A modern industrial application implementation can present a challenging and sometimes daunting mix of requirements. For instance, it is well understood that a typical control system must interface with signals from simple actuators and sensors, yet for many modern applications this is merely the starting point. Advanced control features, device interoperability, network connectivity, and enterprise data integration are all capabilities increasingly demanded in a modern industrial application.
These modern requirements extend far of the traditional discrete-logic-based control of input/output (I/O) signals handled by a PLC (programmable logic controller). Most PLCs are programmed using ladder logic, which has its origins in the wiring diagram used to describe the connections and layout of discrete physical relays and timers in a control system. Applications that expand beyond or diverge from this model become increasingly hard to program in ladder logic. For instance, mathematically complex applications such as proportional-integral-derivative (PID) loops used for temperature control involve floating-point arithmetic. PLCs must often be enhanced with separate—and separately programmed— hardware cards to perform these calculations.
Making a PLC More Like a PC
Using a PLC to meet modern application requirements for device interoperability, network connectivity, and enterprise data integration presents other challenges. These tasks types are usually more suited to the capabilities of a computer (PC). Additional processors, converters or network gateways, “middleware” software running on a separate PC, and special software for enterprise systems must often be integrated into the system to provide these capabilities in a PLC-based application.
Making a PC More Like a PLC
An industrial environments PC packaged can provide many of the capabilities sought in modern applications, particularly those needed for data communication and networking. Similar to augmenting a PLC to accomplish PC-like tasks, however, an industrial PC that requires performing PLC-like tasks, such as process control or machine, also requires expansion. For instance, a PC may be using an operating system that is not optimized for deterministic industrial and high-performance applications. Additional I/O special extensions or expansion cards may need to be integrated into the PC’s operating system to provide the high-performance, deterministic or near-deterministic operation.