# US 11,305,412 B2 · Sensorless motor control for a power tool

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- Number: US 11,305,412 B2
- Document ID: US11305412B2
- Status: Granted
- Kind: B2
- Application number: 17/054,913
- Filed: 2020-04-15
- Published: 2021-07-29
- Granted: 2022-04-19
- Earliest claimed: 2019-04-15
- Assignees: Milwaukee Electric Tool Corporation
- Applicants: Milwaukee Electric Tool Corporation
- Inventors: Timothy R. Obermann; Douglas R. Fieldbinder; Alex Huber
- Web page: https://patentgrep.com/patent/US11305412B2

## 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 11/27: Devices for sensing current, or actuated thereby (overcurrent protection responsive to temperature of the machines or parts thereof, e.g. windings, H02K11/25)
- H02K 21/16: having annular armature cores with salient poles (with homopolar co-operation H02K21/20)
- H02P 6/181: {using different methods depending on the speed}
- H02P 6/182: using back-emf in windings
- H02P 6/183: {using an injected high frequency signal}
- H02P 21/18: Estimation of position or speed
- H02P 2203/03: Determination of the rotor position, e.g. initial rotor position, during standstill or low speed operation
- 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

## Abstract

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.

## Claims

### Claim 1

A power tool comprising;
a sensorless motor;
an inverter bridge configured to provide operating power to the sensorless motor; and
a motor controller coupled to the inverter bridge, the motor controller configured to
determine a first load point based on a user input, wherein the first load point is one selected from the group consisting of a high speed low torque application, a high speed high torque application, a low speed low torque application, and a low speed high torque application,
determine a first motor control technique corresponding to the first load point,
drive, using the inverter bridge, the sensorless motor based on the first motor control technique,
determine a change from the first load point to a second load point;
determine a second motor control technique corresponding to the second load point, and
drive, using the inverter bridge, the sensorless motor based on the second motor control technique.

### Claim 2 (depends on 1)

The power tool of claim 1, wherein the first motor control technique is one selected from the group consisting of: block commutation, sinusoidal control, and field oriented control.

### Claim 3 (depends on 1)

The power tool of claim 1, wherein the second motor control technique is one selected from the group consisting of: block commutation, sinusoidal control, and field oriented control.

### Claim 4 (depends on 1)

The power tool of claim 1, wherein the user inputs include one or more selected from the group consisting of: speed input from a trigger switch, a torque limit from a torque setting dial, a direction signal from a forward/reverse selector, and an operation mode from a mode selector.

### Claim 5 (depends on 1)

The power tool of claim 1, wherein the change from the first load point to the second load point is detected based on a change in the user input.

### Claim 6 (depends on 1)

The power tool of claim 1, wherein the second load point is one selected from the group consisting of a high speed low torque application, a high speed high torque application, a low speed low torque application, and a low speed high torque application.

### Claim 7 (depends on 1)

The power tool of claim 1, further comprising:
a coupling circuit; and
a decoupling circuit,
wherein the motor controller is further configured to
couple, using the coupling circuit, a high-frequency injection signal to the sensorless motor,
detect, using the decoupling circuit, motor response to the high-frequency injection signal,
determine rotor position based on motor response while maintaining a lower switch frequency on the inverter bridge, and
drive, using the inverter bridge, the sensorless motor based on detected rotor position.

### Claim 8

A method for automatic control switching for driving a sensorless motor of a power tool, the method comprising:
detecting, using a motor controller, a power tool operating parameter;
determining, using the motor controller, a load point of the power tool based on the power tool operating parameter, wherein the load point is one selected from the group consisting of a high speed low torque application, a high speed high torque application, a low speed low torque application, and a low speed high torque application;
determining, using the motor controller, a motor control technique corresponding to the load point; and
driving, using the motor controller, the sensorless motor based on the motor control technique.

### Claim 9 (depends on 8)

The method of claim 8, wherein the motor control technique is one selected from the group consisting of: block commutation, sinusoidal control, and field oriented control.

### Claim 10 (depends on 8)

The method of claim 8, wherein the power tool operating parameter is detected using one or more sensors.

### Claim 11 (depends on 10)

The method of claim 10, wherein the one or more sensors are used to detect one or more selected from the group consisting of: a motor current, a motor voltage, and a torque output.

### Claim 12 (depends on 8)

The method of claim 8, further comprising:
coupling, using a coupling circuit, a high-frequency injection signal to the sensorless motor,
detecting, using a decoupling circuit, motor response to the high-frequency injection signal,
determining, using the motor controller coupled to the decoupling circuit, rotor position based on motor response while maintaining a lower switch frequency on an inverter bridge, and
driving, using the motor controller and the inverter bridge, the sensorless motor based on detected rotor position.

