Methods and devices for using multiturn magnetic sensors with extended magnetic windows

Abstract

A method for recording a number of rotations with a multi-turn magnetic sensor using an extended magnetic window, the method comprising: Applying a magnetic field to the multi-turn magnetic sensor having a magnetic target, the magnetic field defining a magnetic field vector at the multi-turn magnetic sensor, the magnetic field vector pointing out of a region for which domain wall propagation is expected in the multi-turn magnetic sensor, and the magnetic field having a first strength at the multi-turn magnetic sensor below a range for which domain walls predictably propagate through the multi-turn magnetic sensor; while the magnetic field vector points out of the area, increasing the strength of the magnetic field with the magnetic target to a second strength at the multiturn magnetic sensor within the range for which domain walls predictably propagate through the multiturn magnetic sensor; and while the magnetic field has the second strength at the multi-turn magnetic sensor, adjusting the magnetic field with the magnetic target object such that the magnetic field vector points into the area to adjust a state of the multi-turn magnetic sensor.

Description

AREA OF REVELATION

[0001] The technology described relates to magnetic sensors and related systems and methods. GENERAL STATE OF THE ART

[0002] Rotary counters that can measure angles greater than 360° are used in a wide variety of applications and are often referred to as multiturn counters. One implementation of a multiturn counter uses the phenomenon of magnetoresistance, in which ferromagnetic layers are separated by a thin, non-magnetic film. A multiturn counter based on the phenomenon of magnetoresistance possesses several desirable properties. It may be desirable for the strength of the magnetic field generated by a rotating magnetic target and detected by the sensor to remain within a relatively narrow magnetic window. If the strength of the magnetic field is too low, the sensor may not be able to properly record the rotation of the magnetic target. Conversely, if the strength of the magnetic field is too high, the magnetic field can distort the data recorded by the sensor.In any case, the rotation count from the sensor can no longer be trusted. The difference between the smallest and largest acceptable magnetic field strength can be referred to as a magnetic window.

[0003] In various applications, it can be difficult to provide a magnetic target that delivers a magnetic field that remains within the magnetic window for all rotation angles of the target. For example, applications where the magnetic target cannot be placed at the end of a rotating shaft may involve impractically large magnetic windows.

[0004] US 2007 / 0205759 A1 discloses a bearing with an integrated rotation sensor. To provide a bearing with an integrated rotation sensor capable of detecting the rotational speed and the origin position without being influenced by an external magnetic field, the bearing comprises a rotatable ring, a magnetic encoder attached to the rotatable ring, and a stationary ring. The magnetic encoder includes an annular rotational speed detecting member having a plurality of alternating magnetic poles and an origin position detecting element axially disposed in a circumferential direction of the detecting member. Speed ​​and origin position sensors are attached to the stationary ring to respectively confront the rotational speed and origin position detecting elements.A magnetic recovery element is arranged in a peripheral portion of the magnetic encoder where it confronts the magnetic origin position sensor, the second component to be detected being excluded from the peripheral portion. BRIEF PRESENTATION OF REVELATION

[0005] The claimed subject matter is defined in the independent claims. Advantageous further developments are described in the dependent claims.

[0006] The innovations described in the claims each have multiple aspects, none of which is solely responsible for its desired attributes. Without limiting the scope of the claims, some salient features of this disclosure will now be briefly described.

[0007] One aspect of the present disclosure is a method for recording a number of rotations with a multi-turn magnetic sensor using an extended magnetic window. The method comprises: applying a magnetic field to the multi-turn magnetic sensor, wherein the magnetic field points out of a region for which domain wall propagation is expected in the multi-turn magnetic sensor, and wherein the magnetic field has a first strength below a region for which domain walls predictably propagate through the multi-turn magnetic sensor. The method comprises: while the magnetic field points out of the region, increasing the strength of the magnetic field to a second strength within the region for which domain walls predictably propagate through the multi-turn magnetic sensor, and while the magnetic field has the second strength, rotating orReversing the magnetic field such that the magnetic field vector points into the area to adjust a state of the multiturn magnetic sensor.

[0008] The method may comprise: applying the magnetic field to the multi-turn magnetic sensor having a magnetic target (magnetic target object) and rotating the magnetic target (magnetic target object) relative to the multi-turn magnetic sensor or linearly parallel translating the magnetic target (magnetic target object) relative to the multi-turn magnetic sensor.

[0009] The method may comprise applying, with an initialization magnet separate from the magnetic target and to the multi-turn magnetic sensor, an initialization magnetic field having a third strength that is within the range for which domain walls predictably propagate through the multi-turn magnetic sensor, and rotating the initialization magnetic field relative to the multi-turn magnetic sensor to create at least one domain wall in the multi-turn magnetic sensor.

[0010] The method may comprise: while the magnetic field points out of the region, reducing the magnetic field to a third strength below a region for which any propagation of domain walls by the multiturn magnetic sensor is expected.

[0011] Another aspect of the present disclosure is a multiturn magnetic sensing system with an extended magnetic window. The multiturn magnetic sensing system includes a multiturn magnetic sensor with magnetoresistive elements and configured to record a number of rotations of a magnetic field based on domain wall propagation by the multiturn magnetic sensor, and a magnetic target configured to move between a first position relative to the multiturn magnetic sensor and a second position relative to the multiturn magnetic sensor.The magnetic target object can be configured such that in the first position the magnetic target object is configured to apply the magnetic field with a first strength to the first multi-turn magnetic sensor, wherein the first strength is below a range for which domain walls predictably propagate through the multi-turn magnetic sensor, and in the second position the magnetic target object is configured to apply the magnetic field with a second strength to the multi-turn magnetic sensor, wherein the second strength is in the range for which domain walls predictably propagate through the multi-turn magnetic sensor.

[0012] The magnetic target object may comprise a first portion of magnetic material forming a first magnetic dipole and a second portion of the magnetic material forming a second magnetic dipole, the first magnetic dipole being inverted relative to the second magnetic dipole, the first and second portions of the magnetic material being arranged along a substantially circular circumference, and at least a portion of the first portion of the magnetic material being arranged at the second portion of the magnetic material.

[0013] When the magnetic target is in the first position, the second portion of the magnetic material may be disposed away from the multi-turn magnetic sensor. When the magnetic target is in the second position, the second portion of the magnetic material may be disposed near the multi-turn magnetic sensor.

[0014] The substantially circular perimeter of the magnetic material can define a circle with a center. The first magnetic dipole can be oriented such that the first magnetic dipole has a magnetic north pole pointing toward the center of the circle and a magnetic south pole pointing away from the center of the circle. The second magnetic dipole can be oriented such that the second magnetic dipole has a magnetic south pole pointing toward the center of the circle and a magnetic north pole pointing away from the center of the circle.

[0015] The substantially circular perimeter of the magnetic material may define a circle lying in a plane. The first magnetic dipole may be oriented such that the first magnetic dipole has a magnetic north pole pointing normal to the plane and a magnetic south pole pointing antinormal to the plane. The second magnetic dipole may be oriented such that the second magnetic dipole has a magnetic south pole pointing normal to the plane and a magnetic north pole pointing antinormal to the plane.

[0016] The magnetic target may comprise a ring having a substantially circular circumference, wherein the first and second portions of the magnetic material together span substantially the entire substantially circular circumference of the ring.

[0017] The magnetic target object may include a third portion of the magnetic material forming a third magnetic dipole, the third magnetic dipole being inverted relative to the second magnetic dipole, and the second portion of the magnetic material being disposed between the first and third portions of the magnetic material.

[0018] When the magnetic target is in the first position, the second portion of the magnetic material may be disposed away from the multi-turn magnetic sensor. When the magnetic target is in the second position, the second portion of the magnetic material may be disposed near the multi-turn magnetic sensor.

[0019] The magnetic target may comprise a straight magnetic target having an elongated direction and at least one pole pair magnetized perpendicular to the elongated direction. The pole pair may be closer to the multi-turn magnetic sensor when the magnetic target is in the first position than when the magnetic target is in the second position.

