DE102012203153A1 - Device for contactless acquisition of relative moving element of drive motor for electronic steering system, has field sources stationary attached to sense elements, for detecting and evaluating evaluation electronics and radial component - Google Patents

Abstract

The device has magnetic field sources secured on a moving element (7). Magnetosensitive sensors (1, 2) i.e. hall sensors, of the magnetic field sources are spaced and arranged in a plane. The moving element is rotatably supported such that the plane is arranged parallel to a rotational axis (14). A common housing (4) accommodates lateral magnetic field sources that are stationary attached to sense elements (3a, 3b) arranged parallel to the rotational axis for detecting and evaluating associated evaluation electronics and a radial component of magnetic field. An independent claim is also included for a method for determination of absolute position of relative magnetosensitive sensors of a rotatable element.

Description

The invention relates to a device and a method for redundant, absolute position determination of a rotatable body. In particular, the invention relates to an apparatus and a method for absolute, redundant position determination for off-axis applications by means of magneto-sensitive sensors.

WO2007071383 relates to a device for non-contact, redundant position determination, in which two integrated, built on Hall sensor base magnetic angle sensor circuits are placed in a common housing on top of each other, wherein the two circuits are separated by an insulating intermediate layer.

In these angle sensors, a construction is essential in which the axis of rotation of the rotating magnet comes to lie centrally above the center of the integrated Hall sensor group arranged in a circle on the circuit. A lateral offset of the sensor elements relative to the axis of rotation leads to an increase of the angular error, in particular if the Hall sensors are located outside of the between the poles of the magnetic field source approximately linearly extending vertical magnetic field Bz.

A positioning of the circuits next to each other in a common housing is therefore not useful for this reason. In order to achieve a centering of both angle sensors relative to the axis of rotation of the magnetic field source, they must therefore be installed one above the other in the common housing.

A disadvantage of this structure is the higher cost of the superimposed mounting of the circuits with an intermediate additional insulation layer.

A further disadvantage is that the tolerance range for the vertical distance between magnet and sensor housing is severely limited by the superimposed structure, since both the bottom and the top angle sensor must be within a tolerance window for the optimum working range of the strength of the magnetic field ,

Furthermore, this structure is only suitable for axial construction, where the angle sensor circuit is below the magnetic field source, normal and centric to the axis of rotation.

In safety-critical applications, such as a drive motor for an electronic steering system EPS can e.g. When load changes forces act on the drive shaft to be measured, which move them in the axial direction. This displacement is affected by the axial structure in a change in distance between the magnetic field source, which is attached to the end of the drive shaft and the sensor. In order to avoid possible damage to the sensor or magnet due to mechanical contact between the two objects, a minimum distance between the magnetic field source and the sensor housing must be maintained, which in turn further limits the tolerance range for the distance between the sensor and the magnetic field source.

The invention has for its object to provide a redundant sensor system for so-called off-axis applications, i. Applications in which magneto-sensitive sensors are located outside the axis of symmetry of a movable body, which is able to provide a redundant position detection of a rotatably mounted body by means of two separate sensor systems. Magneto-sensitive sensors are to be understood in particular as Hall sensors.

This object is achieved with a device according to the independent claim. The dependent claims 2 and 3 relate to particular embodiments.

The invention relates to a device for non-contact detection of a relatively movable element which has a fixed magnetic field source on the movable element, wherein two lying in a plane, spatially offset in the direction of movement magneto-sensitive sensors are spaced from the magnetic field source. It is envisaged that the relatively movable element is rotatably mounted. In addition, it is provided that the plane is arranged parallel to the axis of rotation and that two sensor elements are housed in a common housing, which is mounted laterally of the magnetic field source stationary parallel to the axis of rotation, which two each lying in a plane, spatially in the direction of rotational movement offset magneto-sensitive sensors with the associated evaluation include and detect the radial component of the magnetic field and evaluate. The redundant sensor system comprises two sensor elements.

In one embodiment, it is provided that the absolute rotational position is detected over an angular range of 360 °, wherein the magnetic field source is formed as a 2-pole diametrically magnetized disc magnet or ring magnet.

In one embodiment, it is provided that the absolute rotational position is detected over an angular range of <360 °, the magnetic field source being a multi-pole magnetized disc magnet ( 9 ) or ring magnet ( 10 ) is trained.

