INJECTION VELOCITY CONTROL BASED-ON AN ITERATIVE LEARNING AND FEEDBACK COMBINED CONTROLLER

Injection velocity is a key variable in injection molding process. The dynamics of injection velocity is largely affected by the control valves used in the hydraulic system. Previously, it has been controlled precisely using advanced control algorithms based on servo-valves. However, this increased significantly the capital and maintenance costs. In this paper, the injection velocity was controlled using economical but slow response proportional valves. Iterative learning control is adopted to exploit the repetitive nature of the process for control performance improvement with the slow valves. Most nonlinearity is handled by the ILC control, with a simple feedback control incorporated to provide within-cycle disturbance rejection. Experiments show that the proposed method can work well over a wide range of operating conditions.