Patent Description:
Magnetic sensor systems, in particular linear or angular position systems are known in the art. They offer the advantage of being able to measure an angular position without making physical contact.

It is a challenge to build a sensor system that is substantially insensitive to a constant external magnetic disturbance field (also known as "fremdfeld"). This problem is known in the art, and is addressed in different ways.

<CIT> describes sensor arrangements for measuring an angular position using a multi-pole magnet. Some embodiments described therein address the problem of robustness against an external disturbance field by using a multi-pole magnet and by determining the angular position by measuring magnetic field gradients rather than magnetic field values per se.

<CIT> discloses a sensor system (duplicated in <FIG>, which is a replica of <FIG> of US'<NUM>) comprising a permanent magnet and two angle sensor devices, one adapted for providing a first angle ϕ1, the other for providing a second angle ϕ2 respectively, as shown in <FIG> which is a replica of <FIG> of US'<NUM>. Both individual angles ϕ1, ϕ2 are incorrect in the presence of an external disturbance field Bd. If the disturbance field is small (e.g. more than <NUM> times smaller than the field of the magnet), and if the external field is oriented substantially perpendicular to the field of the magnet, the error due to the external disturbance field can be reduced based on a combination of the angles ϕ1 and ϕ2, but not completely eliminated.

<CIT> discloses an angle sensor with a plurality of at least four sensors, each providing an angle which is disturbed by an external disturbance field, and a processor for determining an overall angular position using least mean squares for reducing the errors.

The present invention is related to a linear position sensor system as defined by independent claim <NUM>.

It is an object of embodiments of the present invention to provide a position system capable of determining a position of a magnetic field generator (e.g. a permanent magnet), in a manner that is highly insensitive to a disturbance field, in particular a constant disturbance field.

It is an object of particular embodiments of the present invention to provide a linear position system capable of determining a linear position of a magnetic field generator (e.g. a permanent magnet), in a manner that is capable of providing an accurate position, even if this disturbance field has a magnitude larger than <NUM>% or larger than <NUM>% or larger than <NUM>% of the magnitude as that of the magnetic field generated by the magnetic field generator (e.g. permanent magnet).

It is an object of particular embodiments of the present invention to provide such a position system comprising sensor devices which, when considered alone, are not robust against an external disturbance field.

It is an object of particular embodiments of the present invention to provide such a linear position system comprising only two sensor devices which, when considered alone, are not robust against an external disturbance field, but the system being substantially insensitive to a disturbance field, even if the disturbance field has a magnitude larger than <NUM>% of the magnetic field generated by the magnetic field generator (e.g. permanent magnet). The two sensor devices may be two discrete integrated circuits (ICs).

This document also discloses a method for determining a linear or angular position of the magnetic field generator (e.g. permanent magnet).

It is an object of particular embodiments of the present invention to provide a system wherein the magnetic field generator and the sensor devices are arranged in a particular manner (position and/or orientation) such that the complexity of the algorithm for determining the linear or angular position is reduced, without compromising the robustness against the external disturbance field (if present).

It is an object of particular embodiments of the present invention to provide a linear position system where the mounting requirements of the sensor devices and the magnetic field generator are drastically reduced, without compromising the robustness against the external disturbance field (if present).

These objectives are accomplished by a linear position sensor system according to embodiments of the present invention.

The present invention provides a linear position sensor system as defined by independent claim <NUM>.

With "eliminates the external disturbance field, even if its magnitude is in the same order of magnitude as the magnetic source" is meant for example: "without assuming that the external disturbance field has a particular orientation" and without assuming that the magnitude of the external disturbance field is smaller than <NUM>% of the field created by the magnetic source".

The vector data may be 2D-vector data or 3D-vector data.

With the "first magnetic field vector being different from the second magnetic field vector" is meant two different vectors when expressed in absolute coordinates.

The first sensor device and the second sensor device are preferably located in different positions.

The first sensor device can determine the first vector data with reference to a first local coordinate system, for example having axes X1, Y1 or X1, Y1, Z1, and the second sensor device can determine the second vector data with reference to a second local coordinate system, for example having axes X2, Y2 or X2, Y2, Z2. These coordinate systems may be fully aligned (i.e. the <NUM> corresponding axes are parallel), or not aligned (i.e. none of the <NUM> corresponding axes are parallel), or partly aligned (e.g. X1 and X2 are aligned, but Y1 and Y2 are not, and Z1 and Z2 are not).

In preferred embodiments, these axes correspond to directions of maximum sensitivity of sensors (e.g. sensor circuits or sensor elements) used in the first and second devices. For example the Z-axis could typically correspond to a direction perpendicular to the semiconductor plane, and the Z-component can e.g. be measured by a so called "horizontal Hall element". The X-axis and the Y-axis are typically two axes parallel to the semiconductor plane, and perpendicular to each other. The X-component and Y-component can for example be measured using two vertical Hall elements, but other sensor elements or sensor structures may also be used.

It is a major advantage of this angular position system that the influence of an external magnetic field can be reduced, e.g. substantially eliminated, by combining the vector information obtained from said two sensor devices.

It is an advantage of this algorithm that it does not have to rely on the magnitude of the external field being negligibly small, for example having a magnitude smaller than <NUM>% of the magnitude of the magnetic field provided by the magnetic field generator (e.g. permanent magnet).

It is an advantage of this algorithm that it still provides the correct angular value, even if the magnitude of the external disturbance field is larger than <NUM>% or even larger than <NUM>% of the magnitude of the magnetic field provided by the magnetic field generator.

The processor can be a processor inside one of the sensor devices, or inside both of the sensor devices, or an external processor, or combinations thereof. Of course, the sensor devices would be interconnected and/or connected to said external processor for providing said vector data. This communicative connection may be a wired connection or a wireless connection.

In an embodiment, the first sensor device is adapted for measuring the first combined magnetic field vector in only two dimensions or in three dimensions, and for providing two or only two values or three values corresponding to said two-dimensional or three-dimensional vector data; and the second sensor device is adapted for measuring and providing the second combined magnetic field vector in only two dimensions or in three dimensions, and for providing two or only two values or three values corresponding to said two-dimensional or three-dimensional vector data; and said method is based on solving a set of equations using two or only two or three values measured from each sensor.

An algorithm that uses at least two values from each sensor is clearly different from an algorithm that uses only a single value from each sensor, such as e.g. an angle value.

The set of equations may be a set of linear equations. An algorithm bases on first solving a set of linear equations to completely eliminate the external magnetic field components, and then finding the angular position based on the remaining equations where the external field does not play a role, is clearly different from a set of equations which assumes that the external field has a small amplitude, the influence of which can be reduced by taking multiple measurements in several directions, e.g. using least-mean-squares approximation.

According to the invention, the position sensor system is a linear position sensor system; and the position is a linear position; and the magnetic field generator is movable along a longitudinal axis, or the first and second sensor are movable along a longitudinal axis; and the first and second magnetic sensor device have a predefined first and second position and a predefined first and second orientation relative to said longitudinal axis.

This document also describes an angular position sensor system; and the position is an angular position; and the magnetic field generator is rotatable about a longitudinal axis; and the first and second magnetic sensor device have a predefined first and second position and a predefined first and second orientation relative to said longitudinal axis.

In an embodiment, both the first sensor device and the second sensor device are substantially located on the axis of the magnetic field source.

With "substantially located on the axis" is meant for example that a radial offset from the axis is less than <NUM>, preferably less than <NUM>, or less than <NUM>.

In an embodiment, the first sensor device is substantially located on the axis of the magnetic field source; and the second sensor device is located at a distance of at least <NUM> from the axis, for example a distance larger than <NUM>, or larger than <NUM>, or larger than <NUM>, or larger than <NUM>, or larger than <NUM> or larger than <NUM>.

