Magnetic Field Differential Torque Sensor

Abstract

A system, method, and apparatus for a differential magnetic field torque sensor including first and second magnetic targets for coupling to one or more rotatable shafts. The magnetic targets may include multi-pole ring magnets having a plurality of alternating magnetic domains. First and second differential magnetic field angular position sensors positioned proximate the magnetic targets generate an angular position of the targets, and a processing device is operable to receive an angular position from each of the first and second differential magnetic field angular position sensors and determine a difference between the angular positions. The difference corresponds to an angle between the targets, and the processing device is operable to calculate a torque applied to the one or more rotatable shafts based on the angle.

Description

[Background technology]

[0001]

[0001] Magnetic field sensors can be used in a variety of applications. In one application, magnetic field sensors can be used to detect the rotation angle of an object. In another related application, magnetic field sensors can be used to sense the rotation (e.g., continuous or non-continuous rotation) of an object.

[0002]

[0002] Various magnetic sensing elements may be used in magnetic field sensors. For example, planar Hall effect elements and vertical Hall effect elements are known types of magnetic field sensing elements. Planar Hall effect elements tend to be responsive to magnetic fields that are perpendicular to the surface of the substrate on which the planar Hall effect elements are formed. Vertical Hall effect elements tend to be responsive to magnetic fields that are parallel to the surface of the substrate on which the vertical Hall effect elements are formed. Magnetoresistive elements are also known types of magnetic field sensing elements used for magnetic field sensors. Some types of magnetoresistive elements tend to be responsive to magnetic fields that are parallel to the surface of the substrate on which the magnetoresistive elements are formed.

[0003]

[0003] Various parameters characterize the performance of magnetic field sensing elements and magnetic field sensors that use magnetic field sensing elements. These parameters include sensitivity, which is the change in the output signal of the magnetic field sensing element in response to a change in the magnetic field experienced by the magnetic field sensing element, and linearity, which is the degree to which the output signal of the magnetic field sensing element varies in direct proportion to the magnetic field. These parameters also include offset, which is characterized by an output signal from the magnetic field sensing element that is not representative of a zero magnetic field when the magnetic field sensing element is subjected to a zero magnetic field.

[0004]

[0004] Stray magnetic fields caused by magnetic components or other sources such as electric currents can interfere with the performance of magnetic field sensors and sensing elements. Such stray magnetic fields can pose serious problems in applications such as automobiles where electric motors, batteries, and other electromagnetic components are used. For example, electric motors that drive electric vehicles ("EVs") and hybrid electric vehicles ("HEVs") typically require significant amounts of current and therefore create strong magnetic fields around the cables that deliver current from the battery or alternator to the motor. Other common low current components can also generate significant stray magnetic fields in automotive applications such as electric power steering ("EPS") pumps, power windows or sunroofs, and any other electrically operated devices used in vehicles. Systems and signal processing that rely on such sensors can be adversely affected by stray magnetic fields as well, as stray magnetic fields can affect the accuracy of magnetic field sensors and cause significant output errors in such sensors. Summary of the Invention [Problem to be solved by the invention]

[0005]

[0005] Embodiments of the present disclosure provide systems, methods, and apparatus for differential angle and / or torque sensing with sensors that tend to eliminate and / or are resistant to stray magnetic fields. [Means for solving the problem]

[0006]

[0006] An example differential magnetic field torque sensor may include a first multi-pole magnet assembly having a plurality of magnetic pole pairs and configured for coupling to a first rotatable shaft (element), a second multi-pole magnet assembly having a plurality of magnetic pole pairs and configured for coupling to a second rotatable shaft, where the first rotatable shaft is coupled (e.g., mechanically coupled) to the second rotatable shaft by an elastic element (e.g., a metal cylinder, etc.), a first differential magnetic field angular position sensor positioned in proximity to the first multi-pole magnet assembly and configured to generate an angular position of the first multi-pole magnet assembly, a second differential magnetic field angular position sensor positioned in proximity to the second multi-pole magnet assembly and configured to generate an angular position of the second multi-pole magnet assembly, and a processing device operable to receive angular positions from each of the first and second differential magnetic field angular position sensors and determine a difference in angular positions, the difference corresponding to an angle, and the processing device operable to calculate a torque applied to the first or second rotatable shaft based on the angle. The first and / or second rotatable shaft (element) may be part of, constitute or comprise a steering column.

[0007]

[0007] With respect to the sensor, each of the first and second differential magnetic field angular position sensors may include (i) a first array of magnetic field sensing elements, (ii) a second array of magnetic field sensing elements, the first array of magnetic field sensing elements being spaced a distance from the second array of magnetic field sensing elements, the first and second arrays of magnetic field sensing elements each having at least first and second axes of maximum sensitivity, the first axis of maximum sensitivity being orthogonal to the second axis of maximum sensitivity, and (iii) an angular position module for determining an angular position of the multi-pole magnet assembly from a differential signal from the first and second arrays of magnetic field sensing elements. In some embodiments or examples, the first and / or second differential magnetic field angular position sensors may be considered or referred to (individually or collectively) as "means for detecting differential angular position."

[0008]

[0008] The first or second differential magnetic field angular position sensor may include a Hall effect element. The first or second differential magnetic field angular position sensor may include a magnetoresistive element. For the first differential magnetic field angular position sensor, a distance that the first array of magnetic field sensing elements is spaced from the second array of magnetic field sensing elements may be configured to match a pitch of adjacent pole pairs of the first multi-pole magnet assembly. For the second differential magnetic field angular position sensor, a distance that the first array of magnetic field sensing elements is spaced from the second array of magnetic field sensing elements may be configured to match a pitch of adjacent pole pairs of the second multi-pole magnet assembly.

