Fieldbus refers to a digital communication network used in industrial environments to connect measurement and control devices, often referred to as a field network. It enables communication between sensors, terminals, and controllers, replacing traditional analog signals, contact switches, and ON/OFF signals with digital data transmission. This digital approach allows for time-division multiplexing, multi-point communication, and improved performance, reliability, and ease of maintenance. By reducing the amount of wiring needed, it also lowers installation costs and simplifies system configuration.
Key features of fieldbus include:
- **Communication capability**: Field control devices are equipped with communication functions, enabling the construction of a robust underlying control network.
- **Open standards**: Communication protocols are standardized, ensuring interoperability between different devices from various manufacturers.
- **Function block standardization**: Devices with similar functions can be easily interchanged due to standardized function blocks and structures.
- **Decentralized control**: Control functions are placed at the field level, resulting in a highly distributed system architecture.
Advantages of fieldbus technology include:
- Integration of self-controlled devices into information networks, expanding their application scope.
- Reduced installation costs by connecting multiple devices over a single pair of twisted wires.
- Lower maintenance efforts and enhanced system reliability.
- Greater flexibility in system integration and configuration.
The development of fieldbus technology is expanding across various industries such as manufacturing, process control, transportation, buildings, and energy.
**Mainstream Fieldbus Technologies:**
1. **Foundation Fieldbus (FF)**
Developed by a consortium of companies including Yokogawa, ABB, and Siemens, FF has evolved from merging ISP and WorldFIP standards. It operates using a simplified OSI model (physical, data link, application, and user layers), with two speed variants: H1 (31.25 Kbit/s) and H2 (1–2.5 Mbit/s). It supports both wired and wireless communication and is widely used in process automation.
2. **CAN (Controller Area Network)**
Originally developed by Bosch, CAN is widely used in discrete control systems. It is an international standard (ISO 11898) and supports high noise immunity, short frame structure, and multi-master operation. It offers speeds up to 1 Mbps and distances up to 10 km at lower speeds.
3. **LonWorks**
Created by Echelon Corporation, LonWorks uses the full ISO/OSI seven-layer model and supports object-oriented design. It can operate over various media, including twisted pair, fiber, and infrared, and is known as the "universal control network" due to its versatility.
4. **DeviceNet**
Based on CAN technology, DeviceNet provides a low-cost, open network solution for device-level communication. It supports up to 64 nodes, with speeds ranging from 125 Kbit/s to 500 Kbit/s. Its producer/consumer communication model allows flexible device connections.
5. **PROFIBUS**
A German and European standard, PROFIBUS includes three variants: DP (high-speed data transfer), FMS (field message specification), and PA (process automation). It supports a wide range of transmission rates and media, making it suitable for diverse applications.
6. **HART**
HART (Highway Addressable Remote Transducer) combines digital and analog communication over existing wiring, serving as a transitional technology. It supports master-slave and multicast communication modes and is commonly used in process industries.
7. **CC-Link**
Launched by Mitsubishi Electric, CC-Link is a high-speed network (10 Mbit/s) that connects control and field devices. It is widely used in Asia and is recognized as a national standard in China.
8. **WorldFIP**
Originating in Europe, WorldFIP remains independent after merging with FF in North America. It is popular in France and supports seamless integration with other fieldbus technologies like FF HSE.
9. **INTERBUS**
An early fieldbus developed by Phoenix Contact, INTERBUS is now an IEC 61158 international standard. It features reliable, real-time communication and is widely used in automotive and packaging industries.
Other notable fieldbuses include P-Net (used in agriculture and food industries) and SwiftNet (used in aerospace). Each technology has unique strengths, catering to specific industrial needs and application scenarios.
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