Research And Design Of Control System In Fermentation Process Of Marine Biologic Enzyme

The study about marine biologic enzyme, one of the National 863 Programs, has been finished by Yellow Sea Fisheries Research Institute Chinese Academy of Fishery Sciences. Actual qualification tests have indicated that marine biologic enzyme addition agent is very advantageous to the growth of marine fish. But low automatic level of equipments has been the biggest obstacle in the product industrialization process.This thesis talks about the research and design of control system in fermentation process of marine biologic enzyme. PLC S7-315-2DP of SIEMENS is adopted as a main station of the system which plays an important part in system control. It deals with various data and flow of technique. Three OP270 operator panels, as the second main stations of the system, can be used by workers to monitor system. By using ET200M, a kind of long-distance I/O module, I/O devices can enter the nearest substation, so it is convenient to connection and debugging. MM440 is the variable-frequency equipment which has perfect communication function. By connecting with PROFIBUS board, we can get PROFIBUS-DP substation. It responds to the commands of the main station real time and controls devices directly. At the same time, it monitors and returns running state of the machine. The CP342-5 communications processor, as the intermediate repeater of the PROFIBUS-DP network, can be used to reduce the communication tasks of the main station.In the fermentation process, the concentration of dissolved oxygen in the fermentation fluid is an extremely important fermentation parameter. It affects not only the growth of the cells, but also the formation of the product. There are several variables in the system which can affect each other, so it is very difficult to find the accurate mathematic model of the system. As a result, the conventional method is not fit for the dissolved oxygen control system. Considering the reasons above, we introduce fuzzy control in this paper, choose the stirring rate and the air flow rate as the control variables, and build up a two-input-two-output fuzzy control system. It is proved to be a good method.This thesis not only analysis the design and configuration, but also introduces general situation of PROFIBUS and the basic character of PROFIBUS-DP.