System for determining the position of an object with respect to a magnetic field sources

• US 6,437,561 B1
• Filed: 11/17/1999
• Issued: 08/20/2002
• Est. Priority Date: 11/17/1999
• Status: Expired due to Term

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Bartingale, Steven R., Hamerly, Mike E., Haagenstad, Jeff D.
• Primary Examiner(s): Lefkowitz, Edward
• Assistant Examiner(s): Aurora, Reena
• Application Number:
  US09/441,475
• Time in Patent Office: 1,007 Days
• Field of Search: 180/167, 180/168, 180/169, 324/67, 324/326, 324/207-2-2, 340/901, 340/905, 340/941, 702/150
• US Class Current: 324/207.22
• CPC Class Codes: G05D 1/0263 using magnetic strips

Abstract

A detection system determines the position of an object moving along a first direction. The system includes a magnetic field source generating a magnetic field signal and a magnetic field detection system coupled to the object. The detection system includes a source interface module with magnetic field sensors positioned a known distance apart along a second direction different from the first direction. Each sensor detects the magnetic field generated by the magnetic field source and generates a magnetic field signal. A processing module processes the magnetic field intensity signal produced by the source interface module. The processing module generates data for each sensor in the source interface module, which is made up of points representing peak magnetic field and sensor location along the second direction. The points are compared to determine the distance of the object from the magnetic field source along the second direction.

Claims

1. A detection system for determining the position of an object moving along a first direction, the system comprising:

(a) a magnetic field source generating a magnetic field signal; and

(b) a magnetic field detection system coupled to the object, the detection system comprising;

(i) a source interface module comprising magnetic field sensors positioned a known distance apart along a second direction different from the first direction, wherein each sensor detects the magnetic field generated by the magnetic field source and generates a magnetic field signal,

(ii) a processing module that processes the magnetic field signal produced by the source interface module, wherein the processing module;

(1) determines magnetic field peak data from the magnetic field signal along the first direction for each sensor, and

(2) determines the relative difference between the magnetic field peak data for adjacent sensors to determine the distance of the object from the magnetic field source along the second direction.

2. The detection system as claimed in claim 1, wherein the magnetic field source generates an oscillating magnetic field signal.

3. The detection system as claimed in claim 1, wherein the source interface module comprises at least two magnetic field sensors.

4. The detection system as claimed in claim 1, wherein the source interface module comprises at least three magnetic field sensors.

5. The detection system as claimed in claim 1, wherein the first direction and the second direction are normal to each other.

6. The system of claim 5, wherein the determination of distance in step (b)(ii)(2) based on the relative differences is independent of the distance of the source interface module from the magnetic field source along a third direction substantially normal to the first and second directions.

7. The detection system as claimed in claim 1, wherein the magnetic field source is a magnetic tape.

8. The system of claim 7, wherein the magnetic tape is positioned along the first direction.

9. The system of claim 1, wherein the processing module determines, based on the relative differences between the magnetic field peak data, whether the source lies inside or outside the span of the source interface module.

10. The system of claim 9, wherein the processing module further applies one of an inside distance algorithm and an outside distance algorithm.

11. The system of claim 1, wherein the source interface module comprises a central magnetic field sensor, at least one first magnetic field sensor on a first side of the central magnetic field sensor, and at least one second magnetic field sensor on a second side of the central magnetic field sensor opposite the first side.

12. The system of claim 11, wherein in step (b)(ii)(2) the processing module determines a first slope of a first line between a data point for the central magnetic field sensor and a data point for the first magnetic field sensor, and determines a second slope of a second line between the data point for the central magnetic field sensor and a data point for the second magnetic field sensor.

13. The detection system of claim 12, wherein if the first slope and the second slope are opposite and of approximately equal magnitude, the processing module

determines a calibrated slope, and

evaluates the first slope, the second slope, and the magnetic field peak data using the calibrated slope to determine the distance of the object from the magnetic field source along the second direction.

14. A method for determining the position of an object moving along a first direction, the method comprising:

(a) generating a magnetic field signal in the first direction; and

(b) sensing the magnetic field signal with an array of magnetic field sensors positioned a known distance apart along a second direction different from the first direction, wherein each sensor detects the magnetic field signal and generates a magnetic field peak signal corresponding to the relative intensity of the detected field along the first direction,

(c) generating peak data from the magnetic field signal for each sensor in the processing module, and

(d) determining the relative difference between the magnetic field peak data for adjacent sensors to determine the distance of the object from the magnetic field source along the second direction.

15. The method as claimed in claim 14, wherein the magnetic field signal is an oscillating magnetic field signal.

16. The method as claimed in claim 14, wherein the sensor array comprises at least two magnetic field sensors.

17. The method of claim 14, wherein the second direction is normal to the first direction, and wherein the determination of distance in step (d) based on the relative differences is independent of the distance of the source interface module from the magnetic field source along a third direction substantially normal to the first and second directions.

18. The method of claim 17, wherein the processing module further applies one of an inside distance algorithm and an outside distance algorithm.

19. The method of claim 18, wherein in step (b)(ii)(2) the processing module determines a first slope of a first line between a data point for the central magnetic field sensor and a data point for the first magnetic field sensor, and determines a second slope of a second line between the data point for the central magnetic field sensor and a data point for the second magnetic field sensor.

20. The detection system as claimed in claim 19 wherein if the first slope and the second slope are opposite and of approximately equal magnitude, the processing module

determines a calibrated slope, and

evaluates the first slope, the second slope, and the magnetic field peak data using the calibrated slope to determine the distance of the object from the magnetic field source along the second direction.

21. The method as claimed in claim 14, wherein the source interface module comprises three magnetic field sensors.

22. The method as claimed in claim 21, wherein the sensors are aligned along the second direction.

23. The method of claim 14, wherein the processing module determines in step (d), based on the relative differences, whether the source lies inside or outside the span of the source interface module.

24. The method of claim 14, wherein the source interface module comprises a central magnetic field sensor, at least one first magnetic field sensor on a first side of the central magnetic field sensor, and at least one second magnetic field sensor on a second side of the central magnetic field sensor opposite the first side.

25. The method of claim 14, wherein the magnetic field source is a magnetic tape positioned along the first direction.

26. A detection system for determining the position of an object moving along a first direction using a magnetic field source generating a magnetic field signal, the system comprising:

(a) a magnetic field detection system coupled to the object, the detection system comprising;

(i) a source interface module comprising magnetic field sensors positioned a known distance apart along a second direction normal to the first direction, wherein each sensor detects the magnetic field generated by the magnetic field source and generates a magnetic field signal,

(ii) a processing module that processes the magnetic field signal produced by the source interface module, wherein the processing module;

(1) determines magnetic field peak data from the magnetic field signal along the first direction for each sensor, and

(2) determines the relative difference between the magnetic field peak data for adjacent sensors to determine the distance of the object from the magnetic field source along the second direction.