Abstract: "Velocity Observer" and "Imbalance Observer" circuits are used to control the journals in the magnetic field of an attractive type active magnetic bearing and/or damper. The circuits are characterized by the use of integrators rather than differential components. The velocity observer circuit uses a position feedback loop and a velocity observer feedback loop, both with variable gain, to control the levitation of the journal in the magnetic field. The imbalance observer circuit recreates the journal acceleration directly from the displacement measurement and can be used optionally on-line and off-line to suppress vibrations.

Abstract: A magnetic/centrifugal-fluid seal comprising a rotating disk-like collar/vane surrounding a rotatable shaft journalled in a housing defined by close-fitting stationary members forming a cavity to accommodate the rotatable shaft and disk-like collar/vane. A magnetic fluid is retained in a close clearance magnetic gap region between the rotatable shaft and the stationary members and is magnetized by an external permanent magnet or electromagnet. At standstill or low-speed the magnetic fluid is retained by magnetic force in the close-clearance magnetic gap region formed by several sets of opposing pole-like teeth confronting the inner surfaces of the rotating disk-like collar/vane. By virtue of magnetic attraction the magnetic fluid can withstand a pressure drop between high and low pressure regions and thus effects a magnetic seal at standstill and low speeds.