Wireless Interfacing For Industrial Machinery

April 18, 2007 -- Researchers at TRLabs are currently working to analyze the performance of the ZigBee wireless protocol under the influence of noise with the objective to establish design rules for wireless systems in industrial applications.

Background

Current industrial data and communication systems, such as those found in excavators, contain sensors, actuators, and monitors that are connected to controller modules through wire harnesses. However, the hard-wire scheme is often expensive to install because complex wiring routes are required to protect the vulnerable wires. Furthermore, when part of the wiring network fails, it becomes extremely difficult to determine and access the location of the failure, which leads to costly repairs. These factors, combined with the safety concern of failing machinery, has led TRLabs, in conjunction with Vansco Electronics, to look for a wireless solution for industrial data and communication systems using ZigBee mesh networking.

Built on top of the IEEE 802.15.4 standard, ZigBee is a low data rate, low cost, reliable, short-ranged, and secure wireless communication protocol. As well, ZigBee devices have long battery life due to low power consumption, allowing them to remain active for long periods of time with minimal attention. Furthermore, ZigBee's support of mesh topology and self-forming and self-healing features allows for the creation of reliable networks. For example, a mesh network is reconfigured without manual intervention when new nodes are added or when old nodes are removed, and data is automatically rerouted to new paths when old paths are broken due to unreliable links or nodes.

Despite appearing to be tailored to industrial uses [1], there is still speculation on the performance of the ZigBee protocol in noisy environments. In an industrial setting, a ZigBee network will have to be able to coexist with other wireless technologies operating at the 2.4 GHz unlicensed Industrial, Scientific and Medical (ISM) frequency band. Other types of noise that could be encountered in the field include radiated noise (emitted from electric arcs or electric discharge from powerful motors), conducted noise (due to poor grounding), and induced noise (caused from the current present in cable wiring). While other researchers in the field are addressing the coexistence issues, no research has been done with regards to determining the effects of radiated, conducted, or induced (RCI) noise on the ZigBee protocol. TRLabs researchers are taking the lead and pioneering the effort to determine the effects of RCI noise on the ZigBee protocol. They have developed a novel methodology, state-of-the-art noise modeling, and designed an apparatus, which will provide the ability not only to measure the effects of RCI noise, but also to establish design rules that will help wireless network designers in creating reliable ZigBee networks for industrial applications.
Benefits…

• Reduction in installation and repair costs
• Increased reliability through self-healing mesh network
• Flexibility in the addition and removal of nodes

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