U.S. patent application number 17/371908 was filed with the patent office on 2022-01-13 for inductive position sensor comprising at least one transmit coil, an absolute position receive coil pair, a high-resolution position receive coil pair and a conductive moving target.
This patent application is currently assigned to Renesas Electronics America Inc.. The applicant listed for this patent is Renesas Electronics America Inc.. Invention is credited to Andreas Buchinger, Bence Gombor, Harald Hartl, Ruggero Leoncavallo, Rudolf Pichler.
Application Number | 20220011085 17/371908 |
Document ID | / |
Family ID | |
Filed Date | 2022-01-13 |
United States Patent
Application |
20220011085 |
Kind Code |
A1 |
Pichler; Rudolf ; et
al. |
January 13, 2022 |
INDUCTIVE POSITION SENSOR COMPRISING AT LEAST ONE TRANSMIT COIL, AN
ABSOLUTE POSITION RECEIVE COIL PAIR, A HIGH-RESOLUTION POSITION
RECEIVE COIL PAIR AND A CONDUCTIVE MOVING TARGET
Abstract
An inductive position sensor including at least one transmit
coil, an absolute position receive coil pair, a high-resolution
position receive coil pair and a conductive moving target, the
absolute position receive coil pair and the high-resolution receive
coil pair together define a measurement area of the inductive
position sensor and the moving target can move in this measurement
area, the absolute position coil pair has a first sine receive coil
and a first cosine receive coil, both having one period over the
measurement area of the inductive position sensor, the
high-resolution position receive coil pair has a second sine
receive coil and a second cosine receive coil, both having at least
two periods over the measurement area of the inductive position
sensor, the absolute position receive coil pair and the
high-resolution position receive coil pair are arranged in the same
area of a printed-circuit board of the inductive position
sensor.
Inventors: |
Pichler; Rudolf;
(Stallhofen, AT) ; Buchinger; Andreas;
(Waldhofen/Ybbs, AT) ; Leoncavallo; Ruggero;
(Gratkorn, AT) ; Gombor; Bence; (Graz, AT)
; Hartl; Harald; (Graz-Strassgang, AT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Renesas Electronics America Inc. |
Milpitas |
CA |
US |
|
|
Assignee: |
Renesas Electronics America
Inc.
Milpitas
CA
|
Appl. No.: |
17/371908 |
Filed: |
July 9, 2021 |
International
Class: |
G01B 7/00 20060101
G01B007/00; H01F 5/00 20060101 H01F005/00; G01D 5/20 20060101
G01D005/20 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 10, 2020 |
EP |
20185164.9 |
Jun 10, 2021 |
EP |
21178772.6 |
Claims
1. An inductive position sensor comprising: at least one transmit
coil, an absolute position receive coil pair, a high-resolution
position receive coil pair and a conductive moving target, wherein
the absolute position receive coil pair and the high-resolution
receive coil pair together define a measurement area of the
inductive position sensor and the moving target can move in this
measurement area, wherein the absolute position coil pair has a
first sine receive coil and a first cosine receive coil, both
having one period over the measurement area of the inductive
position sensor, wherein the high-resolution position receive coil
pair has a second sine receive coil and a second cosine receive
coil, both having at least two periods over the measurement area of
the inductive position sensor, and wherein the absolute position
receive coil pair and the high-resolution position receive coil
pair are arranged in the same area of a printed-circuit board of
the inductive position sensor.
2. The inductive position sensor according to claim 1, wherein the
inductive position sensor is a radial position sensor and the
measurement area is a 360.degree. circle.
3. The inductive position sensor according to claim 1, wherein the
inductive position sensor is a linear position sensor and the
measurement area is a straight line.
4. The inductive position sensor according to claim 1, further
comprising a signal processing unit, for providing a signal to the
at least one transmit coil and/or for processing the signals of the
absolute position receive coil pair and the high-resolution receive
coil pair.
