CA-3153018-C - CONTROLLING BRUSHLESS MOTOR COMMUTATION

Abstract

The present invention relates to a method of commutation control of a brushless DC (BLDC) motor. The method uses a controller to control the BLDC motor using a modified six-step commutation. The method adds six intermediate steps that overlap the six-step commutation. Each of the six steps overlap with preceding and following steps, resulting in six additional intermediate steps in which all three phases are active. By doubling the number of steps, current and torque will vary less over time compared with current solutions without increasing the size or changing the design of the motor.

Inventors

• Jason Genz
• Michael T. Rajzer
• Christoffer S. Fox
• Daniel Nitzsche

Assignees

• SNAP-ON INCORPORATED

Dates

Publication Date

20260505

Application Date

20220322

Priority Date

20220314

Claims (20)

1. What is claimed is: 1. A tool including an output and a brushless DC (BLDC) motor having multiple phases and that is adapted to drive the output, the tool comprising: a controller adapted to: control the motor using overlapped commutation by: controlling first high-side and first low-side switches corresponding to a first phase of the motor; controlling second high-side and second low-side switches corresponding to a second phase of the motor; and controlling third high-side and third low-side switches corresponding to a third phase of the motor; wherein the overlapped commutation includes first through twelfth steps, and the controller is adapted to cause the first, second, and third phases of the motor to be active during the second, fourth, sixth, eighth, tenth, and twelfth steps, and the controller is further adapted to vary an amount of overlapped commutation of the second, fourth, sixth, eighth, tenth, and twelfth steps.
2. 2. The tool of claim 1, wherein the controller is adapted to cause at least two of the first, second, and third high-side switches to be active during the fourth, eighth, and twelfth steps.
3. 3. The tool of claim 1, wherein the controller is adapted to cause at least two of the first, second, and third low-side switches to be active during the second, sixth, and tenth steps.
4. 4. The tool of claim 1, wherein the controller is adapted to cause the first high-side switch, the second low-side switch, and the third low-side switch to be active during the second step. 11
5. 5. The tool of claim 1, wherein the controller is adapted to cause the first high-side switch, the third high-side switch, and the second low-side switch to be active during the fourth step.
6. 6. The tool of claim 1, wherein the controller is adapted to cause the third high-side switch, the first low-side switch, and the second low-side switch to be active during the sixth step.
7. 7. The tool of claim 1, wherein the controller is adapted to cause the second high-side switch, the third high-side switch, and the first low-side switch to be active during the eighth step.
8. 8. The tool of claim 1, wherein the controller is adapted to cause the second high-side switch, the first low-side switch, and the third low-side switch to be active during the tenth step.
9. 9. The tool of claim 1, wherein the controller is adapted to cause the first high-side switch, the second high-side switch, and the third low-side switch to be active during the twelfth step.
10. 10. A method for controlling commutation of a brushless DC (BLDC) motor, wherein the motor has multiple phases, the method comprising: controlling first, second, and third high-side switches respectively corresponding to first, second, and third phases of the motor, and controlling first, second, and third low-side switches respectively corresponding to the first, second, and third phases of the motor using overlapped commutation, wherein the overlapped commutation includes first through twelfth steps; causing the first, second, and third phases of the motor to be active during the second, fourth, sixth, eighth, tenth, and twelfth steps; and varying an amount of overlapped commutation of the second, fourth, sixth, eighth, tenth, and twelfth steps.
11. 11. The method of claim 10, wherein causing the first, second, and third phases of the motor to be active during the second, fourth, sixth, eighth, tenth, and twelfth steps includes causing at 12 least two of the first, second, and third high-side switches to be active during the fourth, eighth, and twelfth steps.
12. 12. The method of claim 10, wherein causing the first, second, and third phases of the motor to be active during the second, fourth, sixth, eighth, tenth, and twelfth steps includes causing at least two of the first, second, and third low-side switches to be active during the second, sixth, and tenth steps.
13. 13. The method of claim 10, wherein causing the first, second, and third phases of the motor to be active during the second, fourth, sixth, eighth, tenth, and twelfth steps includes causing the first high-side switch, the second low-side switch, and the third low-side switch to be active during the second step.
14. 14. The method of claim 10, wherein causing the first, second, and third phases of the motor to be active during the second, fourth, sixth, eighth, tenth, and twelfth steps includes causing the first high-side switch, the third high-side switch, and the second low-side switch to be active during the fourth step.
15. 15. The method of claim 10, wherein causing the first, second, and third phases of the motor to be active during the second, fourth, sixth, eighth, tenth, and twelfth steps includes causing the third high-side switch, the first low-side switch, and the second low-side switch to be active during the sixth step.
16. 16. The method of claim 10, wherein causing the first, second, and third phases of the motor to be active during the second, fourth, sixth, eighth, tenth, and twelfth steps includes causing the second high-side switch, the third high-side switch, and the first low-side switch to be active during the eighth step. 13
17. 17. The method of claim 10, wherein causing the first, second, and third phases of the motor to be active during the second, fourth, sixth, eighth, tenth, and twelfth steps includes causing the second high-side switch, the first low-side switch, and the third low-side switch to be active during the tenth step.
18. 18. The method of claim 10, wherein causing the first, second, and third phases of the motor to be active during the second, fourth, sixth, eighth, tenth, and twelfth steps includes causing the first high-side switch, the second high-side switch, and the third low-side switch to be active during the twelfth step.
19. 19. A controller for a brushless DC (BLDC) motor having multiple phases, the controller comprising: a microprocessor adapted to: control first, second, and third high-side switches respectively corresponding to first, second, and third phases of the motor, and first, second, and third low-side switches respectively corresponding to the first, second, and third phases of the motor using overlapped commutation, wherein the overlapped commutation includes first through twelfth steps; during the first, third, fifth, seventh, ninth, and eleventh steps, cause one of the first, second, and third high-side switches to be active and one of the first, second, and third low-side switches to be active; and vary an amount of overlapped commutation of the second, fourth, sixth, eighth, tenth, and twelfth steps.
20. 20. The controller of claim 19, wherein the microprocessor is further adapted to: 14 cause the first high-side switch and the third low-side switch to be active during the first step; cause the first high side switch and the second low side switch to be active during the third step; cause the third high side switch and the second low side switch to be active during the fifth step; cause the third high side switch and the first low side switch to be active during the seventh step; cause the second high side switch and the first low side switch to be active during the ninth step; and cause the second high side switch and the third low side switch to be active during the eleventh step.

