U.S. patent application number 17/087942 was filed with the patent office on 2022-05-05 for method for on-chip wheel pitch recognition for magnetoresistive sensors.
This patent application is currently assigned to Infineon Technologies AG. The applicant listed for this patent is Infineon Technologies AG. Invention is credited to Alessandro PETRI, Christoph SCHROERS, Massimiliano ZILLI.
Application Number | 20220136865 17/087942 |
Document ID | / |
Family ID | |
Filed Date | 2022-05-05 |
United States Patent
Application |
20220136865 |
Kind Code |
A1 |
SCHROERS; Christoph ; et
al. |
May 5, 2022 |
METHOD FOR ON-CHIP WHEEL PITCH RECOGNITION FOR MAGNETORESISTIVE
SENSORS
Abstract
A sensor device includes a first sensor arrangement configured
to generate first sensor signals based on sensing a varying
magnetic field generated by a pole wheel having a pole wheel pitch,
wherein the first sensor signals represent a first differential
signal that defines a first measurement value; a second sensor
arrangement configured to generate at least one second sensor
signal based on sensing the varying magnetic field, wherein the at
least one second sensor signal defines a second measurement value
that is phase shifted from the first measurement value; and a
signal processor configured to detect the pole wheel pitch based on
the first measurement value and the second measurement value, and
adjust a gain setting of an amplifier circuit based on the detected
pole wheel pitch, where the amplifier circuit is configured to
amplify the at least one second sensor signal.
Inventors: |
SCHROERS; Christoph;
(Villach, AT) ; PETRI; Alessandro; (Villach,
AT) ; ZILLI; Massimiliano; (Villach, AT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Infineon Technologies AG |
Neubiberg |
|
DE |
|
|
Assignee: |
Infineon Technologies AG
Neubiberg
DE
|
Appl. No.: |
17/087942 |
Filed: |
November 3, 2020 |
International
Class: |
G01D 5/16 20060101
G01D005/16; G01D 5/244 20060101 G01D005/244 |
Claims
1. A sensor device, comprising: a first sensor arrangement
comprising a plurality of first sensor elements configured to
generate first sensor signals based on sensing a varying magnetic
field generated by a pole wheel having a pole wheel pitch, wherein
the first sensor signals represent a first differential signal that
defines a first measurement value; a second sensor arrangement
comprising at least one second sensor element configured to
generate at least one second sensor signal based on sensing the
varying magnetic field generated by the pole wheel, wherein the at
least one second sensor signal defines a second measurement value
that is phase shifted from the first measurement value; a first
amplifier circuit configured to receive and amplify the first
sensor signals to generate amplified first sensor signals; a second
amplifier circuit configured to receive and amplify the at least
one second sensor signal to generate at least one amplified second
sensor signal; and a sensor circuit configured to convert the
amplified first sensor signals into the first differential signal
having the first measurement value and convert the at least one
amplified second sensor signal into a measurement signal having the
second measurement value, wherein the sensor circuit comprises a
signal processor configured to detect the pole wheel pitch based on
the first measurement value and the second measurement value, and
adjust a gain setting of the second amplifier circuit based on the
detected pole wheel pitch.
2. The sensor device of claim 1, wherein the measurement signal is
shifted 90.degree. from the first differential signal.
3. The sensor device of claim 1, wherein the second sensor
arrangement comprises a plurality of second sensor elements
configured to generate second sensor signals based on sensing the
varying magnetic field generated by the pole wheel, wherein the
second sensor signals represent a second differential signal that
defines the second measurement value.
4. The sensor device of claim 3, wherein: the second amplifier
circuit is configured to receive and amplify the second sensor
signals to generate amplified second sensor signals; the sensor
circuit configured to convert the amplified second sensor signals
into the measurement signal, the measurement signal being the
second differential signal having the second measurement value, the
signal processor is configured to detect the pole wheel pitch based
on the first measurement value and the second measurement value,
and adjust the gain setting of the second amplifier circuit based
on the detected pole wheel pitch.
5. The sensor device of claim 4, wherein the first measurement
value is a first differential value and the second measurement
value is a second differential value.
6. The sensor device of claim 3, wherein the plurality of first
sensor elements are arranged in a first bridge circuit and the
plurality of second sensor elements are arranged in a second bridge
circuit.
7. The sensor device of claim 1, wherein: the signal processor is
configured to correlate a combination of the first measurement
value and the second measurement value to a corresponding gain
setting of a plurality of gain settings, select the corresponding
gain setting from among the plurality of gain settings based on the
combination of the first measurement value and the second
measurement value, and set the selected corresponding gain setting
as the gain setting of the second amplifier circuit.
8. The sensor device of claim 7, wherein each of the plurality of
gain settings corresponds to one of a plurality of pole wheel
pitches programmed in memory of the sensor circuit.
9. The sensor device of claim 7, wherein: the signal processor is
configured to detect the pole wheel pitch using a look-up table,
wherein the signal processor determines the pole wheel pitch based
on the combination of the first measurement value and the second
measurement value within the look-up table, and selects the
corresponding gain setting based on the determined the pole wheel
pitch.
10. The sensor device of claim 7, wherein: the signal processor is
configured to select the corresponding gain setting using a look-up
table, wherein the signal processor selects the corresponding gain
setting based on the combination of the first measurement value and
the second measurement value within the look-up table.
11. The sensor device of claim 7, wherein: the signal processor is
configured to select the corresponding gain setting based on a
logic circuit formalized by if then else statements, wherein the
signal processor selects the corresponding gain setting based on
the combination of the first measurement value and the second
measurement value satisfying one of the if then else
statements.
12. The sensor device of claim 7, wherein: the signal processor is
configured to calculate a ratio of the first measurement value and
the second measurement value, compare the ratio to at least one
threshold to generate a comparison result, and select the
corresponding gain setting based the comparison result.
13. The sensor device of claim 7, wherein: the signal processor is
configured select the corresponding gain setting based on a ratio
of the first measurement value and the second measurement
value.
14. The sensor device of claim 7, wherein: the signal processor is
configured to calculate a ratio of the first measurement value and
the second measurement value, determine a threshold range from a
plurality of threshold ranges in which the ratio is located, and
select the corresponding gain setting based on the determined
threshold range.
15. The sensor device of claim 7, wherein the signal processor is
configured to calculate a ratio of the first measurement value and
the second measurement value, and select the corresponding gain
setting based the ratio.
