The Research On The Application Of Field Bus In Medical Technology Vehicle And Shelter

Medical vehicle equipped with medical instruments and equipments, it accomplishes medical treatment and realize function. The microenvironment in the medical vehicle's shelter is very important for the wounded and doctors. The microenvironment should be controlled in temperature, air pressure and humidity so that the wounded have a better environment and the doctors keep a better efficiency. In addition, in some special medical vehicle's shelter, such as the blood vehicle, the temperature should be supervised rigorously to ensure the quality of the blood.Today ,the medical equipment of the PLA is developing rapidly, and the informationization has achieved a high level. The kinds of medical vehicle become more and more abundant, and the function advanced. Especially in the microenvironment, the standard is extremely rigorous and the capacity of communication and the number of supervised parameters as temperature, air pressure and so on is very large. There are many disadvantages like complex routing, low system reliability and difficult maintenance etc. If the microenvironment supervision system uses the traditional DCS(Distributed Control System) technology.FCS( Fieldbus Control System ) technology brings a revolution to the field of automatization control. Many Fieldbus protocols are applied in different automatization control fields. Hundreds of large multinational corporations have developed their own production, and the new technology has been popularized in our country, too. The Fieldbus technology has a expansive developing perspective. Using the Fieldbus technology in microenvironment supervision system can decrease routing, strengthen system reliability and convenience maintenance, it will improve the informationization level for our military's medical equipment.According to some standard about the shelter microenvironmentin the national Standards and the national military Standards,CAN bus and ProFibus were chosen from all kinds of buses. The two were more popular in current market and more successful in technology. Then the microenvironment supervision system was set up respectively and the supervision software was developed to achieve the real-time supervision of the temperature, air pressure and humidity inside the medical technology vehicle to make people in shelter feel more comfortable. Besides real-time supervision and control, the software also had the functions of trendline display, database management, chart print and alert. Furthermore, the system could be extended easily. It was convenient to increase node and communicate with the equipment which has RS-485 interface.In the hardware, firstly sensors and actuators were chosen for designing signal collection circuits. To get a better anti-disturbing ability and satisfied the precision and range of supervision and control. Then the instruments of field bus were selected,including communication clip which communicated with the mainframe, supervision and control, communication ports and so on. Finally, the system was configurated and the communication's address was set to make the mainframe easy-management for each instrument. The CAN node was designed for communicating with the supervision and control system conveniently.In the shelter microenvironment supervision and control software design,firstly the driver were set up in the mainframe.Then the language of VB and LD was used to design the application software. Meanwhile the VBA technology was used to accomplish the development and management of database. Finally the whole SCADA(Supervisor Control And Data Acqusition)system was founded. In this process there were eight technical difficulties have been solved as follows:The first was the transform of sampling data. The collected data is usually numerical value of voltage. To be displayed ,it should be transformed into numerical value of temperature or pressure.The second was the method of history data record.There were two methods to record metamorphic history data into the database.One method based periodical sampling. When it ran on one second or a decimus second the data was recorded quickly. Another method base on data change.When the collected data changed one or 10%,the time should be recorded immediately. The rates of numerical value to time in two methods were different,so the numbers of record were different.When the real-time data changed fast,the number of record in method based periodical sampling would be less.When the real-time data change slowly,the number of record in method depending data change was less. Choosing specified methods on different conditions could decrease the number of record.The third was fuzzy control arithmetic. By the fuzzy control method the air-condition could be controlled automatically to adjust the shelter's temperature invariable ,and the people could feel more comfortably.The forth was the drawing of real-time trendline. There were two methods as follows. First, functions were programmed using the painting control of VB to paint the real-time trendline. Second, Applying the technology of DDE(Dynamic Data Exchange) to communicate VB with matlab for painting the real-time trendline.The fifth was the development and storage of database.VBA(Visual Basic For Application) technology was used to found an Access database, which recorded the real-time data and managed them. When the period of supervision and control was long, the data recorded by database was numerous. The arithmetic of Swinging Door could compress the database efficiently. It could record more data on the same condition,but it didn't affect reviewing data and analysing the database.The sixth was the design of system's reliability.The method of redundance was used to creat two communication channels.If one didn't work,the other could replace it.It guarantees one channel working in any time.The system's reliability was increased.The seventh was the design of net node.PIC18F458 was used to design a net node. Besides A/D transform, series interface and timer, it also had a CAN module. So it could communicate with CAN bus system conveniently to accomplish the function of signal sending and receiving, A/D transforming and PWM(Pulse-Width Modulation).The flexibility of system could be increased.The eighth was the design of gateway. At present many apparatus and instruments applying RS-485 protocol to communicate with each other. But they can't communicate with Field bus. A gateway communicate between Field bus and RS-485 by PLC program was designed to make the appearances and instruments with RS-485 protocol into Field bus system. So the range of application in Field bus was extended.Basing on the test and examination, the supervision and control system for shelter microenvironment of Medical vehicle are developed in Field bus. It could supervise and control the microenvironment well. The system's informationization and reliability could satisfy the requirement. The field bus could develop our military's medical equipment.