[0009]

[0009] The angular position module may include an arctangent calculation module and / or may be configured to provide CORDIC (Coordinate-Rotation-Digital-Computer) processing. The first or second multi-pole magnet assembly may include a ring magnet. For the first differential magnetic field angular position sensor, the differential signals from the first and second arrays of magnetic field sensing elements may include sine and cosine signals. For the second differential magnetic field angular position sensor, the differential signals from the first and second arrays of magnetic field sensing elements may include sine and cosine signals.

[0010]

[0010] The resilient element may include a torsion bar. The first and second multi-pole magnet assemblies may be concentrically disposed in a common plane in an end-shaft configuration, the first multi-pole magnet assembly having a first radius and the second multi-pole magnet assembly having a second radius different from the first radius. The first and second differential magnetic field angular position sensors may be disposed on a common die. The common die may be disposed adjacent to the first and second multi-pole magnet assemblies and parallel to the common plane.

[0011] The first and second multi-pole magnet assemblies may be disposed in first and second parallel planes, respectively, in a side-shaft configuration. The first and second differential magnetic field angular position sensors may be disposed on a common die. The common die may be disposed adjacent to the first and second multi-pole magnet assemblies and perpendicular to the parallel planes.

[0012] The angular position module may be operable to calculate a coupling matrix for magnetic coupling between the first array of magnetic field sensing elements and the second array of magnetic field sensing elements. The angular position module may be further operable to calculate an inverse matrix based on the coupling matrix and to modify the differential signal from the first and second arrays of magnetic field sensing elements.

[0013] The processing unit may be operable to calculate a coupling matrix for magnetic coupling between the first differential magnetic field angular position sensor and the second differential magnetic field angular position sensor. The processing unit may be further operable to calculate an inverse matrix based on the coupling matrix and to correct the angular positions from the first and second differential magnetic field angular position sensors.

[0014]

[0014] The manner and process of making and using the disclosed embodiments may be understood by reference to the figures in the accompanying drawings. It should be understood that the components and structures illustrated in the figures are not necessarily to scale, emphasis instead being placed on illustrating the principles of the concepts described herein. Like reference numbers indicate corresponding parts throughout the different views. Moreover, the embodiments are illustrated in the figures by way of example and not by way of limitation. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 illustrates an example magnetic field differential torque sensor in a side shaft configuration according to the present disclosure. [Diagram 2]

[0016] 1 illustrates an exemplary magnetic field differential torque sensor in an end shaft configuration according to the present disclosure. [Diagram 3]

[0017] 1A-1C illustrate exemplary embodiments of a magnetic field differential torque sensor in a side shaft configuration utilizing a common die according to the present disclosure; [Figure 4]

[0018] 1A-1C illustrate exemplary embodiments of a magnetic field differential torque sensor in an end-shaft configuration utilizing a common die according to the present disclosure; [Diagram 5]

[0019] FIG. 2 is a circuit and signal flow diagram of an example magnetic field differential torque sensor according to the present disclosure. [Figure 6]

[0020] FIG. 2 is a side view of an exemplary magnetic field differential angle sensor according to the present disclosure. [Figure 7]

[0021] FIG. 1 is a block diagram of an example computer system operable to perform processing in accordance with the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016]

[0022] Before describing the exemplary embodiments of the present disclosure, some information is provided. As used herein, the term "magnetic field sensing element" refers to various electronic elements that can sense a magnetic field. The magnetic field sensing element may be, but is not limited to, a Hall effect element, a magnetoresistance element, or a magnetotransistor. As is known, there are different types of Hall effect elements, for example, planar Hall effect elements, and vertical Hall effect elements. As is further known, there are different types of magnetoresistance elements, for example, semiconductor magnetoresistance elements such as indium antimonide (InSb), giant magnetoresistance (GMR) elements, for example, spin valves, anisotropic magnetoresistance elements (AMR), tunnel magnetoresistance (TMR) elements, and magnetic tunnel junctions (MTJs). The magnetic field sensing element may be a single element, or alternatively, it may include two or more magnetic field sensing elements arranged in various configurations, for example, a half bridge or a full (Wheatstone) bridge. Depending on the type of device and other application requirements, the magnetic field sensing element may be a device made of Group IV semiconductor materials such as silicon (Si) or germanium (Ge), or Group III-V semiconductor materials such as gallium arsenide (GaAs) or indium compounds, e.g., indium antimonide (InSb).

[0017]

[0023] As is known, some of the above-mentioned magnetic field sensing elements tend to have a maximum sensitivity axis parallel to the substrate supporting the magnetic field sensing element, while other of the above-mentioned magnetic field sensing elements tend to have a maximum sensitivity axis perpendicular to the substrate supporting the magnetic field sensing element. In particular, planar Hall effect elements tend to have a sensitivity axis perpendicular to the substrate, while metal-based or metallic magnetoresistance elements (e.g., GMR, TMR, AMR) and vertical Hall effect elements tend to have a sensitivity axis parallel to the substrate.

[0018]

[0024] As used herein, the term "magnetic field sensor" refers to an assembly that uses one or more magnetic field sensing elements in combination with electronic circuitry, typically all disposed on a common substrate, e.g., a semiconductor substrate. Magnetic field sensors are used in a variety of applications, including, but not limited to, angle sensors that sense the angle of a magnetic field direction, angle sensors that sense the angle of rotation of a target object, and rotation sensors that sense the rotation (e.g., speed and direction of rotation) of a rotating target object.

[0019]

[0025] Described herein is a magnetic field sensor in the form of an angle and / or rotation sensor capable of sensing the angle of rotation of a ferromagnetic object. As used herein, the term "magnetic field signal" is used to describe any circuit signal resulting from a magnetic field experienced by or sensed by a magnetic field sensing element.

[0020]

[0026] The terms "parallel" and "perpendicular" are used in various contexts within this specification. It should be understood that the terms parallel and perpendicular do not require exact perpendicularity or exact parallelism, but rather, normal manufacturing tolerances are intended to apply, which tolerances will depend on the context in which the terms are used. In some cases, the term "substantially" is used to modify the terms "parallel" or "perpendicular." In general, use of the term "substantially" reflects angles that are beyond manufacturing tolerances, but are within, for example, + / - 10 degrees (plus or minus 10 degrees).

