On Adaptive Control of Color for Paper Machines

This paper will examine and evaluate via computer simulations different methods, both adaptive and nonadaptive, for the feedback control of color of dyed paper. The objective is to maintain the paper color at a desired setpoint despite disturbances such as addition of recycled dyed paper (broke in the industry jargon), and to perform color grade changes as smoothly as possible. The dynamics of a three-dye system are essentially multivariable and nonlinear with a significant dead time, thus the incentive for adaptive control. Several Dahlin controllers with gain scheduling are designed, tested in simulation and compared. Adaptive versions using parameters identified with Recursive Least Squares (RLS) are also tested. For practical applications, the Dahlin algorithm with gain scheduling seems to offer good performance together with simplicity and relative ease of use.