| In recent years, some epidemics have outbreak all around the world, such as SARS in 2003, H5N1 strain in 2005, H1N1 influenza in 2009, H7N9 influenza in 2013 and Ebola hemorrhagic fever in Africa started from 2014, threatening the health and life of human seriously and impacting the politics and economy of the world greatly. China is a country with the vast territory, the huge population, the complicated geographical environment and the frequent international communication, and occasional emerging or burst epidemics make the situation of disease prevention and control we faced even grimmer. Consequently, biosafety issues begin to arouse attention and accelerate the development and popularization of biosafety equipment, especially mobile biosafety equipment.The mobile biosafety shelter(MBS) is a kind of medical platform for biological sample, testing, analysis and the treatment or transport of patients under field conditions, such as biological reconnaissance vehicle, biological test vehicle, bio-control/infectious ambulance and mobile biosafety laboratory, which can acquire, grow, and inspect the suspected pathogen in the bio-contaminated areas, complete the emergency treatment or transport of the wounded or infectious victims, and quarantine the source of pollution and infection, reducing cross-infection.High efficiency particulate air(HEPA) filters and negative pressure gradient control are the two technical measures to achieve bio-safety and isolation protection. The negative pressure gradient control system(also called as electrical system) can hold a stable pressure, temperature and humidity to provide an effective protection for medical staff, which could be affected by the good condition of its equipment. Once the fault occurs, airflow will have no particular direction, which might lead to the proliferation of pathogenic microorganisms, endangering the lives of staff and surrounding populations, even causing serious social panic. Unlike fixed bio-safety laboratory, MBS lacks support forces for the harsh working environment, and it is hard to operate conventional equipment inspection and routine maintenance for the limited space. Therefore, the research of fault diagnosis for electrical system that can improve MBS intelligent level, decrease equipment failure rate, reduced maintenance costs, shorten maintenance time, and ensure the normal operation of MBS has a very important practical significance.This paper studied the fault and fault diagnose of electrical system in MBS. The main contents are as follows:(1) Fault formation mechanism of electrical system of MBS is studied. Select one type of mobile BSL-3 as the research subject and analyze its structure and work flows. The mobile BSL-3 is composed of the main laboratory shelter(main shelter) and human cleaning and technology support shelter(assistant shelter), which have respective negative pressure control systems. Negative pressure control devices include inflatable gate, electrical valve, VAV valve, pressure switch, pressure sensors, three-phase centrifugal fan, inverter, PLC and so on, which can be divided by function into air supply subsystem, exhaust subsystem, process control subsystem and gating subsystem, and all devices are controlled by IPC through the RS485 bus connection. Fault alarm preinstalled in the system can only prompt the fault type but the fault reason. This paper analyzes and summarizes the fault symptoms and reasons of MBS by drawing from the troubleshooting of other mobile medical platforms, vehicle embedded devices, fixed bio-safety laboratories and HVAC, and find that some faults symptoms have a complex and fuzzy non-linear mapping, making it difficult to judge the electrical system fault and evaluated its severity.(2) The fault diagnosis strategy of electrical system is summarized. The failures of electrical system are divided into hard faults and soft faults according to the extent of impact on the system. This paper complete the diagnostic description about some hard faults like power supply and air conditioning, summarize the basic change rules of parameter, the relationship between the soft fault symptoms and reasons by experiment, and generalized a pacific method to explain the variation of pressure using the difference among air volume Q, providing a fault diagnosis reference for similar equipment.(3) A method using Mamdani type fuzzy inference algorithm to diagnose the soft fault of electrical system is presented. According to the characteristic information and troubleshooting equipment of electrical system, take the main cabin as an example, select the blower front and behind pressure, exhaust fan pressure, main laboratory modules pressure, airlock modules pressure, protective clothing modules pressure, output frequency of blower inverter and the output frequency of exhaust inverter as input variables, and divide the parameters into high, normal, low three levels, which are fuzzificated with S-shaped function, Gaussian function and Z-shaped function respectively. Then, establish thirteen fuzzy inference rules based on the parameters’ change, which can identify 8 kinds of faults, such as loose of blower’s electronic value, fans aging, inverter’s abnormal output, leakage and VAV’s abnormal value.(4) An experimentally electrical system using the CAN bus to connect each device is designed. Considering the disadvantage of distributed control system and the characteristics and requirements of MBS, to facilitate the maintenance, upgrade and extension in the future, this paper put forward an electrical system solution of devices connection using CAN bus to replace RS485. Each equipment is an independent node of the CAN network, and cannot be affected by other nodes’ damage, which makes it easy to troubleshoot and replace faulty equipment quickly. Fault diagnosis equipment can also connect to the CAN network easily, monitoring and evaluating the status of electrical system. CAN interface card and PC is selected as hardware of fault diagnosis system and Lab VIEW as the programming language to design the status monitoring and fault analysis program. The fault diagnosis system can record the status of devices and all pressures institution,, provide the real-time presentation using lights and curves, and use forenamed methods to determine whether a fault occurs.This research can improve the capability of fault diagnosis of MBS, and contribute to fault diagnosis of other biosafety device. |
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