16. A sensor device, comprising: a first sensor arrangement
comprising a plurality of first sensor elements configured to
generate first sensor signals based on sensing a varying magnetic
field generated by a pole wheel having a pole wheel pitch, wherein
the first sensor signals represent a first differential signal that
defines a first measurement value; a second sensor arrangement
comprising at least one second sensor element configured to
generate at least one second sensor signal based on sensing the
varying magnetic field generated by the pole wheel, wherein the at
least one second sensor signal defines a second measurement value
that is phase shifted from the first measurement value; a first
amplifier circuit configured to receive and amplify the first
sensor signals to generate amplified first sensor signals; a second
amplifier circuit configured to receive and amplify the at least
one second sensor signal to generate at least one amplified second
sensor signal; and a sensor circuit configured to convert the
amplified first sensor signals into the first differential signal
having the first measurement value and convert the at least one
amplified second sensor signal into a measurement signal having the
second measurement value, wherein the sensor circuit comprises a
signal processor configured to correlate a combination of the first
measurement value and the second measurement value to a
corresponding gain setting of a plurality of gain settings, select
the corresponding gain setting from among the plurality of gain
settings based on the combination of the first measurement value
and the second measurement value, and set the selected
corresponding gain setting as the gain setting of the second
amplifier circuit.
17. The sensor device of claim 16, wherein the corresponding gain
setting is optimized for the pole wheel pitch.
18. A method for calibrating a magnetic field sensor circuit based
on a pole wheel pitch of a pole wheel, the method comprising:
generating first sensor signals, by a first sensor arrangement,
based on sensing a varying magnetic field generated by the pole
wheel, wherein the first sensor signals represent a first
differential signal that defines a first measurement value;
generating at least one second sensor signal, by a second sensor
arrangement, based on sensing the varying magnetic field generated
by the pole wheel, wherein the at least one second sensor signal
defines a second measurement value that is phase shifted from the
first measurement value; amplifying the first sensor signals, by a
first amplifier circuit, to generate amplified first sensor
signals; amplifying the at least one second sensor signal, by a
second amplifier circuit, to generate at least one amplified second
sensor signal; converting the amplified first sensor signals, by a
sensor circuit, into the first differential signal having the first
measurement value; converting the at least one amplified second
sensor signal, by the sensor circuit, into a measurement signal
having the second measurement value; correlating, by the sensor
circuit, a combination of the first measurement value and the
second measurement value to a corresponding gain setting of a
plurality of gain settings; selecting, by the sensor circuit, the
corresponding gain setting from among the plurality of gain
settings based on the combination of the first measurement value
and the second measurement value; and setting, by the sensor
circuit, the selected corresponding gain setting as the gain
setting of the second amplifier.
19. The method of claim 18, wherein each of the plurality of gain
settings corresponds to one of a plurality of pole wheel pitches
programmed in memory of the sensor circuit.
20. The method of claim 18, further comprising: detecting, by the
sensor circuit, the pole wheel pitch using a look-up table,
including determining the pole wheel pitch based on the combination
of the first measurement value and the second measurement value
within the look-up table, and selecting the corresponding gain
setting based on the determined the pole wheel pitch.
21. The method of claim 18, further comprising: selecting, by the
sensor circuit, the corresponding gain setting using a look-up
table, including selecting the corresponding gain setting based on
the combination of the first measurement value and the second
measurement value within the look-up table.
22. The method of claim 18, further comprising: selecting, by the
sensor circuit, the corresponding gain setting based on a logic
circuit formalized by if then else statements, including selecting
the corresponding gain setting based on the combination of the
first measurement value and the second measurement value satisfying
one of the if then else statements.
23. The method of claim 18, further comprising: calculating, by the
sensor circuit, a ratio of the first measurement value and the
second measurement value; comparing, by the sensor circuit, the
ratio to at least one threshold to generate a comparison result;
and selecting, by the sensor circuit, the corresponding gain
setting based the comparison result.
24. The method of claim 19, further comprising: selecting, by the
sensor circuit, the corresponding gain setting based on a ratio of
the first measurement value and the second measurement value.
25. The method of claim 18, further comprising: calculating, by the
sensor circuit, a ratio of the first measurement value and the
second measurement value; determining, by the sensor circuit, a
threshold range from a plurality of threshold ranges in which the
ratio is located; and selecting, by the sensor circuit, the
corresponding gain setting based on the determined threshold
range.
26. The method of claim 18, further comprising: calculating, by the
sensor circuit, a ratio of the first measurement value and the
second measurement value; and selecting, by the sensor circuit, the
corresponding gain setting based the ratio.
Description
BACKGROUND
[0001] Magnetic speed sensors are used in speed sensing for many
applications in many industries including in the automotive
industry for wheel speed, engine speed, and transmission speed, and
the like. In the field of speed sensing, a sinusoidal signal may be
generated by a magnetic sensor in response to a rotation of a
target object, such as a wheel, camshaft, crankshaft, or the like.
The sinusoidal signal may be translated into pulses, which is
further translated into a movement detection or a speed output.
[0002] Information from a speed sensor may generate a speed signal
from which the speed of the target object can be extracted as well
as a direction signal that in combination with the speed signal
gives the rotational direction of the movement of the target
object. Thus, a speed sensor may generate a speed signal and a
direction signal. Based on one or both of these signals additional
output signals (e.g., pulsed output signals) are generated that
provide sensor information to a microcontroller that uses the
pulsed output signal.
[0003] A sensor element pitch is the lateral, center-to-center,
distance between two magnetic field sensor elements that are
arranged along a rotation direction of the target object.
[0004] A pitch of a pole wheel is the center-to-center distance
along a pitch circle between two neighboring poles of the same
polarity (i.e., between two neighboring positive poles or two
neighboring negative poles). Two neighboring poles of the same
polarity have one pole of opposite polarity interposed
therebetween. Thus, a half-pitch of a pole wheel is the
center-to-center distance along a pitch circle between two adjacent
poles of different (i.e., opposite) polarity. In other words, the
half-pitch is the distance along a pitch circle between a center of
positive pole and a center of a negative pole that is adjacent to
the positive pole.
[0005] For a good system performance, the sensor element pitch of a
sensor integrated circuit (IC) and the wheel half-pitch should
match each other (1:1). In other words, the sensor element pitch
should be half of the wheel pitch (1:2). This ratio provides
improved signal-to-noise ratio. Unfortunately, this is not always
possible because one sensor IC can be designed for different
platforms that use different wheels with different wheel pitches.
If the sensor element pitch and the wheel half-pitch are not
matched, performance can be lost.
[0006] Therefore, an improved magnetic field sensor capable of
determining the wheel pitch and performing compensation based
thereon may be desirable.
