Continuous Control of Sliver Thickness
Fumio Murakami, Toshio Shoman, Susumu Kase · Journal of the Textile Machinery Society of Japan · 1960
This is an attempt to approximate the characteristics of two major types of servo-draft systems the open-loop system and the closed-loop system-by comparatively simple mathematical models consisting of linear transfer functions. The effectiveness of servo-draft systems in terms of the frequency response of the mathematical models has been investigated with the following results: (1) Sinusoidal variations in input sliver thickness cannot be effectively attenuated by the servo-draft system if the frequency of such variations exceeds a certain limit. This limit frequency is fixed by the time constants of the system components. (2) The open-loop servo-draft system is much higher in limit frequency than the closed-loop system if their time constants are equal. In other words, the open-loop system can attenuate sliver irregularities of higher frequencies than the closed-loop system can. (3) In most servo-draft systems there are frequency ranges in which the normalized amplitude of input thickness variations is magnified, rather than attenuated. (4) The open-loop and closed-loop systems can be combined Into one servo-draft system to make use of the advantages of the two systems. The characteristics of such a combined system are easily predictable from the characteristics of the two constituent systems.