The PLC has moved well beyond its original discrete control function to become a multi-discipline platform for plant-wide automation. Mogan Swamy reports.
Customers increasingly need to make good business decisions based on information obtained from the plant floor. But the devices or methods used to enable this must be at an optimal cost, with the minimum ofdisruption in its execution or implementation.
Interestingly, these were the exact driving forces that gave birth to the programmable logic controller (PLC): it was envisioned as a controller to replace troublesome relay panels, to replace costly minicomputers and reduce programming time for various machine tool applications. In its conception, overall, it provided a simpler interface betweencomputers and machines at a relatively low cost.The concepts upon which the PLC’s development was based, has not diminished, but has been further heightened with a need to define a vision for the factory of the future. This demands the provision of an architectural roadmap, based on hardware and software. Conceptually, the PLC design should depend on prevailing business drivers and emerging technologies and all evidence suggests that the PLC has been up to the task, without slacking on the goalsfor which it was originally envisioned.
In this sense, the PLC continues to play an important role in integrated automation. Theintegration of a PLC into the factory floor makes it not just a single controller, but an extension of thewhole enterprise computer system.
In the current context, it would most likely to be part of the technology mix in more collaborative discrete control systems, designed and built for a distributed manufacturing process and supply chain, but sensitive to a demand-driven market, and the need for real-time collaboration and response acrossthe manufacturing enterprise.
The fact is the PLC has become the workhorse of factory automation. Other technologies such as CNC, motor drives, motion control, robotics, automatic ID systems, and vision systems are now factoryfunctional because they are hitched to a PLC system. This implies that information from all these other domains are the engine that runs the production line, with the PLC taking an event-driven approach that allows for optimization of the production processes,by providing access to real-time events.Event-driven information, potentially, can be the cornerstone of an effective production-to-business strategy. As this information is captured, as it occurs, it can be moved to enhance production management, improve manufacturing process visibility and streamline supply chain applications. But this can only be effective if the information is shared across theproduct lifecycle and the manufacturing enterprise.
The trend towards a unified and flattened, tiered, and a hierarchical discrete manufacturing environment, has helped the PLC define its own relationship between the different domains in the manufacturing environment, and move towards aproduction-to-business based architecture.This has resulted in PLC trends towards increased communication capability, smaller sizes, better software and implementation tools, and diagnostics. In addition, these developments have tried to address customer demands for open standards, multi-control disciplines, modular architecture, and comprehensiveautomation solutions software.