| Qinghai Salt Lake Co.Ltd is the largest production base of potash in China, their potash production line adopts the reverse-flotation & cold-crystallization process. Reverse-flotation is the core process to improve the quality of products and productive efficiency in potash production, so it’s necessary to achieve the high-precision control the important devices and key objects.The background of this paper is the new million tons potash production project of Qinghai Salt Lake Co.Ltd, and the reverse-flotation process is the main object. A dual CPU redundancy control system based on Rockwell PLC and three-layer networks is designed. The system builds on the Rockwell three-layer nets architecture. In the control layer, Rockwell ControlLogix platform is the cardinal controller, the control programs are compiled in RSLogix5000 software; in the device layer, the centralized control of Low-voltage electrical devices uses the Motor Control Center (MCC). VFD, E3 Plus Relay and SMC soft starter are the three kinds of control units; PC monitoring system is designed in the FactoryTalk View SE configuration software in the information layer.The control strategies of flotation reagent are researched deeply. After simulative researches about PID control strategy which is adopted in the site, the deficiencies of PID control strategies are obtained and an improved project, fuzzy predictive control algorithm is proposed. The simulation results certify that the FPC strategy can solve the problems of delay part, modeling imprecision and vulnerability, it also can get better dynamic characteristic and robustness. The FPC strategy offers a new project for further optimization of the system.The trial operation results show that the control system has high reliability, strong stability, accurate control effect, outstanding man-machine interaction and good openness as well as extensibility, which can fulfill the control demands of the industrial site. It has a certain value to promote. |
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