1. Characteristics of hydraulic system failure
The hydraulic system of engineering machinery mainly includes hydraulic pump, torque converter, control valve, hydraulic motor and hydraulic cylinder (actuator), transmission, power shift transmission valve and other mechanisms. The failure of the hydraulic system is generally manifested by the weakness, delay, vibration or overheating of the walking and actuator, the poor coupling of the hydraulic clutch and the inflexibility of the hydraulic piston. . The main reason for the failure is caused by the failure of the hydraulic system or components. This failure is often manifested by changes in pressure, flow and temperature of the hydraulic system. The fault characteristics of hydraulic system of construction machinery have the following 5 characteristics:
One is that the fault point is strong concealment. The failure of the hydraulic equipment of the engineering machinery often occurs inside the system, and the inspection conditions of the work site are poor, so it is difficult to detect directly, and it is difficult to analyze and judge the fault.
Two, the fault diagnosis of the hydraulic system is complicated. The relationship between the fault performance of the hydraulic system of the engineering machinery and the fault point is more complicated. A fault phenomenon may be caused by a number of fault points. A fault symptom may be caused by many reasons, and a fault source may also cause multiple hydraulic symptoms.
The three is the strong randomness of the related factors. In the working process, the hydraulic system of engineering machinery is often affected by many factors, and the occurrence and development of the fault often have uncertainty. Therefore, it is difficult to judge and analyze it quantitatively.
The four is the dispersion of the failure distribution. Due to differences in design, materials, processing and working environment greatly, the wear rate of different hydraulic components caused by the large engineering machinery, the so-called "hydraulic element life standard" in such a complex case only as a reference, but not as the main basis of hydraulic component fault diagnosis and analysis.
The five is the mechanical and liquid coupling difference. Engineering machinery is often a comprehensive system of mechanical, electronic and hydraulic devices. Its failure is often the complex coupling of the subsystems, which makes the fault monitoring and diagnosis of the hydraulic components very difficult.
2. Classification of fault monitoring and diagnosis technology
The hydraulic system fault monitoring and diagnosis of the engineering machinery is to use modern scientific and technological means and equipment, to detect the oil state, speed, noise and leakage condition of the hydraulic motor and hydraulic cylinder, such as the basic parameters of temperature, pressure, flow and so on in the hydraulic system, as well as the hydraulic motor and hydraulic cylinder and so on, to judge the hydraulic pressure synthetically. The working state of the system and the working condition and damage condition of the hydraulic components are deduced.
According to the different objects, there are 2 main kinds of fault monitoring and diagnosis technology in the hydraulic system of engineering machinery, one is to monitor and diagnose the oil pollution, and the two is to monitor and diagnose the hydraulic system. In the working process of the hydraulic system of the engineering machinery, local oil leakage often occurs, causing the local oil pollution in the hydraulic system of the engineering machinery, affecting the efficiency of the system and even causing the failure. Through the monitoring of the oil contamination of the hydraulic system of the construction machinery, the fault can be diagnosed.
The realization of different functions of the hydraulic system of engineering machinery needs multiple hydraulic components to cooperate with each other. If one or more components fail in the working process, it is bound to affect the work of the hydraulic system of the construction machinery. Through the monitoring and diagnosis of the hydraulic device by fault monitoring and diagnosis technology, the problems of the hydraulic system in the construction machinery can be found in time and processed in time, so as to ensure the reliability of the operation of the hydraulic system of the construction machinery.
Once the hydraulic system of the construction machinery fails, the on-site staff can take the following methods to lock down the fault points and eliminate the problems in time. One is the observation method. The observation method is the most convenient method. The staff can check the parts of the hydraulic system of the engineering machinery by listening, smelling, touching and looking. The difference between the normal noise and the fault noise of the working system, as well as the oil taste, vibration, temperature, color change, etc., can be used to judge such as deformation, loosening, oil leakage, rupture and so on. Failure. The observation method is simple and reliable, especially when the necessary tools and instruments are applied to the job site. The two is to diagnose by operation and adjustment. When there are problems in the hydraulic system of the engineering machinery, the staff of the working experience can judge the types and parts of the fault by the operation and adjustment of the equipment through the equipment and the normal working conditions. This diagnostic method can be carried out without load, but requires higher skills for the staff. The three is the contrast or replacement examination. The fault points can be judged by the comparison of the working state of the 2 same equipment or the replacement of the suspected fault hydraulic components in the failure of the hydraulic system of the engineering machinery and the lack of the testing instruments and professional technicians. The use of this method is more direct, but it is often limited by the fact that the same equipment is not found and the disassembly is inconvenient.
3. Status of fault monitoring and diagnosis technology
(1) the status of foreign countries
Many foreign organizations represented by developed countries in Europe and America have done a lot of research on the informatization and intellectualization of construction machinery, and have put them into practice. For example, a brand has installed GIS geographic information system, GPS global positioning system, GSM global mobile communication system and METS mining shovel soil transportation system on many engineering machinery. METS is mainly composed of 3 parts: CAES (computer aided earth shovel transportation system), VMS (key information management system) and CAESoffice (CAES proprietary office system). It has the functions of radio communication, equipment detection, fault warning and diagnosis, operation management and mechanical automation control.
