METHODS FOR MODELING TWO-DIMENSIONAL RESPONSES OF CROSS-MACHINE DIRECTION ACTUATORS IN SHEET-FORMING PROCESSES

A plurality of random probing sequences are used to perturb a corresponding plurality of cross-machine direction (CD) actuators of a web manufacturing machine. The web of sheet material is measured as the CD actuators are perturbed. The global process machine direction (MD) dynamics is estimated and a CD response is estimated for each of the plurality of CD actuators using the plurality of random probing sequences, measurements of the web of sheet material and the estimated global process MD dynamics. The estimated global process MD dynamics and the estimated CD responses form 2D responses for the plurality of CD actuators. To refine the 2D responses, the estimates of global process MD dynamics, and CD responses for each of the plurality of CD actuators are iterated. The actuator dynamics of the plurality of CD actuators may also be estimated and used in the estimates of the global process MD dynamics of the plurality of CD actuators and CD responses for each of the plurality of CD actuators. Variations that are not associated with actuator responses are removed from the estimated CD responses, for example by filtering. The estimated CD responses may be further refined by selecting one of the CD responses as a reference response. All remaining CD responses are shifted into alignment with the reference response to determine relative CD response locations and to define a group of overlapping CD responses. Using iterative techniques, a mean response is determined from a group of overlapping CD responses and variation bounds are set above and below the mean response. A family of probable CD responses are generated within the variation bounds and a most probable response is selected from the family of probable responses for each CD actuator response. The CD response for each CD actuator is replaced with the most probable response shifted by an appropriate amount for each CD actuator and multiplied by an optimal gain.