A method and device for acquiring a rotor position based on a permanent magnet synchronous drive system. The permanent magnet synchronous drive system includes an inverter and a permanent magnet synchronous motor, wherein the initial speed of the permanent magnet synchronous motor is not zero. The method includes: controlling a bridge arm switch of an inverter periodically; collecting a three-phase current of the permanent magnet synchronous motor at a fixed time within each control period; and after the three-phase current is reversed, sending same to a phase-locked loop system to conduct processing, so as to obtain a phase angle of an induction potential vector, and according to the phase angle of the induction potential vector, acquiring a rotor position angle of the permanent magnet synchronous motor.

A motor control system and a motor control method are provided. The motor control method includes: coupling a brushless direct current (BLDC) motor of the motor device to the motor controller via at least one wire, wherein the motor controller provides power to the BLDC motor via the at least one wire; and coupling a sensor of the motor device to the motor controller via the at least one wire, wherein the sensor generates sensed data, wherein the sensed data is transmitted to the motor controller via the at least one wire.

A driver system operable to supply a drive signal to a motor includes a system input adapted to be coupled to an input voltage and a system output adapted to be coupled to the motor. The driver system includes a high-side transistor which has a first terminal coupled to the system input, a second terminal coupled to the system output, and has a control terminal. The driver system includes a low-side transistor which has a first terminal coupled to the system output, a second terminal coupled to a reference potential terminal, and has a control terminal. The driver system includes a low-side gate control circuit which provides a first level current responsive to a low-side digital control signal transitioning from a low state to a high state and provides a second level current if the output voltage is less than an upper reference voltage.

A driver system operable to supply a drive signal to a motor includes a system input adapted to be coupled to an input voltage and a system output adapted to be coupled to the motor. The driver system includes a high-side transistor which has a first terminal coupled to the system input, a second terminal coupled to the system output, and has a control terminal. The driver system includes a low-side transistor which has a first terminal coupled to the system output, a second terminal coupled to a reference potential terminal, and has a control terminal. The driver system includes a low-side gate control circuit which provides a first level current responsive to a low-side digital control signal transitioning from a low state to a high state and provides a second level current if the output voltage is less than an upper reference voltage.

In order to provide an electric tool with good operability that can extend the life of and suppress breakage of a switching element for controlling energization of a brushless motor, a control unit (50), after an operation switch (5) is turned off, does not immediately turn off an inverter circuit (43) (does not set the duty of a PWM signal to 0), and instead normally operates the inverter circuit (43) with a low-duty PWM signal and waits until a rotation speed of a brushless motor (6) reaches a predetermined rotation speed or less to turn off the inverter circuit (43) (to set the duty of the PWM signal to 0).

In order to provide an electric tool with good operability that can extend the life of and suppress breakage of a switching element for controlling energization of a brushless motor, a control unit (50), after an operation switch (5) is turned off, does not immediately turn off an inverter circuit (43) (does not set the duty of a PWM signal to 0), and instead normally operates the inverter circuit (43) with a low-duty PWM signal and waits until a rotation speed of a brushless motor (6) reaches a predetermined rotation speed or less to turn off the inverter circuit (43) (to set the duty of the PWM signal to 0).

A method for detecting an initial position of a rotor of a permanent magnet synchronous motor in a no-load environment can comprise the steps of: estimating a temporary initial position α′ by means of aligning a d axis; measuring a first voltage command which is output by performing velocity control within predetermined velocity ranges with respect to the forward direction of a motor on the basis of the temporary initial position α′; measuring a second voltage command which is output by performing velocity control within the predetermined velocity range with respect to the reverse direction of the motor on the basis of the temporary initial position α′; calculating respective variations of the first voltage command and second voltage command, and calculating a compensation angle α″; and calculating an initial position α of the rotor on the basis of the sum of the temporary initial position α′ and compensation angle α″.

A position estimation device acquires detection values of magnetic field strength at three or more locations of a rotor in a range where a rotor angle is less than one rotation. A section is selected based on a detection value of the magnetic field strength from predetermined sections for a pole pair number of the rotor. A feature amount calculator is provided to calculate feature amounts of a waveform of the magnetic field strength based on a combination of the detection values of the magnetic field strength according to the section selected. An estimator is provided to determine, for each segment associated with the section selected, whether or not a magnitude relationship of the feature amounts learned in advance coincides with a magnitude relationship of the feature amounts calculated, and estimating, as a rotation position of the rotor, the pole pair number associated with the segment having the same magnitude relationship.

A position estimation device acquires detection values of magnetic field strength at three or more locations of a rotor in a range where a rotor angle is less than one rotation. A section is selected based on a detection value of the magnetic field strength from predetermined sections for a pole pair number of the rotor. A feature amount calculator is provided to calculate feature amounts of a waveform of the magnetic field strength based on a combination of the detection values of the magnetic field strength according to the section selected. An estimator is provided to determine, for each segment associated with the section selected, whether or not a magnitude relationship of the feature amounts learned in advance coincides with a magnitude relationship of the feature amounts calculated, and estimating, as a rotation position of the rotor, the pole pair number associated with the segment having the same magnitude relationship.

A method for identifying a position of a multi-phase brushless motor includes applying a plurality of detection voltage pulses to the motor, each detection voltage pulse corresponding to a respective driving phase of the motor, measuring a time period associated with a current reaching a predetermined current limit for each applied detection voltage pulse, and identifying a driving phase associated with a shortest time period for the current to reach the predetermined current limit.