Model reference adaptive control of cavity pressure in injection molding during filling and packing phases

Abstract

Mold cavity pressure in injection molding machine plays an important role in determining the quality of molded products. However, the dynamic of cavity pressure is time-varying in relation to the hydraulic servo-valve opening. A cavity pressure control scheme was proposed by applying Model-Reference Adaptive Control (MRAC) to deal with the time-varying nature of cavity pressure. The adjustment of controller gains was carried out by MIT Rule. A lead compensator was also employed to improve the transient response. The simulation demonstrated the effectiveness of MRAC-based system during filling and packing phases even in the presence of parameter variations, zero mismatches, and measurement noise. The actual cavity pressure response is able to follow the output of prescribed reference model with varied set point profile. In the future, the proposed control scheme is potential to be implemented in the real system.