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: 1) choice of dynamic sliding surface for a system with relative degree greater than one; 2) computation of the discrete-time dynamic sliding surface variable (s_k); 3) and self-tuning of the switching control magnitude to reduce chatterings. A simplified lumped parameter model is constructed to decouple the original multi-channel system into multiple single-channel subsystems. Experimental results show effectiveness of the proposed method