FIELD OF THE INVENTION

The present invention relates in general to the field of magnetic position sensor devices, methods and systems, and more in particular to a position sensor device, method and system for determining a position over a relatively large range with relatively high accuracy, and to a special magnet or magnetic structure.

BACKGROUND OF THE INVENTION

Magnetic sensor systems, in particular linear position sensor systems and angular position sensor systems are known in the art. They offer the advantage of being able to measure a linear or angular position without making physical contact, thus avoiding problems of mechanical wear, scratches, friction, etc.

Many variants of position sensor systems exist, solving one or more of the following requirements: using a simple or cheap magnetic structure, using a simple or cheap sensor device, being able to measure over a relatively large range, being able to measure with great accuracy, requiring only simple arithmetic, being able to measure at high speed, being highly robust against positioning errors, being highly robust against an external disturbance field, providing redundancy, being able to detect an error, being able to detect and correct an error, having a good signal-to-noise ratio (SNR), etc.

Often two or more of these requirements conflict with each other, hence a trade-off needs to be made. A typical example is the trade-off between a large measurement range and high accuracy.

There is always room for improvements or alternatives.

SUMMARY OF THE INVENTION

It is an object of embodiments of the present invention, to provide a position sensor device, and a method of determining a position of a position sensor device relative to a magnetic structure, and to provide a position sensor system comprising such a device and such a magnetic structure, and to a special magnet or magnetic structure for use in such a system.

It is an object of embodiments of the present invention, to provide a position sensor device, method and system for determining a position of a position sensor device relative to a magnetic structure in the form of a permanent magnet structure having a plurality of poles, e.g. a plurality of alternating poles.

It is also an object of embodiments of the present invention to provide a magnetic structure and a position sensor device which can be used in such a position sensor system.

It is a particular object of embodiments of the present invention, to provide a position sensor system having a relatively large measurement range and a relatively high accuracy, and to a method of determining a position having the same properties.

It is an object of embodiments of the present invention, to provide a position sensor device, and method and system that is substantially insensitive to an external disturbance field.

It is an object of embodiments of the present invention, to provide a position sensor system and method which requires only relatively simple arithmetic (such as for example addition, subtraction, multiplication, division, a look-up table, interpolation) that can be performed on a simple micro-controller, but not including a Discrete Fourier-Transform (DFT) or Fast Fourier Transform (FFT) which typically requires a Digital Signal Processor (DSP) with a Multiply-Accumulate-instruction, and typically also requires considerably more random-access-memory (RAM).

It is an object of embodiments of the present invention, to provide a position sensor device, method and system using one or more permanent magnets, where the position determination is substantially robust against demagnetization of said magnet(s).

These objectives are accomplished by a position sensor system, and by a method for determining a position, and by a position sensor device, and by a magnet or magnetic structure according to embodiments of the present invention.

According to a first aspect, the present invention provides a position sensor device for use in a position sensing system wherein the position sensor device is movable relative to a magnetic structure having a plurality of poles, the position sensor device comprising: a semiconductor substrate; at least three sensors (e.g. S1, S2, S3) for measuring at least three first magnetic field components (e.g. Bx1, Bx2, Bx3), also referred to herein as “in-plane magnetic field components”, oriented in a first direction (e.g. X) substantially parallel to the substrate on at least three different locations (e.g. X1, X2, X3) spaced apart over predefined distances (e.g. Δx12between S1and S2, e.g. Δx23between S2and S3) along the first direction, and for measuring at least three second magnetic field components (e.g. Bz1, Bz2, Bz3), also referred to herein as “out-of-plane magnetic field components”, oriented in a second direction (e.g. Z) oriented substantially perpendicular to the substrate on said at least three different locations (e.g. X1, X2, X3); a processing unit adapted for: a) calculating two first gradients (e.g. ΔBx12/Δx12, ΔBx23/Δx23) of the first magnetic field components (e.g. Bx1, Bx2, Bx3) along the first direction (also referred to herein as “in-plane gradients”); b) calculating two second gradients (e.g. ΔBz12/Δx12, ΔBz23/Δx23) of the second magnetic field components (e.g. Bz1, Bz2, Bz3) along the first direction, (also referred to herein as “out-of-plane gradients”); c) calculating a coarse signal (Sc) based on at least some or all of the first and second gradients; d) calculating a fine signal (Sf) based on at least some of the first and second gradients; e) determining a position (e.g. X, α) based on the coarse signal (Sc) and the fine signal (Sf).

