How are Wireless Sensor Networks employed in Industrial Automation

Wireless Sensor Networks, or WSNs, are infrastructure-less wireless networks that use thousands of spatially distributed sensors to monitor environmental and physical parameters, like temperature, motion, pressure, etc. Each sensor node collects data and transmits it to a sink node or a central hub using radio frequency. At this main location, it is processed, stored, and analyzed by a computer or a human. These smart sensors are self-configured, meaning that they can automatically supervise processes without any manual intervention.

What does WSN architecture offer?

WSNs have several key components:

Sensor Nodes

A sensor node comprises of a sensing unit (or a transducer) that measures physical parameters, a micro-controller that processes the data, an ADC, a transceiver for wireless communication, and a power source which is usually a battery.

Network Topology

WSNs come in three main structures for radio communication.

• In Star Topology, the sink node can send or receive information from various remote sensors. However, information cannot be exchanged between sensor nodes. In a low-power simple network, the central hub or base station is required to be within the radio transmission range of all the nodes present in the network. This structure is also not as robust as some of the other structures since the sink node alone is responsible for managing the whole system.
• Mesh Topology enables direct communication between different sensor nodes and with the sink node. A node can communicate with a node outside of its transmission range via another node. This allows for a limitless expansion potential. 
• Cluster Tree Topology balances efficiency and scalability by grouping the nodes in a cluster with a cluster head that can communicate with the central hub.

Communication Protocols

Common communication protocols for WSNs include Zigbee, BLE, Wi-Fi, and LoRaWAN to define rules for data transmission and address and handle errors. WSNs operate ISMsband for Zigbee and BLE or sub-GHz band for LoRaWAN, balancing range and data rate needs.

Data Acquisition and processing

Sensors measure specific environmental parameters like temperature, motion, and pressure. Data is then processed at the node level to reduce the transmission load by noise filtering and data aggregation. Pre-processed data is then wirelessly transmitted to a sink node, which forwards it to a central server (or cloud) for further analysis.

Apart from these, Power and Data management, scalability, and reliability are also important in any modern WSN architecture. 

Power and Data Management

Sensor nodes are designed to maximize energy efficiency and battery life, using low-power components and sleep modes. Additional energy harvesting capabilities like solar panels may also be included.

On the other hand, data aggregation and data fusion are reliable ways to improve efficiency and accuracy. Data transmission protocols like MQTT (Message Queuing Telemetry Transport) or CoAP (Constrained Application Protocol)  ensure timely data transmission.

Scalability and reliability

A scalable design that allows for  the addition of more sensor nodes without significant changes to the existing network infrastructure

Mesh topologies and multi-hop communication enhance network reliability. WSNs are designed to continue functioning even if some nodes fail.

WSNs in industrial settings

The WSN technology has been recently employed in industrial automation from short-range personal area networks (PANs) to cellular networks and even global communication through satellite.

WSNs come with huge benefits over wired counterpart solutions. Remote sensors with local decision-making capabilities save the cost of wires, labor, energy, and materials. Additionally, they make significant improvements in the monitoring and make the whole process a lot more feasible.

 Here are some of the common industrial applications of the WSNs.

Supervisory Control and Data Acquisition (SCADA)

WSNs improve SCADA systems with real-time data acquisition and transmission to the central node. The central node then aggregates and transmits the data to the SCADA master station via standard communication links such as Ethernet/IP, Wireless Protocols, Cellular Networks, Modbus TCP/IP, or OCP (OLE for process control). The wireless nature of the WSNs simplifies the systems and reduces operational costs. While both SCADA and WSN systems face security challenges, the flexibility and modern design of WSNs better adapt to new security protocols and measures.

Diagnostics, Testing, and Maintenance

WSN’s sensors are strategically placed at critical points of industrial machinery to detect any deviation from normal operating conditions. Then different data analysis and diagnostic techniques such as condition monitoring, predictive maintenance and root cause analysis are employed.

Following are a few specific applications.

1. Vibration analysis is done using sensors to detect vibrations of rotating equipment like motors, pumps, and compressors to monitor machine health.
2. Thermal sensors may be used to monitor overheating of critical components.
3. Pressure of the hydraulic or pneumatic systems may be monitored with pressure sensors to give information about leaks and blockages that could result in potential malfunction. 

