Discrete Predictor and Sliding Mode Control of Hot Strip Fimishing Mill.

Abstract

Sliding Mode Control (SMC) as a Variable Structure System (VSS) and a nonlinear robust control theory, has been widely used in various engineering fields today, and carried out excellent performances in practical use. The purpose of this study is to make a try of utilizing SMC for hot strip finishing mill and present the datails of design procedure of discrete time sliding mode servocontroller. The plant is described as a MIMO system and the thickness measured dead-time is added into state space as a series of delay elements. The influence of this dead-time can be cancelled with the use of an augmented VSS observer. A state predictor also is used to compensate the time delay caused in calculation and transmission of control computers. A new approach of discrete sliding mode control which can remove the chattering phenomenon entirely, is proposed with the use of linear reaching law. The usefulness and robustness of the SMC are demonstrated through computer simulations under plant perturbation and external disturbances, and compared with a conventional optimal serve-controller.