[0020] Another aspect of the present disclosure is a magnetic sensing system with an extended magnetic window.The magnetic sensing system comprises a magnetic sensor comprising magnetoresistive elements and configured to record position data based on domain wall propagation through the magnetic sensor and a magnetic target object arranged relative to the magnetic sensor such that in a first position relative to the magnetic sensor, the magnetic target object is configured to apply a magnetic field with a first strength to the magnetic sensor, wherein the first strength lies in a range for which domain walls propagate through the magnetic sensor with a non-zero probability of less than 95%, and in a second position relative to the magnetic sensor, the magnetic target object is configured to apply the magnetic field with a second strength to the magnetic sensor, wherein the second strength lies in a range for which domain walls predictably propagate through the magnetic sensor.

[0021] The magnetic target object may be arranged relative to the magnetic sensor such that in a third position relative to the magnetic sensor, the magnetic target object is configured to apply the magnetic field with a third strength to the magnetic sensor, wherein the third strength is in a range for which domain walls are not expected to propagate through the magnetic sensor.

[0022] The magnetic target may be formed in a ring and may have magnetic poles pointing radially inward toward a center of the ring and radially outward from the center of the ring.

[0023] The magnetic target object may be formed in a ring lying in a plane and having magnetic poles pointing normal to the plane of the ring and antinormal to the plane of the ring.

[0024] The magnetic target may comprise a straight magnetic target having an elongated direction and having magnetic poles pointing perpendicular to the elongated direction of the straight magnetic target.

[0025] For the purpose of summarizing the disclosure, certain aspects, advantages, and novel features of the innovations have been described herein. It should be understood that not all such advantages may necessarily be achieved according to a particular embodiment. Thus, the innovations may be embodied or practiced in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other advantages that may be taught or suggested herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] These drawings and the associated description herein are presented to illustrate specific embodiments and are not intended to be limiting. Fig. 1 shows an exemplary magnetic stripe layout diagram of a multiturn magnetic sensor with a corresponding circuit schematic diagram. Fig. Figure 2 shows an example magnetic stripe layout with explanatory symbols. Fig. 3 shows a multiturn magnetic sensor that can operate with an extended magnetic window. Fig. 4 shows an example of a magnetic target formed from a magnetic ring with a reversed pole pair and a magnetic sensor sensitive to magnetic fields from the magnetic target according to one embodiment. Fig. Figure 5A shows a graphical representation of the magnetic field strength of the multiturn magnetic sensor of Fig. 4 as a function of the angle of rotation of the magnetic target object of Fig. 4. Fig. Figure 5B shows a graphical representation of the magnetic field direction of the multiturn magnetic sensor of Fig. 4 as a function of the angle of rotation of the magnetic target object of Fig. 4. Fig. 6 shows an example of a magnetic target formed from a ring with magnetic poles and a magnetic sensor sensitive to magnetic fields from the magnetic target, according to one embodiment. Fig. Figure 7A shows a graphical representation of the magnetic field strength of the multiturn magnetic sensor of Fig. 6 as a function of the angle of rotation of the magnetic target object of Fig. 6. Fig. Figure 7B shows a graphical representation of the magnetic field direction of the multiturn magnetic sensor of Fig. 6 as a function of the angle of rotation of the magnetic target object of Fig. 6. Fig. 8 shows an example of a magnetic target formed from a magnetic ring with a reversed pole pair and configured for axial detection by a multi-turn magnetic sensor according to one embodiment. Fig. 9 shows an example of a magnetic target formed from a ring with magnetic poles and configured for axial detection by a multi-turn magnetic sensor according to one embodiment. Fig. 10 is a flowchart of an exemplary method for counting rotations of a magnetic target according to one embodiment. Fig. 11 is a flowchart of an example method for initializing a magnetic sensor having one or more domain walls, according to one embodiment. Fig. 12 shows an example of a straight magnetic target formed from a magnetic bar having at least one reversed pole pair according to one embodiment. Fig. 13 shows an example of a magnetic target formed from a straight target with magnetic pole pairs according to an embodiment. DETAILED DESCRIPTION

[0027] The following detailed description presents various descriptions of specific embodiments. However, the innovations described herein may be embodied in a variety of different ways, for example, as defined and covered by the claims. Reference is made throughout this description to the drawings, where like reference numerals may indicate identical or functionally similar elements. It should be understood that elements depicted in the figures are not necessarily drawn to scale. Rather, it should be understood that certain embodiments may include more elements than depicted in any one drawing and / or a subset of the elements depicted in a drawing. Furthermore, some embodiments may include any suitable combination of features from two or more drawings.

[0028] Aspects of the present disclosure relate to a magnetic sensing system comprising a multi-turn magnetic sensor and a magnetic target (magnetic target object). Domain walls may predictably extend through the multi-turn magnetic sensor when a first strength of a magnetic field generated by the magnetic target is within a range of magnetic field strengths. In a first position, the magnetic target may apply the magnetic field to the multi-turn sensor at the first magnetic field strength. The magnetic target may rotate from the first position to a second position. In the second position, the magnetic target may generate a magnetic field at a second magnetic field strength within a region for which domain wall propagation is not expected, wherein the second magnetic field strength is below the range of magnetic field strengths for which domain walls predictably propagate through the multi-turn magnetic sensor.The multiturn magnetic sensor can maintain a state while the magnetic target rotates from the first position to the second position and then to the first position. Accordingly, the magnetic sensing system can operate with magnetic field strengths that have a wider range than other magnetic sensing systems. Magnetic targets in the magnetic sensing systems discussed herein can have less magnetic material than other magnetic sensing systems. This can save space and cost.

[0029] The magnetic field sensing systems described herein can provide a compact and modular arrangement for measuring a rotation count in various applications. One exemplary application for the disclosed magnetic field sensors is measuring the rotation count of a steering column. In some embodiments, the disclosed magnetic field sensors can be used with magnetic targets whose operating strength can exceed the traditional magnetic windows of sensors while maintaining error-free operation of the sensors. Such arrangements can facilitate sensing a rotation count of a rotating shaft even when the magnetic sensor is not positioned at the end of the rotating shaft.

[0030] In some embodiments, a magnetic stripe having magnetic anisotropy is physically configured in the shape of a spiral. A domain wall generator coupled to one end of the magnetic stripe is configured to generate and transport one or more domain walls through the magnetic stripe according to the orientation of a rotating magnetic field. A drive circuit may activate a portion of the spiral (e.g., apply a voltage and / or current to it), and a sensing circuit may take an electromagnetic reading associated with the portion of the spiral. As such, the sensing circuit may sense a resistance of an isolated magnetoresistive element of the magnetic stripe. A control circuit may control a sequence in which different portions of the spiral may be energized and sensed by a sensing circuit.For example, the control circuit may control switches for selecting a particular magnetoresistive element of the spiral, for which the sensing circuit may detect a value indicative of the resistance. The sensing circuit may take a sequence of electrical readings from the various parts of the spiral associated with magnetic states of the various parts of the spiral. In some cases, the sensing circuit may perform a comparison of the electromagnetic readings. The output of the sensing circuit may be decoded to determine an accumulated rotational state of the magnetoresistive elements of the magnetic strip.

[0031] Fig. 1 shows an exemplary magnetic stripe layout 100 with a corresponding circuit schematic representation 150. Fig. Figure 1 shows a magnetic strip 101 with corners 105 and segments 103a-103n forming magnetoresistive elements R1-R14 arranged in series with each other, and a domain wall generator 107. The magnetoresistive elements can act as variable resistors that change resistance values ​​in response to a magnetic alignment condition. Fig. The magnetic stripe 101 shown in Figure 1 can be implemented in a multi-turn counter.

