Linear position sensor system
View Patent ↗A position sensor measures a magnetic flux of a magnetic field produced by a magnet system in a first direction and a second direction. Values associated with the measured magnetic flux in the first direction are adjusted based on a first gain and a first offset that are determined based on the measured magnetic flux and a reference magnetic flux in the first direction. Values associated with the measured magnetic flux in the second direction are adjusted based on a second gain and a second offset that are determined based on the measured magnetic flux and a reference magnetic flux in the second direction. A position of the magnet system with respect to the position sensor at a given time may then be determined based on the adjusted values of the magnetic flux in the first and second directions at the given time.
1. A computer-implemented method for detecting a position of a magnet system, the method comprising:
measuring, at a position sensor, a magnetic flux of a magnetic field in a first direction that is produced by a magnet system and measuring, at the position sensor, a magnetic flux of a magnetic field in a second direction that is produced by the magnet system, where the first direction and the second direction are different directions;
determining, with a controller, a first offset based on a first measured maximum flux value, a second measured maximum flux value, and a measured minimum flux value associated with the measured magnetic flux in the first direction and a first reference maximum flux value, a second reference maximum flux value and a reference minimum flux value associated with the magnetic flux in the first direction;
determining, with the controller, a first gain based on the first offset, one of the first measured maximum flux value and the second measured maximum flux value, and one of the first reference maximum flux value and the second reference maximum flux value associated with the magnetic flux in the first direction, or based on the first offset, the measured minimum flux value, and the reference minimum flux value associated with the magnetic flux in the first direction;
adjusting, with the controller, at least a portion of the values of the measured magnetic flux in the first direction based on the first gain and the first offset, where the adjustment occurs at at least one of a zero crossing associated with the magnetic flux in the first direction and a zero crossing associated with the magnetic flux in the second direction;
determining, with the controller, a second offset based on a measured maximum flux value and a measured minimum flux value associated with the measured magnetic flux in the second direction and a reference maximum flux value and a reference minimum flux value associated with the magnetic flux in the second direction;
determining, with the controller, a second gain based on the second offset, the measured maximum flux value, and the reference maximum flux value associated with the magnetic flux in the second direction, or based on the second offset, the measured minimum flux value, and the reference minimum flux value associated with the magnetic flux in the second direction;
adjusting, with the controller, at least a portion of the values of the measured magnetic flux in the second direction based on the second gain and the second offset, where the adjustment occurs at at least one of a zero crossing associated with the magnetic flux in the first direction and a zero crossing associated with the magnetic flux in the second direction; and
determining, with the controller, a position of the magnet system with respect to the position sensor at a given time based on the adjusted values of the measured magnetic flux in the first direction and the adjusted values of the measured magnetic flux in the second direction.
2. The computer-implemented method of claim 1 , wherein determining the position of the magnet system with respect to the position sensor at a given time comprises:
obtaining a value from a lookup table that is associated with a relationship between the adjusted value of the measured magnetic flux in the first direction at the given time and the adjusted value of the measured magnetic flux in the second direction at the given time; and
linearizing the value from the lookup table.
3. The computer-implemented method of claim 2 , wherein obtaining a value from a lookup table comprises:
determining a relationship between the adjusted value of the measured magnetic flux in the first direction at the given time and the adjusted value of the measured magnetic flux in the second direction at the given time using an arctangent function; and
obtaining a value from a lookup table associated with the determined relationship.
4. The computer-implemented method of claim 2 , wherein obtaining a value from a lookup table comprises:
determining an angle based on the adjusted value of the measured magnetic flux in the first direction at the given time and the adjusted value of the measured magnetic flux in the second direction at the given time using a coordinate rotation digital computer (“CORDIC”) function; and
obtaining a value from a lookup table associated with the determined angle.
5. The computer-implemented method of claim 1 , wherein determining the position of the magnet system with respect to the position sensor at a given time comprises:
determining a relationship between the adjusted value of the measured magnetic flux in the first direction at the given time and the adjusted value of the measured magnetic flux in the second direction at the given time using an arctangent function;
determining a value associated with the relationship using a polynomial position function; and
linearizing the value.
