Position sensor with master track and nonius track

Abstract

To provide a sensing system and a method for sensing a position.SOLUTION: A sensing system and a method for sensing a position include a first magnetic track comprising a first number of multipoles for generating a magnetic field cooperatively fixed to a second magnetic track for generating a magnetic field and a second sensor for sensing magnetic field, forming a magnetic structure. At least two sensors are included. A first sensor is positioned proximally to the first magnetic track, closer to the first magnetic track than to the second magnetic track. The second sensor is positioned proximally to the second magnetic track. The distance between the first sensor and the second magnetic track is larger than the distance between the second sensor and the second magnetic track. The magnetic flux density generated by the first and second magnetic tracks follow a ratio of two or more.SELECTED DRAWING: Figure 11

Description

Technical Field

[0001] The present invention relates to the field of position sensing. More specifically, it relates to a position sensing system for determining the relative position of a magnetic structure with respect to a magnetic field sensor.

Background Art

[0002] Position sensing systems are typically included in devices that need to detect the positions of some of their components. For example, many engines include an angular position sensing system for detecting the relative position of a rotor with respect to a stator in order to ensure proper power supply to an engine coil.

[0003] These typically include a magnetic field sensor and a magnetic piece. The relative movement of one with respect to the other is detected by the sensor, and the sensor provides a signal. The accuracy, resolution, and other characteristics of the measurement signal depend on several factors such as the type of magnet. A conventional rotary encoder with a simple dipole magnet and a Hall magnetic sensor has an angular resolution limited to about 0.02 degrees and an angular accuracy limited to about 0.3 degrees over temperature, which also depends on the signal-to-noise ratio.

[0004] Multipole magnets improve the resolution and accuracy of relative positioning. However, multipole magnets are divided into sectors, and a magnetic sensor alone cannot identify the position of the angular sector itself. This means that information about the absolute angular position is lost.

[0005] To solve this, existing magnetic structures include two multipole magnetic tracks, one of which has fewer pole pairs than the other. Thus, the complete 360° range can usually be reconstructed by combining the signals of both tracks obtained by a pair of sensors integrated on a single chip. The track with the most poles is the "master track".

Summary of the Invention

Problems to be Solved by the Invention

[0006] Sectors are identified using the difference between signals from two tracks, and angles are measured using the signal from the master track. However, these types of systems have high crosstalk between fields. While tracks can be physically separated to reduce crosstalk, this requires two separate chips, or an integrated sensor requires more separation, and therefore a larger sensor chip area, thus increasing costs.

[0007] Embodiments of the present invention aim to provide sensing systems, position sensors including such systems, and methods for sensing position. The present invention enables accurate detection of the position of a magnetic structure with respect to a magnetic sensor without loss of information about absolute position. It also provides a compact sensing system in which sensors can be integrated. [Means for solving the problem]

[0008] In a first aspect, the present invention provides a sensing system for sensing position, comprising a first magnetic track including a first number of multipole poles for generating a magnetic field, and a second magnetic track for generating a magnetic field. The first and second magnetic tracks are linked and fixed to each other to form a magnetic structure. At least a first sensor and a second sensor are included for sensing magnetic fields at different positions.

[0009] The first sensor is positioned near the first magnetic track, and closer to the first magnetic track than to the second magnetic track. The second sensor is positioned near the second magnetic track. The distance between the first sensor and the second magnetic track is greater than the distance between the second sensor and the second magnetic track. The magnetic flux densities generated by the first and second magnetic tracks follow a ratio of 2 or greater.

[0010] An advantage of the embodiments of the present invention is that the signal sensed by the first sensor is affected by a negligible contribution of crosstalk from a weaker second track, and therefore crosstalk compensation is not required, while providing a compact device and a highly integrable sensor.

[0011] In some embodiments of the present invention, the projection of the first sensor in the direction perpendicular to the track (the direction of the distance between the sensor and the magnetic structure) overlaps with the first track. In some embodiments, the projection of the second sensor in the direction of the distance between the second sensor and the magnetic structure does not overlap with the first track. For example, the projection of the second sensor overlaps with the gap of nonmagnetic material provided between the first track and the second track. For example, the projection of the second sensor overlaps with the second track. The present invention is not limited thereto, and the second sensor may be positioned such that its projection also overlaps with the first track.

[0012] In some embodiments of the present invention, the tracks are concentric tracks that can rotate around a common axis of rotation.

[0013] An advantage of the embodiments of the present invention is that they can provide an angular position sensing system.

[0014] In a particular embodiment, the tracks are coplanar tracks. The second track is surrounded by the first track. The first track has a first predetermined width, and the second track has a second predetermined width. The first predetermined width is at least twice as large as the second predetermined width.

[0015] An advantage of the embodiments of the present invention is that they can provide a sensing system having a flat profile.

[0016] In some embodiments of the present invention, the first track and the second track are stacked rings having the same outer radius. The width defined in the axial direction of the first track is at least twice as large as the width of the second track.

[0017] An advantage of the embodiments of the present invention is that a ring multipole is easily provided. A further advantage is that the ability of the sensor to be positioned on the side may be desirable under certain spatial constraints.

[0018] In some embodiments of the present invention, the first track is a multipole having at least eight dipoles, and the second track has a non-zero number of dipoles, the number being different from the number of dipoles of the first track.

[0019] An advantage of the embodiments of the present invention is that the sensing system can be made more compact compared to other solutions that have more poles.

[0020] In some embodiments of the present invention, the first and second sensors are adapted to sense different field components, typically tangential and axial field components.

[0021] An advantage of the embodiments of the present invention is that the position relative to the second track can be obtained by a linear combination of the axial field component and the tangential field component, and the axial component is usually not very sensitive to crosstalk.

[0022] In some embodiments of the present invention, the first sensor and the second sensor are integrated into a single semiconductor chip.

[0023] An advantage of the embodiments of the present invention is that manufacturing costs can be reduced without sacrificing compactness or precision.

[0024] In some embodiments of the present invention, the system further includes signal processing means for processing sensor signals. The system further includes a signal output for providing the absolute position of a first track relative to the sensor.

[0025] An advantage of the embodiments of the present invention is that the sensing system can be used as a position sensor.

[0026] In certain embodiments, the processing means is adapted to calculate an initial position from the measurement value of a second sensor when the sensing system is activated.

[0027] An advantage of the embodiments of the present invention is that the sensing system can provide sector identification while powered on and can therefore be simply fitted by taking into account the measurements of the first sensor. A further advantage is that the computational load is reduced and therefore the sensing speed can be increased.

[0028] In certain embodiments, the processing means is adapted to obtain a position from measurement signals from a first sensor and a second sensor and to calibrate the position.

[0029] An advantage of the embodiments of the present invention is that a simple lookup table can be used to compensate for, for example, mechanical misalignment, defects in the track, and so on.

[0030] In a second aspect, the present invention provides a method for sensing a position using a sensing system described in any one of the preceding claims, further comprising: obtaining measurements from a first sensor and a second sensor; and calculating the position of a magnetic structure relative to the first sensor.

[0031] An advantage of the embodiments of the present invention is that the position can be obtained without the need for crosstalk compensation.

