Over the years, the market has attempted to reflect the expanded role of the PLC by defining terms such as Open PLC. But, the term “Open PLC” is confusing and in the context of automation has numerous interpretations that tend to dilute its meaning. One issue that creates this confusion is that both new and form factor feature adoption is occurring at different rates in the market. Incorporation of features such as IEC 61131-3 control languages, motion & device networks, and industrial Ethernet connectivity are all being used to define open. Form factors such as Slot PLCs, which are traditional PLCs that run on a PC backplane, or a software only solution (SoftPLC) that runs on a PC are quick to call themselves open.
The value proposition of an Open Control Architecture should equate to a means of providing efficient, cost effective production operations, rather than dwell on the technical nuances of what is open and what is not. PACs clearly address the integration is- sues confronting OEMs and end users by extending the domain expertise of automation systems, resulting in lower lifecycle costs and a lower total cost of ownership (TCO) for manufacturers.
Machine builders and OEMs are seeking smaller and smarter products as the demand for more flexible and modular machines permeates the market. PACs satisfy these requirements with platform independence, PC functionality, and employment of de-facto standards such as OPC and XML for interoperability that allow users to easily exchange data as part of net- worked multi-vendor systems.
A PAC is flexible and configurable enough so users can customize and optimize it to meet their particular needs using components for controlling and automating both machines and plants. All parts of the system are designed to maximize software and hardware integration. There should be one programming and engineering tool for the complete system. This capability involves transparent access for all parameters and functions within the entire system, combining PLC, SoftPLC, remote I/O, motion control, drives, PID control, user guidance, visualization and data handling, along with a maximum integration level to the enterprise though the use of Ethernet TCP/IP, Internet, and IT standards.