Generating electromagnetic forces through radial air gaps

A method for exerting an electromagnetic force on a body along a body axis, the method comprising:

• with a magnetically permeable axial actuator target having a first end-facing surface and a second end-facing surface to the body;
• a first stationary axial control pole adjacent to the first end-facing surface of the axial actuator target, the first stationary axial control pole being entirely radially outward from the axial actuator target and body and separated from the axial actuator target and the body by a radial air gap and offset axially away from the axial actuator target;
• a second stationary axial control pole adjacent to the second end-facing surface of the axial actuator target, the second stationary axial control pole being entirely radially outward from the axial actuator target and the body, separated from the axial actuator target and the body by a radial air gap and offset axially away from the axial actuator target;
• the first stationary axial control pole and the second stationary axial control pole magnetically connected so that the first stationary axial control pole, the second stationary axial control pole and the axial actuator target form an axial control magnetic circuit;
• and
• a permanent magnet affixed to the rotor and producing a bias magnetic field in the axial actuator target so that the bias magnetic field propagates between the axial actuator target and the first stationary axial control pole and between the axial actuator target and the second stationary axial control pole;
• generating axial control magnetic flux in an electrical axial control coil in the axial control magnetic circuit with an axial control electrical current, the axial control magnetic flux adding to the bias magnetic flux on one of the end-facing surfaces of the axial actuator target while subtracting from the bias magnetic flux on the other end-facing surface of the axial actuator target so that the difference in magnetic fluxes on two end-facing surfaces of the axial actuator target result in an axial electromagnetic force exerted on the axial actuator target.

An electric machine system comprising:

• a stator;
• a rotor having a rotational axis configured to rotate the rotational axis relative to the stator;
• an electromagnetic actuator subassembly comprising:
• an axial actuator target rigidly affixed to the rotor and having first and second end-facing surfaces;
• a radial actuator target affixed to the rotor and having an exterior lateral surface,
• a stationary axial control pole assembly comprising a first axial control pole and a second axial control pole;
• the first stationary axial control pole residing adjacent the first end-facing surface of the axial actuator target, entirely radially outward from the axial actuator target and body, separated by a radial air gap and offset axially away from the axial actuator target, the first stationary axial control pole adapted to communicate magnetic flux with the first end-facing surface of the second axial actuator target;
• the second stationary axial control pole residing adjacent the second end-facing surface of the axial actuator target, entirely radially outward from the axial actuator target and body, separated by a radial air gap and offset axially away from the axial actuator target, the second stationary axial control pole adapted to communicate magnetic flux with the second end-facing surface of the axial actuator target, the second stationary axial control pole being magnetically coupled to the first stationary axial control pole, and the first stationary axial control pole, the second stationary axial control pole and the axial actuator target forming an axial control magnetic circuit;
• an axial control electrical coil adapted to produce an axial control magnetic flux in the axial control magnetic circuit;
• the radial control pole assembly comprising three radial control poles in a plane perpendicular the body rotational axis around the radial actuator target, the radial control poles being entirely radially outward from the radial actuator target and body separated from the radial actuator target by radial gaps, magnetically couped to each other and to the radial actuator target to form a plurality of radial control magnetic circuits;
• a plurality of radial control coils each wound around a respective one of the radial control poles, and when energized with electrical radial control currents, the radial control coils produce respective radial control magnetic fields;
• a first permanent magnet affixed to the rotor and configured to produce a bias magnetic flux in the axial actuator target, the bias magnetic flux traveling from the axial actuator target into the axial control poles, and where the axial control magnetic flux superimposed on the bias flux causes an axial electromagnetic force;
• a second permanent magnet affixed to the rotor and configured to produce a bias magnetic flux in the radial actuator target, the bias magnetic flux traveling from the radial actuator target into the radial control poles, and where he radial control magnetic fluxes superimposed on the bias flux causes radial electromagnetic forces;
• a position sensor configured to sense a position of the rotor;
• and
• a control electronics package configured to control the magnetic fluxes in the axial magnetic control circuit and the radial magnetic control circuits.