[0032] In some embodiments of the present invention, the method further includes subsequently calibrating the results for compensation of mechanical misalignment.

[0033] An advantage of the embodiments of the present invention is that a simple lookup table can be used.

[0034] In some embodiments of the present invention, the method further includes detecting the position of a first track by using measurements from a first sensor and a second sensor for detecting the dipole of the magnetic structure on which the sensor is placed, while ignoring the measurement from the second sensor for detecting the absolute position of the first sensor with respect to the magnetic structure.

[0035] An advantage of the embodiments of the present invention is that the initial measurement can be updated with the absolute position measurement.

[0036] In some embodiments of the present invention, the detection of the dipole position and absolute position is performed, for example, as a first step when the sensor is activated, and the method further includes ignoring the signal of the second sensor in subsequent measurements by using the measurement of the first sensor to extract the dipole of the magnetic structure on which the sensor is placed after the initial position of the first track has been detected. An advantage is that the method can provide faster measurements.

[0037] In some embodiments of the present invention, the position of a first track is detected by using the measurements of the first and second sensors to detect the dipole of the magnetic structure on which the sensor is located, and to detect the absolute position of the first sensor with respect to the magnetic structure, by performing a linear combination of the measurements of the first and second sensors.

[0038] In some embodiments of the present invention, calculating the position of the magnetic structure relative to the first sensor involves obtaining a linear combination of both the axial and tangential components of the magnetic field generated by both tracks.

[0039] A further advantage is that the method can provide the position of a second track without complex calculations, and can enable the reconstruction of the system's absolute position, for example, its angular position within a 360° cycle.

[0040] Specific and preferred embodiments of the invention are described in the attached independent and dependent claims. Features from the dependent claims are not limited to those explicitly described in those claims, but may be combined with features of the independent claims and other dependent claims as necessary.

[0041] These and other aspects of the present invention will be apparent from and clarified by the embodiments described below. [Brief explanation of the drawing]

[0042] [Figure 1] The prior art sensors and rotary axles used as measurement targets are shown. [Figure 2] This shows three multi-pole magnetic structures or encoders, the first two being angular encoders and the third being linear. [Figure 3] This shows different sensor devices, including multiple magnetic sensors with different distributions that are suitable for measuring the orthogonal components of a magnetic field. [Figure 4] This shows different sensor devices, including multiple magnetic sensors with different distributions that are suitable for measuring the orthogonal components of a magnetic field. [Figure 5] This shows different sensor devices, including multiple magnetic sensors with different distributions that are suitable for measuring the orthogonal components of a magnetic field. [Figure 6] This shows different sensor devices, including multiple magnetic sensors with different distributions that are suitable for measuring the orthogonal components of a magnetic field. [Figure 7] This shows different sensor devices, including multiple magnetic sensors with different distributions that are suitable for measuring the orthogonal components of a magnetic field. [Figure 8] This shows different sensor devices, including multiple magnetic sensors with different distributions that are suitable for measuring the orthogonal components of a magnetic field. [Figure 9] This shows different sensor devices, including multiple magnetic sensors with different distributions that are suitable for measuring the orthogonal components of a magnetic field. [Figure 10] This shows different sensor devices, including multiple magnetic sensors with different distributions that are suitable for measuring the orthogonal components of a magnetic field. [Figure 11] This document shows a sensing system including a sensor device and magnetic structure according to an embodiment of the present invention for angular position sensing. [Figure 12] Figure 11 shows a top view of the system. [Figure 13] Another sensing system, including a sensor device and magnetic structure according to an embodiment of the present invention, for angular position sensing is shown. [Figure 14] Another sensing system, including a sensor device and magnetic structure according to an embodiment of the present invention, for linear position sensing is shown. [Figure 15] A schematic diagram of an existing signal processing method for obtaining the absolute position of a target using a prior art position sensing system, as shown in Figure 1 or Figure 2, is provided. [Figure 16] A schematic diagram of a method according to an embodiment of the present invention for obtaining the absolute position of a target using a sensing system according to an embodiment of the present invention is shown. [Modes for carrying out the invention]

[0043] The drawings are only schematic and not limiting. Some elements in the drawings may be exaggerated in size and are not drawn to scale for illustrative purposes only.

[0044] Any reference numeral in the claims should not be construed as limiting the scope.

[0045] In different drawings, the same reference numeral refers to the same or similar element.

[0046] The present invention will be described with respect to certain embodiments and with reference to some drawings, but will not be limited thereto, and will be limited only by the claims. Dimensions and relative dimensions will not correspond to actual reductions in the implementation of the invention.

[0047] Furthermore, the terms 1, 2, and similar terms in the description and claims are used to distinguish similar elements and are not necessarily used to describe any sequence in time, space, ranking, or any other way. It should be understood that the terms used in this manner are interchangeable under appropriate circumstances, and that embodiments of the invention described herein may operate in sequences other than those described or illustrated herein.

[0048] Furthermore, terms such as "above," "below," and similar terms in the description and claims are used for illustrative purposes only and not necessarily to describe relative positions. It should be understood that these terms are interchangeable under appropriate circumstances, and that embodiments of the invention described herein may operate in orientations other than those described or illustrated herein.

[0049] It should be noted that the term “equipped with” as used in the claims should not be construed as being limited to the means subsequently enumerated, nor should it exclude other elements or steps. Therefore, it should be interpreted as specifying the presence of the described features, integers, steps, or components mentioned, but not as excluding the presence or addition of one or more other features, integers, steps, or components, or groups thereof. Thus, the term “equipped with” encompasses situations where only the described features are present, as well as situations where these features and one or more other features are present. Therefore, the expression “a device comprising means A and B” should not be interpreted as being limited to a device consisting only of components A and B. This means, with respect to the present invention, that the relevant components of the device are only A and B.

[0050] Throughout this specification, any reference to “one embodiment” or “embodiment” means that a particular feature, structure, or characteristic described in relation to an embodiment is included in at least one embodiment of the present invention. Therefore, occurrences of the phrase “in one embodiment” or “in an embodiment” in various parts of this specification do not necessarily all refer to the same embodiment, although they may refer to the same embodiment. Furthermore, certain features, structures, or characteristics can be combined in any suitable manner in one or more embodiments, as will be apparent to those skilled in the art from this disclosure.

[0051] Similarly, in the description of exemplary embodiments of the present invention, various features of the invention may be grouped into a single embodiment, figure, or description for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various embodiments of the invention. However, this method of disclosure should not be interpreted as reflecting an intention that the claimed invention requires more features than are explicitly described in each claim. Rather, as reflected in the claims below, the embodiments of the invention are fewer than all the features of the single embodiments disclosed above. Accordingly, the claims following the detailed description are explicitly incorporated into this detailed description, and each claim exists independently as a distinct embodiment of the invention.

[0052] Furthermore, some embodiments described herein include some features included in other embodiments, but do not include other features included in other embodiments, and combinations of features of different embodiments mean that they are within the scope of the invention and form different embodiments, as will be understood by those skilled in the art. For example, any combination of any of the claimed embodiments may be used in the following claims.

