Research On The Pneumatic Control System Of Large-tonnage Superplastic Forming Equipment

Superplastic forming processing refers to the processing of metal using the characteristics of metal,in order to obtain the precise size,complex shape and grain size uniformity and fine thin-walled parts,is a kind of advanced manufacturing technology.With the development of China's space industry and the progress of national defense science and technology,the research of large tonnage superplastic forming equipment is becoming more and more important.The pneumatic pressure control system in superplastic forming equipment will affect the forming precision of parts.Especially in the large tonnage superplastic forming equipment,the deformation of the material will cause great changes in the volume of the gas chamber,which makes the system difficult to achieve accurate control of the air pressure in the air chamber.This paper focuses on the pressure control method of large tonnage superplastic forming equipment,and develops an pneumatic control system with visual operation and remote control function.The demand analysis of superplastic forming equipment pneumatic control system is carried out.It uses the mechanism method to complete the mathematical modeling of the upper and lower air chambers in the pneumatic control system.The model structure is corrected and the model parameters are determined by experiment.Then,the time variant model of chamber is deduced.Traditional PID control,neural network control,fuzzy control and fuzzy PID control theory are studied.And the control system of the fixed volume cavity model and the volume expansion model of 10 times is built respectively based on the MATLAB/Simulink simulation software.The step response and trapezoidal wave response of the system under different control methods are studied.The comparison of the simulation results shows that when the fuzzy PID control is applied to the system,the overshoot of the system step response and the trapezoidal wave signal response is smaller,and the adjustment time is shorter,which meets the control requirements.The hardware design of the pneumatic control system and the software design of the pneumatic control system is completed.The hardware design mainly includes requirement analysis,overall design,hardware selection and system construction based on Ethernet communication protocol.The software design includes the design of the main control interface based on Kingview,the design of file sharing based on FTP and the design of air pressure control method based on MATLAB.Among them,the main control interface mainly includes the air pressure parameter setting interface,the real-time status display interface,the alarm interface and the history data report interface.OPC communication technology is used to realize the data exchange in all parts of the pneumatic control system.And after the fuzzy PID control method is applied to the actual superplastic forming equipment,the function of the pneumatic control system is tested and the accuracy is tested.The pressure test proves that the pneumatic control system based on fuzzy PID control has higher accuracy and realtime performance.The parts processing test shows that the parts processed by superplastic forming equipment meet the process requirements.