It is noted that the predefined distance Δx12between the first sensor S1and the second sensor S2may be the same as the predefined distance Δx23between the second sensor S2and the third sensor S3, but that is not absolutely required. Different distances can easily be taken into account by appropriate scaling of the respective differences. Preferably the three sensors are equidistant from each other, i.e. Δx12=Δx23.

In case of four sensors, preferably the distance Δx12between the first and second sensor is equal to the distance Δx34between the third and four sensor, but that is not absolutely required. Preferably the four sensors are equidistant from each other, i.e. Δx12=Δx23=Δx34.

The at least three or at least four sensors may be located on a virtual line (collinear), but that is not absolutely required.

The coarse signal is indicative of the relative position in a first range (e.g. in an overall range corresponding to a distance spanned by the plurality of poles). The fine signal is indicative of the relative position in a second range which is a subset of the first range (e.g. in a range corresponding to two adjacent poles).

It is an advantage of this position sensor device that it uses a combination of a coarse signal and a fine signal, because in this way the fine granularity (high accuracy) can be combined with a large range.

It is an advantage of this position sensor device that the position can be determined using a relatively simple controller and does not require a powerful processor, such as a Digital Signal Processor (DSP), because the mathematics required for determining the position can for example be based on basic operations like additions, subtractions, multiplications, divisions, a goniometric function and/or a look-up table, but does not require for example a Discrete Fourier Transform (DFT). It is noted that also the goniometric function itself can be performed using a look-up table, and optional interpolation.

It is a major advantage of this position sensor device that both the fine signal as well as the coarse signal are based on gradient signals, which are insensitive to a (substantially constant) external disturbance field (also referred to as “stray field”), hence also the combined signal is highly insensitive to an external stray field.

It is an advantage of this position sensor device that a rough position indication can be quickly determined based on the coarse signal alone, if required or desired.

It is an advantage that the position of the sensor device relative to the magnetic structure is uniquely defined by the combination of the fine and the coarse signal. This is true even if the coarse signal does not vary strictly monotonically.

It is an advantage of this position sensor device, and of a position sensor system in which this device is used, that the fine signal and the coarse signal contain at least some redundancy, in the sense that they allow to determine an inconsistency between the two signals, or the presence of a relatively (too) large disturbance field. Depending on the application, this information can be used to detect an error condition.

It is an advantage of this position sensor device, and of a position sensor system in which this device is used, that the position of the sensor device relative to the magnetic structure can be uniquely determined without first having to move to a “known position”, e.g. after power-ON.

Preferably the movement trajectory is located in a single plane. Preferably the sensor device comprises a semiconductor substrate which is oriented parallel to said single plane. The at least three in-plane magnetic field components (e.g. Bx1, Bx2, Bx3) are preferably measured in the movement direction (in case of a linear movement trajectory), or tangential to the movement trajectory (in case the movement trajectory is circular or curved). The at least three out-of-plane magnetic field components (e.g. Bz1, Bz2, Bz3) are preferably oriented perpendicular to the semiconductor plane.

The position sensor device is preferably oriented such that the first direction (e.g. X) is oriented in a direction parallel to or tangential to the direction of (relative) movement. Hence the first (or “in-plane”) magnetic field components (e.g. Bx) are parallel or tangential to the direction of relative movement, and the second (or “out-of-plane”) magnetic field components (e.g. Bz) are oriented perpendicular to the direction of (relative) movement.

In an embodiment, the position sensor device comprises at least three sensors (e.g. S1, S2, S3), and is adapted for calculating the coarse signal (Sc) as a function of the two first gradients (e.g. ΔBx12/Δx12, ΔBx23/Δx23) and the two second gradients (e.g. ΔBz12/Δx12, ΔBz23/Δx23).

In an embodiment, the position sensor device comprises at least three sensors (S1, S2, S3), and is adapted for calculating the coarse signal (Sc) based on a linear combination (e.g. a difference) of a first value and a second value (v1, v2), the first value (v1) being a function (e.g. a goniometric function) of the first (in-plane) and second (out-of-plane) gradient of the component signals obtained from the first and second sensor (S1, S2), and the second value (v2) being a function (e.g. a goniometric function) of the first (in-plane) and second (out-of-plane) gradient of the component signals obtained from the second and third sensor (S2, S3). The function may be a goniometric function, e.g. an arctangent function, or an arctan 2 function.