SUMMARY
[0007] Embodiments provide a sensor device that includes: a first
sensor arrangement including a plurality of first sensor elements
configured to generate first sensor signals based on sensing a
varying magnetic field generated by a pole wheel having a pole
wheel pitch, wherein the first sensor signals represent a first
differential signal that defines a first measurement value; a
second sensor arrangement including at least one second sensor
element configured to generate at least one second sensor signal
based on sensing the varying magnetic field generated by the pole
wheel, wherein the at least one second sensor signal defines a
second measurement value that is phase shifted from the first
measurement value; a first amplifier circuit configured to receive
and amplify the first sensor signals to generate amplified first
sensor signals; a second amplifier circuit configured to receive
and amplify the at least one second sensor signal to generate at
least one amplified second sensor signal; and a sensor circuit
configured to convert the amplified first sensor signals into the
first differential signal having the first measurement value and
convert the at least one amplified second sensor signal into a
measurement signal having the second measurement value. The sensor
circuit includes a signal processor configured to detect the pole
wheel pitch based on the first measurement value and the second
measurement value, and adjust a gain setting of the second
amplifier circuit based on the detected pole wheel pitch.
[0008] Embodiments further provide a sensor device that includes: a
first sensor arrangement including a plurality of first sensor
elements configured to generate first sensor signals based on
sensing a varying magnetic field generated by a pole wheel having a
pole wheel pitch, wherein the first sensor signals represent a
first differential signal that defines a first measurement value; a
second sensor arrangement including at least one second sensor
element configured to generate at least one second sensor signal
based on sensing the varying magnetic field generated by the pole
wheel, wherein the at least one second sensor signal defines a
second measurement value that is phase shifted from the first
measurement value; a first amplifier circuit configured to receive
and amplify the first sensor signals to generate amplified first
sensor signals; a second amplifier circuit configured to receive
and amplify the at least one second sensor signal to generate at
least one amplified second sensor signal; and a sensor circuit
configured to convert the amplified first sensor signals into the
first differential signal having the first measurement value and
convert the at least one amplified second sensor signal into a
measurement signal having the second measurement value. The sensor
circuit includes a signal processor configured to correlate a
combination of the first measurement value and the second
measurement value to a corresponding gain setting of a plurality of
gain settings, select the corresponding gain setting from among the
plurality of gain settings based on the combination of the first
measurement value and the second measurement value, and set the
selected corresponding gain setting as the gain setting of the
second amplifier circuit.
[0009] Embodiments further provide a method for calibrating a
magnetic field sensor circuit based on a pole wheel pitch of a pole
wheel., The method includes: generating first sensor signals, by a
first sensor arrangement, based on sensing a varying magnetic field
generated by the pole wheel, wherein the first sensor signals
represent a first differential signal that defines a first
measurement value; generating at least one second sensor signal, by
a second sensor arrangement, based on sensing the varying magnetic
field generated by the pole wheel, wherein the at least one second
sensor signal defines a second measurement value that is phase
shifted from the first measurement value; amplifying the first
sensor signals, by a first amplifier circuit, to generate amplified
first sensor signals; amplifying the at least one second sensor
signal, by a second amplifier circuit, to generate at least one
amplified second sensor signal; converting the amplified first
sensor signals, by a sensor circuit, into the first differential
signal having the first measurement value; converting the at least
one amplified second sensor signal, by the sensor circuit, into a
measurement signal having the second measurement value;
correlating, by the sensor circuit, a combination of the first
measurement value and the second measurement value to a
corresponding gain setting of a plurality of gain settings;
selecting, by the sensor circuit, the corresponding gain setting
from among the plurality of gain settings based on the combination
of the first measurement value and the second measurement value;
and setting, by the sensor circuit, the selected corresponding gain
setting as the gain setting of the second amplifier.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Embodiments are described herein making reference to the
appended drawings.
[0011] FIG. 1A illustrates a magnetic field sensing principle using
a pole wheel according to one or more embodiments;
[0012] FIGS. 1B and 1C illustrate a pitch matching principle
according to one or more embodiments;
[0013] FIG. 2 is a schematic block diagram illustrating a magnetic
speed sensor according to one or more embodiments;
[0014] FIG. 3A is a schematic diagram of a first sensor arrangement
with a pre-amplifier according to one or more embodiments;
[0015] FIG. 3B is a schematic diagram of a second sensor
arrangement with a pre-amplifier according to one or more
embodiments; and
[0016] FIG. 3C shows a schematic block diagram of a speed sensor
arrangement and a direction sensor arrangement of a magnetic speed
sensor according to one or more embodiments.
DETAILED DESCRIPTION
[0017] In the following, details are set forth to provide a more
thorough explanation of the exemplary embodiments. However, it will
be apparent to those skilled in the art that embodiments may be
practiced without these specific details. In other instances,
well-known structures and devices are shown in block diagram form
or in a schematic view rather than in detail in order to avoid
obscuring the embodiments. In addition, features of the different
embodiments described hereinafter may be combined with each other,
unless specifically noted otherwise. It is also to be understood
that other embodiments may be utilized and structural or logical
changes may be made without departing from the scope defined by the
claims. The following detailed description, therefore, is not to be
taken in a limiting sense.
[0018] Further, equivalent or like elements or elements with
equivalent or like functionality are denoted in the following
description with equivalent or like reference numerals. As the same
or functionally equivalent elements are given the same reference
numbers in the figures, a repeated description for elements
provided with the same reference numbers may be omitted. Hence,
descriptions provided for elements having the same or like
reference numbers are mutually exchangeable.
[0019] Directional terminology, such as "top", "bottom", "above",
"below", "front", "back", "behind", "leading", "trailing", "over",
"under", etc., may be used with reference to the orientation of the
figures and/or elements being described. Because the embodiments
can be positioned in a number of different orientations, the
directional terminology is used for purposes of illustration and is
in no way limiting. In some instances, directional terminology may
be exchanged with equivalent directional terminology based on the
orientation of an embodiment so long as the general directional
relationships between elements, and the general purpose thereof, is
maintained.
[0020] In the present disclosure, expressions including ordinal
numbers, such as "first", "second", and/or the like, may modify
various elements. However, such elements are not limited by the
above expressions. For example, the above expressions do not limit
the sequence and/or importance of the elements. The above
expressions are used merely for the purpose of distinguishing an
element from the other elements. For example, a first box and a
second box indicate different boxes, although both are boxes. For
further example, a first element could be termed a second element,
and similarly, a second element could also be termed a first
element without departing from the scope of the present
disclosure.
[0021] It will be understood that when an element is referred to as
being "connected" or "coupled" to another element, it can be
directly connected or coupled to the other element or intervening
elements may be present. In contrast, when an element is referred
to as being "directly connected" or "directly coupled" to another
element, there are no intervening elements present. Other words
used to describe the relationship between elements should be
interpreted in a like fashion (e.g., "between" versus "directly
between," "adjacent" versus "directly adjacent," etc.).
[0022] In embodiments described herein or shown in the drawings,
any direct electrical connection or coupling, i.e., any connection
or coupling without additional intervening elements, may also be
implemented by an indirect connection or coupling, i.e., a
connection or coupling with one or more additional intervening
elements, or vice versa, as long as the general purpose of the
connection or coupling, for example, to transmit a certain kind of
signal or to transmit a certain kind of information, is essentially
maintained. Features from different embodiments may be combined to
form further embodiments. For example, variations or modifications
described with respect to one of the embodiments may also be
applicable to other embodiments unless noted to the contrary.