5. The inductive position sensor according to claim 4, wherein the
signal processing unit is arranged on the same printed-circuit
board as the inductive position sensor or externally connected to
the printed-circuit board of the inductive position sensor.
6. The inductive position sensor according to claim 1, wherein the
conductive moving target comprises multiple sections spaced apart
from each other.
7. The inductive position sensor according to claim 6, wherein the
multiple sections of the conductive moving target have the same
shape and/or spacing.
8. The inductive position sensor according to claim 1, wherein the
conductive moving target comprises at least one first target
element and at least one second target element, wherein the shape
of the at least one first target element is different to the shape
of the at least one second target element.
9. The inductive position sensor according to claim 8, wherein the
multiple sections of the at least one first target element covers
the complete measurement area of the inductive position sensor or
the measurement area of the inductive position sensor not covered
by the at least one second target element.
10. The inductive position sensor according to claim 8, wherein the
at least one second target element covers a part of the measurement
area of the inductive position sensor.
11. The inductive position sensor according to claim 10, wherein
the at least one second target element has a semi-circular shape,
an arc segment of a full ring shape, a rectangular shape or an
arrow shape.
12. The inductive position sensor according to claim 8, wherein the
at least one first target element and the at least one second
target element are arranged next to each other or are at least
partially overlapping each other.
13. The inductive position sensor according to claim 12, wherein
the at least one first target element and the at least one second
target element are totally overlapping but having different sizes.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The subject application claims priority to European Patent
Application No. EP20185164.9, filed on Jul. 10, 2020, and European
Patent Application No. EP21178772.6, filed on Jun. 10, 2021. The
disclosures of European Patent Application No. EP20185164.9 and
European Patent Application No. EP21178772.6 are incorporated
herein by this reference.
BACKGROUND
[0002] The invention relates to an inductive position sensor
comprising at least one transmit coil, an absolute position receive
coil pair, a high-resolution position receive coil pair and a
conductive moving target. The invention further relates to a use of
such an inductive position sensor.
[0003] Inductive position sensors are very popular because of their
robustness against environmental influences. Especially for
through-shaft applications the inductive sensors are attractive
because of the design flexibility in coil design which easily
allows to adapt for example on-axis and off-axis position sensing
applications.
[0004] These benefits are a big advantage in many industrial or
automotive applications. But often for industrial or robotics
applications a higher output resolution is needed which only one
absolute inductive position sensor is not capable of. As well some
automotive applications require absolute high-resolution sensors
like steering sensors or sensors for wheel hub traction motors.
[0005] An inductive position sensor setup usually consists of a
sensor printed circuit board (PCB) inside a housing and a
conductive target moving near to the sensor.
[0006] The sensor PCB includes a signal conditioning and processing
unit which is usually an application-specific integrated circuit
(ASIC) and a sensor coil system connected to the ASIC. The sensor
coil system consisting of one or more transmit coils and one or
more receive coils. Typically, there is one transmitter coil and
two receiver coils. The two receiver coils are arranged such that
one generates a sine and the other a cosine signal every
360.degree. mechanical rotation of the target for a rotational
position sensor. This configuration provides the absolute position
of the target (absolute embodiment). By increasing the number of
receiver coil pattern over the 360.degree. and an appropriate
target configuration it is possible to increase the mechanical
accuracy and resolution of the measurement per rotation by
generating a number of signal repetition equal to the number of
physical repetition of the sine and cosine signal repetitions
(multi-period embodiment). In contrast by using such a method the
absolute position of the target gets lost
[0007] Generally, state of the art sensor can be implemented by
using two separate absolute and incremental sensors and separate
targets or by using two separate coil systems next to each other,
but such implementation has quite high space requirement.
[0008] The drawbacks of separate sensors are for example: Thicker
sensor, 2.times.PCB, 2.times.target, additional wiring to connect
to the evaluation unit--MCU, leads to higher cost. The drawbacks of
separate coils next to each other are for example: size of the PCB
(cost), limited chances to scale it down.