Description

CONTROLLING BRUSHLESS MOTOR COMMUTATION [0001] Technical Field of the Invention [0002] The present invention relates generally to electric motors, and more particularly to 5 commutation control of a brushless DC (BLDC) motor. Background of the Invention [0003] Power tools, such as, for example, motorized ratchet wrenches, drills, and drivers, driven by brushless DC (BLDC) motors are commonly used in automotive, industrial, and household applications to tighten and untighten work pieces, such as threaded fasteners, and to apply a 10 torque and/or angular displacement to a work piece, for example. BLDC motor commutation is typically implemented using a microcontroller or microprocessor computer. Controlling commutation with electronics and position feedback instead of brushes allows greater flexibility and capabilities not available with conventional brushed DC motors, including precise speed control, position control, and stepped operation for slow and fine motion control. 15 [0004] Many different techniques of commutation of three-phase brushless direct current (BLDC) motors are currently used. One known technique is a six-step commutation, which uses a position of a rotor of the motor to determine which pair of phases to turn on in order to spin the rotor. In each step of these six steps, only two phases are active. A positive bus voltage is applied to the first phase via a first phase high side switching element, and a negative bus voltage is 20 applied to the second phase via a second phase low side switching element resulting in a flow of Date Re!,ue/Date Received 2024-01-11 current through the coil(s) connecting the first and second phases. However, due to the coarse nature of six step commutation, large current and torque ripple (i.e., variations in torque production during shaft revolution) often occurs. Moreover, to increase the torque or speed output of the motor requires increasing the size or changing the design of the motor. Summary of the Invention [0005] The present invention relates broadly to commutation control of a BLDC motor for use with, for example, a power tool. While the present invention is described as being used with a BLDC motor for a power tool, it will be appreciated that the present invention can be used with a BLDC motor for any purpose or function. In an embodiment, a method of commutation control 10 uses a controller to control a BLDC motor using a modified six-step commutation, in which each of the six steps overlap with the preceding and following steps. The areas of overlap result in six additional intermediate steps in which all three phases are active. By doubling the number of steps, current and torque will vary less over time compared with current solutions without increasing the size or changing the design of the motor. Brief Description of the Drawings [0006] For the purpose of facilitating an understanding of the subject matter sought to be protected, there are illustrated in the accompanying drawings embodiments thereof, from an inspection of which, when considered in connection with the following description, the subject matter sought to be protected, its construction and operation, and many of its advantages should 20 be readily understood and appreciated. [0007] FIG. 1 is a perspective view of an exemplary power tool, such as a motorized ratchet tool, incorporating an embodiment of the present invention. 2 Date Re!fue/Date Received 2022-03-22 [0008] FIGs. 2 and 3 are block component diagrams of electronic components of an exemplar tool incorporating embodiments of the present invention. [0009] FIG. 4 is a schematic of an exemplar BLDC motor incorporating an embodiment of the present invention. 5 [0010] FIG. 5 is a chart illustrating an exemplary method of commutation control of a BLDC motor, according to an embodiment of the present invention. Detailed Description of the Invention [0011] While the present invention is susceptible of embodiments in many different forms, there is shown in the drawings, and will herein be described in detail, embodiments of the invention, 10 including a preferred embodiment, with the understanding that the present disclosure is to be considered as an exemplification of the principles of the present invention and is not intended to limit the broad aspect of the invention to any one or more embodiments illustrated herein. As used herein, the term "present invention" is not intended to limit the scope of the claimed invention, but is instead used to discuss exemplary embodiments of the invention for explanatory 15 purposes only. [0012] The present invention relates broadly to commutation control of a BLDC motor for use with, for example, a power tool. While the present invention is described as being used with a BLDC motor for a power tool, it will be appreciated that the present invention can be used with a BLDC motor for any purpose or function. In an embodiment, a method of commutation control 20 uses a controller to control a BLD