Against the backdrop of increasing digitalisation in industry, wireless systems offer a flexible and affordable possibility for networking machines, components and tools. Various solutions ranging from WLAN to Bluetooth and even special industrial systems such as WirelessHART are being used, depending on the requirements involved.
What is WirelessHART?
A high level of flexibility and productivity are the main requirements for modern industrial manufacturing.
Wireless communication systems are therefore incredibly important, because they allow mobile elements in production – forklifts, robots, mobile workstations – to receive control data and supply status information.
They can also be used to noticeably reduce cabling and installation work – an increasingly important factor in flexible, modularly designed factories in which more and more devices are networked.
Machine networking with mobile communication
Wireless technologies that people know from their daily lives can certainly be used for this purpose – mobile communication, Wi-Fi and Bluetooth have been used in industrial applications for a long time now.
One example is remote maintenance on equipment. For example, the sewing machine specialist Dürkopp Adler offers its customers the option to access the sewing machines remotely for the purposes of maintenance work.
The machines are equipped with mobile communication modems and are connected to a cloud-based platform run by the German telecommunications provider Deutsche Telekom.
This allows them to send machine operating parameters via the mobile-communication network, and to receive control commands. Mobile-communication can also be an interesting proposition for communicating with the machine operator.
Phoenix Contact, a manufacturer of components for electrical technology and automation, offers a mobile communication module which a machine tool can use to send status messages to its operator via text message.
This means the operator is informed of a malfunction immediately, even while they are on a break or in a different area of the factory.
Transport jobs over WLAN
In contrast, Wi-Fi has become widely used in intralogistics in particular. That being said, the use of WLAN in industrial environments repeatedly poses challenges to system integrators, as demonstrated by German brewery Badische Staatsbrauerei Rothaus.
The stored liquids – in this case beer – require that the WLAN frequency of the stacker control system be tuned to work with the resonant frequency of the tank or bottle contents. Otherwise, the wireless connection would be too severely disrupted and operating the stacker would either be restricted or not possible at all.
In cases like these, the industrial truck manufacturer Linde offers the option to use different wireless systems on the stackers. This means that data can be transferred by means of GPRS (SIM card), Bluetooth or WLAN.
If there is no WLAN in the outdoor area, then a mobile connection can be used on the vehicle deployed there to send information to the database.
Furthermore, if the building has areas where there is poor WLAN reception, the stacker can automatically retrieve data via Bluetooth as soon as it nears a permanently installed Bluetooth access point.
However, Wi-Fi or Bluetooth also reach their limits if a production plant has hundreds of sensors, actuators and additional systems which all need to be networked together.
With upwards of 15 devices, this can lead to problems in practice as the devices can interfere with each other.
Additionally, there are noticeable connection problems with wireless LAN in terms of walls, interference signals, machines and metal objects, which can result in unreliable communication.
Stable sensor networks for condition monitoring
The IEEE 802.15.4 wireless standard was specifically developed for industrial sensor networks and is characterised by extremely low power consumption, low data rates and wireless ranges of up to approximately 200 metres.
The cost-effective hardware and the use of royalty-free ISM bands both set the wireless standard apart. This standard is the basis of different wireless technologies including ZigBee, 6LoWPAN and WirelessHART.
Comprehensive sensor networks can be realised using these systems, with one example being condition monitoring – the monitoring of machines and facilities.
The ball bearing specialist SKF, for example, has developed a smart sensor which combines data acquisition and a wireless device into a single battery-powered device which can record both vibration as well as temperature data.
The sensor uses the WirelessHART communication protocol, which can network up to 250 participants in the form of a mesh network. In this arrangement, every connected device simultaneously serves as a router.
If a data path for signal transmission fails, the signal searches for an alternative path. Messages which do not arrive or arrive incomplete are re-sent to the same participant.
This creates a very robust network, such as is required for industrial applications. The possibilities of a mesh network are also offered by other systems such as ZigBee 3.0 or the relatively new Bluetooth Mesh.
Industry 4.0 needs new solutions
However, in many cases, the existing wireless solutions are not enough for future applications in Industry 4.0, the requirements of which with regard to latency, reliability, range, failure tolerance, security and localisation options are often too high.
This is at least what the German Association for Electrical, Electronic and Information Technologies (VDE) cautioned in its German position paper “Funktechnologien für Industrie 4.0” (Wireless Technologies for Industry 4.0).
Among other things, the association calls for the development of new wireless systems based on open, globally recognised standards.
Not only should these offer the required performance and reliability for Industry 4.0 applications, but also the simplest possible installation, operation and maintenance.
The spectrum of industrial wireless communication systems could thus become even broader in the future.