Short-term Irregularity
G. Thilagavathi, T. Karthik · WPI Publishing eBooks · 2016
M – Measuring zone DV – Desired value A – Amplifier TD – Time delay S – Speed adjusting unit TG – Tacho generator In open-loop system, there is no check on delivered sliver. In other words the changes in draft are solely based on the mass variation in the input material. Control by this chain of steps requires an additional element, namely a storage device. Since the material has to travel a certain distance between the measuring and adjusting points, and therefore arrives at the adjusting point with a time delay, the signal must be held back in the storage device until this instant. This additional requirement represents a second disadvantage of open-loop control in addition to the lack of self-monitoring. There is a third disadvantage, since very exact values of the adjustment are required at all times. Advantage – This system has got shorter time lag between detection and correction and hence can easily correct even much shorter variations. Since the detection is done at feed end itself it is possible to correct the fault exactly at the right location. Disadvantage – There is no way of ensuring that the variation detected has indeed been corrected.