U.S. patent application number 09/297970 was filed with the patent office on 2001-08-16 for method and device for measuring the angle of a first rotatable body.
Invention is credited to FUHRMANN, HORST, NOLTEMEYER, RALF.
Application Number | 20010013774 09/297970 |
Document ID | / |
Family ID | 7841929 |
Filed Date | 2001-08-16 |
United States Patent
Application |
20010013774 |
Kind Code |
A1 |
NOLTEMEYER, RALF ; et
al. |
August 16, 2001 |
METHOD AND DEVICE FOR MEASURING THE ANGLE OF A FIRST ROTATABLE
BODY
Abstract
An apparatus (1) is described for determining the angle of a
first rotatable body which coacts with two further rotatable
bodies. The angle of the two further bodies can be measured, and
the angle of the first body can be calculated therefrom. According
to the present invention, means are provided with which
simultaneous measurement of the angles of the two further bodies
can be achieved. The accuracy of the determination of the angle of
the first body is thereby improved.
Inventors: |
NOLTEMEYER, RALF; (WERNAU,
DE) ; FUHRMANN, HORST; (GROSSBOTTWAR, DE) |
Correspondence
Address: |
KENYON & KENYON
ONE BROADWAY
NEW YORK
NY
10004
US
|
Family ID: |
7841929 |
Appl. No.: |
09/297970 |
Filed: |
June 29, 1999 |
PCT Filed: |
March 6, 1998 |
PCT NO: |
PCT/DE98/00661 |
Current U.S.
Class: |
324/207.25 ;
324/173 |
Current CPC
Class: |
B62D 15/02 20130101;
G01D 5/145 20130101; G01D 2205/26 20210501; G01D 2205/28
20210501 |
Class at
Publication: |
324/207.25 ;
324/173 |
International
Class: |
G01N 019/00; G01P
003/54 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 11, 1997 |
DE |
197 39 823.5 |
Claims
1. A method for determining the angle of a first rotatable body
which coacts with two further rotatable bodies, the angle of the
two further bodies being measured and the angle of the first body
being calculated therefrom, characterized in that the angle of the
two further bodies is measured simultaneously.
2. The method as defined in claim 1, characterized in that the
measured angles of the two further bodies are stored.
3. The method as defined in claim 1 or 2, characterized in that the
angles of the two further bodies are measured with a common time
reference, in particular at a single sampling time.
4. An apparatus (1, 7) for determining the angle of a first
rotatable body which coacts with two further rotatable bodies, the
angle of the two further bodies being measurable and the angle of
the first body being calculable therefrom, characterized in that
means are provided for simultaneous measurement of the angles of
the two further bodies.
5. The apparatus (1, 7) as defined in claim 4, characterized in
that each of the two further bodies is equipped with a magnet (6),
associated with which is an AMR sensor (8, 9) that is provided for
measuring the angle of the associated further body; and that an
analysis circuit (10) is provided which is coupled to the two AMR
sensors (8, 9) and is provided for analyzing and optionally for
transforming the measured angles of the two further bodies.
6. The apparatus (1, 7) as defined in claim 5, characterized in
that the analysis circuit (10) is equipped with means, in
particular with sample-and-hold elements, for storing the measured
angles of the two further bodies.
7. The apparatus (1, 7) as defined in one of claims 4 through 6,
characterized in that a calculation device (13), in particular a
programmable microprocessor, is provided for determining the angle
of the first body.
8. The apparatus (1, 7) as defined in claim 7, characterized in
that the calculation device (13) can generate a start signal (S)
with which simultaneous measurement of the angles of the two
further bodies by the two AMR sensors (8, 9) can be triggered.
9. The apparatus as defined in claim 8, characterized in that by
way of the start signal, the angles of the two further bodies are
measured with a common time reference, in particular at a single
sampling time.
10. The apparatus (1, 7) as defined in claim 5 and claim 8,
characterized in that a line (17) is provided with which the
calculation device (13) is connected to the analysis circuit (10),
and on which the start signal (S) can be delivered to the analysis
circuit (10).
11. The apparatus (1, 7) as defined in one of claims 4 through 10,
characterized in that the first body is equipped with a number (n)
of teeth; and that the two further bodies are equipped with
different numbers (m, m+1) numbers of teeth differing
therefrom.
12. The apparatus (1, 7) as defined in one of claims 4 through 11,
characterized in that the first body is coupled to a steering wheel
of a motor vehicle.
