Position sensor devices, methods and systems based on magnetic field gradients

Patent metadata

Field	Value
Publication number	US-11892325-B2
Application number	US-202117207301-A
Country	US
Kind code	B2
Filing date	Mar 19, 2021
Priority date	Mar 23, 2020
Publication date	Feb 6, 2024
Grant date	Feb 6, 2024

Abstract

A method of determining a linear or angular position of a magnetic sensor device relative to a magnetic source, or vice versa, the sensor device includes at least four magnetic sensor elements. The method involves the steps of: a) determining a first magnetic field gradient; b) determining a second magnetic field gradient; c) determining a ratio of the first and second magnetic field gradient; d) converting the ratio into a position; while matching signal paths of the magnetic sensor elements so as to improve signal-to-noise.

First claim

The invention claimed is:

1. A method of determining a linear or angular position of a magnetic sensor device relative to a magnetic source, or vice versa; the magnetic sensor device comprising:
a first, a second, a third and a fourth magnetic sensor element;
a first, second, third and fourth biasing source for biasing said sensor elements;
a first, second, third and fourth amplifier for amplifying a signal originating from said sensor elements;
at least one analog-to-digital converter for digitizing signals originating from said amplifiers;
one or both of a temperature sensor and a differential stress measurements circuit;
a digital processing circuit connected downstream of the analog-to-digital convertor;
the method comprising the steps of:
obtaining one or both of a temperature value and a differential stress value;
a) determining a first magnetic field gradient based on signals obtained from the first and the third magnetic sensor element;
b) determining a second magnetic field gradient based on signals obtained from the second and the fourth magnetic sensor element;
c) calculating a ratio of the first and the second magnetic field gradient;
d) determining said linear or angular position based on said ratio;

wherein:
step a) comprises: adjusting the third biasing source and/or adjusting a signal path comprising the third amplifier using a first predefined function of temperature and/or differential stress, to match a signal path containing the third sensor element to a signal path containing the first sensor element; and
step b) comprises: adjusting the fourth biasing source and/or adjusting a signal path comprising the fourth amplifier using a second predefined function of temperature and/or differential stress, different from the first predefined function to match a signal path containing the fourth sensor element to a signal path containing the second sensor element;
step d) further comprises: determining said linear or angular position based on said ratio, optionally taking into account a predefined factor K or a predefined function K of temperature.

2. The method according to claim 1 ,
wherein step a) comprises: determining a first magnetic field gradient of a first magnetic field component oriented in a first direction along said first direction; and
wherein step b) comprises: determining a second magnetic field gradient of a second magnetic field component oriented in a second direction substantially perpendicular to the first direction, along said first direction.

3. The method according to claim 1 ,
wherein step a) comprises: determining a first magnetic field gradient of a magnetic field component oriented in a first direction along a second direction substantially perpendicular to the first direction; and
wherein step b) comprises: determining a second magnetic field gradient of said magnetic field component oriented in said first direction along a third direction substantially perpendicular to the first direction and substantially perpendicular to said second direction.

4. The method according to claim 1 , wherein step a) comprises:
determining an analog difference signal between a first signal obtained by: biasing the first magnetic sensor, and amplifying the first sensor signal, and
a second signal obtained by: biasing the second magnetic sensor, and amplifying the second sensor signal,
after measuring a temperature and/or a differential stress, and adjusting the second biasing source or the second amplifier using a predefined function of the measured temperature and/or differential stress; and
digitizing the analog difference signal to obtain the first gradient.

5. The method according to claim 1 , wherein step a) comprises:
determining a digital difference value
between a first digital value obtained by: biasing the first magnetic sensor and amplifying the first sensor signal, and digitizing this amplified signal; and
a second digital value obtained by: biasing the second magnetic sensor, and amplifying the second sensor signal, and digitizing this amplified signal,
after measuring a temperature and/or a differential stress, and adjusting the second biasing source or the second amplifier using a predefined function of the measured temperature and/or differential stress.

6. The method according to claim 1 , wherein step a) comprises:
determining a digital difference value
between a first digital value obtained by: biasing the first magnetic sensor and amplifying the first sensor signal, and digitizing this amplified signal; and
a second digital value obtained by: biasing the second magnetic sensor and amplifying the second sensor signal, and digitizing this amplified signal, and adjusting this digitized value by multiplication with a correction factor using a predefined function of the measured temperature and/or differential stress.

7. The method according to claim 1 , wherein the predefined function for adjusting the biasing source and/or the amplifier gain and/or for correcting the digitized value, is a function of only temperature, or is a function of only differential stress, or is a function of temperature and differential stress.

8. A magnetic position sensor device comprising a semiconductor substrate comprising:
at least a first magnetic sensor located at a first sensor location, and a second magnetic sensor located at a second sensor location, spaced apart from the first sensor location;
at least a first biasing source for biasing the first magnetic sensor, and a second biasing source for biasing the second magnetic sensor;
at least a first amplifier for amplifying a signal obtained from the first magnetic sensor, and a second amplifier for amplifying a signal obtained from the second magnetic sensor;
at least a third magnetic sensor, and optionally a fourth magnetic sensor;
at least a third biasing source for biasing the third magnetic sensor, and optionally a fourth biasing source for biasing the fourth magnetic sensor;
at least a third amplifier for amplifying a signal obtained from the third magnetic sensor, and optionally a fourth amplifier for amplifying a signal obtained from the fourth magnetic sensor;
a temperature sensor located at a predefined position on the substrate;
at least one differential stress sensing circuit configured for determining at least one stress difference between two of said magnetic sensors;
at least one analog-to-digital-converter connected downstream of said amplifiers;
a digital processing circuit connected downstream of the analog-to-digital-converter;
a non-volatile memory operatively connected to the digital processing circuit, configured for storing one or more values or parameters of said predefined function;
wherein the digital processing circuit is configured for performing a method according to claim 1 .

9. A magnetic position sensor system, comprising:
a two-pole ring or disk magnet, rotatable about an axis;
a magnetic position sensor device, arranged at a distance from said magnet, and comprising four horizontal Hall elements arranged on an imaginary circle, and angularly spaced apart by 90°, and four biasing sources, and four amplifiers;
the magnetic sensor further comprising: at least one analog-to-digital convertor, and a temperature sensor and two differential stress sensors; and a digital processing circuit comprising a non-volatile memory, and being configured for performing a method according to claim 1 .

10. A magnetic position sensor system, comprising:
a magnetic structure having at least four poles;
a magnetic position sensor device, arranged at a distance from said magnetic structure, and comprising two magnetic sensors spaced apart from each other,
each magnet

Assignees

• Melexis Tech Sa
• Melexis Tech

Inventors

• Dupre Nicolas
• Bidaux Yves

Classifications

• G01D5/145 Primary

  influenced by the relative movement between the Hall device and magnetic fields (see G01R33/06) · CPC title

• G01B7/30

  for measuring angles or tapers; for testing the alignment of axes · CPC title

• G01K13/00

  Thermometers specially adapted for specific purposes · CPC title

• G01L5/00

  Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes · CPC title

• G01B7/003 Primary

  for measuring position, not involving coordinate determination (coordinate measuring G01B7/004) · CPC title