Patent ID: 8288970

Claim:
A system for adaptive operation of a personal care resonant appliance having a workpiece which is driven through an amplitude of motion by a motor drive mechanism which includes a stator member, comprising: a circuit ( 13 ) within the personal care appliance for measuring average electrical current through the stator member ( 15 ); stored information ( 10 ) which relates values of average electrical current through the stator during operation of the device to amplitude of motion of the workpiece, wherein the personal care appliance is characterized by a workpiece amplitude/frequency response curve similar to the stator current/frequency response curve; and a processor ( 17 ) operating with a stored program for adjusting the operating frequency of the personal care appliance in response to the measured values of stator current to produce an adjusted stator current value which correlates with a desired amplitude of motion indicating a desired match between the operating frequency and the resonant frequency of the personal care appliance, in accordance with the stored information.