Discussions about industrial networks and their installation worldwide are not as widespread as one might expect. In reality, far more factories are unnetworked than networked. Michael Bryant, director of the PROFIBUS industry organization, estimates that despite efforts from all industries, only 25% of the potential industrial network market has been developed to date. Most companies still hardware-connect individual devices and controllers to PLCs or low-precision systems. When a pressure sensor and a reading display box are separate, what constitutes a "network" is essentially a worker carrying a notebook and moving between various devices. If you're not planning a major overhaul in your factory, remember that existing products offer a wide variety of options. From many vendors' perspectives, industrial networks are incredibly diverse. For example, there are at least 50 different fieldbus platforms. The sheer size of this subject can be daunting when you first encounter it. Moreover, in reality, any network, regardless of size, involves at least two technologies, the specific choice depending on the distance between individual field devices and ERP or IT networks. [align=center] Figure: Today's networks can cover everything from single bus devices to large IT or ERP network systems. Practice has proven that, to date, no single network platform can cover the entire system from a limit switch to top-level management. Furthermore, network architecture is designed for different objectives. On one hand, you might want to simplify the wiring from each machine to the PLC as much as possible; on the other hand, your manager might expect to see the actual operational output of the current manufacturing process simultaneously in a hotel office in another country. These are two very different projects, but both fall under the category of industrial networking. Why is networking necessary? With such profound and complex technology, why would some people prefer to leave the world of hardware? What were the shortcomings of the old-fashioned notebooks? The first and most clichéd answer to these questions is that networking saves on wiring costs. In fact, networking was initially designed to reduce the need for individual wiring from each device to the controller's I/O ports. Controller companies have designed dedicated Fieldbus operating platforms based on different practical needs, which is why there are so many platforms. Depending on your situation, saving on wiring and infrastructure costs remains a significant consideration. As networks become increasingly complex, the reasons for implementing them also increase: ■ Factory safety systems and control functions use the same network; ■ Controllers can provide methods for diagnosing system problems and resetting equipment without rewiring; ■ If there are network lines, these new devices can transmit more information; ■ Production Asset Management (PAM) procedures need to be operated through the control network; ■ As IT networks move down the enterprise level, their ability to communicate with other devices makes the entire enterprise more interconnected. Tom Phinney, a professor at Honeywell Process Solutions, advises: “The significance of networks lies in their reasonable cost, not their novelty. Don’t change a network if it doesn’t break down. Don’t change it unless it’s for economic reasons. But that doesn’t mean there aren’t potential areas for improvement. There are many applications that urgently need significant breakthroughs in cost reduction, dissipation, and maintenance costs, but these require a great deal of commitment. This requires increased awareness, greater attention, and industry building. Introducing more precise instruments into factory network applications is an effective way to achieve these goals. You can use the auxiliary information from smart devices to predict maintenance problems. Command your flow meter to provide noise signals, and if you repeat this a few times, you can observe changes and detect sludge. You can’t do all this with just 4-20mA.” Adds Katherine Voss, executive director of ODVA, says, “Today, companies all over the world, regardless of size, are connected! We want more than just control of manufacturing processes; we need access to process information anytime, anywhere! A wave of manufacturing networking is coming. The era of copper wire connections is over; seamless, routable networks are emerging.” " Analyzing from the Bottom Given the complexity of industrial networks and the overlap of many areas, any categorization of networks would be quite messy. The suggestions here are conceptually specific to the current topic, not referring to any particular level. If we consider discrete field devices as the bottom-level nodes of the entire network, then the PLC is the first major level operating at this bottom. While other network technologies exist above or below the PLC level, these rarely jump to higher levels. Networks that interconnect PLCs and connect PLCs to higher-level devices typically do not extend downwards. Conversely, networks below the PLC level are generally not used to interconnect PLCs, although some more complex fieldbus platforms can change levels, but they rarely extend to higher levels. The simplest network is probably connecting a group of discrete devices to a PLC. These devices are connected to I/O cards via hardware and do not use a network at all. However, this becomes very expensive and cumbersome as the number and distance of devices increase. The simplest network uses a single fieldbus to connect everything, reducing the number of wires and making PLC configuration much easier." Even when setting up a relatively small network, you must figure out the types of devices you'll be connecting. This determines how much data your network will handle: ■ Small data items, such as limit switches, photovoltaic cells, proximity sensors, etc., are 1-bit devices and require a simple bit-data network; ■ Medium data items, such as smart devices, smart instruments, frequency converters, small-cycle controllers, etc., will require more complex fieldbus technology; ■ Large data items, such as robots, human-machine interfaces, large-cycle controllers, etc., will require complex fieldbus technology or Ethernet. The data processing speed of each device multiplied by the number of devices gives the total capacity of this industrial network and the speed required by the network. If you have enough 1-bit devices, the capacity requirement can reach the level of more complex instruments. "What types and capacities of I/O does the network support?" asked Mike Darnell, a systems integrator at Prism Systems. "For example, it's normal for a paper mill to move around about 5,000 data points in their daily operations. Ethernet is sometimes squeezed out by low-end I/O ports, and Ethernet devices are limited to the low-end market, but it's actually a perfect solution for large applications." High-end market users are gaining a deeper understanding of Ethernet technology and generally believe that its specialization is lower than that of fieldbus platforms. For those already using networks, it's crucial to consider how networks will change over the next 3-5 years. Larry Komarek, Automation Product Manager at Phoenix Contact, advises: "Will you be using a large number of the same type of devices? Or have you already seen an increase in the data volume required for each device? When you add intelligent devices, or digital devices with diagnostic or status information analysis capabilities, the data volume of these devices