The Application Study Of Fuzzy PID Controller Of Electrohydraulic Control Systems For Injection Molding Machine

Injection molding is a machine which can mould some product of some special shapes quickly. It contains four working process, melting, injecting, keeping pressure and cooling.Injecting process is electro-hydraulic displacement serve control system, and keeping pressure process is electro-hydraulic force serve control system. It is impossible that system have a good performance using PID controllers because of performing the switch from electro-hydraulic displacement serve control system to electro-hydraulic force serve control system. Base on this character, this paper will use fuzzy controller to apply some parameter varieties. However, because of fuzzy controller's structure, it can't have a good precision. So this paper absorbs the advantages of fuzzy and PID controllers, it uses a control method of fuzzy PID controller (FPC). FPC has some structure forms, such as fuzzy turning PID controllers, fuzzy and PID controller combination. The paper refers the working principle and decision of this FPC in keeping pressure process for injection molding.Fuzzy turning PID controller is the controller which changes the three parameters of PID controller by the error and error's varieties of systems, so it can adapt some parameters'varieties for system. Fuzzy and PID controller combination also can adapt some parameters'varieties by corporate output of fuzzy controller and PID controller, and it improves system's precision and response.By simulating of MATLAB for system and doing experiments with RTW toolbox applied in this system, we can get the performance of system by PID controller and FPIDC. In invariablenes pressure and invariableness flow process, compare FPIDC with PID controller when two methods control the system indivisually and the system is switched, and confirm the best controllers.