Design Of Control System For Halide Scintillation Crystal Growth Furnace

Scintillation crystals is a functional crystals that convert high-energy particles into light energy,which is widely used in X-ray CT imaging,security inspection and other detection fields.With the increasing demand for scintillation crystals,The ultra-low speed growth technology and the reliability of temperature control system of existing equipment cannot meet the requirements of crystal growth process,generation equipment generation material,therefore,it is of great significance to study the control technology of the scintillation crystal growth furnace to improve the crystal quality and efficiency.According to the technical indicators proposed by a domestic scientific research institution,a set of control system of halide scintillation crystal growth furnace is designed by adopting the crucible descending method.The main research contents are as follows:(1)Through the analysis of crystal growth process,a control system scheme capable of growing halide scintillation crystals is proposed,And a crucible rotating fixing device is designed to improve the coaxiality and verticality to ensure the homogenization of the melt in the crucible.(2)Aiming at the crawling problem of the scintillation crystal growth furnace pulldown device at low speed control,based on the analysis of the friction phenomenon,a variable gain control method is proposed,which uses different gain parameters to suppress the nonlinear friction interference and realizes the compensation of the lowspeed performance of the servo system.(3)As the controlled object,the temperature of the crystal growth furnace has large inertia and hysteresis.On the basis of PID control,a parameter self-tuning fuzzy PID control scheme is proposed.With the help of MATLAB simulation software,the experimental verification is carried out.The simulation results show that this method can achieve accurate temperature control quickly and effectively compared with PID.(4)The control system construction and human-machine interface interaction design have been completed,and the prototype test has been carried out according to the technical requirements of the scientific research institution.The test results show that the low-speed operation error of the crystal growth pull-down device is less than1%,and the temperature of the heating furnace is controlled to be stable at ±0.2 °C.The temperature field gradient distribution meets the requirements of crystal growth process parameters,which verifies the reliability of the system.