[0032] The magnetic stripe 101 may be a GMR (Giant Magnetoresistance) track, which is physically designed in the shape of a spiral. As shown in Fig. 1, such a spiral magnetic stripe 101 may have rounded corners 105 and segments 103a-103n. The magnetic stripe 101 may have a magnetic anisotropy, such as a high anisotropy, based on the material and cross-sectional dimensions of the magnetic stripe 101. The magnetic stripe 101 may store magnetic energy. A domain wall generator (DWG) 107 is coupled to one end of the magnetic stripe 101. The DWG 107 may have a magnetic anisotropy, such as a low anisotropy. The domain wall generator may generate domain walls in response to rotations in a magnetic field. The domain walls may be coupled onto the magnetic stripe 101.

[0033] The segments 103a-103n of the magnetic stripe 101 are shown as straight sides of the magnetic stripe 101 in the example of Fig. 1. The segments 103a-103n can have a variable resistance based on the magnetic domain of the segment. When the magnetic domain of a segment changes, the resistance of that segment can change. Accordingly, the segments 103a-103n can operate as magnetoresistive elements, also referred to herein as variable resistors R1-R14. The magnetoresistive elements R1-R14 can also function as a non-volatile magnetic memory that can be magnetically written to and electrically read from. The magnetoresistive elements R1-R14, as configured in the spiral magnetic stripe 101, are coupled to each other in series. A corresponding circuit schematic diagram 150 shows segments 103a-103n represented as corresponding magnetoresistive elements R1-R14 connected in series.

[0034] Fig. Figure 2 shows an exemplary magnetic stripe layout diagram 200 with explanatory symbols. The magnetic stripe 101 with magnetoresistive element segment equivalents R1-R14 of Fig. 1 is shown along with the DWG 107, an external magnetic field 201, an arrow 203 indicating a rotation of the external magnetic field 201, and a domain wall 213. Domain orientations 205, 207, 209, and 211 indicate an orientation of a domain within a segment of a magnetic stripe.

[0035] The DWG 107 can be influenced by the external magnetic field 201. When the external magnetic field 201 rotates, as indicated by the arrow 203, the DWG 107 can couple domain walls 213 through the magnetic stripe 101. The domain wall 213 can propagate through the segments as the magnetic field 201 rotates and the domain orientations 205, 207, 209, and 211 change. Although Fig. 2 shows the external magnetic field 201 at vertical positions for clarity, the magnetic field can point at any angle, such as a 45-degree angle, to the spiral corners.

[0036] The resistivity of segments of magnetic stripe 101 can be influenced by the domain orientation within a magnetic stripe segment. The domain orientation of each segment can cause that segment to have a high resistance value ("H" or "HR") or a low resistance value ("L" or "LR") depending on the segment's orientation. Vertically illustrated magnetic stripe segments with a domain orientation 205 have a higher resistivity than vertical magnetic stripe segments with a domain orientation 207, which have a low resistivity. Horizontally illustrated magnetic stripe segments with a domain orientation 213 have a higher resistivity than horizontal magnetic stripe segments with a domain orientation 211, which have a low resistivity. The magnetic stripe segments with domain orientations 205 and 213 can have comparable resistivity values.Analogously, the magnetic stripe segments with domain orientations 207 and 211 can have comparable resistance values.

[0037] The Fig. 1 and Fig. The examples shown in Figure 2 depict a spiral magnetic stripe 101 as an open spiral based on a quadrilateral. However, in some other embodiments, various polygonal or elliptical spiral configurations are possible. Furthermore, the spiral can be a closed spiral or a multilayer spiral with overlapping portions.

[0038] As discussed above, it may be desirable for the strength of the magnetic field generated by a rotating magnetic target and sensed by a multiturn magnetic sensor to remain within a relatively narrow magnetic window, referred to herein as a first magnetic window. The first magnetic window may comprise the range of magnetic field strengths for which domain walls predictably propagate through a multiturn magnetic sensor. As such, the first magnetic window may comprise magnetic fields with strengths at the multiturn magnetic sensor that are no stronger than a maximum magnetic field strength Hmax and no weaker than a minimum magnetic field strength for reliable domain wall propagation. If the strength of the magnetic field is too high (e.g., above the maximum magnetic field strength Hmax), the magnetic field may create new domain walls even without rotation of the magnetic field. This may confound the data recorded by the sensor.Conversely, if the magnetic field strength is too low (e.g., below a minimum magnetic field strength Hmin for reliable domain wall propagation), the domain walls may not propagate reliably, and the sensor may lose track of the number of rotations of the magnetic target. Thus, it may be desirable for the magnetic field strength to remain within the first magnetic window (e.g., between Hmin and Hmax) to ensure error-free operation.

[0039] The present disclosure provides multi-turn sensing systems that operate with magnetic fields that extend outside the first magnetic window while still providing error-free operation. As examples, multi-turn sensing systems provided in the present disclosure may operate with magnetic fields that may occasionally be within a second magnetic window and that may occasionally be within a third magnetic window.

[0040] The second magnetic window may contain the range of magnetic field strengths for which domain walls propagate through a multiturn magnetic sensor, but in an unreliable manner. If the magnetic field strength lies within a second magnetic window (e.g., between a minimum magnetic field strength Hmin for reliable domain wall propagation and a minimum magnetic field strength Hmin2 for domain wall propagation, where Hmin2 is smaller than Hmin), the domain walls may propagate with some probability (e.g., with a certainty or probability of less than 1, sometimes referred to as a certainty or probability of less than 95%).

[0041] The third magnetic window may have magnetic field strengths sufficiently weak that domain wall propagation is not expected to occur in the multiturn magnetic sensor. If the magnetic field strength is within the third magnetic window (e.g., below a minimum magnetic field strength Hmin2 for domain wall propagation), the domain walls should not propagate within the sensor, regardless of the magnetic field direction. The properties of the second and third magnetic windows can be used in forming a sensor that operates outside the first magnetic window (e.g., by ensuring that the magnetic field strength is within the first magnetic window during certain time periods).

[0042] Fig. 3 shows an exemplary multiturn magnetic sensor 300 that can be reliably operated with a magnetic target that creates a magnetic field strength at the sensor that is occasionally outside the magnetic window (e.g., outside a magnetic window in which domain walls predictably propagate through the multiturn magnetic sensor 300).

[0043] The external magnetic field 301 may fall within the second magnetic window (e.g., a magnetic window where domain wall propagation occurs, but with less than 100% probability) as long as the field direction remains within one of the four regions 302a, 302b, 302c, or 302d. In particular, if the direction of the external magnetic field 301 remains within one of the four regions 302a, 302b, 302c, and 302d, no domain wall propagation is expected. As such, the probability of domain wall propagation within the second magnetic window below 100% is acceptable (e.g., since domain wall propagation is not expected within these regions, the reliability of its propagation is irrelevant).Before entering the second magnetic window, the direction of the external magnetic field 301 should be within one of the four ranges 302a, 302b, 302c and 302d, and the direction should remain within the same range as long as the field strength is within the second magnetic window (e.g., between Hmin2 and Hmin).

[0044] Various properties of the magnetic windows of the magnetic sensor 300, such as the magnetic field strengths corresponding to a maximum magnetic field strength Hmax, a minimum magnetic field strength Hmin for reliable domain wall propagation, and a minimum magnetic field strength Hmin2 for domain wall propagation, can depend on the geometry of the magnetic sensor 300 and the materials forming the magnetic stripe. In particular, the thickness and width of the magnetic stripe, together with the materials forming the stripe, can serve to define the values ​​of Hmax, Hmin, and Hmin2. Various materials, such as iron and cobalt iron, can be used to form the magnetic stripe. By varying the selected material and / or the thickness and / or width of the magnetic stripe, the values ​​of Hmax, Hmin, and Hmin2 can be adjusted.Typical values ​​for the magnetic windows of the sensor 300 in a first implementation may include a maximum magnetic field strength Hmax of about 1000 oersteds and a minimum magnetic field strength Hmin for reliable domain wall propagation at about 700 oersteds. In a second implementation, the Hmax of the sensor 300 may be about 350 oersteds, the Hmin may be about 150 oersteds, and the minimum magnetic field strength Hmin2 for domain wall propagation may be about 50 oersteds. In some cases, the minimum magnetic field strength Hmin for reliable domain wall propagation may be about half the value of the maximum magnetic field strength Hmax, while the minimum magnetic field strength Hmin2 for domain wall propagation may be about 20% of the value of the maximum magnetic field strength Hmax.