Or stated in other words, in this embodiment, the first sensor device is located "on-axis", while the second sensor device is located "off-axis". It is an advantage of this embodiment that the first and second magnetic field vectors are typically quite different for all angular positions, and that the physical placement of these sensor devices may be easier.

In an embodiment, both the first sensor device and the second sensor device are located at a distance of at least <NUM> from the axis, for example a distance larger than <NUM>, or larger than <NUM>, or larger than <NUM>, or larger than <NUM>, or larger than <NUM> or larger than <NUM>. Or stated in other words, in this embodiment, the first and the second sensor device are both located "off-axis".

In an embodiment, the first sensor device comprises a first substrate defining a first plane; and the second sensor device comprises a second substrate defining a second plane; and the first and second sensor device are oriented such that the first plane and the second plane are substantially perpendicular.

It is an advantage of this embodiment that the perpendicular arrangement can simplify the set of equations.

In an embodiment, the first sensor device has at least two magnetic sensors defining at least two different directions of maximum sensitivity (e.g. X1,Y1; X1,Z1; X1,Y1,Z1) corresponding to a first local coordinate system; and the second sensor device has at least two magnetic sensors defining at least two different directions of maximum sensitivity (e.g. X2,Y2; X2,Z2; X2,Y2,Z2) corresponding to a second local coordinate system; and none of the axes of the first coordinate system is parallel to any of the axes of the second coordinate system.

It is an advantage of this embodiment that the first and second sensor can be oriented in any direction, making the mechanical design easier. Yet, by solving the set of equations, the angular position can be uniquely determined. In particular embodiments, the positions of the first and second sensor can be specifically chosen to simplify the set of equations.

In an embodiment, at least one or at least two or all three components of the first magnetic field vector and the second magnetic field vector provided by the magnetic field source are different for all angular positions of the magnetic field source.

It is an advantage that at least one component, but preferably at least two components or at least three components are different, because this not only ensures that the set of equations only has a single solution, but moreover may provide an over-specified set of equations, which may help to improve accuracy due to for example rounding errors.

In preferred embodiments, their amplitude is different by at least <NUM>%, or their orientations are different by at least <NUM>° or at least <NUM>° or at least <NUM>° or at least <NUM>°, or both.

With "the first vector and the second vector are different" is meant that their magnitude is different or their orientation is different, or both.

In an embodiment, the first sensor device comprises a first substrate defining a first plane; and the second sensor device comprises a second substrate defining a second plane; and the first plane and the second plane are substantially parallel.

It is an advantage of this embodiments, that the external disturbance field components measured by the first and second sensor are identical, except for an in-plane rotation, which can be mathematically described as a two-dimensional matrix-calculation with fixed coordinates, depending on the alignment of the axis of the two sensor devices, which are fixed over time, and can be determined by calibration.

In an embodiment, the first plane and the second plane coincide.

It is an advantage of this embodiment that the two sensor devices may for example be mounted on a single PCB.

In an embodiment, the first sensor device and the second sensor device are located substantially on said axis.

In an embodiment, the magnetic field source is adapted to provide the first magnetic field vector to the first sensor device and the second magnetic field vector to the second sensor device in a manner such that a first projection of the first magnetic field vector in the first plane is parallel or anti-parallel to a second projection of the second magnetic field vector in the second plane.

It is an advantage of this embodiment that the first plane and second plane are parallel, because then the influence of a constant external disturbance field oriented in any direction X,Y,Z, is exactly the same in both planes.

It is an advantage that the magnet provides a first magnetic field vector to the first sensor device, and a second magnetic field vector to the second sensor device, which first and second magnetic field vector is either parallel (i.e. define an angle of about <NUM>°) or anti-parallel (i.e. define an angle of about <NUM>°), because this allows geometrical symmetry considerations to be used to simplify the calculations, in a manner which allows to fully eliminate the influence of the external field by simple vector addition or subtraction.

In an embodiment, the first projection of the first magnetic field vector B1mag in the first plane is anti-parallel to the second projection of the second magnetic field vector B2mag in the second plane; and the method comprises calculating the position based on the following set of formulas or an equivalent set of formulas: <MAT> where (v1x, v1y) are vector coordinates of the first total vector v1 measured by the first sensor device, and (v2x, v2y) are vector coordinates of the second total vector v2 measured by the second sensor device, and (B1magx, B1magy) are vector-coordinates of the first projection of the field created solely by the magnetic generator.

The first and second sensor device may be located on said axis.

It is an advantage of this embodiment, that the angular position can be calculated using simple subtraction of vectors, and that no value needs to be determined during calibration, but the mounting requirements of the sensor devices are somewhat more stringent.

In an embodiment, the magnetic field generator (e.g. the permanent magnet) is located between the two planes.

In an embodiment, the first plane and the second plane are a single plane, and the sensor devices are located on the same side as the magnet, adjacent each other.

In an embodiment, the system is adapted for calculating the angular position according to the following formula: α=arctan(B1magy / B1magx).

It is an advantage of this embodiment, that the angular position can be calculated using a single goniometrical function, which can be implemented for example using a look-up table, which is optionally interpolated. It is noted however that a perfect arctangent function is not required, and the look-up table may compensate for higher harmonics, for example.

In an embodiment, the first sensor device is configured for measuring an in-plane field component (e.g. B1x in a direction parallel to the semiconductor plane of the first sensor device) and an out-of-plane field component (e.g. B1z in a direction perpendicular to the semiconductor plane) at the first sensor position, and the second sensor device is configured for measuring an in-plane field component (e.g. B2x in a direction parallel to the semiconductor plane of the second sensor device) and an out-of-plane field component (e.g. B2z in a direction perpendicular to the semiconductor plane) at the second location; and the magnetic source is magnetized such that, and the first sensor device is oriented relative to the magnetic field source such that the first in-plane field component (e.g. B1x) is substantially <NUM>° phase shifted relative to the first out-of-plane field component (e.g. B1z), (or stated in other words: such that a waveform of the first in-plane field component as a function of the position is <NUM>° phase shifted with respect to a waveform of the first out-of-plane field component as a function of the position); and wherein the magnetic source is magnetized such that, and the second sensor device is oriented relative to the magnetic field source such that the second in-plane field component (e.g. B2x) is substantially <NUM>° phase shifted relative to the second out-of-plane field component (e.g. B2z); and wherein the first and the second sensor device are spaced apart such that the first in-plane magnetic field component (e.g. B1x) is phase shifted relative to the second in-plane magnetic field component (e.g. B2x) by a value in the range from <NUM>° to <NUM>°, or a value in the range from <NUM>° to <NUM>°, or a value in the range from <NUM>° to <NUM>°, or a value in the range from <NUM>° to <NUM>°, or a value in the range from <NUM>° to <NUM>°, e.g. equal to about <NUM>°.

In this embodiment, (illustrated for example in <FIG>, <FIG> and <FIG>), the position and orientation of the sensor devices with respect to the magnetic source is specifically chosen, such that the at least four signals measured by the sensor devices are <NUM>° and <NUM>° phase shifted with respect to each other. This allows the angular position to be determined in a manner which is completely insensitive to an external disturbance field, and moreover, using a relatively simple set of formulas.

The first and second sensor device may be located off-axis (e.g. at a distance of at least <NUM> from the axis).

In an embodiment, the method is adapted for calculating the angular position based on the following set of formulas: <MAT> where (v1x, v1z) are vector coordinates of the first vector v1 measured by the first sensor device, and (v2x, v2z) are vector coordinates of the second vector v2 measured by the second sensor device, and (B1magx, B1magz) are vector-coordinates of the magnetic field created solely by the magnetic generator.

