Sensor assembly and method for determining a magnetization direction of an indicator magnet

• US 9,057,629 B2
• Filed: 09/24/2012
• Issued: 06/16/2015
• Est. Priority Date: 03/25/2010
• Status: Active Grant

• Current Assignee: Fraunhofer Gesellschaft Zur Foerderung Der Angewandten Forsching E.V.
• Original Assignee: Fraunhofer Gesellschaft Zur Foerderung Der Angewandten Forsching E.V.
• Inventors: Hohe, Hans-Peter, Sauerer, Josef
• Primary Examiner(s): Aurora, Reena
• Application Number:
  US13/625,165
• Publication Number:
  US 20130027028A1
• Time in Patent Office: 995 Days
• Field of Search: 324/207.15, 324/207.22
• US Class Current: 1/1
• CPC Class Codes: G01D 5/145 influenced by the relative movement between the Hall device and magnetic fields see G01R33/06

Abstract

A sensor assembly for determining a magnetization direction of an indicator magnet with respect to the sensor assembly includes a first magnetic field sensor for detecting a first and a second magnetic field component with respect to a first and a second spatial direction, and a second magnetic field sensor for detecting a third and a fourth magnetic field component with respect to the second spatial direction, wherein the first and the second magnetic field sensor are spaced apart from one another. Further, the sensor assembly includes a processor that is implemented to combine the first and the second magnetic field component to obtain a first combination quantity, to combine the third and the fourth magnetic field component to obtain a second combination quantity, to determine a position of the indicator magnet and the magnetization direction.

Claims

1. A sensor assembly for determining a magnetization direction of an indicator magnet, comprising:

a first magnetic field sensor configured to detect a first magnetic field component of the indicator magnet with respect to a first spatial direction and a second magnetic field component of the indicator magnet with respect to a second spatial direction, wherein the first and second spatial directions are linearly independent spatial directions;

a second magnetic field sensor configured to detect a third magnetic field component of the indicator magnet with respect to the first spatial direction and a fourth magnetic field component of the indicator magnet with respect to the second spatial direction;

wherein the first magnetic field sensor and the second magnetic field sensor are arranged spaced apart from one another; and

a processor implemented to;

combine a first value derived from the first magnetic field component and a second value derived from the second magnetic field component to acquire a first combination result;

combine a third value derived from the third magnetic field component and a fourth value derived from the fourth magnetic field component to acquire a second combination result;

determine a position of the indicator magnet with respect to the sensor assembly based on a comparison of the first combination result and the second combination result; and

determine the magnetization direction based on the determined position of the indicator magnet with respect to the sensor assembly and on a sign of a detected magnetic field component with respect to the second spatial direction.

2. The sensor assembly according to claim 1, wherein the first magnetic field sensor and the second magnetic field sensor are implemented to each detect the first magnetic field component and the third magnetic field component in an axial direction and the second magnetic field component and the fourth magnetic field component in a radial direction with respect to a relative direction of movement of the indicator magnet with respect to the sensor assembly.

3. The sensor assembly according to claim 1, wherein the processor is implemented to determine a first position of the indicator magnet with respect to the sensor assembly, when a magnitude of the first combination quantity is greater than a magnitude of the second combination quantity, and to determine a second position of the indicator magnet with respect to the sensor assembly when the magnitude of the second combination quantity is greater than the magnitude of the first combination quantity.

4. The sensor assembly according to claim 3, wherein the processor is implemented to state, when the first position has been determined, a first magnetization direction at a positive sign of the second magnetic field component or the fourth magnetic field component, and to state a second magnetization direction when the second position has been determined, and to state, when the first position has been determined, the second magnetization direction at a negative sign of the second magnetic field component or the fourth magnetic field component, and to state the first magnetization direction when the second position has been determined.

5. The sensor assembly according to claim 1, wherein the processor is implemented to combine the first magnetic field component with the second magnetic field component and the third magnetic field component with the fourth magnetic field component, each in such a way that the magnitude of the first combination quantity represents a magnitude function and the magnitude of the second combination quantity represents a magnitude function.

6. The sensor assembly according to claim 5, wherein the processor is implemented to calculate the magnitude function by means of a CORDIC algorithm.

7. The sensor assembly according to claim 5, wherein the processor is implemented to weight the detected magnetic field component with respect to the first spatial direction or the detected magnetic field component with respect to the second spatial direction with a first weighting factor of less than or equal to 0.75.

8. The sensor assembly according to claim 1, wherein the first magnetic field sensor and the second magnetic field sensor are each implemented as multi-axis magnetic field sensor, wherein each sensor element of the multi-axis magnetic field sensor comprises a magnetic sensitivity with respect to the first spatial direction and the second spatial direction.

9. The sensor assembly according to claim 1, wherein the processor is further implemented

to determine whether the indicator magnet is within a central region around a reference point of the sensor assembly, based on a comparison of a magnetic field component detected by the first magnetic field sensor or the second magnetic field sensor with respect to the first spatial direction with a magnetic field component detected by the first magnetic field sensor or the second magnetic field sensor with respect to the second spatial direction;

and

if the indicator magnet is within the central region, to determine the magnetization direction based on a sign of a detected magnetic field component with respect to the first spatial direction.

10. The sensor assembly according to claim 9, wherein the processor is implemented to state the first magnetization direction at a positive sign of the detected magnetic field component with respect to the first spatial direction, and to state the second magnetization direction at a negative sign of the detected magnetic field component with respect to the first spatial direction, when a magnitude of the detected magnetic field component with respect to the first spatial direction is greater than a magnitude of the detected magnetic field component with respect to the second spatial direction.