[0023] Depending on certain implementation requirements, a storage
medium may include a RAM, a ROM, a PROM, an EPROM, an EEPROM, a
FLASH memory, or any other medium having electronically readable
control signals stored thereon, which cooperate (or are capable of
cooperating) with a programmable computer system such that the
respective method is performed. Therefore, a storage medium may be
regarded as a non-transitory storage medium that is computer
readable.
[0024] Additionally, instructions may be executed by one or more
processors, such as one or more central processing units (CPU),
digital signal processors (DSPs), general purpose microprocessors,
application specific integrated circuits (ASICs), field
programmable logic arrays (FPGAs), or other equivalent integrated
or discrete logic circuitry. Accordingly, the term "processor," as
used herein refers to any of the foregoing structure or any other
structure suitable for implementation of the techniques described
herein. In addition, in some aspects, the functionality described
herein may be provided within dedicated hardware and/or software
modules. Also, the techniques could be fully implemented in one or
more circuits or logic elements. A "controller," including one or
more processors, may use electrical signals and digital algorithms
to perform its receptive, analytic, and control functions, which
may further include corrective functions.
[0025] A sensor may refer to a component which converts a physical
quantity to be measured to an electric signal, for example, a
current signal or a voltage signal. The physical quantity may for
example comprise a magnetic field, an electric field, a pressure, a
force, a temperature, a current, or a voltage, but is not limited
thereto. A sensor device, as described herein, may be a voltage
sensor, a current sensor, a temperature sensor, a magnetic sensor,
and the like.
[0026] A magnetic field sensor, for example, includes one or more
magnetic field sensor elements that measure one or more
characteristics of a magnetic field (e.g., an amount of magnetic
field flux density, a field strength, a field angle, a field
direction, a field orientation, etc.). The magnetic field may be
produced by a magnet, a current-carrying conductor (e.g., a wire),
the Earth, or other magnetic field source. Each magnetic field
sensor element is configured to generate a sensor signal (e.g., a
voltage signal) in response to one or more magnetic fields
impinging on the sensor element. Thus, a sensor signal is
indicative of the magnitude and/or the orientation of the magnetic
field impinging on the sensor element.
[0027] Magnetic field sensor elements include, but is not limited
to, magneto-resistive sensors, often referred to as XMR sensors
which is a collective term for anisotropic magneto-resistive (AMR),
giant magneto-resistive (GMR), tunneling magneto-resistive (TMR),
etc. The sensor circuit may be referred to as a signal processing
circuit and/or a signal conditioning circuit that receives one or
more signals (i.e., sensor signals) from one or more magnetic field
sensor elements in the form of raw measurement data and derives,
from the sensor signal, a measurement signal that represents the
magnetic field.
[0028] In some cases, a measurement signal may be differential
measurement signal that is derived from sensor signals generated by
two sensor elements having a same sensing axis (e.g., two sensor
elements sensitive to the same magnetic field component) using
differential calculus. A differential measurement signal provides
robustness to homogenous external stray magnetic fields.
[0029] Signal conditioning, as used herein, refers to manipulating
an analog signal in such a way that the signal meets the
requirements of a next stage for further processing. Signal
conditioning may include converting from analog to digital (e.g.,
via an analog-to-digital converter), amplification, filtering,
converting, biasing, range matching, isolation and any other
processes required to make a sensor output suitable for processing
after conditioning.
[0030] Thus, the sensor circuit may include an analog-to-digital
converter (ADC) that converts the analog signal from the one or
more sensor elements to a digital signal. The sensor circuit may
also include a digital signal processor (DSP) that performs some
processing on the digital signal, to be discussed below. Therefore,
a chip, which may also be referred to as an integrated circuit
(IC), may include a circuit that conditions and amplifies the small
signal of one or more magnetic field sensor elements via signal
processing and/or conditioning.
[0031] A sensor device, as used herein, may refer to a device which
includes a sensor and sensor circuit as described above. A sensor
device may be integrated on a single semiconductor die (e.g.,
silicon die or chip). Thus, the sensor and the sensor circuit are
disposed on the same semiconductor die.
[0032] Magnetic field sensors provided herein may be configured for
speed measurements and rotation direction measurements of a
rotating magnetic encoder, such as a wheel or camshaft, referred to
as a target object or target wheel. Magnetic field sensors may also
measure the magnetic phase where one magnetic period is correlated
into 360 degrees.
[0033] One type of magnetic encoder is a pole wheel that consists
of alternating magnets, which are magnetized in opposite directions
(e.g., alternating south-pole and north-pole magnets) and arranged
along a circumference of the encoder. In this case the speed sensor
is placed in front or on the side of the pole wheel where the
distance between the sensor module and the pole wheel is defined by
an air gap. The sensor module detects if the measured magnetic
field changes its polarity. In this case, the speed sensor
generates an output signal that indicates that a pole passed
by.
[0034] FIG. 1A illustrates a magnetic field sensing principle using
a pole wheel according to one or more embodiments.
[0035] A sensor module 1 is a speed sensor that includes a first
sensor element arrangement and a sensor circuit (not shown). The
first sensor element arrangement is a first sensing structure that
includes two differential magnetic field sensor elements, SE1 and
SE2. The sensor signals of each differential sensor element SE1 and
SE2 is provided to the sensor circuit that calculates a
differential measurement signal using a differential calculation
that may be used to cancel out homogeneous stray-fields in the
sensor plane directions. A sensor element pitch is the lateral,
center-to-center, distance between the two magnetic field sensor
elements SE1 and SE2 that are arranged along a rotation direction
of the target object (i.e., the pole wheel 11).
[0036] The sensor arrangement is configured to sense a magnetic
field produced by the pole wheel 11. The sensor arrangement may
generally be referred to herein as speed sensor arrangement and may
further include a sensor circuit (not shown) and may be disposed in
a sensor package.
[0037] The pole wheel 11 is a magnetized encoder wheel that
comprises alternating north pole sections 12 and south pole
sections 13. The sensor elements SE1 and SE2 are sensitive to
magnetic fields influenced by the north pole sections 12 and south
pole sections 13 of the pole wheel 11. A pitch of a pole wheel is
the center-to-center distance along a pitch circle between two
neighboring poles of the same polarity (i.e., between two
neighboring positive poles or two neighboring negative poles). Two
neighboring poles of the same polarity have one pole of opposite
polarity interposed therebetween. Thus, a half-pitch of a pole
wheel is the center-to-center distance along a pitch circle between
two adjacent poles of different (i.e., opposite) polarity. In other
words, the half-pitch is the distance along a pitch circle between
a center of positive pole and a center of a negative pole that is
adjacent to the positive pole.
