TECHNIQUES FOR CALIBRATING A LINEAR POSITION SENSOR

• US 20130293223A1
• Filed: 05/03/2013
• Published: 11/07/2013
• Est. Priority Date: 05/04/2012
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Youngner, Daniel W., Muldoon, Kelly P., Carlson, Douglas R.
• Granted Patent: US 9,372,062 B2
• Time in Patent Office: Days
• US Class Current: 324/207.12
• CPC Class Codes: A61B 2034/2051 Electromagnetic tracking systems
• CPC Class Codes: A61B 5/06 Devices, other than using radiation, for detecting or locating foreign bodies for removing same A61B17/50 ; determining position of probes within or on the body of the patient
• CPC Class Codes: G01B 7/023 for measuring distance between sensor and object G01B7/082 and G01B7/102 take precedence
• CPC Class Codes: G01B 7/14 for measuring distance or clearance between spaced objects or spaced apertures G01B7/30 takes precedence
• CPC Class Codes: G01D 18/00 Testing or calibrating apparatus or arrangements provided for in groups G01D1/00 - G01D15/00
• CPC Class Codes: G01D 5/145 influenced by the relative movement between the Hall device and magnetic fields see G01R33/06
• CPC Class Codes: G01D 5/2448 Correction of gain, threshold, offset or phase control
• CPC Class Codes: G01R 33/07 Hall effect devices

Abstract

Techniques are described for sensing a position of an object located within an enclosure over a position range. The techniques include generating an expected output signal of each of a plurality of magnetic field sensors disposed along an outer surface of the enclosure, receiving actual output signals from the sensors, wherein each actual output signal indicates a relative proximity of a magnetic target coupled to the object to the corresponding sensor. The techniques further include superimposing the expected output signal over the actual output signals, and iteratively shifting the expected output signal over position relative to the actual output signals and comparing the shifted expected output signal to the actual output signals, until the expected output signal compared to the actual output signals corresponds to a substantially minimized error parameter. The position of the object may then be determined based at least in part on the shifted expected output signal.

Claims

1. A method of sensing a position of an object located within an enclosure over a position range, the method comprising:

generating an expected output signal of each of a plurality of magnetic field sensors disposed along an outer surface of the enclosure between a first end and a second end of the enclosure;

receiving a plurality of actual output signals from the plurality of magnetic field sensors, wherein each of the plurality of actual output signals indicates a relative proximity of a magnetic target coupled to the object to the corresponding one of the plurality of magnetic field sensors;

superimposing the expected output signal over the plurality of actual output signals;

iteratively shifting the expected output signal over position relative to the plurality of actual output signals and comparing the shifted expected output signal to the plurality of actual output signals, until the shifted expected output signal compared to the plurality of actual output signals corresponds to a substantially minimized error parameter; and

determining the position of the object within the enclosure over the position range based at least in part on the shifted expected output signal.

2. The method of claim 1, wherein the expected output signal comprises a signal that is expected to be output by each of the plurality of magnetic field sensors as the magnetic target passes the respective one of the plurality of magnetic field sensors.

3. The method of claim 1, wherein generating the expected output signal comprises:

receiving a plurality of calibration output signals from the plurality of magnetic field sensors, wherein each of the plurality of calibration output signals indicates a relative proximity of the magnetic target to the corresponding one of the plurality of magnetic field sensors;

normalizing the plurality of calibration output signals such that each of the plurality of calibration output signals comprises a substantially same dynamic range;

shifting the normalized plurality of calibration output signals over position such that the signals of the normalized plurality of calibration output signals are substantially aligned relative to one another; and

averaging the shifted normalized plurality of calibration output signals so as to generate a single shifted normalized calibration output signal, wherein the single shifted normalized calibration output signal comprises the expected output signal.

4. The method of claim 3, wherein each of the plurality of calibration output signals indicates the relative proximity of the magnetic target to the corresponding one of the plurality of magnetic field sensors as the magnetic target passes the corresponding one of the plurality of magnetic field sensors.

5. The method of claim 1, wherein generating the expected output signal comprises generating the expected output signal based at least in part on a model of one or more of the enclosure, the object, the plurality of magnetic field sensors, the magnetic target, and relative positions thereof.