[0045] The location, size, and even the number of regions 302a, 302b, 302c, and 302d in the magnetic sensor 300 where the field strength can drop out of the magnetic window may depend at least in part on the physical attributes of the magnetic stripe (e.g., the coil) forming the magnetic sensor 300, and may also depend on the materials forming the magnetic stripe (which, as discussed herein, may partially determine the properties of the magnetic windows). In some embodiments, the regions 302a, 302b, 302c, and 302d may each span approximately 60 degrees, with gaps between the regions spanning approximately 30 degrees. In some other embodiments, the gaps between the regions 302a, 302b, 302c, and 302d may span between 10 and 30 degrees.

[0046] Furthermore, the external magnetic field 301 can drop from the second magnetic window into the third magnetic window (e.g., a magnetic window below a minimum magnetic field strength Hmin2 for domain wall propagation, where domain wall propagation is not expected to occur). Within the third magnetic window, the direction of the external magnetic field 301 can rotate in any direction without changing the recorded data of the sensor 300. However, before adjusting the strength of the external magnetic field 301 from within the third magnetic window to within the second magnetic window, the magnetic field vector of the external magnetic field 301 should lie within one of the four regions 302a, 302b, 302c, and 302d.

[0047] In some embodiments, the direction of the external magnetic field 301 should point within the same one of regions 302a, 302b, 302c, and 302d when its strength increases into the second magnetic window as it did when its strength decreased from the second magnetic window. As an example, the magnetic field 301 may point somewhere within region 302a at a first time and have a strength within the second magnetic window. Then, at a second, later time, the magnetic field 301 may drop into the third magnetic window, and its direction may change without restriction. Finally, at a third, later time, the magnetic field 301 may increase back into the second magnetic window while its direction remains within region 302a.

[0048] In some other embodiments, the direction of the external magnetic field 301 may change from one of the regions 302a, 302b, 302c, and 302d to another while the field strength is within the third magnetic window. In other words, the strength of the external magnetic field 301 may drop from the second to the third magnetic window (while in one of the regions 302a, 302b, 302c, and 302d); may shift to another of the regions 302a, 302b, 302c, or 302d; or may then increase from the third to the second magnetic window while in the new region. In such embodiments, there may be a predictable relationship between the direction of the magnetic field 301 at the time it entered the third magnetic window and the direction of the magnetic field 301 when it returns to the second magnetic window.The predictable relationship may be determined based on the physical layout of sensor 300 and the rotating magnetic target. As one example, magnetic field 301 may point somewhere within region 302a at a first time, have an initial strength in the second magnetic window, and then decrease into the third magnetic window. Then, the direction of magnetic field 301 may shift in a predictable manner to point within region 302c, and its strength may increase after shifting the direction to region 302c in the second magnetic window. The change from region 302a to 302c while in the third magnetic window may indicate a rotation of the magnetic target in at least some implementations.

[0049] Fig. 4 shows an example of a multi-turn magnetic sensing system that includes a multi-turn magnetic sensor 400 and a magnetic target 402 formed from a magnetic ring 404 with a reversed pole pair 406. The magnetic ring 404, along with the reversed pole pair 406, can rotate relative to the sensor 400 along with a target (e.g., a shaft or other object whose rotation is tracked by the sensor 402). The magnetic ring 404 can be formed from concentric rings, with the outer ring forming a first magnetic pole and the inner ring forming a second magnetic pole. The concentric rings can form a magnetic dipole, and the reversed pole pair 406 can form an additional magnetic dipole that is reversed relative to the concentric rings. In at least some embodiments, the magnetic target 402 can be formed from a ring that is differently magnetized in different regions.Thus, the magnetic target 402 may be a single ring that is magnetic away from the reversed pole pair 406 in a first direction and magnetized to the reversed pole pair 406 in a second direction.

[0050] The multi-turn magnetic detection system may include readout circuitry, such as readout circuitry 430 as shown in Fig. 4, for reading data from the multiturn magnetic sensors disclosed herein. The readout circuitry 430 may be provided separately from the multiturn magnetic sensor 400 or integrated therein. The readout circuitry, such as the readout circuitry 430 of Fig. 4, can detect the position(s) and number of domain walls within the magnetic sensor (e.g., by detecting the resistance of one or more of the tracks forming the magnetic sensor, whose resistance may vary due to magnetoresistive effects, such as the GMR (Giant Magnetoresistive), AMR (Anisotropic Magnetoresistive), TMR (Tunnel Magnetoresistive), CMR (Colossal Magnetoresistive), and EMR (Extraordinary Magnetoresistive) effects). The readout circuitry can analyze the detected position(s) and number of domain walls and provide an output to external circuitry indicating the rotation count (or linear position in embodiments using linearly translated targets) of the magnetic target.

[0051] The magnetic target 402 may induce a magnetic field at the sensor 400 that varies with the rotation of the magnetic target 402 relative to the magnetic sensor 400, allowing the sensor 400 to track a rotation or a rotation number of the magnetic target 402. As an example, a reversed pole pair, such as pole pair 406, may be present at one or more locations along the magnetic ring 404, wherein the positions of the magnetic poles are reversed relative to the magnetic ring 404. As an example, the shaded areas of Fig. 4 may represent magnetic north poles, while the unshaded areas may represent magnetic south poles, or vice versa. Because of the reversed pole pair 406, the magnetic ring 404 may generate a non-uniform magnetic field that can be used to track the rotations of the magnetic ring 404. If desired, structures other than the reversed pole pair 406 may be included as part of the magnetic ring 404 to induce a non-uniform magnetic field and enable tracking of the rotation and / or number of rotations of the magnetic ring 404.

[0052] In the multi-turn magnetic detection system from Fig. 4, the sensor 400 can count a number of rotations with a full-turn resolution. The sensor 400 can store a state corresponding to an accumulated number of rotations, in which the accumulated number of rotations can be greater than 1.

[0053] In at least some embodiments, the field strength of the magnetic target 402 is high near the reversed pole pair 406, but weak along other portions of the magnetic ring 404. In other words, whenever rotation of the magnetic ring 404 moves the reversed pole pair 406 away from the sensor 400, the field strength received by the sensor 400 may be low. In contrast, whenever rotation of the ring 404 moves the reversed pole pair 406 close to the sensor 400, the field strength received by the sensor 400 may be high.

[0054] In the example of Fig. 4, the magnetic south pole of the magnetic rings 404 may be radial to the plane of the magnetic target 402 (e.g., pointing inward toward the center of the ring), while the magnetic north pole of the magnetic rings 404 may be antiradial to the plane of the magnetic target 402 (e.g., pointing inward toward the center of the ring) or vice versa (e.g., the north and south poles may be reversed). Analogously, it can be said that the magnetic north and south poles of the reversed pole pair 406 may be radial and antiradial to the plane of the magnetic target 402 (or vice versa).

[0055] Graphical representations showing a magnetic field strength curve 502 and a magnetic field angle curve 510 (e.g., magnetic angle) through the magnetic target 402 of Fig. 4 induced in the magnetic sensor 400, are in Fig. 5A and 5B respectively. The Fig. 5A and Fig. 5B show the field strength and angle as a function of the rotation angle of the magnetic target 402 relative to the magnetic sensor 400, respectively.

