ℋ∞ robustification of a paper machine cross-directional control system

This paper considers ℋ_∞ robustification of an industrial paper machine cross-directional (CD) control system. The existing industrial controller is reinterpreted as a precompensator weight for shaping the open-loop response. The robustification is then achieved by performing a robust stabilization of the nominal plant model and industrial controller combination. The large scale (226 inputs and 226 outputs) ℋ_∞. optimization problem is decoupled into 226 independent SISO systems by an application of recent results for spatially invariant systems. The robustified closed-loop is then implemented by augmenting the industrial controller with a low-order prefilter. It is then demonstrated that the robustness of the closed-loop system has been significantly improved while its performance remains well-preserved