U.S. patent application number 14/829990 was filed with the patent office on 2017-01-05 for method for operating a sensor system, sensor system and measurement signal.
The applicant listed for this patent is BALLUFF GmbH. Invention is credited to Ralph Bauer, Thomas Burkhardt.
Application Number | 20170003143 14/829990 |
Document ID | / |
Family ID | 50236179 |
Filed Date | 2017-01-05 |
United States Patent
Application |
20170003143 |
Kind Code |
A9 |
Burkhardt; Thomas ; et
al. |
January 5, 2017 |
METHOD FOR OPERATING A SENSOR SYSTEM, SENSOR SYSTEM AND MEASUREMENT
SIGNAL
Abstract
The invention proposes a method for operating a sensor system
comprising at least one sensor unit which provides signals, in
which the signals comprise primary measurement value signals which
are measurement values of the sensor unit or are generated from
measurement values of the sensor unit and in which the signals
comprise coefficient signals which characterize the measurement
value capture.
Inventors: |
Burkhardt; Thomas; (Zell
unter Aichelberg, DE) ; Bauer; Ralph; (Kirchheim am
Neckar, DE) |
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Applicant: |
Name |
City |
State |
Country |
Type |
BALLUFF GmbH |
Neuhausen |
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DE |
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Prior
Publication: |
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Document Identifier |
Publication Date |
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US 20160041004 A1 |
February 11, 2016 |
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Family ID: |
50236179 |
Appl. No.: |
14/829990 |
Filed: |
August 19, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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PCT/EP2014/054333 |
Mar 6, 2014 |
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14829990 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B60L 13/06 20130101;
B60L 2200/26 20130101; G01D 3/00 20130101; G01D 5/00 20130101; G01D
5/14 20130101; G01D 5/145 20130101; G01B 7/003 20130101 |
International
Class: |
G01D 5/14 20060101
G01D005/14 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 8, 2013 |
DE |
10 2013 102 323 |
Claims
1. Method for operating a sensor system comprising at least one
sensor unit which provides signals, in which the signals comprise
primary measurement value signals which are measurement values of
the sensor unit or are generated from measurement values of the
sensor unit and in which the signals comprise coefficient signals
which characterize the measurement value capture.
2. Method in accordance with claim 1, wherein the primary
measurement value signals are electrical signals which are
measurement values of, or are generated from, one or more physical
quantities.
3. Method in accordance with claim 1, wherein the coefficients
which are contained in the coefficient signals characterize at
least one of (i) what margin, (ii) what security and (iii) what
quality exists in the measurement value capture.
4. Method in accordance with claim 1, wherein the primary
measurement value signals and the coefficient signals are
transmitted on different channels.
5. Method in accordance with claim 1, wherein the primary
measurement value signals and the coefficient signals are
transmitted in attached relationship with each other and are in
particular transmitted on a single channel.
6. Method in accordance with claim 1, wherein the coefficient
signals are permanently transmitted and are in particular
transmitted at the same data rate as that of the primary
measurement value signals.
7. Method in accordance with claim 1, wherein the coefficient
signals are transmitted at a data rate that is less than that of
the measurement value signals and are in particular transmitted at
certain events, such as startup or shutdown of the sensor system or
service calls related to the sensor system.
8. Method in accordance with claim 1, wherein the coefficient
signals and the primary measurement value signals are transmitted
in analog form and in particular wherein the coefficient signals
are modulated onto the primary measurement value signals.
9. Method in accordance with claim 1, wherein the primary
measurement value signals and the coefficient signals are
transmitted in serial digital form.
10. Method in accordance with claim 9, wherein a primary
measurement value signal is transmitted as a digital datum
comprising a plurality of data bits, in particular wherein the
individual data bits are requested and output with respective clock
impulses.
11. Method in accordance with claim 10, wherein a number of the
data bits requested and output is defined by clock impulses of a
controller.
12. Method in accordance with claim 9, wherein a coefficient signal
is attached to the datum of the associated primary measurement
value signal as a digital datum comprising data bits and is in
particular attached to said datum in such a manner that it follows
the latter in time.
13. Method in accordance with claim 12, wherein a number of
associated clock periods of the primary measurement value signal
with n data bits with attached coefficient signal with m data bits
is n+m.
14. Method in accordance with claim 10, wherein at least one of the
datum of the measurement value signal and the datum of the
coefficient signal comprises one or more extra bits and comprises
in particular at least one of (i) one or more error bits, (ii) one
or more warning bits and (iii) one or more check bits.
15. Method in accordance with claim 14, wherein a measurement value
signal datum is provided with CRC bits and CRC bits are attached to
the coefficient signal datum as well.
16. Method in accordance with claim 15, wherein a number of the
clock periods for measurement value signals with n data bits with
attached coefficient signal with m data bits and with q data bits
for a CRC datum is n+m+2q.
17. Method in accordance with claim 9, wherein the primary
measurement value signals and the coefficient signals are
transmitted according to SSI interface or BiSS-C interface.
18. Method in accordance with claim 1, wherein primary measurement
value signals are transmitted as analog or digital increments.
19. Method in accordance with claim 18, wherein coefficient signals
are transmitted as increments with a time distance apart that is
less than the time distance between increments of the primary
measurement value signals.
20. Method in accordance with claim 1, wherein transmission of the
coefficient signals is such that a superordinate controller can
decide whether or not it evaluates the coefficient signals.
21. Method in accordance with claim 1, wherein a signal chain
comprising primary measurement value signals and coefficient
signals is formed such that there is provided a capability of
selecting whether or not coefficients are read out.
22. Method in accordance with claim 1, wherein coefficient signals
are determined at the sensor system without the use of additional
monitoring sensors and in particular wherein one or more sensors of
the at least one sensor unit are used for the determination of
coefficients.
23. Method in accordance with claim 1, wherein in a sensor system
in which the time period between certain two zero-crossings is
measured as a primary measurement value signal, a maximum signal
level between the zero-crossings results in the coefficient.
24. Method in accordance with claim 1, wherein measurement values
are captured from a plurality of signals of the at least one sensor
unit.
25. Method in accordance with claim 24, wherein a check is
performed as to whether on a certain zero-crossing of an analog
first sensor signal, a digital second signal is in high state and
wherein, in this case, a measurement signal is generated, in
particular as a falling edge of a digital signal.