[0053] Numerous specific details are described herein. However, it is understood that embodiments of the present invention may be carried out without these specific details. In other examples, well-known methods, structures, and techniques are not shown in detail so as not to obscure the understanding of this description.

[0054] In embodiments of the present invention, when referring to a "position sensing system," it refers to a system comprising components such as a magnetic structure and sensor devices. The sensor devices include sensors for detecting parameters or sets of parameters linked to the position of a moving target. The moving target provides relative movement between the structure and the sensors. These sensors may include sensing elements that provide signals (e.g., electrical signals) proportional to one or more detected parameters. The parameters may be, for example, components of a magnetic field. Thus, the position sensing system provides a signal that can be processed to obtain the position of the target. These signals can be processed by a processor, such as a microelectronic processor, a monolithic integrated microprocessor, etc. In the framework of the present invention, a position sensor may be defined as a position sensing system coupled with a processor for processing the signals of the system.

[0055] The present invention relates to a position sensing system for measuring the position of a target. Figure 1 shows a prior art position sensor 10, which includes one or more magnetic field sensors integrated into a chip 11 and a magnetic structure 12 that forms a sensing system 13. One of the sensors or structures moves with the target, while the other remains stationary. In the exemplary sensor 10 of Figure 1, the target is an axle 20 that rotates around its axis 21. The magnetic structure 12 (such as a disk) is mounted on the axle 20, which rotates with it, while the chip 11 is stationary. For example, it may be mounted on a housing (not shown). The relative position between the sensor and the structure can be measured by measuring the magnetic field generated by the magnetic structure 12 and the change in the field at the position of the sensor chip 11. The sensor can measure magnetic flux indicating not only the polarization of the field (north or south) but also how close the position is to the center of a particular pole or how close it is to the boundary with another pole. The sensor may include several sensing elements for measuring different magnetic components of the vector field, thereby improving positioning. The signal from the sensor chip 11 can be processed by the processor 14. The processor 14 can calculate the position of the magnet based on the field sensed at the position of the sensor chip 11.

[0056] This disclosure can be applied to a moving magnetic structure relative to a fixed sensor, or to a moving sensor relative to a static magnetic structure and magnetic structure.

[0057] For example, in the case of a sensing system for sensing angular position, a conventional rotary encoder having a simple dipole magnet and a magnetic sensing element can provide an absolute angular position because both the direction and value of the field are measured by the magnetic sensing element, and these same parameter configurations are repeated for each full rotation. Therefore, the measurement can obtain an accurate angle within one rotation (360°).

[0058] However, the resolution of state-of-the-art position sensors is limited to 0.02°, or 14 bits, and the angular accuracy over temperature, including temperature drift, signal-to-noise ratio, and positioning error, is approximately 0.3°. This limitation is given by the relative mechanical positioning between the magnet and the magnetic sensor, and the signal-to-noise ratio. The use of multipole magnets containing multiple dipoles (e.g., multiple dipoles, each having a North Pole and a South Pole) is a usable solution to improve resolution and angular accuracy. In the following text, multipole magnets will simply be referred to as "multipole". In a multipole, each dipole covers a portion of the structure (e.g., a portion of a full 360° rotation), making the field more variable with motion and thus increasing the accuracy of the magnetic sensor. In this way, if the field strength of both signals is maintained, the resolution of accuracy can be directly improved by the number of pole pairs applied. Thus, in the case of eight pole pairs, the accuracy can be improved eightfold.

[0059] On the other hand, using a multi-pole approach results in the loss of direct information regarding absolute position because the pole pairs are repeated for each segment. While angles are accurately measured within a given segment or angular sector (for example, a 45° sector in the case of 8 pole pairs), the angular sector cannot be identified from the multi-pole approach alone.

[0060] To rectify this problem, existing systems use a composite magnetic structure formed by two magnetic tracks. As used herein, the term “track” as part of a magnetic source typically refers to a ring-shaped, annular, or cylindrical object when speaking of angular position sensor systems, and to a beam-shaped object when speaking of linear position sensor systems.

[0061] The magnetic structure includes a first track, i.e., the master track, and a second track, also called the nonius track. The master track is a multipole having a predetermined number of dipoles, while the nonius track is a multipole having a different number of pole pairs than the master track, usually fewer pole pairs (since precision is not as critical as with the master track, this simplifies the design). The field generated by each track is sensed by a corresponding magnetic sensor. By combining the measured signals, the angular position within a single 360° rotation can be obtained. The number of pole pairs in each track and their difference can be adapted to optimize the calculation of the angular position. For example, given that the master track has n pole pairs, the nonius track usually has n-1 pole pairs, but in common designs, and in some embodiments of the present invention, it has two or more dipoles. It should be noted that the nonius track and the master track contain substantially the same type of magnetic material of substantially the same size, and therefore the bundles are substantially the same. The difference in field intensity or flux sensed by the first and second sensors is due to the different relative positions of the poles along the magnetic structure, resulting from the different number of poles in the master track and nonius track. Therefore, in the prior art, the pole fluxes in the master track and nonius track are substantially the same.

[0062] Figure 2 shows an example of these tracks. The upper magnetic source 30 has a structure that includes two concentric tracks located in a single plane for angular position sensors. The magnetic sensor device 31 can be positioned above or below that plane. In the example, the first track 32 is formed by an outer ring having five pole pairs, and the second track 33 is formed by an inner ring having four pole pairs. These rings are preferably magnetized in the axial direction. When there is relative rotational motion between the sensor and the source 30, the sensor device 31 senses eight poles by the inner track sensor and ten poles by the outer track sensor for each rotation.

[0063] The central figure shows a magnetic structure 40 comprising two cylindrical tracks 42, 43 having the same radius, and a sensor device 41 positioned as a satellite and movable around these cylindrical tracks (or the cylinder rotates around its center perpendicular to the axial direction A, with the sensor device 41 remaining fixed).

[0064] The bottom figure shows a magnetic structure 50 for a linear position sensor, comprising a magnetic sensor device 51 and two parallel linear tracks 52, 53 located in a single plane, the sensor device 51 positioned above or below the plane. The first track 52 may be formed by a first multipole magnet having five pole pairs, and the second track 53 may be formed by a second multipole magnet having four pole pairs. These magnets are preferably magnetized in the height direction H. The sensing system senses five north poles and five south poles for the first track and four north poles and four south poles for the second track when there is relative motion between the magnetic sensing system and the magnetic structure along the structure over the longitudinal direction L, as described above.

[0065] As described above, the magnetic sensor device includes first and second sensors for the corresponding track, which provide measurement of the magnetic field in at least two different directions. For example, each sensor is adapted to provide measurement of the magnetic field in at least two different directions. For example, each sensor device comprises at least two magnetic sensing elements, the element of the first sensor is configured to measure at least two first orthogonal magnetic field components (typically referred to as By1, Bz1) at a first sensor location (P1) on a first magnetic track, and the element of the second sensor is configured to measure at least two second orthogonal magnetic field components (typically referred to as By2, Bz2) at a second sensor location (P2).

