Do all wireless solutions solve real industry problems?
09 February 2021
Brett Binnekade, an Applications Engineer at Festo, talks about the applications for wireless technology in the automation industry.
Wireless technology refers to devices that allow us to communicate without using cables or wires. With this platform, machines can communicate over long distances. Wireless technology plays a role in solving complex engineering problems. By using modern, standards-driven wireless technologies, designers and machine users have access to new tools that can help transform and simplify their working lives. Wireless technology offers benefits such as cost-effectiveness, freedom from wires and easy setup – but only if the technology is appropriately applied.
Wireless near and far
Despite the many benefits that wireless technology can claim, distance is a factor that should be considered when machine users purchase wireless solutions. At long distances, the cost and simplicity benefits trump their counterparts by negating cost and sometimes impossible cable runs. When used at a short distance, for example 10-15 metres, the benefits of wireless usually don’t outweigh the challenges. The cost and complexity of a short distance wireless solution are often much higher than the short cable option, even for impossible applications such as continuously rotating indexing tables, where the use of a slip ring has proven to be more robust.
“For short distances, the power output of the transmitter must be set to prevent over-saturation of the receiver,” explains Binnekade. “But, at low power outputs, wireless solutions become more susceptible to jamming.”
In wireless technology, jamming is defined as the disruption of existing wireless communications by decreased signal-to-noise ratio at receivers, through the transmission of interfering wireless signals. Jamming is different from regular network interferences because it is the deliberate use of wireless signals to disrupt communications. Intentional interference is usually an act of interrupting or preventing communication in devices, so jamming can occur at different levels – from hindering transmission to distorting packets in legitimate communications.
Industry 4.0 and I/O Links
The next generation of industrial advancement, which is referred to as Industry 4.0, aims to inter-connect and computerise the traditional industries such as automation. The objective in Industry 4.0 is to make the factories smart in terms of improved adaptability and resource efficiency, as well as the improved integration of supply and demand processes between the factories.
“Wireless solutions play a significant role in the transformation to Industry 4.0, because they assist in moving data from point to point,” says Binnekade. “But installing wireless technology alone will not give you a smart factory. There are other factors that need to come into play.”
Interoperability of products from different suppliers, transparency and easy connection of network participants are key factors that help identify if a wireless solution is part of Industry 4.0 methodology. Another key indicator would be if the device provides diagnosis and big data from the shop floor level to the cloud via standardised protocols, i.e., MQTT and OPC UA or AMQP.
So how is wireless connectivity achieved? In automation, wireless solutions must not only conform to a specific company’s IO-Link standards, but also international standards. IO-Link for wireless technology is an extension of IO-Link at the physical level and defines wireless communication between sensors and controllers in the automation industry. It can also be integrated into a range of products in the industry to avoid cabling.
Binnekade advises: “When incorporating wireless technology, it is vital to adhere to a standard that does not lock you in and prevent the communication between brands, types and models as this would be moving in the opposite direction to Industry 4.0.”
Questions of frequency
The 2.4GHz band found in most wireless devices provides coverage at a more extended range. Many Wi-Fi enabled technologies, both in the automation industry and in a domestic setting, use the 2.4GHz band – including microwaves, Bluetooth, garage door openers and many other devices. This is something that needs to be taken into account when considering a wireless solution.
“Due to the large bandwidth consumed by Wi-Fi devices, as few as three Wi-Fi hotspots in an area can completely consume the 2.4Ghz band”, says Binnekade. “This is a danger because when multiple devices attempt to use the band at the same time, overcrowding occurs, resulting in system faults and downtimes.
With more wireless products becoming available, the existing frequency channels are becoming more congested. All the wireless devices we use operate within frequencies that have been set aside for free use and are called ISM bands. These ISM bands, especially the 2.4Ghz one, are heavily congested by devices we are very familiar with, such as Wi-Fi and Bluetooth. These devices all fight for channels to communicate over because only one channel or frequency can be used at a time.
“Most devices use a shotgun approach and transmit at randomly selected channels and hope for the best,” explains Binnekade. “If the transmission does not get through, they try again and again, which causes more congestion and delays.”
This phenomenon is commonly known as noise or interference. This is where frequency blacklisting and adaptive frequency hopping can help. However, the wireless device needs the intelligence to check which frequencies are being used and selects available channels in every transmission cycle. The lack of these features can heavily impact the performance and stability of a machine or plant.
Final thoughts
In the automation industry, reliable and effective solutions are required to keep production moving. New, technologically advanced solutions are introduced in the market every day. However, it is of the utmost importance to identify your machine requirements to make an informed decision. With wireless solutions, always consider how interference will affect the process. Delays of 250 ms are common if the transmitter has to resend data due to interference and this can have a detrimental effect on a machine running at 200 parts per minute. Besides wireless technologies, you can also explore digital solutions such as the Festo Motion Terminal (VTEM) that solves real industry challenges.
“It is also important to understand that when a device is deemed wireless, the wireless aspect of it is for data communication,” concludes Binnekade. “The device will still require electrical power and, if it incorporates pneumatics, it will require an air supply line as well.”
So, as with any other aspect of automation, wireless technology requires careful consideration and planning to maximise its benefits.
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