A sensorless active magnetic bearing suitable for use in rotating machinery and seals, contemplates a circuit and a process for actively controlling the position of an object using magnetic forces without mechanical contact between the object suspended 10 and the components of the magnetic positioner, and without the necessity for discrete sensors for determining the position of the object suspended. Electromagnets L.sub.1 and L.sub.2 are placed in an ordered coaxial array surrounding an object to be suspended, and impart magnetic forces while simultaneously detecting the position of the object in accurate registration with the position of the corresponding electromagnets. In one embodiment constructed according the principles of the present invention, the currents to the electromagnets are controlled by switching amplifiers 20 that switch the amplitudes of the supply voltages applied across the coils of electromagnets L.sub.1, L.sub.2. When two or more electromagnets are placed electrically in series, the absolute magnitude of the voltage developed across a coil indicates its relative inductance. The position of the member along an axis may be detected by comparing the absolute magnitude of the voltage drops of the two electromagnets located on either side of the member being supported and along that axis because the inductance of the electromagnet varies with its distance from the supported member. In another embodiment constructed according these principles, a single electromagnet L.sub.1 is placed electrically in series with a reference coil L.sub.ref and the absolute magnitude of the voltage across the reference coil may be used to detect the position of the member being supported.
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.
Systems are disclosed for holding an object in mid-air under the influence of fixed and variable magnetic forces countering the gravitational pull of the object. These systems can be used for display purposes, such as advertising or commercial displays; and/or educational purposes such as spinning globes. It is perceived that the larger the gap between the suspended object and the structure containing the magnets and control systems, the more desirable the device becomes.
A method and a corresponding inking unit permit positioning of a roller into at least two different operating positions. The roller is, in particular, a vibrator roller of an inking unit for a rotary printing machine. The roller is positioned by controlling or regulating a magnetic bearing device in which the roller is mounted.
The apparatus includes a motor control circuit including an amplifier with an inductance compensation circuit responsive to a motor, such as a switched reluctance motor, having inductance variations. The inductance compensation circuit includes at least two inductance compensation values and switching means for alternatingly coupling and decoupling at least one of the inductance compensation values from the inductance compensation circuit providing at least first and second inductance compensation for driving the motor in response to variations in the inductance of the motor.
A magnetic suspending device which can detect the temperature of a controlled object and assure a safe operation thereof without any need for any special construction or work to the device and any special maintenance is disclosed. In the magnetic suspending device comprising a pair of electromagnets (11, 13) disposed opposite to each other, a magnetizable controlled object (15) disposed between the pair of electromagnets (11, 13) and position displacement detection sensors (12, 14) disposed opposite to each other for detecting a position displacement of the controlled object (15), wherein detection signals from the position displacement detection sensors (12, 14) are inputted to a control circuit unit (20) for performing phase compensation and gain adjustment, wherein control outputs from the control circuit unit (20) control magnetic attractive or repulsive forces of the pair of electromagnets (11, 13), and wherein the controlled object is magnetically suspended by the pair of electromagnets without contact at an arbitrary position, a temperature operational circuit unit (30) is provided for detecting the size and temperature of the controlled object (15) using the detection signals from the position displacement detection sensors (12, 14).