[0066] The following describes several magnetic sensor devices with reference to Figures 3 to 10. Note that the Z-direction follows the direction from the sensor to the magnetic structure. This corresponds to the axial direction in coplanar angular magnetic structures and the radial direction in stacked cylindrical magnetic structures.

[0067] Figure 3 shows a schematic diagram of a sensor device 820a having a first magnetic sensor and a second magnetic sensor at locations P1 and P2 separated by a predefined distance Δx along the X-axis. Each sensor comprises four horizontal magnetic sensing elements, such as Hall elements H1-H4, positioned near the periphery of integrated flux concentrators IMC1 and IMC2. Three orthogonal magnetic field components, Bx, By, and Bz, can be measured at each location P1 and P2, as described in more detail in publication EP3650816A1. The components are obtained from the difference or sum of signals from different elements (e.g., Bx1 is proportional to the difference of signals H1-H3). Thus, the sensor device 820a has eight magnetic sensing elements that can measure two sets of three orthogonal magnetic field components, namely (Bx1, By1, Bz1) at the first sensor location P1 and (Bx2, By2, Bz2) at the second sensor location P2.

[0068] Figure 4 shows another sensor device, each comprising two magnetic sensors spaced apart by a predefined distance Δx, with each sensor containing one horizontal Hall sensing element (for measuring Bz) and two vertical Hall sensing elements (one for measuring Bx and one for measuring By). Thus, the magnetic sensor device 820b can also measure three orthogonal magnetic field components, namely (Bx1, By1, Bz1) at the first sensor position P1 and (Bx2, By2, Bz2) at the second sensor position P2.

[0069] The sensor device in Figure 5 also includes two sensors spaced apart by a predefined distance Δx, and each sensor includes a structure comprising only two horizontal Hall elements positioned on either side of the IMC disk and on a virtual line perpendicular to the X-axis. Each sensor structure can measure two orthogonal components By and Bz at each of the sensor locations P1 and P2. This sensor device advantageously requires only four horizontal Hall elements instead of eight.

[0070] Figure 6 shows another sensor device comprising two magnetic sensor structures spaced apart over a predefined distance Δx, each sensor structure comprising one horizontal Hall element and one vertical Hall element. Each sensor structure can measure two orthogonal components By and Bz. Since it does not require an integrated flux concentrator, it may be easier to manufacture.

[0071] Since the absolute position can be obtained using two orthogonal components, these types of sensors that provide two orthogonal components are sufficient.

[0072] Figure 7 shows a modified version of Figure 3, and Figure 8 shows a modified version of Figure 4. The sensor devices in Figures 7 and 8 each have four sensors spaced apart in the X and Y directions instead of just two sensors. These devices can measure three orthogonal components (Bx1, By1, Bz1) at P1 and another three orthogonal components (Bx2, By2, Bz2) at P2, as well as determine the spatial gradients of Bx, By, and Bz at the two sensor locations P1 and P2 as dBx / dy, dBBy / dy, and dBz / dy.

[0073] Although the setup is more complex, gradient signals are useful because they are very insensitive to external disturbances, and therefore the overall angular position is also very insensitive to external disturbances.

[0074] Next, the gradient signals dBy / dy and dBz / dy can be converted into two sets of orthogonal signals using a relatively small number of coefficients, e.g., a set of linear equations or polynomials with predefined coefficients, which can be determined, for example, by simulation or by measurement after assembly. The coefficients may be stored in non-volatile memory, e.g., in a processing unit such as a microelectronic processor. Then, based on the arctangent functions of the orthogonal signals, the first angle α1 with respect to the inner ring and the second angle α2 with respect to the second ring can be calculated.

[0075] It should be noted that obtaining a gradient signal is optional. For example, in Figures 3 to 6, the two components (e.g., By and Bz) may be orthogonal, and a gradient signal is not necessary.

[0076] Figure 9 is a simplified version of the sensor device in Figure 7, in which the X-direction component and gradient dBx / dy are not obtained for each sensor. This is similar to the sensor device in Figure 5, in which the magnetic field gradient signals dBBy / dy and dBz / dy can be further measured. Similarly, Figure 10 is a simplified version of the sensor device in Figure 8, in which the X-direction component and gradient dBx / dy are not obtained for each sensor. This is similar to the sensor device in Figure 6, in which the magnetic field gradient signals dBBy / dy and dBz / dy can be further measured.

[0077] Functionally speaking, the sensor devices in Figures 3, 5, 7, and 9 are similar to the sensor devices in Figures 4, 6, 8, and 10, respectively.

[0078] The multi-track concept has the drawback of significant overlap (or crosstalk) between the magnetic fields generated by the first and second tracks. Crosstalk is low in the direction established between the magnetic structure and the sensor, i.e., the component parallel to the Z-direction, but is typically much higher in the component of the field perpendicular to the Z-direction. To address this, prior art tracks and sensor positions must be sufficiently spaced apart to allow individual readings, enabling each sensor to obtain signals from its corresponding track with low crosstalk. This may require the use of several sensor platforms or expensive, large semiconductor chips. Alternatively, crosstalk can be compensated for computationally.

[0079] Signal processing will be explained in more detail in the following example. Generally speaking, each sensor is fitted to measure field components with different directions, for example, two orthogonal field components of the field near each track. Thus, four signals are obtained from the field (two from each sensor position), but readings from adjacent sensors on each track are adversely affected by crosstalk from other tracks. For mathematical correction, it is necessary to solve a linear regression problem, which can provide two orthogonal components for each track. From these, the master angle and nonius angle can be obtained, which are then combined again to provide the uncalibrated absolute angle. Final calibration may be provided to eliminate nonlinearities such as mechanical misalignment or defects in the magnet.

[0080] However, this method involves complex data processing. This is because the master angle and nonius angle can only be reconstructed by a continuous linear combination of all four input signals. Furthermore, the coefficients used for the master angle are only valid at the exact calibration position. Even a slight misalignment will result in an error in the calibrated angle.

[0081] The present invention provides a system, sensor, and position sensing method that reduces crosstalk between the field generated by a master track and the field generated by a nonius track. This is achieved without the need to separate the sensing elements, thereby allowing the magnetic sensing system to fit on a fairly small chip and reducing costs. This is achieved by adapting the magnetic structure, in which the master track generates a magnetic field that is much stronger (e.g., at least twice as strong) than the nonius track. Thus, the first sensor can detect the field generated by the stronger first magnetic track, while downplaying the contribution of the weaker second magnetic track to the magnetic field detected by the first sensor. To determine a small angle, once the nonius position is obtained, it is not necessary to use four input signals in a linear combination to obtain the small angle, so the sensing becomes less sensitive to positional deviations. Complex calculations are not required during motion and may only be required when the sensing system is "activated".

[0082] Magnetic structures in which the master track generates a much stronger field than the nonius track can be realized in different ways. The poles of the master track may be physically larger. However, the present invention is not limited thereto, and the master track and nonius track may be of similar size (as in the structure shown in Figure 2), but the poles of the master track may be made of a different magnetic material than those of the nonius track (or both the size and material of the poles may be different).

