernet interface offers several optional features including, for example, connecting with up to nine clients with different resolutions, display sizes and content. At the hot stretcher end of the process line, the CP-Link 3 technology is used; at the other end of the large machine, an additional panel can be positioned for special diagnostic purposes.

The recipes for current and temperature curves, section types, etc. are managed on the database server. The database server also deals with archiving and processing of relevant process and production data. The database and PLC form the centerpiece of the process control system. Like the visualization, this communication is also based on Java Script. The components required for this purpose are the respective web servers and the script DLLs. For the PLC, these are Internet Information Server (IIS) integrated in Windows and the ADS script DLLs for accessing the PLC variables.

The main operator panel is a Windowsenabled Panel PC that is installed directly at the plant. Since all modern browsers support Java, that means that no further software is required and the browser integrated in the operating system can be used as a framework for visualization. The operator terminal is connected directly with the PLC via CP-Link 3, and Ethernet is mainly used for fast online visualization of process data. In addition, authorized operators have access to the database and the recipes. Quality-relevant data can be archived and the diagnostic data can be accessed via the database server.

Mobile devices such as iPads, iPhones or remote client PCs are routed via the Internet through VPN. They can access the web server of the database computer directly via Java Script for displaying the required data. In the same way as the system control can access the database, the reverse route is also available. For example, the production manager can not only view the production data stored in the database, it is also possible to visualize current process values such as currents, temperatures or diagnostic plant data on an iPad.

Increased efficiency results

"The current source we developed sets new standards in terms of performance, controllability and energy efficiency," said Aixcon's managing director Karl Swiontek. "For example, the single-phase AC power source used in the past was only around 60% efficient. We were able to increase efficiency to an impressive 98%. This is not only better for the environment, it also offers real savings potential."

Ralf Stachelhaus is Manager of Beckhoff Automation's Rhine-Ruhr branch in Germany.

www.beckhoff.com


Source: Industrial Ethernet Book Issue 76 / 17
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