System and method of overcoming a dead-band in a switched reluctance motor

Patent metadata

Field	Value
Publication number	US-11811344-B2
Application number	US-202017132076-A
Country	US
Kind code	B2
Filing date	Dec 23, 2020
Priority date	Dec 23, 2020
Publication date	Nov 7, 2023
Grant date	Nov 7, 2023

Abstract

A work machine includes a frame, a traction system supporting the frame, a power source mounted on the frame, a switched reluctance motor, an inverter configured to control power to the motor from a power source, and a controller. The controller is configured to receive a signal indicating a desired torque and determine if the desired torque is between an upper threshold and a lower threshold. If the desired torque is between the upper threshold and the lower threshold, pulse width modulation is used to produce a PWM adjusted torque command, and the motor is commanded based on the PWM adjusted torque command. The PWM adjusted torque command is configured to cycle between the upper threshold and the lower threshold to produce the desired torque.

First claim

What is claimed is:

1. A work machine, comprising
a frame;
a traction system supporting the frame;
a power source mounted on the frame;
a switched reluctance motor;
an inverter configured to control power to the motor from the power source; and
a controller configured to:
receive a desired torque command signal indicating a desired torque,
determine if the desired torque is between an upper threshold and a lower threshold which corresponds to a positive and a negative torque load which produce a minimum current,
use pulse width modulation to produce a PWM adjusted torque command if the desired torque is between the upper threshold and the lower threshold, the PWM adjusted torque command being configured to cycle between the upper threshold and the lower threshold to produce the desired torque, and
command the motor based on the PWM adjusted torque command.

2. The work machine of claim 1 , wherein the PWM adjusted torque command is produced by generating a PWM reference signal and comparing that signal to the desired torque.

3. The work machine of claim 2 , wherein the PWM reference signal is a sawtooth wave.

4. The work machine of claim 1 , wherein the minimum current is required for sensor-less operation of the switched reluctance motor.

5. The work machine of claim 1 , wherein the upper threshold is 250 N·m and the lower threshold is −250 N·m.

6. The work machine of claim 1 , wherein the desired torque creates a sine wave.

7. An electric drive system for a work machine, comprising:
a switched reluctance motor;
an inverter configured to control power to the motor from a power source; and
a controller configured to:
receive a desired torque command signal indicating a desired torque,
determine if the desired torque is between an upper threshold and a lower threshold,
use pulse width modulation to produce a PWM adjusted torque command if the desired torque is between the upper threshold and the lower threshold, the PWM adjusted torque command being configured to cycle between the upper threshold and the lower threshold to produce the desired torque,
wherein the PWM adjusted torque command is produced by generating a PWM reference signal and comparing that signal to the desired torque, and

command the motor based on the PWM adjusted torque command.

8. The system of claim 7 , wherein the PWM reference signal is a sawtooth wave.

9. The system of claim 7 , wherein the PWM reference signal has a frequency of 500 Hz.

10. The system of claim 7 , wherein the upper threshold and a lower threshold correspond to a positive and a negative torque load which produce a minimum current.

11. The system of claim 7 , wherein the upper threshold is 250 N·m and the lower threshold is −250 N·m.

12. The system of claim 7 , wherein the desired torque creates a sine wave.

13. A method of overcoming a dead-band in a switched reluctance motor, comprising:
receiving a desired torque command signal indicating a desired torque;
determining if the desired torque is between an upper threshold and a lower threshold which correspond to a positive and a negative torque load which produce a minimum current required for sensor-less operation of the switched reluctance motor;
using pulse width modulation to produce a PWM adjusted torque command if the desired torque is between the upper threshold and the lower threshold, the PWM adjusted torque command being configured to cycle between the upper threshold and the lower threshold to produce the desired torque; and
commanding the motor based on the PWM adjusted torque command.

14. The method of claim 13 , wherein the PWM adjusted torque command is produced by generating a PWM reference signal and comparing that signal to the desired torque.

15. The method of claim 14 , wherein the PWM reference signal is a sawtooth wave.

16. The method of claim 14 , wherein the PWM reference signal has a frequency of 500 Hz.

17. The method of claim 13 , wherein the upper threshold is 250 N·m and the lower threshold is −250 N·m.

18. The method of claim 13 , wherein the desired torque creates a sine wave.

Assignees

• Caterpillar Inc

Inventors

• Gerdes Jesse R
• Sopko Thomas M
• Nino Baron Carlos E
• Wai Jackson
• Khalil Ahmed
• Abdul Sajan
• Ashfaq Amara
• Thorne James Michael

Classifications

• H02P23/30 Primary

  Direct torque control [DTC] or field acceleration method [FAM] · CPC title

• E02F9/207

  of the type electric propulsion units, e.g. electric motors or generators · CPC title

• 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

• 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

• E02F9/02

  Travelling-gear, e.g. associated with slewing gears ({drives therefor E02F9/20}; for motor vehicles B60B, B60G; undercarriages for locomotives or railroad cars B61F; track-laying vehicles B62D; for cranes B66C23/18) · CPC title