[0021]

[0027] As used herein, the term "processor" or "processing device" refers to an electronic circuit that performs a function, operation, or sequence of operations. The function, operation, or sequence of operations may be hard-coded into the electronic circuit or soft-coded with instructions held in a memory device. A "processor" or "processing device" may perform a function, operation, or sequence of operations using digital values ​​or using analog signals.

[0022]

[0028] In some embodiments, the "processor" or "processing unit" may be embodied in an application specific integrated circuit (ASIC), which may be an analog ASIC or a digital ASIC. In some embodiments, the "processor" or "processing unit" may be embodied in a microprocessor with associated program memory. In some embodiments, the "processor" or "processing unit" may be embodied in discrete electronic circuitry, which may be analog or digital.

[0023]

[0029] As used herein, the term "module" may describe a "processor." However, the term "module" may be used more generally to describe any circuit that can transform an input signal into an output signal that differs from the input signal.

[0024]

[0030] A processor may include an internal processor or internal module that performs a portion of a processor's function, operation, or sequence of operations. Similarly, a module may include an internal processor or internal module that performs a portion of a module's function, operation, or sequence of operations.

[0025]

[0031] Although the electronic circuits shown in the figures herein may be shown in the form of analog or digital blocks (e.g., processors or modules), it should be understood that the analog blocks may be replaced by digital blocks (e.g., processors or modules) performing the same or similar functions, and the digital blocks may be replaced by analog blocks performing the same or similar functions. Analog-to-digital or digital-to-analog conversion may not be explicitly shown in the figures, but should be understood to be present.

[0026]

[0032] In particular, it is to be understood that the so-called comparator may consist of an analog comparator having a two-state output signal indicating that an input signal is above or below a threshold level (or that one input signal is above or below another input signal). However, a comparator may also or alternatively consist of a digital circuit (e.g., a processor or module) having an output signal or value with at least two states indicating that an input signal or value is above or below a threshold level (or that one input signal or value is above or below another input signal or value), respectively, or that a digital signal or value is above or below a digital threshold signal or value (or another digital signal or value), respectively.

[0027]

[0033] As used herein, the term "predetermined" when referring to a value or signal refers to a value or signal that is set or fixed in the factory at the time of manufacture or thereafter by external means, e.g., programming. As used herein, the term "determined" when referring to a value or signal refers to a value or signal that is recognized by the circuit after manufacture and during operation.

[0028]

[0034] As used herein, the term "amplifier" refers to a circuit element that has a gain greater than, less than, or equal to unity.

[0029]

[0035] As used herein, the terms "line" and "linear" are used to describe either a straight line or a curved line. A line may be described by a function having any degree, but is never infinite.

[0030]

[0036] 1 is a diagram of an example differential magnetic field torque sensor 100 configured to reject stray magnetic fields, according to an embodiment of the present disclosure. The sensor 100 includes first and second differential magnetic field angular position sensors 102, 104 positioned adjacent first and second targets 106, 108, respectively. The first and second targets 106, 108 are coupled, e.g., mounted, to a rotatable member 110, shown as a representative shaft, under loading conditions of applied torques indicated by opposing torques M1 and M2. The magnetic field sensors 102, 104 are operable to detect the angular positions (angles) of the respective adjacent targets 106, 108, and to generate corresponding signals indicative of the angular positions α1 and α2. It should be understood that the rotatable member 110 is not necessarily a unitary body, it may have a different shape than that shown, and it may be made up of or include multiple components or parts, such as torsion bars, as described in more detail below. In an exemplary embodiment, the first and second targets 106, 108 are ring magnets, as shown. The configuration of the magnetic field sensors 102, 104 and targets 106, 108 in association with a rotatable member 110 (e.g., a shaft) as shown in FIG. 1 may be referred to in some applications as a "side shaft" configuration.

[0031]

[0037] The differential magnetic field angular position sensors 102, 104 may each include or consist of a set of magnetic field sensing elements positioned to detect magnetic field changes in a desired manner, as described more fully below. In an example embodiment, the differential magnetic field angular position sensors 102, 104 may each include two or more Hall effect elements configured such that the difference in the signals from the Hall effect elements may be used as a differential signal with stray magnetic field effects reduced and / or eliminated by differential processing. In some embodiments, the differential magnetic field angular position sensors 102 and / or 104 or the like may be considered or referred to (individually or collectively) as a "means for detecting differential angular position."

[0032]

[0038] During operation of the sensor 100, when torque is applied to the rotatable member 110 about the torsion axis, the torque is transferred and distributed along the rotatable member 110. Because the two targets 106, 108 (e.g., ring magnets) are positioned at different locations along the length of the rotatable member 110 (in the direction of the torsion axis), they rotate by different amounts and undergo angular displacement (angular misalignment) relative to one another. The distance between the targets 106, 108 is one factor that affects the amount of angular misalignment between the differential sensors 102, 104 that results from a given applied torque. As described in more detail below, a resilient element such as a torsion bar (e.g., a metal cylinder) may be used as part of the physical connection between the targets 106, 108, with an extension or section (e.g., a sheath or sleeve) used to move the targets 106, 108 closer to one another, for example, in a side-by-side arrangement for a side shaft sensor configuration, or concentric with one another for an end shaft sensor configuration.

[0033]

[0039] 1, a processor (not shown) can receive the differential magnetic angles α1 and α2 and calculate the difference between the angles, where such difference in angle corresponds to the relative difference in angular displacement between the targets 106, 108 - i.e., the angle between them - under a given applied torque. The applied torque can be obtained by multiplying the angle difference (the angle itself) by a system-defined coefficient k. The defined coefficient k can be related, for example, to the material's modulus of rigidity and / or the geometry (moment of inertia) of the rotatable member 110.

