Aaron Severa / product manager—HMI, FieldConnex, remote IO / Pepperl+Fuchs
I suppose the answer here might depend on how quickly your company wants to be able to innovate. It’s true that technologies, libraries, operating systems, protocols and everything else tend to move on more quickly toward obsolescence in the PC world than in the PLC world. But, to take another angle on this, those same factors moving more quickly in PC solutions also allow you to more readily embrace the rapid iterations and innovations that come along. Technology advancements are not done just for the fun of it.
There are deliberate motivations behind these changes. Each improvement is done with the intention of allowing users to do more, to do it on a greater scale and to do it with more efficiency. The same forces are applied in both PLCs and PCs, as, underneath it all, these share many commonalities. However, the fact that PCs are designed to be more application-agnostic and less hardware-oriented allows for evolution to take place more quickly.
Regardless of whether you take a stance that is more PLC or PC-centric, an important factor to consider is what dependencies your application has: is there a path forward, and does the vendor have a future-proof plan? The horror stories resulting from Windows XP’s retirement weren’t a result of the need for us to start building systems with a newer operating system.
These resulted from the plethora of software technology providers who had made no forward-looking plans for what comes next. No technology is going to be relevant forever. All will eventually face obsolescence. The key goal is to pick technology providers who have a vision and a plan for how to stay ahead of the curve and who can help carry you forward along the way.
Jotham Kildea / solutions sales engineering supervisor / Iconics
The breadth of applications for PC- and PLC-based control is increasing, and the line between PLC and PC is becoming more nebulous. Driven by the production pressures to reduce costs within manufacturing, increase finished goods part counts and establish a robust log of traceability data to clearly document quality, both PC- and PLC-based control architecture have their merits, many of which you have clearly articulated. The risks of choosing the wrong control architecture can be devastating, and you are absolutely correct in taking an objective perspective when comparing the two control-based architectures. Before we address the risks of PC-based control, two pieces of data should be gathered, the first being the prioritization of the facilities’ objectives; the second are principles to compare each architecture’s specifications to these objectives.
Each of the facilities’ objectives, not only from the perspective of one department, but the facility as whole, should be paired with the facilities’ pressures, which are incentivizing the achievement of the objectives, as well as the facilities’ current challenges inhibiting the objectives from coming to reality immediately. This prioritization will help when guiding the selection between PC- and PLC-based control architectures and even between different PC and PLC manufacturers.
You are absolutely correct that phase-outs can become a source of risk. Moore’s Law does limit the product lifecycle of specific PC models, and software development is continuing at an ever-increasing pace. When helping customers determine between PC- and PLC-based control, our team builds a rubric, focusing on machine performance, developing transparent and simple architecture and leaving future opportunities to easily harvest more data from the system.
Overlaying these three principles with the facilities’ objectives can help focus the team on not only the obvious costs, such as hardware and software licensing, but also the hidden cost, such as first-pass yield or the opportunity cost of not pursuing other projects and training. Many vendors offer both PLC and IPC platforms for control as both have distinct value when helping facilities meet their production objectives. However, both control methodologies maximize machine performance, minimize architecture complexity without compromising robustness and allow for more data harvesting without incurring additional costs.
For the specific application, the value of a PC-based control system may be worth the risk, but it may not. Laying out your team’s needs and future roadmap can offer both PC and PLC control the opportunity to create a solution, which not only generates returns, but also leaves the door open for sustaining that performance in change that is yet to come.
Thomas Kuckhoff / product manager—controller / Omron Automation Americas
To begin, an important difference between an industrial PC and a PLC is the way it executes a program. A PLC is usually a scan-based program, whereas an IPC is event-driven. More businesses are wanting to make their operations more flexible and scalable, and PC-based control provides such capabilities. Understanding end users’ needs and desire for continued growth and sustainability is vital to helping them select the right solution. Both PLCs and PC-based hardware have their place in modern facilities. You can combine them together to get the best of both worlds or look into PACs.
PLC advantages:
• It’s made for reliable operation in very harsh environments.
• Ease of programming and troubleshooting usually follows scan-based programmable software. See International Electrotechnical Commission (IEC) 61131-3 standard.
• Proprietary processors and unique operating systems are resistant to viruses and cyberattacks.
• It supports scalability with easy-to-add expansion modules and long lifecycles of 15 to 20 years.
• It is used in nearly every industry.
