A Study Of Fuzzy Self-tuning PID Control And Its Application In Injection Molding Machine Of Electro-hydraulic Systems

The injection molding machine is a kind of fast Molding equipment which can produce products through inject melted raw materials to mould and then cooling. Its working process mainly includes shut the mould, injection, pressure-keeping, cooling and open the mould. The key to affect the quality of products is injection and pressure-keeping process controlled by Injection control system. For high quality products, design a High-performance controller for injection system to make injection velocity and pressure track fast with the expected changes base on control theory is necessary.In this study, Injection system is a hydraulic system. Its injection process is a electro-hydraulic position control system and pressure-keeping stage is a electro-hydraulic force control system. Due to the complexity of hydraulic system. Melted material flow and injection mould etc. establishing accurate mathematical model became difficult or even impossible. Therefore, the traditional PID control can't satisfy the requirements of control system. For injection system is a nonlinear, large delay and intermittent work system. This paper put forward a control strategy base on fuzzy reasoning called fuzzy self-tuning PID to implement the system control.The Injection system requires injection velocity, holding pressure have good Dynamic performance and Steady precision, also, the switch from Injection stage to pressure-keeping stage needed to be performed with fast and smooth. So,this paper introduce the fuzzy reasoning theory to the control system, combining quite matured of PID control and design a fuzzy self-tuning PID controller base on establishing the dynamic model of electro-hydraulic control system. this kind of fuzzy self-tuning PID controller can adjust and optimize the three parameter of PID all through the whole process, and realize to Improve the response speed of system and steady precision.In specific research, this paper established a Fuzzy self-tuning PID controller and a improved fuzzy self-tuning PID controller through Matlab/Simulink software platform. Then compare and analysis the control effect of each controller designed based on the establishing of the position control system, the force control system and the switch of control system through simulation. Finally, applied the designed controller to control the experimental equipment. Simulation and experimental results both indicate that,compared with the traditional PID control,The introduce of fuzzy PID controller obviously improve the performance of the control system, and the improved fuzzy PID controller enables the system control effect once again.