The Research Of Electrical Control System In Compulsory-Asphalt-Mixing Station

With the rapid development of microelectronic technology, PLC products have been greatly enriched and improved in their functionality and performance indicators, which lay the foundation of series of advanced-control and technology innovation. Combining with the fundamental principle and technical features of closed-loop control and PLC technology, the thesis analyzes and studies the electrical control of compulsory asphalt mixing station deeply based on analyzing and summarizing process characteristics and control requirements. According with some special model of S7-300 PLC, the thesis designs closed -loop control for compulsory asphalt mixing station, and introduces the field bus PROFIBUS-DP timely. The main content of this thesis is shown as follows:1. The thesis analyzes the inadequacy of the original control system, and finds such problems as asphalt measurement accuracy is low caused by utilizing the second measurement, stone temperature uses single closed-loop control which causes high temperature fluctuations and slow response, PC does not have the OPC communication interface which causes the system's poor expansibility, amount of wiring brings the increase of cost and the difficulties about maintenance and troubleshoot.2. The thesis uses SIMATIC S7-300 PLC as the main controller, utilizes Ethernet and field bus for communication of itself and host computer and the distribution of I / O respectively. The thesis uses Reduce-Measurement as asphalt measurement approach and uses the concatenate to control the temperature of stone.3. The thesis describes hardware configuration, software develop procedures and the realization of the circuits, such as start and stop of motor control circuit and its application procedure, production control procedure diagram and hardware configuration schematic.4. Finally, the thesis introduces the monitoring system which uses FAMEVIEW V7.5.1 configuration software as development tools to monitor and control the compulsory asphalt mixing station.In addition, the thesis also analyzes the application effectiveness of closed-loop control and the SIMATIC S7-300 PLC technology in the work process of the compulsory asphalt mixing station. Practice shows that this control system has stable running and reliable control, and various technical indicators reaches theinternational high-class product indicators after implementation of the controlprogram.