A magnetic pole initial position detection device includes: a direct-current excitation command generation section configured to generate a first command for causing a constant excitation current with a current phase fixed to a first phase to flow through the synchronous motor; a torque-zero determination section configured to determine whether a torque generated in the rotor of the synchronous motor is zero when the excitation current based on the first command flows through the synchronous motor; and a magnetic pole initial position acquisition section configured to acquire the magnetic pole initial position of the rotor of the synchronous motor on a basis of a rotor actual position at or near a point in time when the torque-zero determination section determines that the torque is zero; a number of pole pairs of the synchronous motor; and an excitation phase during direct-current excitation under the first command.

A power tool is provided including a brushless motor having a stator defining a plurality of phases and a rotor. A power unit is provided including power switches operable to deliver power to the motor. A primary controller is interfaced with the power unit to output drive signals to drive the phases of the motor over a series of sectors of the rotor rotation. The primary controller measures a back-electromotive force voltage of the motor and transitions motor commutation from the present sector to the next sector based in relation to the back-EMF voltage. A second controller is provided to receive at least one of the drive signals, calculate a speed and/or direction of rotation of the motor from the drive signals, and take corrective action to cut off supply of power to the motor if it detects an overspeed condition or incorrect direction of rotation.

Methods and power tools for sensorless motor control. One embodiment provides a method for automatic control switching for driving a sensorless motor (150) of a power tool (100). The method includes determining, using a motor controller (224), a first load point based on user inputs (232) and determining, using the motor controller (224), a first motor control technique corresponding to the first load point. The method also includes driving the motor (150) based on the first motor control technique. The method further includes determining, using the motor controller (224), a change from the first load point to a second load point and determining, using the motor controller (224), a second motor control technique corresponding to the second load point. The method includes driving the motor (150) based on the second motor control technique.

The magnetic pole position of the rotor is estimated with high accuracy at the initial start of a three-phase motor of the sensorless system. Semiconductor device for driving and controlling the three-phase motor of the sensorless system have a detector connected to the three-phase output nodes of the inverter circuit and the virtual neutral point (or neutral point), and detecting a voltage generated in the output node of the non-energized phase of the three-phase. Controller applies the initial drive voltage by the inverter circuit to any two phases of the three-phase motor based on the estimated position of the magnetic pole of the rotor in the stop state. Controller estimates the position of the rotor based on a difference voltage detected by the detector in a driving voltage applying period and a regeneration period immediately after or immediately before the driving voltage applying period.

Methods and power tools for sensorless motor control. One embodiment provides a method for automatic control switching for driving a sensorless motor (150) of a power tool (100). The method includes determining, using a motor controller (224), a first load point based on user inputs (232) and determining, using the motor controller (224), a first motor control technique corresponding to the first load point. The method also includes driving the motor (150) based on the first motor control technique. The method further includes determining, using the motor controller (224), a change from the first load point to a second load point and determining, using the motor controller (224), a second motor control technique corresponding to the second load point. The method includes driving the motor (150) based on the second motor control technique.

Provided are a motor rotation angle measurement device and method. The device may comprise: a signal conditioning circuit, configured to receive a three-phase output voltage of a motor and separately generate three square-wave signals; and a processor, configured to generate a six-multiplying frequency pulse whenever jumping of any one of the three square-wave signals, is detected in a rotation period of a motor, generate compensation pulses between the current six-multiplying frequency pulse and a next six-multiplying frequency pulse based on a time interval between the current six-multiplying frequency pulse and a previous six-multiplying frequency pulse and a preset compensation subdivision coefficient k, and accumulate the number of the compensation pulses, wherein the number of the compensation pulses is related to the rotation angle of the motor.

The present invention improves performance of a motor control device. A slave device (90) includes: an inverter (73) configured to drive a motor (74); and a control section (10) configured to control the motor (74) via the inverter (73). The control section (10) includes: a feedback signal obtaining section configured to obtain a feedback signal indicative of a predetermined physical quantity corresponding to an operating state of the motor (74); a communication section (120) configured to communicate with a PLC (100); and a PWM signal output section (130) configured to supply a motor driving signal to the inverter (73). The control section (10) is implemented by a single IC chip.

In a motor control device, when estimating an initial position of a magnetic pole of a rotor of a motor, a drive circuit continuously or intermittently applies a voltage to a stator winding at each of a plurality of energization angles while sequentially changing the energization angles, and at a voltage value and for an energization time period, the voltage value and the energization time period being set such that the rotor does not rotate. An initial position estimation unit calculates an estimated initial position of the magnetic pole of the rotor based on a phase angle of a trigonometric function curve that approximates a change of a γ-axis current Iγ with respect to each of the energization angles. The trigonometric function curve has a cycle equal to one electrical cycle of the motor.

A system includes a position sensor configured to detect positions of a rotor of a starter motor relative to the position sensor and to output signals indicating the detected positions and a controller configured to rotate the rotor to a plurality of predetermined positions relative to a stator of the starter motor, determine sensed positions of the rotor based on the signals output by the position sensor, and calculate an initial detected position of the rotor based on relationships between the determined sensed positions of the rotor and an expected angular distance between adjacent ones of the predetermined positions.

An electric motor includes: a rotor with a first number of permanent magnets, wherein each permanent magnet encompasses a first circular sector; a stator with a second number of pole feet, wherein a first group of coils is electrically connected via a first star point, wherein a second group of coils is electrically connected via a second star point to be conductive, wherein the second star point is electrically insulated from the first star point, wherein a coil of the first group of coils is arranged between two coils of the second group of coils; and a controller for applying drive signals to the first group of coils so as to provide the rotor with a torque with respect to the stator, and for applying a control signal that differs from the drive signals to at least one coil of the second group of coils.