[0056] As in Fig. 5A, the magnetic field strength Hmin may be above a minimum magnetic field strength for reliable domain wall propagation and in the magnetic window of the magnetic sensor 400 between angles 504 and 506. The peak of the magnetic field strength curve 502, which occurs approximately midway between angles 504 and 506, may generally correspond to the position of the reversed pole pair 406 of the magnetic target 402 in proximity to the magnetic sensor 400. In particular, the magnetic field strength curve 502 may generally be at its maximum when the magnetic target 402 is rotated such that the reversed pole pair 406 is located near the magnetic sensor 400, which Fig. 4. As the magnetic target 402 is rotated such that the reversed pole pair 406 moves away from the magnetic sensor 400, the magnetic field strength curve 502 may decrease and fall below the minimum magnetic field strength Hmin for reliable domain wall propagation into the second magnetic window, in which domain wall propagation with changing magnetic field direction is expected to occur but is less than a 100% probability.

[0057] As in Fig. 5B and in at least some embodiments, the magnetic field direction may be within a range of angles 512 whenever the target 402 is rotated below angle 504 or above angle 506. The range of angles 512 may correspond to one of the four ranges 302a, 302b, 302c, and 302d shown in Fig. 3. In particular, the magnetic field generated by the magnetic target 402 may be within one of the four regions 302a, 302b, 302c, or 302d when the magnetic target 402 is rotated to an angle below angle 504 or above angle 506. As described in connection with Fig. As discussed in Figure 3, no domain wall propagation is expected while the magnetic angle remains within any of the four ranges 302a, 302b, 302c, and 302d. Thus, while the magnetic target is at an angle below 504 or above angle 506, the magnetic field strength can drop below the minimum magnetic field strength Hmin for reliable domain wall propagation into the second magnetic window and can even drop below the minimum magnetic field strength Hmin2 for domain wall propagation into the third magnetic window without data loss.

[0058] As the magnetic target 402 rotates and the reversed pole pair 406 passes the sensor 400, the magnetic field strength is within the magnetic window and completes a full 360-degree rotation, as shown in Fig. 5B. The rotation in the magnetic field direction can be recorded by the sensor 400 and used to track a rotation count of the magnetic target 402.

[0059] As in Fig. 5A and Fig. As shown in Figure 5B, the magnetic field strength may be above the minimum magnetic field strength Hmin for reliable domain wall propagation and within the magnetic window of the magnetic sensor 400 at all times when the magnetic field angle curve 510 is outside the range of angles 512. Thus, the magnetic target 402 may provide a magnetic field strength sufficient to cause reliable domain wall propagation within the magnetic sensor 400 whenever the direction of the magnetic field changes significantly due to rotation of the magnetic target 402.

[0060] In at least some embodiments, the magnetic sensors disclosed herein, such as magnetic sensors 400, 600, 800, and 900, may be precharged and / or initialized prior to active operations in tracking the rotations of a magnetic target having one or more domain walls. As an example, magnetic fields from a source other than the magnetic target (e.g., a magnetic initialization source) may be applied to a magnetic sensor to generate one or more domain walls, such as domain wall 213 of Fig. 2, and to position those domain walls at appropriate locations along the track. This initialization process can be advantageous in arrangements where rotation of a magnetic target can move a domain wall within a magnetic sensor but is unable to generate new domain walls.

[0061] Fig. 6 shows an alternative magnetic target 602 that can be tracked by a magnetic sensor such as sensor 600. Magnetic target 602 can include three magnetic pole pairs 604, 606, and 608, which can have alternating poles. In particular, magnetic pole pair 606 can be rotated relative to pole pairs 604 and 608. Furthermore, magnetic pole pairs 604 and 608 can be configured such that the magnetic field strength decreases with increasing distance from the center pole pair 606, potentially to zero. Magnetic pole pairs 604 and 608 can be formed from magnetic materials that decrease in thickness, with the thickest regions located at the reversed pole pair 606, and have a tapered thickness with increasing distance from the reversed pole pair 606.In at least some embodiments, magnetic targets such as target 602 and the other targets disclosed herein may be formed from a single piece of magnetic material, with different regions having different magnetizations. As one example, regions of the single piece of magnetic material corresponding to the center pole pair 606 may be magnetized in a first direction, while regions of the single piece of magnetic material corresponding to pole pairs 604 and 608 may be magnetized in a second direction. In still other embodiments, magnetic targets such as target 602 and the other targets disclosed herein may be formed from multiple pieces of magnetic material joined together.

[0062] In contrast to the magnetic target 402 of Fig. 4, the magnetic target 602 may include substantially less magnetic material. In particular, the magnetic target 602 may be formed substantially from magnetic material forming the magnetic pole pairs 604, 606, and 608 integrated therewith, attached thereto, or otherwise disposed thereon at one or more locations along the target 650. In at least some embodiments, the magnetic target 602 may be formed by attaching the magnetic material forming the magnetic pole pairs 604, 606, and 608 to a target 650 to count rotations of the target 650. The target 650 may be non-magnetic, if desired. A magnetic target 602 may also be provided in a straight shape, with one or more groupings of two or three magnetic pole pairs spaced along the elongated direction of the straight target.

[0063] In the example of Fig. 6, the magnetic north pole of the magnetic pole pairs 604 and 608 can be said to be radial to the plane of the magnetic target 602 (e.g., pointing inward toward the center of the ring), while the magnetic south pole of the magnetic pole pairs 604 and 608 can be said to be antiradial to the plane of the magnetic target 602 (e.g., pointing outward from the ring), or vice versa (e.g., the north and south poles can be reversed). Analogously, the magnetic north and south poles of the reversed pole pair 606 can be said to be antiradial and radial (or vice versa) to the plane of the magnetic target 602, respectively.

[0064] Graphical representations of the magnetic field strength curve 702 and the magnetic field angle curve 710 (e.g. magnetic angle) generated by the magnetic target 602 of Fig. 6 induced at the magnetic sensor 600 are in Fig. 7A and 7B respectively. The Fig. 7A and Fig. 7B show the field strength and angle as a function of the rotation angle of the magnetic target 602 relative to the magnetic sensor 600, respectively.

[0065] As in Fig. 7A, the magnetic field strength Hmin may be above the minimum magnetic field strength for reliable domain wall propagation and in the magnetic window of the magnetic sensor 600 between angles 704 and 706. The peak of the magnetic field strength curve 502, which occurs approximately midway between angles 704 and 706, may generally correspond to the position of the reversed pole pair 606 of the magnetic target 602. In particular, the magnetic field strength curve 702 may generally be at its maximum when the magnetic target 602 is rotated such that the reversed pole pair 606 is located near the magnetic sensor 600, which Fig. 6. As the magnetic target 602 is rotated so that the flipped pole pair 606 moves away from the magnetic sensor 600, the magnetic field strength curve 702 may decrease and fall below the minimum magnetic field strength Hmin for reliable domain wall propagation into the second magnetic window, in which domain wall propagation is expected to occur with changing magnetic field direction, but is less than a 100% probability. As the magnetic target 602 is further rotated so that the pole pairs 604 and 608 move away from the magnetic sensor 600, the magnetic field strength curve 702 may decrease further and fall below the minimum magnetic field strength Hmin2 for domain wall propagation into the third magnetic window, in which domain wall propagation is not expected to occur.

[0066] As in Fig. 7B and in at least some embodiments, the magnetic field direction may be within a range of angles 712 whenever the target 602 is rotated below angle 704 or above angle 706. The range of angles 712 may correspond to one of the four ranges 302a, 302b, 302c, and 302d shown in Fig. 3. In particular, the magnetic field generated by the magnetic target 602 may be within one of the four regions 302a, 302b, 302c, or 302d when the magnetic target is rotated to an angle below angle 704 or above angle 706 relative to the magnetic sensor 600. As described in connection with Fig. 3, no domain wall spreading is expected while the magnetic angle remains within any of the four ranges 302a, 302b, 302c, and 302d. Thus, while the magnetic target 602 is at an angle below 704 or above angle 706, the magnetic field strength curve 702 can fall below the minimum magnetic field strength Hmin for reliable domain wall spreading into the second magnetic window and can fall below the minimum magnetic field strength Hmin2 for domain wall spreading into the third magnetic window without loss of data. It should be noted that the direction of the magnetic field is irrelevant while the magnetic field strength is in the third magnetic window. Thus, stray magnetic fields or other changes in the magnetic field direction do not affect the operation of the magnetic sensor 600 as long as the strength remains within the third magnetic window.

