Design tension controller of unwinding system based on LMI-based H _∞ robust control

The unwinding system is the most important section for tension generating of the gravure printing machine, and how to maintain the stability of the tension in unwinding system is a key problem to ensure the printing quality. In this paper, an H_∞ controller based on Linear Matrix Inequality (LMI) method is presented to strengthen the stability of the tension in unwinding section, and the controller is analyzed and verified by the simulation. Firstly, a nonlinear mathematical model is established according to unwinding system's working principle, and a linear mathematical model is constructed by analyzing the uncertain and time-varying parameters. Secondly, based on the mathematical model and LMI framework, a H_∞ robust controller is designed. Finally, the performance of the H_∞ controller is verified by the simulation, and the results show that the proposed tension controller has better robustness and disturbance rejection than traditional PID controller in tension control of the unwinding system.