6. The computer-implemented method of claim 1 , wherein determining the position of the magnet system with respect to the position sensor at a given time comprises:
determining an angle based on the adjusted value of the measured magnetic flux in the first direction at the given time and the adjusted value of the measured flux in the second direction at the given time using a coordinate rotation digital computer (“CORDIC”) function;
determining a value associated with the angle using a polynomial position function; and
linearizing the value.
7. The computer-implemented method of claim 1 , wherein the magnet system comprises one magnet.
8. The computer-implemented method of claim 1 , wherein the magnet system comprises more than one magnet.
9. The computer-implemented method of claim 1 , further comprising:
determining whether the position sensor is malfunctioning based on at least one of a plausibility check associated with the first measured maximum magnetic flux, the second measured maximum magnetic flux, the measured minimum magnetic flux, the first reference maximum magnetic flux, the second reference maximum flux and the reference minimum magnetic flux in the first direction, and a plausibility check associated with the measured maximum magnetic flux, the measured minimum magnetic flux, the reference maximum magnetic flux, and the reference minimum magnetic flux in the second direction.
10. The computer-implemented method of claim 1 , further comprising:
filtering values from at least one of the measured magnetic flux in the first direction prior to determining the first offset and the first gain, and the measured magnetic flux in the second direction prior to determining the second offset and the second gain.
11. The computer-implemented method of claim 1 , wherein determining the first offset comprises:
calculating the first offset using the equation:
FirstOffset
=
Φ
m
i
n
M
·
Φ
ma
x
R
Φ
m
i
n
R
-
Φ
m
ax
R
1
-
Φ
m
ax
R
Φ
m
i
n
R
,
wherein Φ max R is a mean of the first reference maximum flux value and the second reference maximum flux value, Φ min R is the reference minimum flux value, Φ max M is a mean of the first measured maximum flux value and the second measured maximum flux value, and Φ min M is the measured minimum flux value associated with the magnetic flux in the first direction; and
wherein the first gain is determined based on the first offset, one of the first measured maximum flux value and the second measured maximum flux value, and one of the first reference maximum flux value and the second reference maximum flux value associated with the magnetic flux in the first direction using the equation:
FirstGain
=
Φ
m
ax
R
FirstOffset
+
Φ
ma
x
M
,
wherein Φ max R is one of the first reference maximum flux value and the second reference maximum flux value and Φ max M is one of the first measured maximum flux value and the second measured maximum flux value.
12. The computer-implemented method of claim 11 , wherein determining the first offset comprises:
calculating the first offset using the equation:
SecondOffset
=
Φ
m
i
n
M
·
Φ
ma
x
R
Φ
m
i
n
R
-
Φ
ma
x
R
1
-
Φ
m
ax
R
Φ
m
i
n
R
,
wherein Φ max R is a mean of the first reference maximum flux value and the second reference maximum flux value, Φ min R is the reference minimum flux value, Φ max M is a mean of the first measured maximum flux value and the second measured maximum flux value, and Φ min M is the measured minimum flux value associated with the magnetic flux in the first direction; and
wherein the first gain is determined based on the first offset, the measured minimum flux value, and the reference minimum flux value associated with the magnetic flux in the first direction using the equation:
FirstGain
=
Φ
m
i
n
R
FirstOffset
+
Φ
m
i
n
M
,
wherein Φ min R is the reference minimum flux value and Φ min M is the measured minimum flux value.
13. The computer-implemented method of claim 1 , wherein determining the second offset comprises:
calculating the second offset using the equation:
SecondOffset
=
Φ
m
i
n
M
·
Φ
ma
x
R
Φ
m
i
n
R
-
Φ
ma
x
R
1
-
Φ
ma
x
R
Φ
m
i
n
R
,
wherein Φ max R is the reference maximum flux value, Φ min R is the reference minimum flux value, Φ max M is the measured maximum flux value, and Φ min M is the measured minimum flux value associated with the magnetic flux in the second direction; and
wherein the second gain is determined based on the second offset, the measured maximum flux value, and the reference maximum flux value associated with the magnetic flux in the second direction using the equation:
SecondGain
=
Φ
m
ax
R
SecondOffset
+
Φ
ma
x
M
,
wherein Φ max R is the reference maximum flux value and Φ max M is the measured maximum flux value.