Description
BACKGROUND INFORMATION
[0001] The present invention relates to a method and an apparatus
for measuring the angle of a first rotatable body which coacts with
two further rotatable bodies, the angle of the two further bodies
being measured and the angle of the first body being determined
therefrom.
[0002] A method and an apparatus of this kind are known from German
Unexamined Patent Application 195 06 938 A1, in which a first gear
which is equipped with a number of teeth and is rotatably through
more than 360.degree. is provided as the first rotatable body. The
two further rotatable bodies are also gears, which are in
engagement with the first gear and whose numbers of teeth is less
than the number for the first gear. In addition, the numbers of
teeth of the two further bodies differ, for example, by one
tooth.
[0003] Associated with each of the two further bodies is a sensor
with which the angle of the body can be measured absolutely, i.e.
even when the body is stationary. The angle of the first body can
be determined from the measured angles of the two further
bodies.
[0004] The accuracy of the angle determined for the first body can
be influenced by an appropriate selection of the number of teeth of
the first body and of the two further bodies. It has been found,
however, that even after optimization in this regard, the angle
determined for the first body still exhibits inaccuracies.
[0005] Proceeding therefrom, it is the object of the invention to
develop a method and an apparatus of the kind cited initially in
such a way that exact determination of the angle of the first
rotatable body is possible.
[0006] In the case of a method and an apparatus of the kind cited
initially, this object is achieved according to the present
invention in that the angle of the two further bodies is measured
simultaneously.
[0007] Simultaneous measurement ensures that even when the angles
of the two further bodies are measured during rotation of the
bodies, an exact determination of the angle of the first body is
possible. If the angles of the two further bodies were not measured
simultaneously, the result, especially in the event of rotation of
the bodies, could be that the body measured later would already
have rotated further by a slight "delta." This delta is in itself
very small, but can nevertheless means that the requisite accuracy
can no longer be obtained in the subsequent determination of the
angle of the first body. This is reliably avoided by simultaneous
measurement of the angles of the two further bodies. Measurement of
the angles of the two further bodies is thus synchronized, with the
substantial advantage that the accuracy of the determination of the
angle of the first body is thereby improved.
[0008] Because of the synchronization, the angles of the two other
bodies are measured at a single sampling time, i.e. simultaneously.
Synchronization and definition of the single sampling time, and
thus simultaneous measurement, are achieved with the aid of a
signal with which measurement of the two angles is started.
[0009] In an advantageous embodiment of the invention, the measured
angles of the two further bodies are stored. The result of this is
that determination of the angle of the first rotatable body is
independent of measurement of the angles of the two further bodies.
It is thus unnecessary to process the measured angles of the two
further bodies immediately; rather it is possible, because the
measured angles are stored, to process these measured angles
regardless of the time at which measurement occurred.
[0010] It is particularly useful if each of the two further bodies
is equipped with a magnet, associated with which is an AMR sensor
that is provided for measuring the angle of the associated further
body; and if an analysis circuit is provided which is coupled to
the two AMR sensors and is provided for analyzing and optionally
for transforming the measured angles of the two further bodies. The
aforesaid AMR sensors are suitable for making an absolute
measurement of the angles of the two further bodies. The angles can
thus be measures with no need to impart any rotation to the two
bodies. The analysis circuit associated with the two AMR sensors is
provided in order to process the measured angles further in a first
step. In particular, it is possible for the analysis circuit to
transform the measured angles, for example, into pulse-length
modulated signals or other digital signals.
[0011] In an advantageous development of the invention, the
analysis circuit is equipped with means, in particular with
sample-and-hold elements, for storing the measured angles of the
two further bodies. The aforesaid decoupling of the measurement of
the angles of the two further bodies from the determination of the
angle of the first body is thereby accomplished in simple
fashion.
[0012] It is particularly useful if a calculation device, in
particular a programmable microprocessor, is provided for
determining the angle of the first body. This makes it possible, in
particularly simple fashion, to adapt the determination of the
angle of the first body, for example, to the geometry of the two
further bodies. All that is necessary in this context is to modify
the corresponding values in the program of the microprocessor.
