Patent ID: 6121747
Filing Date: 2000-09-19
Classification: H02P,Y10S

Abstract:
A controller for an electric motor, comprising:a reference circuit which generates a reference signal having a phase and frequency determined in accordance with a set of motion parameters input to the circuit; andcontrol circuitry, which receives the reference signal and receives a feedback signal from a rotation detector coupled to the motor, the detector having an inherent angular rotational resolution, and compares the reference signal and the feedback signal to generate a drive signal used to drive the motor at a speed and phase of rotation determined by the frequency and phase of the reference signal,the phase of rotation of the motor being locked to the phase of the reference signal such that deviation of the phase of rotation relative to the phase of the reference signal at steady state is substantially smaller than the rotational resolution of the rotation detector,wherein the control circuitry comprises a first phase-frequency comparator, which generates a phase-frequency signal responsive to the deviation between the phase of the reference and the phase of rotation of the motor, and wherein the phase-frequency signal is processed to generate the drive signal, andwherein the control circuitry comprises an integration circuit, which receives and integrates the phase-frequency signal to generate a modified phase-frequency signal, responsive to the phase-frequency signal and the feedback signal, wherein the modified phase-frequency signal is characterized by a second-order astatism.