• – dass Amplitudenverhältnisse durch Division eines vorgebbaren Signalhubs durch eine Differenz eines Maximumwertes und eines Minimumwertes der jeweiligen Sensorsignale bestimmt werden,
• – dass Offsetwerte um den jeweiligen Nullpunkt der Sensorsignale aus den Minimum- und Maximumwerten der Sensorsignale bestimmt werden,
• – dass mittels Subtraktion der Offsetwerte von den Sensorsignalen und durch Normierung mit den Amplitudenverhältnissen normierte Sensorsignale berechnet werden, wobei die Bestimmung der Minimum- und Maximumwerte durch eine relative Bewegung des Elements und der daran befestigten Magnetfeldquelle über einen vollen Bewegungsweg bei gleichzeitiger Erfassung der Sensorsignale beider Sensoren erfolgt,
• – dass von den normierten Sensorsignalen ein Summensignal und ein Differenzsignal gebildet werden,
• – dass das Summensignal und das Differenzsignal wiederum nach Bestimmung des Amplitudenverhältnisses normiert werden, wobei die Bestimmung der Minimum- und Maximumwerte durch relative Bewegung des Elements und der daran befestigten Magnetfeldquelle über einen vollen Bewegungsweg bei gleichzeitiger Messung des Summensignals sowie des Differenzsignals und Auswertung der Minimum- und Maximumwerte des Summensignals und des Differenzsignals erfolgt und
• – dass mittels des normierten Summensignals und des normierten Differenzsignals eine absolute Drehstellung der Magnetfeldquelle berechnet wird.

The invention also relates to a method with a device described above for determining the absolute position of a movable relative to two magneto-sensitive sensors element whose magnetic properties are determined by the magneto-sensitive sensors characterized in that a first sensor signal with a first magneto-sensitive sensor and a second sensor signal a second magneto-sensitive sensor is measured, wherein the first sensor signal and the second sensor signal represents a component of the magnetic field and the sensor signals have a phase offset φ in the range of 0 ° <φ <180 ° or 180 ° <φ <360 °, wherein it is provided

• - that amplitude ratios are determined by dividing a predeterminable signal deviation by a difference between a maximum value and a minimum value of the respective sensor signals,
• - That offset values are determined by the respective zero point of the sensor signals from the minimum and maximum values of the sensor signals,
• In that the determination of the minimum and maximum values is effected by a relative movement of the element and the magnetic field source attached thereto over a full movement path with simultaneous detection of the sensor signals of both sensors he follows,
• That a sum signal and a difference signal are formed by the normalized sensor signals,
• In that the summation signal and the difference signal are in turn normalized after determination of the amplitude ratio, wherein the determination of the minimum and maximum values by relative movement of the element and the attached magnetic field source over a full path of movement with simultaneous measurement of the sum signal and the difference signal and evaluation of the minimum and maximum values of the sum signal and the difference signal occur and
• - That by means of the normalized sum signal and the normalized difference signal, an absolute rotational position of the magnetic field source is calculated.

In one embodiment of the method, it is provided that the component of the magnetic field is the radial or the axial component.

In one embodiment of the method, it is provided that the absolute rotational position of the magnetic field source is calculated by forming the arctangent of the ratio of the normalized sum signal and the normalized difference signal.

In one embodiment of the method, it is provided that the absolute rotational position of the magnetic field source is calculated by means of an algorithm of the coordinate transformation, preferably with a CORDIC algorithm.

The invention will now be further explained with reference to embodiments and associated figures. Show it:

1 the construction of two sensor elements in a vertical arrangement,

2 the construction of two sensor elements in a parallel arrangement,

3 an arrangement for the redundant measurement of a rotational position with a radial structure,

4 a top view of 3 .

5 - 8th various embodiments of suitable magnetic field sources,

9 an analog block diagram of the signal processing,

10 a digital block diagram of signal processing, and

11 to 15 Waveforms.

1 shows the structure of the two sensor elements 3a . 3b in the common housing 4 : the sensor elements 3a and 3b are identical and each contain two Hall sensors 1a . 2a such as 1b . 2 B , In addition, each of the electronics for signal processing is integrated on the sensor element. The two sensor elements 3a . 3b are rotated 180 ° to each other. The resulting measurement results are opposite in relation to each other and must be considered accordingly in the evaluation in an external processing unit. This structure can simplify the electrical connection between the sensor element and the electrical connections of the housing, if, for example, the electrical connections of the sensor element are located only on one longitudinal side of the sensor element, which then directly faces the corresponding contact rows of the sensor housing.

