Electro-hydraulic Hybrid System Design And Control Research Of The Injection Molding Machine

Injection molding machine is one of the main equipments of plastic molding. Its key technologies are to develop energy-saving drive and control systems. This paper is based on national science and technology support plan "electro-hydraulic servo hydraulic transmission and control technology research of precision plastic molding equipment". Major developments are as follows:1 The research status of hydraulic system power consumption, drive system and control strategies of the injection molding machine are presented both in and out of china. The energy consumption characteristics of the common injection molding machine hydraulic system was compared. Pointed out that the all-electric servo-motor driven injection molding machine is not suitable for our country at this stage because of the high cost and we should develop the hybrid electro-hydraulic injection molding machine.2 Two electric-hydraulic driven hydraulic system solutions of the injection molding machine are proposed. By comparing the characteristic in the aspects of energy efficiency and cost, I choose the servo motor directly driving the fixed pump hydraulic system as the final plan and designed the details of the hydraulic schematic. And also established its math models and the simplified loading model and analyse the stability of this system.3 According to the characteristics of injection molding designed an fuzzy controller based on an pressure and flow optimization algorithm. A method of flow control through the difference of pressure was presented to create a nonlinear function, and a fuzzy control method is used to adjust its parameter on line due to parametric uncertainties of hydraulic system itself and load model, by which the flow signal was optimized. And, it is not necessary to design the point where the velocity control switch to pressure control. Then, a PID control is combined to realize pressure tracking. A MATLAB model was created and the results of simulation show this method worked very well.4 Both hardware circuit and soft program were made based on TMS320F2812 chip as a lower controller of the injection molding machine. The experimental results show that the proposed method can satisfy the requirement for injection pressure of injection molding machine and has good self-adapting character:the injection and holding pressure curve can be well followed, and got an faster system response without overshoot with good repeatability of the products.