26. Method in accordance with claim 25, wherein a coefficient
signal is generated from the length of the second sensor signal at
HIGH and the position thereof relative to the zero-crossing.
27. Method in accordance with claim 1, wherein in a
magnetostrictive displacement measuring system, a position value is
derived from a voltage signal and an amplitude of the voltage
signal forms a coefficient signal, in particular wherein the
amplitude is determined via the adjustment of an automatic gain
control circuitry.
28. Method in accordance with claim 1, wherein in a magnetically
encoded displacement measuring system, a coefficient signal is
determined from at least one of (i) an amplitude or amplitude ratio
of magnetic sensor signals and (ii) a phase or phase ratio of
magnetic sensor signals.
29. Method in accordance with claim 1, wherein in a sensor system
comprising a plurality of sensor units, the measurement value of
the sensor unit that has the highest coefficient is used.
30. Sensor system, comprising at least one sensor unit which
provides measurement values for primary measurement value signals
and comprising a coefficient determining unit which generates
coefficient signals that characterize the measurement value
capture.
31. Sensor system in accordance with claim 30, wherein a signal
generating unit is provided which connects coefficient signals to
primary measurement value signals.
32. Sensor system in accordance with claim 30, wherein the
coefficient determining unit generates the coefficient signals
without the use of additional monitoring sensors.
33. Measurement signal of a sensor system, comprising a primary
measurement value signal and a coefficient signal which
characterizes the measurement value capture.
34. Measurement signal in accordance with claim 33, wherein the
primary measurement value signal is a digital serial signal and the
coefficient signal is attached as a digital datum to the primary
measurement value signal.
Description
[0001] This application is a continuation of international
application number PCT/EP2014/054333 filed on Mar. 6, 2014 and
claims the benefit of German application No. 10 2013 102 323.1
filed on Mar. 8, 2013, which are incorporated herein by reference
in their entirety and for all purposes.
BACKGROUND OF THE INVENTION
[0002] The invention relates to a method for operating a sensor
system comprising at least one sensor unit.
[0003] The invention further relates to a sensor system.
[0004] Furthermore, the invention relates to a measurement signal
of a sensor system.
[0005] Sensor systems, such as inductive distance sensors,
magnetostrictive displacement sensors and displacement sensors with
magnetically encoded scale body, are described in the book "Lineare
Weg- and Abstandssensoren" (Linear Displacement and Distance
Sensors) by T. Burkhardt, A. Feinaugle, S. Fericean and A. Forkl,
Verlag Moderne Industrie, Munich 2004.
[0006] DE 101 64 121 A1 discloses a magnetostrictive displacement
measurement method for determining a position of a magnet, in which
the magnet is movable along a waveguide, in which an excitation
impulse is generated and is conducted through the waveguide to the
magnet, in which a torsion wave is generated in the waveguide when
the excitation impulse reaches the magnet, in which a reply impulse
is generated depending on the torsion wave, and in which the
position of the magnet is determined depending on the excitation
impulse and the reply impulse. A multiplicity of positions and of
excitation impulse correction values are associated with each
other, and the duration of the next excitation impulse is changed
depending on the position of the magnet determined and the
associated excitation impulse correction value from the table.
[0007] DE 10 2004 025 388 A1 discloses a method for determining the
position and/or one or more movement quantities of an object, in
which position data and/or first movement data for a first movement
quantity of the object are determined by time-discrete measurements
and in which second movement data for a second movement quantity of
the object are determined by time-continuous measurements, wherein
the second movement quantity is in a differential relation with
respect to the position and/or the first movement quantity.
[0008] DE 31 31 455 A1 discloses a magnetostrictive displacement
measuring device comprising an impulse generator for generating
electric impulses. There is provided a source for generating sound
impulses which serve as reference impulses, said source being
stationary with respect to a sound transducer and cooperating with
a magnetostrictive element.
[0009] DE 10 2006 051 032 A1 discloses a system for determining the
anchoring state of implanted endoprostheses, wherein the
endoprosthesis has arranged thereon a sensor suited to vibration
measurement and a transponder unit for wireless transmission of
vibration measurement signals and for inductive transmission of
electrical energy.
[0010] A magnetostrictive sensor and a control apparatus for
controlling a variable of a device are disclosed in U.S. Pat. No.
6,600,962 Bl.
[0011] DE 101 13 716 C2 discloses a communication interface for a
distance measuring device, said communication interface being
capable of being coupled between the distance measuring device and
a control device. U.S. Pat. No. 6,867,581 B1 discloses a sensor
device comprising a sensor element for generating an output signal
in response to the measurement of a physical quantity.
[0012] DE 20 2008 014 347 U1 discloses a displacement measuring
apparatus, comprising a measuring probe, a housing, a first board,
a second board and a third board, said boards being arranged in the
housing and being circuit carriers, wherein the second board and
the third board are in each case oriented transversely to the first
board, wherein the second board and the third board are connected
together by means of a first connector device and wherein the
combination of second board and third board is connected to the
first board by way of a second connector device.
[0013] DE 10 2008 009 250 B4 discloses a distance sensor apparatus
in which distance determination relies on a propagation time
measurement of signals, said apparatus comprising a transmitter
device, a receiver device providing receive signals, an amplifier
device for receive signals, a control device operatively connected
for signal communication with the amplifier device and controlling
the latter by control signals in order to control the amplitude of
amplified receive signals. A control signal evaluation device is
provided which is operatively coupled for signal communication with
the control device and which is provided with control signals for
evaluation. The control circuit comprises a terminal via which
control signals can be coupled out and can be provided to the
control signal evaluation device.
[0014] DE 10 2004 025 387 A1 discloses a magnetostrictive
displacement transducer for detecting the displacement of a
position marker, said magnetostrictive displacement transducer
comprising a measuring probe device having a measuring probe
extending in a longitudinal direction, the position marker coupling
to the measuring probe in a non-contact manner. An integrated
acceleration sensor is provided for determining the acceleration of
the position marker.
