With the development of computer technology, communication technology, and control technology, fieldbus technology has been widely applied in industrial control systems, and has also begun to be used in the textile industry. This article introduces the basic principles of fieldbus, compares several existing fieldbuses, and, based on an analysis and summary of the new characteristics of the development of digital textile production control systems, introduces the current situation of fieldbus application in the domestic and international textile industries.
1 Introduction
With the continuous and rapid development of my country's textile industry, modern textile technology will be dominated by electronic information technology and characterized by intelligent production [1]. At present, the development of domestic textile machinery and equipment control systems focuses on realizing the automation of textile process performance of single equipment, enclosing the advanced functions of the machine in a single machine system, while ignoring the network structure of the system. As a result, the structure of the machine (especially its control system) will become more and more complex, making the machine an "island" in the automation system of textile enterprises. Since the 1990s, fieldbus technology and control systems based on this technology have attracted great attention at home and abroad, becoming a hot spot in the development of automation technology worldwide. It integrates microprocessor technology, network technology, communication technology and automatic control technology, and puts the microprocessor into the field automatic control equipment, so that the equipment has the ability of digital calculation and digital communication. It not only improves the accuracy of signal measurement, control and transmission, but also creates conditions for realizing its remote transmission.
In the process of the textile industry's transformation from traditional to modern industry, fieldbus-based control technology has provided opportunities for the development of textile industry control systems towards decentralization, networking, and intelligence. This paper introduces the basic principles of fieldbus, compares the characteristics and application scenarios of several commonly used fieldbuses, and builds a framework model of a digital textile production system based on fieldbus control technology.
2. Basic Principles of Fieldbus
Fieldbus is the intersection of the current 3C (Computer, Communication, Control) technologies, as well as the convergence of process control technology, automation instrumentation technology, and computer network technology. It is a concentrated manifestation of the development of information technology and network technology in the control field, and an inevitable result of the extension of information technology and network technology to the field.
According to the standards of the International Electrotechnical Commission (IEC) and the Fieldbus Foundation (FF), fieldbus is a digital, bidirectional, multi-branch communication network that connects intelligent field devices and automation systems [2]. Fieldbus technology incorporates dedicated microprocessors into traditional measurement and control instruments, enabling them to have digital computing and digital communication capabilities, and to become network nodes capable of independently undertaking certain detection, control, and communication tasks. A network system is formed by connecting multiple measurement and control instruments, computers, etc. as nodes through ordinary twisted-pair cables; using open and standardized communication protocols, data transmission and information sharing are realized between multiple microcomputerized measurement and control devices located at the production control site, as well as between field instruments and remote computers used for monitoring and management, forming various automatic control systems that meet actual needs.
Fieldbus is primarily designed for process control. Besides transmitting direct digital and analog signals, it can also transmit control information. The data unit for network exchange is a frame. Compared to Distributed Control Systems (DCS), Fieldbus Control Systems (FCS) offer advantages such as higher reliability, better security, interchangeability and interoperability, openness, and decentralization.
In summary, fieldbus is a real-time control communication network that interconnects the lowest-level field controllers and field intelligent instruments in automation. It follows all or part of the communication protocols of the ISO/OSI Open Systems Interconnection Reference Model.
3. Several common fieldbus technologies
Since the 1980s, major international companies have successively launched several industrial fieldbuses and field communication protocols. Currently popular protocols include FF (Fieldbus Foundation), Profibus (Process Fieldbus), CAN (Controller Area Network), LonWorks (Local Operation Network), and WorldFIP (Factory Instrumentation Protocol). Their main technical differences and applicable scenarios are as follows:
3.1 FF Fieldbus
The Foundation Fieldbus (FF) is based on the ISO/OSI Open Systems Interconnection model, taking its physical layer, data link layer, and application layer as the corresponding layers of the FF communication model, and adding a user layer on top of the application layer. FF offers two communication rates: low-speed H1 and high-speed H2. H1 has a transmission rate of 1.25 kbit/s, a communication distance of up to 1900 m (extended with repeaters), supports bus power supply, and is intrinsically safe for explosion-proof environments. H2 has two transmission rates: 1 Mbps and 2.5 kbit/s, with communication distances of 750 m and 500 m respectively. The physical transmission medium supports twisted-pair cable, fiber optic cable, and wireless transmission. The protocol conforms to the IEC 11582 standard, and the transmitted signals use Manchester encoding. It is mainly used in process automation fields, such as chemical, power, oilfield, and wastewater treatment.
3.2 Profibus Fieldbus
The Profibus series consists of three compatible parts: Profibus-DP, Profibus-FMS, and Profibus-PA. Profibus utilizes the physical and data link layers of the OSI model, forming a subset of its standard's first part. Profibus offers transmission rates from 9.6 kbit/s to 12 Mbit/s, with a maximum transmission distance of 100 m at 12 Mbit/s and 400 m at 1.5 Mbit/s, extendable to 10 km using repeaters. Transmission media can be twisted-pair cable or fiber optic cable. Key application areas include: DP type, suitable for manufacturing automation applications such as pharmaceuticals, cement, food, power, power generation, and power distribution; FMS, suitable for general manufacturing automation such as textiles, building automation, programmable logic controllers (PLCs), and low-voltage switchgear; and PA type, a bus type used for process automation.
3.3 CAN Fieldbus
CAN network design adopts a three-layer architecture model conforming to the ISO/OSI network standard model: physical layer, data link layer, and application layer. The physical and data link layer functions are performed by the CAN interface device, while the application layer functions are performed by the processor. Communication features outstanding reliability, real-time performance, and flexibility; it uses a short frame structure, resulting in short transmission time and strong interference resistance; nodes are assigned different priorities to meet varying real-time requirements. Its transmission media can include twisted-pair cable, coaxial cable, or optical fiber, with a maximum communication rate of 1 Mbit/s (40m) and a maximum direct transmission distance of 10km (5kbit/s). Major application areas include: automotive manufacturing, robotics, hydraulic systems, distributed I/O, machine tools, and medical devices.
3.4 Lonworks Fieldbus
LonWorks employs a 7-layer protocol architecture similar to the OSI reference model. The core of LonWorks technology is the Neuron chip, which integrates communication and control functions. The Neuron chip implements the complete LonTalk communication protocol for LonWorks, enabling peer-to-peer communication between nodes. LonWorks communication rates range from 78K bit/s to 1.25M bit/s, supporting various physical media including twisted-pair cable, fiber optic cable, coaxial cable, power line carrier, and wireless communication; it also supports various topologies, allowing for flexible networking. Its main application areas include industrial control, building automation, data acquisition, and SCADA systems, demonstrating superior performance in building distributed monitoring networks.
3.5 WorldFIP Fieldbus
The WorldFIP fieldbus architecture is divided into three levels: process, control, and monitoring. Its protocol consists of a physical layer, a data link layer, and an application layer. Communication rates include 31.25K bit/s, 1M bit/s, 2.5M bit/s, and 25M bit/s. Shielded twisted-pair cable and fiber optic cable are used as transmission media. It can meet various user needs and is suitable for centralized, distributed, and master/slave application structures. A single WorldFIP bus can meet the needs of process control, factory manufacturing, and various drive systems. Major application areas include: power industry, railway, transportation, industrial control, and building systems.
