Patent ID: 7376525

Claim:
An apparatus comprising: a brushless motor having a rotor, a stator, and electrical terminals accepting an electric drive signal, the motor characterized by an a priori unknown initial phase of the rotor with respect to the stator; a driver connected to the electrical terminals and producing the electric drive signal; an incremental displacement sensor configured to measure a displacement of the rotor with respect to the stator and producing an output signal indicative of the displacement; a processor having an input receiving the output signal from the displacement sensor and having an output connected to the driver, the processor configured: to cause the driver to produce the electric drive signal according to a predetermined function of time, to observe the output signal from the displacement sensor resulting from the electric drive signal, and to perform mathematical computations on the basis of the observed output signal and a model of dynamic behavior of the motor to estimate the initial phase of the rotor with respect to the stator.