[0034]

[0040] 2 illustrates an example differential magnetic field torque sensor 200 in an end-shaft configuration, according to an exemplary embodiment of the present disclosure. The sensor 200 is generally similar to the sensor 100 of FIG. 1, except that the differential sensor is positioned in an end-shaft configuration, and instead of a single rotatable member, two rotatable shafts 212, 214 are connected by an intermediate resilient element 216 (e.g., a torsion bar). The use of the intermediate resilient element 216 may improve the signal strength (e.g., magnitude) and / or signal-to-noise ratio (S / N) of the sensed signal.

[0035]

[0041] As shown in FIG. 2, the sensor 200 includes first and second differential magnetic field sensors 204, 206 mounted on a suitable support or substrate 208, e.g., a printed circuit board (PCB), adjacent respective targets 208, 210. In an exemplary embodiment, the differential magnetic field angular position sensors 204, 206 may be integrated into a common integrated circuit (IC) package 202. In an exemplary embodiment, the targets 208 and 210 may be ring magnets, each having a plurality of alternating magnetic domains or poles formed, e.g., by separate joined magnets or by differently magnetized portions of a unitary ring structure. The targets 208, 210 are coupled to the first and second shafts 212 and 214 by sheaths (or sleeves) 222, 224, respectively. The targets 208, 210 may be mounted on respective supports 218, 220, which in turn are connected to the sheaths 222, 224. As noted above, the first and second shafts 212 and 214 are connected by a resilient member 216, for example a torsion bar.

[0036]

[0042] The torsion bar 216 may be used to increase the angular signal strength for angle measurements by creating a larger twist angle (easier to measure / detect) from a given applied torque on the first or second shafts 212, 214. The torsion bar 216 may be designed by appropriate geometry and / or material selection (e.g., use of a particular metal alloy) to twist by a particular angular range for a typical applied load. The sheaths 222, 224 allow the targets 208, 210 to be mounted close to each other, facilitating measurement of the relative angle between the shafts 212, 214, even though the actual portions of the first and second shafts 212, 214 to which they are respectively attached are separated by a greater distance. Although not shown, other associated circuitry and components may be included on the support 208, such as a processor as described below. It should be understood that the illustrated locations of the supports 218, 220 along the torsion bar 216 and the lengths of the sheaths 222, 224 are merely representative and provided for purposes of illustration, and that their locations and lengths may vary within the scope of this disclosure. Furthermore, in some embodiments, the supports 218, 220 may be mounted to or adjacent the shafts 212 or 214 such that only one sheath is used (instead of two), and that sheath spans substantially the entire length of the torsion bar 216, allowing the other sheath to be omitted.

[0037]

[0043] During operation of the sensor 200, when torque is applied to either shaft 212 or 214, the torque is transferred to the other shaft through the elastic element 216 (torsion bar). The torsion bar 216 undergoes an amount of twist (more extreme than would occur if it were not present), and the connected shafts (212, 214) are correspondingly rotated relative to one another by an angle (e.g., θ). The two targets 208, 210 are adjacent to one another for angular measurement, while connected to separate shafts 212, 214, resulting in the same angular offset (e.g., θ) relative to one another as the shafts 212, 214. In an exemplary embodiment, the system 200 may be utilized as a torque measurement sensor for a steering column 226 in an automotive application, with the shafts 212, 214 and the elastic element 216 being components of the steering column.

[0038]

[0044] 3 is a diagram of an exemplary embodiment of a magnetic field differential torque sensor 300 in a side shaft configuration utilizing a common die for magnetic sensing elements according to the present disclosure. The sensor 300 includes a die 302 on which two differential magnetic field sensors 304, 306 are disposed. Each sensor 304, 306 includes a pair of two-axis magnetic field sensing elements (shown as circles) for measuring the angular position of a respective adjacent target 310, 320 about an axis of rotation 308. As previously mentioned, the targets 310, 320 may be coupled to one or more rotatable members, e.g., rods, shafts, or other components, desired for torque measurement. In an exemplary embodiment, the magnetic field sensors 304, 306 include Hall effect elements.

[0039]

[0045] Continuing with the description of FIG. 3, the targets 310, 320, e.g., multi-pole ring magnets, used to measure angles are preferably manufactured and magnetized on the same machine to have the same error profile, thus improving accuracy. The number of pole pairs of each target (e.g., ring magnet) 310, 320 may also be optimized for twisting relative to the rotatable member due to applied torque. For example, if the applied torque results in a maximum relative rotation of 10 degrees, it may be desirable or preferable for each pole pair to span 20 degrees. This arrangement may provide optimal resolution and accuracy when the electrical angle is multiplied by the mechanical angle for angle measurement in the exemplary embodiment. In the configuration shown, the ring magnets 310, 320 are preferably magnetized radially orthogonal to the vertical axis 308 (Z-axis).

[0040]

[0046] 4 is a diagram of an exemplary embodiment of a magnetic field differential torque sensor 400 in an end-shaft configuration utilizing a common die for the magnetic sensing elements according to the present disclosure. The sensor 400 includes a die 402 on which two differential magnetic field sensors 404, 406 are disposed. Two ring magnets 410, 420 are present as magnetic targets for the sensors 404, 406, respectively. In the configuration shown, the ring magnets 410, 420 are preferably magnetized in the direction of a vertical axis 430 (Z-axis). A torsion bar (elastic member) may be utilized as previously discussed, but this is omitted from FIG. 4 for purposes of clarity.

[0041]

[0047] In an exemplary embodiment, each sensor 404, 406 includes a pair of dual-axis Hall effect elements, indicated by ellipses 404-1, 404-2 and 406-1, 406-2, and a die 402 is common to each of the sensors 404, 406. The die 402 may be encapsulated or contained in an IC package (not shown). In an exemplary embodiment, the pitch between the sensing elements of a sensor, e.g., 406, may be matched to the pitch of the magnetized area of ​​a corresponding target, e.g., an adjacent ring magnet 420. In an exemplary embodiment, the pitch of the inner sensing elements, e.g., of sensor 404, may be smaller than the pitch of the outer sensing elements, e.g., of sensor 406, as indicated by the dashed line passing through the sensing elements and intersecting the center of curvature / axis of rotation 430.

