PURPOSE: To determine the position of a valve smoothly according to the load fluctuation of the valve by enlarging deceleration starting position deviation in the case of an motor-operated valve not being decelerated down to the command positioning speed, and reducing positioning speed in the case of the valve being out of the dead zone when the stop of a motor.
CONSTITUTION: A target position signal 1 is read first, and then a present position detection signal 8 is read from a position detecting part 7. This present position detection signal 8 is fed back to a control part 2 so as to compute deviation between a target position and the present position and to judge this deviation value. The control part 2 determines whether a motor M is to be operated at normal speed, decelerated or stopped respectively depending on deviation > positioning starting deviation, positioning starting deviation ≥ deviation > dead zone, or deviation ≤ dead zone. In this case, a judgement is made from the data during deceleration given from the position detecting part 7, and when the deceleration is incomplete, the deceleration starting position deviation is enlarged. In the case of no change in the target position no valve entering the dead zone after the stop of the motor M, mode shift is performed to reduce the positioning speed. This action is repeated every time when the target position is changed.
NAKAJIMA KOSHIROU
HIRANO MAKOTO
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