[0013] In an advantageous embodiment of the invention, the
calculation device can generate a start signal with which
simultaneous measurement of the angles of the two further bodies by
the two AMR sensors can be triggered. The calculation device is
thus responsible for the simultaneous measurement of the angles of
the two further bodies. The calculation device triggers this
simultaneous measurement by generating a single start signal which
brings about measurements at both AMR sensors. This represents a
reliable but nevertheless very simple possibility for achieving
simultaneous measurement of the angles of the two further
bodies.
[0014] The result of this common start signal is that the angles of
the two further bodies are measured at a single sampling time, i.e.
simultaneously. The single sampling time is defined by the start
signal.
[0015] In an advantageous development of the invention, a line is
provided with which the calculation device is connected to the
analysis circuit, and on which the start signal can be delivered to
the analysis circuit. The analysis circuit is acted upon by the
start signal by way of this line.
[0016] Further features, potential applications, and advantages of
the invention are evident from the description below and from
exemplary embodiments of the invention which are depicted in the
Figures of the drawings. In this context, all features described or
depicted constitute, of themselves or in any combination, the
subject matter of the present invention, regardless of their
summarization in the claims or references thereto, and regardless
of their wording or depiction in the description or the
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 shows a schematic depiction of an exemplary
embodiment of an apparatus according to the present invention for
determining the angle of a first rotatable body;
[0018] FIG. 2 shows a schematic block diagram of an electrical
circuit for the apparatus of FIG. 1; and
[0019] FIG. 3 shows a schematic diagram of two signals occurring in
the circuit of FIG. 2.
DETAILED DESCRIPTION
[0020] FIG. 1 depicts an apparatus 1 which has a first rotatable
body and two further rotatable bodies. A gear 2 having a number of
teeth n is provided as the first rotatable body. The two further
rotatable bodies are also configured as gears 3, 4, gear 3 having a
number of teeth m, and gear 4 a number of teeth m+1.
[0021] Gear 2 is, for example, coupled to a steering wheel of a
motor vehicle. In particular, gear 2 is mounted on a shaft 5 which
constitutes a component of the aforesaid steering wheel.
[0022] Each of the two gears 3, 4 is equipped with a magnet 6, each
of magnets 6 generating a magnetic field oriented in a specific
direction.
[0023] The two gears 3, 4 and gear 2 are in engagement, so that a
rotation of gear 2 causes corresponding rotations of gears 3, 4.
Because of the different numbers of teeth on gears 2, 3, 4, the
rotation angles of gears 2, 3, 4 upon rotation are different.
[0024] The rotation angle of gear 2 can be less than 360.degree..
Especially when apparatus 1 is used for a steering wheel of a motor
vehicle, gear 2 can perform multiple rotations. In particular, the
rotation angle of gear 2 is, for example, 1440.degree.. The
rotation angles of the two gears 3, 4 are preferably not
limited.
[0025] FIG. 2 depicts a circuit 7 which is associated with
apparatus 1 of FIG. 1. Circuit 7 of FIG. 2 has two so-called AMR
sensors 8, 9, which are elements having a variable resistance (AMR
=anisotropic magnetic resistance). AMR sensors are sensors whose
resistance changes depending on how the sensor is oriented in an
external magnetic field. AMR sensors are therefore suitable for
sensing the rotation angles of bodies on which, for example, a
magnet is mounted. The two AMR sensors 8, 9 are connected to an
analysis circuit 10 which is made up of two blocks 11, 12; first
AMR sensor 8 acts on block 11, and second AMR sensor 9 on block 12.
Analysis circuit 10 is connected to a calculation device 13, in
particular to a microprocessor. A clock 14 and a memory 15 are
connected to calculation device 13. A power supply 16 generates a
supply voltage VCC which is supplied to calculation device 13,
clock 14, memory 15, the two blocks 11, 12 of analysis circuit 10,
and to the two AMR sensors 8, 9. When the circuit is used in a
motor vehicle, the aforesaid supply voltage VCC is generated from
the battery voltage of the motor vehicle.
[0026] The calculation device is connected to other devices via a
plurality of further lines. When circuit 7 is used in a motor
vehicle, calculation device 13 is connected by way of the aforesaid
lines, in particular, to a control device for controlling and/or
regulating the functions of the motor vehicle.
