Where Is Hardware in the Open Systems Vision

Overview

During the 20th Annual ARC Industry Forum in Orlando, Florida, representatives from ExxonMobil put forth a vision of a more open process control architecture. ExxonMobil depicted this vision as a "system of systems," with an open method of communicating between existing control systems, new control systems, and supervisory systems. The presenters provided little detail beyond that, and that was on purpose.

Suppliers could take a number of different paths to meet the proposed vision.  Nearly all the technologies required exist now.   End users really need to agree on what problems they want to solve and, more importantly, what they are willing to pay for.

The market has proven that if the upgrade to a new system doesn't present appreciable short-term benefits and payoff, the architecture and long-term lifecycle costs won't make a difference.  When a plant is forced to upgrade its obsolete, decades-old control system, will the management invest in an open system, or opt for yet another proprietary system that may be cheaper?

What Are the Goals of the Open Systems Vision?

At the 2016 ARC Industry Forum, ExxonMobil put forth its motivation for seeking an open automation platform.  Its primary motivation is cost. ExxonMobil recognizes that newer systems indeed offer value.  However, it believes the cost of moving its intellectual property (IP) from the existing systems to these newer systems overshadows the potential benefits gained. Therefore, part of the vision is a system that allows IP to be retained, regardless of the hardware.

The company also wants to address the cost of incorporating third-party solutions.  By convincing the industry to adopt a more widely accepted open standard, ExxonMobil argues that integration costs will drop.  This is because the method for exchanging information will be the same regardless of the top-level application and the lower level control.  The idea is to decouple those applications with high IP content from the specifics of the control systems installed.

ExxonMobil also wants to capitalize on mixing and matching best-in-class components from various suppliers, instead of compromising with the features of one supplier's all-inclusive package.

The user community has been asking for these types of capabilities for decades, but perceives little progress.

What about Best-In-Class Hardware?

The announcement says little about hardware beyond its ability to host various functions.  It focuses heavily on integrating control applications and hardware independence. The thinking here is that the intellectual property is difficult to move from one system to another, but so are wires.

Level 2 Control

The DCN (Distributed Control Node) in ExxonMobil's vision is a single-loop controller with universal I/O capability and the ability to communicate on the high-speed deterministic network with peers and supervisory nodes.

The building blocks have existed for decades, with a number of single-loop controllers still on the market. Any of these could be enhanced with the same I/O technology available in the leading DCSs (distributed control systems) to support universality and smart field communications.  Most offer some sort of protocol to allow a remote user to configure and/or view the device information. This protocol could easily be changed.

Many suppliers of hybrid DCSs and PACs (programmable automation controllers) promoted their advantages over single-loop controllers by highlighting the ease of adding supervising logic, redundancy, HMI integration HMI, and ease of engineering and maintenance. But are these differences insurmountable with today's existing technology?  The ExxonMobil proposal harkens back to the days of racks of panel-mounted analog controllers or a 1970s-vintage DCS connected to a central minicomputer with lots of advanced computations coordinating across the unit.

Field Inputs

In most current systems, most I/Os have similar specifications: environmental specs, D/A conversion specs, electrical specs, etc.  Most major DCS manufacturers offer some form of late-binding I/O.  A handful of manufacturers also sell generic I/O that could be used by a multitude of different controllers or even a software-based controller hosted elsewhere. There is not much use of third-party I/O in process control systems, though.  Why? The integrated I/O offers better functionality.  Or does it? Given ExxonMobil's desired architecture, I/O for indication alone or even multivariate control could also be added to the real-time service bus.  With a properly specified standard, I/O from multiple vendors could easily be integrated to meet a given need.

Could the Current Rack-System Approach Work?

Certainly. Racks provide economies afforded by shared infrastructure and may offer advantages for retrofits, which will be far more likely than greenfield installations. Conditioned power from external power supplies reduce heat dissipation requirements from individual units and should increase the overall MTTF of the rack components.  A consolidated network interface to the HMI and supervisory controls ensures the required bandwidth and determinism between rack components.  Because many applications require redundant communication paths, sharing the networking hardware reduces parts and failure modes.

Regardless of the technology used for the real-time bus, a dedicated backplane network will always be capable of faster, more secure communications.  However, for process automation, it may no longer matter because the physics of most processes and field equipment are much slower to respond.

Safety Systems Too?

ARC believes that safety systems would likely continue in their current form, though there is really little technical reason why they couldn't follow suit. However, the market continues to have an aversion to the potential for common-mode failures and call for "black channel" communication for safety-related systems. The configuration tools, however, may converge to reduce training requirements, meeting the needs of a shrinking automation workforce.

Conclusions and Musings

Hardware vendors seeking to meet the needs expressed through the ExxonMobil initiative have plenty of options.  Much of the technology is sitting on the shelves now.  The biggest challenge is finding the "secret sauce," the unique value proposition, in the open systems environment.  In the proposed architecture, there appears to be little value attributed to the frontline controls.  The configurations are envisioned to be easily portable and the communications universal; the epitome of a commodity item.

When we consider today's DCS architectures, the trend is toward consolidation.  Controllers today can accommodate more I/Os than ever.  The DCN concept would actually reverse this trend.  The realities of today's facilities would likely continue the centralized approach where control hardware is located in a room, because the wiring costs are too high and even hardened electronics survive longer under a controlled climate.  Greenfield installations would permit greater distribution.  But distributed I/O can be supported now, yet only makes up a small percentage of the installations.

Several available technologies could open up the architecture further.  Current wireless technologies would allow the service bus to be extended to the field devices themselves, with the DCN functionality hosted in the field device electronics (similar to FOUNDATION fieldbus control in the field).  There is also an initiative that could extend to the service bus via a hardwired network solution to field devices, but it would need to support the current wiring infrastructure to be useful for existing facilities.

Though nearly all the technologies required exist now, there are several paths that vendors could take to meet the vision.   The question that end users really need to answer are: "What problems am I trying to solve?" and "What will I really buy?" The market has proven that if the upgrade to a new system doesn't present appreciable short-term benefits and payoff, the architecture and long-term lifecycle costs won't make a difference in the buying decision.  Will the management invest in an open system that offers potential benefits down the road, or opt for another proprietary system replacement that may be cheaper upfront?

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Keywords: Process Control, ExxonMobil, I/O, DCS, Control Systems, Open Systems, Automation, ARC Advisory Group.