A speed estimating device for an AC motor includes: a model deviation computing unit computing a model deviation based on a voltage, a current, and an estimated angular velocity of the AC motor; a first angular velocity estimating unit computing a first estimated angular velocity based on the model deviation; a second angular velocity estimating unit computing a second estimated angular velocity differing from the first estimated angular velocity in frequency, based on the model deviation; a compensation phase computing unit computing a compensation phase based on a disturbance frequency; and an estimated angular velocity calculator computing an estimated angular velocity of the AC motor based on the first estimated angular velocity and the second estimated angular velocity. Either one of the first estimated angular velocity and the second estimated angular velocity is computed based on the compensation phase.

A speed estimating device for an AC motor includes: a model deviation computing unit computing a model deviation based on a voltage, a current, and an estimated angular velocity of the AC motor; a first angular velocity estimating unit computing a first estimated angular velocity based on the model deviation; a second angular velocity estimating unit computing a second estimated angular velocity differing from the first estimated angular velocity in frequency, based on the model deviation; a compensation phase computing unit computing a compensation phase based on a disturbance frequency; and an estimated angular velocity calculator computing an estimated angular velocity of the AC motor based on the first estimated angular velocity and the second estimated angular velocity. Either one of the first estimated angular velocity and the second estimated angular velocity is computed based on the compensation phase.

Described is a method of aligning a rotor of a polyphase synchronous motor having a permanent magnet rotor to a predetermined, selected, or specified rotor angle. The method comprises sensing or measuring the stator winding voltages/currents during synchronous operation of the motor. Based on the sensed or measured stator winding voltages/currents, a synchronously rotating reference frame vector voltage (V.sub.9) in the q-axis is determined as a product of stator winding resistance (R.sub.s) and stator winding current (i.sub.q) in the q-axis. Corresponding polyphase drive voltages for the synchronous motor for the predetermined, selected, or specified rotor angle (θ) are determined from the synchronously rotating reference frame vector voltage (V.sub.q). The polyphase drive voltages are applied to align the rotor on stopping at said predetermined, selected, or specified rotor angle (θ), The polyphase drive voltages are applied by suitable PWM drive signals.

This application provides a permanent-magnet synchronous machine control method and device, and a permanent-magnet synchronous machine control system. The method includes: obtaining a d-axis current i.sub.d and a q-axis current i.sub.q in a permanent-magnet synchronous machine control loop at a current moment; obtaining a fifth-order harmonic current i.sub.d5th and a seventh-order harmonic current i.sub.d7th in the d-axis current i.sub.d in the permanent-magnet synchronous machine control loop at the current moment, and a fifth-order harmonic current i.sub.q5th and a seventh-order harmonic current i.sub.q7th in the q-axis current i.sub.q in the permanent-magnet synchronous machine loop at the current moment; determining a d-axis current i.sub.d.sup.k+1 at a next moment in each switch state; determining a q-axis current i.sub.q.sup.k+1 at the next moment in each switch state based on the first current i.sub.d.sup.k, the second current i.sub.q.sup.k, and the second voltage in each switch state; and determining a control policy of the permanent-magnet synchronous machine.

Systems and methods for extracting motor operational state parameters from an electric motor for improved motor control and motor fault or failure detection are discussed. An exemplary system includes an excitation circuit to apply a drive voltage to an electric motor, and a processor circuit to measure a resulting winding current, extract a current waveform by oversampling the winding current in an entire PWM frame at a sampling rate higher than the PWM frequency, and fit the current waveform in the PWM period to a parametric model. The processor circuit can determine a motor operational state parameter using one or more of the applied drive voltage or the parametric model of the winding current.

Systems and methods for extracting motor operational state parameters from an electric motor for improved motor control and motor fault or failure detection are discussed. An exemplary system includes an excitation circuit to apply a drive voltage to an electric motor, and a processor circuit to measure a resulting winding current, extract a current waveform by oversampling the winding current in an entire PWM frame at a sampling rate higher than the PWM frequency, and fit the current waveform in the PWM period to a parametric model. The processor circuit can determine a motor operational state parameter using one or more of the applied drive voltage or the parametric model of the winding current.

Saliency tracking for brushless direct current (BLDC) motors and other permanent magnet synchronous motors (PMSMs) is provided. Embodiments generate an accurate estimate of rotor position for use in field-oriented control (FOC) of BLDC motors. In addition, a robust saliency tracking algorithm provides for the use of BLDC motors in low-speed high-torque applications without the need of external sensors. This enables sensorless application of higher level algorithms as well, such as servo control. In addition, accurate measurement of motor phase inductance and flux linkage can be provided without any additional equipment.

A motor controller includes an observer that estimates a y-axis electromotive force and a δ-axis electromotive force, during an idle time of a rotor of a motor. The motor controller includes a derivation unit that derives a phase difference between dq axes and yδ axes, from the y-axis electromotive force and the δ-axis electromotive force. The motor controller includes an estimation unit that estimates an idling state of the rotor from the phase difference. For example, the estimation unit estimates an idle velocity of the rotor from periodicity of the phase difference. For example, the estimation unit estimates a pole position of the rotor during the idle time, from the phase difference, a sign of the y-axis electromotive force, and a sign of the δ-axis electromotive force.

A motor controller includes an observer that estimates a y-axis electromotive force and a δ-axis electromotive force, during an idle time of a rotor of a motor. The motor controller includes a derivation unit that derives a phase difference between dq axes and yδ axes, from the y-axis electromotive force and the δ-axis electromotive force. The motor controller includes an estimation unit that estimates an idling state of the rotor from the phase difference. For example, the estimation unit estimates an idle velocity of the rotor from periodicity of the phase difference. For example, the estimation unit estimates a pole position of the rotor during the idle time, from the phase difference, a sign of the y-axis electromotive force, and a sign of the δ-axis electromotive force.

A system and method for controlling an electric machine via an inverter comprises an speed estimator that is configured to estimate a rotor speed of an electric motor to determine whether to control the inverter to operate the electric motor in a first mode or a second mode. For example, the first mode comprises a current-frequency control mode and the second mode comprises a back electromagnetic force (BEMF) mode. An electronic data processor or controller is configured to determine a first (current) command associated with a first mode of operating the electric motor, if the estimated rotor speed is a less than a speed threshold. The electronic data processor or controller is configured to determine a second (current) command associated with a second mode of operating the electric motor if the estimated rotor speed is equal to or greater than the speed threshold.