When looking at a typical production plant, numerous applications can be immediately recognized that benefit from wireless communication or even require it. Examples include data exchange with mobile transport systems such as warehouse shuttles or pallet wrapping machines, as well as with cranes. Mobile maintenance or the flexible integration of terminals and machines into the production network are further application examples.

Bring your own device application example: Components such as the 'Anybus Wireless Bolt' enable access to the internal web server of the machine control system and are a cost-effective alternative to HMIs.

© HMS Industrial Networks

In most cases, however, the focus is not on saving cabling costs. Rather, faster and more reliable wireless communication results in cost benefits due to simplified design, greater flexibility and freedom from wear and tear. Against this background, wireless automation networks have already established themselves in numerous production plants. HMS Industrial Networks estimates the market share of wireless networks in factory automation at around 6% of the new industrial network participants installed in 2017.

The buzzword 'Bring Your Own Device' - BYOD for short - describes the trend in which modern smart devices such as tablets or smartphones are used to parameterize and operate machines and retrieve diagnostic data via their integrated internet browser or special apps. These devices now come with wireless technology as standard and offer visualization options like traditional HMIs thanks to the web browser integrated into the mobile operating system. For interlinked systems such as printing and packaging machines, the BYOD approach promises a noticeable reduction in costs: where previously an expensive, permanently installed HMI was required for each individual machine in the interlinked system, technicians can now access each individual machine directly via their tablet or smartphone 'on the fly'. This trend is reinforced by the new Windows 8 and 10-based tablets, which also run standard Windows-based HMI applications such as Win-CC or Labview, which users are used to from the stationary Windows-based HMI. Finally, the connection between the smart device and the production network is established via wireless gateways, which work as wireless access points in these applications.

Radio instead of slip ring

With its compact design, the 'Anybus Wireless Bolt' is ideal for mounting directly on the machine.

© HMS Industrial Networks

Wireless gateways, which are used as wireless bridges, are often used as cable replacements, as they enable wear-free and high-performance data transmission, even in applications with special requirements such as gantry cranes, automated guided vehicles, filling and packaging systems or sewage treatment plants. In these applications, expensive mechanical slip rings and drag chains can be replaced. When using the wireless gateway as a cable replacement, data is usually transmitted in the form of a point-to-point connection.

It is important to select the right wireless technology (Bluetooth or WLAN) and to have the necessary expertise for installation and antenna alignment. Last but not least, the requirements for real-time behavior and the amount of data to be transmitted must be tailored to the capabilities of the wireless solution. Company IT departments in particular are often of the opinion that a large and fast WLAN network is sufficient for all applications, including the production area. However, the various applications place different or sometimes conflicting demands on the wireless technology, which is why separate wireless networks often have to be set up for individual application areas. Time-critical automation tasks in particular should always be implemented via a separate wireless network. The mere fact that there are only a few WLAN channels available, which are usually used by other applications - for example from the office environment - shows this: WLAN is not always necessarily the best choice. In many cases, the use of Bluetooth communication in industrial applications is therefore the better alternative. Almost every communication-capable mobile device today offers an integrated wireless modem that supports both wireless technologies: Blue tooth (IEEE 802.15.1) is the right choice if robustness and stability of the connection are the key criteria. WLAN (IEEE 802.11) is ideal when high data throughput is required. For example, while data between autonomous transport systems and the higher-level production network is transmitted via WLAN, it makes more sense to exchange data with moving or rotating components of a machine via the machine's own Bluetooth network.

The 2.4 GHz band is ideal for use in industrial scenarios due to its better propagation characteristics. In particular, radio waves in this frequency range penetrate walls and obstacles better than radio waves in higher frequencies.

2.4 or 5 GHz WLAN?

However, the frequencies of the 2.4 GHz frequency band are traditionally used by a large number of different radio systems. This often leads to a higher load on the channels.

The frequencies of the 5 GHz band, on the other hand, are often less encumbered by competing networks, as other wireless technologies such as Bluetooth, cordless phones and cheaper WLAN solutions are often limited to the 2.4 GHz band. However, the use of the 5 GHz band also brings difficulties: the radio waves are much more affected by physical obstacles due to their higher frequency. As a result, the range of 5 GHz WLAN transmissions in buildings or industrial facilities is usually somewhat shorter than with a comparable transmission in the 2.4 GHz frequency range (a detailed white paper is available for free download at www.anybus.de to help you choose the right wireless technology).

Industry versus office

The Anybus Wireless Bridge is usually used as a cable replacement in moving applications and enables wireless distances of up to 400 meters.

© HMS Industrial Networks

Industrial applications place diverse demands on the quality of a wireless network that go far beyond the requirements in the office and private sectors. The core requirements for future-proof wireless connections in manufacturing are the highest possible throughput, low latency and good area coverage.

Even if WLAN and Bluetooth are standardized wireless technologies in accordance with IEEE 802, which are also used in the home and office environment, specially designed and functionally enhanced devices are required for use in the industrial sector. In addition to more robust hardware and a wider temperature range, the components must offer flexible installation options and long-term availability. There are also functional differences that determine the suitability for an automation-specific application. These include, for example, optimization for short, cyclical data packets with low latency times, fast and stable roaming, support for specific mechanisms of automation protocols such as Profinet and Ethernet/IP as well as hard real-time prioritization of communication. One device that meets all these requirements for an industrial wireless gateway is the 'Anybus Wireless Bolt' from HMS. With its special design and integrated antenna, it is specially designed for use directly on the machine. The robust IP67 housing combines the connection, communication processor and integrated antenna in a single unit.

The Wireless Bolt supports both WLAN (2.4 or 5 GHz) and Bluetooth. In 'Wireless Bridge' mode, a radio link is established via two wirelessly connected Bolts. In 'Access Point' mode, a Bolt acts as a transfer point between the wired network participants and any other network components connected wirelessly. As an access point, the bolt usually provides wireless access to the machine's control network. This allows machines to be configured, parameterized and operated via tablet PC or smartphone. The current operating status of the machine, production quantities or diagnostic data can also be queried wirelessly. The range of the wireless connection is up to 100 m.

Author:
Michael Volz is Managing Director of HMS Industrial Networks in Karlsruhe.