Patent ID: 8076877

Claim:
A method of controlling an actuator having a stator, a shaft with a plurality of magnets, wherein the stator and the shaft move relative to each other at an interface between the stator and the shaft so that the plurality of magnets provide a first magnetic flux that varies in magnitude and direction along the interface, at least one coil defined on the stator with respect to the interface so that an electric current applied to the at least one coil provides a second magnetic flux that varies in magnitude and direction along the interface responsively to variations in the electric current, said method comprising the steps of: (a) receiving by a controller a first input comprising a first signal indicating a request for a force to be output by the actuator; (b) receiving by the controller a second input comprising a second signal indicating a request to dissipate electrical power in the actuator; (c) in response to the first input, controlling the second magnetic flux so that the second magnetic flux has a predetermined phase with respect to the first magnetic flux; (d) in response to the second input, and variably with respect to the first input, controlling the second magnetic flux so that the phase of the second magnetic flux with respect to the first magnetic flux shifts from the predetermined phase, and the magnitude of the second magnetic flux is controlled in order to substantially maintain the requested force output of the actuator.