H _∞ robust control design for unwinding tension system

An H _∞controller based on linear matrix inequality (LMI) method is presented to strengthen the stability of the tension in unwinding section of printing press, and the controller is analyzed and verified by the simulation. A nonlinear model is established according to the unwinding system working principle, and a linear model is constructed by analyzing the uncertain and time-varying parameters. Then an H _∞ controller is designed following the linear model with LMI. The robust disturbance rejection performance of the H _∞controller is verified by the simulation, and the results show that the unwinding tension system can be controlled easily with LMI robust control concepts. LMI-based controller is endowed with advantages of requiring no weighting functions, optimizing the parameters of controller automatically and meeting transient requirements with pole placement constraints, and ensures the unwinding tension system to get asymptotically stable and the performance can be optimized according to the time-varying parameters and external disturbances.