[0083] In a first aspect, the present invention provides a sensing system comprising a magnetic structure having a master track and a nonius track, and respective sensors for measuring the field proximal to each track. The magnetic structure is adapted such that the first sensor primarily senses the magnetic field of the master track, and therefore excluding the field from the nonius track from consideration does not affect the accuracy of the measurement. At least two sensors can be provided within the same sensor chip. The magnetic structure is not rotationally symmetric over 360 degrees (in other words, it has 1x rotational symmetry, so the fields are the same only after a 360-degree rotation). For example, the master track and the nonius track have different numbers of poles so that the fields have 1x symmetry, and typically the master track has more poles than the nonius track, e.g., one more pole.

[0084] In some embodiments, each sensor is adapted to provide a measurement of the orthogonal component of the magnetic field, as described above. In some embodiments, at least two sensors may be included in any of the magnetic sensor devices described with reference to Figures 3 to 10. These figures illustrate various examples of sensor devices that may be used in embodiments of the present invention, but the present invention is not limited thereto, and other sensor structures, such as sensor structures including magnetoresistive elements, may also be used.

[0085] The predefined distance Δx between sensors can be a value equal to approximately 2.0 mm, for example, in the range of approximately 1.0 mm to approximately 3.0 mm, for example, approximately 1.5 mm to approximately 2.5 mm. The predefined distance Δy between two pairs of sensors can be a value in the range of approximately 0.5 mm to approximately 3.0 mm. As mentioned above, Δy (directed in the circumferential direction of the magnetic source) may be greater than or less than Δx (directed in the radial direction of the magnetic source).

[0086] Because the master track provides a magnetic field that is, for example, two, three, or even five or ten times stronger than the nonius track, the magnetic structure of the sensing system allows for a better and simpler approach. This reduces crosstalk at the first sensor (at position P1 facing the master track).

[0087] The relative positioning of the first and second magnetic sensors can be optimized to reduce crosstalk, given the constraint that there is a small distance between these magnetic sensors, for example, that both sensors are provided on the same sensor device, e.g., on a chip. Generally, the distance between the first sensor and the nonius track must be greater than the distance between the second sensor and the nonius track.

[0088] In some embodiments, the first sensor is closer to the master track than to the nonius track. In some embodiments of the present invention, the upper projection of the first sensor overlaps with the master track, and the second sensor is at least the same distance from both, preferably closer to the nonius track than to the master track. The upper projection of the second sensor may overlap with the nonius track, or it may overlap with the gap of nonmagnetic material between the master track and the nonius track. The present invention is not limited to these configurations, and the upper projection of the second sensor may overlap with the master track. In some embodiments, the upper projection at the midpoint between the first and second sensors does not overlap with the nonius track.

[0089] As shown below, a position sensor having such a sensing system provides position sensing with a low computational load during measurement.

[0090] In some embodiments, each magnetic dipole in the master track provides a magnetic field whose measured component is at least twice as high as each of the magnetic dipoles in the nonius track.

[0091] The maximum value of the magnetic field, for example, the norm of the magnetic flux, may be compared for each track at substantially the same location relative to other tracks, for example, above the center of the magnetic pole and above the centerline of the track in a similar air gap (where Bz is maximum), or between two opposite poles above the centerline of the track in a similar air gap (where Bx is maximum). Alternatively, the maximum value of the norm of the magnetic flux at any location on each track in a similar air gap may also be considered. The fact that the magnetic field of the master track is large (at least twice as large) depends on the magnetic track itself, not on the arrangement of sensors or the like, but on the size of the poles, the magnetic material of the poles, or both. In some embodiments, the air gap may be at least 0.3 mm and up to 5 mm.

[0092] For example, the field of each track can be compared at the opposite sensor location. The position P1 of the first sensor is farther from the nonius than the position P2 of the second sensor. The magnetic flux generated from the nonius track at the position P1 of the first sensor may be at least half to one-tenth, e.g., at least half, or one-third, or one-quarter, or one-fifth, or one-sixth, or one-tenth, of the magnetic flux generated from the master track at the position P2 of the second sensor. In contrast, in the prior art, these values ​​are substantially equal. The effect is that crosstalk is reduced at the first position P1, even though it may increase at the second position P2. The surprising effect is that the overall determination of absolute position is improved, rather than the changes in crosstalk canceling each other out or worsening the determination of absolute position.

[0093] The present invention can be applied to linear or rotatable systems with appropriate adaptation. The details of the present invention will be described below with reference to a sensing system adapted to measure the angular position of a rotating system. For example, a master track and a nonius track are concentric tracks that can rotate around a common axis of rotation, so that the position of a rotating system, such as the angular position of a rotor, can be obtained.

[0094] In some embodiments, the master track and nonius track are rectangular toroids.

[0095] In some embodiments, the master track and nonius track are coplanar tracks magnetized in the axial direction. Sensors can be placed above or below the tracks in a plane parallel to the tracks, and therefore the Z component of the field is axial. For example, a sensor chip may include all sensors, and for example, the sensors may be monolithically integrated with chips parallel to the tracks. In this way, the rotational motion of the tracks relative to the sensors is detected as a changing magnetic field and its direction.

[0096] In particular, nonius tracks are usually smaller (with fewer pole pairs) than master tracks, and for practical reasons, they may be surrounded by master tracks.

[0097] As mentioned above, the master track provides a much higher magnetic field than the nonius track, for example, twice as large, for example, three or six times larger, maximum magnetic flux density for at least two components of the field, for example, two orthogonal components of the field. In some embodiments, the master track is made of a magnetic material having a greater magnetization than the nonius track. Many combinations can be envisioned. For example, neodymium-based magnets for the master track together with ferrite magnets in the nonius. In some embodiments, the two tracks may include neodymium-based alloys having different content of magnetic material. For example, the first track may contain a high or nearly exclusive content of FeNdB, while the second track contains FeNdB in a plastic matrix (also called a plastic junction magnet), thus reducing the content of magnetic material and ultimately the strength of the second track. The configuration of the magnetic structure may be as shown in the embodiment in Figure 2, in which the magnetic material of the poles is adapted so that the poles in the master track are much stronger (providing higher magnetic flux) than the poles in the nonius track.

[0098] Alternatively, the relative size and geometric shape of the magnets may be adapted to obtain the desired effect. For example, the master track may include magnets that are larger than those of the nonius track in at least one dimension. For example, as shown in the embodiment of the present invention in Figure 11, the tracks 101 and 102 of the magnetic structure 100 may have the same thickness and be made of the same material, which provides a mechanical advantage in a rotatable system (e.g., a uniform distribution when the magnetic structure is in motion), but the first track or master track 101 has a width at least twice as large as the width of the nonius track 102 in the same plane, for example, three times as large, for example, at least six times as large as the width of the nonius in the same plane. The present invention is not limited thereto, and both the shape, size and material of the poles of the master track may differ from those of the poles of the nonius track.

