Plant Construction & Process Technology

ARC Advisory Group’s Vision Of Evolution

From DCS to a Collaborative Process Automation System

15.03.2011 -

Conceptual Model - A Vision of Collaborative Process Automation System (CPAS) is the ARC Advisory Group's vision of how process automation systems should evolve through the next decade. CPAS does not describe any particular commercially available system, but rather it presents a conceptual model as a vision. While the technologies associated with CPAS are available and proven, not all are currently available within any single offering. In this first part of the two-part series, ARC's Director of European Research David Humphrey looks at the evolution and history of process automation systems.

CPAS is an application-enabling environment for process control, advanced process control, and operations management applications that also includes human empowerment applications such as decision support and advanced analytics. CPAS spans from sensors and actuators to ERP interfaces. To minimize confusion, CPAS does not recognize software such as MES or HMI SCADA as subsystems, but rather addresses these as classes of applications. Within the constraints of the IEC 61131-3 programming and configuration standard, CPAS incorporates a single model with distributed processing and shared services. It is data-driven, all-digital and based on international standards. CPAS systems are inherently robust, deliver high accuracy with low total cost of ownership (TCO), and support a high level of collaboration. The CPAS concept is the product of several decades of technological process automation evolution, each with its specific characteristics and focus.

The Computer Integrated Manufacturing Decade

The CPAS vision began with the introduction of computer-integrated manufacturing (CIM) in the 1960s and 1970s. CIM was ahead of its time and largely an academic exercise because the necessary supporting computer and network technology was not yet in place. Focused on supervisory applications, its primary value was to validate what was possible and set the stage for future developments. The Purdue Operations Model, model-based predictive control, and optimization came out of the CIM era.

The System (DCS) Centric Decade

The 1970s brought us the microprocessor and distributed process automation in the form of the first distributed control systems (DCS). These marked the transition from analog technology to the greater precision of digital technology and used IEEE 802.4 token passing communication because of its determinism. These systems were essentially proprietary in nature with closed communications.

The Network-Centric Open Systems Decade

The next decade (mid 1980s through mid 1990s) began to address the proprietary nature of systems and brought us the "network-centric open system," with much of the associated technology developed by the U.S. Department of Defense (DOD). The DOD developed the first open standards-based operating system, Unix, and more importantly, a truly state-of-the-art standards-based networking technology, IEE 802.3 Ethernet TCP/IP.

Rather than using token passing, Ethernet uses collision algorithms (CSMA/CD). This networking technology enabled client-server computing, the internet and, ultimately, CPAS with global data access. Most process automation system suppliers were late to embrace Ethernet because they believed it was not deterministic enough - which later proved not to be the case. Object
management (not to be confused with object programming) describes the ability to organize related data or information into a common structure, perform higher-level operations on it, and interact with it as a defined entity.

This decade also saw the introduction of the first commercially available process data historians. Since most process control systems at the time had not yet embraced Ethernet, most systems became historian-centric with respect to data access for supervisory applications. Ultimately, Ethernet TCP/IP became ubiquitous as the state-of-the-art networking infrastructure for process automation and enterprise systems.

The Application-Centric Decade

A common foundation for networking made it possible to incorporate process control and information into the same application environment, making possible the application-centric decade (mid 1980s to mid 1990s). It also heralded the Windows environment as the presentation vehicle of choice. This marked the point in the evolution of process automation technology where the focus shifts from the underlying technology to application-enabling technology. Many major advances were built on internet technology, most significantly Ethernet and TCP/IP, which enabled the CPAS concept of the "Common Information Infrastructure." In essence, this collapsed the traditional DCS architecture onto a common network backbone by allowing the process control and supervisory applications to interact in automation configurations in exactly the same way that Internet applications interact. It also provided a vehicle to integrate standards-based fieldbus technology into the same infrastructure and to exchange data using the same mechanisms.

Object management (not to be confused with object programming) is a major beneficiary of this technology. It describes the ability to organize related data or information into a common structure, perform higher-level operations on it, and interact with it as a defined entity. Examples of object management are the grouping of objects associated with a unit operation and performing global functions like alarm suppression with a single action, or creating inheritance or association between different objects. Object management is an important capability when the process to be controlled is functionally decomposed for advanced functions.

Up until the application-centric decade, there were an unlimited number of approaches for describing, designing, interfacing and programming applications. This decade delivered the ISA88 common reference model for structuring process control applications, which is applicable to continuous, batch, and discrete process control. It also brought us the ISA95 reference model for operations management applications. Finally, it brought us IEC 61131-3; an international standard that organizes and prescribes the most commonly used process control languages and configuration.

Maintenance is the second largest controllable cost in a typical process plant. In the application-centric decade, predictive maintenance, which is about one-tenth the cost of routine maintenance, drove the need for plant asset management (PAM) applications. Most process automation systems incorporate PAM extensions, but with varying success. PAM began as a maintenance facility for automation field devices, but now reaches into automation assets themselves as well as into the plant production assets that automation controls.
With the introduction of information technology into process control systems, it was inevitable that Windows, the operator interface of choice, would soon follow. Object Linking and Embedding for Process Control (OPC) technology also gave us a basis for interfacing Microsoft-based applications with both organized and disparate data and information. Traditional OPC is a de facto standard communication protocol for non-mission-critical applications. OPC-UA (Universal Architecture) promises to be more robust and deterministic.

The Business-Centric Decade

The previous four decades were a precursor for the current business-centric decade because at this point, the focus is continuing to evolve from the underlying and application-enabling technologies to actually improving business performance. The business-centric decade introduces some significant capabilities. These include identifying potential incidents in time to avoid them, operating on an exception basis, automating operations management work processes to support a knowledge management workforce, operating proactively based on predictive modeling, and finally, unifying business and manufacturing work processes.

The Emergence of CPAS

When the benefits of utilizing information technologies in process plants became obvious, the major process automation companies brought new systems to market, marking the evolution to the next generation of automation systems. Each system differed based on how a specific supplier viewed the problems to be solved and its perceived solutions to those problems.

This led to a period of confusion for users, with several major operating companies retaining the ARC Advisory Group to draft the vision for a system that supported process control, advanced process control, and operations management applications, complemented by human empowerment applications such as decision support and advanced analytics. This vision needed to include general guiding principles, while also providing enough detail to allow in-depth internal discussions as well as productive problem-solution discussions with external suppliers. This effort resulted in the Collaborative Process Automation System, or CPAS.

Part two of this series, which will cover the CPAS vision and guiding principles, will be published on April 14. 


ARC Advisory Group GmbH & Co KG

Stadttor 1
40219 Düsseldorf

+49 2104 542 012