11. The sensor assembly according to claim 10, wherein the processor is implemented to determine the magnitude and the magnitude each via a magnitude function.

12. The sensor assembly according to claim 10, wherein the processor is implemented to weight the magnitude or the magnitude with a second weighting factor, such that the central region around the reference point is reduced.

13. The sensor assembly according to claim 12, wherein the processor is implemented to weight the magnitude with the second weighting factor between 0.25 and 1.

14. A non-transitory computer readable medium including a computer program for performing, when the computer program runs on a processor, the method for determining a magnetization direction of an indicator magnet with respect to a sensor assembly, wherein the sensor assembly comprises a first magnetic field sensor configured to detect a first magnetic field component of the indicator magnet with respect to a first spatial direction and a second magnetic field component of the indicator magnet with respect to a second spatial direction, wherein the first and second spatial directions are linearly independent spatial directions, and a second magnetic field sensor spaced apart therefrom configured to detect a third magnetic field component of the indicator magnet with respect to the first spatial direction and a fourth magnetic field component of the indicator magnet with respect to the second spatial direction, the method comprising:

combining a first value derived from the first magnetic field component and a second value derived from the second magnetic field component to acquire a first combination result;

combining a third value derived from the third magnetic field component and a fourth value derived from the fourth magnetic field component to acquire a second combination result;

determining a position of the indicator magnet with respect to the sensor assembly based on a comparison of the first combination result and the second combination result; and

determining the magnetization direction based on the determined position of the indicator magnet with respect to the sensor assembly and on a sign of a detected magnetic field component with respect to the second spatial direction.

15. A method for determining a magnetization direction of an indicator magnet with respect to a sensor assembly, wherein the sensor assembly comprises a first magnetic field sensor configured to detect a first magnetic field component of the indicator magnet with respect to a first spatial direction and a second magnetic field component of the indicator magnet with respect to a second spatial direction, wherein the first and second spatial directions are linearly independent spatial directions, and a second magnetic field sensor spaced apart therefrom configured to detect a third magnetic field component of the indicator magnet with respect to the first spatial direction and a fourth magnetic field component of the indicator magnet with respect to the second spatial direction, comprising:

combining a first value derived from the first magnetic field component and a second value derived from the second magnetic field component to acquire a first combination result;

combining a third value derived from the third magnetic field component and a fourth value derived from the fourth magnetic field component to acquire a second combination result;

determining a position of the indicator magnet with respect to the sensor assembly based on a comparison of the first combination result and the second combination result; and

determining the magnetization direction based on the determined position of the indicator magnet with respect to the sensor assembly and on a sign of a detected magnetic field component with respect to the second spatial direction.

16. The method according to claim 15, wherein the first magnetic field component and the third magnetic field component are detected in an axial direction and the second magnetic field component and the fourth magnetic field component in a radial direction with respect to a relative direction of movement of the indicator magnet with respect to the sensor assembly.

17. The method according to claim 15, wherein in the step of determining the position a first position of the indicator magnet with respect to the sensor assembly is determined, when a magnitude of the first combination quantity is greater than a magnitude of the second combination quantity, and a second position of the indicator magnet with respect to the sensor assembly is determined when the magnitude of the second combination quantity is greater than the magnitude of the first combination quantity.

18. The method according to claim 15, wherein in the step of determining the magnetization direction, when the first position has been determined, a first magnetization direction is stated at a positive sign of the second magnetic field component or the fourth magnetic field component, and when the second position has been determined, a second magnetization direction is stated, and when the first position has been determined, the second magnetization direction is stated at a negative sign of the second magnetic field component or the fourth magnetic field component, and when the second position has been determined, the first magnetization direction is stated.

19. The method according to claim 15, wherein the first magnetic field component is combined with the second magnetic field component and the third magnetic field component with the fourth magnetic field component, such that the magnitude of the first combination quantity represents a magnitude function and the magnitude of the second combination quantity represents a magnitude function.

20. The method according to claim 15, further comprising:

determining whether the indicator magnet is within a central region around a reference point of the sensor assembly, based on a comparison of a magnetic field component detected by the first magnetic field sensor or second magnetic field sensor with respect to the first spatial direction with a magnetic field component detected by the first magnetic field sensor or second magnetic field sensor with respect to the second spatial direction;

if the indicator magnet is within the central region, determining the magnetization direction based on a sign of a detected magnetic field component with respect to the first spatial direction; and

if the indicator magnet is outside the central region, determining the magnetization direction according to the method for determining a magnetization direction of an indicator magnet with respect to a sensor assembly, wherein the sensor assembly comprises a first magnetic field sensor for detecting a first magnetic field component with respect to a first spatial direction and a second magnetic field component with respect to a second spatial direction, and a second magnetic field sensor spaced apart therefrom for detecting a third magnetic field component with respect to the first spatial direction and a fourth magnetic field component with respect to the second spatial direction, the method comprising;

combining the first magnetic field component and the second magnetic field component to acquire a first combination quantity;

combining the third magnetic field component and the fourth magnetic field component to acquire a second combination quantity;

determining a position of the indicator magnet with respect to the sensor assembly based on a comparison of the first combination quantity and a second combination quantity; and

determining the magnetization direction based on the determined position of the indicator magnet with respect to the sensor assembly and on a sign of a detected magnetic field component with respect to the second spatial direction.