[0015] DE 10 2010 039 055 A1 discloses a displacement measuring
apparatus, comprising at least a first measuring path and a second
measuring path, each of these having an extension in a longitudinal
direction and being oriented parallel to one another in at least a
measuring range. Furthermore, at least one position marker is
provided which couples to the measuring paths in a non-contact
manner and a measuring path holder is provided which extends in the
measuring range and has recesses, each recess having a measuring
path arranged therein.
[0016] EP 1 164 358 A1 discloses an inductive measuring device for
position detection, consisting of a coil structure and a scale body
with at least one scale of variable reluctance or conductivity. The
coil structure is of multilayer design comprising a combination of
coils having contours in the form of quasi-closed windings.
[0017] A method for serial data transmission between a position
measuring system and a processing unit is known from EP 1 168 120
A2.
[0018] A description of essential aspects of the PROFIBUS
technology is provided in "PROFIBUS Technology and Application"
System Description, August 2002-version.
[0019] A description of a format and a modulation method for a
digital code recorded on a longitudinal track is provided in the
document entitled "EBU Time-And-Control Code for TELEVISION TAPE
RECORDINGS", Tech 3097-E, 3rd edition, April 1982, said digital
code being used for purposes of timing and control on television
tape machines and associated audio tape machines.
[0020] A description of the Open Source BiSS Interface is provided
in the article entitled "BiSS-Interface als adaptierter Interbus"
SPS-Magazin, HMI-Special issue, 2011, pp. 113-115.
[0021] A description of the SMPTE time code is provided in the
document entitled "SMPTE Made Simple", TimeLine Vista, Inc.,
1996.
SUMMARY OF THE INVENTION
[0022] In accordance with an embodiment of the invention, there is
provided a method for operating a sensor system comprising at least
one sensor unit which provides signals, said method having a high
utilization factor for a user.
[0023] In accordance with an embodiment of the invention, the
signals comprise primary measurement value signals which are
measurement values of the sensor unit and are generated from
measurement values of the sensor unit, and coefficient signals
which characterize the measurement value capture.
[0024] The primary measurement value signals characterize the
physical quantities that are measured via the at least one sensor
unit. The coefficient signals characterize how "critical" the
determination of these measurement quantities was in terms of, for
example, how much "margin" or "security" existed in the measurement
thereof.
[0025] The coefficient signals provide qualitative and quantitative
information on the reliability of the measurement values.
Optionally, the sensor system may be adjusted by, for example, a
feedback loop in order to achieve a higher quality.
[0026] In particular, the primary measurement value signals are
electrical signals which are measurement values of, or are
generated from, one or more physical quantities.
[0027] The coefficients which are contained in the coefficient
signals characterize in particular what margin and/or security
and/or quality exist(s) in the capture of the measurement values,
or how critical the determination thereof is. For example,
measurement values may be captured at different signal-to-noise
ratios. The signal-to-noise ratio can be characterized via the
coefficients. If, for example, this ratio is very small, the
captured measurement values are correspondingly more
"critical".
[0028] For example, by determining the coefficient and in
particular by determining the coefficient on a regular basis, it is
also possible, when changes occur in the sensor system or in the
environment of the sensor system which change relevant properties,
for such changes to be recognized at an early stage, and
corresponding actions can then be initiated.
[0029] By way of example, it is also possible that for "bad"
coefficients an indication be given indicating, for example, the
need for a sensor system to be readjusted.
[0030] The primary measurement value signals and the coefficient
signals can be transmitted on different channels.
[0031] Alternatively, it is also possible for the measurement value
signals and the coefficient signals to be transmitted in attached
relationship with each other and in particular to be transmitted on
a single channel. By way of example, coefficient signals can be
modulated onto the primary measurement value signals or they can be
serially attached thereto.
[0032] In particular, the primary measurement value signals and the
coefficient signals are combined in the output signals in such a
manner that downward compatibility with the method of "pure"
transmission of measurement values (i.e. without coefficients)
exists so that, for example, an adjustment can be made in a
superordinate control or controller as to whether or not the
coefficient signals are utilized.
[0033] It is possible for the coefficient signals to be permanently
transmitted and in particular to be transmitted at the same data
rates as that of the primary measurement value signals. For
example, monitoring on a regular basis can thereby be realized.
[0034] It is also possible for the coefficient signals to be
transmitted at a data rate that is less than that of the
measurement value signals and, in particular, for them to be
transmitted at certain events, such as startup or shutdown of the
sensor system or service calls related to the sensor system. A
corresponding checking action can thereby be realized.
[0035] In an exemplary embodiment, the coefficient signals and the
primary measurement value signals are transmitted in analog form
and, in particular, the coefficient signals are modulated onto the
primary measurement value signals.
[0036] It is also possible for the primary measurement value
signals and the coefficient signals to be transmitted in serial
digital form. For example, downward compatibility can thereby be
achieved in a simple way. In particular, the coefficient signals
are attached to the primary measurement value signals in time
sequence.
[0037] In an exemplary embodiment, a primary measurement value
signal is transmitted as a digital datum comprising a plurality of
data bits, in particular wherein the individual data bits are
requested and output with respective clock impulses. A coefficient
signal can thereby be attached as a digital datum in a simple
way.
[0038] In particular, provision is made for a number of the data
bits requested and output to be defined by clock impulses of a
controller. Downward compatibility can thereby be realized in a
simple way, i.e. a controller is able to decide by, for example,
the number of clock impulses whether it wants to receive or
evaluate the additional information that is contained in the
coefficient signals. Signal chains comprising coefficient signals
can then be generated, and a selection can be made via the
controller as to whether or not the coefficient signals are
evaluated.
[0039] In particular, then, a coefficient signal is attached to the
datum of the associated primary measurement value signal as a
digital datum comprising data bits and is in particular attached to
said datum in such a manner that it follows the latter in time.
This results in a total signal that comprises as its components the
datum of the primary measurement value signal and the datum of the
coefficient signal. For example, a superordinate controller can
then decide via a corresponding clocking action whether the
coefficient signals are evaluated as well or whether they are
ignored.
[0040] A number of associated clock periods of the primary
measurement value signal with n data bits with attached coefficient
signal with m data bits is n+m. A superordinate controller can then
decide by a corresponding clocking action with n clock periods
whether the primary measurement value signal alone is used, or, by
selecting n+m periods, whether the coefficient signal is utilized
as well. Furthermore, by way of a corresponding clocking action in
a superordinate controller, it is easily possible for the primary
measurement value signal to be separated from the coefficient
signal.