[0009] It is therefore an object of the present invention to
provide an inductive position sensor providing absolute and
high-resolution position data and requiring minimum space on a
printed-circuit board.
SUMMARY
[0010] According to the invention the object is solved by an
inductive position sensor comprising at least one transmit coil, an
absolute position receive coil pair, a high-resolution position
receive coil pair and a conductive moving target,
[0011] wherein the absolute position receive coil pair and the
high-resolution receive coil pair together define a measurement
area of the inductive position sensor and the moving target can
move in this measurement area,
[0012] wherein the absolute position coil pair has a first sine
receive coil and a first cosine receive coil, both having one
period over the measurement area of the inductive position
sensor,
[0013] wherein the high-resolution position receive coil pair has a
second sine receive coil and a second cosine receive coil, both
having at least two periods over the measurement area of the
inductive position sensor,
[0014] wherein the absolute position receive coil pair and the
high-resolution position receive coil pair are arranged in the same
area of a printed-circuit board of the inductive position
sensor.
[0015] The invention describes a new way of combining a lower
resolution absolute sensor with a high-resolution incremental
sensor. Generally, it is simply possible by just using a
combination of an absolute inductive position sensor next to an
incremental high-resolution position sensor, but this approach
needs a lot of space which is typically not available.
[0016] This invention is about an innovative embodiment which
consists of overlapping the absolute position sensor with the
multi-period high-resolution sensor to increase the mechanical
accuracy and resolution without losing the absolute position. As a
result a high-accuracy, high-resolution absolute sensor can be
designed.
[0017] The new implementation according to the invention
incorporates both absolute and high-resolution coil at the same PCB
area.
[0018] The benefits are for example: [0019] Implementation within
smaller space possible: 1.times.PCB, 1.times.target, evaluation
unit can be located on the same PCB, much easier to scale it
physically down; [0020] On-axis, through-shaft and side-shaft
applications are possible; [0021] Redundant implementation is
possible; [0022] High robustness against environmental influences;
[0023] Immune against magnetic strayfields; [0024] Higher output
resolution compared to an absolute position sensor without high
resolution coil.
[0025] Pursuant to a variant of the invention the inductive
position sensor is a radial position sensor and the measurement
area is a 360.degree. circle.
[0026] According to an alternative variant of the invention the
inductive sensor is a linear position sensor and the measurement
area is a straight line.
[0027] In a preferred variant the inductive position sensor
comprises a signal processing unit, for providing a signal to the
at least one transmit coil and/or for processing the signals of the
absolute position receive coil pair and the high-resolution receive
coil pair. The signal processing unit is arranged on the same
printed-circuit board as the inductive position sensor or
externally connected to the printed-circuit board of the inductive
position sensor.
[0028] The sensor configuration can be used with different target
configuration. The performance of the implementation strongly
depends on the target configuration.
[0029] In an advantageous variant of the invention the conductive
target comprises multiple sections spaced apart from each other.
Preferably, the multiple sections of the conductive moving target
have the same shape and/or spacing.
[0030] According to a preferred variant of the invention the moving
target comprises at least one first target element and at least one
second target element, wherein the shape of the at least one first
target element is different to the shape of the at least one second
target element. The at least one first target element and the at
least one second target element are preferably arranged on a common
substrate, like a printed-circuit board. For example, the first
target element and/or the second target element comprise multiple
sections.
[0031] In a particularly preferred variant of a radial inductive
position sensor according to the invention the radial area covered
by the at least one first target element, particularly of each
section of the at least one first target element, is constant in
the radial direction, i.e. the width of each section increases
constantly from the center to the radial outside.
[0032] Pursuant to a variant of the invention the at least one
first target element, particularly the multiple sections of the at
least one first target element, covers the complete measurement
area of the inductive position sensor or the measurement area of
the inductive position sensor not covered by the at least one
second target element.
[0033] According to a variant of the invention the at least one
second target element covers a part of the measurement area of the
inductive position sensor. Preferably, the at least one second
target element has a semi-circular shape, an arc segment of a full
ring shape, a rectangular shape or an arrow shape.