14. The computer-implemented method of claim 1 , wherein determining the second offset comprises:
calculating the second offset using the equation:
SecondOffset
=
Φ
m
i
n
M
·
Φ
ma
x
R
Φ
m
i
n
R
-
Φ
ma
x
R
1
-
Φ
ma
x
R
Φ
m
i
n
R
,
wherein Φ max R is the reference maximum flux value, Φ min R is the reference minimum flux value, Φ max M is the measured maximum flux value, and Φ min M is the measured minimum flux value associated with the magnetic flux in the second direction; and
wherein the second gain is determined based on the second offset, the measured minimum flux value, and the reference minimum flux value associated with the magnetic flux in the second direction using the equation:
SecondGain
=
Φ
m
i
n
R
SecondOffset
+
Φ
m
i
n
M
,
wherein Φ min R is the reference minimum flux value and Φ min M the measured minimum flux value.
15. A non-transitory computer-readable storage medium comprising a set of instructions for detecting a position of a magnet system, the set of instructions to direct a processor perform acts of:
instructing a position sensor to measure a magnetic flux of a magnetic field in a first direction that is produced by a magnet system and instructing the position sensor to measure a magnetic flux of a magnetic field in a second direction that is produced by the magnet system, where the first direction and the second direction are different directions;
determining a first offset based on a first measured maximum flux value, a second measured maximum flux value, and a measured minimum flux value associated with the measured magnetic flux in the first direction and a first reference maximum flux value, a second reference maximum flux value, and a reference minimum flux value associated with the magnetic flux in the first direction;
determining a first gain based on the first offset, one of the first measured maximum flux value and the second maximum flux value, and one of the first reference maximum flux value and the second reference maximum flux value associated with the magnetic flux in the first direction, or based on the first offset, the measured minimum flux value, and the reference minimum flux value associated with the magnetic flux in the first direction;
adjusting at least a portion of the values of the measured magnetic flux in the first direction based on the first gain and the first offset, where the adjustment occurs at at least one of a zero crossing associated with the magnetic flux in the first direction and a zero crossing associated with the magnetic flux in the second direction;
determining a second offset based on a measured maximum flux value and a measured minimum flux value associated with the measured magnetic flux in the second direction and a reference maximum flux value and a reference minimum flux value associated with the magnetic flux in the second direction;
determining a second gain based on the second offset, the measured maximum flux value, and the reference maximum flux value associated with the magnetic flux in the second direction, or based on the second offset, the measured minimum flux value, and the reference minimum flux value associated with the magnetic flux in the second direction;
adjusting at least a portion of the values of the measured magnetic flux in the second direction based on the second gain and the second offset, where the adjustment occurs at at least one of a zero crossing associated with the magnetic flux in the first direction and a zero crossing associated with the magnetic flux in the second direction; and
determining a position of the magnet system with respect to the position sensor at a given time based on the adjusted values of the measured magnetic flux in the first direction and the adjusted values of the measured magnetic flux in the second direction.
16. The computer-readable storage medium of claim 15 , wherein determining the position of the magnet system with respect to the position sensor at a given time comprises:
obtaining a value from a lookup table that is associated with a relationship between the adjusted value of the measured magnetic flux in the first direction at the given time and the adjusted value of the measured magnetic flux in the second direction at the given time; and
linearizing the value from the lookup table.
