Industrial control systems have long relied on classical control theory. With the increasing integration of computer technology in industrial settings, the need for efficient feedback mechanisms has become more critical. This involves how control commands are delivered to actuators and how the resulting system responses are returned to the control system through sensors. In complex industrial environments, fieldbus technology plays a vital role by enabling reliable, fast, and stable communication. This ensures that industrial control systems can quickly access accurate field data, process it efficiently, and issue precise control commands.
1. **Basic Model of Communication**
Communication is the process of transferring information from one point to another, similar to telephone, radio, or television. Industrial communication systems also require transmitters, receivers, and communication links. These links can be twisted pair cables, coaxial cables, fiber optics, radio, or microwave. The transmitter modulates the data, while the receiver demodulates it, and the rules governing this exchange are known as protocols.
2. **Special Requirements for Industrial Communication**
Unlike general communication, industrial communication must operate in harsh environments. It often deals with process data, state variables, and maintenance information. Key features include real-time performance, frequency, jitter, response time, synchronization, and time-space consistency. Real-time communication is essential, ensuring that responses meet strict timing constraints.
3. **How Fieldbus Meets Industrial Communication Needs**
The OSI model defines the physical layer, which includes not just cables and connectors but also signal encoding, bandwidth, and transmission methods. The data link layer manages data packets, with fieldbuses typically divided into LLC and MAC layers. The application layer defines how devices exchange data and manage device states.
Fieldbus communication data is usually categorized into identification data (process variables between controller, sensor, and actuator) and general messages used for configuration and maintenance. One of the key advantages of fieldbus over traditional 4-20 mA analog signals is its digital nature, offering better noise immunity, reduced cabling, and enhanced diagnostics.
3.1 **Replacing the 4-20 mA Wiring Scheme**
While 4-20 mA was once the standard, fieldbus technology now offers a more advanced solution. It enables distributed intelligence, requiring smart sensors and actuators with digital communication capabilities. Although this increases equipment costs, it enhances system flexibility and performance.
3.2 **RS-232 and RS-485 Electrical Standards**
RS-232 and RS-485 are interface standards, not buses themselves. They define electrical and mechanical characteristics, such as voltage levels and pin functions. RS-232 uses voltage levels to represent logic, while RS-485 uses voltage differences. RS-485 supports multi-drop networks, making it suitable for many fieldbus systems.
3.3 **Manchester Coding and Symbol Concepts**
Fieldbus systems often use Manchester coding, where each symbol contains a transition that helps maintain clock synchronization. Understanding symbols, bits, and baud rates is crucial. A symbol may consist of multiple bits, and the number of symbols per second determines the baud rate.
3.4 **Communication Media**
Fieldbus typically uses wired connections like twisted pair, coaxial cable, and fiber optics. However, with the rise of wireless technologies, many fieldbuses are now incorporating wireless communication to meet evolving industrial needs.
3.5 **Communication Models**
Two main models exist: client/server and publisher/subscriber. The client/server model is ideal for state data, where a client requests data and the server responds. The publisher/subscriber model is suited for event-based communication, where data is pushed to subscribers.
3.6 **Communication Mechanisms**
Communication can be periodic, event-triggered, or based on responses. Periodic communication is common in control systems, where data is transmitted at fixed intervals. Some systems use both periodic and acyclic communication, depending on the data type and urgency.
3.7 **Error Control and Flow Control**
Error detection and recovery are handled at the application level. Fieldbuses often provide two communication mechanisms: one for error detection and another for flow control. These ensure reliable data transfer even in challenging environments.
4G Industrial Router
Analysis of advantages and disadvantages of 4G industrial routers
First, what is the classification of industrial routers?
Industrial Router (a communication device that can be divided into 2G routers, 2.5G routers, 3G routers and 4G routers according to network standards.
For users, you can communicate with the Internet by setting a default gateway on your PC or network device. In fact, the default gateway configured for network devices is the packet export for network devices. After the packet is sent to the Ethernet port of the router, the router performs the next job, so the router is an Internet relay.
Second, how do industrial routers work
So how does the router forward the packet? Just like getting somewhere, you need to place a route. This route is a routing table. This routing table contains all the destination network addresses owned by the router, as well as the best path to reach those networks through the router. This is because there is a routing table, so the router can forward packets according to the routing table. That's how routers work.
Understand what is an industrial router and how it works, it is not difficult to understand the advantages and disadvantages of the router. Here we focus on the advantages and disadvantages of 4G industrial routers.
Third, the advantages of 4G industrial routers
For networks interconnected via single-protocol industrial-grade wireless routers, the same or different protocols can be used at layers 1-2. Layer 3 uses the same routable protocol and requires the same or compatible protocols at layer 4 and beyond.
Industrial routers can perform complex routing calculations and are suitable for connecting three or more large networks with complex network topologies.
Industrial-grade routers can isolate broadcast storm information in the source network, thereby reducing and mitigating the impact of broadcast storms.
Multiprotocol industrial wireless routers can be used as network interconnection platforms using different communication protocols because they can connect to the network using different communication protocols.
The entire network router can also be used as a bridge to handle non-routable protocols.
Industrial 4G routers enable you to isolate unnecessary communications so that the interconnected network maintains its own area of independent management and control, thereby improving network security performance. Therefore, industrial-grade 4G routers are commonly used as firewalls to restrict access to the internal and external networks (Internet) of the LAN, as well as the internal areas of the LAN, and act as network masking.
It can provide reliable transport and prioritization services, and industrial LTE routers do not need to maintain a persistent connection between networks that communicate with each other.
Complete Netcom router network segmentation improves network performance and reduces host load.
Third, the advantages of 4G industrial routers
High price
When installing an industrial LTE router, it is difficult to install and maintain due to the large number of initial configurations
If you spend more time processing, the transmission performance of the entire network of the industrial router will decrease.
Unlike Bridges, routers across industrial networks are protocol-related. Each advanced protocol used for network connectivity must be configured separately, and an industrial-grade network-grade router with a separate protocol for each protocol must be provided.
Industrial Netcom routers do not support non-routed protocols, so when interconnecting multiple networks, there are restrictions on the protocols used by the connected networks.
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