[0042]

[0048] 5 is a circuit and signal flow diagram of a magnetic field differential torque sensor 500 according to an exemplary embodiment of the present disclosure. The sensor 500 includes first and second differential magnetic field angle sensors 502, 504. The sensors 502, 504 may be the same as or similar to the sensors 304, 306 (FIG. 3) or the sensors 404, 406 (FIG. 4) and thus may be positioned adjacent to a respective target, e.g., a ring magnet, such that detection of the rotation angle of the target may be processed to detect torque. Each sensor 502, 504 includes a first sensing element or sensing element array 502-1, 504-1 and a second sensing element or sensing element array 502-2, 504-2. Each of the first sensing elements 502-1, 504-1 includes a pair of sensing elements configured to detect orthogonal magnetic field components (i.e., having orthogonal axes of maximum sensitivity), such that each pair generates sine and cosine signals. Similarly, each of the second sensing elements 502-2, 504-2 includes a pair of sensing elements configured to detect orthogonal magnetic field components (i.e., having orthogonal axes of maximum sensitivity), such that each pair generates sine and cosine wave signals. For example, each of the magnetic field sensing elements (502-1, 502-2, and 504-1, 504-2) may include a pair of sensing elements positioned orthogonal to one another to detect orthogonal magnetic field components, as illustrated by the X-axis and Z-axis components of the detected magnetic field (B). In an exemplary embodiment, the magnetic field sensors 502, 504 include Hall effect elements.

[0043]

[0049] Continuing to refer to FIG. 5, for each magnetic sensor 502, 504, the same component signals (e.g., X-axis and Z-axis components) from the magnetic sensing element are differentially processed as shown by subtractors 512, 514, 532, 534. Differential processing facilitates elimination of and / or immunity to the detrimental effects of stray magnetic fields by eliminating the sensed stray magnetic fields that are essentially uniform to one or two orders of magnitude at the sensing element in most circumstances. Differential processing may also include or be followed by signal processing such as, for example, amplification and filtering with a low-pass filter to eliminate high frequency noise. Chopping techniques well known in the art may be used to reduce or eliminate offsets. Linearization and / or gain correction may also be included in the signal processing. The sensors 502, 504 may accordingly generate differential magnetic field signals (dBi) for the respective orthogonal axes as shown at 516, 518 and 536, 538.

[0044]

[0050] From the differential magnetic field signal, ARCTAN(tan -1 ) processing or other suitable processing (such as by blocks 520 and 540 included in DSP 550) may be performed to determine the angles of rotation α1, α2 of each target (as indicated by angle signals 524, 544). In some embodiments, ARCTAN processing may be performed by Coordinate, Rotation, and Digital Computation (CORDIC) processing in DSP 550 or other suitable processor.

[0045]

[0051] Continuing to refer to FIG. 5, the angle signals 524, 544 are provided to a processor (DSP) 550 that configures or determines (indicated by subtraction unit 552) a difference 554 between the angles α1, α2. The processor 550 may then multiply the difference 554 by a system-defined coefficient k (indicated at 556) to obtain a value (558) indicative of the torque applied to one or more rotatable members (e.g., one or more shafts) to which the target is connected. Other quantities, such as applied power, may be calculated from the difference 554 using other defined values ​​(e.g., constants). The defined coefficient k may be a constant or a variable (e.g., temperature dependent) related, for example, to the modulus of rigidity of a material and / or the moment of inertia of a rotatable member. The output interface module 560 may generate a sensor output signal 562, including information, e.g., a torque value, in one or more formats to meet the needs of a particular application.

[0046]

[0052] In an example embodiment, the output torque value 558 may be provided in a sensor output signal 562, for example, in a serial peripheral interface (SPI), single edge nibble transmission (SENT), pulse width modulation (PWM), inter-integrated circuit (I2C), and / or analog output format. The differential flux density value and / or the angle value between the two sensors 554 may be available for output in SPI and SENT in further examples. Along with the magnetic data, the SPI and SENT options may provide access to additional device information, such as temperature error flag information and customer identification registration data.

[0047]

[0053] An embodiment of a sensor according to the present disclosure may optionally employ processing to mitigate the effects of magnetic coupling that may occur between closely spaced magnetic sensing elements and / or magnetic sensors. For closely spaced magnetic sensing elements / sensors, each differential magnetic field signal dBi (e.g., in the x and z directions) may be subject to crosstalk. By knowing the coefficient for that crosstalk, each differential signal may be modified, for example, before the ARCTAN block / processing. Such magnetic coupling mitigation may be advantageously used in embodiments where the magnetic sensors are located on a single common die. In an exemplary embodiment, a processor such as a DSP550 or similar is operable to perform such processing to mitigate the effects of magnetic coupling. For example, such mitigation may have particular utility in situations where the separation distance between sensing elements (of the same or different sensors) is on the order of a few millimeters, e.g., 3 mm, 2 mm, 1 mm, or the like.

[0048]

[0054] For each magnetic field sensing element, a processor (e.g., DSP 550) may be configured to use the combined output from each of the sensor signals (516, 518, 536, and 538) together with the known coupling coefficients from each of the targets, e.g., the ring magnet, to more accurately determine the magnetic field from the closer target, e.g., the ring magnet, at the location of the multiple magnetic sensing elements. The processor may be configured to generate coupling matrices [A] and [B] including coupling coefficients where two magnetic field directions are sensed from each target (e.g., the ring magnet) to each sensor element, as shown by processing (algorithm) block 557. The processor 550 may be further configured to extract the magnetic field from the closer target (e.g., the ring magnet) [Mx] and [Mz] for matrix equations Ax×Mx=Hx and Ay×My=Hy, e.g., via block 557, where [Ai] is the coupling matrix and [Hi] is a matrix including magnetic field signals from the multiple magnetic field sensors with magnetic sensing elements. The processor may be further configured to solve the matrix equation Ai×Mi=Hi, e.g., using a least squares method or a pseudo-inverse method, to generate an inverse matrix [Ci] such that Mi=Ci×Hi, e.g., via block 557. The processor may include a multiplier configured to multiply the magnetic field signals from each of the multiple magnetic field sensors by the matrix [Ci], e.g., via block 557, to modify the sensed magnetic field values ​​to account for mutual coupling.