[0099] Figure 11 shows a master track 101 having eight pole pairs 103, each black zone being either a north or south pole. The nonius track 102 has seven pole pairs 104, and its magnets are much smaller than those of the master track. As the magnetic structure rotates around its center in a plane perpendicular to axis A, sensors at adjacent positions P1 and P2 on the master track and nonius track receive signals from the pole pairs 103 of the master track 101 and the pole pairs 104 of the nonius track 102, respectively. For example, the position P1 of the first sensor may overlap with the first track. For example, the position P2 of the second sensor may not overlap with the second track, and may, for example, traverse the adjacent zone between the first and second tracks, or overlap with the code-free area 108, as shown in Figure 11. It can be at least the same distance from both tracks and closer to the nonius track. The position P2 of the second sensor may overlap with the nonius track. Position P2 may also overlap with the master track. This is not limited to the planar geometry of Figure 11, but is not limited to any other magnetic structure geometry according to embodiments of the present invention. Note that the direction of overlap follows the distance to the magnetic structure of the corresponding sensor. In the case of Figure 11, the overlap is on the top view.

[0100] Since the magnet is much larger than the master track, the signal from the magnet (pole pair 104) in the nonius track can be excluded from consideration. The magnetic flux density of the axial and tangential components sensed by the sensor, for example, the maximum magnetic flux density of the above components, or, as described above, the field of the master track at position P2 of the second sensor compared to the field of the nonius track at position P1 of the first sensor, may be twice as large for the master track as for the nonius track. This can be applied to other configurations of the magnetic track and different components of the field.

[0101] For example, the first track has an area that is five times larger than the second track, for example, twenty times larger, for example, ten times larger. In general, the first track may be, for example, five to fifty times larger than the second track, for example, for ten to thirty times larger. Figure 12 is a top view of the magnetic structure of Figure 11 with specific measurements. However, other parameters, dimensions, and geometric shapes can be used. A sensor device 105 is shown, which is positioned to obtain a large signal from the master track with a first sensor and a second sensor positioned at position P2 such that the Z direction does not cross the master track.

[0102] The present invention is not limited to coplanar settings. For example, as shown in the embodiment of Figure 13, a cylindrical setting can be used, where the tracks of structure 200 are rings stacked in the axial direction (A). For example, the thickness (in the axial direction) of the master track 201 may be greater than the thickness of the nonius track 202. As described above, the dimensions may be adjusted to obtain a desired ratio of the magnetic fields generated by the tracks. For example, the magnetic material of the master track may be stronger than the nonius magnet, particularly with respect to the relevant component for the sensor device 205, at a higher maximum magnetic flux density. The sensor device 205 is positioned to sense around the tracks, with the first sensor near the master track 201 and the second sensor further away from the master track 201 and near the nonius track 202. Similar to Figure 11, the first sensor may overlap with the master track (in the side view, according to the distance between the sensor device 205 and the magnetic structure 200 in the case of Figure 13, which is radial in this case), and the second sensor may be on the code-free area or at the same distance from both tracks, preferably closer to the nonius track (e.g., overlapping with the nonius track). This positioning of the sensor devices on the side of the sensing system may be desirable under certain spatial constraints.

[0103] Furthermore, Figure 14 shows an exemplary embodiment of a linear sensing system for linear position measurement, in which the magnetic structure 300 comprises parallel first linear tracks 301 and second linear tracks 302, and the dipole distribution and sensor device 305 are positioned as defined with reference to the bottom drawing of Figure 2.

[0104] In these diagrams, the track width of the composite magnetic structure is defined by the radial direction R for coplanar tracks, by the axial direction A for stacked cylindrical tracks, and by the transverse direction T for linear tracks.

[0105] In the embodiments of Figures 11, 13, and 14, to illustrate the required magnetic fields and their ratios for the master track and nonius track, the width of the master track is at least twice, for example, at least three times, for example, six times greater than the width of the nonius track. However, as stated above, the present invention is not limited thereto, and the magnetic material of the master track may be adapted or other geometric shapes (e.g., different thicknesses) may be provided to provide a desired configuration of the magnetic field.

[0106] In all these examples, the relative position between the first sensor and the magnetic structure is measured. For example, a moving target whose position is measured moves in conjunction with the first and second tracks. For example, the moving target may be attached to tracks fixed to each other and / or to the moving target, and the magnetic sensing system is fixed in a manner similar to the system in Figure 1 (replacing the magnetic structure 12 and sensor device or chip 11 with the sensing system according to an embodiment of the present invention). Alternatively, the magnetic structure may be stationary, and the magnetic sensing system moves in conjunction with the target, for example, attached to the target. For example, it may be a chip attached to the target. In either case, the master track and nonius track do not move relative to each other. In embodiments of the present invention, the magnetic structure is a magnetic piece to which the tracks are fixed to each other. In some embodiments of the present invention, the structure includes a gap between the first and second tracks. The gap may be filled with a non-magnetic material. The presence of the gap reduces crosstalk between the magnetic structures.

[0107] The gap can be defined as the shortest distance between the sensor and the track, for example, the plane containing the track surface. This plane may be tangential to the curved surface in the cylindrical configuration of Figure 13, or, in the case of the planar track in Figures 11 and 14, the plane of the track facing the sensor. Since the system is arranged so that the sensors are parallel to the plane containing the track surface in the same plane, the gaps for all sensors may be substantially the same. The gaps may range from about 0.3 mm to about 5.0 mm, for example, from 0.8 mm to 3 mm.

[0108] In a further embodiment, the present invention provides a position sensor including a position sensing element according to an embodiment of the first embodiment of the present invention. The position sensor further comprises processing means, such as a processing unit or processor, which can be connected to a sensing system. For example, the processor may be an external module that can be connected to or is connected to the signal output section of the magnetic sensor. The processor may be included as an integrated part with the magnetic sensor, and for example, the magnetic sensor and processor may be monolithically integrated on the same chip or the like. However, this is not necessary, and processing may be performed outside the sensor device, for example, physically outside the sensing system, by an external processor, microprocessor, or microcontroller.

[0109] Figure 12 shows the above-described position sensor 400 according to an embodiment of the present invention, which includes a sensing structure and processing means 106 adapted to process signals from a sensor device 105 (e.g., a sensor chip). The processing means may be a processor, such as a microelectronic processor connected to the sensor of the sensor device 105, which may include, for example, computing power, programmability, memory (e.g., for a lookup table), etc. The processing means 106 may be a separate module or may be monolithically integrated with the sensor device 105.

[0110] In some embodiments of the present invention, the processing unit may include connections for an output unit 107, such as a memory, display, or interface. For example, the output unit 107 may include a controller coupled to or connected to the processing means 106, so that the controller can receive signals from the processor and control a device accordingly, for example, the power supply to a motor moving a target to which a magnetic structure 100 is attached can be controlled according to feedback from a position sensor installed in the motor. However, the present invention is applicable to other functions and devices.

[0111] In some embodiments of the present invention, the processing means 106 (e.g., processing unit) may also include internal memory and / or connections for acquiring information from a table (e.g., LUT) to calibrate a position sensor, for example.