[0038] For a good system performance, the sensor element pitch of a
sensor integrated circuit (IC) and the wheel half-pitch should
match each other (1:1). In other words, the sensor element pitch
should be half of the wheel pitch (1:2). This ratio provides
improved signal-to-noise ratio.
[0039] In practice, the sensor elements SE1 and SE2 may both have a
sensitivity axis aligned in the x-direction such that they are
sensitive to an x-component Bx of the magnetic field produced by
the pole wheel. As a result of their sensitivity axis being aligned
with the x-component Bx of the magnetic field, the sensor elements
SE1 and SE2 generate electrical signals that are representative of
or proportional to the magnitude of the x-component Bx. The sensor
circuit of the sensor arrangement generates a sensor output that
corresponds to the rotational speed of the magnetized encoder wheel
11 by detecting the change of the alternating magnetic field
produced by alternating north and south poles passing by the sensor
arrangement as the pole wheel 11 rotates about its rotation axis
14.
[0040] As the pole wheel 11 rotates, the positive poles 12 and the
negative poles 13 alternate past the sensor module 1 and the sensor
elements within the sensor arrangement sense a change in the x-axis
or the y-axis magnetic field strength that varies as a sinusoidal
waveform (i.e., as a signal modulation), the frequency of which
corresponds to a speed of rotation of the wheel, and which further
corresponds to a speed of rotation of a drive shaft (e.g.,
camshaft) that drives the rotation of the wheel.
[0041] Thus, the sensor circuit of the sensor arrangement receives
signals (i.e., sensor signals) from the magnetic field sensor
elements SE1 and SE2 and derives, from the sensor signals, a
differential measurement signal that represents the magnetic field
as a signal modulation. The differential measurement signal may
then be output as an output signal to an external controller,
control unit, or processor (e.g., an ECU), or used internally by
the sensor circuit for further processing (e.g., to generate a
pulsed output signal) before being output to the external device.
For example, the external device may count the pulses of the pulsed
output signal and calculate a wheel-speed therefrom. The
differential measurement signal may be referred to as a speed
signal from which the speed of the target object can be
extracted.
[0042] In addition, the sensor module 1 may include a second sensor
arrangement as a second sensing structure that is used to generate
a direction signal indicative, in combination with the speed
signal, of the rotational direction (e.g., clockwise or
counter-clockwise) of the pole wheel 11. Here, the second sensing
structure is comprised of a single, monocell sensor element SE3
(i.e., a third magnetic field sensor element) that is arranged in
the middle between the two differential sensor elements SE1 and SE2
of the first sensing structure to enable the sensor to detection a
rotational direction of the wheel 11. The sensor element SE3 may
also have a sensitivity axis aligned in the x-direction.
[0043] In particular, the first sensor arrangement may be
configured to generate a speed sensor signal and the second sensor
arrangement may be configured to generate a direction sensor signal
that is phase shifted 90.degree. or substantially 90.degree. from
the speed sensor signal. The phase shift between the speed signal
and direction signal can be evaluated by the sensor circuit and the
rotation direction of a target object can be determined based on
whether the phase shift is positive or negative. For example, the
differential sensor elements SE1 and SE2 may be used to generate a
sinusoidal speed signal and the third sensor element SE3 may be
used to generate a sinusoidal (cosinusoidal) direction signal that
is phase shifted 90.degree. from the speed signal. By monitoring
the direction of the phase shift (e.g., positive or negative), the
sensor circuit can determine a rotational direction of the magnetic
field and thus of the target object.
[0044] While the second sensing structure is shown as being formed
by a monocell sensor element, it will be appreciated that the
second sensing structure may also comprise a plurality of sensor
elements that are used to generate a differential sensor signal
that is phase shifted 90.degree. or substantially 90.degree. from
the speed sensor signal, which is also a differential signal. The
phase shift is caused by the geometrical placement of the sensor
elements (e.g., SE1, SE2, and SE3) relative to each other.
[0045] In addition, it will be appreciated that the first sensor
arrangement may be comprised of two or more sensor elements for
generating the speed sensor signal, while the second sensor
arrangement may be comprised of one or more sensor elements for
generating the direction sensor signal. In the event that a sensor
arrangement includes two or more sensing elements, the sensing
elements of each respective sensor arrangement may be arranged in a
differential configuration and/or a bridge configuration. For
example, sensor elements used for generating a speed sensor signal
may include four or more sensor elements arranged in a bridge
configuration that outputs the speed sensor signal as a first
differential signal. Similarly, sensor elements used for generating
a direction sensor signal may include four or more sensor elements
arranged in a bridge configuration that outputs the direction
sensor signal as a second differential signal.
[0046] FIGS. 1B-1C illustrates a pitch matching principle according
to one or more embodiments. As discussed above, FIG. 1A shows a
magnetized encoder wheel 11 and a first sensor arrangement (SE1 and
SE2) that has a sensor element pitch that is matched to the pole
wheel half-pitch 1:1.
[0047] FIG. 1B shows a graph of an oscillating magnetic field that
is generated by the magnetized encoder wheel 11 and projected onto
the wheel speed sensor in a case where the pitches are ideally
matched (i.e., the sensor element pitch that is matched to the pole
wheel half-pitch). As can be seen, the peak-to-peak amplitude of a
differential sensor signal (Bdiff,max) is equal to two times the
maximum amplitude of the x-component Bx of the magnetic field that
can be sensed at the wheel speed sensor (e.g., based on the
constant air gap between the wheel speed sensor and the wheel). The
peak-to-peak amplitude in this case is the maximum value that can
be detected by the sensor.
[0048] FIG. 1C shows a graph of an oscillating magnetic field that
is generated by the magnetized encoder wheel 11 and projected onto
the wheel speed sensor in a case where the pitches are mismatched
(i.e., the sensor element pitch that is not matched to the pole
wheel half-pitch). As can be seen, the peak-to-peak amplitude of a
differential sensor signal (Bdiff,max) is damped with respect to
the peak-to-peak amplitude shown in FIG. 1B. Thus, the peak-to-peak
amplitude in FIG. 1C is less than two times the maximum amplitude
of the x-component Bx of the magnetic field that could conceivably
be sensed at the wheel speed sensor (e.g., based on the constant
air gap between the wheel speed sensor and the wheel) if not for
the pitch mismatch.
[0049] Further embodiments are described that are capable of
determining the wheel pitch and performing compensation on a sensor
signal based on the determined wheel pitch or half-pitch. For speed
sensors, such as anti-lock braking system (ABS) speed sensors,
direction detection is also present. The speed sensor signal and
the direction sensor signal are converted to digital signals (i.e.,
digital values) by the sensor circuit (e.g., including an ADC) and
the sensor circuit is further configured to determine the wheel
pitch via look-up table, by dividing the two values and checking in
a lookup table, or by some other algorithm.
