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(English) Controls Evolution for Automationagosto 31, 2016
In the 1960s, the Programmable Logic Controller (PLC) was developed as a device to replace relay logic in industrial machines and assembly processes. While some of this technology still exists today, much of it has been replaced in an effort to reduce energy consumption, complex wiring diagrams, troubleshooting efforts and especially space requirements. This led to a shift in knowledge base and tool requirements that ultimately resulted in logic changes requiring extensive planning, engineering, and wiring changes, all of which were expensive, error prone and lacking in standards as it provided opportunity for freedom of methodology and format depending on the programmer. It did however, enable faster logic changes and less labor associated with hard wiring a cabinet full of relays. The PLCs were programmed using Ladder Logic, which consisted of symbols that looked like relay contacts, coils, and timers. Eventually far more complex tools were developed to do sophisticated math functions and comparisons. By organizing these symbols in ladder rungs, the engineer would create a control logic sequence. This method of control greatly simplified the process and effort for engineers and technicians because they understood how to design control systems with these components.
In the 1970s, Distributed Control Systems (DCS) were developed for process control applications, meaning, control devices were distributed throughout the systems using microprocessor technology. At the same time, Direct Digital Control emerged for process loop control using computers or microprocessors rather than pneumatic or electronic analog controllers. As with most new technology, each manufacturer/developer wanted to protect their IP and try to protect their market share thus leading to proprietary, or closed protocols.
Then in the late 1970s, standard open network communication protocols were established for industrial communications. Modbus was the first and remains a common protocol for many Original Equipment Manufacturer (OEM) companies. Control systems then evolved to provide coordinated control through networking of control processors. Until the establishment of the IEC 61131-3 standard, which was first published in December 1993 each vendor had their own proprietary programming methods and network protocols. This made it difficult for end users to make decisions on capital equipment purchases due the incompatibility of the network protocols. In the last 20 years, Ethernet has become the industrial network backbone for open industrial protocols. Generally, DCSs use Ethernet hardware and communication devices, but they still have proprietary control network protocols.
Today we at CAID utilize PLC’s with open network communications via Ethernet to control our complex solutions and provide our customers with the highest level of quality, flexibility and success.