In an embodiment, the position sensor device comprises at least three sensors, and is adapted for calculating the coarse signal (Sc) as a function (e.g. a goniometric function or a polynomial expression) of a first ratio (R1) and a second ratio (R2), wherein the first ratio (R1) is calculated as a ratio of the first (in-plane) gradient and the second (out-of-plane) gradient obtained from the first and second sensor (S1, S2), and wherein the second ratio (R2) is calculated as a ratio of the first (in-plane) gradient and the second (out-of-plane) gradient obtained from the second and third sensor (S2, S3). This can be written as follows:
R1=(ΔBx12/Δx12,ΔBz12/Δx12),
R2=(ΔBx23/Δx23,ΔBz23/Δx23),
Sc=f(R1,R2).
Since Δx12is present in the nominator and denominator of R1, the division by Δx12can be omitted. Likewise, the division by Δx23can be omitted in R2. Hence, this can be simplified to:
R1=ΔBx12/ΔBz12,
R2=ΔBx23/ΔBz23,
Sc=f(R1,R2).

In an embodiment, the position sensor device comprises at least three sensors and is adapted for calculating the coarse signal (Sc) based on the following formulas:
v1=arctan 2(K*ΔBx12/Δx12,ΔBz12/Δx12),
v2=arctan 2(K*ΔBx23/Δx23,ΔBz23/Δx23),
delta=(v1−v2+n*360°),
Sc=delta, orSc=1/delta,
where K is a predefined constant or is a predefined function of temperature, n is an integer chosen such that delta lies in the range from 0° to 360°, Sc is the coarse signal, atan 2 or arctan 2 is the two-argument arctangent function, ΔBx12/Δx12is a first gradient (or “in-plane gradient”) of the first magnetic field components (Bx1, Bx2) obtained from the first and second sensor, ΔBx23/Δx23is a first gradient of the first magnetic field components (Bx2, Bx3) obtained from the second and third sensor, ΔBz12/Δx12is a second gradient (or “out-of-plane gradient”) of the second magnetic field components (Bz1, Bz2) obtained from the first and second sensor, and ΔBz23/Δx23is a second gradient of the second magnetic field components (Bz2, Bz3) obtained from the second and third sensor.

For the same reason as explained above, the division by Δx12and Δx23can be omitted, and thus the formula for v1and v2can be simplified to:
v1=arctan 2(K*ΔBx12,ΔBz12), and
v2=arctan 2(K*ΔBx23,ΔBz23).

K may be a predefined constant equal to 1.0. K may be a predefined constant different from 1.0, for example smaller than 0.95 or larger than 1.05. In some embodiments, K is determined as a function K(T) of temperature. The position sensor device may comprise a temperature sensor to this end. This temperature sensor may be configured for measuring a substrate temperature at any location.

The value of K may be chosen such that, for a particular position of the sensor device relative to the magnet, the magnitude of K*dBx/dx is substantially equal to the magnitude of dBz/dx, or the magnitude or K*ΔBx12is substantially equal to the magnitude of ΔBz12over the envisioned measurement range. The value of K, or the values or parameters of the function K(T) may be determined during calibration or simulation and may be stored in a non-volatile memory.

In an embodiment, the position sensor device comprises at least four magnetic sensors, and is adapted for calculating the coarse signal (Sc) based on the following set of formulas:
v1=arctan 2(K*ΔBx12/Δx12,ΔBz12/Δx12),
v2=arctan 2(K*ΔBx34/Δx34,ΔBz34/Δx34),
delta=(v1−v2+n*360°),
Sc=delta, orSc=1/delta,
where K is a predefined constant or is a predefined function of temperature, n is an integer chosen such that delta lies in the range from 0° to 360°, Sc is the coarse signal, atan 2 or arctan 2 is the two-argument arctangent function, ΔBx12/Δx12is a first gradient (or “in-plane gradient”) of the first magnetic field components (Bx1, Bx2) obtained from the first and second sensor, ΔBx34/Δx34is a first gradient of the first magnetic field components (Bx3, Bx4) obtained from the third and fourth sensor, ΔBz12/Δx12is a second gradient (or “out-of-plane gradient”) of the second magnetic field components (Bz1, Bz2) obtained from the first and second sensor, and ΔBz34/Δx34is a second gradient of the second magnetic field components (Bz3, Bz4) obtained from the third and fourth sensor.

Because the arctan 2 function is based on a ratio of its two arguments, the formulas for v1and v2can be simplified to:
v1=arctan 2(K*ΔBx12,ΔBz12),
v2=arctan 2(K*ΔBx34,ΔBz34).