It is an advantage of this embodiment, that it involves mere subtraction of values obtained measured by the sensors. It should be appreciated that the value v1x itself may vary with an external disturbance field, but the difference signal (v1x-v2x) does not, and due to the specific placement of the two sensor devices.

The inventors surprisingly found that this particular arrangement of the sensors devices leads to leads to extremely simple formulas. As far as is known to the inventors, this particular arrangement is not known in the art.

In an embodiment, the system is adapted for calculating the angular position α based on the following formula: α=arctan(B1magz / B1magx).

In practice, the processor performing this method may calculate an arctangent function, or may obtain this value using a look-up table, or in any other suitable way.

In an embodiment, the angular position system comprises only two sensor devices including said first sensor device and said second sensor device.

It is a major advantage of such embodiment that only two sensor devices are required (in contrast for example to systems where at least four sensor devices are used, and where the influence caused by the external disturbance field is not completely eliminated by design, by merely reduced, e.g. using least mean squares).

This document also describes a computer-implemented method for determining a position of the magnetic field generator of a position sensor system according to the first aspect, in a processor; the method comprising the following steps: a) receiving first vector data from a first sensor device, the first vector data being two-dimensional data (e.g. two in-plane field components, or one in-plane component and one out-of-plane component) or three-dimensional data related to a combination of said first magnetic field vector and an external disturbance field, if such disturbance field is present; b) receiving second vector data from a second sensor device, the second vector data being two-dimensional data (e.g. two in-plane field components, or one in-plane component and one out-of-plane component) or three-dimensional data related to a combination of said second magnetic field vector and said external disturbance field, if present; c) determining a position of the magnetic field generator based on the first vector data and the second vector data in a manner which eliminates the external disturbance field, even if a magnitude of the external disturbance field is in the same order as the field generated by the magnetic field generator.

This method can be executed by a processor embedded inside one or both sensor devices, or by an external processor, connected to these sensor devices.

In an embodiment, the first sensor device is adapted for measuring two in-plane field component values (e.g. v1x, v1y), or for measuring one in-plane field component value and one out-of-plane field component value (e.g. v1x, v1z), or for measuring three values (e.g. v1x, v1y, v1z) corresponding to said two-dimensional or three-dimensional vector data; and the second sensor device is adapted for measuring two in-plane field component values (e.g. v2x, v2y), or for measuring one in-plane field component value and one out-of-plane field component value (e.g. v2x, v2z), or for measuring three values (e.g. v2x, v2y, v2z) corresponding to said two-dimensional or three-dimensional vector data; and said algorithm is based on solving a set of equations using at least two values from each sensor device.

In preferred embodiments, the set of equations is a set of linear equations, meaning a set of first order polynomial equations of a plurality of variables including variables for the external disturbance field (Bext), e.g. a plurality of variables representing magnetic field strength of a magnetic field created by the magnetic field source (e.g. permanent magnet), and magnetic field strength of the unknown external disturbance field.

In preferred embodiment, the set of linear equations contains (or is reduced to) only two linear equations.

In an embodiment, the first sensor device is adapted for measuring the first combined magnetic field vector and for providing two values or three values corresponding to said two-dimensional or three-dimensional vector data; and the second sensor device is adapted for measuring and providing the second combined magnetic field vector and for providing two values or three values corresponding to said two-dimensional or three-dimensional vector data; and said algorithm is based on solving a set of equations using at least two values from each sensor device.

With "combined magnetic field" or "total magnetic field" is meant: the combination (or superposition) of the magnetic field generated by the magnetic source, e.g. permanent magnet and the external disturbance field.

In preferred embodiments, the method may be adapted for determining the angular position for a specific arrangement (position and/or orientation) of the two sensor devices, as described above.

The present invention is related to a linear position sensor systems, e.g. as illustrated in <FIG>, which can be seen as variants of the angular position sensor systems of <FIG>.

In this document, unless explicitly mentioned otherwise, the term "sensor" can refer to a magnetic sensor device, or a magnetic sensor element, depending on the context.

In this document, the term "sensor element" or "magnetic sensor element" refers to a component or a sub-circuit or a structure capable of measuring a magnetic quantity, such as for example a magneto-resistive element, a horizontal Hall plate, a vertical Hall plate, a Wheatstone-bridge containing at least one (but preferably four) magneto-resistive elements, etc..

In this document, the term "sensor device" or "magnetic sensor device" refers to an arrangement (e.g. on a semiconductor substrate or semiconductor die) of at least three sensor elements which are not collinear, e.g. at least four sensor elements which are located in a single plane. The sensor device may be comprised in a package, also called "chip", but that is not absolutely required.

In this document, the expression "in-plane components of a vector" and "X and Y component of a perpendicular projection of the vector in the plane" mean the same. In case of two sensor chips, each containing a semiconductor substrate, a projection of the magnetic field vectors in the planes defined by said substrates is meant.

In this document, the term "two vectors being parallel or anti-parallel" means that the two vectors define an angle of <NUM>° or <NUM>° with respect to each other. In other words, their carriers are parallel, but the vector may point in the same or opposite directions.

Unless explicitly mentioned otherwise, the expression "two vectors being parallel" means that their carriers are parallel, irrespective of their direction (same or opposite).

In this document the terms "magnetic field generator" and "magnetic source" mean the same, and may refer to an arrangement comprising one or more coils, or to an arrangement comprising one or more permanent magnets, or the like. The permanent magnet may be a dipole magnet, or a multi-pole magnet having at least four poles, or at least six poles, or at least eight poles. The permanent magnet may be a bar magnet or a ring magnet or a disk magnet, etc..

The present invention provides several angular position systems <NUM> (see <FIG>), <NUM> to <NUM> (see <FIG>), <NUM> (see <FIG>), <NUM> (see <FIG>) and <NUM> (see <FIG>) and <NUM> (see <FIG>), and <NUM> (see <FIG>), and <NUM> (see <FIG>), and <NUM> (see <FIG>), and <NUM> (see FIG. <NUM>) comprising a magnetic field generator <NUM>, <NUM> (e.g. an arrangement comprising one or more coils, or an arrangement comprising one or more permanent magnets, or a multi-pole magnet) rotatable about a longitudinal axis <NUM>, for example as part of a rotor.

The magnetic field generator <NUM> is adapted for providing a first magnetic field vector B1mag to a first magnetic sensor device <NUM>, and a second magnetic field vector B2mag to a second magnetic sensor device <NUM>. The second magnetic field vector B2mag (e.g. expressed in absolute coordinates) is different from the first magnetic field vector B1mag, in magnitude and/or orientation and/or direction, preferably for all angular positions α of the magnetic field source.

In case of a linear position sensor where the magnetic source moves along a trajectory, e.g. a linear axis, the first and second magnetic sensor device preferably have a fixed distance and a fixed orientation relative to said axis.

In case of an angular position sensor, where the magnetic source is rotatable about a rotation axis, the first and second magnetic sensor device <NUM>, <NUM> have a first and second position which is fixed with respect to a fixed point on the rotation axis, or fixed relative to a centre of the magnetic field generator. The first and second magnetic sensor device <NUM>, <NUM> have a predefined first and second orientation relative to said point or said centre, which orientations are also fixed. The first and second sensor are typically mounted on a stator.

The first sensor device <NUM> is adapted for determining first vector data (e.g. v1x, v1y, v1z in case of a 3D sensor device, or v1x, v1y in case of a 2D sensor device) related to a combination of said first magnetic field vector B1mag and an external disturbance field Bext, if present. The first vector data may be expressed in a first local coordinate system (e.g. X1,Y1,Z1 in case of a 3D sensor, or X1,Y1 in case of a 2D sensor device).

