Fixed gain electromagnetic actuator and electromagnetic bearing incorporating same

In an electromagnetic actuator for creating a fixed gain net force on a body, the improvement comprising:

• at least two pairs of magnetic permeable poles spaced about the body defining air gaps between the actuator and the body, each pole of each pair wound with a control coil and a separate bias coil;
• the control coils and the bias coils of one said pair of poles wound in the same direction;
• the control coils and the bias coils of each opposing said pair of poles wound in opposite directions;
• said bias coils of opposing pairs of poles connected in series;
• and
• said control coils of opposing pairs of poles connected in series;
• a bias source for said bias coils for producing a current in the bias coils for producing equal strength magnetic fields in the air gaps on opposing sides of the body;
• and
• a control source for said control coils for providing a current in the control coils for producing an increase in the equal strength magnetic field on one side of the body and producing a corresponding equivalent decrease in the equal strength magnetic field on the opposing side of the body to compensate for any external forces acting on the body.

An electromagnetic bearing comprising:

• an actuator including at least two pairs of opposing pole means spaced about a rotor for defining air gaps between the actuator and the rotor;
• bias means for each pole means for establishing equal strength magnetic fields in the air gaps on opposing sides of the rotor;
• separate control means for each pole means for controlling the position of the rotor;
• a bias source for said bias means for providing a bias current in said bias means for producing equal strength magnetic fields in the air gaps on opposing sides of the rotor establishing a steady-state position for the rotor with respect to said pole means;
• sensor means for detecting displacement of the rotor relative to said steady-state position;
• and
• means, responsive to said sensor means, for correcting displacement of the rotor under loading conditions including a control current source for providing a control current in said control means producing an increase in the equal strength magnetic field on one side of the rotor and an automatic corresponding equivalent decrease in the equal strength magnetic field on the opposing side of the rotor, and means to selectively activate said current source.

An electromagnetic bearing for controlling the position of a body in one plane comprising:

• four pairs of magnetic permeable poles spaced from the body defining air gaps between said poles and said body, each pair opposing another pair;
• position sensor means for detecting the position of the body with respect to said poles;
• a control coil wound about each pole and a separate bias coil wound about each pole, the control coils and the bias coils of one opposing pair of poles wound in the same direction, the control coils and bias coils of the other opposing pair of poles wound in the opposite direction;
• said bias coils of each two pair of opposing poles connected in series and said control coils of each two pair of opposing poles connected in series;
• a bias source interconnected with said bias coils for producing equal strength magnetic fields proximate each pair of poles;
• position controller means, responsive to said position sensor means, for increasing the magnetic field proximate one pair and automatically reducing the magnetic field by an equivalent amount proximate an opposing pair of poles in response to any deflection of the body with respect to said poles to provide a correcting force on the body including a control source for said control coils comprising at least one power amplifier for each two pairs of poles for supplying a current in said control coils in an amount sufficient to compensate for any upsetting forces acting on the body.