In 2 the two sensor elements are arranged parallel to each other. In this embodiment, the resulting measurement results are the same relative to each other.

3 shows an embodiment for redundant measurement of a rotational position with radial structure. One around a rotation axis 14 rotatably mounted object 6 contains a connected to this magnetic field source 7 , its radial field by means of two sensor systems 3a . 3b measured and evaluated.

The sensitive to the measurement of magnetic fields axes of the integrated Hall sensors are shown in the form of arrows.

An absolute change in the magnetic field strength, as e.g. When the temperature of the magnet changes, there is no influence on the accuracy of the measuring principle, since the evaluation of the measured signals takes place ratiometrically and thus compensates for changes in the signal amplitude, provided that they act on all Hall sensors equally.

In case of 3 This also applies if the rotatable element 6 with the magnetic field source attached thereto 7 moves in the axial direction. The axial displacement can cause different signal amplitudes in the four Hall sensors, but this signal change acts on all Hall sensors in the same way and is thus compensated.

The advantage of this embodiment lies in particular in a large tolerance to axial displacements of the rotatably mounted parts 6 . 7 ,

Furthermore, this embodiment is also suitable for ring magnets and hollow shafts, since the magnetic field of the magnetic field source is measured at its periphery.

4 shows a plan view of 4 , An exact centering of the sensor elements 3a . 3b to the axis of rotation 14 is not necessary because these tolerances can be compensated by a reference travel after assembly of the sensor system

5 - 8th show various embodiments of suitable magnetic field sources:

5 and 6 show a 2-pole diametrically magnetized disc magnet 7 or ring magnet 9 , with which a determination of the absolute rotational position over 360 ° is possible.

7 and 8th show a multi-pole magnetized disc magnet 8th or ring magnet 10 , The illustrations shown here show an embodiment with 4 poles, the application of the invention is not limited to this number of poles, but applies to any number of pole pairs. The maximum absolutely measurable rotational position range in these embodiments is 360 ° / pp, where pp corresponds to the number of pole pairs of the magnets. When using these magnetic field sources

The following explains the associated method.

In 11 and 12 is analog signal processing path in block 100 and the digital signal processing path in block 200 shown.

In the embodiment how 11 shown, it is assumed that the measured signals of the Hall sensors 1 . 2 have a phase angle of 30 °, already pre - amplified and due to influences of the Positioning accuracy and due to process engineering tolerances both with offset voltages and with different signal levels are afflicted.

In a first step, the offset voltage of the sensor signals 101 . 102 subtracted and the signal levels to a normalized signal swing (for example, 2V _ss ) aligned. The normalized signal levels stand as a signal 107 and 108 available and are in 12 shown.

In order to calculate the required trimming values for Offset1, Offset2, Gain1 and Gain2, it is sufficient to calculate the minimum and maximum values of the sensor signals 101 . 102 to investigate. This can be achieved by simply rotating the magnetic field source while simultaneously determining the minimum and maximum values of the sensor signals 101 and 102 happen.

für

H1_max,min

= Maximum- bzw. Minimumwert von Sensorsignal1 101

H2_max,min

= Maximum- bzw. Minimumwert von Sensorsignal2 102

From the minimum and maximum values, the values necessary for trimming can then be calculated as follows:

For

H1 _{max, min}

= Maximum or minimum value of sensor signal1 101

H2 _{max, min}

= Maximum or minimum value of sensor signal2 102

Of these normalized signals, the next step is the sum 109 and the difference 110 educated. In 13 these signals are shown.

The ratio of the signal swing from the sum signal to the difference signal depends on the phase angle φ of the input signals 101 . 102 from. However, the phase angle φ of the sum signal to the difference signal is always 90 °. An exception are the special cases of the phase positions φ = 360 ° = 0 ° and φ = 180 °, in which a determination of the rotational position is not possible because at φ = 180 °, the sum signal to 0 and at φ = 360 ° = 0 ° the difference signal becomes 0.

In 15 this relation is shown graphically. The X-axis shows the phase relationship of the input signals 101 . 102 and the y-axis shows the amplitude ratio of the peak values from the sum signal to the difference signal.

zu Phasenlage errechnet sich aus:

The mathematical relationship of the peak values of sum signal by difference signal

to phase position is calculated from:

In a further step, the sum signal 109 and the difference signal 110 again normalized to a predetermined value, for example 2V _ss .