[0112] In some embodiments, a processing unit (e.g., a processor) may be adapted to perform calculations using the measurements of a first and a second sensor when the sensing system is started, for example, when the sensors of the sensing system are powered on. This yields a first absolute position. After the sensors are started, the processor may then be adapted to process the signal from the first sensor and exclude the signal from the second sensor. Using the resulting processed signal, the position information obtained at startup is updated, and thus a subsequent absolute position is provided. The processor may be adapted to repeat this process periodically, processing only the signal from the first sensor (and thus excluding the signal from the second sensor from the nonius track), updating the previously obtained absolute position information, and thus the absolute position is updated with each periodic measurement. The complex calculations using the inputs from both sensors need to be performed only once, which is advantageous when the position sensors are started (or activated).

[0113] The processor includes contacts or inputs for receiving signals from the first and second sensors, and processes these signals to provide a position sensor. Signal processing may be performed according to the method described below.

[0114] In a further embodiment, a method for position measurement is provided. As described above, measuring the motion of a target involves linking the motion to be measured to the relative motion of a magnetic structure including a first multipole magnetic track and a second multipole magnetic track with respect to a first sensor and a second sensor. The method may include providing a master track in which the magnetic field flux is at least twice that of the magnetic field flux generated by the nonius. The method includes reading the magnetic field at a first position adjacent to the first track (or master track) using the first sensor, thereby obtaining a first signal. For example, the first sensor may be placed closer to the master track than to the nonius track. The method includes reading the magnetic field at a second position, the second position not overlapping the master track, and for example, the second position is adjacent to the second track (or nonius track) using a second sensor, thereby obtaining a second signal. The second sensor may be placed closer to the nonius track than to the master track.

[0115] The method may include using a magnetic sensor device, for example, a sensor chip including a first sensor and a second sensor. The method may include using a first track and a second track having different numbers of poles and moving together in conjunction (both having the same speed and direction of motion). In some embodiments, the method may include using a sensing system according to a first aspect of the present invention and processing the sensor signals in a processor. The method step including signal processing may be performed algorithmically within the processor.

[0116] The method includes using signals from a first sensor and a second sensor to obtain quadrant information, or in other words, information relating to which division of the target (e.g., which division of 360°, e.g., which quadrant of the eight 45° quadrants for an eight-dipole multipole) is facing the sensor. This provides coarse information about the approximate position of the magnetic structure. The method also includes using signals from only the first sensor to obtain precise positions (e.g., angles) across the quadrants. By combining the coarse information and the precise position information, the absolute position (e.g., absolute angle) of the magnetic structure can be accurately obtained.

[0117] Figure 15 shows a signal processing scheme including a master track and a nonius track. The magnetic components in the direction between the magnetic structure and the sensor, and the orthogonal components, are measured at the sensor position. In this particular embodiment, it can be assumed that a coplanar magnetic structure is used, so the axial component Mx and the tangential component Mt are sensed. The axial and tangential signals are provided by at least two sensing elements adapted to sense the axial and tangential components of the field, respectively.

[0118] The second sensor provides similar measurements (signals) at a position adjacent to the nonius track, closer to the nonius track than the master track. The similarity of the second sensor can be described as above for the axial signal Nx and the tangential signal Nt.

[0119] In the first example, since the sensors are integrated onto a single chip, for example, and located very close to each other, crosstalk can be considered between the magnetic field generated by the master track and the field generated by the nonius track at the location of any sensor. As mentioned earlier, it is possible to isolate the sensors, which can introduce new problems. It is economically advantageous when they are on a single chip, for example, a semiconductor chip.

[0120] The orthogonal components can be obtained from the measured values as a linear combination of different measured components (e.g., axial component and tangential component).

[0121] In embodiments of the present invention, the orthogonality between signals arises not from the orthogonal components or gradients, but from sensitive elements that are spaced at a specific distance. In some embodiments, the sensitive elements may match half of the corresponding pole distance. For example, when using two Bz sensing elements separated by half of the pole distance on the master track and another two Bz sensing elements spaced by half of the pole distance on the nonius track (a total of four Bz sensing elements), although a single component is being sensed (sensed at two locations instead of one), each pair of signals is orthogonal.

[0122] The master axial signal Mx and the master tangential signal Mt can be written as the field components B a_master , B t_master respectively, and the same can be done for the nonius signals Nx, Nt, written as B a_nonius , B t_nonius respectively.

[0123] 1) SIN(N pp * x)=A1*B t_master +A2 * B a_master +A3 * B t_nonius +A4 * B a_nonius 2) COS(N pp * x)=A5 * B t_master +A6 * B a_master +A7 * B t_nonius +A8 * B a_nonius 3) Sin((N pp -1) * x)=A9 * B t_master +A 10 * Ba_master +A 11 * B t_nonius +A 12 * B a_nonius 4) Cos((N pp -1) * x)=A 13 * B t_master +A 14 * B a_master +A 15 * B t_nonius +A 16 * B a_nonius The master track has a predetermined number of poles (Npp), and the nonius track has one fewer pole than the master track (Npp-1 poles). The two first couples 1) and 2) are the orthogonal components (Sin and Cos) of the master track, and these components include the crosstalk component of the second sensor (corresponding to the nonius track). The other two couples 3) and 4) are the components of the nonius track, which also include the measured value component from the first sensor due to the aforementioned crosstalk.

[0124] Therefore, the master track angle MALC is obtained from the linear combination LC of all four signals as components 1) and 2). The nonius angle NA is also obtained from the linear combination of all four signals as components 3) and 4). The master pole counter MPC is obtained by combining the master angle MA and the nonius angle NA. This provides information related to the sector of the structure in which the sensor receives the magnetic field. Combining MPC with MALC again yields the (uncalibrated) absolute position UA1, which in this case is, for example, an angle in the range of 0° to 360°. A final calibration CAL (e.g., using a lookup table LUT) can be applied to compensate for mechanical or magnetic irregularities, thus obtaining the absolute angle ABS. Linear regression operations and further calculations need to be performed periodically for each series of measurements obtained by the sensor, for example, every fraction of a second. This is a computationally intensive operation that slows down position detection. However, calibration and regression may only need to be performed once, so that the position information can be updated simply using the measurements provided by the first sensor. In other words, since the quadrants are initially obtained using the nonius position, it is possible to update the quadrant information after the relative motion has passed from one quadrant to another (which can be tracked by measurements on the first track).

[0125] In embodiments of the present invention, the magnetic configuration of the master track relative to the nonius track results in a signal from the first sensor with much lower crosstalk from the nonius magnetic field. This allows the measurement from the second sensor to be excluded from consideration. This simplification is made possible by the present invention and can be carried out in different ways by signal processing.

[0126] In some embodiments, linear regression is performed as previously shown to obtain the absolute angle. However, the present invention makes it possible to exclude the signal from a second sensor (nonius signal) from consideration in this calculation. For example, Figure 16 is a scheme of the method according to an embodiment of the present invention. As previously stated, the first sensor provides two orthogonal signals Mx, Mt corresponding to a field located closer to the master track than the nonius track. The second sensor provides two orthogonal signals Nx, Nt which may correspond to the same orientation as those of the first sensor. These are generated by a field located closer to the nonius track than the master track.

[0127] As mentioned above, a linear regression can be obtained from these signals, forming a system consisting of the four equations shown earlier.

