An Adaptive Controller for the Temperature of Injection Molding Machine Cylinder

The heater of injection molding machine's cylinder is composed of several zones which spread along the cylinder's axis. There are strong coupling effects among the zones. To avoid computing-intensive decoupling matrices, we treat every zone as an independent nonlinear time-varying second-order system and compensate them with a proposed self-turning PID controller separately. Due to the self-turning PID controller must include some kind of parameter estimation algorithm, the recursive instrumental variable method (RIV) is employed to avoid computing noise model of objects and ensure the consistent progressive convergence of model parameters in the environment with non-white noise. In addition, we introduce the forgetting factor to modify the RIV method to keep the online continuing identifiable capability for time-varying parameters. It has validated that this controller has better stability, high accuracy and good adaptability to the variety of environmental conditions and cylinder specification in the factory.