[0041] Provision may be made for the datum of the measurement value
signal and/or the datum of the coefficient signal to contain one or
more extra bits in addition to the actual measurement value
information and coefficient information and in particular to
comprise one or more error bits and/or warning bits and/or check
bits or also start bits.
[0042] A measurement value signal datum can be provided with CRC
bits and CRC bits are then attached to the coefficient signal datum
as well. CRC bits provide a check value in order to be able to
detect errors in transmission or storage. Downward compatibility
results when corresponding CRC bits are attached to a datum which
consists of the original datum, the CRC for the latter, and the
coefficient signal datum. The total signal therefore ends with CRC
bits. This "end" CRC is determined using the same algorithm as that
used for determining the CRC for the original datum.
[0043] In particular, a number of the clock periods for measurement
value signals with n data bits with attached coefficient signal
with m data bits and with q data bits for a CRC datum is then
n+m+2q. Because the CRC datum is contained twice in the total
signal, it accordingly requires 2 q clock periods.
[0044] In particular, the CRC datum of a signal chain comprising a
measurement value signal and a coefficient signal is protected by
the CRC datum that is attached to the coefficient signal. This
results in a high level of security and compatibility because, as
with the transmission without coefficient datum, the CRC bits are
attached to the end of the total signal.
[0045] For example, the primary measurement value signals and the
coefficient signals are transmitted according to SSI interface (SSI
protocol) or BiSS-C interface (BiSS-C protocol). The transmission
of coefficient signals can be integrated in these protocols in a
corresponding manner.
[0046] It is also possible for primary measurement value signals to
be transmitted as analog or digital increments. Such a transmission
of increments is provided for example in displacement measuring
systems using a magnetically encoded scale body. Coefficient
signals can thereby be transmitted by corresponding (additional)
increments.
[0047] For example, coefficient signals are transmitted as
increments with a time distance apart that is less than the time
distance between increments of the primary measurement value
signals. By arrangement and/or frequency of increments which form
the coefficient signal, the corresponding coefficient signal can be
transmitted. For a superordinate (evaluating) controller, a
coefficient signal when not evaluated specifically means, at most,
increased noise.
[0048] In particular, transmission of the coefficient signals is
such that a superordinate controller can decide whether or not it
evaluates the coefficient signals. This results in downward
compatibility. For example, a decision as to whether or not
coefficient signals are evaluated can be made via the number of
clock periods used.
[0049] It is particularly advantageous for a signal chain
comprising primary measurement value signals and coefficient
signals to be formed such that there is provided a capability of
selecting whether or not coefficients are read out. This results in
downward compatibility. In a serial digital transmission for
example, a decision as to whether it is desired to read out
coefficients is made by sending more clock impulses.
[0050] In a BiSS-C transmission for example, if no more clock
impulses are sent after a first CRC, the system will behave like a
standard BiSS-C interface. Downward compatibility is thereby
realized in a simple way; if further clock impulses are sent, one
obtains the coefficient and the CRC across the entire data set. For
example, incremental interfaces have additional impulses inserted
therein which, by a standard controller, are interpreted merely as
noise. These additional impulses can be evaluated and interpreted
and coefficients can be captured therefrom. For example, in an
analog data transmission, the coefficient is superimposed on the
useful signal. A standard controller can ignore the coefficient
signals. An adapted controller can look out for the superimposed
coefficient signals and can evaluate and interpret these in a
corresponding manner.
[0051] It is particularly advantageous for coefficient signals to
be determined at the sensor system without the use of additional
monitoring sensors and, in particular, for one or more sensors of
the at least one sensor unit to be used for the determination of
coefficients. Coefficient determination can thereby be realized in
a simple way.
[0052] In an exemplary embodiment of a sensor system, the time
period between certain two zero-crossings of an analog signal is
measured as a primary measurement value signal. A maximum signal
level between the zero-crossings then advantageously results in the
coefficient directly or indirectly.
[0053] Such a determination is for example provided in
magnetostrictive displacement measurements. For example, when the
maximum signal level is very low, then a bad signal-to-noise ratio
exists and the determination of the time period is "critical",
i.e., in particular, there is not a high level of measurement
accuracy.
[0054] Provision may also be made for measurement values to be
captured from a plurality of signals of the at least one sensor
unit. For example, by combining corresponding signals, coefficients
can then be determined as well.
[0055] For example, a check is performed as to whether on a certain
zero-crossing of an analog first sensor signal, a digital second
signal is in high state, and if this the case a measurement signal
is generated, in particular as a falling edge of a digital signal.
Such a capture of a primary measurement value signal is used for
example in connection with sensor systems that employ magnetically
encoded scale bodies.
[0056] For example, a coefficient signal is then generated from the
length of the second sensor signal at HIGH and the latter's
position relative to the zero-crossing. In a sense, the phase
between the digital second sensor signal and the analog first
sensor signal is checked.
[0057] In a magnetostrictive displacement measuring system for
example, a position value is derived from a voltage signal and an
amplitude of the voltage signal forms a coefficient signal, in
particular wherein the amplitude is determined via the adjustment
of an automatic gain control circuitry. For example, a coefficient
signal can then be directly generated from this adjustment.
[0058] In a magnetically encoded displacement measuring system for
example, a coefficient signal is determined from an amplitude or
amplitude ratio and/or a phase or phase ratio of magnetic sensor
signals.
[0059] It is particularly advantageous if, in a sensor system
comprising a plurality of sensor units, the measurement value of
the sensor unit that has the highest coefficient is used. For
example, it is then possible, in a redundant sensor system, to
determine which measurement value has the highest "security", and
this measurement value can then be used.
[0060] In accordance with an embodiment of the invention, a sensor
system is provided, said sensor system comprising at least one
sensor unit which provides measurement values for primary
measurement value signals and comprising a coefficient determining
unit which generates coefficient signals that characterize the
measurement value capture.
[0061] The sensor system constructed in accordance with the
invention has the advantages that have already been discussed in
connection with the method in accordance with the invention.
[0062] In particular, the method in accordance with the invention
can be carried out on a sensor system constructed in accordance
with the invention.
