Wireless sensor networks: Overcoming deployment challenges on the factory floor

The widespread deployment of ZigBee networks in industrial applications may be coming sooner than anyone expected.

The low-power wireless sensor and control networks are extending the capabilities of factory automation systems to physical spaces and functions never before possible. Recently released studies by research firms like Harbor Research (www.harborresearch.com), On World (www.onworld.com) and ABI Research (www.abiresearch.com) predict a rapid acceleration in the adoption of this technology over the next 12 to 36 months.

A major catalyst for this adoption is an upcoming wave of new ZigBee products. Over the past few years, more than a quarter billion dollars of investment has been put into development of the underlying technology for these wireless networks, including low-power, low-cost silicon; ZigBee-compliant network stacks; and development tools. This investment has allowed major OEMs to standardize on ZigBee, and soon they will begin pushing these products to market. The availability of these products will provide companies with the hardware components necessary to move forward with ZigBee deployment projects on the factory floor.

Other key factors that will accelerate the deployment of ZigBee applications are corporate initiatives focused on energy management and stringent operational standards, which are supported by the capabilities of ZigBee.

Putting ZigBee to work
The expected applications of ZigBee include energy management, advanced process control, safety enhancement, machine monitoring and maintenance, as well as temperature and vibration monitoring. But how do you get these wireless applications to work in production operations?

It is important to begin discussing this issue now because there are some critical hurdles and challenges that organizations will run up against when they move forward with their deployments. To help with the transition from wired to wireless, there are a number of questions that manufacturers need to ask themselves.

Key questions – DEPLOYMENT
Before deploying and commissioning ZigBee networks, manufacturers must first consider:
• How do I plan for the quantity and placement of the wireless devices in the venue, particularly when the existing staff has little experience deploying wireless RF devices?
• How do I create a ZigBee application that can be installed by an electrician or other professional who is typically in charge of wired installations?
• How do I create a system whose installation begins on-site by an electrician and is completed by a specialist remotely?
• How do I embed enough automatic capability in ZigBee devices so that they can operate effectively, securely and easily at the time of the device’s commissioning?
• How does the installation team establish a simple way of binding each wireless device to the location where it is installed, so that both the device and the application understand the device’s functional placement and role?

One common thread that runs through each of these questions is the issue of how to successfully deploy a wireless application using the same team that is responsible for the traditional wired sensors and actuators. Very few of the teams that currently oversee wired sensor networks in industrial settings have extensive experience working with RF devices, and most companies will not have the luxury of an RF-trained engineer to support every step of a ZigBee application deployment. This presents a significant obstacle to ZigBee deployments, which is different than the installation process for wired sensors. Wireless enables freedom of choice, and that will lead to a larger volume of wireless devices. In turn, this means that most of the wireless devices will have to have a level of automated intelligence embedded in them to enable easy commissioning and flexible use. Addressing these challenges will require advanced planning to automate deployment issues faced by the people who will actually have responsibility for installing the ZigBee application.

Key questions – BUILDING APPLICATIONS
When building ZigBee applications, organizations must ask themselves:
• How can I get all the disparate components of a ZigBee network to operate as a unified system?
• How can I accelerate integration of the ZigBee application with other systems within the facility so that it becomes a fully integrated extension of the company’s technology infrastructure?
• How do I build the network with automated functionality and network intelligence that addresses the lack of a human interface on most of the devices within a ZigBee network?

One of the most compelling and powerful characteristics of ZigBee applications is that they connect device capability in ways that have previously been impossible to accomplish or even to imagine. That strength of the technology also causes new operational challenges because these applications bring together devices and technologies that have previously not worked together. The process of making these disparate components talk to one another and operate as a unified system is daunting and often requires expertise in atypical areas of technology. Planning ahead to select devices and components that minimize these interoperability issues is very important. Likewise, it will be valuable to have processes and technologies that will help automate the process of building out the application and overcoming interoperability snags that occur along the way.

Key questions – MANAGING THE NETWORK
To manage a wireless network’s health and performance, manufacturers have to think about:
• How can I proactively manage the network to ensure reliability and performance?
• How do I dynamically monitor and manage radio consumption to conserve battery power in wireless devices?
• How do I run diagnostics when there is a network performance issue?
• How do I manage network load between different channels or subnets?
• If I have redundancy in the network, in order to maximize reliability, how do I manage the network in real time to deal with issues such as interference and switching channels to improve performance?

One of the things that will catch many organizations by surprise is the difference between wired and wireless networks when it comes to management and maintenance. The diagnostic process, for example, is different for a wired network than for a wireless one. Whereas troubleshooting a failure in a wired device is limited to examination of elements within sub-sections of a wired circuit, performance issues with a wireless device have multiple potential causes and the deductive process of identifying the true cause is complex. More importantly, the network itself must be imbued with the automated intelligence to handle these monitoring and management chores. This will create unforeseen changes for technical teams who are experts in wired systems, but new to wireless networks.

Key questions – ENSURING SECURITY
Security is an important consideration for wireless networks. To ensure the network is secure, organizations must ask themselves:
• How do I ensure that a wireless device is appropriately secured for the application and the function? And how do I begin that device’s life in a secure fashion?
• How do I put a system in place that allows that security scheme to be flexible and secure?
• How do I build easy-to-design-and-manage capabilities into the network that establish a hierarchy of access that aligns access privileges with the functional uses of an application?

The question is not whether wireless can be secure; ZigBee networks can and do meet the stringent security requirements at the network level in industrial settings. The question instead is how to make them secure in the application context that not only achieves a user’s security objectives, but also provides a flexible platform that supports different purposes of the device and the needs of the organization over time. Advanced work is critical for achieving these twin objectives of security and flexibility.

Looking ahead
The questions outlined here are by no means exhaustive. They are meant to provide a starting point for the process that an organization will embark on as it begins planning its wireless deployment. The operational challenges that companies face in building, deploying and managing wireless technologies are real. Advanced planning will help overcome these challenges. Companies need to maximize the level of automated intelligence built into these devices, to minimize the complexity of living with these applications day-to-day once they are operational in production settings.

Tim Enwall is the founder and chief operating officer of Tendril, a provider of network operating platform software for building, deploying and managing ZigBee networks. He can be reached at 303-951-4361 or tenwall@tendrilinc.com.