| Based on the brief introduction about the technical procedure of adjustable pressure casting, this paper puts forward a scheme on TY-1 adjustable pressure casting control system. In the system, the process of adjustable casting is controlled by using two modes-manual control mode and automatic control mode. With regard to the distributed computer control system, the paper gives a detailed description of the hardware structure of the measure computer and provides an application software of the measure computer system which is programmed with a graphical programming language known as LabVTEW. The software consists of data acquisition program, asynchronous serial communication program, animated process-monitoring program, reliable alarm program etc. In addition, the method of using external code in LabVIEW is elaborated. And in the 4th chapter, by the standard of RS232, the system works out and realizes a convenient communication protocol which suits the asynchronous serial communication between the measure computer and the control computer.After acquiring the rough model of the system by analyzing the work principle, the system gives the accurate mathematical models of the upper and lower system by identification method-least squares estimation, then it adopts the method of pole assignment to design classical PID controller for each system. The simulation results show that this algorithm produces a satisfied effect, so it is used on the real casting system. After that, an adjustable parameter PID controller is proposed to compensate the change of parameters in the plants. Both the two kinds of PID controllers are simulated, the comparison of the results show out that the second proposal attains a more remarkable effect. Finally, the Fuzzy -PID compound controller is presented to restrain the noise and improve the control precision of the pressure deviation and differential pressure deviation. The simulation results of the design are well met the requirement. |
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