[0034] In a particularly preferred variant of a radial inductive
position sensor according to the invention the radial area covered
by the at least one second target element changes in the radial
direction, i.e. for example the width of the at least one second
target element is constant in the radial direction (rectangular) or
changes in a rate different than the radially covered area
(arrow).
[0035] Pursuant to a variant of the invention the at least one
first target element and the at least one second target element are
arranged next to each other or are at least partially overlapping
each other.
[0036] In a further variant of the invention the at least one first
target element and the at least one second target element are
totally overlapping but having different sizes. Particularly, one
target element is bigger than the other target element, so that the
bigger target element completely covers the smaller target
element.
[0037] The invention further relates to a use of an inductive
position sensor according to the invention together with another
inductive position sensor according to the invention or any other
position sensor to calculate further output signals such as torque,
diagnostic information or error compensation.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS In the
following the invention will be further explained with respect to
the embodiments shown in the attached figures. It shows:
[0038] FIG. 1 a schematic view of a first embodiment of an
inductive position sensor according to the invention;
[0039] FIG. 2 a schematic view of a second embodiment of an
inductive position sensor according to the invention;
[0040] FIG. 3 a first embodiment of a conductive moving target;
[0041] FIG. 4 a second embodiment of a conductive moving
target;
[0042] FIG. 5 a third embodiment of a conductive moving target;
[0043] FIG. 6 a fourth embodiment of a conductive moving
target;
[0044] FIG. 7 a fifth embodiment of a conductive moving target;
[0045] FIG. 8 a sixth embodiment of a conductive moving target;
[0046] FIGS. 9a, 9b performance comparisons for different
embodiments of the conductive moving target;
[0047] FIG. 10 outputs of an inductive position sensor according to
the invention after signal processing; and
[0048] FIG. 11 a schematic view of a third embodiment of an
inductive position sensor according to the invention.
DETAILED DESCRIPTION
[0049] FIG. 1 shows a schematic view of a first embodiment of an
inductive position sensor 1 according to the invention. The
inductive position sensor 1 comprises a transmit coil 2, an
absolute position receive coil pair 3, 4, a high-resolution receive
coil pair 5,6 and a conductive moving target 7. The absolute
position receive coil pair 3, 4 and the high-resolution receive
coil pair 5, 6 together define a measurement area of the inductive
position sensor 1 and the moving target 7 can move in this
measurement area. The first embodiment shown in FIG. 1 refers to a
radial inductive position sensor 1 and the measurement area is a
360.degree. circle.
[0050] The absolute position coil pair 3, 4 has a first sine
receive coil 3 and a first cosine receive coil 4, both 3, 4 having
one period over the measurement area of the inductive position
sensor 1. The high-resolution position receive coil pair 5, 6 has a
second sine receive coil 5 and a second cosine receive coil 6, both
5, 6 having at least two periods over the measurement area of the
inductive position sensor 1. According to the embodiment shown in
FIG. 1 the second sine receive coil 5 and a second cosine receive
coil 6 each have 8-periods over the measurement area.
[0051] According to the present invention the absolute position
receive coil pair 3, 4 and the high-resolution position receive
coil pair 5, 6 are arranged in the same area of a printed-circuit
board 8 of the inductive position sensor 1.
[0052] The inductive position sensor 1 shown in FIG. 1 further
comprises a signal processing unit 9, for providing a signal to the
at least one transmit coil 2 and for processing the signals of the
absolute position receive coil pair 3, 4 and the high-resolution
receive coil pair 5, 6. According to the embodiment shown in FIG. 1
the signal processing unit 9 is externally connected to the
printed-circuit board 8 of the inductive position sensor 1. In an
alternative embodiment of the invention the signal processing unit
9 is arranged on the same printed-circuit board 8 as the inductive
position sensor 1. The connections between the signal processing
unit 9 and the transmit coil 2, the absolute position receive coil
pair 3, 4 and the high-resolution receive coil pair 5, 6 have been
numbered identically to the respective coil. During use of the
inductive position sensor 1 shown in FIG. 1 the signal processing
unit 9 provides an excitation current to the transmit coil 2, which
creates an electro-magnetic field due to the excitation current.
