For more than six decades, programmable logic controllers, or PLCs, have been the backbone of industrial automation. Introduced in the 1960s to replace hard-wired relay logic, PLCs work as industrial-grade computers designed to monitor inputs, execute deterministic control logic, and drive outputs that control physical equipment.
Despite huge advances in processing power, form factor, and connectivity, the core function of the PLC has remained largely unchanged. A PLC reads signals from sensors and devices on the plant floor, evaluates those signals against its programmed logic, and updates outputs to actuators, drives, valves, and other equipment. PLCs range from compact units small enough to fit in a pocket to large, rack-mounted systems designed for complex, mission-critical processes.
And, over time, most industrial sites have accumulated a mix of PLC types, vendors, and generations.
This state of affairs, says Dave Sutton, Product Marketing Manager for Industrial Automation at Schneider Electric, brings a set of problems for plant owners. While each controller may reliably do its job, this diversity introduces a significant engineering burden. Each PLC is programmed individually, data sharing between controllers must be explicitly engineered, and network communication requires careful configuration and maintenance. As plants grow in complexity, this overhead increases rapidly.
The challenge is not limited to PLCs alone. Human Machine Interfaces (HMI) and Supervisory Control and Data Acquisition (SCADA) systems provide operators with visibility, control, and visualisation of industrial processes, replacing physical panels of switches and dials. But these systems are often developed separately, and integrating them with multiple PLCs, energy systems, and analytics platforms is complex and costly. The result is frequently siloed data and limited operational insight.
“From a design point of view, we can see all these problems stacking up and we’re asking how we can address some of these challenges in this first design phase,” Sutton says, speaking at a press briefing at the Schneider London HQ.
The answer, according to Schneider Electric, is to set up an industrial automation system based, not on the hardware the plant uses, but rather on a software layer which connects everything in the plant and from which various bits of hardware can be connected. For example, a single pump model can be instantiated across a plant for 100 identical pumps. This reuse ensures consistency, reduces engineering effort, and maintains digital continuity — data flows seamlessly from the PLC execution layer through HMI, SCADA, and analytics systems. PLCs are no longer isolated islands of logic but distributed execution nodes within a unified software architecture.
This approach has become known as open software defined automation.
“Instead of starting with hardware, engineers begin by modelling the plant itself,” says Karishma Guddu, Solution Consultant for Software Designed Automation at Schneider. “Assets such as pumps, treatment units, or production lines are defined in a hardware-independent software layer. Only once the application is designed does hardware selection come into play.”
This layer contains the control logic, data models, alarms, HMI hooks, and operational context for each asset. AI-assisted engineering tools help teams collaborate efficiently, apply best practices, and accelerate design. Because the software is decoupled, assets can be deployed to any compatible execution platform — traditional PLCs, smart drives with embedded controllers, industrial PCs, or virtual controllers in data centres. The same logic can be deployed without modification, regardless of vendor.
Schneider Electric says its aim is that open software defined automation should be able to make it as simple for industrial operators to upgrade infrastructure as upgrading a laptop.
Neil Smith, Segment President for Consumer Packaged Goods at Schneider Electric, draws an analogy with digital transformation in the music industry: from vinyl to CDs to streaming, users can access the same music across platforms without learning new devices. Similarly, open SDA decouples applications from specific hardware, allowing flexible deployment across PLCs, drives, or virtual controllers. “You don’t have to have a specific hardware device,” Smith explains. “You take the application first… then decide what hardware to deploy it on.”
Smith highlights that modern manufacturing demands agility. A dairy plant, for example, may produce dozens of milk variants — low-fat, plant-based, flavoured — on the same line. Open SDA supports this by allowing engineers to design asset models once and deploy them across multiple SKUs without reprogramming hardware.