As mentioned above, K may be a predefined constant equal to 1.0, or K may be a predefined constant different from 1.0, or K may be determined by a function K(T) of temperature.

It is an advantage of these formulas, that the coarse signal is substantially insensitive to demagnetization effects of the magnet, but moreover, since the signal is based on differential signals, is robust against an external disturbance field. It is noted that the coarse signal may monotonically increase or monotonically decrease over the measurement range of interest, but that is not absolutely required. Instead, what is required is that the combination of a particular fine signal value and the corresponding coarse signal value is unique for every location to be measured.

In an embodiment, the position sensor device comprises at least three sensors (S1, S2, S3) or at least four sensors (S1, S2, S3, S4), and is adapted for calculating the fine signal (Sf) based on a ratio of the two first gradients (ΔBx12/Δx12, ΔBx23/Δx23), or based on a ratio of the two second gradients (ΔBx34/Δx34, ΔBz34/Δx34).

In an embodiment, the position sensor device comprises at least three sensors (S1, S2, S3) or at least four sensors (S1, S2, S3, S4), and is adapted for calculating the fine signal (Sf) based on a goniometric function of a ratio of the two first gradients, or based on a goniometric function of a ratio of the two second gradients.

In an embodiment, the position sensor device comprises at least three sensors, and is adapted for calculating the fine signal (Sf) based on one of the following formulas:
Sf=arctan 2(K*ΔBx12/Δx12,ΔBz12/Δx12), or
Sf=arctan 2(K*ΔBx23/Δx23,ΔBz23/Δx23), or
Sf=arctan 2(K*ΔBx13/Δx13,ΔBz13/Δx13)
wherein Sf is the fine signal, atan 2 or arctan 2 is the two-argument arctangent function, K is a predefined constant or is a predefined function of temperature, ΔBx12/Δx12is a first gradient of the first magnetic field components (Bx1, Bx2) obtained from the first and second sensor (S1, S2), ΔBx23/Δx23is a first gradient of the first magnetic field components (Bx2, Bx3) obtained from the second and third sensor (S2, S3), ΔBx13/Δx13is a first gradient of the first magnetic field components (Bx1, Bx3) obtained from the first and third sensor (S1, S3), ΔBz12/Δx12is a second gradient of the second magnetic field components (Bz1, Bz2) obtained from the first and second sensor (S, S2), ΔBz23/Δx23is a second gradient of the second magnetic field components (Bz2, Bz3) obtained from the second and third sensor (S2, S3), ΔBz13/Δx13is a second gradient of the second magnetic field components (Bz1, Bz3) obtained from the first and third sensor (S1, S3).

As mentioned above, K may be a predefined constant equal to 1.0, or K may be a predefined constant different from 1.0, or K may be determined by a function K(T) of temperature.

For the same reasons as mentioned above, the formulas for Sf can be simplified to:
Sf=arctan 2(K*ΔBx12,ΔBz12), or
Sf=arctan 2(K*ΔBx23,ΔBz23), or
Sf=arctan 2(K*Δx13,ΔBz13)

In an embodiment, the position sensor device comprises at least three sensors, which are spaced equidistantly, and is adapted for calculating the fine signal (Sf) based on a second order gradient, according to the following set of formulas:
Δ2Bx/Δx2=(ΔBx23/Δx)−(ΔBx12/Δx)
Δ2Bz/Δx2=(ΔBz23/Δx)−(ΔBz12/Δx)
Sf=arctan 2(L*Δ2Bx/Δx2,Δ2Bz/Δx2),
where L is a predefined constant, or a function of temperature. These formulas can also be written as:
d2Bx=(ΔBx23−ΔBx12),
d2Bz=(ΔBz23−ΔBz12),
Sf=arctan 2(L*d2Bx,d2Bz).

