Field-oriented sensorless brushless motor control in a power tool

Patent metadata

Field	Value
Publication number	US-11469697-B2
Application number	US-202016896504-A
Country	US
Kind code	B2
Filing date	Jun 9, 2020
Priority date	Jun 10, 2019
Publication date	Oct 11, 2022
Grant date	Oct 11, 2022

Abstract

A power tool is provided including a housing, a brushless motor disposed within the housing, a power switch circuit that supplies power from a power source to the brushless motor, and a controller configured to apply a drive signal to the power switch circuit to control the supply of power to the brushless motor. The controller is configured to receive at least one signal associated with a phase current of the motor, detect an angular position of the rotor based on the phase current of the motor within a variable speed range of zero to at least 15,000 rotations-per-minute (RPM), and control the drive signal based on the detected angular position of the rotor to electronically commutate the motor within a torque range of zero to at least 15 newton-meters (N.m.) and a power output of zero to at least 1500 watts.

First claim

The invention claimed is:

1. A power tool comprising:
a housing;
a brushless motor disposed within the housing, the motor comprising a stator having a plurality of windings and a rotor;
a power switch circuit that supplies power from a power source to the brushless motor; and
a controller configured to apply a drive signal to the power switch circuit to control the supply of power to the brushless motor, wherein the controller is configured to receive at least one signal associated with a phase current of the motor, detect an angular position of the rotor based on the phase current of the motor within a variable speed range of zero to at least 15,000 rotations-per-minute (RPM), and control the drive signal based on the detected angular position of the rotor to electronically commutate the motor within a torque range of zero to at least 15 newton-meters (N.m.) and a power output of zero to at least 1500 watts.

2. The power tool of claim 1 , wherein the controller is configured to apply a vector-space pulse-width modulation (VSPWM) control to the drive signal for field-orientated control of the brushless motor.

3. The power tool of claim 2 , wherein the controller is configured to compute a position difference between the detected angular position of the rotor and a target position associated with a target speed reference, generate an error-correction signal as a function of the computed position difference, and apply the VSPWM control accordingly.

4. The power tool of claim 1 , wherein the power switch circuit comprises a plurality of low-side switches, a plurality of high-side switches, and a shunt component to which the at least one signal associated with the phase current of the motor is coupled.

5. The power tool of claim 4 , wherein the shunt element is provided on an output node of the power switch circuit.

6. The power tool of claim 4 , wherein the shunt component is provided in series with one of the low-side switches.

7. The power tool of claim 1 , wherein the power switch circuit comprises a plurality of low-side switches and a plurality of high-side switches, wherein the at least one signal associated with the phase current of the motor is coupled to the plurality of low-side switches and the controller measures the motor phase current using an internal resistance of the plurality of low-side switches.

8. The power tool of claim 7 , wherein the controller is configured to determine an ON-state of the plurality of low-side switches and measure a shunt voltage of one of the low-side switches that in the ON-state to calculate the motor phase current.

9. The power tool of claim 1 , further comprising a secondary controller configured to determine at least one of a speed of the rotor or a rotational direction of the rotor and disable supply of power to the motor if the speed of the rotor exceeds a speed threshold or the rotational direction of the rotor is different from a target direction.

10. The power tool of claim 9 , wherein the secondary controller is configured to monitor at least one of a sequence or frequency of the phase current of the motor.

11. The power tool of claim 9 , wherein the secondary controller is configured to monitor at least one of a sequence or frequency of the drive signal.

12. The power tool of claim 9 , wherein the secondary controller is configured to monitor at least one of a sequence or frequency a back electromotive force (back-EMF) voltage of the motor.

13. The power tool of claim 1 , wherein the controller comprises a Cortex-M+processor core architecture.

14. The power tool of claim 1 , wherein for a motor speed below a speed threshold, the controller is configured to apply a high-frequency injection (HFI) step of injecting a plurality of voltage pulses to the motor and detecting corresponding high-frequency current components to determine the angular position of the rotor.

15. The power tool of claim 14 , wherein for the motor speed above the speed threshold, the controller is configured to apply a sliding-mode observer (SMO) step of estimating a back electromotive force (back-EMF) voltage of the motor based on the phase current of the motor and determining the angular position of the rotor based on the estimated back-EMF voltage.

16. A method of controlling a brushless motor in a power tool, the brushless motor including a stator having a plurality of windings and a rotor, the power tool including a controller and a power switch circuit configured to supply power from a power source to the brushless motor, the method being executed by the controller and comprising:
applying a drive signal to the power switch circuit to control the supply of power to the brushless motor;
receiving at least one signal associated with a phase current of the motor;
detecting an angular position of the rotor based on the phase current of the motor within a variable speed range of zero to at least 15,000 rotations-per-minute (RPM); and
controlling the drive signal based on the detected angular position of the rotor to electronically commutate the motor within a torque range of zero to at least 15 newton-meters (N.m.) and a power output of zero to at least 1500 watts.

17. The method of claim 16 , further comprising applying a vector-space pulse-width modulation (VSPWM) control to the drive signal for field-orientated control of the brushless motor.

18. The method of claim 17 , further comprising:
computing a position difference between the detected angular position of the rotor and a target position associated with a target speed reference;
generating an error-correction signal as a function of the computed position difference; and
applying the VSPWM control accordingly.

19. The method of claim 16 , further comprising, for a motor speed below a speed threshold, applying a high-frequency injection (HFI) step of injecting a plurality of voltage pulses to the motor and detecting corresponding high-frequency current components to determine the angular position of the rotor.

20. The method of claim 19 , further comprising, for the motor speed above the speed threshold, applying a sliding-mode observer (SMO) step of estimating a back electromotive force (back-EMF) voltage of the motor based on the phase current of the motor and determining the angular position of the rotor based on the estimated back-EMF voltage.

Assignees

• Black & Decker Inc

Inventors

• Yajurvedi Girish
• Ramezani Mehdi
• Forster Michael K
• Vanko John C
• Gottesman Tal
• Gokdere Levent

Classifications

• H02P27/12

  pulsing by guiding the flux vector, current vector or voltage vector on a circle or a closed curve, e.g. for direct torque control · CPC title

• H02P21/10 Primary

  Direct field-oriented control; Rotor flux feed-back control · CPC title

• H02P21/34

  Arrangements for starting · CPC title

• H02P3/22

  by short-circuit or resistive braking · CPC title

• H02P29/0241

  the fault being an overvoltage · CPC title