The second sensor device <NUM> is adapted for determining second vector data (e.g. v2x, v2y, v2z in case of a 3D sensor device, or v2x, v2y in case of a 2D sensor device) related to a combination of said second magnetic field vector B2mag and the external disturbance field Bext, if present. The second vector data may be expressed in a second local coordinate system (e.g. X2,Y2,Z2 in case of a 3D sensor, or X2,Y2 in case of a 2D sensor device).

The linear or angular sensor system <NUM>, <NUM> to <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> further comprises at least one processor <NUM>, <NUM>, <NUM> (see e.g. <FIG>) adapted for receiving the first (raw uncorrected) vector data, e.g. (v1x, v1y, v1z) or (v1x, v1y) and the second vector data, e.g. (v2x, v2y, v2z) or (v2x, v2y), and adapted for determining a linear or an angular position of the magnetic field generator <NUM> based on the first vector data and the second vector data in a manner which substantially completely eliminates the external disturbance field Bext, even if a magnitude of the external disturbance field is in the same order as the field generated by the magnetic field generator, for example has a magnitude larger than <NUM>% or larger than <NUM>% of the magnitude of the magnetic field generated by the magnetic field generator.

In contrast to the system described in <FIG>, where each sensor device merely provides an angle (which is a numerical value), each of the sensor devices <NUM>, <NUM> of a system according to the present invention is capable of measuring and/or providing 2D or 3D vector information, meaning for example the X and Y coordinates of a projection of the magnetic field vector in the plane defined by the sensor device, or the X and Y and Z coordinates of the magnetic field vector measured by the sensor device. This is an important difference with the system shown in <FIG> where two sensors are used which are only capable of providing an angle, not a vector. At least one of the sensor devices <NUM>, <NUM> is capable of outputting this vector information, e.g. by providing the vector information it has measured or determined to the other sensor device, e.g. via a serial bus <NUM> (see <FIG>) or via a parallel bus interconnecting the two sensor devices.

In an embodiment one of the sensor devices (e.g. the first sensor device <NUM>) provides its vector information to the other (e.g. the second sensor device <NUM>), in which case a processor <NUM> in the second sensor device <NUM> will calculate the linear position x or angular position α of the magnetic source <NUM> based on the first vector information measured by and received from the first sensor device <NUM>, and based on the second vector information measured by the second sensor device <NUM>.

In an embodiment, both sensor devices <NUM>, <NUM> provide their vector information to the other sensor device, and a first processor <NUM> in the first sensor device <NUM> and a second processor <NUM> in the second sensor device <NUM> both calculate said linear or angular position. This can be used for redundancy reasons or for fault detection.

In another or a further embodiment, both sensor devices <NUM>, <NUM> provide their vector information to an external processor <NUM>, for example to an on-board computing device, which then calculates said linear or angular position.

The vector information may be provided e.g. in the form of Cartesian coordinates (e.g. an X-coordinate and a Y-coordinate, or an X and Y and Z coordinate), or in the form of an amplitude and an angle (in case of a 2D sensor device) or in the form of an amplitude and two angles (in case of a 3D sensor device), but other coordinate systems such as for example cylindrical coordinates (Radius, Angle, Height), or spherical coordinates (Radius, angle1, angle2) may also be used.

Rather than relying on approximations (as is done in <CIT>), the inventors of the present invention found an improved algorithm for determining the angular position of the magnetic field source <NUM>, which is based on several insights. It is a major advantage that the improved algorithm allows to determine the linear or angular position of the magnetic source <NUM> relative to the sensors, even if the external disturbance field is relatively large (e.g. has an amplitude as large as that of the magnetic field source), and irrespective of the orientation of the external disturbance field Bext. In other words, it is a major advantage that this method is "truly robust" to an external disturbance field.

One of the underlying ideas of the present invention is based on the insight that each sensor can measure a vector relative to its own local coordinate system, but since the relative positions and orientations of the two sensors is fixed, and is known, e.g. is predetermined by design (within some tolerance margins), or is measured after mounting, e.g. during a calibration test, the vector information obtained by the first and second sensor device, are related.

Another underlying idea of the present invention is based on the insight that the external disturbance field at the location of the first sensor device is substantially the same as the external disturbance field at the location of the second sensor device.

Yet another underlying idea of the present invention is based on the insight that the first magnetic vector measured by the first sensor device is the vector sum of the first magnetic field vector B1mag provided by the magnetic field source and a disturbance field vector Bext, and that the second magnetic vector measured by the second sensor device is the vector sum of the second magnetic field vector B2mag provided by the magnetic field source and the same disturbance field vector Bext.

Yet another underlying idea of the present invention is based on the insight that there is a relation between the first magnetic field vector B1mag created by, or originating from the magnetic field source and the second magnetic field vector B2mag created by, or originating from the magnetic field source, e.g. permanent magnet, which relation is known, e.g. is predetermined by design, or can be measured, e.g. during a calibration test. There are many arrangements possible where this relation can be expressed by means of a set of linear equations, which can first be solved to eliminate the external field, and the remaining equations can then be used to calculate the linear or angular position, e.g. using a goniometric function. It is a major advantage that the external disturbance field can be eliminated, e.g. completely eliminated by the set of linear equations.

Yet another underlying idea of the present invention is based on the insight that by measuring a sufficient number of field components, and by combining all the information from only two sensor devices, the (unknown) field components of the external disturbance field, as well as the unknown linear or angular position of the magnet, can be determined by solving a set of equations.

It is explicitly pointed out that the combination of all these insights is required to come to the solution provided by the present invention.

In the rest of this document, the principles of the present invention will be described for several exemplary arrangements, both simple arrangements as well as more complex arrangements, and several algorithms will be described to determine the linear or angular position of the magnetic source (e.g. relative to a reference position). Each version has its merits in terms of reduced complexity of the algorithm versus less stringent mounting requirements, but all versions are robust against an external disturbance field.

First (in <FIG>) arrangements with many mounting constraints will be described, because methods to calculate the angular position is easy to understand. In these systems, both sensor devices can be 2D sensor devices capable of measuring magnetic field components in only two dimensions. Next, (in <FIG>) more general arrangements are described, with relaxed mounting requirements, but requiring a more complex method to determine the angular position. In these systems one or both of the sensor devices needs to be a 3D sensor device. In <FIG> another example of a 2D sensor system will be described. Finally, in <FIG> other specific embodiments will be described.

<FIG> is a replica of <FIG> of <CIT>, and shows a sensor system known in the art, comprising a permanent magnet <NUM> and a first "angle sensor device" <NUM> adapted for providing a first angle ϕ1, and a second angle sensor device <NUM> adapted for providing a second angle ϕ2 respectively. It is pointed out that these devices only provide an angle, and do not provide vector information.

<FIG> is a replica of <FIG> of <CIT>, and shows a first angle ϕ1 measured by the first sensor device <NUM>, and a second angle ϕ2 measured by the second sensor device <NUM>, in the presence of a disturbance field Bd. It is described in US'<NUM> that, in case the disturbance field Bd is more than <NUM> times smaller than the field of the magnet Bm1, Bm2, a combination of the angles ϕ1 and ϕ2 can provide an angle with a reduced error caused by the disturbance field.

The inventors of the present invention also considered the arrangement of <FIG>, and the problem of determining the angular position of the magnet <NUM> relative to the sensors <NUM>, <NUM> in the presence of the external disturbance field Bd, but found another solution for addressing this problem. The solution proposed herein is capable of drastically reducing, or even completely eliminating the influence of the external field, irrespective of the direction of the external disturbance field, even if the amplitude of the disturbance field is up to about <NUM>% or up to about <NUM>% or up to about <NUM>%, or up to about <NUM>% or up to about <NUM>% or even as large as that of the magnetic field generator, e.g. permanent magnet.

