PURPOSE: To surely carry out motion of a loom and synchronous follow up of length- measuring and storing action and improve length measuring accuracy by outputting command pulse with a digital servo control system of a variable speed motor for length measuring and storing, synchronously with rotation of the loom.

CONSTITUTION: In control of a variable speed motor for driving length-measuring and storing device of a loom, a digital servo control system is composed of a command pulse generator, a reversible counter, D/A converter, a driving circuit and a feed back pulse generator. The command pulse corresponding to a target rotation amount of the variable speed motor is input from the command pulse generator to the reversible counter, synchronously with rotation of the loom and the pulse is converted to voltage of analog amount with the D/A converter and fed to the driving circuit as a speed command signal to rotate the variable speed motor. A rotation amount of the variable speed motor is detected with a feed back pulse generator and the value is input to the variable counter and the counter transmits storage pulse number corresponding to deviation of the command pulse and a feed back pulse through the D/A converter and the driving circuit to the variable speed motor to control the motor.