In an embodiment, the position sensor device comprises at least four sensors, and is adapted for calculating the fine signal (Sf) based on one of the following formulas:
Sf=arctan 2(K*ΔBx12/Δx12,ΔBz12/Δx12), or
Sf=arctan 2(K*ΔBx23/Δx23,ΔBz23/Δx23), or
Sf=arctan 2(K*ΔBx34/Δx34,ΔBz34/Δx34)
wherein Sf is the fine signal, atan 2 or arctan 2 is the two-argument arctangent function, K is a predefined constant or is a predefined function of temperature, ΔBx12/Δx12is a first gradient of the first magnetic field components (Bx1, Bx2) obtained from the first and second sensor (S1, S2), ΔBx23/Δx23is a first gradient of the first magnetic field components (Bx2, Bx3) obtained from the second and third sensor (S2, S3), ΔBx34/Δx34is a first gradient of the first magnetic field components (Bx3, Bx4) obtained from the third and fourth sensor (S3, S4), ΔBz12/Δx12is a second gradient of the second magnetic field components (Bz1, Bz2) obtained from the first and second sensor (S1, S2), ΔBz23/Δx23is a second gradient of the second magnetic field components (Bz2, Bz3) obtained from the second and third sensor (S2, S3), ΔBz34/Δx34is a second gradient of the second magnetic field components (Bz3, Bz4) obtained from the third and fourth sensor (S3, S4).

For the same reasons as mentioned above, these formulas can also be written as:
Sf=arctan 2(K*ΔBx12,ΔBz12), or
Sf=arctan 2(K*ΔBx23,ΔBz23), or
Sf=arctan 2(K*ΔBx34,ΔBz34)

But of course, Sf can also be determined based on an arctangent function of a ratio of the signals obtained from sensor S1and sensor S3, or the signals obtained from S1and S4, or the signals obtained from S2and S4.

In an embodiment, the position sensor device comprises four sensors, which are spaced equidistantly, and is adapted for calculating the fine signal (Sf) based on a second order gradient, according to the following set of formulas:
Δ2Bx/Δx2=(ΔBx34/Δx)−(ΔBx12/Δx)
Δ2Bz/Δx2=(ΔBz34/Δx)−(ΔBz12/Δx)
Sf=arctan 2(L*Δ2Bx/Δx2,Δ2Bz/Δx2),
where L is a predefined constant, or a function of temperature. These formulas can also be written as:
d2Bx=ΔBx34−ΔBx12,
d2Bz=ΔBz34−ΔBz12,
Sf=arctan 2(L*d2Bx,d2Bz)

It is an advantage that the fine signal Sf (or a value derived therefrom) is substantially insensitive to demagnetization effects, because it is based on a ratio.

It is an advantage that the fine signal Sf is highly robust against a (constant) external disturbance field, because it is based on magnetic field gradients.

In an embodiment, the position sensor device is adapted for determining said position by determining a plurality of at least two candidate positions (e.g. xA, xB) based on the fine signal only, and then selecting one of these candidate positions considering also the coarse signal.

The second step (selecting) may include selecting the candidate position for which the coarse signal deviates least with a predefined coarse position associated with said fine signal.

In an embodiment, each magnetic sensor comprises an integrated magnetic concentrator (IMC) and a pair of two horizontal Hall elements arranged on opposite sides of the magnetic concentrator, e.g. as illustrated inFIG. 4(a)orFIG. 4(b).

Preferably the horizontal Hall elements of the plurality of magnetic sensors are collinear.

It is an advantage that each such “magnetic sensor” comprising a pair of horizontal Hall elements and a magnetic concentrator can measure Bx and Bz at one sensor location. Hence three such “magnetic sensors” allow to measure a value of Bx and Bz at three different sensor locations. A pairwise subtraction of the Bx-values and the Bz-values of adjacent sensor structures allow to calculate the gradients (or spatial derivatives).

In an embodiment, each magnetic sensor comprises a horizontal Hall element and a vertical Hall element, as illustrated for example inFIG. 5(a)andFIG. 5(b).

The distances Δx12, Δx23between centers of the horizontal Hall elements and the distances between centers of the vertical Hall elements is preferably the same, but that is not absolutely required.

In an embodiment, the distance between centers of the vertical Hall elements is larger than the distance between centers of the horizontal Hall elements, e.g. at least 5% to 10% larger, without having to increase the size of the substrate. In this way, the signals obtained from the vertical Hall elements can be (slightly) increased, hence, the SNR can be slightly increased, and the accuracy of the determined position can be improved.

In an embodiment, the position sensor device comprises three horizontal Hall elements equidistantly spaced over a first distance in a first direction and comprises three vertical Hall elements equidistantly spaced over a second distance in the first direction.

The first distance may be equal to the second distance, but that is not absolutely required. The horizontal Hall elements (without IMC) are adapted to measure the out-of-plane magnetic field vector Bz (oriented perpendicular to the sensor substrate) at three different sensor locations. The three vertical Hall elements are adapted to measure the in-plane magnetic field vector Bx (oriented parallel to the sensor substrate). By determining Bx and Bz at three different sensor locations, two gradients (or spatial derivatives) dBx/dx and dBz/dx can be calculated by pairwise subtraction.

