Robust and Decentralized Control of Web Winding Systems

Abstract

This research addresses the velocity and tension regulation problems in web handling, including those found in the single element of an accumulator and those in the large-scale system settings.A continuous web winding system is a complex large-scale interconnected dynamics system with numerous tension zones to transport the web while processing it.A major challenge in controlling such systems is the unexpected disturbances that propagate through the system and affect both tension and velocity loops along the way.To solve this problem, a unique active disturbance rejection control (ADRC) strategy is proposed.Simulation results show remarkable disturbance rejection capability of the proposed control scheme in coping with large dynamic variations commonly seen in web winding systems.Another complication in web winding system stems from its large-scale and interconnected dynamics which makes control design difficult.This motivates the research in formulating a novel robust decentralized control strategy.The key idea in the proposed approach is that nonlinearities and interactions between adjunct subsystems are regarded as perturbations, to be estimated by an augmented state observer and rejected in the control loop, therefore making the local control design extremely simple.The proposed decentralized control strategy was implemented on a 3-tension-zone web winding processing v line.Simulation results show that the proposed control method leads to much better tension and velocity regulation quality than the existing controller common in industry.Finally, this research tackles the challenging problem of stability analysis.Although ADRC has demonstrated the validity and advantage in many applications, the rigorous stability study has not been fully addressed previously.To this end, stability characterization of ADRC is carried out in this work.The closed-loop system is first reformulated, resulting in a form that allows the application of the wellestablished singular perturbation method.Based on the decomposed subsystems by singular perturbation, the composite Lyapunov function method is used to determine the condition for exponential stability of the closed-loop system.