6. The method of claim 1, wherein generating the expected output signal comprises periodically generating the expected output signal.

7. The method of claim 1, wherein the position range comprises a substantially linear position range.

8. The method of claim 1, wherein the position range comprises a substantially angular position range.

9. The method of claim 1, wherein the magnetic target comprises one or more first magnetic poles and one or more second magnetic poles disposed on opposite ends of the magnetic target so as to generate a uniform magnetic field.

10. The method of claim 1, wherein the enclosure comprises an enclosure that is configured to attenuate a magnetic field passing through the enclosure.

11. The method of claim 10, wherein the enclosure comprises a hydraulic cylinder, and wherein the object comprises a portion of a movable piston disposed within the hydraulic cylinder.

12. The method of claim 11, wherein the object is positioned adjacent to a shaft of the movable piston.

13. The method of claim 11, wherein the object is positioned within the movable piston.

14. The method of claim 1, wherein the substantially minimized error parameter comprises a substantially minimized Least Squares (LS) error parameter, and wherein the substantially minimized LS error parameter corresponds to a substantially minimized sum of squared differences among the shifted expected output signal and the plurality of actual output signals.

15. The method of claim 14, wherein the substantially minimized error parameter further comprises a second substantially minimized Least Squares (LS) error parameter, and wherein the substantially minimized LS error parameter is a result of using an output of an initial substantially minimized Least Squares error calculation as input to a second substantially minimized least squares calculation.

16. The method of claim 1, wherein one or more of the plurality of magnetic field sensors comprise one or more magnetoresistive sensors.

17. A device for sensing a position of an object located within an enclosure over a position range, the method comprising:

means for generating an expected output signal of each of a plurality of magnetic field sensors disposed along an outer surface of the enclosure between a first end and a second end of the enclosure;

means for receiving a plurality of actual output signals from the plurality of magnetic field sensors, wherein each of the plurality of actual output signals indicates a relative proximity of a magnetic target coupled to the object to the corresponding one of the plurality of magnetic field sensors;

means for superimposing the expected output signal over the plurality of actual output signals;

means for iteratively shifting the expected output signal over position relative to the plurality of actual output signals and comparing the shifted expected output signal to the plurality of actual output signals, until the shifted expected output signal compared to the plurality of actual output signals corresponds to a substantially minimized error parameter; and

means for determining the position of the object within the enclosure over the position range based at least in part on the shifted expected output signal.

18. The device of claim 17, wherein the expected output signal comprises a signal that is expected to be output by each of the plurality of magnetic field sensors as the magnetic target passes the respective one of the plurality of magnetic field sensors.

19. The device of claim 17, wherein the means for generating the expected output signal comprises:

means for receiving a plurality of calibration output signals from the plurality of magnetic field sensors, wherein each of the plurality of calibration output signals indicates a relative proximity of the magnetic target to the corresponding one of the plurality of magnetic field sensors;

means for normalizing the plurality of calibration output signals such that each of the plurality of calibration output signals comprises a substantially same dynamic range;

means for shifting the normalized plurality of calibration output signals over position such that the signals of the normalized plurality of calibration output signals are substantially aligned relative to one another; and

means for averaging the shifted normalized plurality of calibration output signals so as to generate a single shifted normalized calibration output signal, wherein the single shifted normalized calibration output signal comprises the expected output signal.

20. An apparatus for sensing a position of an object located within an enclosure over a position range, the apparatus being configured to:

generate an expected output signal of each of a plurality of magnetic field sensors disposed along an outer surface of the enclosure between a first end and a second end of the enclosure;

receive a plurality of actual output signals from the plurality of magnetic field sensors, wherein each of the plurality of actual output signals indicates a relative proximity of a magnetic target coupled to the object to the corresponding one of the plurality of magnetic field sensors;

superimpose the expected output signal over the plurality of actual output signals;

iteratively shift the expected output signal over position relative to the plurality of actual output signals and comparing the shifted expected output signal to the plurality of actual output signals, until the shifted expected output signal compared to the plurality of actual output signals corresponds to a substantially minimized error parameter; and

determine the position of the object within the enclosure over the position range based at least in part on the shifted expected output signal.