According to a second aspect, the present invention also provides a method of determining a position of a position sensor device in a position sensing system, wherein the position sensor device is movable relative to a magnetic structure having a plurality of poles, and wherein the position sensor device comprises: a semiconductor substrate, and at least three sensors for measuring at least three first magnetic field components (e.g. Bx1, Bx2, Bx3) oriented in a first direction (e.g. X) substantially parallel to the substrate on at least three different locations (e.g. X1, X2, X3) spaced apart over predefined distances (e.g. Δx12, Δx23) along the first direction, and for measuring at least three second magnetic field components (e.g. Bz1, Bz2, Bz3) oriented in a second direction (e.g. Z) oriented substantially perpendicular to the substrate on said at least three different locations, and a processing unit; the method comprising the steps of: a) measuring a first magnetic field component (e.g. Bx1, Bx2, Bx3) in said at least three locations (e.g. X1, X2, X3), and calculating two first gradients (e.g. ΔBx12/Δx12, ΔBx23/Δx23) of the first magnetic field components along the first direction; b) measuring a second magnetic field component (e.g. Bz1, Bz2, Bz3) in said at least three locations, and calculating two second gradients (e.g. ΔBz12/Δx12, ΔBz23/Δx23) of the second magnetic field components along the first direction; c) calculating a coarse signal (Sc) based on at least some of the first and second gradients; d) calculating a fine signal (Sf) based on at least some of the first and second gradients; e) determining a position (e.g. X, a) based on the coarse signal (Sc) and the fine signal (Sf).

As described above, the main advantages of this method are that a unique position can be determined, that the position can be accurate thanks to the fine signal, that an absolute position can be determined thanks to the coarse signal, that the position thus determined is substantially insensitive to magnetic degradation, and to an external disturbance field (if present).

It is a further advantage that this method can be performed by a simple processor, (for example an 8-bit or 16-bit processor running at a moderate clock speed, e.g. lower than 40 MHz).

In an embodiment, each of the coarse signal (Sc) and the fine signal (Sf) is derived from a ratio of an in-plane magnetic field gradient (e.g. dBx/dx) and an out-of-plane magnetic field gradient (e.g. dBz/dx).

In an embodiment, step c) comprises: calculating the coarse signal (Sc) based on a linear combination (e.g. a difference) of a first value and a second value (e.g. v1, v2), the first value (v1) being a function (e.g. a goniometric function) of the first (in-plane) and second (out-of-plane) gradient of the component signals obtained from the first and second sensor (S1, S2), and the second value (v2) being a function (e.g. a goniometric function) of the first (in-plane) and second (out-of-plane) gradient of the component signals obtained from the second and third sensor (S2, S3). The function may be a goniometric function, e.g. an arctangent function, or an arctan 2 function.

In an embodiment, step c) comprises: calculating the coarse signal (Sc) based on a first set of formulas, comprising:
v1=arctan 2(K*ΔBx12/Δx12,ΔBz12/Δx12),
v2=arctan 2(K*ΔBx23/Δx23,ΔBz23/Δx23),
delta=(v1−v2+n*360°),
Sc=delta, orSc=1/delta,
where K is a predefined constant or is a predefined function of temperature, n is an integer chosen such that delta lies in the range from 0° to 360°, Sc is the coarse signal, arctan 2 is the two-argument arctangent function, ΔBx12/Δx12is a first gradient of the first magnetic field components (Bx1, Bx2) obtained from the first and second sensor (S1, S2), ΔBx23/Δx23is a first gradient of the first magnetic field components (Bx2, Bx3) obtained from the second and third sensor (S2, S3), ΔBz12/Δx12is a second gradient of the second magnetic field components (Bz1, Bz2) obtained from the first and second sensor (S1, S2), and ΔBz23/Δx23is a second gradient of the second magnetic field components (Bz2, Bz3) obtained from the second and third sensor (S2, S3).

As mentioned above, K may be a predefined constant equal to 1.0, or K may be a predefined constant different from 1.0, or K may be determined by a function K(T) of temperature.

As described above, the formulas of v1and v2can be simplified by omitting the division by Δx12and by Δx23.