[0063] Further advantageous embodiments of the sensor system
constructed in accordance with the invention have likewise already
been discussed in connection with the method in accordance with the
invention.
[0064] In particular, a signal generating unit is provided which
connects coefficient signals to primary measurement value signals.
It is thereby possible for coefficient signals to be transmitted in
associated relationship with the measurement value signals.
[0065] In particular, the coefficient determining unit generates
the coefficient signals without the use of additional monitoring
sensors.
[0066] In accordance with an embodiment of the invention, there is
further provided a measurement signal comprising a primary
measurement value signal and a coefficient signal which
characterizes the measurement value capture.
[0067] For example, the coefficient signal is attached to the
primary measurement value signal in time sequence, in particular
wherein the primary measurement value signal is transmitted in
serial form, and a serial total signal is formed. In the case of
analog signals it is also possible, for example, to modulate the
coefficient signal onto the primary measurement value signal.
[0068] The measurement signal in accordance with the invention has
the advantages that have already been explained in connection with
the method in accordance with the invention and the sensor system
in accordance with the invention.
[0069] In particular, the primary measurement value signal is a
digital serial signal and the coefficient signal is attached (in
serial form) as a digital datum to the primary measurement value
signal.
[0070] The following description of preferred embodiments serves in
conjunction with the drawings to explain the invention in greater
detail.
BRIEF DESCRIPTION OF THE DRAWINGS
[0071] FIG. 1 is a schematic representation of a sensor system that
provides coefficient signals, comprising a control device of a
superordinate control;
[0072] FIG. 2 is an exemplary embodiment of a serial signal
comprising a measurement value signal and a coefficient signal
attached thereto;
[0073] FIG. 3 is an exemplary embodiment of a CRC-protected signal
with an attached coefficient signal;
[0074] FIG. 4 is an example of an incremental measurement value
signal (FIGS. 4(a) and (b)) with coefficient signals;
[0075] FIGS. 5(a), (b) are examples of a measurement quantity for
different conditions of Umax (FIGS. 5(a) and (b));
[0076] FIGS. 6(a), (b) show measurement quantities from which are
derived measurement value signals (FIG. 6(c)) and different
"critical signals" (FIGS. 6(d), (e), (f)) which are used for
coefficient determination.
DETAILED DESCRIPTION OF THE INVENTION
[0077] An exemplary embodiment of a sensor system, shown
schematically in FIG. 1 and indicated therein by 10, comprises a
sensor device 12. Said sensor device 12 provides sensor signals at
an output 14 thereof. The sensor device 12 comprises a sensor unit
16. In particular, said sensor unit 16 is arranged within a housing
18. The housing 18 is preferably closed.
[0078] The sensor unit 16, which comprises one or more sensitive
elements, measures physical quantities. These form the actual
measurement values. The measurement values are converted to
electrical quantities by a transducer unit 20 if they are not
electrical quantities already.
[0079] The sensor device 12 further comprises a coefficient
determining unit 22. The coefficient determining unit 22 determines
a coefficient which is associated with one or more measurement
values and characterizes the security and/or quality of the
measurement value capture itself. In particular, a coefficient
characterizes a margin or security that exists in the measurement
value capture.
[0080] In particular, the coefficient determining unit 22 is
configured such that an additional monitoring sensor is not
required for coefficient determination.
[0081] For example, the coefficient determining unit 22 itself
captures measurement signals of the sensor unit 16 and/or captures
data that are provided by the transducer unit 20.
[0082] Measurement value signals and coefficient signals are
combined.
[0083] The sensor device 12 comprises for example an amplifier 24
which amplifies the measurement value signals, thereby providing
primary measurement value signals which are usable signals. In an
exemplary embodiment, the combination of primary measurement value
signals and coefficient signals is amplified.
[0084] It is also possible in principle for coefficient signals and
primary measurement value signals to be amplified separately.
[0085] The sensor device 12 has an interface 26. This interface 26
is connected to the output 14. Primary measurement value signals
and associated coefficient signals are provided at the output 14 in
a single-channel manner or in a multichannel manner.
[0086] In an exemplary embodiment, the sensor system 10 comprises a
superordinate control device 28. The control device captures the
signals of the sensor device 12 which are composed of the primary
measurement value signals and the coefficient signals and are
provided at the output 14. To this end, the control device 28 has
an adapted interface 30. Downstream of this interface 30 is an
evaluation unit 32. In particular, the evaluation unit 32 separates
the primary measurement value signals from the coefficient signals.
For this purpose, there are provided for example a first terminal
34 and a second terminal 36. Primary measurement value signals are
provided, or utilized, at the first terminal 34 via a corresponding
interface and coefficient signals are provided at the second
terminal 36 via a corresponding interface.
[0087] It is alternatively possible for the separation between
measurement value and coefficient to be realized not in a separate
control device but within the control entity.
[0088] It is in principle possible for a feedback to exist between
the control device 28 and the sensor device 12. This feedback is
indicated in FIG. 1 by the line designated by reference character
38. The line 38, which is connected to the second terminal 36,
feeds back coefficient signals to the sensor device 12, in
particular over the interface 26. A corresponding adaptation
depending on the coefficient signals can be carried out in the
sensor device 12, for example by correspondingly adjusting the
sensor unit 16 and/or the transducer unit 20 and/or the amplifier
24. By way of example, it is thereby possible to realize some type
of control loop in order to achieve a high-quality measurement
result. The objective of this feedback may be, for example, to
achieve a high coefficient in the measurement value capture.
[0089] It is also possible for coefficient signals to be used for
adaptation in the sensor device 12 directly (without external
outcoupling).
[0090] In an exemplary embodiment (FIG. 2), the sensor device 12
provides a signal in which a coefficient signal 40 is attached to a
primary measurement value signal. Said signal is transmitted as a
digital serial transmission, which is single-channel.
[0091] The primary measurement value signal 42 is a digital datum
composed of a plurality of data bits. The data bits comprise
measurement value data bits 44 from MSB (most significant bit) to
LSB (least significant bit). Furthermore, extra bits are provided,
such as one or more error bits 46 and one or more warning bits 48.
The datum of the primary measurement value signal 42 is transmitted
between time t1 and time t2 and comprises n data bits, inclusive of
any extra bits such as error bits 46 and warning bits 48.
