PLC hardware speed, I/O, communications, redundancy, Part 4: PLC technology advances

In a November 9 webcast, “PLC series: PLC hardware speed, I/O, communications, redundancy,” David Ubert, senior automation specialist at Black and Veatch, and Eelco van der Wal, managing director at PLCopen, discussed how PLC designs have changed to meet automation and control challenges in recent years.

By Control Engineering March 18, 2024

Programmable logic controller (PLC) insights

  • In a November 9 webcast, “PLC series: PLC hardware speed, I/O, communications, redundancy,” David Ubert, senior automation specialist at Black and Veatch, and Eelco van der Wal, managing director at PLCopen, discussed how PLC designs have changed to meet automation and control challenges in recent years.
  • In Part 4, van der Wal discusses technical aspects and recent advancements in PLC technology.

In the ever-evolving field of industrial automation, programmable logic controllers (PLCs) have been a mainstay, adapting to the changing needs of various automation applications. Known for their robustness and versatility, PLCs remain a preferred choice for machine control, motion control, and even certain process control applications. However, as the demands of modern automation grow increasingly complex, it’s essential to understand where PLCs fit best in today’s industrial landscape.

In a November 9 webcast, “PLC series: PLC hardware speed, I/O, communications, redundancy,” David Ubert, senior automation specialist at Black and Veatch, and Eelco van der Wal, managing director at PLCopen, discussed scenarios where PLCs are most effective, how their designs have changed to meet contemporary automation challenges, and what key criteria end-users should pay attention to when selecting PLCs for specific applications.

The transcript of their presentation has been provided with minor edits and adaptations.

PLCs in maritime and other industries

Eelco van der Wal: PLCs have a pervasive presence in the maritime industry, especially in the multimillion-dollar yachts produced in the Netherlands. These ships are equipped with extensive PLC controls, essential for ensuring their continuous operation. Similarly, PLCs are integral in various transportation systems. The agricultural sector, too, is increasingly embracing PLCs for precise management practices, such as targeted fertilizer application. Additionally, sectors like chemical, oil, and gas rely heavily on PLCs, as previously mentioned by Dave.

The evolution of PLC functionality and software costs

Traditionally, a PLC’s function was to read inputs, perform calculations, and set outputs in a continuous loop, ensuring real-time response. However, in modern software environments for PLCs, task identification at higher levels is possible. A single PLC can manage multiple tasks, some time-based and others event-based. Time-based tasks occur at regular intervals, while event-based tasks are triggered by field changes. The efficiency of event-based processing is that it only utilizes processing power when necessary.

Despite the decreasing cost of hardware, the cost of software development is rising. This increase is due to the growing complexity and dependence on software, with programs becoming larger and expectations from them higher. At some point, such as in the early 2000s for car production plants, the cost of software integration and orchestration exceeded the cost of physical components like buildings, transportation lines, and robots.

Maintenance and updates in modern software systems

A significant portion of software costs today is attributed to maintenance. This includes not only additional programming but also updates, new functionalities, and modifications due to changes in products, laws, or optimization needs. The dynamic nature of software is evident in the frequent updates and changes it undergoes, significantly altering its functionality over time, much like the numerous updates seen on personal smartphones.

The evolving business model in the PLC market

The continuous evolution of PLC technology not only enhances functionality but also shapes the business model of our market. As hardware becomes more affordable and powerful, a phenomenon encapsulated in Moore’s Law, we can integrate increasing functionalities into PLCs. The processing power of PLCs now rivals that of personal computers, allowing for the addition of complex functionalities such as motion control for robots with integrated pneumatic models. This capability to incorporate and calculate entire systems within a PLC is crucial for the market’s expansion. The rate of innovation in PLC technology is not only continuous but also exponential.

Historical development of PLC technology

Looking back at the timeline, in 1970, PLCs were large, heavy, and expensive modules with limited functionality, primarily focused on logic and relay replacement. By 1998, due to Moore’s Law, we could combine more functions on a single module, reducing costs and size. This led to the advent of microcontrollers in 1990, which were smaller and incorporated communication capabilities, enabling the use of remote IO modules.

In the 2000s, the introduction of sliced IO allowed for even more flexibility, connecting modules via fast networks and creating dedicated IO sections supported by various networks. The 2010s saw the rise of multicore CPUs, facilitating multitasking within PLCs – separate cores for logic, motion, communication, and HMI interfaces. Nowadays, PLCs with up to 64 cores are more powerful than many personal computers, offering tremendous capability for running synchronized programs.

Advancements in communication and information exchange

Around 2020, standardized communication via OPC UA (from the OPC Foundation) emerged, transitioning from specific protocols to the exchange of information independent of the communication protocol. This development resulted in the widespread use of high-speed, internet-based networks, with traditional networks like Modbus aligning with these advancements.

The increase in communication speed, from one megahertz to one gigabit, facilitates the exchange of more information. Information models describe where information is located, its name, data type, etc. Various industries, such as weighing systems and oil drilling, are defining these information models. If the models for different devices, like temperature sensors or printers, are standardized, it simplifies connection and integration, making it easier to control and optimize systems.

The future of PLCs: Virtualization and open control systems

Looking ahead, a significant development in the PLC market is the emergence of virtual PLCs. Virtualization and open control systems, like real-time units, are transforming PLCs from hardware-centric to software-centric systems. A virtual PLC is essentially a software task that can run on any platform, be it a PC or a core of any processor. While some envision virtual PLCs operating in the cloud, the feasibility of this model, particularly in terms of real-time performance, remains uncertain.

Implementing virtual PLCs in industry

Companies like Audi are already utilizing virtual PLCs to update hundreds of their PLCs efficiently during brief coffee breaks. This approach leverages IT tools to create, run, control, and maintain PLC protocols within their environment, a stark contrast to traditional hardware-focused setups. However, the fundamental features of PLCs, such as input/output processing, motion control, safety, communication, and security, remain integral.

The role of redundancy, multicore and scalability

Redundancy is crucial, especially in process control applications like power plants and water distribution. Multicore technology, already discussed, enhances the functionality of PLCs. The scalability of virtual PLCs is particularly notable, offering the ability to expand and adapt systems as needed. Ultimately, whether dealing with hardware or software PLCs, the driving force behind their operation is software. The challenge lies in programming these systems to meet specific expectations while managing costs effectively.

Future trends in manufacturing and software updates

In the future, the focus will shift towards creating more flexible production lines with faster changeovers, reduced waste, lower energy consumption, and greater adaptability. Rigid manufacturing lines requiring labor-intensive hardware changes are giving way to instant remote software updates that have been virtually tested. This shift includes the integration of digital twins and simulation technologies. The goal is to move beyond mere updates to a more holistic approach that encompasses the entire lifecycle of the system.

Dealing with legacy hardware and system upgrades

Dealing with legacy hardware is a significant challenge. The trend is moving towards replacing or retrofitting outdated equipment with more modern, efficient solutions. This transition is part of the broader movement towards more adaptable, software-driven control systems in various industries.