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Flexibility by design
Combining PLC, PC, and software-based control elements with networking technology provides flexible, cost-effective automation
By John Lewis, Northeast Technical Editor -- Design News, May 6, 2002
Newton, MA — Engineers are changing the way they design manufacturing systems by turning to advances in computing technology to succeed in today's make-to-order instead of make-to-stock business environment. Automation systems have to be fast, flexible and cost-effective, according to Ashok Nanjia, senior staff engineer at 3M. "Some of the manufacturing-specific requirements that we are facing today include more rapid auto-processing, and faster changeovers to handle rapid changes of product mix and volume," Nanja explains.
Though overall factory automation system architectures have hardly changed since the invention of the PLC, the technology for information management and control systems has rapidly evolved thanks to the declining cost of computing power, increased power of PCs, improvements in networking, open systems and standards, server technology, database systems, and object oriented programming.
"All of these technologies are coming our way to help us build fast and flexible factories," says Nanjia. "For 3M, the use of open standards and technologies such as Ethernet, OPC drivers, Web-enabled applications, or Active X controls is key."
Daniel Parish, director of engineering with systems integration firm Tegron (Longview, TX) has different issues. Parish envisions a real software-driven, object-oriented world, where it doesn't matter whether he's working with a PLC, inside of an NT environment, or with any other type of software execution model. "The height of flexibility would be applying software modules or objects that work across different platforms. We're not just controlling machines anymore. We're not just replacing relay-based controls with a PLC. Now we need integrated architectures that let us aggregate and pass data around."
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| By reducing the the cost of the hardware required; easing the task of configuring equipment; and simplifying programming and equipment interfacing open control systems promise cost-effective solutions to a host of industrial challenges. |
These needs are driving growth in PC-based controls and OCS (Open Control Software), according to the latest "Open Control Software Worldwide Outlook" study from ARC Advisory Group (Dedham, MA). According to the study, the total PC-based OCS business, including soft logic and motion control, was about $70 million in 2001. Though just a small slice of the overall automation-market pie, the study projects this fast growing segment will increase at a compounded annual growth rate of greater than 24% through 2006, growing to approximately $200 million. The ARC data indicates that GMC (General Motion Control) will catch or surpass SoftLogic by 2006.
Two main drivers for this trend are the proliferation of PC technology on the factory floor and cost savings. "Though PLCs still drive the majority of information gathering on today's factory floors," explains Dick Slansky, ARC research director, "you aren't going to really move data around with PLCs, you're going to have to do it on a PC-based architecture."
However, PLCs, the heart of most automation systems today, will remain in the mix. "It's not going to be a rip-and-replace mentality," Slansky explains. "That is, engineers aren't going to just go in and rip out all their PLCs and convert everything to PC-based controls. Instead, it will be a case-by-case business decision for each automation line. As a result, manufacturers will rely on more hybrid automation systems combining PLCs, PCs, networks, and software control."
In fact, diverse international and de facto standards such as Ethernet, OPC, STEP, Fieldbus and others are evolving to make it easier to connect systems, applications, field devices, hardware, and software components.
The Simatic WinAC MP, from Siemens Automation and Drives, for example, is a soft PLC that performs control and visualization tasks on a Windows CE platform. Because it can run on the Simatic MP 370 multifunctional platform, it's particularly suitable for tasks involving large volumes of data.
"WinAC-MP represents an IEC 6-1133-3 logic control (PLC) function in a pure software form," Slansky explains. "With it, Siemens offers another tool for the automation user who needs a PC-based soft solution that exploits the hard real-time capabilities of Windows CE, while offering the flexibility of PC-based architecture." Such platforms meet today's communications, data managing, and interoperability requirements for a collaborative manufacturing environment, according to Slansky. Additionally, users want to be able to run HMI applications and control logic on the same box in order to reduce automation infrastructure and reduce costs.
For more information about WinAC-MP from Siemens: Enter 533
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