PURPOSE: To prevent waste of power consumption by estimating a varying state of bearing load to adjust power supply to an eletromagnet.
CONSTITUTION: A pressure varying state is monitored based on pressure signals outputted by pressure sensors 4, 5, and based on the pressure varying state a time-based varying period of bearing load and the maximum value of the bearing load are estimated. A computing element 6 actuates a first and a second transistors 12, 13 of an amplifier 7 in order to cope with the estimated bearing load variation. Accordingly, a power source voltage is determined in accordance with a variation value of the bearing load. Control quantity is varied in compliance with the variation of the bearing load. Consequently, in the case of small bearing load, power consumption (supply voltage V × current I) can be suppressed at a small value.
SUGAWARA HIROSHI
YOSHIMI MANABU
FUCHIGAMI HIROSHI