[0067] As the magnetic target 602 rotates and the reversed pole pair 606 passes the sensor 600, the magnetic field strength is within the magnetic window and completes a full 360-degree rotation, as shown in Fig. 7B. The rotation in the magnetic field direction can be recorded by the sensor 600 and used to track a rotation count of the magnetic target 602.

[0068] As in Fig. 7A and Fig. As shown in Figure 7B, the magnetic field strength may be above the minimum magnetic field strength Hmin for reliable domain wall propagation and within the magnetic window of the magnetic sensor 600 at all times when the magnetic field direction is outside the range of angles 712. Thus, the magnetic target 602 may provide a magnetic field strength sufficient to cause reliable domain wall propagation within the magnetic sensor 600 whenever the direction of the magnetic field changes significantly due to rotation of the magnetic target 602 relative to the sensor 600.

[0069] If desired, the principles and advantages discussed herein can be applied to targets of different shapes. As an example, straight magnetic targets, such as those in the examples of Fig. 12 and Fig. 13, instead of circular magnetic targets. In a straight application, a magnetic bar may be magnetized perpendicular to its elongated direction and may have one or more reversed poles arranged along its elongated direction. A multi-turn magnetic sensor may count the reversed poles (in a manner similar to that described herein in connection with circular targets) and thereby track straight motion of the magnetic target relative to the magnetic sensor. Alternatively, or additionally, a multi-turn magnetic sensor may be arranged to rotate relative to a straight magnetic target and count rotations of the multi-turn magnetic sensor.

[0070] As a further example, the principles and advantages discussed herein can be applied to magnetic rings configured for axial sensing, as in the examples of Fig. 8 and Fig. 9 shown.

[0071] As in the example of Fig. 8, a magnetic target 802 may be configured for detection by a magnetic sensor, such as sensor 800, disposed above the plane of the magnetic target 802. The magnetic target 802 may include magnetic rings 804 and a reversed pole pair 804 integrated into, attached to, or otherwise disposed on the target 850. The magnetic rings 804 may be configured as shown in Fig. 8, with the magnetic poles arranged on opposite surfaces of the ring, in contrast to the concentric arrangement of Fig. 4. The magnetic target 802 may rotate about a rotation axis 810 together with the target 850, and the number of rotations of the magnetic target 802 and thus the target 850 may be recorded by the magnetic sensor 800 using the techniques discussed herein.

[0072] In the example of Fig. 8, the magnetic north pole of the magnetic rings 804 can be normal to the plane of the magnetic target 802 (e.g., pointing above the plane of the ring), while the magnetic south pole of the magnetic rings 804 can be antinormal to the plane of the magnetic target 802 (e.g., pointing below the plane of the ring), or vice versa (e.g., the north and south poles can be swapped). Analogously, it can be said that the magnetic north and south poles of the reversed pole pair 806 can be antinormal or normal (or vice versa) to the plane of the magnetic target 802.

[0073] The magnetic target 802 of Fig. 8 can generate magnetic fields for the magnetic sensor 800, which can be any of the multi-turn magnetic sensors discussed above, similar to the magnetic fields of the magnetic target 402 of Fig. 4. In particular, the strength of the magnetic field generated by the magnetic target 802 may be within the second or third magnetic window when the magnetic target 802 is rotated such that the reversed pole pair 806 is positioned away from the magnetic sensor 800. Furthermore, when the magnetic target 802 is rotated such that the reversed pole pair 806 passes the magnetic sensor 800, the magnetic field generated by the magnetic target 802 may have a strength within the magnetic window of the sensor 800 and may change direction in a manner that can be recorded by the sensor 800, allowing the sensor 800 to track the number of rotations of the magnetic target 802.

[0074] As in the example of Fig. 9, a magnetic target 902 configured for axial sensing by the magnetic sensor 900 may be formed from pole pairs 904 and 908 disposed on either side of the inverted pole pair 906. The pole pairs 904, 906, and 908 may be integrated into the target 950, attached thereto, or otherwise disposed at one or more locations along the target 950. The magnetic target 902 may rotate together with the target 950 about the rotation axis 910, and the number of rotations of the magnetic target 902, and thus of the target 950, may be recorded by the magnetic sensor 900 using the techniques described herein. The magnetic target 902 may provide benefits similar to those described herein in connection with Fig. 6 discussed.

[0075] The magnetic target 102 of Fig. 9 can generate magnetic fields for the magnetic sensor 900 that are similar to the magnetic fields of the magnetic target 602 of Fig. 6. In particular, the strength of the magnetic field generated by the magnetic target 902 may be within the third magnetic window when the magnetic target 902 is rotated such that the reversed pole pair 906 is positioned away from the magnetic sensor 900. Furthermore, when the magnetic target 902 is rotated such that the reversed pole pair 906 passes the magnetic sensor 900, the magnetic field generated by the magnetic target 902 may have a strength within the magnetic window of the sensor 900 and may change direction in a manner that can be recorded by the sensor 900, allowing the sensor 900 to track the number of rotations of the magnetic target 902.

[0076] In the example of Fig. 9, the magnetic north poles of the magnetic pole pairs 904 and 908 can be normal to the plane of the magnetic target 902 (e.g., pointing above the plane of the ring), while the magnetic south poles of the pairs 904 and 908 can be antinormal to the plane of the magnetic target 902 (e.g., pointing below the plane of the ring), or vice versa (e.g., the north and south poles can be swapped). Analogously, it can be said that the magnetic north and south poles of the inverted pole pair 906 can be antinormal and normal (or vice versa) to the plane of the magnetic target 902.

[0077] Fig. 10 shows an exemplary method 1000 for counting rotations of a magnetic target using a magnetic sensor. The magnetic target and the magnetic sensor may be any of the magnetic targets and sensors disclosed herein.

[0078] At block 1002, a magnetic sensor may receive a magnetic field with a strength that is within a first magnetic window of the sensor. As one example, the magnetic field may be generated by a magnetic target that rotates (or otherwise moves) relative to the magnetic sensor. The magnetic field may have a strength sufficient to cause reliable propagation of domain walls within the magnetic sensor (e.g., not less than the smallest magnetic field strength Hmin for reliable domain wall propagation), but not so strong that it creates or nucleates new domain walls within the magnetic sensor without corresponding rotation of the magnetic field (e.g., not greater than the largest magnetic field strength Hmax).

[0079] At block 1004, the magnetic sensor may receive a magnetic field with a strength below the sensor's magnetic window (e.g., a field less than the smallest magnetic field strength Hmin for reliable domain wall propagation). Furthermore, at block 1004, the magnetic field may have a direction that is not associated with domain wall propagation. As an example, the direction of the magnetic field may be within one of the regions 302a, 302b, 302c, or 302d of Fig. 3. In at least some embodiments, block 1004 may include the magnetic field strength falling below the second magnetic window such that no domain wall propagation is expected (e.g., a field less than the minimum magnetic field strength Hmin2 for domain wall propagation). In such embodiments, the direction of the magnetic field may be irrelevant and unconstrained, while the field strength is below the minimum magnetic field strength for domain wall propagation Hmin2.

[0080] At block 1006, the magnetic sensor may receive a magnetic field having a strength within the magnetic window of the sensor. Furthermore, at block 1006, the magnetic field may have a direction that is not associated with the propagation of domain walls, such as one of the regions 302a, 302b, 302c, or 302d of Fig. 3.

[0081] At block 1008, while the magnetic field is within the magnetic window, the magnetic sensor may track or record changes in the direction of the magnetic field generated by a magnetic target. Specifically, the magnetic sensor may create, delete, or move domain walls within a spiral path. The position(s) and number of domain walls may be used to track changes in the direction of the magnetic field generated by the magnetic target.