In an embodiment, step c) comprises: calculating the coarse signal (Sc) based on a second set of formulas, comprising:
v1=arctan 2(K*ΔBx12/Δx12,ΔBz12/Δx12),
v2=arctan 2(K*ΔBx34/Δx34,ΔBz34/Δx34),
delta=(v1−v2+n*360°),
Sc=delta, orSc=1/delta,
where K is a predefined constant or is a predefined function of temperature, n is an integer chosen such that delta lies in the range from 0° to 360°, Sc is the coarse signal, arctan 2 is the two-argument arctangent function, ΔBx12/Δx12is a first gradient of the first magnetic field components (Bx1, Bx2) obtained from the first and second sensor (S1, S2), ΔBx34/Δx34is a first gradient of the first magnetic field components (Bx3, Bx4) obtained from the third and fourth sensor (S3, S4), ΔBz12/Δx12is a second gradient of the second magnetic field components (Bz1, Bz2) obtained from the first and second sensor (S1, S2), and ΔBz34/Δx34is a second gradient of the second magnetic field components (Bz3, Bz3) obtained from the third and fourth sensor (S3, S4). As mentioned above, K may be a predefined constant equal to 1.0, or K may be a predefined constant different from 1.0, or K may be determined by a function K(T) of temperature.

As described above, the formulas of v1and v2can be simplified by omitting the division by Δx12and by Δx34.

In an embodiment, step d) comprises: calculating the fine signal (Sf) as a function of the first (in-plane) magnetic field gradient and the second (out-of-plane) magnetic field gradient of the signals obtained from two of said at least three sensors (e.g. S1and S2, or S1and S3, or S2and S3). The function may be a goniometric function, e.g. an arctangent function, or an arctan 2 function.

In an embodiment, step d) comprises: calculating the fine signal (Sf) based on one of the following formulas:
Sf=arctan 2(K*ΔBx12/Δx12,ΔBz12/Δx12), or
Sf=arctan 2(K*ΔBx23/Δx23,ΔBz23/Δx23), or
Sf=arctan 2(K*ΔBx34/Δx34,ΔBz34/Δx34)
wherein Sf is the fine signal, arctan 2 is the two-argument arctangent function, K is a predefined constant or is a predefined function of temperature, ΔBx12/Δx12is a first gradient of the first magnetic field components (Bx1, Bx2) obtained from the first and second sensor (S1, S2), ΔBx23/Δx23is a first gradient of the first magnetic field components (Bx2, Bx3) obtained from the second and third sensor (S2, S3), ΔBx34/Δx34is a first gradient of the first magnetic field components (Bx3, Bx4) obtained from the third and fourth sensor (S3, S4), ΔBz12/Δx12is a second gradient of the second magnetic field components (Bz1, Bz2) obtained from the first and second sensor (S1, S2), ΔBz23/Δx23is a second gradient of the second magnetic field components (Bz2, Bz3) obtained from the second and third sensor (S2, S3), Δz34/Δx34is a second gradient of the second magnetic field components (Bz3, Bz4) obtained from the third and fourth sensor (S3, S4).

As described above, the formulas of Sf can be simplified by omitting the division by Δx12and by Δx23, and by Δx34.

But of course, Sf can also be determined based on an arctangent function of a ratio of the signals obtained from sensor S1and sensor S3, or the signals obtained from S1and S4, or the signals obtained from S2and S4.

In an embodiment, step d) comprises: calculating the fine signal (Sf) based on a second order gradient, according to the following set of formulas:
Δ2Bx/Δx2=(ΔBx23/Δx)−(ΔBx12/Δx)
Δ2Bz/Δx2=(ΔBz23/Δx)−(ΔBz12/Δx)
Sf=arctan 2(L*Δ2Bx/Δx2,Δ2Bz/Δx2),
where L is a predefined constant, or a function of temperature, or according to the following set of formulas:
Δ2Bx/Δx2=(ΔBx34/Δx)−(ΔBx12/Δx)
Δ2Bz/Δx2=(ΔBz34/Δx)−(ΔBz12/Δx)
Sf=arctan 2(L*Δ2Bx/Δx2,Δ2Bz/Δx2).

As described above, these formulas of Sf can be simplified by omitting the division by /Δx and by Δx2.

In another or further embodiment, step e) comprises: determining said position by determining a plurality of at least two candidate positions (e.g. xA, xB) based on the fine signal (Sf), and then selecting one of these candidate positions (e.g. xA, xB) based on the coarse signal (Sc).

