The high response and high efficiency velocity control of a hydraulic injection molding machine using a variable rotational speed electro-hydraulic pump-controlled system

High response and high efficiency velocity control of a hydraulic injection molding machine (HIMM) is requested especially for the process of high-tech industries, such as CD and DVD disks, plastic optical lens, light guide plates, etc. Instead of the hydraulic valve-controlled systems that have the problem of low energy efficiency but have been used widely in today’s HIMMs, the paper develops a high response and high energy efficiency electro-hydraulic pump-controlled system driven by a variable rotational speed AC servo motor for achieving high response and high efficiency velocity control in HIMMs. A constant displacement axial piston pump combined with the AC servo motor is developed in this research as the high response electro-hydraulic pump-controlled system for the HIMMs. For that, the control strategy, signed-distance fuzzy sliding mode control (SD-FSMC) is developed to simplify the fuzzy rule base through the sliding surface for practical applications. The developed high response variable rotational speed electro-hydraulic pump-controlled system controlled by SD-FSMC is implemented and verified experimentally for velocity control with various velocity targets and external loading conditions. Furthermore, the energy efficiencies of different experiments are analyzed and compared precisely by the power quality recorder used to measure the electrical power consumed by the AC servo motor.