PURPOSE: To improve the operation accuracy of carding machines by separately accumulating the rotational speed of a doffer of each carding machine of a carding machine group and a standard rotational speed and controlling the rotational speed of each doffer in such a manner as to keep the accumulated value to zero based on the difference between the above accumulated value and a preset rotational speed.

CONSTITUTION: Motors 3a to 3n for cylinder are driven at a constant speed and motors 6a to 6n are driven at variable speed. A carding machine 1A of a carding machine group is operated at a standard speed. When the speed of a carding machine IC is lowered e.g. by the variation of load or attaching of waste cotton, the difference of the speed is accumulated by a speed regulator 9C. When the accumulated value exceeds a prescribed level, a signal is transmitted to a speed controller 7C for doffer to accelerate the doffer 4C to keep the accumulated value to be zero. The acceleration signal is limited within several % of the standard speed of doffer.