While the present invention is not limited to a permanent magnet as the only possible magnetic field generator, for ease of description, the principles of the present invention will be explained for a permanent magnet. Likewise, while the present invention is not limited to sensor devices with Cartesian coordinate systems, the principles of the present invention will be explained assuming Cartesian coordinate systems. The skilled person having the benefit of the present disclosure can easily extend the principles provided by the present invention to other magnetic sources and/or other coordinate systems.

<FIG> shows an abstract representation of an exemplary arrangement <NUM>, for which the inventors wanted to determine the angular position α of the magnet <NUM> (e.g. mounted to a rotor, not shown) relative to a reference angle. The two sensor devices <NUM>, <NUM> are arranged in a fixed position and orientation, for example to a stator (not explicitly shown).

The permanent magnet <NUM> is rotatable about an axis <NUM>, to define an angle α relative to a reference position.

Based on the insights mentioned above, the inventors of the present invention realised that the system <NUM> depicted in <FIG> can be described mathematically by a set of four simultaneous equations in six unknowns, illustrated in <FIG>, where (v1x, v1y) are the vector coordinates of the first total magnetic field B1mag in the first plane ω1, measured by the first sensor device <NUM>, expressed relative to the X1 and Y1 axis, and where (v2x, v2y) are the vector coordinates of the second total magnetic field B2mag in the second plane ω2, measured by the second sensor device <NUM>, expressed relative to the X2 and Y2 axis.

It is well known in the art that a set of <NUM> linear equations with <NUM> unknowns does not have a unique solution. Hence, at first sight, the problem seems unsolvable.

However, after investigating the arrangement of <FIG> more closely, the inventors came to the insight that, in case a first distance d1 between the magnet <NUM> and the first sensor <NUM>, and a second distance d2 between the magnet <NUM> and the second sensor <NUM> are identical, (i.e. in case d1=d2 and the magnet is equally strong at the top and the bottom), then the magnitude |B1mag| of the first vector provided by the magnet is equal to the magnitude |B2mag| of the second vector provided by the magnet, in which case formula [<NUM>] and [<NUM>] of <FIG> apply. (In fact, these equations also apply for a magnet which is stronger at the top than at the bottom, or vice versa, if d1 and d2 are appropriately chosen).

Combining the formulas [<NUM>] and [<NUM>] of <FIG> with the set of equations [<NUM>] to [<NUM>] of <FIG>, yields the set of four linear equations [<NUM>] to [<NUM>] in four unknowns (B1magx, B1magy, Bextx, Bexty), which has a unique solution, which can be determined for example as worked out further.

Formula [<NUM>] shows that the magnetic field B1mag created by the magnet at the location of the first sensor <NUM> can be obtained by determining the vector difference between the first total vector and the second total vector, divided by <NUM>.

This is illustrated graphically in <FIG> for two exemplary orientations of the magnet, for a fixed orientation of the external disturbance field Bext, to illustrate in fact that this method works for any orientation of the external disturbance field, even if the magnitude of said external external field is about as large as the magnitude of the magnetic field created by the magnet.

<FIG> shows that the first sensor <NUM> would measure B1tot, being the vector sum of B1mag provided by the magnet, and the external disturbance field Bext.

<FIG> shows that the second sensor <NUM> would measure B2tot being the vector sum of B2mag provided by the magnet, and the external disturbance field Bext.

<FIG> illustrates that, for the specific arrangement shown in <FIG>, the vector difference B1tot - B2tot corresponds to <NUM>*B1mag, and thus that B1mag can be calculated as (B1tot - B2tot)/<NUM>, where the external disturbance field Bext is completely eliminated. This is a completely different teaching than the one provided by US'<NUM>.

<FIG> show the similar situation as in <FIG>, for the same external field Bext, when the magnet is rotated clockwise over about <NUM>°. As can be seen, the same formulas apply, irrespective of the size and orientation of Bext relative to the magnet.

Referring back to <FIG>, once the vector position (B1magx, B1magy) is known, the angular position α of the magnet <NUM> can be calculated. For example, in case the B1magx and B1magy values vary substantially like a cosine and sine signal, the angular position can be calculated using formula [<NUM>], or can be calculated using a look-up table optionally using linear interpolation, or can be calculated in other manners known per se in the art.

As can be appreciated from formula [<NUM>] to [<NUM>], the algorithm <NUM> described above needs the vector coordinates (v1x, v1y) of the total projected field measured by the first sensor device <NUM>, and the vector coordinates (v2x, v2y) of the total projected field measured by the second sensor device <NUM>. The algorithm can be executed for example by a processor <NUM> (see <FIG>) embedded in the first sensor device <NUM>, in which case the first and second sensor device <NUM>, <NUM> would need to be interconnected and adapted such that the second sensor <NUM> can provide the second vector information to the first sensor device <NUM>, or vice versa. The first sensor device <NUM> can then calculate the angular position α of the magnet as if the external disturbance field Bext was not there. In an automotive application, the processor <NUM> may communicate this angle α to an on-board computer and/or to other devices for further processing, for example for actuating a steering wheel or the like, but such aspects are outside the scope of the present invention.

In an embodiment, both sensor devices <NUM>, <NUM> have an embedded processor <NUM>, <NUM>, and both sensor devices are adapted for providing its vector information to the other sensor device, and both sensor devices are adapted for calculating the angular position α (which is compensated for the external disturbance field) by performing the algorithm <NUM> described above, and both devices are adapted for providing this angle to said on-board computer or other device. In this way, a fault condition may be detected, since both values should be identical.

In yet another embodiment, the algorithm <NUM> is not performed by a processor <NUM>, <NUM> embedded inside the sensor devices <NUM>, <NUM>, but is performed by a processor <NUM> external to the sensor devices, for example in the example above, by said on-board computer. In this case, each of the sensor devices would be adapted to provide its vector information to said board computer, for example via leads or wires <NUM> or cables or wireless (e.g. optical or via RF), or in any other suitable way. Of course separate leads or tracks or wires or cables may also be provided between the sensor devices and the external processor <NUM>.

But the inventors went one step further, and realized that the set of equations [<NUM>] to [<NUM>] can also be solved if the magnetic field vectors B1mag and B2mag are not parallel or anti-parallel, and/or if the orientation of the first and second sensor device <NUM>, <NUM> is not perfectly aligned (e.g. if X1 is not parallel with X2 and Y1 is not parallel with Y2).

<FIG> shows several variants of the arrangement of <FIG>. It is noted that in <FIG> the sensor devices are not explicitly shown (but a cross is shown instead), and the coordinate axes have been shifted somewhat, in order to keep the drawings readable. As can be seen, in the embodiments shown in <FIG> tot <FIG> the first plane ω1 of the first sensor device <NUM> and the second plane ω2 of the second sensor device <NUM> are still parallel to each other and perpendicular to the rotation axis <NUM>.

For simplifying the description, it is assumed in the drawings of <FIG> that the magnet is symmetrical in the sense that the field strength at a certain distance from the top of the magnet is as large as the field strength at the same distance from the bottom of the magnet. Thus, in the examples of <FIG>, d1=d2 actually means that the magnitude of |B1mag| is equal to the magnitude of |B2mag|, and d1<>d2 actually means that the magnitude of |B1mag| is different from the magnitude of |B2mag|.

In <FIG> the sensor devices are located on opposite sides of the magnet, and.

In <FIG> the sensor devices are located on the same side of the magnet, and.

Considering the arrangement of <FIG>, the inventors came to the further insight that also in this case, there is a simple relation between the field B1mag created by the magnet at the first sensor position and the field B2mag created by the magnet at the second sensor position, which can be mathematically expressed by the formulas [<NUM>] and [<NUM>] shown in <FIG>, where "k" is a constant floating point number which can be determined by calibration.

In the example of <FIG> the value of "k" will typically be negative. In the example of <FIG>, the value of "k" will typically be positive. It can be seen that the formulas [<NUM>] and [<NUM>] are a special case of the formulas [<NUM>] and [<NUM>] for the value k = -<NUM>.