[0050] FIG. 2 is a schematic block diagram illustrating a magnetic
speed sensor 100 according to one or more embodiments. The magnetic
speed sensor 100 includes sensor arrangement S and sensor
arrangement D that are each configured to generate a differential
sensor signal in response to a magnetic field impinging thereon. In
particular, sensor arrangement S may include a first group of
magnetic field sensor elements arranged in a bridge circuit
configuration and is configured to generate a speed sensor signal.
Similarly, sensor arrangement D may include a second group of
magnetic field sensor elements arranged in a bridge circuit
configuration and is to generate a direction sensor signal that is
phase shifted, for example by 90.degree., from the speed sensor
signal. The phase shift between the speed signal and direction
signal can be evaluated and the rotation direction of a target
object can be determined based on whether the phase shift is
positive or negative. It will also be appreciated that sensor
arrangement D may be a monocell magnetic sensor element (i.e.,
comprising only a single sensor element), as described above. When
sensor arrangement D is a monocell magnetic sensor, the sensor
signal generated by the monocell sensor element is used as the
direction signal.
[0051] The sensor arrangements S and D shown in FIG. 2 may each
represent a magnetoresistor bridge that includes a corresponding
set of sensor elements that are arranged in a bridge configuration.
Sensor elements of sensor arrangement S and are configured to
measure magnetic fields according to a same sensing plane (e.g.,
x-plane, y-plane, or z-plane). Similarly, sensor elements of sensor
arrangement D and are configured to measure magnetic fields
according to a same sensing plane (e.g., x-plane, y-plane, or
z-plane). That is, the sensor elements that make up a bridge have
reference directions that are aligned with a same sensing
plane.
[0052] The magnetic speed sensor 100 also includes a sensor circuit
20 that receives the sensor signals from the sensor arrangements S
and D for processing and for generation of pulsed output speed
signal and a direction indicator signal at output OUT. The sensor
circuit 20 includes two signal paths: an S signal path and a D
signal path. The differential speed (S) signal on the S signal path
may be in a form of a sinusoidal (sine) waveform that represents a
speed of rotation of the target object, and the differential
direction (D) signal on the D signal path may be a similar waveform
that is phase shifted, for example 90.degree., from the speed
signal. For example, the direction signal may a cosinusoidal
waveform that represents a speed of rotation of the target object,
but is used by a digital signal processor 27 to determine the
direction of rotation by analyzing the phase difference between the
speed signal and the direction signal.
[0053] Signal paths S and D may each include a pre-amplifier Asp 21
and Adir 22, differential comparators 23 and 24 that output their
respective differential signals to respective ADCs 25 and 26.
[0054] The sensor arrangement S generates differential sensor
signals that have a differential measurement value therebetween,
such as a voltage difference Vdiff,speed. The pre-amplifier Asp 21
amplifies these differential sensor signals according to a set gain
and provides the amplified differential sensor signals to the
differential comparator 23. The differential comparator 23 converts
the differential sensor signals to an analog differential
measurement signal having a value equal to the voltage difference
Vdiff,speed. The ADC 25 converts the analog differential
measurement signal into the digital domain, specifically, into a
digital differential measurement signal representative of the
voltage difference Vdiff,speed.
[0055] Similarly, the sensor arrangement D generates at least one
sensor signal. In the event that the sensor arrangement D is a
monocell arrangement, a signal sensor element is provided to
generate a sensor signal that is phase shifted 90.degree. from the
analog differential measurement signal of the speed signal path. In
this case, the differential comparator 24 would not be needed.
Instead, the pre-amplifier Adir 22 amplifies the sensor signal
received from sensor arrangement D according to a set gain, and the
ADC 26 converts the amplified sensor signal into the digital
domain. As a result, signal processor 27 receives a first digital
signal from the speed path and a second digital signal from the
direction path that is phase shifted from the first digital signal
by a predetermined phase shift (e.g., 90.degree.).
[0056] Alternatively, sensor arrangement D may generate
differential sensor signals, for example via bridge arrangement,
where the differential sensor signals have a differential
measurement value therebetween, such as a voltage difference
Vdiff,dir. The pre-amplifier Asp 22 amplifies these differential
sensor signals according to a set gain and provides the amplified
differential sensor signals to the differential comparator 24. The
differential comparator 24 converts the differential sensor signals
to an analog differential measurement signal having a value equal
to the voltage difference Vdiff,dir. The ADC 26 converts the analog
differential measurement signal into the digital domain,
specifically, into a digital differential measurement signal
representative of the voltage difference Vdiff,dir. As a result,
signal processor 27 receives a first digital signal (i.e., a
digital speed signal Dsp) from the speed path and a second digital
signal (i.e., a digital direction signal Ddir) from the direction
path that is phase shifted from the first digital signal by a
predetermined phase shift (e.g., 90.degree.).
[0057] The digital signal processor 27 is configured to receive the
digital speed signal and the digital direction signal for further
processing, including determining a speed and a rotation direction
of the target object. Additionally, the signal processor 27 is
configured to automatically determine the wheel pitch based on the
speed signal and the direction signal, and further compensate or
condition the speed signals and/or the direction signals based on
the determined wheel pitch. For example, the digital signal
processor 23 may include one or more processors and/or logic units
that performs various signal conditioning functions, such as
absolute signal conversion, normalization, linearization, frequency
increase, and so forth. One or more signal conditioning functions
may be performed in combination with a lookup table stored in
memory. The output OUT of the digital signal processor 27 may
provide one or more output signals to an external device, such as
an ECU.
[0058] For example, the speed of rotation of the target object may
be output as a speed pulse signal. Thus, the sinusoidal signal
generated by the sensor arrangement S may be translated by the
signal processor 27 into pulses, which may be further translated
into a movement detection or a speed output. In addition, the
signal processor 27 may output a signal that indicates a rotation
direction, based on evaluating the phase shift between the digital
speed signal and the digital direction signal.
[0059] In order to determine the wheel pitch, the signal processor
27 evaluates a difference between an amplitude of the digital speed
signal Dsp and an amplitude of the digital direction signal Ddir.
For example, the signal processor 27 may use one or more look-up
tables to evaluate the difference, may use a coordinate rotation
digital computer (CORDIC) operation that calculates a ratio R of
the digital speed signal Dsp and the digital direction signal Ddir
(e.g., R=Dsp/Ddir or R=Dir/Dsp), or may use a combination thereof.
Based on the determined wheel pitch, the signal processor 27 adapts
the gain setting of the pre-amplifier Adir 22 via a gain controller
28 so that the ratio R approaches or equals 1:1. In other words,
the gain controller 28 is configured to adjust the amplification of
the pre-amplifier Adir 22 so that the maximum and minimum
amplitudes of the digital direction signal Ddir are substantially
equal to the maximum and minimum amplitudes of the digital speed
signal Dspeed. By doing so, the signal processor 27 enables the
sensor 100 to automatically adapt to different pole wheel pitches
to optimize the signal performance according to the ideal pitch
matching demonstrated in FIG. 1B.