[0082] At block 1010, the magnetic sensor may be read to obtain a rotation count of the magnetic target. In particular, readout circuitry coupled to the magnetic sensor may detect the position(s) and number of domain walls within the magnetic sensor (e.g., by detecting the resistance of one or more of the tracks forming the magnetic sensor, whose resistance may vary due to the GMR effect). The magnetic sensor may track how many times the magnetic target has been rotated relative to the sensor. The magnetic sensor may add counts when the magnetic target rotates in a first direction and subtract counts when the magnetic target rotates in a second direction opposite the first direction. Thus, the readout circuitry at block 1010 may determine how many times and in which direction the magnetic target has been rotated relative to some baseline state.Such information can be used, for example, to determine whether a car's steering wheel is straight, rotated 360 degrees clockwise, or rotated 360 degrees counterclockwise.

[0083] In at least some embodiments, the magnetic sensors disclosed herein, such as magnetic sensors 400, 600, 800, and 900, may be precharged or initialized with one or more domain walls prior to use in tracking the rotations of a magnetic target. As an example, magnetic fields from a source other than the magnetic target (e.g., an initialization magnet) may be applied to a magnetic sensor to generate one or more domain walls, such as domain wall 213 of Fig. 2, and to position those domain walls at appropriate locations along the track. This initialization process can be advantageous in arrangements where rotation of a magnetic target can move a domain wall within a magnetic sensor, but where it is difficult for the magnetic target to generate new domain walls.

[0084] Fig. 11 shows an exemplary method 1100 for initializing a magnetic sensor with one or more domain walls. The magnetic target and the magnetic sensor referenced in Fig. 11 may be any of the magnetic targets and magnetic sensors disclosed herein.

[0085] At block 1102, one or more magnetic sensors may be initialized to have at least one domain wall. As one example, a magnetic field from an initialization source (e.g., from a source other than the magnetic target the sensor will ultimately track) may be applied to the magnetic sensor in a manner that generates one or more domain walls within the sensor's magnetic spiral. The initialization process of block 1102 may include applying an initializing magnetic field with a strength within the sensor's magnetic window, then rotating the magnetic field through a partial revolution, a full revolution, or more than a full revolution.

[0086] At block 1104, the magnetic sensor may be configured to detect a magnetic target. As an example, the magnetic sensor may be installed in a device near a magnetic target so that rotation (or straight movement) of the magnetic target can be tracked by the magnetic sensor.

[0087] At block 1106, movement of one or more domain walls, which may include the domain wall or domain walls generated in block 1102, may be recorded by the magnetic sensor in response to rotation of the magnetic target and corresponding changes in the magnetic field generated by the magnetic target and received by the magnetic sensor.

[0088] At block 1108, the magnetic sensor may be read to obtain a rotation count of the magnetic target. In particular, readout circuitry coupled to the magnetic sensor may detect the position(s) and number of domain walls within the magnetic sensor (e.g., by detecting the resistance of one or more of the tracks forming the magnetic sensor, whose resistance may vary due to the GMR effect). The magnetic sensor may track how many times the magnetic target has been rotated relative to the sensor. The magnetic sensor may add counts when the magnetic target rotates in a first direction and subtract counts when the magnetic target rotates in a second direction opposite the first direction. Thus, the readout circuitry at block 1108 may determine how many times and in which direction the magnetic target has been rotated relative to some baseline state.Such information can be used, for example, to determine whether a car's steering wheel is straight, rotated 360 degrees clockwise, or rotated 360 degrees counterclockwise.

[0089] As discussed herein, the principles and advantages discussed herein can be applied to targets of different shapes, including straight targets such as those in the examples of Fig. 12 and Fig. 13 straight targets shown.

[0090] Fig. 12 shows an alternative magnetic target 1202 that can be tracked by the magnetic sensor 1200. As in Fig. 12, the magnetic target 1202 may be formed from a straight magnetic member 1204 with at least one reversed pole pair. The example of Fig. Figure 12 illustrates the magnetic target 1202 with two reversed pole pairs 1206a and 1206b, which can be located at any desired locations along the length of the straight magnetic member 1204. The straight magnetic member 1204 can be magnetized perpendicular to its elongated direction. As an example, the shaded areas of Fig. 12 may represent magnetic north poles, while the unshaded areas may represent magnetic south poles, or vice versa. Because of the reversed pole pairs such as 1206a and 1206b, the magnetic target 1202 may generate a non-uniform magnetic field that can be used to track the straight movement of the magnetic target 1202 along an axis 1210 relative to the sensor 1200 (or vice versa). The magnetic target 1202 may move straight with respect to the sensors 1200, e.g., along the axis 1210. The magnetic sensor 1200 may track the straight position of the magnetic target 1202 by recording the passages in each direction of the reversed pole pairs.

[0091] Fig. 13 shows an alternative magnetic target 1302 that can be tracked by a magnetic sensor such as sensor 1300. As in Fig. 13, a magnetic target 1302 configured for straight detection by the magnetic sensor 1300 may be formed from at least one grouping of pole pairs arranged on either side of an inverted pole pair. Fig. Figure 13 illustrates two such groupings; comprising a reversed pole pair 1306a disposed between pole pairs 1304 and 1308, and a reversed pole pair 1306b disposed between pole pairs 1304b and 1308b. The pole pairs and the reversed pole pairs of Fig. 13 may be integrated into, attached to, or otherwise arranged at one or more locations along the target 1350. As an example, the shaded areas of Fig. 13 represent magnetic north poles, while the unshaded areas may represent magnetic south poles, or vice versa.

[0092] The target 1350 can be translated parallel with respect to the sensor 1300 along the axis 1310. The straight position of the target 1350 along the axis 1310 can be recorded by the magnetic sensor 1300 using the techniques discussed herein. The magnetic target 1302 can provide benefits similar to those described herein in connection with Fig. 6 discussed.

[0093] A system is presented that includes a magnetic sensor that can store a magnetic state associated with a number of accumulated rotations of a magnetic target. The magnetic sensor can operate in conjunction with a magnetic target. The magnetic target can generate a magnetic field that, at some positions, falls below a magnetic window of the magnetic sensor. The magnetic target can generate a magnetic field that lies within the magnetic window when needed to update the magnetic state of the sensor to track the accumulated rotations of the magnetic target. The magnetic sensor can be initialized with one or more domain walls.

[0094] The technology disclosed herein may be implemented in a variety of electronic systems. Aspects of the disclosure may be applied to any systems and / or devices that could benefit from the magnetic sensing technology disclosed herein.

[0095] Aspects of the present disclosure may be implemented in various electronic devices. For example, aspects of the present disclosure may be implemented in any electronic device or electronic component that could benefit from the technology discussed herein. Examples of the electronic devices may include, but are not limited to, consumer electronic products, parts of consumer electronic products, electronic test equipment, vehicle electronic systems, and so on. Examples of the electronic devices may include, but are not limited to, computing devices, communications devices, home electronic appliances, automotive electronic systems, other vehicle electronic systems, industrial control electronic systems, and so on. Furthermore, the electronic devices may comprise unfinished products.

[0096] Throughout the specification and claims, the words "comprise," "having," and the like are generally construed in an inclusive sense, as opposed to an exclusive or exhaustive sense; that is, in the sense of "including, but not limited to." The word "coupled," as generally used herein, refers to two or more elements that may be either directly coupled to one another or coupled through one or more intervening elements. Likewise, the word "connected," as generally used herein, refers to two or more elements that may be either directly connected or connected through one or more intervening elements. Furthermore, the words "here," "above," "below," and words of similar import, when used in this application, are intended to refer to this application as a whole and not to any particular portions of this application.Where the context permits, words used in the above Detailed Description using the singular or plural form may also include the plural or singular, respectively. The word "or" in a reference to a list of two or more items is generally intended to include all of the following interpretations of the word: any of the items in the list, all of the items in the list, and any combination of the items in the list.