[0027] The two AMR sensors 8, 9 are associated with the two magnets
6 of the two gears 3, 4. Each of magnets 6 generates in the
associated stationary AMR sensor 8, 9 a voltage which depends on
the angle of the associated gear 3, 4. Rotation of the respective
gear 3, 4 causes a voltage profile which rises over an angle of
approximately 180.degree., and then declines again over an angle of
approximately 180.degree.. After one revolution of gear 3, 4, i.e.
after 360.degree., this voltage profile repeats.
[0028] FIG. 3 depicts the voltage profile generated by the two AMR
sensors 8, 9 when gears 3, 4 rotate. The rotation of gear 2, which
extends over a range from 0.degree. to 1440.degree., is plotted on
the horizontal axis. A rotation of this kind of gear 2 brings about
a plurality of rotations of gears 3, 4. This plurality of rotations
of gears 3, 4 in turn causes the voltages generated by the AMR
sensors 8, 9 to change. This is plotted on the horizontal axis of
the diagram of FIG. 3. A rise in the voltage profile means a
180-degree rotation of the associated gear 3, 4.
[0029] Because of the differing numbers of teeth on gears 3, 4,
different voltage profiles occur for the two AMR sensors 8, 9. As
depicted in FIG. 3, the voltage for the two AMR sensors 8, 9 when
gear 2 is at an angle of 0.degree. is also 0.degree.. When gear 2
then rotates, the voltage of the two AMR sensors 8, 9 rises.
Because of the differing numbers of teeth on the two gears 3, 4,
this rise occurs with differing slopes. The consequence is that the
two voltage profiles generated by AMR sensors 8, 9 are not
identical. This is evident from FIG. 3 in particular at somewhat
greater angles for gear 2, at which the two voltage profiles of AMR
sensors 8, 9 differ substantially from one another.
[0030] When apparatus 1 and circuit 7 are in operation, the voltage
of the two AMR sensors 8, 9 is measured. This voltage is equivalent
to the angles of the two gears 3, 4.
[0031] From these two measured angles of gears 3 and 4, and in
particular from the difference between the two aforesaid angles,
conclusions can be drawn as to the angle of gear 2. This
calculation of the angle of gear 2 involves the numbers n, m, and
m+1 for gears 2, 3, and 4. The correlation described above is
plotted in FIG. 3, as an example, for an angle W.
[0032] As is evident from FIG. 2, a line 17 is provided which
connects calculation device 13 to each of the two blocks 11, 12 and
thus to analysis circuit 10. On line 17 it is possible to deliver,
to analysis circuit 10 and in particular to the two blocks 11, 12,
a start signal S with which simultaneous measurement of the angles
of the two gears 3, 4, can be achieved. These simultaneously
measured angles of the two gears 3, 4 are then stored.
[0033] For this purpose, the two blocks 11, 12 each contain, in
particular, a sample-and-hold element which is connected to the
respectively associated AMR sensor 8, 9. The sample-and-hold
element is also acted upon by start signal S.
[0034] When calculation device 13 then generates start signal S,
for example by transferring on line 17 a binary signal from a "low"
to a "high" potential, the result is that the two sample-and-hold
elements in the two blocks 11, 12 simultaneously read in and store
the voltages supplied by the two AMR sensors 8, 9. This means that
the angles measured by the two AMR sensors for the two gears 3, 4
are stored synchronously in the sample-and-hold elements.
[0035] It is possible thereafter for the calculation device, with
the aid of further activation signals, to read the stored angles of
the two gears 3, 4 out of the sample-and-hold elements of the two
blocks 11, 12, and read them via corresponding lines 18, 19 into
calculation device 13 for further processing.
[0036] Start signal S present on line 17 thus results in a
synchronization of the two blocks 11, 12, and thus ultimately in a
synchronization of the measurement of the angles of the two gears
3, 4. This ensures an identical time reference for the measurement
of the angles of the two gears 3, 4. The consequence is that
because of the aforesaid identical time reference, a higher
accuracy can be achieved in the subsequent calculation of the angle
of gear 2.
[0037] The identical time reference for measuring the angles of the
two gears 3 and 4 is achieved with the aid of start signal S. The
sampling time, and thus the identical time reference, for the
measure of said angles is defined by way of the transition, already
mentioned above, in start signal S from a lower to a higher
potential. On the basis of start signal S, a common time reference
is created which results in a synchronization of the measurement of
the two angles and thus in a simultaneous measurement, i.e. a
measurement of the two angles at one sampling time. It is entirely
possible, in this context, for the sampling time to be identical to
a time generated by clock 14.
* * * * *