In order to calculate the required trim values for Gain3 and Gain4, it is sufficient to determine the minimum and maximum values of the sum and difference signal. This can be done by simply rotating the magnetic field source 5 done over a full period with simultaneous determination of the minimum and maximum values of the sum and difference signal.

From the minimum and maximum values, the values necessary for trimming can then be calculated as follows:

Assuming that the normalized sensor signals 107 . 108 correspond to a pure sinusoidal shape and have no offset voltage more, so created by the sum and difference also no additional offset. This can be checked by means of the minimum and maximum values of the sum and difference signal and if necessary also corrected:

The normalized signals of the sum signal 113 and the difference signal 114 thus result in two signals exactly phase-shifted by 90 ° with the same signal swing. These signals are now used directly to calculate the rotational position.

H1

= Sensorsignal von Hallsensor1 101

H2

= Sensorsignal von Hallsensor2 102

Offset1

= Offsetsignal von Hallsensor1 103

Offset2

= Offsetsignal von Hallsensor2 104

Gain1

= Verstärkung des Sensorsignals H1 105

Gain2

= Verstärkung des Sensorsignals H2 106

Gain3

= Verstärkung des Summensignals 111

Gain4

= Verstärkung des Differenzsignals 112

Subsequently, the normalized sum signal 113 with Vsin and the normalized difference signal 114 described with Vcos. Vsin = Gain3 * [Gain1 * (H1-Offset1) + Gain2 * (H2-Offset2)] [11] Vcos = Gain4 * [Gain1 * (H1-Offset1) -Gain2 * (H2-Offset2)] [12] For

H1

= Sensor signal from Hall sensor1 101

H2

= Sensor signal from Hall sensor2 102

Offset 1

= Offset signal from Hall sensor1 103

Offset 2

= Offset signal from Hall sensor2 104

Gain1

= Amplification of the sensor signal H1 105

Gain2

= Amplification of the sensor signal H2 106

GAIN3

= Amplification of the sum signal 111

Gain4

= Amplification of the difference signal 112

Starting from the input signals Vsin 113 and Vcos 114 can the absolute rotational position W 202 the magnetic field source using the arctangent function W = arctan Vsin / Vcos [13] or other suitable means of coordinate transformation, such as a digital CORDIC algorithm.

The amount value B 203 the coordinate transformation is constant for all rotational positions and is: B = √ Vsin² + Vcos² = const. [14]

12 shows the normalized sum signal 113 = Vsin, as well as the normalized difference signal 114 = Vcos.

Furthermore, the absolute rotational position calculated from Vsin and Vcos is determined in a second ordinate axis 202 shown in a scaling of +/- 180 °.

In many applications, it may be useful to calculate the calculated rotational position with a defined mechanical position of the rotatable element 6 to reconcile, for example, the zero position of a turntable. To facilitate this, can be any rotational position by subtracting a zero reference value 204 be set to zero.

Furthermore, the achieved accuracy of the displayed rotational position optionally by a linearization circuit 205 increase. Typical forms of linearization are tables or mathematical correction functions which try to match the calculated rotational position to reference points defined by the user.

Subsequently, the calculated and linearized rotary position W_L can be converted into an analogue signal form 207 or a digital waveform 208 be made available to the user

In an advantageous embodiment, as in 10 shown, the signal processing can be performed by digital means. The of the Hall sensors 1 . 2 generated signals 101 . 102 be directly by means of an analog-to-digital converter 201/1 converted into a digital waveform and the under 18 , Block 100 described signal processing steps are performed in a digital processing unit. The necessary parameters for gain, offset, zero point and linearization can be stored in a digital memory.

The invention has been explained in more detail with reference to examples and figures, this presentation is not intended to limit the invention. It is understood that those skilled in the art can make changes and modifications without departing from the scope of the following claims. In particular, the invention includes embodiments with any combination of features of the various embodiments described herein.

