# US 2022/0286018 A1 · Power tool and control method thereof

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- Number: US 2022/0286018 A1
- Document ID: US20220286018A1
- Status: Published application
- Kind: A1
- Application number: 17/751,251
- Filed: 2022-05-23
- Published: 2022-09-08
- Earliest claimed: 2019-12-31
- Assignees: Nanjing Chervon Industry Co., Ltd.
- Applicants: Nanjing Chervon Industry Co., Ltd.
- Inventors: Zhen Xu; Dezhong Yang; Yanqing Xu
- Web page: https://patentgrep.com/patent/US20220286018A1

## CPC

- B25F 5/00: Details or components of portable power-driven tools not particularly related to the operations performed and not otherwise provided for
- H02K 7/145: {Hand-held machine tool}
- B25F 5/02: Construction of casings, bodies or handles {(B25F5/006, B25F5/008 take precedence)}
- H02K 11/33: Drive circuits, e.g. power electronics (H02K11/38 takes precedence)
- H02P 6/08: Arrangements for controlling the speed or torque of a single motor (H02P6/10, H02P6/28 take precedence)
- H02P 21/14: Estimation or adaptation of machine parameters, e.g. flux, current or voltage
- H02P 21/20: Estimation of torque
- H02P 21/22: Current control, e.g. using a current control loop
- H02P 27/085: {wherein the PWM mode is adapted on the running conditions of the motor, e.g. the switching frequency}
- B24B 23/028: {Angle tools}
- B25F: COMBINATION OR MULTI-PURPOSE TOOLS NOT OTHERWISE PROVIDED FOR; DETAILS OR COMPONENTS OF PORTABLE POWER-DRIVEN TOOLS NOT PARTICULARLY RELATED TO THE OPERATIONS PERFORMED AND NOT OTHERWISE PROVIDED FOR {(machines or arrangements of machines for performing specified combinations of different metal-working operations not covered by a single other subclass B23P23/00 and subgroups)}
- H02K: DYNAMO-ELECTRIC MACHINES (dynamo-electric relays H01H53/00; conversion of DC or AC input power into surge output power {H03K3/53})
- H02P: CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- B24B: MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING (grinding of gear teeth B23F, of screw-threads B23G1/36; by electro-erosion B23H; abrasive or related blasting B24C; tools for grinding, buffing or sharpening B24D; polishing compositions C09G1/00; abrasives C09K3/14; electrolytic etching or polishing C25F3/00; grinding arrangements for use on assembled railway tracks E01B31/17); DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS

## Abstract

A power tool includes a functional element, a motor, a power supply module, a driver circuit, and a control module. The control module is electrically connected to the driver circuit and configured to output a control signal to the driver circuit to control the driver circuit. The control module is configured to: in the case where the power tool is in a first operation stage, control the driver circuit in a first control mode so that a voltage of the motor varies with a rotor position of the motor in a square wave; and in the case where the power tool is in a second operation stage, control the driver circuit in a second control mode so that the voltage of the motor varies with the rotor position of the motor in a sine wave or a saddle wave.

## Claims

### Claim 1

A power tool, comprising:
a functional element;
a motor configured to drive the functional element to rotate, wherein the motor comprises a stator and a rotor;
a power supply module configured to supply power to the motor;
a driver circuit electrically connected to the motor and the power supply module and configured to apply a voltage of the power supply module to the motor; and
a control module electrically connected to the driver circuit and configured to output a control signal to the driver circuit to control the driver circuit, wherein the control module is configured to:
control the driver circuit in a first control mode so that a voltage of the motor varies with the position of the rotor of the motor in a square wave when the power tool is in a first operation stage; and
control the driver circuit in a second control mode so that the voltage of the motor varies with the position of the rotor of the motor in a sine wave or a saddle wave when the power tool is in a second operation stage.

### Claim 2 (depends on 1)

The power tool of claim 1, wherein the control module is configured to determine whether the power tool is in the first operation stage or the second operation stage according to a load-related parameter of the motor.

### Claim 3 (depends on 2)

The power tool of claim 2, wherein the load-related parameter of the motor comprises at least one of a current of the motor, a rotational speed of the motor, a torque of the motor, or an acceleration of the power tool.

