Electric Motor Phase Control System

• US 20150084558A1
• Filed: 09/26/2013
• Published: 03/26/2015
• Est. Priority Date: 09/26/2013
• Status: Active Grant

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Benson, Christopher Pete, Cameron, Douglas C.
• Granted Patent: US 9,130,494 B2
• Time in Patent Office: Days
• US Class Current: 318/400.13
• CPC Class Codes: H02P 25/089 Sensorless control direct torque control H02P23/30
• CPC Class Codes: H02P 6/157 wherein the commutation is function of electro-magnetic force [EMF]
• CPC Class Codes: H02P 6/182 using back-emf in windings

Abstract

A method and apparatus for controlling an electric motor. A controller is configured to identify a start time for a signal based on a back electromotive force present in an electric motor during operation of the electric motor. The start time is for a position of a rotor relative to a group of coils. The controller is further configured to send the signal to the group of coils using the start time identified. An effect of the back electromotive force on the signal is reduced.

Claims

1. An apparatus comprising:

a controller configured to identify a start time for a signal based on a back electromotive force present in an electric motor during operation of the electric motor, wherein the start time is for a position of a rotor relative to a group of coils; and

send the signal to the group of coils using the start time identified, wherein an effect of the back electromotive force on the signal is reduced.

2. The apparatus of claim 1, wherein the signal is a current that has a waveform with a number of characteristics based on the start time and the back electromotive force in the electric motor.

3. The apparatus of claim 2, wherein the waveform for the current has a desired amplitude over a period of time based on a selection of the start time.

4. The apparatus of claim 3, wherein the desired amplitude is substantially equal to a commanded amplitude for the current over the period of time.

5. The apparatus of claim 1 further comprising:

a sensor system configured to generate information about the back electromotive force and send the information to the controller.

6. The apparatus of claim 5, wherein the sensor system is configured to measure a current in the group of coils to generate the information about the back electromotive force.

7. The apparatus of claim 1, wherein the controller is configured to change the start time based on a change in the back electromotive force.

8. The apparatus of claim 1, wherein the signal is a current in the electric motor and has a waveform and the controller is configured to identify a first area under the waveform, identify a second area under a commanded waveform resulting from a commanded current for the electric motor, and change the start time based on a difference between the first area and the second area.

9. The apparatus of claim 8, wherein the controller is configured to advance the start time to an earlier start time if the first area is less than the second area by a selected amount.

10. The apparatus of claim 8, wherein the controller is configured to divide the waveform into segments and identify an area under the segments to identify the first area.

11. The apparatus of claim 1, wherein the electric motor is selected from one of a brushless direct current electric motor, a reluctance motor, a variable reluctance motor, and a virtual ellipse device.

12. An electric motor system comprising:

an electric motor having a rotor and a group of coils;

a sensor system configured to generate information about a back electromotive force in the electric motor during operation of the electric motor; and

a controller configured to receive the information from the sensor system;

identify a start time for a current based on the back electromotive force present in the electric motor during operation of the electric motor using the information from the sensor system, wherein the start time is for a position of the rotor relative to the group of coils; and

send the current to the group of coils using the start time identified, wherein an effect of the back electromotive force on a signal is reduced.

13. The electric motor system of claim 12, wherein the current in the electric motor and has a waveform and the controller is configured to identify a first area under the waveform, identify a second area under a commanded waveform resulting from a commanded current for the electric motor, and change the start time based on a difference between the first area and the second area.

14. A method for controlling an electric motor, the method comprising:

identifying a start time for a signal based on a back electromotive force present in the electric motor during operation of the electric motor, wherein the start time is for a position of a rotor relative to a group of coils in the electric motor; and

sending the signal to the group of coils using the start time identified, wherein an effect of the back electromotive force on the signal is reduced.

15. The method of claim 14, wherein a waveform for a current has a desired amplitude over a period of time based on a selection of the start time.

16. The method of claim 15, wherein the desired amplitude is substantially equal to a commanded amplitude for the current over the period of time.

17. The method of claim 14 further comprising:

receiving information about the back electromotive force, wherein the information is a measurement of a current of the group of coils to generate the information about the back electromotive force.

18. The method of claim 14 further comprising:

changing the start time based on a change in the back electromotive force.

19. The method of claim 14, wherein the signal is a current in the electric motor and has a waveform further comprising:

identifying a first area under the waveform;

identifying a second area under a commanded waveform resulting from a commanded current for the electric motor; and

changing the start time based on a difference between the first area and the second area.

20. The method of claim 19, wherein the changing step comprises:

advancing the start time to an earlier start time if the first area is less than the second area by a selected amount.