Discrete-time VSS temperature control for a plastic extrusion process withwater cooling systems

The plastic extrusion process with water cooling is a variable structure sy stem in nature. To implement discrete-time variable structure control, thre e important problems are considered. They are: choice of dynamic sliding su rface for a system with relative degree greater than one, computation of th e discrete-time dynamic sliding surface variable (sk), and self-tuning of t he switching control magnitude to reduce chatterings, A simplified lumped p arameter model is constructed to decouple the original multichannel system into multiple single-channel subsystems. Experimental results show the effe ctiveness of the proposed method.