10 reasons to choose PC-based control
Feb. 27, 2015 - PC-based control systems for industrial applications have been around in various forms for as long as PCs themselves. In fact, PCs have been relied upon for machine control just about as long as PLCs have. In certain circles, however, there continues to be a misunderstanding about the reliability and capability of an Industrial PC (IPC) for “real” machine control applications.
When we speak of PC-based controls, we are talking about an industrial control system that utilizes a PC designed as a control platform. While functionally the same as an office PC, the IPC is specifically designed to be rugged enough for demanding plant environments. IPCs are tested to be a reliable computing platform with operating specifications to withstand plant environmental factors such as temperature, vibration and shock — far exceeding the commercial PC. Components used are qualified, standardized and available in the long-term, with product lifecycles that can go toe to toe with any PLC and win.
The PC-based control platform offers a wide range of reliability and capability advantages, among other benefits. Here are 10 reasons that make this case:
1. PC control leverages mainstream hardware computing technology
The IPC uses the same basic technology used in the millions of PCs produced everyday around the world. The latest technology gets implemented in the IPC without the need to prorate development costs over many years and millions of devices. No matter which PLC one may use, that supplier can never match the sheer volume of product produced by a single PC supplier. The net result is that the PC control platform is always modern and always reflective of state-of-the-art computing power. The PC is a mainstream societal technology, yet the PLC is quite the stranger to most of society.
2. PC control leverages mainstream software computing technology
Many IPCs use Microsoft operating systems for non-real-time control tasks. This means that the IPC can be used for multiple applications. Not only will the IPC perform as the real-time control platform, it can also be used as the HMI platform simultaneously. It also provides the connection to the enterprise network using standard Ethernet (NIC) connectivity. Other non-Microsoft operating systems, such as Linux, can also be used.
3. IPCs are lower in cost
IPC manufacturers take advantage of their economy of scale to produce lower cost products. The PLC manufacturer creates a proprietary electronics platform, the cost of which is prorated over thousands of units rather than millions of units... the unfortunate by-product then is that the PLC platform ages quickly from a technology perspective. An outdated IPC can be replaced anytime, likely with a lower cost model that reflects the powerful dynamic in the PC world of “increased power at ever lower costs.”
4. IPCs are more powerful
Many IPCs today use multi-core, 64-bit architectures with several gigabytes of RAM and have virtually unlimited mass storage, providing a tremendously capable computing platform. The PLC is designed for a single task and is equipped with just enough processing power to perform that task. Compare this with the typical PC computing capability and there really is no comparison.
5. IPCs are future-proof
The PC is the ultimate “de facto” standard. There is no end in sight, either to the form factor (ATX, 3½ inch, PC104) or the concept. Combining with Windows operating systems and IEC 61131-3 programming software creates a computing and control platform that will “always be there.” Compare this with the traditional PLC product family with a three to five year general availability and again, no comparison.
6. PC control protects Intellectual Property (IP)
A PC control solution is implemented in software, abstracted from hardware. The customer’s investment is maintained in a truly “open” architecture that can be moved from one IPC brand to another with rarely anything more than a software recompile. Compare this with a PLC solution which is usually a function of software developed on proprietary hardware. The software cannot be separated from the hardware, so there is no abstraction between the two. Unavailability or lack of support on a PLC platform usually means a complete redevelopment of the software application, starting from scratch.
7. PCs are more maintainable
The IPC control solution uses technology known to the masses. The Windows environment is familiar and comfortable to more people and ultimately to more of today’s maintenance personnel whether they admit it or not. IPC users can utilize more internal resources than would be available to support a PLC platform.
8. PC control provides simpler control architecture
The power of the IPC combined with a high speed, real-time control network, such as EtherCAT, means the control architecture can be compressed into a single layer. There is no need for gateways, switches, protocol converters or data links. All control devices are on one Ethernet-based CAT5e network.
9. PC control provides better diagnostics
The power of Microsoft is perhaps most evident in the number of third party applications available for the operating system. A PC-based control platform easily exports control information for offline processing by third party applications and tools, resulting in powerful diagnostic and analytical tools that can provide improved performance, maintainability and reliability. By comparison, the PLC has few resources available for advanced diagnostics. A maintenance person often takes extreme action such as “forcing a contact” to resolve machine operational issues rather than being directed to the “root cause” by advanced diagnostics.
10. PC control converts hardware “boxes” to software applications
If you think about what is in a special “box” that performs an auxiliary function within the control system (for motion control, measurement, safety or something else), you will see that it consists of some sensor electronics, a processor, some memory and usually special software or firmware. The PC control platform has all the necessary computing technology to accomplish the required functions of that box already. In PC-based control, the sensor or other field device simply gets connected to standard I/O. The special application can be implemented in powerful software, either in real-time using IEC 6 1131-3 programming tools or in standard computing languages, such as C and C++.
In conclusion, a PC-based control system provides a powerful, flexible, maintainable and very cost-effective alternative to a traditional PLC-based system. There are many thousands of PC-based control applications around the world — and here in Canada — that provide many of the benefits described in this article. Granted, there is still resistance to change from those who still swear by PLC-based platforms in the name of stability or reliability, or a friendly relationship with a distributor. Change may require additional work to migrate over to a more modern and powerful system, but no business has ridden the “we’ve always done it this way” mantra to long-term success in today’s globally competitive industrial marketplace.
Joe Ottenhof is General Manager of Beckhoff Automation Canada Ltd. He has over 30 years of experience in industrial automation and controls. Ottenhof is an Engineering Technology graduate of St. Lawrence College, Kingston, Ont., where he studied Instrumentation and Process Control.
This feature originally appeared in the January/February 2015 issue of Manufacturing AUTOMATION.
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