Combining the formulas [<NUM>] and [<NUM>] with the set of equations [<NUM>] to [<NUM>] yields the set of four linear equations [<NUM>] to [<NUM>] in four unknowns (B1magx, B1magy, Bextx, Bexty), which has a unique solution, as can be appreciated from formula [<NUM>] and formula [<NUM>].

Similar as above, once the vector position (B1magx, B1magy) is known, the angular position α of the magnet <NUM> (e.g. relative to a reference position, or e.g. relative to a stator) can be calculated, for example using the formula [<NUM>] if B1magx and B1magy vary like a cosine and sine function respectively, or using a look-up table (optionally with linear interpolation), or in any other suitable way.

Compared to the special case of <FIG>, the embodiments of <FIG> offer the advantage that the distance d1 and d2 need not be exactly the same, and/or that the strength of the magnetisation does not need to be exactly the same at the top and the bottom of the magnet, which reduces the mounting requirements. This may also help to improve accuracy in case the magnet is not symmetrically magnetized, but is somewhat stronger at the top and somewhat weaker at the bottom, or vice versa.

Considering the arrangement of <FIG>, the inventors came to the further insight that there is also a relation between the first field vector B1mag and Bext measured by the first sensor device <NUM> and expressed in terms of the first coordinate system X1,Y1,Z1 on the one hand, and the second field vector B2mag and Bext measured by the second sensor device <NUM> and expressed in terms of the second coordinate system X2,Y2,Z2 on the other hand, which can be mathematically expressed by the formulas [<NUM>] and [<NUM>] shown in <FIG>, and similar formulas (not shown) for the external disturbance field, where m, n, p, q, r, s are constant floating point numbers which are predetermined by design, or can be determined by calibration.

It is pointed out that in some embodiments of the present invention, some of the values m, n, p, q, r and s may be equal to zero. In some embodiments of the present invention, one or both of the values "p" and "s" is non-zero, which allows to take into account further mounting anomalies and/or some non-ideal magnetization, or combinations hereof.

It can be understood that the formulas [<NUM>] and [<NUM>] are a special case of the formulas [<NUM>] and [<NUM>] for the case where m=r=k and n=q=s=<NUM>.

Combining the formulas [<NUM>] and [<NUM>] with the set of equations [<NUM>] to [<NUM>] yields the set of four linear equations [<NUM>] to [<NUM>] in four unknowns (B1magx, B1magy, Bextx, Bexty), which has a unique solution.

Similar as above, once the vector position (B1magx, B1magy) is known, the angular position α of the magnet <NUM> can be calculated, for example by using the formula [<NUM>], or using a look-up table optionally with linear interpolation, or in any other suitable way.

As compared to the special case of <FIG>, the embodiments of <FIG> offer the advantage that the field strength at top and bottom and/or the distance d1 and d2 need not be the same, and also the orientation of the sensor devices <NUM>, <NUM> need not be exactly the same (but can be rotated over an angle β), which reduces the mounting requirements even further, and/or may increase the accuracy of the angular position system even further.

It is noted that, in all of the embodiments described in <FIG>, also the values of Bextx and Bexty may be calculated, which may be used for diagnostic purposes, but that is not absolutely required for determining the angular position α of the magnet (e.g. mounted on a rotor).

<FIG> shows a block-diagram of an exemplary embodiment of a first and second sensor device <NUM>, <NUM> which are interconnected via leads or wires, e.g. via a serial bus <NUM>. The bus <NUM> may also be interconnected to other devices, e.g. to an external processor <NUM>.

In the example shown, each of the first and second sensor <NUM>, <NUM> has a processor <NUM>, <NUM>, e.g. in the form of a programmable microcontroller, one or both of which may be adapted for performing said algorithm <NUM> or <NUM> or <NUM>. The algorithm may be stored as a set of executable instructions in a memory connected to said processor.

The working of magnetic sensor devices is well known in the art, and hence need not be explained in further detail. It suffices to understand the present invention that each sensor device preferably contains at least three magnetic sensitive elements, e.g. in the form of Hall plates or magneto-resistive elements, which are not collinear, and thus define a plane. Furthermore, each sensor device is capable of determining a 2D or 3D vector of a (total) magnetic field relative to the sensor device, and at least one of the sensor devices <NUM>, <NUM> is adapted for providing the measured vector to the other sensor device.

Alternatively, the algorithm <NUM>, <NUM>, <NUM> of calculating the angular position α of the magnet is performed by the external processor <NUM>, in which case the first sensor device will provide first 2D or 3D vector information to the external processor, and the second sensor device will provide second 2D or 3D vector information to the external processor <NUM>, based on which the external processor can calculate the angular position α, for example using any of the algorithms described above.

But the inventors went still further, and came to the insight that it is not absolutely required that the first and second sensor device are located on the rotation axis <NUM>, and/or that the first and second plane ω1, ω2 defined by the sensor devices are parallel to one another and perpendicular to the rotation axis. While it is true that such arrangements can simplify the equations, and allow that two-dimensional sensor devices are used, the underlying ideas of the present invention can be broadened.

In other words, the arrangements of <FIG> and <FIG> illustrate the relatively simple case where the sensor devices are 2D devices, which only need to measure an in-field vector because the two planes are parallel, but in case the sensor devices can measure a 3D vector, the limitation of parallel planes is no longer required. In addition, also the requirement that the first magnetic field vector B1mag and the second magnetic field vector B2mag are parallel or anti-parallel, and/or that the first and second magnetic field vector need to have a magnitude with a constant ratio for all angular positions, can be omitted.

<FIG> shows a more general arrangement of an angular position system <NUM>, where the first and second sensor device <NUM>, <NUM> may or may not be located on the rotation axis <NUM>, and where the planes ω1, ω2 of the first and second sensor device may or may not be parallel, and where the planes of the sensor devices may or may not be perpendicular to the rotation axis <NUM>, and where none or only one or all three of the axes X1, Y1, Z1 and X2, Y2, Z2 of the sensor devices may or may not be aligned.

More in particular, <FIG> shows an arrangement of a magnetic source <NUM> and a first and a second sensor device <NUM>, <NUM>, with an indication of their respective coordinate systems X1,Y1,Z1 and X2,Y2,Z2, which in the example of FIG. <NUM>(a) assume arbitrary orientations.

<FIG> shows a set of formulas and equations underlying an algorithm or method <NUM>, as may be used to determine an angular position of the magnet of the arrangement shown in <FIG>.

In formulas [<NUM>] to [<NUM>] the components B2magx, B2magy, B2magz of the second magnetic field vector B2mag generated by the magnetic field source at the second sensor location is expressed as a function of the components B1magx, B1magy, B1magz of the first magnetic field vector B1mag generated by the magnetic field source at the first sensor location, for a given arrangement, meaning, for a given fixed position and orientation of the sensor devices and the magnetic source.

As the external disturbance field Bext is assumed to be constant, formulas [<NUM>] to [<NUM>] express that the external field components Bextx2, Bexty2, Bextz2 measured by the second sensor device can be calculated as a linear combination of the external field components Bextx1, Bexty1, Bextz1. This can also be written in matrix-notation using two 3x1 matrices, and a 3x3 transformation matrix. The values "a" to "i" are known floating point numbers, e.g. predetermined by design, or determined by simulation or by calibration, or in any other way.

Formulas [<NUM>] to [<NUM>] are similar to formulas [<NUM>] to [<NUM>] extended to three dimensions.

Formulas [<NUM>] to [<NUM>] are similar to formulas [<NUM>] to [<NUM>] extended to three dimensions, and then combined with formulas [<NUM>] to [<NUM>].

