Automated cranes provide a critical function in the metals industry. These cranes depend upon the reliability of wireless communications within their working environment. The identification of the proper hardware to provide the necessary reliability is crucial and can become one of the more difficult aspects of the project. Trutegra has extensive experience with this technology and can provide the right hardware for the job.
Since most cranes travel over large areas, roaming from one access point to another is inevitable. Due to the nature of these cranes, safety is a critical issue. It is essential to know that the roams happen in a very short, predetermined period of time. Each roam is therefore scheduled to avoid a hard handoff, instead of completing a soft handoff with a very clean transition. Over the years much has been learned by Trutegra to make that happen reliably. Another layer of complexity is added by the coupling of video traffic, which consumes an enormous amount of bandwidth. However, unlike safety traffic, it is not considered to be critical, and a few frames can be dropped with no adverse effects. In contrast, Level 2 communications are critical and require advanced networking technologies, such as quality of service (QOS) controls, to ensure timely delivery of messages. Safety traffic and PLC to PLC communications are prioritized over everything else. Video gets whatever is left over a certain percentage of the total available bandwidth. To make all of this work reliably requires a deep understanding of industrial networks.
A vital precursor to establishing a reliable wireless network is to develop a good channel plan. That plan should map out the particular channels on which each radio operates, eliminating interference from the corporate IT or other machinery in the area. It is important to execute a wireless site survey ahead of time. This survey involves walking around the area with a laptop and running highly specialized software and taking numerous measurements. The RF environment is analyzed and channel usage in terms of positions relative to GPS is documented. This is then coupled with a spectrum analysis report that identifies noise and other transmissions that may be overlooked in the traditional site survey. All of this data is then compiled into a map of the RF in the area.
From the data obtained via the site survey, a channel plan for the installation of the automation technology can be established. Hence overlapping channels are avoided, working with corporate IT to exclude any channels that are needed for the automation equipment. This approach means that the system is designed to work together from the onset, rather than simply starting up with the hope that it will work.
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