[0060] FIG. 3A is a schematic diagram of a first sensor arrangement
with a pre-amplifier according to one or more embodiments. FIG. 3B
is a schematic diagram of a second sensor arrangement with a
pre-amplifier according to one or more embodiments. FIG. 3C shows a
schematic block diagram of a speed sensor arrangement and a
direction sensor arrangement of a magnetic speed sensor according
to one or more embodiments.
[0061] Specifically, the first sensor arrangement corresponds to
the sensor arrangement S including four sensor elements S1-S4
arranged in a first bridge configuration connected between a first
and a second supply terminal, and the second sensor arrangement
corresponds to the sensor arrangement D including six sensor
elements D1-D6 arranged in a second bridge configuration connected
between the first and the second supply terminal. It will be
appreciated that the sensor arrangement S and D are neither limited
in the number of sensor elements or to the particular bridge
configurations shown.
[0062] The magnetic sensor bridge circuit S comprises a first
magnetoresistive sensor element S1 and a fourth magnetoresistive
sensor element S4. The first and the fourth magnetoresistive sensor
elements S1 and S4 are connected in series. Furthermore, the
magnetic sensor bridge circuit S comprises a second
magnetoresistive sensor element S2 and a third magnetoresistive
sensor element S3. The second and the third magnetoresistive sensor
elements S2 and S3 are connected in series. The first and the third
magnetoresistive sensor elements S1 and S3 are connected to a first
supply terminal of the magnetic sensor bridge circuit X. The second
and the fourth magnetoresistive sensor elements S2 and S4 are
connected to a second, different supply terminal of the magnetic
sensor bridge circuit S.
[0063] The magnetic sensor bridge circuit D comprises a first
magnetoresistive sensor element D1 and a second magnetoresistive
sensor element D2 connected in parallel and further connected in
series with a third magnetoresistive sensor element D3.
Furthermore, the magnetic sensor bridge circuit D comprises a
fourth magnetoresistive sensor element D4 connected in series with
a fifth magnetoresistive sensor element D5 and a sixth
magnetoresistive sensor element D6 that are connected in parallel
with each other. Connections to the first and the second supply
terminals are also provided.
[0064] The differential sensor signals generated by sensor
arrangement S and D are amplified by respective pre-amplifiers Asp
21 and Adir 22. The amplified differential sensor signals have a
differential value therebetween, represented by Vdiff,speed and
Vdiff,dir, respectively. The gain setting of the pre-amplifier Adir
22 is adjustable such that the extrema of Vdiff,dir is equal to or
substantially equal to the extrema of Vdiff,speed, albeit shifted
90.degree. from each other.
[0065] FIG. 3C illustrates an example arrangement of sensor
elements S1-S4 and D1-D6 linearly arranged on a sensor chip (e.g.,
on an x-axis), where the sensor elements are placed in three
different regions: a left region, a center region, and a right
region. The geometric center of the sensor arrangements is located
at a first geometric center of the center sensor elements D3 and
D4. The effective sensor element pitch is defined by the distance
between a second geometric center of the left sensor elements and a
third geometric center of the right sensor elements. The second and
third geometric centers are equidistant from the first geometric
center.
[0066] Equation 1 provided below is a formula for calculating a
damping factor for the speed signal according to a matching of the
pole wheel pitch (pitch.sub.PW) to the effective sensor element
pitch (pitch.sub.SE) by a ratio of 1:2 (i.e., the effective sensor
element pitch is matched to the pole wheel half-pitch). Equation 2
provided below is a formula for calculating a damping factor for
the direction signal according to a matching of the pole wheel
pitch (pitch.sub.PW) to the effective sensor element pitch
(pitch.sub.SE) by a ratio of 1:2 (i.e., the effective sensor
element pitch is matched to the pole wheel half-pitch). Equation 3
provided below is a formula for calculating a pitch mismatch
dependent ratio by dividing Equation 2 by Equation 1.
B diff , sp B x = 2 sin .function. ( pitch SE pitch PW .pi. ) Eq .
.times. 1 B diff , dir B x = 1 - cos .function. ( pitch SE pitch PW
.pi. ) Eq . .times. 2 B diff , dir B diff , sp = 1 2 1 - cos
.function. ( pitch SE pitch PW .pi. ) sin .function. ( pitch SE
pitch PW .pi. ) Eq . .times. 3 ##EQU00001##
[0067] As noted above, the signal processor may implement a look-up
table method for detecting a pole wheel pitch and adjusting the
gain of the pre-amplifier Adir 22 according to the detected pole
wheel pitch. Two or more pole wheel pitches may be known and
programmed into the look-up table. In the following examples, wheel
pitches 4.4 mm and 5.7 mm are correlated to total amplitude values
of the digital measurement signals Dsp and Ddir (see: look-up table
1) or to the value of the least significant bit (LSB) of the
digital measurement signals Dsp and Ddir (see: look-up table
2).
TABLE-US-00001 LOOK-UP TABLE 1 Row # Dsp [.mu.T] Ddir_4.4 mm
[.mu.T] Ddir_5.7 mm [.mu.T] 1 180 56 41 2 232 72 53 3 299 92 68 . .
. . . . . . . . . .
[0068] According to look-up table 1, the signal processor 27 is
configured to discrimination between two predefined wheel pitches
and detect which wheel pitch is present before the speed sensor
100. To make the determination, the signal processor 27 is
configured to select a row of the table based on the measured
amplitude value of the digital speed signal Dsp. Once a row is
selected, the signal processor 27 evaluates the measured amplitude
value of the digital direction signal Ddir to select a
corresponding wheel pitch identified in the second and third
columns. For example, if an amplitude value of the digital speed
signal Dsp is 102, the second row is selected. Following the
selection of the second row, an amplitude value of 95 for the
digital direction signal Ddir indicates that the wheel pitch is 4.4
mm and an amplitude value of 70 for the digital direction signal
Ddir indicates that the wheel pitch is 5.7 mm. Based on the
determination of the wheel pitch, the gain controller 28 is
configured to set a gain setting of the pre-amplifier Adir 22 for
the direction signal that is predefined for the wheel pitch. That
is, each programmed wheel pitch has a corresponding gain setting
that is implemented by the gain controller 28.
TABLE-US-00002 LOOK-UP TABLE 2 Row # Dsp [LSB] Ddir_4.4 mm [LSB]
Ddir_5.7 mm [LSB] 1 79 73 54 2 102 95 70 3 132 122 90 . . . . . . .
. . . . .