Continuous and Batch Processing

For batch processing, different sensors are employed in fermentation plants to ensure optimal conditions for microbial growth. Meanwhile, data in petrochemical plants is continuously monitored to ensure that the reactions stay within safe limits.

Motion control and robotic equipment

Position sensors, accelerometers, and gyroscopes are deployed on robotic arms to monitor motion, i.e., position, speed, and acceleration. Environmental sensors like proximity sensors are also used to detect obstacles. These sensors are commonly used on Automatic Guided Vehicles (AVGs) and form a feedback loop for motion control and dynamic path planning.  WSN integration allows to communicate wirelessly with the control system. This reduces the need for wiring and allows for more flexible deployment of sensors.

WSNs are also used in discrete product manufacturing, automated metering, remote monitoring, inventory, and personnel management.

Why are WSNs better suited for Industries than wired solutions?

Apart from these, WSN technology is expected to grow in a number of areas, which include the detection of rare events, periodic data collection, real-time data acquisition, control, and mobile robots. WSNs are a more feasible solution to mobile applications like bearings of motors, engines, oil pumps, vibration sensing units on packing crates, or such inaccessible or hazardous environments. The wired solutions are not practical for isolation requirements for highly humid environments, high magnetic fields, or vibration. Major advantages of WSNs over the wired options are listed:

Flexible installation and upgradation

• WSNs provide ease of deployment for complex industrial environments where running cables can be challenging
• WSNs are easily scalable as it is easier to integrate new sensors in addition to rapid reconfiguration.

Reduced cost for installation and maintenance

• The absence of cables reduces the cost of installation and labor.
• They typically require lesser maintenance as there are no wires to wear out.

Decentralized automation functions

• With distributed control, control functions are closer to the point of data collection. This betters system’s responsiveness.
• Local processing relieves the load off the central systems. This can improve the system’s overall efficiency.

Regulation and Safety

WSNs help meet regulatory and safety standards, as they are usually the cables or restricted areas that risk loss of life or equipment.

Moving or rotating equipment

Wireless networks are ideal for sensing the environment or physical parameters around rotating or moving machines, as wired connections are impractical.

Fault localization and isolation

Without too many wires, it becomes easier to locate and isolate faults quickly in wireless networks.

Short-range technologies

Automation systems have become more efficient with the introduction of short-range technologies that have interfaces to WANs and form a heterogeneous network. 

Micro-electromechanical systems (MEMS)

• MEMS technology uses small, integrated wireless sensors with robust communication capabilities.
• These sensors are less susceptible to physical damage. It makes them more durable and reliable than their wired counterparts.
• MEMS-based sensors can perform complex functions and yet maintain a small footprint.

Challenges

The Industries can face several challenges with WSN integration. For example, co-channel interference, and noise impact the coverage area and data reliability, where signal strength is affected by multi-path propagation. Other signals from the ISM bands also degrade the signal quality. Additionally, the noise from heavy machinery may also adversely affect the signals from sensors. With compromised reliability, it becomes more important to maintain data integrity, especially for operation-critical data such as safety alarms or protection.

These factors present that WSNs are technically very challenging systems that require expertise from various disciplines. The requirements for industrial settings are usually stricter than those for residential or commercial domains since the system’s failure endangers lives or leads to significant production losses.

Conclusion

WSNs are a modern technology with numerous advantages over their wired counterparts. These advantages include the affordability of installation and maintenance, easier accommodation of new devices, suitability to sensing applications in unreachable places, and overall simplicity by avoiding wiring. However, the technology is still new and has the potential to grow against challenges such as cyber threats, slower communication, and cost. At DO Supply, we’re dedicated to supporting your automation needs with a wide range of high-quality equipment. While WSNs highlight the future of industrial connectivity, our expert tech and sales teams are here to ensure you find the right automation solutions to elevate your operations. Reach out today to explore our extensive inventory of automation equipment tailored to your business! If you would like to learn more about machine-to-machine communication, feel free to check this article out here.