The conductive moving target 7 is located inside this created
electro-magnetic field of the transmit coil 2 and therefore
modifies the electro-magnetic field due to eddy currents induced
into the conductive moving target 7. The absolute position receive
coil pair 3, 4 and the high-resolution receive coil pair 5, 6 can
sense the modifications in the electro-magnetic field due to the
conductive moving target 7 and the position of the conductive
moving target 7. The signals of the absolute position receive coil
pair 3, 4 and the high-resolution receive coil pair 5, 6 are used
by the signal processing unit 9 to determine the absolute position
and the high-resolution position of the conductive moving target 7
in the measurement area.
[0053] FIG. 2 shows a schematic view of a second embodiment of an
inductive position sensor 1 according to the invention. The second
embodiment shown in FIG. 2 differs from the first embodiment shown
in FIG. 1 in that the inductive position sensor comprises two
transmit coils 2 and in that the second sine receive coil 5 and a
second cosine receive coil 6 each have 32-periods over the
measurement area. Otherwise, the second embodiment corresponds to
the first embodiment.
[0054] The implementation of a high-resolution absolute sensor 1
with a 32-periodic receive coil pair 5, 6, an absolute 1.times.360
deg receive coil pair 3,4, two separate transmitter coils 2 and a
signal processing unit 9 with two inductive position sensor ICs
(not shown) with a 12 bit signal acquisition the theoretic
resolution is 32.times.12 bit which is 131072 counts or 17 bit.
[0055] It is known that the sensor linearity will be lower
depending on system configuration and tolerances.
[0056] The implementation of the high-resolution absolute sensor 1
with a 32-periodic receive coil pair 5, 6, a 1.times.360 absolute
receive coil pair 3,4 and one shared signal processing unit 9 is
shown in FIG. 2.
[0057] Generally the target must be designed to generate signal for
both high-resolution receive coil pair 5, 6 and absolute position
receive coil pair 3, 4. The accuracy and robustness over tolerances
will depend on the target configuration. Below are some
implementation examples. FIG. 3 shows a first embodiment of a
conductive moving target 7. The conductive moving target 7
comprises multiple sections 12 spaced apart from each other. The
multiple sections 12 of the conductive moving target 7 have the
same shape and spacing. One or more portions of the incremental
n-period sensor target 7 are removed to generate sufficient signal
on the 1-periodic absolute position receive coil pair 3, 4.
[0058] FIG. 4 shows a second embodiment of a conductive moving
target 7. FIG. 4 shows the upper and lower side of a substrate,
wherein one side comprises a first target element 10 and the other
side comprises a second target element 11, wherein the shape of the
first target element 10 is different to the shape of the at least
one second target element 11. Particularly, the first target
element 10 comprises multiple sections 12, spaced apart from each
other. The multiple sections 12 of the conductive moving target 7
have the same shape and spacing and cover the complete
circumference of the circular substrate building the conductive
moving target 7. Thus, the multiple sections 12 of the first target
element 10 cover the complete measurement area of the inductive
position sensor 1. The second target element 11 has a semi-circular
shape and overs a half-circle of the circular substrate of the
conductive moving target 7. The first element 10 and second element
11 of the conductive moving target 7 overlap with each other, as
FIG. 4 shows the two sides of the same substrate of the same
conductive moving target 7. Thus, FIG. 4 shows high-resolution
segments 12 for the n-periodic receive coil pair 5, 6 and stacked
target 11 for the 1-periodic absolute position receive coil pair 3,
4.
