Reliable Real - Time Wireless Automation

Wireless automation is an emerging field of research, engineering and industrial development that aims at significant savings in installation times and costs of cabling in automation systems, while providing a new level of flexibility for system design, reconfiguration, and agility. It is applicable to both new automation systems and retrofit applications. The use of wireless technologies is rather common in consumer applications, consider, for example, cellular phones, cordless desktops, etc., but the strict real-timeliness and reliability requirements of automation systems have limited the use of wireless technology in industrial environments. There are, however, a variety of existing industrial applications of Bluetooth, ZigBee and WLAN networks, but very rarely these are used in time-critical applications. The bulletproof wireless technologies are few, and hence the technologies have not yet spread to wide use in industrial automation. The main concerns in this respect are related to the problem of how the reliability and real-timeliness of wireless communications could be guaranteed. Wireless automation considers a wide range of technologies that are used in an automation system to enable wireless communications on one or several levels of the system, including factory, automation system, and field device levels. The wireless communications are used to deliver measurements and control values, device configuration information and other process data between the devices, control rooms and servers. This chapter reviews the wireless automation standards and related technologies, but also certain medium access control (MAC) and routing protocols and control design approaches are discussed that together could solve the problem of achieving a reliably working real-time wireless automation system. We will also consider simulation of wireless automation systems, which is essential for the network and automation system co-design validation, and evaluate some candidate system designs with a suitable simulator. The focus is on the field device level, and hence the technologies used for device to device wireless communication for control purposes are addressed. The main contributions of this chapter include a review of current technologies used in wireless automation. We also discuss and propose a new MAC and mesh routing protocol (limited broadcast protocol, LBP) to enhance the reliability and real-time performance of wireless automation systems. We will also demonstrate how the modelling and simulation of packet drops could be done and integrated in the co-design procedure of wireless automation systems. Finally, we will investigate some practical control solutions and designs for wireless automation with a full-scale simulator to validate the proposed designs.