Design Of Temperature Control System For PCD Tools High Frequency Induction Brazing

With the increasing proportion of precision finishing and ultra-precision finishing in the field of mechanical processing and difficult-to-cut materials.Polycrystalline diamond(PCD)tools have been widely used due to their high hardness,good abrasion resistance and low coefficient of thermal expansion.Welding is one of the main links in the manufacturing process of PCD tools,and high-frequency induction brazing is widely used in the welding of PCD tools by virtue of its low-costs in equipment investment,simple welding technique and high production efficiency.Manual welding is still the widest used method of PDC high frequency induction brazing,and the reason is heating process and the temperature of welding are hard to be controlled precisely.So that the welding quality of the cutting tools are not stable,and the production efficiencies are at a low level.It is considered as the main cause of such problems that the temperature of the welding process is hard to control.Thus,a closed loop temperature control system based on fuzzy PID composite is designed for high frequency induction brazing process of PCD tools.Firstly,the development of fuzzy PID temperature control and high frequency induction heating temperature control in China and abroad are analyzed in this paper.Based on a detailed analysis of the PCD tool high-frequency induction brazing process,the overall scheme design of the control system was carried out,including hardware system scheme design and software system scheme design.Secondly,the control strategy is analyzed and selected.The PID control and fuzzy control are studied in details,and their advantages and disadvantages in temperature control are also analyzed.Combined with the advantages of two methods above,a composite control strategy is proposed to control the temperature and heating process of the PCD tools in the high-frequency induction brazing process by combining those two control methods.Thirdly,the hardware design of the control system is carried out.The hardware part of the controller includes infrared thermometer,measurement and control instrument,STM32 single chip microcomputer,D/A conversion module,etc.,which can collect and control temperature.Fourthly,accomplishing the design and analysis of the fuzzy PID controller.According to the characteristics of the controlled object,the parameters of the fuzzy PID controller areset,and the fuzzy control rule table is obtained.The approximative mathematical model is calculated by using the transition curve and the two-point method.With the help of Simulink and Fuzzy toolboxes in MATLAB,the designed Fuzzy PID control is compared with the ordinary PID control.Compared with the ordinary PID control,the control effect of fuzzy PID control can fully meet the temperature control requirements of the PCD tools high-frequency induction brazing.The feasibility of the control strategy is verified.Finally,the software is designed,such as main program flowchart,temperature acquisition system flowchart and fuzzy PID algorithm flowchart.And the software is debugged to verify the feasibility of the temperature control system.