[0128] However, in embodiments of the present invention, the calculation of the first two equations 1) and 2) for the master track does not require the use of measurements from the second sensor. This is indicated by the hatched arrows in Figure 16. In a particular algorithm having the equations 1), 2), 3), and 4) shown earlier, the coefficients A3, A4, A7, and A8 are set to 0.

[0129] In other words, using a structure like that of the embodiment of the present invention allows for the following simplifications. 1) Sin(N pp *x)=A1*B t_master +A2*B a_master 2) cos(N pp *x)=A5*B t_master +A6*B a_master 3)Sin((N pp -1) * x)=A9 * B t_master +A 10 * B a_master +A 11 * B t_nonius +A 12 *B a_nonius 4) Cos((N pp -1) * x)=A 13 * B t_master +A 14 * B a_master +A 15 * B t_nonius +A 16 * B a_nonius However, it should be noted that the linear regression of the second sensor can still be significantly affected by the much stronger crosstalk of the master track, and therefore the signal from the first sensor can be taken into consideration in the calculations (equations 3) and 4).

[0130] The master angle and nonius angle are obtained from sine and cosine by calculating their respective modified Arctan functions.

[0131] After solving the linear regression to obtain the master angle MA and nonius angle NA, the master pole counter MPC and the uncalibrated angle UA can be obtained: MPC=int(MA-NA-MA / N pp ) UA=MPC*360 / N pp +MA / N pp The final calibration CAL can be provided, for example, by calculation or using a LUT, to eliminate nonlinearities such as mechanical misalignment or defects in the magnet, and thus provide a calibrated absolute angle ABS. The number of points used in the LUT is 16*N as a useful trade-off between resolution and the number of calibration points. pp It is equal to . However, the number of other points, for example 4*N, pp ~32*N pp These can be used. These equations can be solved periodically.

[0132] While these specific equations and algorithms illustrate the effects of the present invention on signal processing, the present invention is not limited to these specific algorithms or specific orthogonal components of a field in providing a measure of position.

[0133] For example, instead of axial and transverse components, different components such as radial and transverse components can be used. This may be the case, for example, when stacked tracks as shown in Figure 13 are used. The components may also be in the height H and linear L directions for a linear embodiment of the sensing system, as shown in Figure 14. In this case, different algorithms may be used, but the reading from the second sensor can still be used only when measuring the position of a particular dipole in the track (master pole counter) and can be excluded when measuring the position relative to a particular dipole (absolute position).

[0134] In some embodiments, the master pole counter is obtained from a first sensor and a second sensor (startup master pole counter, MPCS) at startup of the sensing system. This can be done, for example, by following a simplified linear regression calculation as shown earlier. If this is done at startup, subsequent measurements only require the signal from the first sensor. The initial measurement allows for the determination of the sector (identifying the pole) whose field is being sensed by the first sensor, and the effect of nonius track can be negligible, so the operating master pole counter (MPCO) can be simply updated using further accurate measurements from the first sensor without having to recalculate the MPC from linear regression. As shown in Figure 16, it is not necessary to use the signal from the second sensor to update the MPCO, perhaps until the next startup, or to readjust the MPC after some rotation, for example, to re-determine or verify the location of the magnetic structure sector affecting the sensor.

[0135] In some embodiments, the activation of the sensing system is performed while the target is moving. For example, a device such as a motor (including the sensor of the present invention) may be rotating, and the method may be performed by obtaining a master angle and a nonius angle at activation (when the sensor is turned on) while the motor is operating. In some embodiments, the measurement of absolute position, including taking into account the signal from a second sensor, may be performed before the normal motion of the device begins, for example, before the engine starts moving.

[0136] This invention provides accurate measurements from a master track that define the overall measurement accuracy. Measurements from the nonius channel do not need to be as accurate, as they are used only to identify the absolute position. Measurements at a second position (using a second sensor for the nonius track) can accommodate some crosstalk from the master.

Claims

1. 1. A sensing system for sensing a position, comprising: a first magnetic track with a first number of multipoles for generating a magnetic field and a first sensor for sensing the magnetic field; a second magnetic track with a second number of multipoles different from the first number, said second magnetic track for generating a magnetic field, and a second sensor for sensing the magnetic field; the first magnetic track and the second magnetic track are cohesively fixed to each other to form a magnetic structure; A sensing system, wherein the first sensor is positioned in proximity to the first magnetic track, closer to the first magnetic track than the second magnetic track, the second sensor is positioned in proximity to the second magnetic track, the distance between the first sensor and the second magnetic track is greater than the distance between the second sensor and the second magnetic track, and the magnetic flux densities generated by the first magnetic track and the second magnetic track, respectively, on the centerlines of the first magnetic track and the second magnetic track at similar air gaps follow a ratio of 2 to 1 or greater.

2. The sensing system of claim 1 , wherein the tracks are concentric tracks rotatable about a common axis of rotation.

3. 3. The sensing system of claim 2, wherein the tracks are coplanar tracks, the second track is surrounded by the first track, the first track has a first predetermined width, and the second track has a second predetermined width, the first predetermined width being at least two times greater than the second predetermined width.

4. 3. The sensing system of claim 2, wherein the first track and the second track are stacked rings having the same outer radius, and the axially defined width of the first track is at least two times greater than the width of the second track.

5. The sensing system of any one of claims 1 to 4, wherein the first track is multipole having at least eight dipoles.

6. The sensing system of any one of claims 1 to 4, wherein the first sensor and the second sensor are adapted to sense different field components.

7. The sensing system according to any one of claims 1 to 4, wherein the first sensor and the second sensor are integrated on a single semiconductor chip.

8. 5. The sensing system of claim 1, further comprising signal processing means for processing a signal of the sensor, and further comprising a signal output section for providing an absolute position of the first track relative to the sensor.

9. The sensing system of claim 8 , wherein the processing means is adapted to calculate an initial position from measurements of the second sensor upon start-up of the sensing system.

10. The sensing system of claim 8 , wherein the processing means is adapted to obtain the position with measurement signals from the first sensor and the second sensor and to calibrate the position.

11. 5. A method of sensing position using the sensing system of claim 1, further comprising obtaining measurements of the first sensor and the second sensor, and calculating the position of the magnetic structure relative to the first sensor.

12. The method of claim 11 further comprising subsequently calibrating the results to compensate for mechanical misalignment.

13. 12. The method of claim 11, further comprising detecting the position of the first track by using the measurements of the first sensor and the second sensor to detect a dipole of the magnetic structure on which the sensors are placed, while ignoring the measurements of the second sensor to detect an absolute position of the first sensor with respect to the magnetic structure.

14. 14. The method of claim 13, wherein detecting the position and the absolute position of the dipole is performed upon activation of the sensor, and further comprises ignoring the signal of the second sensor in subsequent measurements after an initial position of the first track is detected by using the measurement of the first sensor to obtain the dipole of the magnetic structure on which the sensor is placed.

15. 12. The method of claim 11, further comprising detecting the position of the first track by performing a linear combination of the measurements of the first sensor and the second sensor to detect a dipole of the magnetic structure on which the sensor is placed, and by using the measurements of the first sensor and the second sensor to detect an absolute position of the first sensor with respect to the magnetic structure.

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