[0049]

[0055] In some embodiments, the coupling matrix may accommodate and vary with air gaps and / or absolute angles, e.g., when the magnetic sensing elements are subject to crosstalk. For example, the coupling matrix may be modified to include coefficients that reflect the dependence of signal strength on distance (inverse correlation). For a given air gap, the signal strength varies inversely with the distance (size) of the air gap. The absolute value of the angle vector (the vector created from the orthogonal magnetic field measurements), i.e., =(x ∧ 2+z ∧ 2) ∧ 0.5 can be determined and the reciprocal, i.e., 1 / ((x∧ 2+z ∧ 2) ∧ 0.5) may be used to adjust the coupling matrix to accommodate a given air gap. If the angle is determined to be significant, an angle value may be calculated and introduced into the coupling matrix, and the angle calculation may be repeated, for example, one or more times to achieve a desired accuracy standard. In an example embodiment, the coupling matrix - possibly including variations due to air gap and / or angle - may be stored in a lookup table.

[0050]

[0056] 6 is a side view of an example magnetic field differential angle sensor 600 in a side shaft configuration according to the present disclosure. The sensor 600 includes first and second targets 610, 620 configured as ring magnets that are parallel to one another (orthogonal to the figure) along a torsion or rotation axis. The sensor 600 includes first and second differential magnetic field angular position sensors 604, 606 each configured as or as part of an integrated circuit (IC). Each differential magnetic field angular position sensor 604, 606 includes first and second pairs (labeled 604-1, 604-2 on the sensor 604) of orthogonally configured magnetic field sensing elements (indicated by plates bearing Z-axis and Y-axis names). As shown, a magnetic flux 630 is generated by a target, e.g., 610, with field lines shown emanating from the north pole toward the adjacent south pole of the ring magnets 610, 620. In an exemplary embodiment, the like sensing elements of each sensor pair (e.g., 604-1, 604-2) have an inter-element spacing 614 (either distance or, in a given application, air gap 616 from the target) that matches or is similar to the pole width of the respective magnetic target 610, 620, which pole width is shown in angular terms as from the centerline 615a of one pole to the centerline 615b of the adjacent pole. In an alternative embodiment, the first and second differential magnetic field angular position sensors 604, 606 may be located on a common die, e.g., a die that is perpendicular to the plane of the drawing in a side shaft configuration similar to that shown in FIG.

[0051]

[0057] 7 is a block diagram of an example computer system 700 operable to perform processing according to the present disclosure. The computer system 700 may perform all or at least a portion of the processing, e.g., steps, in the algorithms, equations, and / or methods described herein. The computer system 700 includes a processor 702, a volatile memory 704, a non-volatile memory 706 (e.g., a hard disk), an output device 708, and a user input or interface (UI) 710, e.g., a graphic user interface (GUI), a mouse, a keyboard, a display, or any common user interface. The non-volatile memory (non-transitory storage medium) 706 stores computer instructions 712 (also known as machine-readable instructions or computer-readable instructions), such as software (computer program products), an operating system 714, and data 716. In one example, the computer instructions 712 are executed by the processor 702 from outside (from) the volatile memory 704. In one embodiment, an article 718 (e.g., a storage device or medium, such as a hard disk, optical disk, magnetic storage tape, optical storage tape, flash drive, etc.) includes or stores non-transitory computer readable instructions. As shown, a bus 720 may also be included.

[0052]

[0058] The processing may be implemented in hardware, software, or a combination of the two. The processing may be implemented in a computer program executed on a programmable computer / machine, each of which includes a processor, a storage medium or other article of manufacture (including volatile and non-volatile memory and / or storage elements) readable by the processor, and optionally at least one input device, and one or more output devices. The program code may be applied to data entered using an input device or input connection (e.g., a port or bus) to perform processing and to generate output information.

[0053]

[0059] System 700 may implement processes at least in part through a computer program product (e.g., in a machine-readable storage device) for execution by or to control the operation of a data processing device (e.g., a programmable processor, a computer, or multiple computers). Each such program may be implemented in a high-level procedural or object-oriented programming language to communicate with a computer system. However, the programs may be implemented in assembly or machine language. The language may be a compiled or interpreted language, which may be deployed in any form, including as a stand-alone program or as a module, component, subroutine, or other unit suitable for use in a computing environment. A computer program may be deployed to run on one computer, or on multiple computers at one location or distributed across multiple locations and interconnected by a communication network. A computer program may be stored on a storage medium or device (e.g., a CD-ROM, a hard disk, or a magnetic diskette), which is readable by a general-purpose or special-purpose programmable computer to configure and operate the computer when the storage medium or device is read by the computer. The process may also be implemented as a machine-readable storage medium configured with a computer program, the instructions in the computer program, when executed, causing a computer to operate.

[0054]

[0060] The processing may be performed by one or more programmable processors executing one or more computer programs to perform the functions of the system. All or part of the system may be implemented as special purpose logic circuitry, such as an FPGA (field programmable gate array) and / or an ASIC (application specific integrated circuit).

