Patent ID: 7116070

Claim:
A method for controlling a rotor of an electric motor, the motor having a plurality of stators and a winding connected to each stator of the plurality of stators, said motor being responsive to electric current provided to a set of windings of the motor causing the rotor to change position, said method comprising: controlling position of said rotor from a present open loop position to an open loop intended position in an open-loop operation mode, by; deriving the open loop present position of the rotor from a back electromotive force (EMF) based on at least one of current and voltage conditions of the windings; determining an electric current to move said rotor from said open loop present position to said open loop intended position; providing said electric current to said set of windings to move said rotor towards said open loop intended position; and determining a present open loop velocity of said rotor from said at least one of current and voltage conditions; transitioning control of the motor from the open-loop operation to a phase-locked loop operation when the present rotor velocity reaches a transition velocity; and controlling a subsequent velocity of said rotor via a phase-locked loop operation after said transition velocity is reached, said subsequent velocity determined by a phase-locked position of said rotor and an intended phase-locked position of said rotor, by; deriving a phase-locked electrical phase for said phase-locked position by; determining a back EMF flux value induced over each winding connected to each stator of the plurality of stators from said at least one of current and voltage conditions, including; determining a current back EMF value from said at least one of current and voltabe condition, and integrating values of the current back EMF and previously determined back EMF over each said winding using integration constants with values determined from the back EMF value at the time of transition; determing a phase error representing the difference between a present electrical phase of said rotor and an intended electrical phase representing said intended phase-locked position; and providing an adjustable phase-locked electric current to said set of winding to move the rotor towards the intended phase-locked position, said current being adjustable to track said phase error to adjust said subsequent velocity.