Dynamics and control of accumulators in continuous strip processing lines

Accumulators in a strip processing line are primarily used to allow for rewind or unwind core change while the process continues at a constant velocity. Accumulators facilitate continuous operation of the process line and thus constitute an important element of a continuous strip processing line. This paper studies the coupled dynamics of the accumulator carriage motion, rollers and web spans. Suggestions are made in an effort to integrate the tension dynamics of individual spans in an accumulator. An average dynamic model that integrates the dynamic models of individual spans in the accumulator is derived. This aggregation of the dynamics can facilitate control design for the accumulator carriage. Hydraulic system modeling associated with the accumulator is studied. Aspects of the hydraulic system such as drop due to friction in long pipes and dominant damped resonant frequency of the hydraulic system are discussed. A compact state space model of the dynamic model of the accumulator is obtained from the average span tension dynamics, carriage dynamics, and pressure dynamics. Some experiments conducted on an Alcon continuous process line are discussed.