So, in this era of global transformation towards intelligent manufacturing, what kind of PLCs do we need? In particular, what characteristics should medium-to-large-sized PLCs, often hailed as the "crown jewel," possess?
First, it's important to clarify that the high-end PLC we're talking about today is different from what it was 10 years ago, or even 5 years ago. It's not that a PLC that was high-end 10 years ago can still be called high-end today. Because society has developed, more advanced technologies have emerged, and the standards for judging what constitutes "high-end" have changed over time.
In the current era of intelligent manufacturing, the following five characteristics have become essential requirements for high-end PLCs:
1. Carrying ability is no longer the key; communication ability is more important.
Today, we all see that control system architectures have been fully Ethernet-based in the industrial sector. Over a decade ago, when fieldbuses were emerging, a high-end PLC was considered to have distributed control capabilities, the ability to support numerous distributed stations, and fieldbus connectivity. At that time, the ability to handle data transfer was the most important performance indicator for a controller. However, with the increasing intelligence of field devices and the need for reliable, stable, and available control systems, the CPU's data transfer capability is no longer the key differentiator between high-end and low-end systems. The focus now should be on the coverage of Ethernet communication in the field, which directly determines the system's control level over field equipment. Furthermore, we are currently in a transitional period. For example, while fieldbuses are still in use, upgrades don't necessarily mean they are no longer compatible with older fieldbuses. However, the future trend is towards Ethernet, making Ethernet support even more important, while compatibility with existing fieldbus protocols is also crucial.
Previously, Ethernet was a communication method used between PLCs and host management software. Its advantage was that it could transmit larger amounts of data and allow more control stations to connect to the network. However, for field control, even with a large number of field I/O stations and devices, the actual communication volume is not as high as that between the PLC and the host computer. But it has higher requirements for real-time performance and reliability; packet loss rate is crucial, and real-time performance and data transmission verifiability are also very important.
With the development of lean management in factories, more and more factories are starting to use higher-level operation and maintenance management software such as MES systems and asset management systems. Some people also call this smart manufacturing or digital factory. This is because more and more process customers are looking for more refined control and hope to use PLC systems to retrieve data from the field directly to improve efficiency and real-time performance, thereby enhancing overall operational efficiency and management capabilities.
The consensus among both PLC manufacturers and users is that full Ethernet connectivity is essential. This is well demonstrated by Schneider Electric's Quantum+.
2. Information security of PLCs has become indispensable.
In the context of a "one-network-to-the-end" system, a significant issue arises: once the network is connected, linking on-site production equipment with management software and even the cloud, it opens channels between management and data analysis systems and dedicated industrial control systems. This significantly raises the requirements for information security. When data exchange occurs from on-site devices, the entire communication network is established. If information security issues arise at any point during this process, they can potentially have cascading effects. If upper-layer software security is inadequate, intrusions could occur from there and continue down the chain. Similarly, if security measures are weak at the interface between the control and management networks, intrusions from above or below could lead to a domino effect.
Therefore, information security is equally important for the PLC side. In the past, information security wasn't considered during PLC development because mainstream high-end PLCs were based on technology from 20 years ago, when information security was nonexistent. Later attempts to address this issue involved adding external protection, either through manufacturer updates and patches via the underlying operating system, or, as many information security companies and groups are doing now, adding firewalls and network security switches. However, this is only a temporary solution. Like a person with many ailments, if you take medication every day, you might seem better, but you won't be able to withstand new problems. Defense in depth can provide layered isolation and protection, but true security requires each control level to be robust on its own. This is a major issue that new-generation high-end controllers must consider. Starting with the PLC itself, regardless of other deployments, it must be protected from attack, possessing inherent security capabilities.
3. The focus is no longer simply on speed, but on stability and reliability.
Since the advent of the industrial age, production processes have gradually matured. Changing a process is now very difficult because we've essentially modified everything that could be changed; in other words, it's hard to significantly alter the processing speed of the control system. Regarding the efficiency or precision improvements in the process flow, which are of utmost concern to users, optimization can be achieved in two ways: one is through refined management of the entire production process and materials; the other is through refined management of the equipment.
