Study On Soft-sensor Technology And Inferential Control Of Temperature In Isothermal Forging

The isothermal forging is a kind of special forging method which was developed in the last years. Which control the mould temperature similar to the workpiece temperature and make the workpiece finish the forging process on the condition of keeping constant. Thus, in isothermal forging process, it is important to measure and control the temperature. However, the temperature of workpiece can not be measured directly because of the closeness of mould which due to the deformed workpiece be enclosed in the mould entirely. To cope with this problem, this paper propose that adapt FEM numeral simulation technique to simulate the isothermal forging process of TC4 alloy, and obtain the distribution of temperature of workpiece and mould, further more, gain the temperature sensitive point of mould;and establish the temperature soft sensor model by the mechanism method, regression method and neural network method;lastly, apply virtual instrument technique and adapt inference control method based on soft sensor control the changes of temperature on workpiece ' sensitive points. The main research finding and new outlooks are as follow:According to the forming characteristic of TC4 alloy, this paper employs the numeral simulation technique to simulate the isothermal forging process and analyze the influence of temperature on the workpiece, mould and equipment in the process of isothermal forging, but also find out the workpiece sensitive points through the distribution of temperature. In consideration of the practical production conditions and character of deforming, we decide that the isothermal forging temperature is 950°C or so.Research on the transfer law of temperature signals from die to workpiece in isothermal forging process and find the relationship between mould temperature and workpiece temperature. Then establish workpiece temperature soft sensor model by mechanism method, regression method and neural network method. Comparison of three models, find that the approaching effectiveness of neural network method is the best of all and is used ultimately.This paper design and fabricate an array thermocouple sensor and connect eight thermocouples by the way of series and shunt. In this way, the array sensors canincrease the measurement precision and sensibility in some way.Base on soft sensor method of workpiece temperature, this paper adapt a new controlling method which called inferential control method to control the workpiece temperature in isothermal forging;then use the VI technical, design a measure and control VI system by use of LabVIEW, which can solve problem that temperature can not measure on line, and increase the reliability of the controlling system.