Control through the ages

16 August 2022

Eamonn Garry discusses how controllers have developed, since the introduction of the first PLC, and looks into their future role in modern and future automation systems.

Today’s controllers have very different capabilities to those of their ancestors, and our relationship with them has also transformed. Being at the core of every industrial automation application today, it is only natural for controllers to have evolved to address the needs of their users as well as current industry trends, such as the Industrial Internet of Things (IIoT). More specifically, PLCs are now designed to support data-driven applications by offering a number of key functions. 

One of the most obvious examples is the advances in processing power of PLCs as the requirement for faster cycle times has become a common denominator of competitive companies. Only 20-30 years ago, systems that required high-speed control typically used PC-based controllers. Today, PLCs are so powerful that they are able to offer the same level of performance. 

As the need to store more data, information and programs for data-oriented applications is increasing, PLC memory has also been growing exponentially. It is now easier to offer gigabytes within a product – a capability that has revolutionised programming activities. 

it was essential to minimise memory requirements, coding practices such as pointers and indirect addressing served as key strategies. While these addressed the main issue, they also made maintenance activities challenging. As more memory became available, programming activities changed to favour ease of maintenance, discouraging indirect addressing and including more comments. 

Besides, early PLCs were designed to replace complex relay-logic and timer-based circuitry. The ladder logic programming format was developed to enable technicians to program the system without specialist high level coding expertise. Further programming approaches were then introduced including standardising under IEC 61131 which defines two text-based languages and three graphical configuration formats. 

Additionally, programmers can now take advantage of libraries containing pre-defined code blocks, which can further simplify interactions, reducing the time and cost associated with automation projects. 

Maximum control 
The onward progression of PLC technology has proceeded alongside developments in related industrial automation solutions – in particular, robotics, motion control and vision systems. As the technology has evolved, it has become easier and less costly to integrate modern PLCs with these technologies, for example monitoring and controlling processes via SCADA and HMIs.

Although many PLCs still retain legacy communications interfaces, such as RS-232 and RS-422/485, to enable connectivity with older devices, Ethernet has become the standard for most applications. Moreover, given that data sharing is fundamental for future-oriented, smart manufacturing, modern control systems now use standardised, technology-agnostic communications protocols for more integrated communications between PLCs, HMIs and SCADA. Along the same lines, there is now greater alignment in data management and collection to higher level systems, via standardised solutions such as OPC UA (Unified Architecture) with more detailed diagnostics to support data gathering and analytics. Many process operators and manufacturing companies now integrate their PLCs through OPC UA to ERP, PAT and MES systems.

Also, the use of authentication certificates is supporting improved cybersecurity in increasingly interconnected setups. 

Finally, digitalisation is influencing the way operators interact, learn and troubleshoot their devices. In the past, the only place where it was possible to find answers was via technical documentation. Now, virtual wizard tools, online courses and remote training from automation vendors and system integrators help users increase the effectiveness of their operations. 

Eamonn Garry is operations director at Optimal Industrial Automation.

Contact Details and Archive...

Print this page | E-mail this page