Industrial Ethernet
The evolution of control system connectivity SOURCE: CONTEMPORARY CONTROLS
Take a moment to reflect on where we’ve come from to better understand the connectivity technologies that will help you achieve your goals. Beyond the point when we have connected everything to everything, which technologies will win the day? Thriving organizations are the ones who are paying attention to history. SINCE THE ADVENT OF ELECTRONIC PROCESS control systems, many new technologies have made their way into the industry. Now, we are in the early years of another revolution that is bringing its own innovations and design philosophies. Taking a moment to reflect on where we’ve come from can help us better understand where we are going and which technologies will help us achieve our goals.
Early automation control and communication systems
When the first I/O systems were developed, the standard for control and sensing from the field relied on electromagnetic and pneumatic components, which were subject to physical degradation that limited their lifespan. In the 1960s, engineers generally organized relays into ladders of switching logic that directed electrical flows in a deterministic pattern. These relay configurations were inflexible and guaranteed to fail after a finite time, leading to the development of solid-state components that operated much more reliably. Eventually, the same technology was applied to create compact signal sensing inputs, yielding the components needed for a complete digital input/output system. The first PLCs were built using these early I/O components and began making a splash in the automotive industry in the early 1970s. Around the same time, companies like DEC and Intel were bringing the microprocessor into the mainstream, and their users demanded options for integrating I/O into those systems as well. These high-tech computing systems required further developments in early I/O systems, which offered too little protection for sensitive computer electronics. The first generation of optically isolated digital I/O plug-in module racks quickly became the world standard form factor for computer-based control, allowing automated control to reach many more industries well into the ‘80s. These parallel bus systems were very fast for the time but suffered from a lack of noise immunity, leading to the first serially addressable I/O. The change yielded greater protection and extended cable lengths but came with a reduction in speed, which in some cases necessitated fundamental changes in the communication architecture. Processorintensive I/O tasks like counting and latching 04.202 2
Today’s edge controllers and I/O systems bridge the OT/IT gap by combining traditional real-time control and sensing functions with communication, storage, security, and data processing functions previously found only in higher-level systems. (pictured: Opto 22’s groov EPIC edge controller, 2019) were embedded in the I/O module to preserve the responsiveness of the system; core communication functions were located in a dedicated co-processor. Distributed control through so-called intelligent I/O allowed control systems to manage many more I/O points without impacting the performance of the central controller. As I/O modules and I/O processors improved, these early computer-based control solutions were able to offer analog signal processing options, something found only in large distributed control systems (DCSs) at that time. Since early ladder logic—used by PLCs as a programming language—wasn’t designed to handle analog data formats, this also led to the development of new programming languages. These early developments exemplify a pattern that has repeated over the past several decades and yielded successively more compact and integrated devices. Later generations of control platforms offered greater computing power “per square inch” as advanced math, programming, and communication functions were incorporated into control boards. Newer generations also continued to combine and
i n d u str i a l e th e r n e t b o o k
embed I/O processing circuitry in different ways. Individual modules expanded from a single I/O channel to upwards of 32 channels, and, in the case of universal I/O today, can even accept a variety of different signal types on a single physical channel. These technologies have also become available in low-level devices such as I/O modules, sensors and transmitters, and networking components, allowing for the creation of flexible, resilient distributed architectures.
The information revolution
Another pattern apparent from the early generations of control systems is the influence of information technologies on the industry. Even the PLC, marketed as an alternative to early general-purpose computers that were seen as unreliable and difficult to program, wouldn’t have existed without the development of computing technology. And in the 1980s and 90s, as low-cost IBM-PC alternatives began to flood the market, innovations from outside the industrial control market continued to have an influence. PCs were still the primary control option for
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