A novel model reduction method for sheet forming processes using wavelet packets

Cross-directional control of sheet forming processes, such as a paper machine, can involve up to 600 inputs and 3000 outputs. For such large-scale systems, it is necessary to find proper model reduction strategies before starting controller design. The paper introduces a model reduction method for such processes based on an efficient modified wavelet packet algorithm. The large dimensional signals in the spatial domain can be transformed into a small number of scaling and wavelet coefficients in the wavelet domain, thus the dimension of the original input-output model is reduced without losing any significant information. Two additional benefits are obtained: (1) the system´s controllability can be significantly improved because the system´s condition number is greatly decreased, (2) the physical limits of the actuators can be directly transformed from the original model to the reduced model