A two degrees of freedom H/sub 2/ controller design methodology for multi-motors web handling system

In web transport systems, the main problem consists to control independently the web velocity and tensions, to prevent web breaks, folding, and damage. Some interesting results have been obtained using multivariable control strategies. However, the existing methodologies are often not systematic or have the drawback to handle the tracking and disturbance rejection problems as a whole. This paper presents a complete methodology in order to design a two degrees of freedom (DOF) controller. The feedforward part is composed of a reference model allowing to obtain desired tracking performances (in particular web tensions and velocity decoupling). The feedback part insuring robustness and disturbance rejection is designed from only two design high level tuning parameters thanks to the standard state control (SSC) methodology. The proposed controller is tested on a three motors web handling platform.