The on-line control of the sliver thickness in roll-draft mechanism is very important. The drawing process in manufacturing staple yarn is the last process where the quality of the end product, namely the yarn quality, can be improved. In this study we have searched the possibility to apply a new driving concept, individual motor drive system, on controlling the slivers irregularities, not using the autoleveller, but changing the main draft ratio, while several motors drove each drawing roll and the thickness of the output sliver was measured. As results of this study revealed that 1) the individual motor drive system can be available, if the control system is applied. 2) The irregularities of the sliver can be reduced by using the on-line measurement of the sliver thickness and feeding back the signals to the digital Pl-controller. 3) The transient state persists relatively long of about 85cm, when a bundle of the input sliver falls down. 4) The optimal controller parameters K2=1.125, T1=0.747sec.