Step e) may comprise: choosing the candidate that shows the smallest deviation from a predetermined coarse signal corresponding to this fine signal, e.g. as determined during a calibration step, and stored in a non-volatile memory. The sensor device may comprise for example a look-up table with at least three columns, a first column storing values for the fine signal Sf, the second column storing values for the coarse signal Sc, the third column storing values of an actual displacement value along the direction of movement, or along the movement trajectory, and the method may include the step of finding the best matching value, e.g. using interpolation (e.g. linear interpolation).

According to a third aspect, the present invention also provides a computer-program-product for performing a method according to the second aspect, when being executed on a position sensor device according to the first aspect.

According to a fourth aspect, the present invention also provides a position sensor system comprising: a position sensor device according to the first aspect; a magnetic structure comprising a plurality of poles; the magnetic structure being movable relative to the position sensor device (or vice versa) in a movement direction or along a movement trajectory; wherein a distance (e.g. Xpp, app) between centres of adjacent poles of the magnetic structure varies along the movement direction or along the movement trajectory; wherein the sensor device is oriented such that its first axis (e.g. X) is tangential to the movement direction or movement trajectory.

In an embodiment, the position sensor device is movably arranged relative to the magnetic structure at a substantially constant distance from the magnetic structure.

In an embodiment, the magnetic structure comprises at least four, or at least five, or at least six pole pairs.

What is meant is that the sensor device is adapted for facing at least four, or at least five, etc. poles when moving along its trajectory.

In an embodiment, the magnetic structure is an assembly of a plurality of discrete permanent magnets.

In an embodiment, the magnetic structure comprises a monolithic magnetic material which is magnetized so as to have a plurality of poles, wherein adjacent poles are oriented in opposite directions.

In an embodiment, the magnetic structure has an (overall) elongated shape having a longitudinal axis (e.g. having a substantially linear shape).

This is referred to as “a linear position sensor system”, in which case the position sensor device may be adapted for moving relative to the magnetic structure along a trajectory coinciding with or substantially parallel to said longitudinal axis.

In an embodiment, the magnetic structure has a curved shape having a curved axis (e.g. circular, spiral, elliptical, parabolic, etc).

This is referred to as an “angular position sensor system”, in which case the sensor device may be adapted for moving relative to the magnetic structure along a trajectory coinciding with or located at a substantially constant distance from said curved axis. The curved axis may, but need not necessarily be closed. It can for example be a circle segment or an arc segment.

In an embodiment, the remanent magnetic field inside the magnetic material is oriented substantially perpendicular to said (e.g. linear or curved) axis.

Preferably the sensor device comprises a single semiconductor substrate, and the remanent magnetic field inside the magnetic material is oriented perpendicular to said semiconductor substrate.

In an embodiment, a remanent magnetic field inside the magnetic material is oriented substantially parallel to said second axis (e.g. Z).

In an embodiment, said distance between centres of adjacent poles varies strict monotonically along said first axis. In other words, when moving from a start position of the magnetic structure to an end position, the distance between centres of the poles increases or decreases for each new pole encountered.

In another embodiment, said distances between centres of adjacent poles increases over a first portion and decreases over a second portion.

According to a fifth aspect, the present invention also provides an axially or radially magnetized ring magnet comprising a plurality of alternating poles, wherein an angular distance (αi) between centres of adjacent poles measured at a periphery of the ring magnet, increases over a first angular portion and decreases over a second angular portion of a full 360° range, measured in clockwise direction.

The poles may have the shape of pie segments, in which case the axially or radially magnetized ring magnet comprises a plurality of pie segments spanning different arc segments of the periphery of the ring magnet.

In an embodiment, the ring magnet has exactly four pie segments, with four different adjacent pie sizes, namely size1, size2, size3, size4, wherein size1 is the smallest size, and size3 is the largest size, and wherein size1<size4<size2<size3, or wherein size1<size2<size4<size3.

In an embodiment, the ring magnet has exactly six pie segments, with six different adjacent pie sizes, namely size1, size2, size3, size4, size5, size6, wherein size1 is the smallest size, and size4 is the largest size, and wherein size1<size6<size2<size5<size3<size4, or wherein size1<size6<size2<size3<size5<size4, or wherein size1<size2<size6<size5<size3<size4, or wherein size1<size2<size6<size3<size5<size4.

Particular and preferred aspects of the invention are set out in the accompanying independent and dependent claims. Features from the dependent claims may be combined with features of the independent claims and with features of other dependent claims as appropriate and not merely as explicitly set out in the claims.

These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter.

