To secure high speed control while low consumption of power is being maintained with process loading for a microprocessor lowered by separating a high speed operating part from a low speed operating part.

Judging from controlling a valve 14 in a loop formed out of a PID operating means 18 located at the rear step side of a deviation amplifying means 30, a scaling means 19, a D/A converter 20, an actuator 21, the valve 14, an angle sensor 22, and of an A/D converter 23, high speed renewal operation, for example, roughly at the period of several micro seconds through several tens of micro seconds, is required. In opposition to the above, operations by a normalizing reverse converting means 27 located at the forward step side of the deviation amplifying means 30, an angular converting means 28, and a reverse scaling means 29, are operations for digital signals DS which are setting signals from precedent systems such as a controller and the like, low speed operations roughly at the sampling period of a houdred micro seconds through several hundreds of micro seconds, are good enough so as to thereby aid much to a reduction in power consumption. By this constitution, high speed control can thereby be assured while power consumption is being maintained low.