[0092] Each individual data bit is output on a respective clock
impulse 50 and is output, for example, with a rising edge of such
clock impulse. There are therefore provided n clock periods for n
data bits of the datum of the primary measurement value signal
42.
[0093] The coefficient signal 40 is a datum having m data bits 52
between the data bits MSB (most significant bit) and LSB (least
significant bit). These data bits 52 of the coefficient signal 40
are transmitted between times t2 to t3. The datum of the
coefficient signal 40 follows the datum of the primary measuring
signal 42 immediately.
[0094] The data bits 52 of the coefficient signal 40 are output on
corresponding clock impulses 50. There are therefore provided m
additional clock impulses for transmitting the coefficient signal
40; the total signal, which is composed of the primary measurement
value signal 42 and the attached coefficient signal 40, comprises
n+m data bits. N+m clock periods 50 are needed for it.
[0095] The total signal is transmitted between times t1 and t3.
Time t3 is followed by a pause of duration tm.
[0096] In the example illustrated, transmission is in accordance
with SSI protocol in particular.
[0097] The data transmission of the signal comprising the primary
measurement value signal 42 and the attached coefficient signal 40
has "downward compatibility". The superordinate control device 28
can decide whether or not it evaluates the coefficient signals 40;
if, upon reception, only n clock impulses 50, counting from start,
are evaluated, then it is the primary measurement value signal 42
alone, without attached coefficient signal 40, which is being
evaluated. If n+m clock impulses are used in the reception, then
the coefficient signal 40 can be evaluated as well.
[0098] In a second exemplary embodiment (FIG. 3), the signals are
likewise transmitted in serial digital form, but this signal
transmission is via BiSS-C protocol. The primary measurement value
is transmitted as a digital datum 54 from time t2 on. This digital
datum 54 comprises, after the actual measurement value data bits
from MSB to LSB, at its end, an error bit 56 and a warning bit 58.
This digital datum comprises n data bits. Transmission at time
instant t2 starts after a start bit 60 and a CDS (Control Data
Slave) 62.
[0099] The datum 54, which is or contains the primary measurement
value signal, is followed by a CRC datum 64 having q bits. The CRC
(Cyclic Redundancy Check) contains a check value for the data;
these are the data of the primary measurement value signal.
[0100] The CRC 64 is transmitted between time instants t3 and t4.
With time instant t4, the transmission could be completed; it is
then a "normal" BiSS-C transmission. From time instant t4, if
further clock impulses are transmitted, a datum 66 for the
coefficient signal is attached to the datum 54 having the CRC 64.
Said datum 66 comprises m bits and is transmitted between time
instants t4 and t5. The datum 66 in turn has a CRC 68 attached
thereto directly, this being transmitted between time instants t5
and t6. The CRC 68 corresponds to the CRC 64, but now covering all
the bits between time instants t2 and t5. Contained in this space
of time are data bits, error bits, warning bits, the original CRC
(over t2 to t3) and coefficient bits. The total signal therefore
ends with the CRC 68.
[0101] A superordinate control, comprising for example a control
device 28, can then read out the total signal's CRC at the end of
the total signal in the same way as in the case of no coefficient
signals being attached. This results in downward compatibility.
[0102] The total signal is transmitted in n+m+2q clock periods when
the start bit 60 and the CDS 62 are not taken into
consideration.
[0103] In a further exemplary embodiment (FIG. 4), signals are
transmitted in digital incremental form. This is explained with
respect to an example in which a signal marker moves in a positive
direction at a constant velocity. The sensor unit provides signals
A (FIG. 4(a)) and B (FIG. 4(b)). The "main signals" are impulses 70
and 72, respectively. Position signals from a position marker are
transmitted as positive or negative increments. For example, in an
instance in which edges of a signal 70 occur before edges of a
signal 72, this will be counted as a positive increment. The
reverse instance will be counted as a negative increment. This
results in a basic stepped course (for movement in positive
direction at constant velocity) as depicted in FIG. 4(c).
[0104] Coefficient signals 74 can now be superimposed as increments
as well, wherein a length (in time) of an increment 74 of a
coefficient signal is less than a length in time of a main signal
70 or 72.
[0105] The sequence of edges 74 then results in the total
coefficient signal.
[0106] In FIG. 4, the signal 70 (A signal) and the signal 72 (B
signal) each have a corresponding short increment superimposed
thereon between time instants t1 and t3. The evaluation in the case
of the A signals and B signals results in a short negative
increment followed by a positive increment. The main signals 70, 72
have a negative increment superimposed thereon. Between time
instants t3 and t4, where the signal 70 is at LOW, negative and
positive increments are superimposed two times.
[0107] By the frequency and/or the succession of positive and
negative "short" edges 74, which are evaluated as increments, the
coefficient can be encoded, i.e. a coefficient signal can be
generated.
[0108] In a position measurement, this means that the incremental
main signals 70, 72 remain unchanged. The main signals have
inserted therein short increments as short changes in position. By
way of example, the coefficient can be encoded with the frequency
or the amplitude of these short changes in position. For a standard
controller without coefficient evaluation, these short changes in
position manifest themselves like position noise.
[0109] There are other possibilities of coefficient
transmission.
[0110] For example, the primary measurement value signal and its
associated coefficient signal can be transmitted in analog form
over (at least) two channels.
[0111] Also, provision may be made for the primary measurement
value signal and the associated coefficient signal to be
transmitted in analog form on one channel. For example, the
coefficient signal is modulated on the primary measurement value
signal by, for example, amplitude modulation.
[0112] It is for example also possible for primary measurement
value signals and coefficient signals to be transmitted in
incremental analog form. For example, one exemplary embodiment
transmits position signals as four sinusoidal and cosinusoidal
voltages as differential signals.
U.sub.+sin(S)=Usi.sub.max*sin(ws)+U.sub.si0 (1)
U.sub.-sin(s)=-Usi.sub.max*sin(ws)+U.sub.si0 (2)
U.sub.+cos(s)=Uco.sub.max*COS (ws)+U.sub.co0 (3)
U.sub.-cos(s)=-Uco.sub.max*cos(ws)+U.sub.co0 (4)
[0113] Here, s is the displacement to be measured and w is
determined by
w = 2 .pi. L ( 5 ) ##EQU00001##
[0114] L is a pole length or pole pair length in, for example, a
pole sensitive sensor system.
