Search

CN-117478020-B - Method and system for determining rotor position offset of motor

CN117478020BCN 117478020 BCN117478020 BCN 117478020BCN-117478020-B

Abstract

A method of calibrating an electric machine to determine an angular offset between a position indicated by a motor sensor and an actual rotor position includes the steps of supplying current to a stator winding, identifying a quadrant of the rotor in which a rotor pole is located, approximating a line between a torque value measured at a lower angular boundary of the identified quadrant and a torque value measured at an upper angular boundary of the identified quadrant, and determining the angular offset by locating an angular position in which the torque applied by the rotor is zero.

Inventors

  • S. Barral
  • A. Cather
  • B.P. Davis

Assignees

  • 博格华纳公司

Dates

Publication Date
20260505
Application Date
20230726
Priority Date
20220727

Claims (15)

  1. 1. A method of calibrating an electric machine to determine an angular offset between a position indicated by a motor sensor and an actual rotor position, comprising the steps of: (a) Supplying current to the stator winding; (b) Identifying a quadrant of the rotor in which the rotor pole is located; (c) Approximating a line between the torque value measured at the lower corner boundary of the identified quadrant and the torque value measured at the upper corner boundary of the identified quadrant, and (D) The angular offset is determined by locating an angular position where the torque applied by the rotor is zero.
  2. 2. The method of calibrating an electric machine of claim 1, wherein the current supplied to the stator winding is a constant amount.
  3. 3. A method of calibrating an electric machine according to claim 1, wherein steps (a) - (d) are carried out by a load cell.
  4. 4. The method of calibrating an electric machine of claim 1, wherein step (b) further comprises measuring a first torque value at a first angular offset position and measuring a second torque value at a second angular position.
  5. 5. The method of calibrating a motor of claim 4, wherein the first angular offset position is at 90 degrees and the second angular position is at 180 degrees.
  6. 6. The method of calibrating an electric machine of claim 1, further comprising the step of storing the angular offset in a control system.
  7. 7. A method of calibrating an electric machine to determine an angular offset between a position indicated by a motor sensor and an actual rotor position, comprising the steps of: (a) Supplying current to the stator winding; (b) Identifying a quadrant of the rotor in which the rotor pole is located; (c) Determining an initial angular offset position by approximating a line between a torque value measured at a lower angular boundary of the identified quadrant and a torque value measured at an upper angular boundary of the identified quadrant, and (D) Performing a split search to determine a final angular offset by locating an angular position along the approximated line where torque applied by the rotor is zero to refine the initial angular offset position; (e) The angular offset is stored in a control system.
  8. 8. The method of calibrating an electric machine of claim 7, wherein the current supplied to the stator winding is a constant amount.
  9. 9. The method of calibrating a motor of claim 7, wherein steps (a) - (d) are performed by a load cell.
  10. 10. The method of calibrating a motor of claim 7, wherein step (b) further comprises measuring a first torque value at a first angular position and measuring a second torque value at a second angular position.
  11. 11. The method of calibrating a motor of claim 10, wherein the first angular position is at 90 degrees and the second angular position is at 180 degrees.
  12. 12. A system configured to calibrate an electric machine to determine an angular offset between a position indicated by a motor sensor and an actual rotor position, comprising: A controller, wherein the controller includes a non-volatile memory and is programmed to supply current to a stator winding, identify a quadrant of a rotor in which a rotor pole is located, approximate a line between a torque value measured at a lower corner boundary of the identified quadrant and a torque value measured at an upper corner boundary of the identified quadrant to determine an initial offset position value, and determine a final angular offset position by locating an angular position along the approximated line where torque applied by the rotor is zero.
  13. 13. The system of claim 12, wherein the system comprises a load cell.
  14. 14. The system of claim 12, wherein the controller is a load cell controller.
  15. 15. The system of claim 12, further comprising a control system for controlling the motor.

Description

Method and system for determining rotor position offset of motor Technical Field The present application relates to electric machines and, more particularly, to determining a rotor position offset of a rotor included in a machine. Background An electric machine (also referred to as an electric motor) includes a stator having a plurality of windings, and a rotor angularly displaced relative to the stator in response to application of current to the windings by induction. The motor may exist in a variety of different designs or configurations. In some applications, a motor sensor may monitor the angular position of the rotor and/or the angular position of a motor shaft coupled to the rotor to determine the precise angular position of the rotor/motor shaft relative to the stator. However, the motor sensor may indicate an angular position of the rotor/motor shaft relative to the stator that is offset from the actual relative angular position of the rotor/motor shaft relative to the stator. Disclosure of Invention In one implementation, a method of calibrating an electric machine to determine an angular offset between a position indicated by a motor sensor and an actual rotor position includes supplying current to a stator winding, identifying a quadrant of the rotor in which rotor poles are located, approximating a line between a torque value measured at a lower angular boundary of the identified quadrant and a torque value measured at an upper angular boundary of the identified quadrant, and determining the angular offset by locating an angular position in which torque applied by the rotor is zero. In another implementation, a method of calibrating an electric machine to determine an angular offset between a position indicated by a motor sensor and an actual rotor position includes supplying current to a stator winding, identifying a quadrant of the rotor in which rotor poles are located, approximating a line between a torque value measured at a lower angular boundary of the identified quadrant and a torque value measured at an upper angular boundary of the identified quadrant, and performing a split search (bi-section search) to determine the angular offset by locating an angular position along the approximated line where the torque applied by the rotor is zero, determining an initial angular offset position by approximating a line between a torque value measured at a lower angular boundary of the identified quadrant and a torque value measured at an upper angular boundary of the identified quadrant, performing a split search to determine a final angular offset by locating an angular position along the approximated line where the torque applied by the rotor is zero to improve the initial angular offset position, and storing the angular offset in a control system. In yet another implementation, the system is configured to calibrate the electric machine to determine an angular offset between a position indicated by the motor sensor and an actual rotor position and includes a controller, wherein the controller includes a non-volatile memory and is programmed to supply current to the stator windings, identify a quadrant of the rotor in which the rotor poles are located, approximate a line between a torque value measured at a lower angular boundary of the identified quadrant and a torque value measured at an upper angular boundary of the identified quadrant to determine an initial offset position value, and determine a final angular offset position by locating an angular position along the approximated line where torque applied by the rotor is zero. Drawings FIG. 1 is a diagram depicting an implementation of a system using an electric motor; FIG. 2 is a diagram depicting an implementation of a calibration system capable of calibrating a motor; FIG. 3 is a flow chart depicting an implementation of a method of calibrating a motor; FIG. 4 is a flow chart depicting a portion of an implementation of a method of calibrating a motor; FIG. 5 is a flow chart depicting a portion of an implementation of a method of calibrating a motor; FIG. 6 is a table depicting a portion of an implementation of a method of calibrating a motor, and Fig. 7 is a flow chart depicting a portion of an implementation of a method of calibrating a motor. Detailed Description The electric machine includes a stator having a plurality of stator windings and a rotor angularly displaced relative to the stator in response to application of current to the stator windings. The system is able to determine an angular offset between the rotor angular position indicated by the motor sensor and the actual rotor angular position. That is, the poles of the rotor may be at different angular positions than indicated by the motor sensor, and the angular difference may be referred to as an angular offset. The determination of the angular offset can be accomplished as part of a motor calibration that applies current to the stator windings at a known or fixed current l