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Robust tension observers design for web-winding systems

In web-winding systems, precise regulation of web tensions is critical. Generally, most tension control strategies are sensor-based control, which relies on precise measurement of the tensions. However, measuring devices such as load cells or swing rolls are expensive, require either special or extra rolls, add system complexity and reduce system reliability. In this paper, two nonlinear tension observers are designed to estimate web tensions using only conventional system measurements. Firstly, the nonlinear model of an experimental web-winding system is developed. Two nonlinear observers with time-varying error dynamics are deduced from the presented model, and interval matrix is used to deal with the time-varying parameters of the error dynamics. Then, two sufficient conditions of the error dynamics asymptotical stability are obtained based on Lyapunov stability theory, and the observer gains are obtained by solving linear matrix inequalities (LMIs). Finally, some simulation and real web-winding system experiments show the accuracy and effectiveness of the proposed observer.