Method for reducing error in rotor speed measurements

Patent metadata

Field	Value
Publication number	US-2016291052-A1
Application number	US-201415035784-A
Country	US
Kind code	A1
Filing date	Nov 7, 2014
Priority date	Nov 11, 2013
Publication date	Oct 6, 2016
Grant date	—

Abstract

The method of reducing error in rotor speed measurement includes synchronously measuring a rotor having a target including at least one geometric imperfection. Time intervals for the passing of each tooth of a rotor are stored in a circular buffer memory array. Speed is always determined by extracting the time for a complete revolution, so that geometric imperfections and asymmetry of the rotating target do not influence the speed determination, which is always representing the average speed over the latest complete revolution.

First claim

What is claimed is:

1 . A method measuring rotor speed, comprising:
positioning a sensor opposite a target, said target including a plurality of features; measuring a period corresponding to time between each of said plurality of features on said target passing said sensor; establishing an array of said periods, said array including up to a preselected number of said periods; removing old periods from said array when new periods are added and said preselected number of periods is reached; calculating an average period from a subset of said periods in said array, said average period corresponding to one of a complete revolution or a multiple of complete revolutions; and, calculating rotational speed of a rotor from said average period.

2 . The method of claim 1 , wherein said target includes at least one geometric imperfection.

3 . The method of claim 2 further comprising compensating for said at least one geometric imperfection by averaging said periods from one of a complete revolution or a multiple of complete revolutions of said target.

4 . The method of claim 2 , wherein said geometric imperfection feature causes an inconsistency in measurement of said periods.

5 . The method of claim 2 , wherein said at least one geometric imperfection includes inconsistent angular spacing between adjacent said features.

6 . The method of claim 2 wherein said at least one geometric imperfection includes at least one of said features having inconsistent radial height.

7 . The method of claim 2 wherein said at least one geometric imperfection includes said target having an asymmetric center.

8 . The method of claim 1 , wherein said target is integral with said rotor.

9 . The method of claim 8 wherein a rotational speed of said target is equal to a rotational speed of said rotor.

10 . The method of claim 1 , wherein said target is connected to said rotor.

11 . The method of claim 10 , wherein a rotational speed of said target is proportional to said rotational speed of said rotor.

12 . The method of claim 1 , wherein said preselected number of said periods in said array is greater than or equal to N multiplied by a, where N is the number of said plurality of features on said target and a is the number of revolutions of said target to be considered for said average period.

13 . The method of claim 12 , wherein said average period comprises summing N multiplied by a number of said periods from said array then dividing by N multiplied by a.

14 . The method of claim 13 further comprising determining said average period with a rotor computer.

15 . The method of claim 14 further comprising computing a rotor speed in desired units with said average period by said rotor computer.

16 . The method of claim 1 further comprising continuously updating said array.

17 . A method measuring rotor speed, comprising:
positioning a sensor opposite a target, said target including a plurality of features wherein said features include at least one geometric imperfection; measuring a period corresponding to time between each of said plurality of features on said target passing said sensor; establishing an array of said periods, said array including up to a preselected number of said periods; removing old periods from said array when new periods are added and said preselected number of periods is reached; calculating an average period from a subset of said periods in said array, said average period corresponding to one of a complete revolution or a multiple of complete revolutions; and, calculating rotational speed of a rotor from said average period to compensate for said at least one geometric imperfection.

Assignees

• Gen Electric

Inventors

• Riolo Joseph Scott
• Bradford David Allen

Classifications

• G01P3/481 Primary

  of pulse signals · CPC title

• G01P3/488

  delivered by variable reluctance detectors · CPC title

• G01P3/489

  Digital circuits therefor · CPC title

• G01P21/02 Primary

  of speedometers · CPC title