A Study On High Precision Heating-control Method During The Process Of Super-hard Materials Synthesis

Instantaneous static or dynamic high temperature and high pressure technologyis used in the process of man-made diamond, driving carbonaceous materials such asgraphite from solid or molten directly into a diamond. In the process of graphite intodiamond, we must control pressure and temperature according to the diamondsynthetic process, and the accuracy and stability of pressure and temperatureultimately determines the quality of diamond. Since graphite is in the closed pressurecavity during the synthetic process, temperature measurement is very difficult.Nowadays cubic press is widely used in synthetic diamond, for the control of currentor power instead of control of the temperature. This paper mainly studies constantpower heating in the diamond synthetic process.But the precision, stability and anti-jamming performance of power control isnot ideal since the problems of industrial power grid volatility, load change, lowaccuracy and long period of measurement system itself during synthetic process,which directly affect the quality of diamond. For different kinds of problems of theheating system, this paper proposes a new method using digital controller instead ofanalog controller which is widely used at present. New controller can improve thesystem performance from measurement method, power control method andalgorithm, meeting the requirements of high quality diamond synthetic. This methodobtained the affirmation through the function experiment verified, softwaresimulation and field test.On the hardware design, we completed the whole circuit design of heatingcontrol system, including power module, measuring module, communication module,the zero passage detection module and SCR trigger module, which can realize thefunctions of measured signal acquisition, SCR trigger accurately, and the function ofinformation interaction.On the software design, we completed the measured signal acquisition andcalculation, voltage zero judgment, SCR trigger and the communication program design with Modbus protocol based on system hardware platform. Usingfeedforward compensation and feedback adjustment realize constant power heatingin the aspect of control. Feedforward compensation complete adjustment throughmeasuring the extent of power grid volatility, compensate the influence of powergrid volatility. Feedback system makes fuzzy self-tuning PID algorithm into thepower of negative feedback control, meeting the requirements of precision, stabilityand adaptive ability. Using Matlab to analyze the system modeling, which showedthat the stability, adaptive and anti-jamming performance of the fuzzy self-tuningPID controller were superior to traditional PID controller.On the experiment, this paper states several main experiments during the designprocess and the result of industrial field test, fully demonstrated the feasibility of thesystem. Experiments include waveform comparison on both sides of transformer,double integral AD transform, circuit testing and sampling site testing. Industrialfield test choose Henan FeiMeng diamond industrial co., LTD and XiuWu XinRuisuper hard materials co., LTD to accomplish experiments. The experimental resultsshow that the system can complete the expected design goal, significantly improvethe accuracy and stability of power control in diamond synthetic process, which havegreat significance to high quality diamond synthetic.