US Patent 7482717 Servo actuator with self positioning rotor and method

A linear actuator is provided with an integral permanent magnet, brushless motor capable of axial, self adjustment of the rotor position within the stator for field weakening. Axial displacement of the rotor within the stator allows for significantly improved speed performance from aligned rotor/stator components during light axial loading. Upon contact with a load, the screw and nut, as an integral part of the motor rotor, self align to fully engage within the stator for generation of high forces with minimal current. This axial shift can further be used as a high precision, low cost measure of the force applied for quality assurance purposes.