### Claim 13

A power tool comprising;
a sensorless motor;
an inverter bridge configured to provide operating power to the sensorless motor; and
a motor controller coupled to the inverter bridge, the motor controller configured to
detect a power tool operating parameter;
determine a load point of the power tool based on the power tool operating parameter, wherein the load point is one selected from the group consisting of a high speed low torque application, a high speed high torque application, a low speed low torque application, and a low speed high torque application;
determine a motor control technique corresponding to the load point; and
drive, using the inverter bridge, the sensorless motor based on the motor control technique.

### Claim 14 (depends on 13)

The power tool of claim 13, wherein the motor control technique is one selected from the group consisting of: block commutation, sinusoidal control, and field oriented control.

### Claim 15 (depends on 13)

The power tool of claim 13, further comprising one or more sensors, wherein the power tool operating parameter is detected using the one or more sensors.

### Claim 16 (depends on 15)

The power tool of claim 15, wherein the one or more sensors are used to detect one or more selected from a group consisting of: a motor current, a motor voltage, and a torque output.

### Claim 17 (depends on 13)

The power tool of claim 13, further comprising:
a coupling circuit; and
a decoupling circuit,
wherein the motor controller is further configured to
couple, using the coupling circuit, high-frequency injection signal to the sensorless motor,
detect, using the decoupling circuit, motor response to the high-frequency injection signal,
determine rotor position based on motor response while maintaining a lower switch frequency on the inverter bridge, and
drive, using the inverter bridge, the sensorless motor based on detected rotor position.

### Claim 18

A power tool comprising;
a sensorless motor;
an inverter bridge configured to provide operating power to the sensorless motor; and
a motor controller coupled to the inverter bridge, the motor controller configured to:
determine a first load point based on a user input,
determine a first motor control technique corresponding to the first load point,
drive, using the inverter bridge, the sensorless motor based on the first motor control technique,
determine a change from the first load point to a second load point;
determine a second motor control technique corresponding to the second load point, wherein the second load point is one selected from the group consisting of a high speed low torque application, a high speed high torque application, a low speed low torque application, and a low speed high torque application, and
drive, using the inverter bridge, the sensorless motor based on the second motor control technique.

### Claim 19

A power tool comprising;
a sensorless motor;
an inverter bridge configured to provide operating power to the sensorless motor;
a coupling circuit;
a decoupling circuit; and
a motor controller coupled to the inverter bridge, the motor controller configured to:
determine a first load point based on a user input,
determine a first motor control technique corresponding to the first load point,
drive, using the inverter bridge, the sensorless motor based on the first motor control technique,
determine a change from the first load point to a second load point;
determine a second motor control technique corresponding to the second load point,
drive, using the inverter bridge, the sensorless motor based on the second motor control technique,
couple, using the coupling circuit, a high-frequency injection signal to the sensorless motor,
detect, using the decoupling circuit, motor response to the high-frequency injection signal,
determine rotor position based on motor response while maintaining a lower switch frequency on the inverter bridge, and
drive, using the inverter bridge, the sensorless motor based on detected rotor position.

### Claim 20

A method for automatic control switching for driving a sensorless motor of a power tool, the method comprising:
detecting, using a motor controller, a power tool operating parameter;
determining, using the motor controller, a load point of the power tool based on the power tool operating parameter;
determining, using the motor controller, a motor control technique corresponding to the load point;
driving, using the motor controller, the sensorless motor based on the motor control technique,
coupling, using a coupling circuit, a high-frequency injection signal to the sensorless motor,
detecting, using a decoupling circuit, motor response to the high-frequency injection signal,
determining, using the motor controller coupled to the decoupling circuit, rotor position based on motor response while maintaining a lower switch frequency on an inverter bridge, and
driving, using the motor controller and the inverter bridge, the sensorless motor based on detected rotor position.

### Claim 21

A power tool comprising;
a sensorless motor;
an inverter bridge configured to provide operating power to the sensorless motor;
a coupling circuit;
a decoupling circuit; and
a motor controller coupled to the inverter bridge, the motor controller configured to:
detect a power tool operating parameter,
determine a load point of the power tool based on the power tool operating parameter,
determine a motor control technique corresponding to the load point,
drive, using the inverter bridge, the sensorless motor based on the motor control technique,
couple, using the coupling circuit, high-frequency injection signal to the sensorless motor,
detect, using the decoupling circuit, motor response to the high-frequency injection signal,
determine rotor position based on motor response while maintaining a lower switch frequency on the inverter bridge, and
drive, using the inverter bridge, the sensorless motor based on detected rotor position.