### Claim 4 (depends on 1)

The power tool of claim 1, wherein the control module is configured to determine that the power tool is in the second operation stage and to be switched from the first control mode to the second control mode when a rotational speed of the motor is less than or equal to a first preset rotational speed threshold and a current of the motor is greater than or equal to a first preset current threshold.

### Claim 5 (depends on 4)

The power tool of claim 4, wherein the control module is configured to determine that the power tool is in the first operation stage and to be switched from the second control mode to the first control mode when the rotational speed of the motor is greater than or equal to a second preset rotational speed threshold and the current of the motor is less than or equal to a second preset current threshold.

### Claim 6 (depends on 5)

The power tool of claim 5, wherein the second preset current threshold is less than the first preset current threshold and the second preset rotational speed threshold is greater than the first preset rotational speed threshold.

### Claim 7 (depends on 14)

The power tool of claim 14, wherein the control module is configured to:
in the first control mode, output a first PWM control signal to the driver circuit; and
in the second control mode, output a second PWM control signal to the driver circuit;
wherein a duty cycle of the second PWM signal varies with the position of the rotor of the motor.

### Claim 8 (depends on 7)

The power tool of claim 7, wherein the control module is configured to:
perform a switching process before switching from the first control mode to the second control mode; and
in the switching process, suspend output the first PWM control signal to the driver circuit so that the motor stops driving.

### Claim 9 (depends on 8)

The power tool of claim 8, wherein the control module is configured to start to perform the switching process at a preset position of the rotor.

### Claim 10 (depends on 8)

The power tool of claim 8, wherein a variation of the rotational speed of the motor before and after the switching process is less than a preset threshold.

### Claim 11 (depends on 8)

The power tool of claim 8, wherein the control module is configured to:
in the switching process, acquire a switched initial duty cycle of the second PWM control signal according to a preset duration, the rotational speed of the motor, the position of the rotor of the motor, and a bus current or bus voltage of the motor.

### Claim 12 (depends on 11)

The power tool of claim 11, wherein the preset duration is a duration during which the control module performs the switching process.

### Claim 13 (depends on 1)

The power tool of claim 1, wherein the first operation stage is a motor driving stage of the power tool and the second operation stage is a motor braking stage of the power tool.

### Claim 14 (depends on 13)

The power tool of claim 13, wherein the first operation stage comprises one or more of a light-load operation stage, a medium-load operation stage, or a heavy-load operation stage

### Claim 15 (depends on 13)

The power tool of claim 13, wherein the control module is switched to the second control mode from the first control mode during braking.

### Claim 16

A control method of a power tool comprised of a motor, a driver circuit configured to drive the motor, and a control module configured to control the driver circuit, the control method comprising:
determining whether the power tool is in a first operation stage or a second operation stage;
in a case where the power tool is in the first operation stage, controlling the driver circuit in a first control mode so that an input voltage of the motor varies with a position of a rotor of the motor in a square wave; and
in a case where the power tool is in the second operation stage, controlling the driver circuit in a second control mode so that the input voltage of the motor varies with the position of the rotor of the motor in a sine wave or a saddle wave.

### Claim 17 (depends on 16)

The control method of a power tool of claim 16, wherein determining whether the power tool is in the first operation stage or the second operation stage is based on a load-related parameter of the motor.

### Claim 18 (depends on 17)

The control method of a power tool of claim 17, wherein the load-related parameter of the motor comprises at least one of a current of the motor, a rotational speed of the motor, a torque of the motor, or an acceleration of the power tool.

### Claim 19 (depends on 16)

The control method of a power tool of claim 16, wherein, in a case where a rotational speed of the motor is less than or equal to a first preset rotational speed threshold and a current of the motor is greater than or equal to a first preset current threshold, the power tool is determined to be in the second operation stage and the method further comprises switching the control module from the first control mode to the second control mode.

### Claim 20 (depends on 16)

The control method of a power tool of claim 16, wherein, in a case where the rotational speed of the motor is greater than or equal to a second preset rotational speed threshold and the current of the motor is less than or equal to a second preset current threshold, the power tool is determined to be in the first operation stage and the method further comprises switching the control module from the second control mode to the first control mode.