The set of formulas [<NUM>] to [<NUM>] forms a set of <NUM> equations in <NUM> unknowns (B1magx, B1magy, B1magz, Bextx, Bexty, Bextz) expressed in the first coordinate system, where the functions f1, f2 and f3 and the values "a" to "i" are known, e.g. by design or by simulation or by calibration, or combinations hereof. This set of equations has a single solution for B1magx, B1magy and B1mayz, from which the angular position α can be derived, for example using a lookup-table.

While the formulas of <FIG> are theoretically correct, and demonstrate or at least make plausible that the angular position can be found in a manner that completely eliminates the external field, this formulation may not be easy in practice.

<FIG> shows another set of formulas and equations underlying an algorithm or method <NUM>, as may be used to determine an angular position α of the magnetic source <NUM> of the arrangement shown in <FIG>.

In formulas [<NUM>] to [<NUM>] the X, Y and Z components of the first magnetic field vector B1mag generated by the magnetic field source at the first sensor location are expressed as functions of the angular position α, and in formulas [<NUM>] to [<NUM>] the X, Y and Z components of the second magnetic field vector B2mag generated by the magnetic field source <NUM> at the second sensor location are expressed as functions of the angular position α. The functions g1 to g6 are known, e.g. by design or by simulation, or can be determined during a calibration test.

The formulas [<NUM>] to [<NUM>] as described in <FIG>, are still applicable, allowing to express the external disturbance field components measured by the second sensor device to be expressed as a linear combination of the external disturbance field components measured by the first sensor device. As mentioned above, the values "a" to "i" are floating point numbers, which are known.

The values of the functions g1 to g6 may be determined for a plurality of values of α, and then stored in a non-volatile memory <NUM>, <NUM>, <NUM> of the device (see <FIG>), optionally in a compressed manner. The values of "a" to "i" would also be stored in said memory.

Formulas [<NUM>] to [<NUM>] are similar to formulas [<NUM>] to [<NUM>] extended to three dimensions, and then combined with formulas [<NUM>] to [<NUM>] and formulas [<NUM>] to [<NUM>], resulting in a set of <NUM> equations with <NUM> unknowns α, Bextx1, Bexty1, Bextz1.

This is an overspecified set of equations which has a single solution, from which the angular position α can be calculated in known manners, for example using an iterative process.

In a variant of the system shown in <FIG>, and the method <NUM> of <FIG>, the first sensor device <NUM> is a 3D device, and the second sensor device <NUM> is a 2D device, and the set of equations is a subset of the set of equations shown in <FIG>, where equation [<NUM>] and equation [<NUM>] are omitted, and where V1x, V1y, V1z, V2x, V2y are measured, resulting in a set of <NUM> equations with <NUM> unknowns. This is an overspecified set of equations which has a single solution, from which the angular position α can be calculated in known manners, for example using an iterative process.

Other variants are also contemplated, e.g. where the position and/or the orientation of one or both of the sensor devices is "special".

<FIG> shows an exemplary arrangement of a magnetic source and two sensor devices, which can be seen as a special case of <FIG>, where the sensor devices <NUM>, <NUM> define a first and a second plane ω1, ω2 which are oriented orthogonally with respect to each other. In the example shown in <FIG>, the X2 axis of the second sensor is aligned with the X1 axis of the first sensor, Y2 is aligned to Z1 and Z2 is aligned to -Y1.

<FIG> shows a set of formulas and equations underlying an algorithm or method <NUM>, as may be used to determine an angular position of the magnet source of the arrangements shown in <FIG>. By setting the values a=+<NUM>, f=+<NUM>, h=-<NUM>, and b=c=d=e=g=i=<NUM> in equation [<NUM>] to [<NUM>], the set of equations [<NUM>] to [<NUM>] can be obtained. The values of the external field components can be eliminated from this set of equations, for example as shown by the set of equations [<NUM>] to [<NUM>], resulting in a set of <NUM> equations in <NUM> variable α.

In a variant of the system of <FIG> and the method <NUM> of <FIG>, the first sensor device <NUM> is a 3D device, and the second sensor device <NUM> is a 2D device, and the set of equations is a subset of the set of equations shown in <FIG>, where equation [<NUM>] and equation [<NUM>] are omitted, and where V1x, V1y, V1z, V2x, V2y are measured, resulting in a set of <NUM> equations with <NUM> unknown. This is an overspecified set of equations which has a single solution, from which the angular position α can be calculated in known manners, for example using an iterative process.

<FIG> shows an exemplary arrangement of a magnetic source <NUM> and two sensor devices <NUM>, <NUM>, which can be seen as another special case of <FIG>, where the sensor devices <NUM>, <NUM> define a first and a second plane ω1, ω2 which are oriented parallel with respect to each other. In the example shown in <FIG>, the first coordinate system X1,Y1,Z1 is fully aligned with the second coordinate system X2,Y2,Z2. The two planes may even be a single plane, for example a single PCB, although that is not absolutely required.

<FIG> shows a set of formulas and equations underlying an algorithm or method <NUM>, as may be used to determine an angular position of the magnet source of the arrangement shown in <FIG>. By setting the values a=+<NUM>, e=+<NUM>, i=+<NUM>, and b=c=d=f=g=h=<NUM> in equation [<NUM>] to [<NUM>], the set of equations [<NUM>] to [<NUM>] can be obtained. The values of the external field components can be eliminated from this set of equations, for example as shown by the set of equations [<NUM>] to [<NUM>], resulting in a set of <NUM> equations in <NUM> variable α.

Many specific arrangements are possible, for example, in a particular embodiment, the magnet is a two pole disk magnet or a two pole ring magnet, and one of the sensors is located on the rotation axis <NUM>, and the other sensor device is arranged in the plane of the ring or disk magnet, radially outside the ring or disk. In other embodiments, the magnet is a multi-pole disk magnet or a multi-pole ring magnet, having at least four poles, or at least six poles.

<FIG> shows another exemplary sensor arrangement <NUM> comprising a multi-pole magnetic source (e.g. an eight-pole ring magnet) and two 2D-sensor devices arranged on a single side of the magnet, for example facing the upper surface or facing the bottom surface. <FIG> shows a bottom view, <FIG> shows a front view of the sensor arrangement. The ring magnet may be axially magnetized (i.e. in the Z-direction).

The sensor devices <NUM>, <NUM> are aligned such that their respective axes X1 and X2, and Z1 and Z2 are oriented parallel. The two sensor devices <NUM>, <NUM> are spaced apart over "one pole distance", hence the signals measured by the two devices are substantially <NUM>° phase shifted (in the absence of a disturbance field). This requires an accurate positioning of the sensor devices <NUM>, <NUM> relative to the magnet. It is pointed out, however, that a single printed circuit board (PCB) <NUM> having particular dimensions may be used with magnets having various sizes, by a proper positioning of the PCB relative to the sensor axis <NUM>. Indeed, the angular distance between the two sensor devices as seen from the axis <NUM> can be increased by mounting the PCB closer to the rotation axis, or can be decreased by mounting the PCB further away from the axis <NUM>.

In an embodiment, the first sensor device <NUM> measures an in-plane field component Bx1 and an out-of-plane field component Bz1, and the second sensor device measures an in-plane field component Bx2 and an out-of-plane field component Bz2, and formulas similar to those of <FIG> are used to calculate the relative angular position, namely: <MAT> <MAT> because sensor1 and sensor2 are spaced substantially over one pole distance,.

The Bx and Bz field components of the magnetic field measured at the sensor locations as shown are substantially <NUM>° phase shifted, hence: <MAT> <MAT> Then: <MAT> And: <MAT>.

Instead of an arctangent function, a look-up table, optionally with interpolation can be used to determine the angular position.

Each sensor device may comprise for example one Horizontal Hall element (to measure the Bz component) and one vertical Hall element (to measure the Bx-component), but the present invention is not limited thereto, and other sensors can also be used.

