Patent attributes
A control device includes a differential amplifying circuit for obtaining a difference between values of exciting currents (exciting voltage values) supplied to a pair of axial electromagnets and a pair of radial electromagnets, multiplying the obtained difference by coefficient times, and outputting it as the bearing load in an axial direction and a radial direction. The exciting current includes steady current supplied to the axial electromagnets and the radial electromagnets and control current which varies by the displacement of a main shaft. By supplying the steady current to the axial electromagnets and the radial electromagnets, the magnetic attraction force of the axial electromagnets and the radial electromagnets having non-linearity is linearly approximated. Accordingly, the difference between the values of the exciting currents (exciting voltages) supplied to a pair of electromagnets is obtained and is multiplied by coefficient times, thereby obtaining a value corresponding to the bearing load.
