Patent ID: 6975082

Claim:
A variable speed drive system, comprising: a synchronous electric motor, operably coupled to an output shaft, and operable for applying a varying force to the output shaft in response to a varying input AC electric signal; a control unit, operably coupled to a battery, plural rotor sensors, and a drive unit, and operable, in response to signaling indicative of the position of one or more sensors, to generate the input signal according to a first mode for low speed operation, a second mode for high speed operation, and a transitional mode between first and second thresholds, wherein the control unit comprises a polyphase inverter coupled to the drive unit, a controller coupled to the inverter, and a position estimator coupled to the controller and operably coupled to the sensors, wherein the position estimator comprises a phase locked loop operable to control the drive unit in the second mode according to a continuous waveform function, and an angular position interpolator operable to control the drive unit in the first mode according to a step waveform function.