| Pattern drawing machine is a key equipment used in the process of resin sand molding. It is used for separating the pattern from the sand mould, and this process directly influences the quality of molding sand. The machine is widely used in the casting industry because of the scientific working principle and easy to operate. There are only a few factories have the capacity to produce the machine in China. And the equipments at present have the shortcomings such as the irrational structure and the low drive accuracy, that will destroy sand mould, reduce production efficiency. Based on the main problems of low accuracy and efficiency, the working principle and process characteristic was studied in detail. Second, the hydraulic system by using the technology of electro-hydraulic proportion synchronous control was designed. Then a further study on the feature of the system of synchronous driving during drawing and the nonlinear modeling were presented. According to the actual working conditions, the control strategy of fuzzy PID control was adopted. Then the simulation and experiment results were analized. Finally, the electric system base on PLC was presented.The work of this paper is shown as follows:In Chapter1, first, the development history of the rollover pattern drawing machine was introduced. Then the present researches and applications of electro-hydraulic synchronous driving technology and hydraulic control technology were analyzed. By consulting a number of documents, the present status and directions of the key researchs on the development of electro-hydraulic system were summarized.The general design of electro-hydraulic system was discussed in Chapter2. First, the mechanical structure was put forward and emphasizes on analyzing the processing technological feature. Then the hydraulic system which adopted the electro-hydraulic proportion control technology was designed, and the corresponding types of hydraulic components were slected.In Chapter3, the mold that electro-hydraulic proportion closed loop control was used to realize the double cylinders synchronization drive. Then the mathematical model of electro-hydraulic system of double cylinders drawing synchronization driving was established according to the foundation of the analysis of asymmetric hydraulic cylinder with asymmetric valve. That lay the foundation of the following simulation experiment analysis and the control strategy through the corresponding parameters given in the mathematical model.In Chapter4, the research on the position control of electro-hydraulic system was stated. The actual working conditions of the system analyzed and the strategy of "two-step" fuzzy PID was put forward to realize the synchronization of double cylinders. The results of simulation and actual application show that the proposed control strategy can reach a considerable control effct. It improved the dynamic performance of system and meet the design requirements. The effct was better both on the single cylinder position tracking and double cylinders synchronization control under fuzzy-PID than that of the convetional PID.In Chapter5, the electric control system of the machine was designed. First, based on Siemens S7-300PLC system, the principle of electro-hydraulic control system and the control method for the whole machine was given.Then the type slection of hardware, the design of lower computer control software and the upper computer software were introduced.In Chapter6, the work of developing the electro-hydraulic control system of the rollover pattern drawing machine was summarized, it meet the design index basically. And then the prospect of the research to improve in the future was presented. |
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