Nonlinear control of an electrohydraulic injection molding machine via iterative adaptive learning

Examines the control of an industrial injection molding machine (IMM) for both mold filling and mold packing. The machine is a Boy 50 Ton system operated by hydraulics with electronically controlled valves. A nonlinear model of the system is determined for the filling and packing stages, then verified against experimental data. The model includes several key aspects of the actual machine dynamics including stick-slip friction, time delays, nonlinear valve flow characteristics, and deadzones. A feedforward control input is determined via an iterative learning control scheme. This input is combined with either a feedback strategy or an open-loop strategy for the filling and packing control phases, respectively. The time delay, which exists in both stages, is accounted for by time shifting the learning feedforward signal relative to the feedback control signal. Simulation and experimental investigations indicate the benefits of the proposed strategy for control of electrohydraulic IMMs. Subsequent to demonstrating the benefits for fill-stage and pack-stage learning control, a complete cycle, including fill-to-pack transfer, is demonstrated.

[1]  W. I. Patterson,et al.  Cavity pressure control during the cooling stage in thermoplastic injection molding , 1996 .

[2]  Xiaoqi Tang,et al.  A new method on repetitive tracking control of electro-hydraulic servo systems , 1998, Proceedings of the 1998 American Control Conference. ACC (IEEE Cat. No.98CH36207).

[3]  Hyung S. Cho,et al.  On the realization of an accurate hydraulic servo through an iterative learning control , 1992 .

[4]  I. Pandelidis,et al.  Optimal anticipatory control of ram velocity in injection molding , 1988 .

[5]  Suguru Arimoto,et al.  Bettering operation of Robots by learning , 1984, J. Field Robotics.

[6]  W. J. Thayer,et al.  Controls for injection molding of thermoplastics , 1981 .

[7]  Watton,et al.  Fluid Power Systems , 1991 .

[8]  Jong‐Hwei Wei,et al.  Adaptive model following control of the mold filling process in an injection molding machine , 1991 .

[9]  Michael Pecht,et al.  Injection Molding Process Control - A Review. , 1987 .

[10]  W. I. Patterson,et al.  Cavity pressure dynamics and self-tuning control for filling and packing phases of thermoplastics injection molding , 1996 .

[11]  Masayoshi Tomizuka,et al.  Analysis and Synthesis of Discrete-Time Repetitive Controllers , 1989 .

[12]  Dean Karnopp,et al.  Computer simulation of stick-slip friction in mechanical dynamic systems , 1985 .

[13]  Roberto Horowitz,et al.  Learning Control of Robot Manipulators , 1993 .

[14]  Ampere A. Tseng,et al.  A Multivariable Self-Tuning Controller for Injection Molding Machines , 1989 .

[15]  W. I. Patterson,et al.  Dynamics and control of pressure in the injection molding of thermoplastics , 1987 .

[16]  Suguru Arimoto Robustness of learning control for robot manipulators , 1990, Proceedings., IEEE International Conference on Robotics and Automation.

[17]  Roberto Horowitz,et al.  A new adaptive learning rule , 1991 .

[18]  Rui Liu,et al.  On the Limitations of Force Tracking Control for Hydraulic Servosystems , 1999 .