will increase accordingly. If this is the case, it's simply a matter of investing now versus investing later. If you want to save money now and continue using your existing fieldbus, consider the rate of change in your factory. If you're already struggling with low system scalability, do you have the time to replace it? If your business decision is to avoid introducing an Ethernet platform due to cost savings, make sure you consider the future costs and time required to implement an Ethernet platform." " Changes at the PLC Layer " Once networks are no longer confined to the PLC level, project scope expands significantly and becomes more open. PLCs need to communicate with each other, for example, with HMIs, providing data to historical databases, and uploading information to engineers, enterprise users, and IT networks. These applications significantly change the network itself, making the situation completely different above and below the PLC layer. Some complex fieldbus platforms support PLC peer-to-peer communication, while communication between PLCs and the enterprise layer requires Ethernet technology. As the transmission rates of industrial Ethernet devices increase at double-digit rates, its applications are growing rapidly. At least 10 different platforms are competing, each with its own advantages and disadvantages. Some are dedicated platforms, while most are tied to large manufacturers, although they all claim their products have an open architecture. Currently, Ethernet interconnects PLCs, smart sensors, remote I/O modules, HMIs, and connects them to upper-level systems such as IT and ERP networks. Carl Henning, Vice President of the PROFIBUS industry organization, suggests: "Use the right tools for the right jobs. It seems a range of network architectures will be needed to complete the same project in the future." "Find a suitable platform, don't use an IT network to connect limit switches! If I were the engineer in charge of this project, I would first check the number of devices and their complexity. I would consider the integration requirements of this platform with the production system. A good engineering decision is irreplaceable." Eddie Lee, International Industrial Ethernet Product Sales Manager at Moxa Technologies, sees Ethernet technology expanding into various industries. He points out, "Today, Ethernet is already playing a significant role in barcode scanners at Walmart. This is a case of network applications achieving commercial success. And the same technology is penetrating the manufacturing industry even more widely. Perhaps I'm looking too far ahead, but it's definitely coming." Two Case Studies Optimistic Change A tobacco processing plant used a combination of machinery and skilled operators to manufacture a wide variety of cigars and other products. Before the plant was fully automated, management recognized potential cost savings and the possibility of improving productivity through a more efficient network system. Alabama used Prism Mobile Systems to integrate a sparsely automated, older system. Ultimately, the system connected 21 PLCs, 61 RFID tags, 223 drive units, 7 HMI consoles, and countless other older devices using two fieldbus systems and Ethernet. “With this modern network infrastructure, our customers can now access real-time production data,” said Keith Jones, president of Prism Systems. “The end result is improved efficiency for plant operators and a higher quality product for consumers.” " It's still necessary to maintain Hytrol's position as one of North America's largest suppliers of standard customer conveyors. They produce a wide variety of products, from simple lever conveyors to high-speed slider package sorters. These products are used in large shipyards and large container retailers in various distribution centers. The most basic requirement for these sorters is good network performance. A complete unit is 500-600 feet long and has 1000 I/O ports, operating at speeds up to 700 fpm. A discrete I/O device generally includes the following components: proximity switches, photoelectric sensors, encoders, barcode scanners, authenticators, etc. Surprisingly, at any given moment, a large amount of information can be read into the processor. All I/O ports are updated every 3-4 ms. This places high demands on the speed of the PLC and also depends on the support of the network hardware. "Running a large number of I/O ports at high speed over long distances is a worst-case scenario because a large number of fieldbuses and controllers cannot be processed." "They're either too slow or their directionality is off," says control expert Wendell Rogers. Currently, Hytrol primarily relies on hardware-integrated I/O modules with high-speed interfaces to simplify large-scale cabling. The company continues to experiment with new network technologies to achieve better performance. In contrast, smaller fieldbus facilities can remain relatively independent, while Ethernet solutions are vulnerable to hacking. No network architecture is 100% secure, but there are several layers that can block unauthorized users. This is another topic you need to consider carefully, and there is plenty of information available. Make an informed choice . Before spending time considering your options, it's best to identify if your company has the following specific criteria: network platform, preferred vendors, training mechanisms, or parts catalogs. These strategies are hard to ignore when it comes to time and money. Similarly, it's best to decide whether you want to build a specific system tailored to your company or simply build a similar system based on experience elsewhere. In such cases, your choices can significantly impact finding the ideal solution for many reasons. Once you've established your operating model, the next step is to assess your current situation and needs: ■ What should the network do? Is the network, strictly speaking, simply a way to save on cables connecting I/O endpoints to the PLC, or is it just for transmitting real-time data to the CEO's office or overseas? ■ Do your existing devices and networks need to communicate and interact with each other? Unless you're building a new factory, all machines or processes, legacy equipment, and systems will need to be integrated. ■ You need to ensure that consultation is available at every level, from top to bottom. Your company's IT department may need this input data as they will be connecting to the system. ■ How secure is your integrated network? ■ Will this be a self-developed project, or will you be using an off-the-shelf integrated system? ■ Have you anticipated the effects after use, or have you considered future maintenance? Before looking at large systems or processes within the scope of your company's network establishment project, you first need to list the actual equipment used and clarify their respective roles. Due to the complexity of individual devices and the large amounts of data they need to transmit, they need to be isolated. As part of your engineering work, you'll need to choose the security and control functions of your network software. You can't rely solely on fieldbus and Ethernet to run your processes, manage plant equipment, schedule maintenance, or generate production reports. These functions are all present on the network in operation. There are many network systems and control software options available, and a considerable amount of feedback on them. The Control Engineering website is an excellent platform to continue your in-depth research. (Reprinted from Control Engineering China website)