[0059] FIG. 5 shows a third embodiment of a conductive moving
target 7. The third embodiment of the conductive moving target 7
shown in FIG. 5 differs from the second embodiment of the
conductive moving target 7 shown in FIG. 4 in that the second
element 11 has the shape of an arc segment of a full ring, which is
arranged on the same side as the first element 10 comprising the
segments 12. Furthermore, the first element 10 and the second
element 11 of the conductive moving target 7 are arranged next to
each other, particularly the second element 11 is arranged inside
the first element 10, and the first element 10 and the second
element 11 do not overlap.
[0060] FIG. 6 shows a fourth embodiment of a conductive moving
target 7. The fourth embodiment of the conductive moving target 7
shown in FIG. 6 differs from the third embodiment of the conductive
moving target 7 shown in FIG. 5 in that the second element 11 has a
rectangular shape and overlaps with the first element 10.
Particularly, the first element 10 comprising the segments 12
completely overlaps the second element 11 if the gaps between the
segments 12 are considered to belong to the first element 10.
[0061] FIG. 7 shows a fifth embodiment of a conductive moving
target 7. The fifth embodiment of the conductive moving target 7
shown in FIG. 7 differs from the fourth embodiment of the
conductive moving target 7 shown in FIG. 6 in that the second
element 11 has the shape of an arrow.
[0062] FIG. 8 shows a sixth embodiment of a conductive moving
target 7, wherein the second element 11 has a bigger arrow shape
compared to the fifth embodiment shown in FIG. 7.
[0063] FIGS. 9a and 9b show a target configuration comparisons for:
[0064] a) Second embodiment of conductive moving target shown in
FIG. 4 [0065] b) Third embodiment of conductive moving target shown
in FIG. 5 [0066] c) Fourth embodiment of conductive moving target
shown in FIG. 6 [0067] d) Fifth embodiment of conductive moving
target shown in FIG. 7, and [0068] e) Sixth embodiment of
conductive moving target shown in FIG. 8.
[0069] The setup of the used comparison was: [0070] Speed 1000 rpm
[0071] Nominal AG 1 mm . . . 1.75 mm [0072] X/Y Displacement +/-0.3
mm [0073] Tilt +/-0 . . . 0.5 mm [0074] Different Targets were
Tested
[0075] FIGS. 9a and 9b show a performance comparison based on
32.times. coil.
[0076] There are different ways of signal processing to calculate
the absolute high resolution angle signal. One possible method is
shown below.
[0077] Step1: Calculate
Divisor=(Resolution/#HighResolutionPeriods)
[0078] Step2: Check the actual period
ActualPeriod=Quotient(AbsoluteAngle/Divisor)
[0079] Step3: Calculate the High Resolution Absolute Angle
AbsHighres=HighresAngle+ActualPeriod*Resolution
[0080] Step4: Check Plausibility and correct period if needed
[0081]
IF((AbsHighres-#HighResolutionPeriods*AngleLowRes))>Threshold->Outp-
ut=AbsHighres-Resolution [0082]
IF((AbsHighres-#HighResolutionPeriods*AngleLowRes))<-Threshold->Out-
put=AbsHighres+Resolution [0083] ELSE Output =AbsHighres
[0084] FIG. 10 shows a high-resolution output after processing,
particularly signal plot of 32 periodic high-resolution sensor and
processed high resolution absolute sensor.
[0085] By implementing two or more sets of the high-resolution
absolute sensors on one PCB it is possible to generate a redundant
solution for higher diagnostic coverage.
[0086] By implementing two sets of the high-resolution absolute
sensors on each side of a torsion bar it is possible to calculate
the torque as the difference between the two sensors.
[0087] FIG. 11 shows a schematic view of a third embodiment of an
inductive position sensor 1 according to the invention. The
inductive position sensor 1 shown in FIG. 11 is a linear position
sensor with a straight measurement area, along which the conductive
target 7 moves. Otherwise, the third embodiment of the inductive
position sensor 1 shown in FIG. 11 corresponds to the first
embodiment of the inductive position sensor 1 shown in FIG. 1.
* * * * *