Understanding the unique wireless demands of AGVs in manufacturing
Traditional manufacturing plants rely on personnel to manually load, move and unload goods. This is time-consuming, dull and potentially dirty and dangerous work.
Would you rather have your workers focused on these monotonous activities or on critical tasks like identifying opportunities for improvement, verifying quality standards, monitoring production metrics and making data-driven decisions to optimize operations?
In an effort to reduce labor costs, reassign workers to high-value tasks and improve operational efficiency, today’s modern manufacturing plants are installing technology like automated storage and retrieval systems (AS/RS). Automated guided vehicles (AGVs) can be an essential part of an AS/RS to transport materials and goods within a warehouse or plant.
These AGVs must be monitored in real-time to ensure safety, track performance and improve efficiency. To monitor large numbers of AGVs in manufacturing, a stable wireless network is required. It must be able to support:
- Mobility so AGVs can move freely within the coverage area
- Flexibility so AGVs can adapt to different tasks based on updates and instructions
- Real-time communication so terminals can communicate with control systems and other AGVs and equipment to coordinate movement
- Remote monitoring and control so status, performance and location can be tracked
- Scaling so new terminals can be added to the system without adding more cabling or extensive reconfiguring
- Seamless roaming by automatically switching between different wireless access points without lost connections or delays
- Low-latency switching so data can be processed and shared with minimal delay
The importance of early wireless network planning
Thanks to the proliferation of wireless networks to support smartphones, laptops and other mobile devices, network managers sometimes assume it will be simple to deploy wireless access points throughout their warehouse or plant.
They don’t always realize all the factors that must be considered in these unique environments:
- The need for connectivity despite multiple layers of steel. Metal can obstruct, diffract and reflect signals. It can also create multiple paths for signals to reach the receiver, as well as make it difficult for signals to locate wireless nodes. This can all cause signal distortion, interference and downtime.
- Incredibly high demand for low latency. Fast-moving AGVs in manufacturing require “order and prohibition” to ensure low latency. In other words, to operate smoothly, they need a structured and well-coordinated environment that involves precise scheduling, clear pathways and organized workflows. They also require rules and restrictions that help them avoid certain areas, operate at safe speed limits and prevent accidents. These rules and restrictions depend on low latency to make sure AGVs get messages fast enough to respond.
- Interference from other wireless applications. In plant environments, both 2.4G and 5G wireless networks are used. This can create interference and signal degradation if multiple devices transmit and receive signals on the same frequency at the same time. In addition, plants have many types of equipment and machinery in operation that generate electromagnetic waves and further contribute to signal interference.
If network managers don’t understand these environmental factors, their wireless networks may not be deployed or managed properly. This lack of understanding can lead to operational problems like:
- The inability of AGVs to search for and connect to wireless networks due to insufficient signal coverage
- Additional interference created by too many wireless access points being deployed in the plant
- Multiple devices using the same or adjacent frequencies due to unplanned and unmanaged channels that cause bottlenecks
- Equipment being exposed to inconsistent voltage levels that damage hardware and result in AGV connectivity issues
- Lags in data transmission due to the inability of AGVs to find the nodes they need to connect to
Common performance issues in wireless plant networks
Once wireless networks are operational, network managers must also be able to identify root causes of performance issues and downtime so they can efficiently resolve them and ensure that production continues.
There are numerous factors that affect the stable transmission of wireless signals. Here are a few common examples that impact AGVs in manufacturing.
RF interference
Radio frequency (RF) interference is divided into two types:
- Same frequency interference
- Adjacent frequency interference
In same frequency interference, wireless devices deployed in adjacent areas are set on the same channel. In adjacent frequency interference, wireless devices are deployed on adjacent channels.
In wireless networks, at the same absolute time and in the same absolute space, only one device can transmit and receive wireless data in one channel.
In addition to radio frequency interference from wireless devices, there may be RF interference from the environment in (frequent mechanical vibration or complex electromagnetic interference). Manufacturing environments often struggle with managing RF interference.
Deploying access points in the right places, as well as proper channel management and the use of advanced wireless protocols, can help reduce these problems.
Hidden nodes
Hidden nodes are a common issue in industrial plants wireless communication.
As shown in the figure below, within the coverage area of an access point, there are no less than two clients that can send and receive data using the access point. When Client 2 is communicating with the access point, Client 1 will also send data transmission requests to the access point because it’s not aware of Client 2’s existence.
At this point, the collision of data from two clients on the same channel can cause one client to remain in a data retransmission state, resulting in unstable production.
In this example, compared to Client 1, Client 2 is a hidden node.
Proper placement, advanced roaming protocols and adjustments to signal strength can help avoid this issue.
Roaming problem
Wireless networks are designed so terminals can move without being constrained by space and cables. When using wireless networks, roaming situations are inevitable. The terminal must switch from the coverage area of one access point to the coverage area of another access point during its movement.
Roaming is a phenomenon that occurs constantly throughout the entire wireless network in industrial environments.
Roaming switching is divided into active roaming and passive roaming. In active roaming, the terminal actively scans the spatial wireless signal strength during the cycle, selects the appropriate signal access point according to the built-in algorithm and quickly roams over. In passive roaming, the access point detects terminal connection status based on algorithms and actively kicks out “unqualified” clients.
Both active and passive roaming require advanced algorithms provided by wireless devices.
If roaming problems occur as a result of network congestion, handoff delays or insufficient coverage, then AGVs may lose their wireless connection when moving between access points. This can lead to communication interruptions, causing AGVs to stop or pause.
Proper access point placement, channel planning and the use of advanced roaming protocols are critical to support this capability.
Your journey to deploying AGVs in manufacturing
Belden can assess your specific needs to help you make the best choice for your environment. Our team has extensive experience in not only wireless network design but also in production and manufacturing.
Our complete connection solutions can help you transmit data as reliably as possible—and with very low latency. From initial concepts and site surveys to launching wireless networks and configuration support, your journey to deploying AGVs in manufacturing starts here.
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关于作者
Alex Liu是一位经验丰富的无线工程师，专门从事无线通信技术应用，擅长无线网络规划、优化和故障排除，拥有八年以上的无线应用经验。