Equipment, as a crucial manifestation and material carrier of military combat capability, is widely used in combat operations and other related military activities, and is numerous and diverse in model. This very characteristic of equipment underscores the importance of safety in equipment support, particularly the normal and effective operation of monitoring systems. It can be said that numerous accidents in recent years, including the recent "Jilin Chemical Plant incident," have served as a stark warning about potential safety hazards in our equipment operations. Therefore, the reliable operation of our military's equipment systems and the establishment of a robust safety monitoring system are of paramount importance.
1. Overview of Equipment Monitoring System
Equipment monitoring systems are a general term for equipment used to monitor and control operating machinery, including the monitoring and control of special equipment such as main unit monitoring, auxiliary unit monitoring, and power plant monitoring.
Monitoring and control systems based on microcomputers (including single-chip microcomputers) originated in the 1970s. After 20 years of development, the technology has matured and its applications are widespread. It has many advantages, such as significantly improved integration, low power consumption, and high levels of intelligence and automation. However, it also has disadvantages: a wide variety of systems and low standardization. For example, there are dozens of different models of computer monitoring systems for main battle equipment in the army, resulting in poor interchangeability. Furthermore, various factors related to design, manufacturing, management, and use contribute to some issues regarding the reliability and maintainability of these systems.
In the 1990s, international equipment monitoring systems rapidly developed into a fully digital, fully networked monitoring system based on fieldbus technology. This technology is a highly reliable general-purpose industrial monitoring technology. It is an effective combination of computer network technology and embedded electronic technology, and has advantages that past systems could not match. It is simple, reliable, and very powerful, and will be the main development trend in the field of industrial monitoring for a considerable period of time to come.
2. Fully digital, fully networked equipment monitoring system based on fieldbus technology
With the expanding application of computer technology in industrial control and the increasing demand and trend towards standardization of distributed control products, fieldbus technology has developed rapidly in recent years. It comprehensively integrates control, computer, and communication technologies, characterized by high reliability, stable performance, strong anti-interference capabilities, and low maintenance and system expansion costs. Systems built using fieldbus technology offer a high performance-to-price ratio and have been widely adopted in Europe and America. Several mainstream fieldbus standards, such as PROFIBUS, FF, and CAN, have become national or continental standards. Many major PLC and smart instrument manufacturers worldwide have launched products that support some mainstream fieldbus standard.
The core technologies of fieldbus technology are twofold:
(1) In a monitoring system, there are only 4 lines connecting the system to the system and the component to the component. Two of them are used for power supply and two are used for information transmission. The information transmission adopts serial encoding.
(2) All information in the entire system is digital.
Thanks to the two core technologies mentioned above, along with modern and sophisticated integrated circuit manufacturing processes, the system boasts extremely high reliability and a remarkably simple system structure. In fieldbus technology application systems, regardless of the amount or complexity of information from the control station to the monitored object, whether it's a single object (e.g., controlling only one motor) or multiple objects (e.g., monitoring and controlling four generator sets in a power station), only four lines connect the control station to the monitored object. A CAN bus circuit board is simply placed next to each object, allowing the control station to monitor and control it. The CAN bus circuit board, actuators, and monitoring software differ for different objects. Throughout the system, all information is transmitted digitally, and digital sensors can be used. Digital signals do not drift or introduce errors during processing and transmission, absolutely guaranteeing the system's accuracy and performance.
In a control system, there are a large amount of completely different information, such as temperature, pressure, speed, main unit start, main unit forward and reverse, etc. All of these are encoded and sent to the CAN bus through the CAN bus interface board, or received from the CAN bus interface board, decoded and processed accordingly.
CAN (Content-Oriented Communication) fieldbus technology, also known as fully distributed and fully digital technology, is a new technology that flourished internationally in the 1990s and is poised for widespread application in industrial control and automation across various fields in the next century. Essentially, fieldbus is a fully distributed, fully digital, intelligent, bidirectional, multi-variable, multi-point, and multi-station network communication system between field-controlled objects (instruments, machinery, etc.) and control stations. Its characteristics include:
(1) High reliability and simple structure. From the overall structure of CAN, all sensors, actuators, displays and computers of the system are intelligent, digital and modular, and all are connected to a four-core line (two cores are used to transmit encoded information and two cores are used to power all components on the CAN bus), without any other connections, and each module works independently.