In another example, the sensor devices may comprise two horizontal Hall elements arranged on opposite sides of a circular integrated magnetic concentrator (IMC). The Bz component can then be determined by calculating the sum of the two signals obtained from the Hall elements, and the Bx component can be determined by calculating the difference of the two signals obtained from the Hall elements.

In a variant of <FIG>, the ring magnet <NUM> is replaced by a disk magnet.

The inventors surprisingly found that it is actually not required that the sensors are located at one pole distance for receiving <NUM>° phase shifted signals originating from the magnet, but the invention also works for distances in the range from about <NUM> to about <NUM> pole distances, or from about <NUM> to about <NUM> pole distances, the latter corresponding to a phase shift from about <NUM>° to about <NUM>°. The signal amplitude (hence the SNR) is largest for <NUM>° phase shift, but does not dramatically decrease for other distances. Even more surprisingly, exactly the same formulas as above are applicable. This offers the advantage that the mounting tolerances of the PCB can be drastically relaxed. Depending on the distance between the sensor devices, the angular offset position relative to the "zero position" will vary. In some applications (e.g. where the angular speed is determined as the time derivate of the angular position), the this offset is irrelevant. In other applications, where the offset is important, a precise position can be obtained e.g. by accurate positioning of the PCB (without having to perform a calibration test), and/or by performing a calibration test. In the latter case, the mounting requirements can be drastically reduced.

<FIG> shows another exemplary arrangement comprising a multi-pole magnetic source (e.g. an eight-pole ring magnet, or a ring magnet with more than eight poles) and two 2D or 3D-sensor devices arranged so as to face an outer perimeter or outer circumference of the magnet.

The sensor devices <NUM>, <NUM> are aligned such that their respective axes X1 and X2, and Z1 and Z2 are oriented parallel. In the example shown in <FIG>, the two sensor devices <NUM>, <NUM> are spaced apart over "one pole distance", hence the signals measured by the two devices are substantially <NUM>° phase shifted. This requires an accurate positioning of the sensor devices <NUM>, <NUM> relative to the magnet.

As in the embodiment of <FIG>, the first sensor device <NUM> measures an in-plane field component Bx1 and an out-of-plane field component Bz1 at a first position, and the second sensor device measures an in-plane field component Bx2 and an out-of-plane field component Bz2 at a second position, and the same formulas [<NUM>] to [<NUM>] are also applicable here.

The inventors surprisingly found that also in this case, it is not required to position the two sensor devices at one pole distance, and the invention will also work for other distances, e.g. a distance in the range from <NUM> to <NUM> pole distances or from <NUM> to <NUM> pole distances, or from <NUM> to <NUM> pole distances. The same comments as mentioned above for <FIG> (e.g. with respect to the formulas, the SNR, accurate position versus calibration, and offset position)are also applicable here.

<FIG> shows another exemplary arrangement comprising a multi-pole magnetic source (e.g. an eight-pole ring magnet, or a ring magnet with less than eight, or more than eight poles, e.g. only four poles or only six poles, or ten poles, etc), and two 2D or 3D-sensor devices arranged so as to face an inner perimeter of the ring magnet. In other words, the sensor chips are arranged in the central opening of the magnet.

The two sensor devices <NUM>, <NUM> are aligned such that their respective axes X1 and X2, and Z1 and Z2 are oriented parallel. The two sensor devices <NUM>, <NUM> are spaced apart over "one pole distance", hence the signals measured by the two devices are substantially <NUM>° phase shifted. This requires an accurate positioning of the sensor devices <NUM>, <NUM> relative to the magnet.

As in the embodiment of <FIG> and <FIG>, the first sensor device <NUM> measures an in-plane field component Bx1 and an out-of-plane field component Bz1 at a first position, and the second sensor device measures an in-plane field component Bx2 and an out-of-plane field component Bz2 at a second position, and the same formulas [<NUM>] to [<NUM>] are also applicable here.

It is an advantage of the sensor system of <FIG> that the sensor devices can be arranged closer together, and may even be integrated in a single package.

The inventors surprisingly found that also in this case, it is not required to position the two sensor devices at one pole distance, and the invention will also work for other distances, with the same formulas. The same comments as mentioned above for <FIG> and <FIG> are also applicable here.

While this document has described mainly angular position sensors, the present invention is directed to linear position sensors, for example as illustrated in <FIG>.

<FIG> shows a linear position sensor system <NUM> which can be seen as a variant of the angular position sensor system <NUM> of <FIG>, or as a variant of the system <NUM> shown in <FIG>. The same formulas are applicable, but the "angular value" calculated would have to be converted to a linear distance value, e.g. using a predefined constant. The same or similar comments as mentioned above for <FIG> are also applicable here, mutatis mutandis.

In the example of <FIG>, the magnetic structure is magnetized in a direction parallel to the plane o the sensor device, namely in the Y-direction. The sensor devices may measure a Bx and a By component at a first and a second location. That means, the sensor device may measure two in-plane field components, parallel to the substrate of the sensor devices.

<FIG> shows a linear position sensor system <NUM> which can be seen as a variant of the angular sensor system <NUM> of <FIG>, or as a variant of the sensor system <NUM> of <FIG>.

In the example of <FIG>, the magnetic structure is magnetized in a direction perpendicular to the plane o the sensor device, namely in the Z-direction. The sensor devices may measure a Bx and a Bz magnetic field component at a first and a second location. That means, the sensor device may measure an in-plane field component parallel to the substrate and an out-of-plane magnetic field component perpendicular to the substrate.

Claim 1:
A linear position sensor system (<NUM>; <NUM>) comprising:
- a magnetic field generator (<NUM>) movable relative to a first and a second magnetic sensor (<NUM>, <NUM>) or vice versa, and being adapted for providing a first magnetic field vector (B1mag) to the first magnetic sensor (<NUM>) and for providing a second magnetic field vector (B2mag) different from the first magnetic field vector, to the second magnetic sensor (<NUM>);
- the first magnetic sensor (<NUM>) being adapted for determining first vector data (v1x, v1y; v1x, v1z) related to a combination of said first magnetic field vector (B1mag) and an external disturbance field (Bext), if present;
- the second magnetic sensor (<NUM>) being adapted for determining second vector data (v2x, v2y; v2x, v2z) related to a combination of said second magnetic field vector (B2mag) and said external disturbance field (Bext), if present;
- the position sensor system further comprising at least one processor (<NUM>, <NUM>, <NUM>) adapted for receiving the first vector data (v1x, v1y; v1x, v1z) and the second vector data (v2x, v2y; v2x, v2z), and adapted for performing a method (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) of determining a position of the magnetic field generator (<NUM>) relative to the first and second magnetic sensor (<NUM>; <NUM>), which is based on the first vector data and the second vector data in a manner which eliminates the external disturbance field (Bext);
- wherein the first magnetic sensor (<NUM>) is configured for measuring, at a first sensor position, a first magnetic field component (B1x) oriented in a first direction and a second magnetic field component (B1y; B1z) oriented in a second direction substantially perpendicular to the first direction; and
- wherein the second magnetic sensor (<NUM>) is configured for measuring, at a second sensor position, a third magnetic field component (B2x) oriented in said first direction and a fourth magnetic field component (B2y; B2z) oriented in said second direction;
characterised in that
- the first and the second magnetic sensor (<NUM>; <NUM>) are integrated in a single package;
- the magnetic field generator (<NUM>) is magnetized such that, and the first and the second magnetic sensor (<NUM>, <NUM>) are oriented relative to the magnetic field generator (<NUM>) and are spaced apart such that the first magnetic field component (B1x) is phase shifted relative to the third magnetic field component (B2x) by a value in the range from <NUM>° to <NUM>°.