PURPOSE: To improve the responsiveness by suppressing operation delay of an output rod caused by frictional resistance on the load side in the case of rod position controlling of a stepping cylinder.
CONSTITUTION: Pressures P1, P2 on both sides of a stepping cylinder are supplied to a cylinder load estimator 25. A cylinder load is obtained in a relevant manner to the difference therebetween. Correction pulse having a pulse number corresponding to the result is generated by means of a pulse generator 28. When deviation is caused between the present rod position and an objective position, first, the correction pulse is added to a driving pulse which is generated by a pulse generator 23 correspondingly to the deviation. Then, the resultant pulse is transmitted to a driving circuit 80 which is a driving source of the stepping cylinder. After completion of the transmittance, the correction pulse only is supplied to the driving circuit 80 in a reverse direction.
HANAZAKI KAZUHARU