[0055]

[0061] Thus, embodiments of the present disclosure may provide advantages over the prior art. Such advantages may include, but are not limited to, providing systems, sensors, and techniques that use non-contact angle measurement and / or torque sensing that are resistant to and / or tend to eliminate stray magnetic fields and the deleterious effects of such stray magnetic fields. Such non-contact angle measurement and / or torque sensing may be implemented for various types of objects and in various applications. For example, such measurement and sensing may be accomplished in the case of shafts that are only rotating slowly or that rotate by small angles, including, for example, zero (0) rpm, and in the case of angles less than, for example, 90 degrees, 45 degrees, 30 degrees, 15 degrees, 5 degrees, etc. Embodiments of the present disclosure may provide stray magnetic field robust angle and / or torque measurement using fewer and less expensive parts than conventional systems and techniques.

[0056]

[0062] Various embodiments of the concepts, systems, devices, structures, and techniques sought to be protected are described above with reference to the associated drawings. Alternate embodiments may be modified without departing from the scope of the described concepts, systems, devices, structures, and techniques. It should be noted that various connections and relationships (e.g., above, below, adjacent, etc.) may be used to describe elements in the description and drawings. These connections and / or relationships may be direct or indirect unless otherwise stated, and the described concepts, systems, devices, structures, and techniques are not intended to be limiting in this respect. Thus, coupling of entities refers to either direct or indirect coupling, and relationships between entities may be either direct or indirect relationships.

[0057]

[0063] As an example of an indirect positional relationship, positioning element "A" above element "B" may include a situation where one or more intermediate elements (e.g., element "C") are between element "A" and element "B," so long as the relative features and functionality of elements "A" and "B" are not substantially altered by the intermediate elements.

[0058]

[0064] In addition, the following definitions and abbreviations shall be used for interpretation of the claims and the specification. The terms "comprise," "comprises," "comprising," "include," "includes," "including," "has," "having," "contains," or "containing," or any other variation, are intended to cover a non-exclusive inclusion. For example, a device, method, composition, mixture, or article that includes a list of elements is not necessarily limited to only those elements and may include other elements not expressly listed or inherent to such device, method, composition, mixture, or article.

[0059]

[0065] Additionally, the term "exemplary" means serving as an example, instance, or illustration. Any embodiment or design described as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments or designs. The terms "one or more" and "at least one" refer to any integer greater than or equal to one, i.e., 1, 2, 3, 4, etc. The term "multiple" refers to any integer greater than one. The term "connected" can include a direct "connected" and an indirect "connected."

[0060]

[0066] References herein to "an embodiment," "one embodiment," "one embodiment," "example embodiment," "example," "example," "aspect," and the like indicate that the embodiment being described may include a particular feature, structure, or feature, but all embodiments may or may not include the particular feature, structure, or feature. Moreover, such phrases do not necessarily refer to the same embodiment. Furthermore, when a particular feature, structure, or feature is described in connection with one embodiment, it may affect such feature, structure, or feature in other embodiments, whether or not explicitly described.

[0061]

[0067] Relational or positional terms, including but not limited to "above," "below," "right," "left," "vertical," "horizontal," "up," "below," and derivatives of these terms, refer to the described structures and methods as oriented in the drawings. The terms "overlying," "atop," "on top," "positioned on," and "positioned atop" mean that a first element, such as a first structure, is above a second element, such as a second structure, and that an intervening element, such as an interface structure, may be between the first and second elements. The term "direct contact" means that a first element, such as a first structure, and a second element, such as a second structure, are connected without any intermediate elements.

[0062]

[0068] The use of ordinal terms such as "first," "second," "third," etc. in the claims to modify claim elements does not, in itself, imply any priority, precedence, or ordering of one claim element over another, or the temporal order in which acts of a method are performed, but is merely used as a label to distinguish one claim element having a particular name from another element having the same name (through the use of ordinal terms) to distinguish the claim elements.

[0063]

[0069] The terms "approximately" and "about" may be used in some embodiments to mean within ±20% of a target value, in some embodiments within plus or minus (±) 10% of a target value, in some embodiments within ±5% of a target value, and even in some embodiments within ±2% of a target value. The terms "approximately" and "about" may include the target value. The term "substantially equal" may be used in some embodiments to refer to values ​​that are within ±20% of each other, in some embodiments within ±10% of each other, in some embodiments within ±5% of each other, and even in some embodiments within ±2% of each other.

[0064]

[0070] The term "substantially" may be used to refer to values ​​that are within ±20% of a comparative measurement in some embodiments, within ±10%, within ±5%, and even within ±2% in some embodiments. For example, a first direction that is "substantially" perpendicular to a second direction may refer to a first direction that is within ±20% of making a 90° angle with the second direction in some embodiments, within ±10% of making a 90° angle with the second direction in some embodiments, within ±5% of making a 90° angle with the second direction, and even within ±2% of making a 90° angle with the second direction in some embodiments.

[0065]

[0071] The disclosed subject matter is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings The disclosed subject matter is capable of other embodiments and of being practiced and carried out in various ways.

[0066]

[0072] Moreover, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. As such, the conception on which this disclosure is based may be readily utilized as a basis for the design of other structures, methods and systems for carrying out some of the purposes of the disclosed subject matter. It is therefore intended that the claims be deemed to include such equivalent constructions insofar as they do not depart from the spirit and scope of the disclosed subject matter.

[0067]

[0073] While the disclosed subject matter has been described and illustrated in the foregoing exemplary embodiments, the present disclosure is made by way of example only, and thus, numerous changes in the details of the implementation of the disclosed subject matter may be made without departing from the spirit and scope of the disclosed subject matter.

[0068]

[0074] Therefore, the scope of this patent should not be limited to the described implementations, but rather should be limited only by the spirit and scope of the appended claims.

[0069]

[0075] All publications and references cited in this patent are expressly incorporated by reference in their entirety.