17. A linear position sensor system for detecting a position of a magnet system with respect to a position sensor, the system comprising:
a position sensor configured to measure a magnetic flux of a magnetic field produced by a magnet system; and
a controller in communication with the position sensor, the controller comprising a computer-readable storage medium and a processor, the controller configured to:
direct the position sensor to measure a magnetic flux of a magnetic field in a first direction that is produced by a magnet system and to direct the position sensor to measure a magnetic flux of a magnetic field in a second direction that is produced by the magnet system, where the first direction and the second direction are different directions;
determine a first offset based on measured maximum and minimum flux values of the measured magnetic flux in the first direction and reference maximum and minimum flux values of the magnetic flux in the first direction;
determine a first gain based on the first offset, a measured maximum flux value of the measured maximum flux values, and a reference maximum flux value of the reference maximum flux values in the first direction, or based on the first offset, the measured minimum flux value, and the reference minimum flux value in the first direction;
adjust at least a portion of the values of the measured magnetic flux in the first direction based on the first gain and the first offset, where the adjustment occurs at at least one of a zero crossing associated with the magnetic flux in the first direction and a zero crossing associated with the magnetic flux in the second direction;
determine a second offset based on measured maximum and minimum flux values of the measured magnetic flux in the second direction and reference maximum and minimum flux values of the magnetic flux in the second direction;
determine a second gain based on the second offset, the measured maximum flux value, and the reference maximum flux value in the second direction, or based on the second offset, the measured minimum flux value, and the reference minimum flux value in the second direction;
adjust at least a portion of the values of the measured magnetic flux in the second direction based on the second gain and the second offset, where the adjustment occurs at at least one of a zero crossing associated with the magnetic flux in the first direction and a zero crossing associated with the magnetic flux in the second direction; and
determine a position of the magnet system with respect to the position sensor at a given time based on the adjusted values of the measured magnetic flux in the first direction and the adjusted values of the measured magnetic flux in the second direction.
18. The system of claim 17 , wherein to determine the position of the magnet system with respect to the position sensor at a given time, the controller is configured to:
obtain a value from a lookup table that is associated with a relationship between the adjusted value of the measured magnetic flux in the first direction at the given time and the adjusted value of the measured magnetic flux in the second direction at the given time; and
linearize the value from the lookup table.
19. The system of claim 17 , wherein the controller is further configured to determine whether the position sensor is malfunctioning based on at least one of a plausibility check associated with the measured maximum and minimum magnetic flux values and the corresponding reference maximum and minimum magnetic flux values in the first direction, and a plausibility check associated with the measured maximum and minimum magnetic flux values and the corresponding reference maximum and minimum magnetic flux values in the second direction.
20. A computer-implemented method for detecting a position of a magnet system, the method comprising:
measuring, at a position sensor, a magnetic flux of a magnetic field in a first direction that is produced by a magnet system and measuring, at the position sensor, a magnetic flux of a magnetic field in a second direction that is produced by the magnet system, wherein the first and second directions are different directions;
adjusting, with a controller, at least a portion of the values of the measured magnetic flux in the first direction based on a first gain and a first offset, the first gain and the first offset determined based on measured maximum and minimum flux values of the measured magnetic flux in the first direction and reference maximum and minimum flux values of the magnetic flux in the first direction, where the adjustment occurs at at least one of a zero crossing associated with the magnetic flux in the first direction and a zero crossing associated width the magnetic flux in the second direction;
adjusting, with the controller, a at least a portion of the values of the measured magnetic flux in the second direction based on a second gain and a second offset, the second gain and the second offset determined based on measured maximum and minimum flux values of the measured magnetic flux in the second direction and reference maximum and minimum flux values of the magnetic flux in the second direction, where the adjustment occurs at at least one of a zero crossing associated with the magnetic flux in the first direction and a zero crossing associated with the magnetic flux in the second direction; and
determining, with the controller, a position of the magnet system with respect to the position sensor at a given time based on the adjusted values of the measured magnetic flux in the first direction and the adjusted values of the measured magnetic flux in the second direction.
21. The computer-implemented method of claim 20 , wherein the controller comprises an application-specific integrated circuit.
22. The computer-implemented method of claim 20 , wherein the controller comprises a processor.