Web winding system robustness analysis via μ-analysis

Web winding system behavior is subject to large variations due to changes in operational conditions. Resorting to robustness analysis appears then necessary. The winding system considered in this paper is speed and tension controlled. Several controllers are considered, including H_∞ and gain scheduling techniques. Stability robustness is analyzed via μ-analysis and ad-hoc models are developed in that sense for the phenomena that are the main sources of uncertainties. It is shown that stability is guaranteed for every phenomenon considered separately, but stability region must be restricted when the system is subject simultaneously to several phenomena. Improvements due to gain scheduling are pointed out