Development Of Distributed Control System On Coal Powder Preparation

In order to realize the monitor and control during the raw coal hoisting, feeding, milling, powder separation, storage, weighting and feeding, a control system based on PROFIBUS-DP was developed for a new coal powder preparation line in a Iron Ore Group, Shandong. After extensive research on recent situations about Distribute Control System (DCS) in native and abroad and real needs of the project, a IPC & PLC & field-bus structure is adopted to solve the control problems, such as the complexity of the manufacturing flow, multiplicity of equipments, excessiveness and disperse of I/O and high demand of avoiding blast. In the locale, AC transducers and soft starters form the DP slaves by field-bus communication card in the field to realize the driver and control. A S7-300 PLC, which acted as a DP master and MPI slave, form the middle control layer. Besides finishing the basic logical function, it can also harmonize the work among these DP slaves and realize some special control arithmetic via field-bus communication. A ADVANTECH IPC, which acted as a MPI master, is used to display parameters, deal with alarm information, print report forms and so on.As the core equipment of the system, grinding machine is launched with soft start technique. Development on intelligent solid soft starter based on variable reactance is studied and analyzed in depth. Combining with up-to-the-minute research fruit both at home and abroad, several motor soft start methods are compared. Hardware circuit and electric connection design which takes S7-200 PLC as the main control unit is analyzed in detail. We adopt fuzzy control theory to design software which is mostly fit for limiting current start mode. According to the result of simulation, we can find the fuzzy algorithm has improved the control effectiveness and dynamic and the reliability of system.The coal powder preparation distributed control system has been put into practical use. This system, which can provide preferable references for the designs of other preparation control systems, proves to be steady and easy to operate. It can improve the productivity and the quality of production as well.