Discrete Time Predictive Sliding Mode Control of Hot Strip Mill. Application of Linear Reaching Law.

Abstract

Sliding Mode Control (SMC) as a Variable Structure System (VSS) and a nonlinear control theory, has been widely used in various engineering fields, and carried out excellent performances in practical use. The purpose of this study is to attempt to utilize SMC for hot strip hishing mill and present the details of design procedure of discrete time sliding mode servo-controller. The plant is described as a MIMO system and the thickness measuring dead-time is added into state space equation as a series of delay elements. The influence of this dead-time can be nullified by the use of an augmented VSS observer. A state predictor is also used to compensate for the time delay caused in calculation and transmission of process 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 servo-controller.