[0069] A similar procedure can be implemented by using the least
significant bits (LSB) of the digital speed signal Dsp and the
digital direction signal Ddir of a predetermined number of bits, as
demonstrated by look-up table 2. Here, "LSB" represents the number
of bits of the ADC that digitizes the speed and the direction
signals. The ADC output has a range [0; 2.sup.N-1], wherein N is
the number of bits of the ADC. Thus, the digital values to be
compared with the digital values output by the ADCs 25 and 26 are
provided in the above table.
[0070] The rule in order to build a correct look-up table consists
of not making overlapping the ranges of the Ddir_4.4 mm
(differential speed field range in case of wheel pitch 4.4 mm) with
the ranges of Ddir_5.7 mm (differential direction field range in
case of wheel pitch 5.7 mm). Since the amplitude values will be
bigger if the wheel pitch of the reference wheel is smaller, the
values in column Ddir_4.4 mm will be greater than their
corresponding values in column Ddir_5.7 mm within the same row.
[0071] The signal processor 27 may also apply a pseudo-code for
changing the applied gain to the direction preamplifier Adir 22.
One example of pseudo-code is provided as follows:
TABLE-US-00003 dir_gain_pre-amp=24; // default setting Ddir_4.4mm
if Dsp < 102 if Ddir < 70 dir_gain_pre-amp=32; //Ddir_5.7mm
else if Dsp < 132 if Ddir < 90 dir_gain_pre-amp=32;
//Ddir_5.7mm else if Dsp < 145 if Ddir < 116
dir_gain_pre-amp=32; //Ddir_5.7mm
[0072] Thus, a string of if then else statements may be formalized
or realized by a logic circuit that is used to discriminate the
wheel pitch and select a corresponding gain setting based on the
combination of the first measurement value and the second
measurement value satisfying one of the if then else statements.
The if then else statements may be used in code to confirm specific
conditions for applying different gain settings (dir_gain_pre-amp)
for the direction preamplifier Adir 22. The signal processor 27 is
configured to select the corresponding gain setting based on if
then else statements, where the signal processor selects the
corresponding gain setting based on a combination of the digital
speed signal Dsp (e.g., an amplitude value thereof) and the digital
direction signal Ddir (e.g., an amplitude value thereof) satisfying
one of the if then else statements. Additional lines of code (e.g.,
additional logic in the logic circuit) can be added for additional
gain settings corresponding to additional wheel pitches, where
additional conditions based on speed and direction signal
amplitudes are added to discriminate the correct wheel pitch.
[0073] In addition, CORDIC operations are capable of calculating
the division between two values. Thus, the signal processor 27 may
be configured to divide the speed signal amplitude by the direction
signal amplitude to determine a ratio. In case of a wheel pitch of
4.4 mm, the ratio is close to 1 because the direction path is
designed in order to have an almost one-to-one LSB14 signal
amplitude in the digital domain. If the division between speed and
direction amplitudes result in ratio equal to or larger that a
predefined ratio (e.g., equal to or larger than 1.3), the signal
processor 27 is configured to increase the direction
pre-amplification gain setting from 24 to 32, with 32 being the
optimized amplification for a wheel pitch of 5.7 mm in this example
and 24 being the optimized amplification for a wheel pitch of 4.4
mm. On the other hand, if the ratio is less than the predefined
ratio (e.g., less than 1.3), the signal processor 27 is configured
to set, maintain, or decrease the direction pre-amplification to a
gain setting of 24. It will be appreciated that the number of ratio
constants or ratio ranges increases with the number of possible
pre-amplification options and the number of pole wheel pitches
available. That is, as a number of ratio ranges increases and the
ratio range thereof may become narrower as more wheel pitches are
programmed. Thus, multiple ratio ranges may be defined according to
the number of wheel pitches to be discriminated by the signal
processor 27.
[0074] In view of the above, there a plurality of ways the signal
processor 27 can correlate a combination of the digital speed
signal Dsp (e.g., an amplitude value thereof) and the digital
direction signal Ddir (e.g., an amplitude value thereof) to a
corresponding gain setting of a plurality of gain settings, select
the corresponding gain setting from among the plurality of gain
settings based on the combination of digital speed and direction
values, and set the selected corresponding gain setting as the gain
setting of the direction preamplifier Adir 22.
[0075] The pole wheel pitch may be determined either explicitly or
implicitly via look-up, code, and/or arithmetic where the direction
amplifier gain is selected based on the explicit or implicit
determination of the wheel pitch. If explicitly determined, each
pole wheel pitch may be explicitly mapped to a corresponding
direction amplifier gain. Implicit mappings may also exist without
the explicit determination of the pole wheel pitch. Each of the
plurality of gain settings stored in memory of the sensor circuit
20 corresponds to one of a plurality of pole wheel pitches
programmed in the memory of the sensor circuit 20. Thus, the
plurality of gain settings are available to the signal processor 27
(e.g., to the gain controller 28) for selection based on a
selection algorithm.
[0076] While various embodiments have been disclosed, it will be
apparent to those skilled in the art that various changes and
modifications can be made which will achieve some of the advantages
of the concepts disclosed herein without departing from the spirit
and scope of the invention. It will be obvious to those reasonably
skilled in the art that other components performing the same
functions may be suitably substituted. It is to be understood that
other embodiments may be utilized and structural or logical changes
may be made without departing from the scope of the present
invention. It should be mentioned that features explained with
reference to a specific figure may be combined with features of
other figures, even in those not explicitly mentioned. Such
modifications to the general inventive concept are intended to be
covered by the appended claims and their legal equivalents.
[0077] Furthermore, the following claims are hereby incorporated
into the detailed description, where each claim may stand on its
own as a separate example embodiment. While each claim may stand on
its own as a separate example embodiment, it is to be noted
that--although a dependent claim may refer in the claims to a
specific combination with one or more other claims--other example
embodiments may also include a combination of the dependent claim
with the subject matter of each other dependent or independent
claim. Such combinations are proposed herein unless it is stated
that a specific combination is not intended. Furthermore, it is
intended to include also features of a claim to any other
independent claim even if this claim is not directly made dependent
to the independent claim.
[0078] It is further to be noted that methods disclosed in the
specification or in the claims may be implemented by a device
having means for performing each of the respective acts of these
methods. For example, the techniques described in this disclosure
may be implemented, at least in part, in hardware, software,
firmware, or any combination thereof. For example, various aspects
of the described techniques may be implemented within one or more
processors, including one or more microprocessors, DSPs, ASICs, or
any other equivalent integrated or discrete logic circuitry, as
well as any combinations of such components.
[0079] Further, it is to be understood that the disclosure of
multiple acts or functions disclosed in the specification or in the
claims may not be construed as to be within the specific order.
Therefore, the disclosure of multiple acts or functions will not
limit these to a particular order unless such acts or functions are
not interchangeable for technical reasons. Furthermore, in some
embodiments a single act may include or may be broken into multiple
sub acts. Such sub acts may be included and part of the disclosure
of this single act unless explicitly excluded.
* * * * *