[0115] Usi.sub.max and Uco.sub.max are voltage amplitudes. It is
advantageous for these to be as large as possible. Furthermore, the
signals contain direct voltage components U.sub.si0 and
U.sub.co0.
[0116] Generally, there are tolerances for the aforesaid quantities
that are accepted by standard controllers. By exploiting these
tolerances, the coefficient can be encoded during transmission. For
example, the dc components U.sub.si0 and U.sub.co0 can transmit a
coefficient x between for example x=0 and x=1:
U.sub.si0(x)=U.sub.si0.sub._.sub.t00+(1-x)*hub (6)
U.sub.co0(x)=U.sub.co.sub._.sub.100-(1-x)*hub (7)
where hub is half the maximum offset difference that a
superordinate control, such as the control device 28, still
tolerates.
[0117] For example, the greater the difference between the dc
components, the more critical the signal capture is. Referring to
the above example, when the coefficient is no greater than x=1,
then the dc component is the same for both signal pairs.
[0118] For example, in a variant form, it is also possible for the
difference between the dc components U.sub.si0 and Ucoo to be
modulated at a certain frequency that is proportional to the
coefficient.
[0119] It is also possible for the two dc components to be varied
at the same frequency but at different relative phases. For
example, if the dc components then change in-phase relative to each
other, the primary measurement value signal having the maximum
coefficient was determined. A minimum coefficient results for a
180.degree. phase difference, for example.
[0120] This method is also downward compatible with a standard
sine/cosine interface.
[0121] It is possible in principle for coefficient signals to be
permanently transmitted with primary measurement value signals. The
data rate of the coefficient signals then corresponds to that of
the primary measurement value signals.
[0122] In one embodiment, provision is made for the primary
measurement value signals to be transmitted at a data rate that is
higher than that of the coefficient signals. For example,
coefficient signals are transmitted only at certain events, such as
for example, the startup of the sensor system, the shutdown of the
sensor system, service calls related to the sensor system, etc.
[0123] The coefficients contained in the coefficient signals
characterize in particular a security or margin and therefore also
a quality of a measurement value that is contained in the
measurement value signal. They thereby characterize how "critical"
the determination of the measurement value was.
[0124] Such information may for example be utilized where a
plurality of sensor units 16 exist in order to use, for evaluation
or use, only the primary measurement value signals of the sensor
unit that has the highest coefficient. For example, in a redundant
system comprising a plurality of sensor devices or a plurality of
sensor units (in one sensor device), the "best" measurement can
thereby be used.
[0125] The coefficient associated with the primary measurement
value signal is a measure of the "quality" of the measurement. In
principle, the primary measurement value signals can be monitored,
via the coefficient, for their "usability" in terms of the
measurement values contained therein. For example, if the
coefficient falls below a threshold, a warning signal can be
emitted indicating that the measurement values fall below a lower
limit of reliability.
[0126] The coefficient signals can be captured in different ways in
different sensor systems. The way they are captured depends on the
measurement value capture.
[0127] In one exemplary embodiment (FIG. 5), a measurement value
signal is captured from an analog signal 76 which has
zero-crossings by determining a distance T (for example a distance
in time) between certain two zero-crossings 78a and 78b. The useful
signal (the analog signal 76) has a certain maximum signal level
Umax between the two zero-crossings 78a, 78b. This maximum is a
measure of the "security" of the measurement and can be used as a
coefficient. For example, the smaller Umax is, the worse the
signal-to-noise ratio and the more critical the measurement of T
(for example a measurement of time) will be. The larger Umax, the
more secure the time measurement T is. For example, when Umax
becomes smaller and disappears in the noise, time measurement is no
longer possible.
[0128] Umax can therefore be used as a coefficient directly, and
the corresponding coefficient signal can be generated therefrom by
the coefficient determining unit 22.
[0129] In another exemplary embodiment (FIG. 6), measurement value
recognition comprises a plurality of sensor signals U1(s) and U2(s)
(FIGS. 6(a) and (b)). The usable signal U1(s) is an analog signal
and the usable signal U2(s) is a digital signal.
[0130] Measurement value recognition or capture takes place, for
example, when the usable signal U1(s) has a rising zero-crossing
80, while at the same time the usable signal U2(s) is in high state
82. A resultant primary measurement value signal Um(s) is then
generated (FIG. 6(c)), said signal having a falling edge 84.
[0131] Here, in principle, the quality of the primary measurement
value signal Um(s) is defined by the locations s1 and s2 of the
signal 86, which is in high state 82.
[0132] It is desirable for sl and s2 to be as large as possible and
for their values to be as similar as possible. However, they must
not be so large that they coincide with further rising edges of
U1(s).
[0133] FIGS. 6(d), (e) and (f) show different cases for U2(s).
These signals do not correspond to the situation shown in FIGS.
6(a) and (b). The signal U2a(s) in accordance with FIG. 6(d) and
the signal U2b(s) in accordance with FIG. 6(e) show cases where the
resultant signal Um(s) is only just valid. The signal U2c(s) in
accordance with FIG. 6(f) comes "too late" and Um(s) is not output
correctly any longer.
[0134] The aforementioned signals U2(s) as well as U2a(s), U2b(s)
and U2c(s) are examples of how a coefficient can be determined.
These signals do not themselves transmit the coefficient. The
coefficient can be transmitted in serial form, in digital
incremental form, in analog incremental form, etc. depending on the
interface used.
[0135] A concrete exemplary embodiment of a sensor system is a
magnetostrictive displacement measuring system. See, for example,
T. Burkhardt, A. Feinaugle, S. Fericean, A. Forkl, "Lineare Weg-und
Abstandssensoren" ("Linear Displacement and Distance Sensors"),
Verlag Moderne Industrie, Munich 2004. Magnetostrictive distance
measuring systems operate on the principle of measuring the
propagation time of a torsional wave that is generated by making
use of an inverse magnetostrictive effect. The position marker is a
magnet. A position value for the position of the magnet is derived
from a voltage signal. The amplitude of the voltage signal changes
under the effect of different influencing quantities, such as
temperature, distance of the position marker from a waveguide,
lateral offset of the position marker with respect to the
waveguide, position, etc. Correction for such influencing
quantities is for example realized by an automatic gain control
(AGC) circuit, in particular wherein adaptive control techniques
are applied. For example, the coefficient can be generated from the
amplitude of the voltage signal. A relevant value can in turn be
determined by, for example, adjusting the gain of the automatic
gain control circuitry. In particular, the primary measurement
values are captured from the voltage signals as described above
with reference to FIG. 5, while Umax is determined via the
adjustment of the automatic gain control circuit.