Claims

1. 1. A differential magnetic field torque sensor comprising: a first multi-pole magnet assembly having a plurality of pole pairs and configured for coupling to a first rotatable shaft; a second multi-pole magnet assembly having a plurality of pole pairs and configured for coupling to a second rotatable shaft, the first rotatable shaft being coupled to the second rotatable shaft by a resilient element; and a first differential magnetic field angular position sensor positioned proximate to the first multi-pole magnet assembly and configured to generate an angular position of the first multi-pole magnet assembly; a second differential magnetic field angular position sensor positioned proximate to the second multi-pole magnet assembly and configured to generate an angular position of the second multi-pole magnet assembly; a processing device operable to receive an angular position from each of the first and second differential magnetic field angular position sensors and determine a difference in said angular positions, said difference corresponding to an angle, said processing device operable to calculate a torque to be applied to the first or second rotatable shaft based on said angle; 1. A differential magnetic field torque sensor comprising:

2. Each of the first and second differential magnetic field angular position sensors comprises: (i) a first array of magnetic field sensing elements; (ii) a second array of magnetic field sensing elements, the first array of magnetic field sensing elements being spaced a distance from the second array of magnetic field sensing elements, the first and second arrays of magnetic field sensing elements each having at least first and second axes of maximum sensitivity, the first axis of maximum sensitivity being orthogonal to the second axis of maximum sensitivity; and (iii) an angular position module for determining an angular position of the adjacent multi-pole magnet assembly from a differential signal from the first and second arrays of magnetic field sensing elements. The sensor of claim 1 , comprising:

3. The sensor of claim 1 , wherein the first or second differential magnetic field angular position sensor comprises a Hall effect element.

4. The sensor of claim 1 , wherein the first or second differential magnetic field angular position sensor comprises a magnetoresistive element.

5. 3. The sensor of claim 2, wherein for the first differential magnetic field angular position sensor, a distance that the first array of magnetic field sensing elements is spaced from the second array of magnetic field sensing elements is configured to match a pitch of adjacent pole pairs of the first multi-pole magnet assembly.

6. 6. The sensor of claim 5, wherein for the second differential magnetic field angular position sensor, a distance that the first array of magnetic field sensing elements is spaced from the second array of magnetic field sensing elements is configured to match a pitch of adjacent pole pairs of the second multi-pole magnet assembly.

7. The sensor of claim 2 , wherein the angular position module comprises an arctangent calculation module.

8. The sensor of claim 1 , wherein the first or second multi-pole magnet assembly comprises a ring magnet.

9. The sensor of claim 2 , wherein for the first differential magnetic field angular position sensor, the differential signals from the first and second arrays of magnetic field sensing elements include a sine signal and a cosine signal.

10. The sensor of claim 2 , wherein for the second differential magnetic field angular position sensor, the differential signals from the first and second arrays of magnetic field sensing elements include a sine signal and a cosine signal.

11. The sensor of claim 1 , wherein the resilient element comprises a torsion bar.

12. 2. The sensor of claim 1, further comprising first and second sleeves, each having a proximal end and a distal end, the first sleeve coupled to the first rotatable shaft at the proximal end and to the first multi-pole magnet assembly at the distal end, and the second sleeve coupled to the second rotatable shaft at the proximal end and to the second multi-pole magnet assembly at the distal end.

13. 13. The sensor of claim 12, wherein the first and second multi-pole magnet assemblies are concentrically disposed in a common plane in an end shaft configuration, the first multi-pole magnet assembly having a first radius and the second multi-pole magnet assembly having a second radius different than the first radius.

14. The sensor of claim 13 , wherein the first and second differential magnetic field angular position sensors are disposed on a common die in an end-shaft configuration.

15. The sensor of claim 14 , wherein the common die is disposed adjacent to the first and second multi-pole magnet assemblies and parallel to the common plane.

16. The sensor of claim 13 , wherein the first and second multi-pole magnet assemblies are disposed in first and second parallel planes, respectively, in a side-shaft configuration.

17. The sensor of claim 16 , wherein the first and second differential magnetic field angular position sensors are disposed on a common die.

18. The sensor of claim 17 , wherein the common die is disposed adjacent the first and second multi-pole magnet assemblies and perpendicular to the parallel plane in a side shaft configuration.

19. The sensor of claim 2 , wherein the angular position module is operable to calculate a coupling matrix for magnetic coupling between the first array of magnetic field sensing elements and the second array of magnetic field sensing elements.

20. 20. The sensor of claim 19, wherein the angular position module is further operable to calculate an inverse matrix based on the coupling matrix and to modify the differential signals from the first and second arrays of magnetic field sensing elements.

21. The sensor of claim 1 , wherein the processing unit is operable to calculate a coupling matrix for magnetic coupling between the first differential magnetic field angular position sensor and the second differential magnetic field angular position sensor.

22. 22. The sensor of claim 21, wherein the processing unit is further operable to calculate an inverse matrix based on the coupling matrix and to correct the angular positions from the first and second differential magnetic field angular position sensors.

23. 1. A differential magnetic field angle sensor comprising: first and second targets, each configured for coupling to a rotatable element; means for detecting a differential angular position, the means being operable to generate respective output signals indicative of the differential angular positions of the first and second targets; a processing device operable to receive the respective output signals from the means for detecting a differential angular position, and to calculate a difference in the angular positions, the difference corresponding to an angle between the first target and the second target; 1. A differential magnetic field angle sensor comprising:

24. The sensor of claim 23 , wherein the processor is configured to calculate a torque to be applied to the rotatable element based on the angle.

25. The sensor of claim 23 , wherein the processor is configured to calculate a power to be applied to the rotatable element based on the angle.

26. The sensor of claim 23 , wherein the first or second magnetic target comprises a multi-pole magnet assembly having multiple pole pairs.

27. 27. The sensor of claim 26, wherein the multi-pole magnet assembly comprises a ring magnet.

28. The sensor of claim 23 , wherein the rotatable element comprises a shaft.

29. 30. The sensor of claim 28, wherein the shaft comprises first and second shafts coupled by a resilient element.

30. 30. The sensor of claim 29, wherein the resilient element comprises a torsion bar.

31. 30. The sensor of claim 29, wherein the first and second shafts comprise a steering column.

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