PLC disadvantages:
• I/O options are limited since they’re tied into the same manufacturer.
• It can be expensive.
IPC advantages:
• New industrial PCs are even more resistant to harsh environments and extreme temperatures.
• It has enhanced programming capabilities and increased connectivity and investment value.
• It uses more widely known programming languages, such as C++, and is not tied to one hardware platform.
• It has communication between programmed controls and equipment.
• An IPC can control multiple functions on one platform and runs programs and applications that PLCs cannot.
IPC disadvantages:
• They are difficult to upgrade when new Windows versions are released.
• Long-term product support is lacking.
• They are susceptible to hacking.
Gary Guess / product portfolio manager / RS
Programmable logic controllers and PCs can be used to automate specific functions of machines, entire processes or even entire production lines. These processes can include timing, control, sequencing and starting and stopping motors, pumps and valves. The primary thing that sets PLC control apart from PC-based control is built-in or snap-on input/output (I/O). Many types of I/O can be combined in a PLC: analog, digital, thermocouple. While PC control systems have the same types of I/O available, the I/O is often distributed on a deterministic network.
Programmable logic controllers often need to be connected to other systems, typically PC-based, to complete tasks such as supervisory-control-and-data-acquisition (SCADA) and structured-query-language (SQL) database management. Often PC-based controls have these software features and network capabilities built-in.
Since IPCs use the same hardware and software as hundreds of millions of other PCs across the world, there are no shortages of new updates, products and technology to use. Industrial PCs are widely available, versatile and easy to implement into a system. When the hardware and software used in a system are so mainstream, it’s guaranteed that users will always have state-of-the-art computing power at their fingertips. Industrial PCs often mimic a standard office PC in function, making them familiar to operate and maintain.
Industrial PCs may use Microsoft OS, Linux OS and other operating systems to control non-real-time tasks, which means IPCs can be used for multiple tasks beyond the cyclic control tasks. Additionally, IPCs can combine real-time operating systems with non-real-time operating systems. A real-time operating system is a computing environment that reacts to input within a deterministic time period. A real-time clock and turnaround reaction time can often be measured in microseconds. Industrial PCs also have easy connection to the network using Ethernet connectivity.
Industrial PCs are not a niche market. The cost to purchase and maintain these types of control systems are typically lower for a given processing speed or update rate. Industrial PCs also come in a wide range of sizes and power and can be purchased with options that include fanless or high IP ratings, such as IP67 or higher. Maintenance and replacement may be significantly easier and options to upgrade abound. Often, IPCs from one manufacturer can be replaced with an IPC from another. When processing or computing power becomes a limiting factor, there are usually options to upgrade the processor speed, memory, port options or number of network interface cards.
Industrial PCs have the capability to work with all controllers, including PLCs, and networks such as EtherCAT, Ethernet/IP and Modbus TCP/IP. This allows for a more streamlined, purpose-built control architecture that is flexible and scalable.
Danny Weiss / senior product manager / Newark
I’m still a fan of traditional PLCs due to their longevity, long lifecycles and ruggedness. But many PLCs are, at their core, PC-based controllers, as they run a logic engine on a form of Linux or Windows IoT and offer many of the advantages typically associated with PCs, so the line between PC-based controllers and PLCs is becoming blurred.
However, a full-fledged PC can bring many advantages due to its sheer computing power. Industrial Internet of Things (IIoT) integration, databasing and higher-level languages are all very desirable in automation applications, and these are very achievable with PC-based controllers.
Take these precautions to mitigate some of the risks:
• Be sure to use an IPC rather than a standard PC in a cabinet. The ruggedness of the construction will result in a much longer lifespan.
• Be sure to work with a reputable manufacturer and discuss the expected lifespan and opportunities to extend the lifespan. I have worked with more than one company that manufactures IPCs, and they usually offer operating-system upgrades that can extend the useful lifespan of the hardware.
• When selecting a logic engine to run the control, consider a product that is hardware-independent and can be moved around. CoDeSys is a good example of a logic engine that runs on a vast array of operating systems and hardware platforms.
In conclusion, PC-based controllers offer a lot of value and should be considered; just do your homework and contingency planning.
Ted Thayer / principal product marketing specialist—control / Phoenix Contact
First off, you’re right. PC-based control offers undeniable advantages compared to the legacy PLC approach. Industrial PCs (IPCs) offer an unbeatable price-to-performance ratio, and their scan times are incredibly fast (Figure 3).
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