A method for detecting failure of speed measurement of a multi-phase AC motor includes (1) sensing current drawn by the motor, (2) sensing voltage magnitude supplied to the motor, (3) measuring motor speed, (4) calculating motor speed, (5) determining whether the difference between the measured motor speed and the calculated motor speed is greater than a predetermined threshold, if the difference between the measured motor speed and the calculated motor speed is not greater than a predetermined threshold, repeating (1) through (5), if the difference between the measured motor speed and the calculated motor speed is greater than a predetermined threshold, indicating a fault, if a fault is indicated, performing a predetermined number of restart attempts, if the motor is successfully restarted, repeating (1) through (5), if the motor is not successfully restarted, indicating a restart failure.

A method for ascertaining, without an encoder, a rotational angle position of the rotor of a brushless DC motor, includes the steps of: detecting a voltage induced in a stator of the brushless DC motor; checking whether the voltage induced in the stator is lower than a threshold value; and if the induced voltage is lower than the threshold value, then ascertaining an initial rotational angle position of the rotor based on an Indirect Flux detection by Online Reactance Measurement, and subsequently updating the rotational angle position proceeding from the calculated initial rotational angle position using at least one continuous test signal.

A motor driver using a correcting mechanism on a sensed motor position is provided. A rotor position detector circuit senses a position of a rotor of a motor to output a commutation signal. A back electromotive force detector circuit detects a back electromotive force signal of the motor. An actual phase difference calculator circuit calculates a phase difference between the back electromotive force signal and the commutation signal as an actual phase difference. An error phase angle calculator circuit calculates a difference between the actual phase difference and a reference phase difference as an error phase angle. A motor driving circuit corrects the commutation signal according to the error phase angle. The motor driving circuit determines the position of the rotor of the motor to drive the motor according to the corrected commutation signal.

An abnormality determination means performs detection of abnormality of one of the pairs of detection means at a normal speed, and performs detection of abnormality of the other of the pairs at a speed not higher than the normal speed, and, when a sign of abnormality of the detection means is detected at the normal speed, a CPU performs switching to the other normal pair and continues control, and the abnormality determination means performs detection of abnormality of the other normal pair at the normal speed, and meanwhile, continues to perform detection of abnormality of the abnormal pair at a speed not higher than the normal speed.

A motor controller for controlling a brushless DC motor is provided. The motor controller includes a vector control unit configured to perform a sensorless vector control on the brushless DC motor in accordance with an input command value; a storage portion configured to store time-series control target values so that an amount of rotation angle of the brushless DC motor transitions in a same manner as an expected pattern; and a command portion configured to input, to the vector control unit, the control target values serially as the command value.

A magnetic pole position detecting device for a synchronous motor includes: a storage unit for storing a reference magnetic pole position of the synchronous motor as a predetermined reference; a magnetic pole position detector for detecting the magnetic pole position of the synchronous motor when a predetermined condition is satisfied; and a determination unit for comparing the reference magnetic pole position stored in the storage unit with the magnetic pole position detected by the magnetic pole position detector to determine that detection of the magnetic pole position is abnormal when the difference between the two falls out of a predetermined range.

A circuit includes a processor that analyzes a pulse width modulated (PWM) signal feedback from a brushless DC motor to determine a transition between a mutual inductance zero crossing condition and a Back Electro Motive Force (BEMF) zero crossing condition of the brushless DC motor. A mutual inductance controller is executed by the processor to commutate the brushless DC motor at startup of the motor when the mutual inductance zero crossing condition is detected by the processor. A BEMF controller is executed by the processor to commutate the brushless DC motor after startup of the motor when the BEMF zero crossing condition is detected by the processor.

The invention relates to a method for operating a rotating electric machine (1) having a rotor (3), a polyphase excitation winding (5) and a commutation apparatus (9) for commutating excitation winding currents of the excitation winding (5) depending on rotor position values (R) for rotor positions of the rotor (3). First measurement values (A) for the rotor positions are detected by means of a first sensor apparatus (13) and second measurement values (B) for the rotor positions are detected by means of a second sensor apparatus (15). For the commutation of the excitation winding currents, the rotor position values (R) are formed from weighted mean values (M) of the first measurement values (A) and the second measurement values (B). In a first rotation speed range of rotor rotation speeds of the rotor (3), the first sensor apparatus (13) has a higher resolution of the rotor positions than the second sensor apparatus (15) and, in the first rotation speed range, the first measurement values (A) are given more weight than the second measurement values (B) when forming the weighted mean values (M).

A motor control system includes an estimator responsive to measured motor winding voltage and measured motor winding current to generate an estimated position signal indicative of an estimate of a position of the motor and/or an estimated speed signal indicative of an estimate of a speed of the motor. A diagnostic checker circuit compares the estimated position signal and/or the estimated speed signal to a respective one of an actual position of the motor or an actual speed of the motor.

An oil-pump motor drive apparatus includes a current detection unit for detecting each of multi-phase currents flowing through coils of a stator, a control unit for converting the detected multi-phase currents into a d-axis current Id and a q-axis current Iq, calculating a phase error between an actual rotational position of the rotor and an imaginary rotational position by comparing the d-axis current Id with a d-axis current command value Idref and comparing the q-axis current Iq with the d-axis current command value Idref, performing control so that the phase error gets closer to zero, and outputting voltage command values indicating voltages to be applied to respective phases of the brushless motor, to a motor drive circuit, in which the control unit sets the d-axis current command value Idref to a value larger than zero when the number of revolutions of the motor is smaller than a predetermined number.