[0097] In addition, conditional language as used herein, such as, but not limited to, "may," "could," "might," "e.g.," "for example," "such as," and the like, unless specifically stated otherwise or understood within the context as used, is generally intended to convey that certain embodiments include certain features, elements, and / or conditions while other embodiments do not. Thus, such conditional language is generally not intended to imply that features, elements, and / or conditions are required in any way for one or more embodiments, or that one or more embodiments necessarily include logic for deciding whether these features, elements, and / or conditions are to be included or performed in a particular embodiment.

[0098] Although certain embodiments of the inventions have been described herein, these embodiments have been presented merely by way of example and are not intended to limit the scope of the disclosure. Indeed, the novel methods, apparatus, and systems described herein may be embodied in a variety of other forms; further, various omissions, substitutions, and changes in the form of the methods, apparatus, and systems described herein may be made without departing from the spirit of the disclosure. For example, circuit blocks and / or circuit elements described herein may be deleted, moved, added, subdivided, combined, and / or modified. Each of these circuit blocks and / or circuit elements may be implemented in a variety of different ways.The appended claims and their equivalents are intended to cover all such forms or modifications as would fall within the scope and spirit of the disclosure.

Claims

[1] A method for recording a number of rotations with a multi-turn magnetic sensor using an extended magnetic window, the method comprising: Applying a magnetic field to the multi-turn magnetic sensor having a magnetic target, the magnetic field defining a magnetic field vector at the multi-turn magnetic sensor, the magnetic field vector pointing out of a region for which domain wall propagation is expected in the multi-turn magnetic sensor, and the magnetic field having a first strength at the multi-turn magnetic sensor below a range for which domain walls predictably propagate through the multi-turn magnetic sensor; while the magnetic field vector points out of the area, increasing the strength of the magnetic field with the magnetic target to a second strength at the multiturn magnetic sensor within the range for which domain walls predictably propagate through the multiturn magnetic sensor; and while the magnetic field has the second strength at the multi-turn magnetic sensor, adjusting the magnetic field with the magnetic target object such that the magnetic field vector points into the area to adjust a state of the multi-turn magnetic sensor. [2] The method of claim 1, wherein adjusting the magnetic field comprises rotating the magnetic target relative to the multi-turn magnetic sensor. [3] A method according to any preceding claim, wherein adjusting the magnetic field comprises linearly translating the magnetic target relative to the multi-turn magnetic sensor. [4] A method according to any preceding claim, further comprising: Applying, with an initialization magnet separate from the magnetic target and to the multiturn magnetic sensor, an initialization magnetic field having a third strength that is within the range for which domain walls predictably propagate through the multiturn magnetic sensor; and Rotating the initialization magnetic field relative to the multiturn magnetic sensor to create at least one domain wall in the multiturn magnetic sensor. [5] A method according to any preceding claim, further comprising, while the magnetic field points out of the region, reducing the magnetic field to a third strength below a region for which any propagation of domain walls is expected by the multi-turn magnetic sensor. [6] Multi-turn magnetic detection system with an extended magnetic window, the multi-turn magnetic detection system comprising: a multi-turn magnetic sensor comprising magnetoresistive elements and configured to record a number of rotations of a magnetic field based on domain wall propagation by the multi-turn magnetic sensor; and a magnetic target configured to move between a first position relative to the multi-turn magnetic sensor and a second position relative to the multi-turn magnetic sensor, the magnetic target configured such that: in the first position, the magnetic target object is configured to apply the magnetic field with a first strength to the multi-turn magnetic sensor, wherein the first strength is below a range for which domain walls predictably propagate through the multi-turn magnetic sensor; and in the second position, the magnetic target object is configured to apply the magnetic field with a second strength to the multi-turn magnetic sensor, wherein the second strength is in the range for which domain walls predictably propagate through the multi-turn magnetic sensor. [7] The system of claim 6, wherein the magnetic target object comprises: a first section of magnetic material forming a first magnetic dipole; and a second portion of the magnetic material forming a second magnetic dipole, the first magnetic dipole being inverted relative to the second magnetic dipole, the first and second portions of the magnetic material being disposed along a substantially circular circumference, and at least a portion of the first portion of the magnetic material being disposed adjacent the second portion of the magnetic material. [8] The system of claim 7, wherein when the magnetic target is in the first position, the second portion of the magnetic material is disposed away from the multi-turn magnetic sensor. [9] The system of claim 7, wherein when the magnetic target is in the second position, the second portion of the magnetic material is disposed adjacent the multi-turn magnetic sensor. [10] The system of any one of claims 7 to 9, wherein the substantially circular perimeter defines a circle having a center, the first magnetic dipole being oriented such that the first magnetic dipole has a north magnetic pole and a south magnetic pole, the north magnetic pole of the first magnetic dipole being closer to the center of the circle than the south magnetic pole of the first magnetic dipole, and the second magnetic dipole being oriented such that the second magnetic dipole has a south magnetic pole and a north magnetic pole, the south magnetic pole of the second magnetic dipole being closer to the center of the circle than the north magnetic pole of the second magnetic dipole. [11] The system of any one of claims 7 to 9, wherein the substantially circular perimeter defines a circle lying in a plane, the first magnetic dipole being oriented such that the first magnetic dipole has a magnetic north pole pointing normal to the plane and a magnetic south pole pointing antinormal to the plane, and the second magnetic dipole being oriented such that the second magnetic dipole has a magnetic south pole pointing normal to the plane and a magnetic north pole pointing antinormal to the plane. [12] A system according to any one of claims 7 to 11, wherein the magnetic target comprises a ring having the substantially circular circumference and the first and second portions of the magnetic material together span substantially the entire substantially circular circumference of the ring. [13] The system of any one of claims 7 to 12, wherein the magnetic target comprises a third portion of the magnetic material forming a third magnetic dipole, the third magnetic dipole being inverted relative to the second magnetic dipole, and the second portion of the magnetic material being disposed between the first and third portions of the magnetic material. [14] The system of claim 13, wherein when the magnetic target is in the first position, the second portion of the magnetic material is disposed away from the multi-turn magnetic sensor, and wherein when the magnetic target is in the second position, the second portion of the magnetic material is disposed at the multi-turn magnetic sensor. [15] The system of claim 6, wherein the magnetic target comprises a straight magnetic target having an elongated direction and at least one pole pair magnetized perpendicular to the elongated direction, the pole pair being closer to the multi-turn magnetic sensor when the magnetic target is in the first position than when the magnetic target is in the second position. [16] A magnetic detection system with an extended magnetic window, the magnetic detection system comprising: a magnetic sensor comprising magnetoresistive elements and configured to record position data based on domain wall propagation by the magnetic sensor; and a magnetic target object arranged relative to the magnetic sensor such that: in a first position relative to the magnetic sensor, the magnetic target object is configured to apply a magnetic field having a first strength to the magnetic sensor, wherein the first strength lies in a range for which domain walls propagate through the magnetic sensor with a non-zero probability of less than 95%; and in a second position relative to the magnetic sensor, the magnetic target object is configured to apply the magnetic field with a second strength to the magnetic sensor, the second strength being in a range for which domain walls predictably propagate through the magnetic sensor. [17] The magnetic sensing system of claim 16, wherein the magnetic target is arranged relative to the magnetic sensor such that in a third position relative to the magnetic sensor, the magnetic target is configured to apply the magnetic field to the magnetic sensor at a third strength, the third strength being in a range for which domain walls are not expected to propagate through the magnetic sensor. [18] A magnetic detection system according to claim 16 or 17, wherein the magnetic target object is shaped in a ring and has a plurality of magnetic poles. [19] A magnetic detection system according to claim 16 or 17, wherein the magnetic target is formed in a ring lying in a plane, and wherein the magnetic target has magnetic poles pointing normal to the plane of the ring and antinormal to the plane of the ring. [20] The magnetic detection system according to claim 16, wherein the magnetic target comprises a straight magnetic target having an elongated direction, and wherein the straight magnetic target has magnetic poles perpendicular to the elongated direction of the straight magnetic target.

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