A growing trend in industrial plant design is wireless connectivity. Recent technological advances have made wireless protocols significantly more robust and reliable than previous versions, enough so to rival traditional hard-wired connections. The result is an increasingly wide variety of products and solutions for wireless data transfer for upstream communications in industrial applications. Plant managers have rejected wireless connectivity in the past for its lack of reliability and security, but newer protocols and infrastructure systems have been developed to offer greater benefits without the drawbacks of outdated wireless systems.
Modern industrial wireless networks offer numerous options for the infrastructure of a plant or operation that would otherwise be limited in connectivity by hard-wired connections. By eliminating the necessity for each access point to be joined by a physical connection, industrial operations gain the access to vastly increased connectivity and more flexible, versatile configuration possibilities.
The most common wireless networking standards for industrial applications have been 802.11a, b and g. However, there is a newer and better standard, 802.11n, which utilizes multiple antennas to increase data rates (a system referred to as MIMO, or multiple-in multiple-out). This standard, when paired with the correct equipment, offers more transmission paths resulting in data transfer rates in the hundreds of Mb/second. In turn, the increased receiving paths produce greater reliability in received quality and minimize the impact of RF interference.
While this newer wireless technology is now readily available to industry professionals, even if they are aware of it, many are probably reluctant to adopt it due to their previous experiences or preconceived notions having to do with the security and reliability of these types of networks. As a relatively new technology, wireless connectivity has undergone a growth process including several iterations that were less than satisfactory for industrial applications. As a result, many industry professionals erroneously associate their past experiences involving residential or commercial-grade wireless networks with the more robust, reliable industrial-grade options currently available.
This reluctance to adopt wireless technology can result in industry personnel never experiencing a correctly engineered industrial application of the technology. Just like hard-wired applications, there is a very large quality gap between commercial and industrial performance levels. Due to their technological development and age, hard-wired networks have had more time to develop industrial-grade levels of quality to provide reliable and secure connectivity. The same is and has been taking place with wireless networks, which have now reached a level of quality capable of delivering effective solutions for industrial operations.
Industrial Network CategoriesIn industrial automation systems, there are typically two types of networks in operation: the communications or supervisory network (PLCs communicating information to computers, HMIs, or other controllers for monitoring and coordination purposes) and the automation network (PLCs communicating machine control information to and from I/O, motion, vision, and other automation modules). The information traveling throughout these networks can be categorized into either upstream (information traveling away from the automation system) or downstream (information being received by the automation system). Upstream network traffic consists of information being sent back to the control center or end user for diagnostics, status, and management purposes, while downstream traffic consists of information being sent from the PLC to the hardware responsible for executing the automation and motion control functions.
Wireless networking can be used in many upstream communications networks for industrial applications due their less critical, lower speed, and less deterministic nature. These networks include standard protocols like TCP/IP and Ethernet/IP, which can be easily adapted to transmit information via wireless instead of hard-wired Ethernet connections. Upstream communications are considered to be less critical to the overall process than downstream communications in a properly engineered distributed-control architecture.
Downstream network traffic is much harder to adapt to include wireless connectivity due to the nature of modern automation and motion control systems. They typically require extremely high data transfer rates and very high reliability using protocols that include failure-proof handshaking. EtherCAT is the most recent phenomena to come to the automation world with its blazing fast speed and jitter of less than 1 us. Very little effort relatively has been expended into wireless architectures for these types of applications. ZigBee is one low-power and short-range protocol that has been developed and is being used in the commercial markets. While it has been looked at in the industrial markets, there is very little of it available still at this point.
Industrial Wireless ApplicationsDue to its unmatched versatility, wireless networking can make some industrial applications much simpler and, in some cases, provide options that would have previously been impossible using traditional hard-wired connections. These benefits are proving effective for a wide variety of industries, from refining and manufacturing to remote drilling and mining applications.
In one case, an industrial plant had a rail-mounted crane that needed to transmit information back to the control center wirelessly. The only option when the plant was built was to not transmit the data back at all. How does one effectively run a communications cable from a building out to a rail car on a track that is half a mile long extending through and under the building itself? As wireless technology emerged, they implemented a wireless platform that regularly dropped connectivity and lost data as a result. After replacing the transmitters with a newer, more robust platform and better system architecture, the plant can now transmit important data wirelessly without the fear of losing the connection. This is a prime example of the reliability offered by modern wireless networks that are often overlooked by industry professionals.
Another useful application of wireless networking is in factory monitoring. With traditional hard-wired connections, thousands of feet of wire would need to be routed from place to place in a time-consuming and expensive installation process. By implementing a wireless network with minimal installation requirements, factory managers can save time and money while putting a system in place that can be easily updated and maintained. The critical processes taking place in a factory can then be consistently relayed to a central control room thanks to the high throughput of modern wireless transmitters. With a robust wireless network implemented throughout a factory facility, there is always the option to add new connection points or transmitters with minimal changes to the system infrastructure.
In yet another example, a coal mining operation in China utilized wireless networking to relay information from underground tunnels to control rooms on the surface level. Integrating a wireless network both above and below ground offered the operation an unprecedented amount of flexibility in transmitting information.
An additional application of wireless technology is in oil field applications. With a sizeable network of well sites and controllers spread out over a large geographical area, running wired connections to each remote site would be a considerable undertaking. Traditionally, cellular signals have been used requiring cellular cards and service contracts. However, implementing an 802.11 wireless network is as simple as equipping each well site with a wireless router capable of relaying information back to the control center. These routers are also capable of being bridged to receive and transmit information from sites that are farther away. Putting many of these units together is referred to as a mesh network, in which all stations in the network cooperate in distributing data. Additionally, mesh networks can utilize self-healing algorithms to continue their operation even when a particular node stops working or when a connection loses strength, providing outstanding reliability for the entire network. In one particular application the nodes were located as far as 20 KM away from each other and could still successfully transmit information with a throughput of more than 100 Mb/s.
ConclusionWhile many larger companies are still reluctant to rely on wireless networks to transmit important information in industrial settings, there is an increasing acceptance rate of the newer, more robust wireless options that are now available. These wireless platforms offer a greater combination of speed, functionality, and flexibility than any previous types of wireless networks as well as the majority of hard-wired connections.
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