The effect of speed-loop bandwidths and line speed on system natural frequencies in multispan strip processing systems

Strip processing systems (SPSs) are composed of multiple tension zones. These zones are separated by driven rolls such as bridles, the speed of which is regulated by a closed-loop controller. Given that the typical tension regulator regulates tension by trimming the reference to a closed speed-loop controller, the designer of the tension regulator cannot ignore the effects of closing the speed loop, and line speed, on the SPS natural frequencies. These natural frequencies are typically computed as the eigenvalues of an equivalent translational cascaded spring-mass system. This paper discusses these effects.