The F series and G series of loaders developed by a company in 1990s have all installed CMS (computer monitoring system), which replaced the EMS (electronic monitoring system) of the previous generation of the E series. The electronic computer system of F series and G series loader can monitor the fuel quantity, water temperature, transmission temperature and hydraulic oil temperature at the same time. At the same time, the system has the function of fault diagnosis, and can provide three levels of alarm. The computer system, which is carried on a engineering machine, can monitor and diagnose the parameters of the loader and transmit the data to the office for record and analysis by wireless transmission. The computer monitoring and diagnosis system provided by a construction machinery provides guidance and diagnosis system and software package based on maintenance tools. The installation of a engineering machine has VMS (key information management system), which further strengthens its monitoring and fault diagnosis system, and can display the error information and fault causes on the LCD screen by LeTourneau (integrated network control system). At the same time, he also provides a three level alarm signal to display the engine, hydraulic system and electrical electronics. The state of a system, etc. The L series loader produced by a company has also installed Matris software based on computer technology to monitor and analyze the working state of the key systems such as the engine and hydraulic system of the loader, and provide human-computer interaction and automatic fault diagnosis and display.
(2) domestic status
Comparatively speaking, China's engineering machinery fault detection and diagnosis technology is lagging behind. Since twenty-first Century, many domestic research institutes have increased theoretical research and practical exploration on electronic monitoring, fault monitoring and diagnosis of construction machinery. For example, He Lingsong and Yang Shuzi of Huazhong University of Science and Technology combed the domestic and foreign research status and key technical problems of remote diagnosis of equipment fault based on Internet, and Xing Songyin of Harbin Institute of Technology introduced CSCW (computer supported synergy) from the development background, concept connotation, key technology, application prospect and development trend. Work) in the field of fault monitoring and diagnosis for construction machinery.
In order to improve the reliability of the engineering machinery, the domestic engineering machinery design and manufacturing enterprise began to try and develop the electronic monitoring and control system of the engineering machinery to monitor and record the operating state of the engineering machinery, and to provide the fault diagnosis and remote control based on the computer and Internet technology with the function of preliminary fault monitoring and diagnosis. Service system. Installation of engineering machinery with this system, no matter in any place in the world, as long as the user has opened a remote service system, the manufacturer's experts can monitor the working state of the engineering machinery at any time, and provide the consultation and troubleshooting (consultation) service of the fault machinery. The intelligent construction machinery remote monitoring platform based on GPS, GPRS (wireless communication technology) and GIS (Geographic Information Technology) developed by a domestic enterprise has been widely used in the company's positive flow hydraulic excavator and other products, and its performance index has reached the international leveling of the same period.
4, the future development trend
With the continuous development of mechatronic and hydraulic integration technology, computer and data processing technology, network and communication technology gradually merge, the fault detection and diagnosis technology of the hydraulic system of engineering machinery is developing from the simple subjective analysis to the new direction, mainly in the following aspects.
(1) virtualization
With the continuous development of computer technology, its related software technology and microelectronic technology are constantly being updated. As a new technology, virtual instrument technology has been gradually applied to all kinds of construction machinery. This technology is flexible and open, the development environment is friendly, users can make some changes to the software, and some new functions can be realized.
(2) high precision
For the hydraulic system of engineering machinery, the signal is often nonlinear, abrupt and transient, so the traditional time domain and frequency domain only apply to the analysis of steady state signal, and the fault information can not be revealed. This requires a method that can simultaneously display signal in time and frequency domain. The continuous development of computer technology and big data technology can meet this requirement and greatly improve the resolution of signal processing.
(3) state
The sensor technology, computer technology, infrared temperature measurement technology and ultrasonic technology are introduced into the field of monitoring and diagnosis of the hydraulic system of engineering machinery. It can effectively solve the tracking problems of the time difference flow signal and pressure signal produced by the flow, pressure and noise of the liquid flowing through the pipeline. The dynamic system of hydraulic system can be realized. The on-line real-time monitoring of parameters avoids the problem of "disintegration physical examination" of the hydraulic system of the engineering machinery, thus effectively solving the contradiction between "insufficient maintenance" and "overmaintenance".
(4) intelligentization
The application of artificial intelligence technology, such as knowledge engineering, expert system and artificial neural network, in the field of monitoring and diagnosis of hydraulic system of engineering machinery, can solve the problem of serious dependence on practical experience of fault diagnosis because of the concealment, diversity and complicated causes of the hydraulic system.
(5) networking
The structure of modern engineering machinery hydraulic system is becoming more and more complex, and the professionalism is becoming stronger and stronger. This requires the equipment experts to be able to intervene the fault detection and diagnosis in time. The liquidity of engineering machinery is strong, and the equipment manufacturers often can not send experts in time to solve the problem in time. Therefore, the establishment of real-time online measurement and fault diagnosis system based on the Internet will be an inevitable choice for the monitoring and diagnosis of the hydraulic system of the engineering machinery.