However, from this perspective, our equipment, under the control of the previous generation of high-end controllers over the past 20 years, has no problem with processing speed and can fully meet process requirements. Faster control systems are no longer effective in improving factory operational efficiency. It's like driving on a highway; reaching 500 mph is meaningless because, for stability and reliability, a car that can reach around 200 mph is sufficient. Higher speeds are unnecessary and may even pose potential risks. In this situation, pursuing speeds far exceeding those of high-end processors, as was the case in the past, is pointless. But one thing remains the same: stability and reliability. Just like why would I drive a car instead of a motorcycle? Because safety and reliability are paramount.
For high-end controllers today, it's not about how many points they can handle or how fast their processing speed is, because those are no longer important in the previous generation. Now, any small or medium-sized controller can easily match the handling capacity and processing speed of a large controller. The core elements are their security, stability, reliability, and system communication capabilities. In the past, large PLCs were mainly used for large systems, which require inter-system communication, collaborative management capabilities, and the ability to communicate and support higher-level computers. These capabilities are what determine whether a system is a high-end or small/medium-sized control system.
4. Miniaturization and ease of use are the trends.
In the past, we said that bigger was better, because there was no other way, as small products were already being made as small as possible. For electronic products, under the same performance, the smaller the size, the higher its technological content. Furthermore, we know there's a major trend now: as industrial products become more accepted, they're moving into the civilian sector. Especially in recent years, as various countries' industries have developed to a certain level, many public works projects, such as large buildings, have started using PLCs for control. Previously, embedded controllers were used, but their versatility, expandability, and maintenance required specialized personnel. For these reasons, PLCs have become increasingly popular.
The demand for distributed systems is expanding rapidly, even in traditional heavy industries where the requirements for distributed installation of control systems are increasing. In the past, we had dedicated control stations, especially in traditional industries, where all PLCs were placed in a single main control station. However, this resulted in numerous wiring connections, complex construction and maintenance, and high costs when these modules were connected to field devices. Therefore, distributed I/O is needed.
In the future, all equipment will evolve towards intelligence. Motors and testing instruments in the field will likely all have Ethernet interfaces, connecting directly to the control system. The main control room might house a cabinet full of controllers, with numerous switches connected to a multitude of network cables. In this scenario, should PLCs be made large or small? The control philosophy is changing, and so will factory design. Future monitoring system screens will be very large, but equipment will need to be used as compactly as possible to improve comfort and efficiency. Considering this, controlling 3000 points currently requires ten cabinets, which will become increasingly impossible in the future.
How to place high-end chips with original functions on a smaller circuit board, or integrate chips with more powerful functions into a smaller circuit board, requires professional design and manufacturing capabilities. Not everyone can make it very small. It is easy to make the electronic control system large, but difficult to make it small. This is because solving EMC interference, heat dissipation, and circuit layout problems in a smaller size to achieve a controller that is more powerful than the original is a manifestation of high-end technology.
5. The inheritance of experience and professional quality are essential.
High-end controllers aren't something that can be achieved simply by a product suddenly appearing one day. It's different from consumer electronics. For example, someone who used to make monitors or computers could suddenly start making mobile phones and quickly become a core player in the industry. However, the industrial control field doesn't have this advantage. A mobile phone malfunctioning or experiencing a problem won't have a major impact. Users don't prioritize stable operation like they do with industrial equipment. In industrial control, even a slight stop or problem is a serious issue. Therefore, the importance of legacy systems and expertise is paramount.
Why is it that among so many PLC manufacturers, only a handful can provide high-end controllers? Not everyone can do it, and it's because of the inheritance of experience. If you suddenly enter the market without experience, it's not like software development where you can just find a few experts to code something. It involves all the chips, all the layouts, EMC interference immunity, and all aspects are a summary of experience, accumulated and optimized over many years.
Another key factor is professionalism. Why is professional quality so important? There are many manufacturers capable of producing controllers, especially those using PC-based chips, which offer readily available chips and operating systems. In the current PLC industry, there are established standards for programming and system architecture. While creating a copy is easy, the level of professionalism in that copy is crucial. Without experience and specialized knowledge, it's difficult to produce a truly professional product. This is why many manufacturers can only produce low-end controllers. The higher the level, the more difficult it becomes – this is the reason why many companies, despite years of effort, struggle to move into the high-end market.
