By: Kobus Vermeulen - Direct Sales Executive, Process Automation at Schneider Electric

Process industries today are walking a tightrope of sorts, modernising ageing distributed control systems (DCS) while also embracing edge analytics and cloud connectivity, all without compromising the deterministic, always-on control that keeps plants safe and productive.

Indeed, it’s a challenge shaped as much by operational reality as by technology ambition.

Across brownfield sites, constraints are both physical and practical. For example, legacy I/O and proprietary hardware create compatibility headaches; control logic often embeds decades of undocumented behaviours and outdated networks resist integration with modern, secure architectures. 

Add to above, already-complex challenges, is the need for continuous production, shrinking pools of legacy expertise, and growing cybersecurity pressure.  It’s a mouthful and makes a clear case for why operators hesitate to take the next step.

This is where next‑generation DCSs, such as Schneider Electric’s Foxboro offering, are paving a smoother path, preserving the best of the old while introducing the new in a less disruptive manner.

Preserving the non-negotiables of control

At the heart of modernised DCS like Foxboro is a simple principle: software-defined automation cannot come at the expense of deterministic control.

In high-hazard, continuous-process environments, timing is everything. Here, for example, Foxboro’s scan-based execution model is predictable, bounded and fail-safe and remains ever-present, even as control moves into virtualised and distributed environments. Determinism is what keeps loops stable, even in the face of compute or network variability.

Equally critical is true fault tolerance. Advanced DCS offerings draw on a heritage of parallel, state‑synchronised control, where primary and shadow processors continuously validate each other, thus setting a higher standard than conventional redundancy. 

And in a software‑defined world, this philosophy endures: resilience is engineered into execution, not added as an afterthought.

These principles extend to network design, modular control logic, and secure-by-design architectures. The result is a system that embraces openness through standards such as OPC UA (Open Platform Communications Unified Architecture) and IEC-aligned models, without compromising control integrity.

Re-engineering I/O

Traditional DCS designs lock engineers into early signal types, cabinet layouts and wiring decision making which can be costly to revere when plant realities change. However, Foxboro’s universal, software-configurable I/O fundamentally breaks this constraint.

It allows each channel to be defined in software, analogue, discrete, HART (Highway Addressable Remote Transducer) or otherwise which in turn enable engineering teams standardise cabinet designs early, without committing to final configurations. 

This dramatically reduces complexity, enabling pre-built, repeatable intelligent enclosures with fewer cabinets, less marshalling and significantly reduced wiring.

The impact on project execution is fundamental and profound. Late-stage changes which is historically a source of cost overruns and delays become software adjustments rather than physical rework. Furthermore, instrument changes, vendor substitutions or scope shifts no longer trigger redesign cycles or procurement bottlenecks.

In practice, risk moves out of the physical domain and into software, where it is faster, safer and far less expensive to manage.

Building the software-defined stack

Looking closer at Foxboro’s evolution into an edge-ready, software-defined architecture, it is clear that it was not one single leap but a layered metamorphosis:

• Virtualised backbone - servers decouple DCS apps from hardware, running HMI, historian, engineering, and alarms as resilient, scalable virtual machines.
• Lifecycle friction reduced - updates are now image‑based, not hardware‑bound, streamlining maintenance and upgrades.
• Thin and zero clients at the front line. Operator access has been simplified, tools run centrally and delivered securely to lightweight endpoints.
• Cybersecurity strengthened and overhead is cut – there are no more complex workstation upkeep; centralisation now reduces risk and cost.
• Edge I/O brings intelligence closer - software‑defined modules shrink cabling, add diagnostics, and enable local processing.

A pragmatic path forward

For brownfield sites, transformation is necessarily incremental. Here it is important to forgo the forklift approach, focusing on phases that are strategic and actionable.

It begins with stabilisation, refreshing infrastructure, aligning lifecycle dependencies and ensuring systems remain current and continuous. From there, Edge I/O and universal I/O can be introduced alongside existing systems, reducing complexity without disrupting operations.

The next step is coexistence: piloting software-defined automation and edge applications in low-risk areas, while integrating with the existing DCS through secure, non-intrusive interfaces. 

Ultimately, modern DCS preserve the non-negotiables of deterministic control, fault tolerance and high availability, while introducing flexibility through software, virtualisation and edge technologies. Only then does the control layer itself evolve gradually, and in line with natural lifecycle event, towards fully software-defined execution.