Power based pulse injection control for SR self sensing

Patent metadata

Field	Value
Publication number	US-11545922-B2
Application number	US-202117154832-A
Country	US
Kind code	B2
Filing date	Jan 21, 2021
Priority date	Jan 21, 2021
Publication date	Jan 3, 2023
Grant date	Jan 3, 2023

Abstract

Power based self-sensing of a rotor position of an SR motor at mid to high speeds and low torque is achieved by an SR motor control system by comparing the motor power to an injection maximum power. A position current pulse is injected to a stator pole in response to the motor power being less than the injection maximum power. An actual stator current created by the position current pulse is compared to an estimated stator current, and a stored estimated rotor position in a memory is updated to a new estimated rotor position if the actual stator current is not equal to the estimated stator current.

First claim

What is claimed is:

1. A work machine, comprising:
a power source;
a switched reluctance (SR) motor having a stator and a rotor;
an inverter operatively connected to the power source and the SR motor to control transfer of power from the power source to the SR motor; and
a controller operatively connected to the SR motor and the inverter, the controller being configured to:
calculate a motor power that is output by the SR motor,
compare the motor power to an injection maximum power,
determine an estimated stator current for the SR motor based on a position current of a position current pulse to be injected to a stator pole of the SR motor to estimate a rotor position in response to the motor power being less than the injection maximum power,
cause the inverter to inject the position current pulse with the position current to the stator pole of the SR motor in response to the motor power being less than the injection maximum power,
determine an actual stator current of the SR motor created by the position current pulse,
compare the actual stator current to the estimated stator current, and
set a stored estimated rotor position in a memory equal to a new estimated rotor position in response to determining that the actual stator current is not equal to the estimated stator current by an error amount that is greater than a predetermined error amount.

2. The work machine of claim 1 , wherein the controller is configured to:
determine an estimated rotor speed of the rotor of the SR motor;
compare the estimated rotor speed to an injection maximum rotor speed; and
execute the calculate motor power step in response to determining that the estimated rotor speed is greater than the injection maximum rotor speed.

3. The work machine of claim 2 , wherein the controller is configured to omit the calculate the motor power step in response to determining that the estimated rotor speed is less than the injection maximum rotor speed.

4. The work machine of claim 1 , wherein the controller is configured to:
determine an estimated rotor speed of the rotor of the SR motor;
determine a motor torque of the SR motor; and
calculate the motor power by multiplying the motor torque by the estimated rotor speed.

5. The work machine of claim 4 , wherein the controller is configured to determine the estimated rotor speed by reading the memory for a stored estimated rotor speed.

6. The work machine of claim 1 , wherein the controller is configured to:
determine the estimated stator current for the SR motor based on a command current of a command current pulse to be injected to the stator pole of the SR motor to estimate the rotor position in response to the motor power being greater than the injection maximum power;
cause the inverter to inject the command current pulse with the command current to the stator pole of the SR motor in response to the motor power being greater than the injection maximum power; and
determine the actual stator current of the SR motor created by the command current pulse.

7. The work machine of claim 6 , wherein the controller is configured to determine the actual stator current of the SR motor created by the command current pulse.

8. A method for self-sensing a rotor position of a rotor of a switched reluctance (SR) motor, comprising:
calculating a motor power that is output by the SR motor;
comparing the motor power to an injection maximum power;
determining an estimated stator current for the SR motor based on a position current of a position current pulse to be injected to a stator pole of the SR motor to estimate the rotor position in response to the motor power being less than the injection maximum power;
injecting the position current pulse with the position current to the stator pole of the SR motor in response to the motor power being less than the injection maximum power;
determining an actual stator current of the SR motor created by the position current pulse;
comparing the actual stator current to the estimated stator current; and
setting a stored estimated rotor position equal to a new estimated rotor position in response to determining that the actual stator current is not equal to the estimated stator current by an error amount that is greater than a predetermined error amount.

9. The method of claim 8 , comprising:
determining an estimated rotor speed of the rotor of the SR motor;
comparing the estimated rotor speed to an injection maximum rotor speed; and
executing the calculating the motor power step in response to determining that the estimated rotor speed is greater than the injection maximum rotor speed.

10. The method of claim 9 , comprising omitting the calculating the motor power step in response to determining that the estimated rotor speed is less than the injection maximum rotor speed.

11. The method of claim 8 , comprising:
determining an estimated rotor speed of the rotor of the SR motor; and
determining a motor torque of the SR motor,
wherein calculating the motor power comprises multiplying the motor torque by the estimated rotor speed.

12. The method of claim 11 , determining the estimated rotor speed comprises reading a memory for a stored estimated rotor speed.

13. The method of claim 8 , comprising:
determining the estimated stator current for the SR motor based on a command current of a command current pulse to be injected to the stator pole of the SR motor to estimate the rotor position in response to the motor power being greater than the injection maximum power;
injecting the command current pulse with the command current to the stator pole of the SR motor in response to the motor power being greater than the injection maximum power; and
determining the actual stator current of the SR motor created by the command current pulse.

14. The method of claim 13 , comprising determining the actual stator current of the SR motor created by the command current pulse.

15. An electric drive system for a work machine having a frame, a traction system supporting the frame, and a power source mounted on the frame, the electric drive system comprising:
a switched reluctance (SR) motor having a stator and a rotor;
an inverter operatively connected to the power source and the SR motor to control transfer of power from the power source to the SR motor;
a current sensor operatively connected to the SR motor; and
a controller operatively connected to the SR motor, the inverter and the current sensor, the controller being configured to:
calculate a motor power that is output by the SR motor,
compare the motor power to an injection maximum power,
determine an estimated stator current for the SR motor based on a position current of a position current pulse to be injected to a stator pole of the SR motor to estimate a rotor position in response to the motor power being less than the injection maximum power,
cause the inverter to inject the position current pulse with the position current to the stator pole of the SR motor in response to the motor power being less than the injection maximum power,
determine an actual stator current of the SR motor created by the position current pulse based on current sensor signals from the current sensor,
compare the actual stator current to the estimated stator current, and
set a stored estimated rotor position in a memory equal to a new estimated rotor position in response to determining that the actual stator current is not equal to the estimated stator current by an error amount that is greater than a predetermined error amount.

16. The electric drive system of claim 15 , wher

Assignees

• Caterpillar Inc

Inventors

• Gerdes Jesse Ray
• Thorne James Michael
• Khalil Ahmed
• Wai Jackson
• Abdul Sajan
• Ashfaq Amara

Classifications

• E02F3/7609

  Scraper blade mounted forwardly of the tractor on a pair of pivoting arms which are linked to the sides of the tractor, e.g. bulldozers · CPC title

• H02P2203/01

  Motor rotor position determination based on the detected or calculated phase inductance, e.g. for a Switched Reluctance Motor · CPC title

• H02P6/185 Primary

  using inductance sensing, e.g. pulse excitation · CPC title

• E02F3/841

  Devices for controlling and guiding the whole machine, e.g. by feeler elements and reference lines placed exteriorly of the machine (construction of roads E01C19/008) · CPC title

• H02P25/089 Primary

  Sensorless control (direct torque control H02P23/30) · CPC title