LIST OF REFERENCE NUMBERS

1

 first magneto-sensitive sensor

1a

 first magneto-sensitive sensor of the first sensor element

1b

 first magneto-sensitive sensor of the second sensor element

2

 second magneto-sensitive sensor

2a

 second magneto-sensitive sensor of the first sensor element

2 B

 second magneto-sensitive sensor of the second sensor element

3

 Sensor element comprising two magneto-sensitive sensors

3a

 first sensor element

3b

 second sensor element

2

 second magneton-sensitive sensor

4

 common housing

5

 common substrate

6

 rotatable element

7

 2-pole diametrically magnetized disc magnet

8th

 multi-pole magnetised disc magnet

9

 2-pole diametrically magnetized ring magnet

10

 multi-pole magnetized ring magnet

14

 axis of rotation

15

 magnetic field source

101

 first sensor signal

102

 second sensor signal

103

 first offset

104

 second offset

105

 first reinforcement

106

 second reinforcement

107

 first normalized sensor signal

108

 second normalized sensor signal

109

 sum signal

110

 difference signal

113

 normalized sum signal

114

 normalized difference signal

202

 absolute rotational position

203

 Absolute value B of the coordinate transformation

207

 analog signal form

208

 digital waveform

100

 analog signal processing block

200

 digital signal processing block

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 2007071383 [0002]

Claims (7)

Device for non-contact detection of a relatively movable element, which is mounted on the movable element ( 6 ), wherein two in a plane, spatially offset in the direction of movement magneto-sensitive sensors ( 1 . 2 ) from the magnetic field source ( 15 ) are arranged spaced, characterized in that the relatively movable member is rotatably mounted, that the plane is arranged parallel to the axis of rotation and that in a common housing ( 4 ), which is mounted laterally of the magnetic field source stationary parallel to the axis of rotation, two sensor elements ( 3a . 3b ) are accommodated, which each have two in one plane, in the direction of the rotational movement spatially offset magneto-sensitive sensors ( 1a . 2a ) and ( 1b . 2 B ) with the associated evaluation electronics and detect and evaluate the radial component of the magnetic field. Apparatus according to claim 1, characterized in that the absolute rotational position over an angular range of 360 ° is detected, wherein the magnetic field source as a 2-pole diametrically magnetized disc magnet ( 7 ) or ring magnet ( 9 ) is trained. Apparatus according to claim 1, characterized in that the absolute rotational position over an angular range of <360 ° is detected, wherein the magnetic field source as a multi-pole magnetized disc magnet ( 8th ) or ring magnet ( 10 ) is trained. Method for determining the absolute position of a member rotatable relative to two magneto-sensitive sensors with a device according to one of claims 1 to 3, wherein a first sensor signal ( 101 ) with the first magnetosensitivity sensor and a second sensor signal ( 102 ) is measured with the second magneto-sensitive sensor, wherein the first sensor signal ( 101 ) and the second sensor signal ( 102 ) represents a component of the magnetic field and the sensor signals ( 101 . 102 ) have a phase offset φ in the range of 0 ° <φ <180 ° or 180 ° <φ <360 °, characterized in that - amplitude ratios by dividing a predetermined signal stroke by a difference of a maximum value and a minimum value of the respective sensor signals ( 101 . 102 ), that offset values ( 103 . 104 ) around the respective zero point of the sensor signals ( 101 . 102 ) from the minimum and maximum values of the sensor signals ( 101 . 102 ), that by subtracting the offset values from the sensor signals ( 101 . 102 ) and normalized by normalization with the amplitude ratios sensor signals ( 107 . 108 ), wherein the determination of the minimum and maximum values by a relative movement of the element and the attached magnetic field source over a full path of movement with simultaneous detection of the sensor signals ( 101 . 102 ) of both sensors ( 1 . 2 ), that - of the normalized sensor signals ( 107 . 108 ) a sum signal ( 109 ) and a difference signal ( 110 ), - that the sum signal ( 109 ) and the difference signal ( 110 ) are normalized again after determination of the amplitude ratio ( 113 . 114 ), wherein the determination of the minimum and maximum values by relative movement of the element and the attached magnetic field source over a full path of movement with simultaneous measurement of the sum signal ( 109 ) as well as the difference signal ( 110 ) and evaluation of the minimum and maximum values of the sum signal ( 109 ) and the difference signal ( 110 ) and - that by means of the normalized sum signal ( 113 ) and the normalized difference signal ( 114 ) an absolute position ( 202 ) of the magnetic field source is calculated. Method according to claim 4, characterized in that the component of the magnetic field is the radial or the axial component. Method according to claim 4 or 5, characterized in that the absolute rotational position ( 202 ) of the magnetic field source by forming the arctangent of the ratio of the normalized sum signal ( 113 ) and the normalized difference signal ( 114 ) is calculated. Method according to one of claims 4 to 6, characterized in that the absolute rotational position ( 202 ) of the magnetic field source is calculated by means of a coordinate transformation algorithm, preferably with a CORDIC algorithm.

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