The digital chips used on the CAN bus have a very high degree of integration and extremely low power consumption. For example, the 12PA6 main unit remote control system, after adopting CAN technology, consumes only a few dozen watts. The number of circuit boards using CAN bus technology is reduced by an order of magnitude compared to the previous parallel system. For instance, a power plant monitoring system previously used a centralized parallel acquisition system with 38 circuit boards for monitoring four generator sets. After being modified by military academies using CAN technology, the four generator sets only have five circuit boards.
CAN bus technology employs fully digital technology, maintaining consistent accuracy throughout its lifespan, significantly reducing system debugging and equipment maintenance workload. In system layout, CAN bus can utilize double-layer ring cabling, ensuring that interruptions at any two points will not affect system operation. Furthermore, opto-isolation eliminates the risk of network cable short circuits.
As seen above, due to the many advantages of CAN bus technology, it is a highly reliable and simple high-tech system, making it very suitable for equipment monitoring systems.
(2) High degree of standardization and modularization. Because CAN bus technology has internationally unified standards and has a simple structure, CAN technology application systems are easy to standardize and modularize.
(3) The system structure is simple and easy to maintain. The number and variety of circuit boards are greatly reduced, thereby reducing the amount of maintenance required for the system. The four-core wire system structure makes it very easy for maintenance personnel to perform maintenance.
3. Design and Application of Equipment Monitoring System Based on Fieldbus Technology
A power station in an equipment warehouse has four MWM234 diesel generator sets (three main generators and one auxiliary generator). Each diesel engine has 13 monitored parameters: speed, exhaust temperature, lubricating oil pressure, lubricating oil temperature, outlet coolant temperature, battery voltage, power, current, voltage, frequency, main switch on/off status, reverse power, and generator internal temperature. The basic structure of the power station's monitoring system is as follows: each generator set has a data acquisition box next to it. Data from these boxes is transmitted to a host computer via a two-core network cable. There are four identical data acquisition boxes for all four generator sets. The four generator sets are connected to the host computer in the control room via only one two-core cable, making the structure extremely simple. The host computer collects the information from the generator set data acquisition boxes via the two-core network cable and processes, displays, prints, and generates alarms.
4. Hardware Components
The monitoring system mainly consists of a local data acquisition box and a host computer. The local data acquisition box has a highly integrated circuit board that integrates signal conditioning (filtering and amplification), AD conversion, sampling processing, and communication functions. The chips on the board use the latest international analog-to-digital circuits from the 1990s, making it powerful, small in size, low in power consumption, and highly reliable.
The CAN bus interface uses the PCX82C200 chip. The communication medium (communication line) uses ordinary cable, with no special requirements, making on-site installation and construction very convenient. Each data acquisition box is responsible for processing all data from one diesel generator. After sampling, the data is sent to the host computer via the CAN bus. Each acquisition box contains only one circuit board, measuring 200×150mm, with a power consumption of approximately 5W.
5. Software Components
The software consists of three main parts: data acquisition software, communication software, and human-computer interface software.
(1) Acquisition Software: This software is a fixed program stored in the 27256 and placed on the circuit board in the acquisition box. Its task is to complete signal channel switching, amplification, AD conversion, sampling, digital filtering, linearization processing, scaling transformation, etc. This software is composed of 8031 assembly language.
(2) Communication software: It is embedded in the same 27256 as the acquisition software. Its task is to conduct network communication of the acquired and processed data according to the CAN bus rules.
(3) Human-machine interface software: This software is stored on the hard drive of the host computer (486, 586 computer). This software consists of display, alarm, printing and other modules. It completes the Chinese character display, Chinese character printing, alarm and human-machine dialogue of the diesel generator data sent by the acquisition box. This software is written in C language and the display and printing have been localized, which beautifies the screen and facilitates operation.
Distributed monitoring systems based on fieldbus not only save a lot of cable and laying costs, but also make debugging and maintenance simple and convenient, greatly improving the practicality and reliability of the system, while also reducing project costs.
