PURPOSE: To carry out an operation such as positioning in a high speed and a high accuracy by making a time constant in which driving forces vary with driving signals smaller than a time constant in which opening quantities vary with changes in driving forces applied to first and second control valves.
CONSTITUTION: Valve control units 10a, 11a operate opening degree errors from opening degrees of control valves 3a, 3b detected by opening degree sensors 12a, 12b and opening degree commanding signals for the control valves 3a, 3b coming from a control unit 9, use only the maximum value of the driving forces in positive and negative directions even if there are hysteresises on characters of driving forces applied to the control valves 3a, 3b, and suppress influences thereof. Next, driving forces are detected by driving signal correcting units 10b, 11b, driving signals are operated and output on using differences between the driving forces and outputs of the valve control units 10a, 11a and differential values of the differences, and a time constant in which driving forces vary due to driving signals to the control valves 3a, 3b is made smaller than a time constant in which the opening degrees vary due to driving force changes. It is possible thereby that opening degrees of control valves coincide with commanded values in high speed without chattering, and positioning or the like is performed in high speed and with high accuracy.
MATSUURA SADAHIRO
TAKASO HIROSHI
TACHIKAWA MASAICHIRO