[0136] In a magnetically encoded sensor system (displacement sensor
with magnetically encoded scale body), in order to capture
displacement information, a sensor head comprising magnetic field
sensors is passed over a magnetically encoded scale body in
non-contacting and spaced-apart relationship therewith. The sensor
head has contained therein (at least) two magnetic field sensors
which measure either the component of the magnetic field vector in
the direction of their sensitivity or the angle of the magnetic
vector field relative to the direction of motion. Counting magnetic
periods provides information as to the distance travelled.
[0137] Generally, the magnetic field sensors are arranged in the
sensor head at a distance of one quarter or three quarters of a
magnetic field period from each other. This results in a 90.degree.
(or)270.degree. phase difference. The corresponding magnetic field
sensors are commonly called sine sensor and cosine sensor. See also
the book cited above.
[0138] Correspondingly, an incremental displacement system
comprising a magnetically encoded scale body provides up to two
output signals which are a position (displacement increments) and a
reference signal. A coefficient can be determined for both signals
and a combination of the two values can be transmitted.
[0139] A position signal is derived for example by interpolating
the sensor signals from the sine sensor and the cosine sensor. The
amplitude decreases under the effect of different influencing
quantities, such as distance from the magnetically encoded scale
body, lateral offset, temperature, etc. The coefficient can be
determined from the amplitude or the phase.
[0140] For a reference pulse (reference signal), same is determined
from two magnetic sensors. These magnetic sensors are separated by
a defined distance. A change in angle causes the phase between the
magnetic sensors to change. Evaluation becomes more critical. The
reference signal is also angle-dependent. Via the usable signals in
accordance with FIGS. 6(a) and (b), the corresponding reference
signal in accordance with FIG. 6(c) can be captured, with the above
mentioned possibility of coefficient capture.
[0141] In principle, with appropriate construction a magnetically
encoded displacement measuring system is also able to determine an
absolute position. In particular, a plurality of magnetic sensors
exist. For example, if the sensor head is twisted relative to the
scale body, the mechanical conditions change and the absolute
position determination becomes more critical. Temperature,
distance, lateral offset, etc. have an influence as well. Here
again, the coefficient can be derived from the corresponding
signals of the magnetic field sensors and reference is made to what
has been said in connection with FIG. 6.
[0142] In an exemplary embodiment, magnetic fields of a scale body
are measured with the aid of a plurality of sensors (for example
2*15 sensors). When a sensor unit having these sensors is moved,
the magnetic fields that can be seen by the sensors change. When a
magnetic field change occurs, the corresponding sensor that sees
this change in magnetic field must switch. The switching of the
sensors should occur as simultaneously as possible and also, where
possible, at the center of a range in which the switching of a
sensor is acceptable. The simultaneity and the centrality of the
switching of the sensors in a corresponding sensor unit are a
measure of the quality of the (primary) measurement signal.
[0143] If a sensor head having such a sensor unit has too large a
distance relative to the scale body or is in an incorrect position
or orientation relative to the scale body, the centrality or
simultaneity decreases and signal generation becomes more
critical.
[0144] The coefficient for centrality and simultaneity can be
determined by the method described above.
[0145] In accordance with the invention, a measurement signal is
provided which contains a primary measurement value signal that
contains the measurement values. The measurement signal further
comprises a coefficient signal which characterizes the capture of
the measurement values and in particular the security or margin
thereof.
[0146] In an exemplary embodiment, coefficient signals are attached
to or are superimposed on the primary measurement value signals.
This results in a corresponding signal train.
[0147] With appropriate configuration of this signal, a decision
can be made by a superordinate controller as to whether or not the
coefficient signal is utilized.
[0148] The coefficient signal can be evaluated by a corresponding
diagnostic tool in the control device 28. Optionally, it is
possible for the sensor device 12 to be adjusted when, for example,
the coefficient is or becomes too low.
[0149] For example, it is also possible for the coefficient to
change in certain positions or measurement ranges. Such a change
may occur in operation (for example following a crash or after
servicing) when relevant properties such as an air gap change. By
determining the coefficient on a regular basis, such effects can be
diagnosed at an early stage and corresponding actions can be
initiated.
[0150] In principle, coefficients can be advantageously captured
and transmitted in sensor systems that are employed for
displacement and distance measurements. However, coefficient
capture and transmission is in principle possible in any sensor
system.
LIST OF REFERENCE NUMBERS
[0151] 10 sensor system
[0152] 12 sensor device
[0153] 14 output
[0154] 16 sensor unit
[0155] 18 housing
[0156] 20 transducer unit
[0157] 22 coefficient determining unit
[0158] 24 amplifier
[0159] 26 interface
[0160] 28 control device
[0161] 30 interface
[0162] 32 evaluation unit
[0163] 34 first terminal
[0164] 36 second terminal
[0165] 38 line
[0166] 40 coefficient signal
[0167] 42 measurement value signal
[0168] 44 measurement value data bit
[0169] 46 error bit
[0170] 48 warning bit
[0171] 50 clock impulse
[0172] 52 data bit
[0173] 54 datum
[0174] 56 error bit
[0175] 58 warning bit
[0176] 60 start bit
[0177] 62 CDS
[0178] 64 CRC across data bits
[0179] 66 datum
[0180] 68 CRC across data bits, CRC of the data bits and
coefficient
[0181] 70 signal
[0182] 72 signal
[0183] 74 increment signal
[0184] 76 analog signal
[0185] 78a zero-crossing
[0186] 78b zero-crossing
[0187] 80 zero-crossing
[0188] 82 HIGH
[0189] 84 edge
[0190] 86 signal
[0191] 88 critical signal form of U2(s) as U2a(s)
[0192] 88' critical signal form of U2(s) as U2b(s)
[0193] 88'' critical signal form of U2(s) as U2c(s)
* * * * *