Learning-enhanced PI control of ram velocity in injection molding machines

Abstract

This paper presents the development of a new learning enhanced PI control method for cyclical control of the ram velocity in injection molding machines. The overall structure of the control consists of a feedback and a feedforward component. The PI feedback control stabilizes the system, and the feedforward component incorporates an iterative learning control (ILC) algorithm to compensate for nonlinear/unknown dynamics and disturbances, thereby enhancing the performance achievable with feedback control alone. A simple and effective tuning method is further developed for the composite control structure which yields both the PI and ILC gains given only a first-order model. A nonlinear physical model derived for the process serves as the basis for the simulation study of the proposed control scheme. A comparison of the performance achieved with an optimally tuned PI control is also provided to highlight the advantages of the proposed control scheme. © 2002 Elsevier Science Ltd. All rights reserved.