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

The plastic extrusion process with water cooling is a variable structure system in nature. To implement discrete-time variable structure control, three important problems are considered. They are: choice of dynamic sliding surface for a system with relative degree greater than one, computation of the discrete-time dynamic sliding surface variable (s_k), and self-tuning of the switching control magnitude to reduce chatterings. A simplified lumped parameter model is constructed to decouple the original multichannel system into multiple single-channel subsystems. Experimental results show the effectiveness of the proposed method