Absolute position measurement using a single magnetic stripe

Abstract

Embodiments of the present disclosure relate to absolute position measurement using a single magnetic stripe. An absolute position measurement system includes a multipole magnet comprising alternating magnetic poles extending along a multipole extension direction, the multipole magnet having a linearly varying configuration with respect to a linear path and generating a magnetic field, a field strength of the magnetic field undergoing a sinusoidal variation along the linear path due to the alternating magnetic poles and a linear variation along the linear path according to the linearly varying configuration with respect to the linear path; and a magnetic sensor configured to move along the linear path. The magnetic sensor comprises: a first sensor element arrangement configured to generate a first sensor signal; a second sensor element arrangement configured to generate a second sensor signal phase-shifted with respect to the first sensor signal; and a processing circuitry configured to calculate an absolute position of the magnetic sensor based on the first sensor signal and the second sensor signal.

Description

TECHNICAL FIELD

[0001] The present disclosure relates generally to position sensing, and more particularly, to absolute position sensing using a magnetic field sensor and a single magnetic strip. BACKGROUND

[0002] Linear magnetic position sensors can sense linear motion relative to a multipole magnetic strip. Absolute linear motion measurement can be made using the Nonius-Vernier principle, but it requires two multipole magnetic strips and two magnetic sensors. The Nonius-Vernier principle allows absolute position to be measured by two tracks consisting of periodic divisions. The number of periods of the two tracks must differ by one, and they must be in phase at both ends. The one with more periods is called the main track, and the other is called the Nonius track. However, the requirement of using two multipole magnetic strips and two magnetic sensors increases cost and space.

[0003] Absolute linear motion can also be measured by measuring relative position using a single multipole magnetic strip, but the measurement requires a reference position to determine absolute position at system power-up reset. That is, every time the system is powered up, the position of the sensor relative to the multipole magnetic strip needs to be set back to a reference position. However, certain applications do not allow the sensor to be moved back to the reference position at every power-up reset. Therefore, this technique cannot be used for those applications.

[0004] Accordingly, there can be a need for an absolute linear position measurement system that does not require two multipole magnetic strips and does not require power-up reset to a reference position. SUMMARY

[0005] Magnetic sensor modules, systems, and methods are provided that are configured to detect absolute position of an object.

[0006] One or more embodiments provide an absolute position measurement system, comprising: a multipole magnet comprising alternating magnetic poles extending along a multipole extension direction, wherein the multipole magnet has a linearly varying configuration relative to a linear path, and the multipole magnet is configured to generate a magnetic field along the linear path; and a magnetic sensor configured to move along the linear path. The magnetic sensor comprises a first sensor element arrangement configured to generate a first sensor signal in response to the magnetic field, and a second sensor element arrangement configured to generate a second sensor signal in response to the magnetic field. As the magnetic sensor moves along the linear path, the first sensor signal has a first sinusoidal waveform having a first linearly varying peak-to-peak amplitude, and the second sensor signal has a second sinusoidal waveform having a second linearly varying peak-to-peak amplitude, wherein the second sinusoidal waveform is phase-shifted relative to the first sinusoidal waveform. The magnetic sensor further comprises processing circuitry configured to receive the first sensor signal and the second sensor signal and compute an absolute position of the magnetic sensor based on the first sensor signal and the second sensor signal.

[0007] One or more embodiments provide an absolute position measurement system, comprising: a multipole magnet comprising alternating magnetic poles extending along a multipole extension direction, wherein the multipole magnet has a linear variation configuration relative to a linear path, and the multipole magnet is configured to generate a magnetic field along the linear path, the magnetic field having a strength that experiences a sinusoidal variation along the linear path due to the alternating magnetic poles and a linear variation along the linear path according to the linear variation configuration relative to the linear path; and a magnetic sensor configured to move along the linear path. The magnetic sensor comprises a first sensor element arrangement configured to generate a first sensor signal and a second sensor element arrangement configured to generate a second sensor signal that is phase-shifted relative to the first sensor signal. The magnetic sensor further comprises a processing circuit configured to receive the first sensor signal and the second sensor signal, and to compute an absolute position of the magnetic sensor based on the first sensor signal and the second sensor signal.

[0008] One or more embodiments provide an absolute position measurement system, comprising: a multipole magnet comprising alternating magnetic poles extending along a multipole extension direction, the multipole extension direction coinciding with a linear path, the multipole magnet configured to move along the linear path, wherein the multipole magnet has a linear configuration that changes relative to a fixed position as the multipole magnet moves along the linear path, wherein the multipole magnet is configured to generate a magnetic field at the fixed position; and a magnetic sensor movably fixed at the fixed position. The magnetic sensor comprises a first sensor element arrangement configured to generate a first sensor signal in response to the magnetic field and a second sensor element arrangement configured to generate a second sensor signal in response to the magnetic field. As the magnetic sensor moves along the linear path, the first sensor signal has a first sinusoidal waveform having a first linearly varying peak-to-peak amplitude, and the second sensor signal has a second sinusoidal waveform having a second linearly varying peak-to-peak amplitude, wherein the second sinusoidal waveform is phase-shifted relative to the first sinusoidal waveform. The magnetic sensor further comprises a processing circuit configured to receive the first sensor signal and the second sensor signal, and to compute an absolute position of the multipole magnet based on the first sensor signal and the second sensor signal.

[0009] One or more embodiments provide a method of computing an absolute position of a magnetic sensor, the method comprising: generating, by a first sensor element arrangement of the magnetic sensor, a first sensor signal in response to a magnetic field; generating, by a second sensor element arrangement of the magnetic sensor, a second sensor signal in response to the magnetic field, wherein, as the magnetic sensor moves along a linear path, the first sensor signal has a first sinusoidal waveform having a first linearly varying peak-to-peak amplitude, and the second sensor signal has a second sinusoidal waveform having a second linearly varying peak-to-peak amplitude, wherein the second sinusoidal waveform is phase shifted relative to the first sinusoidal waveform; and processing circuitry computing the absolute position of the magnetic sensor from the first and second sensor signals. BRIEF DESCRIPTION OF DRAWINGS

[0010] Embodiments are described herein with reference to the accompanying drawings.

[0011] Figure 1 A schematic block diagram of an absolute linear position sensor 100 is shown in accordance with one or more embodiments;

[0012] Figure 2 is a top view of an absolute linear positioning system in accordance with one or more embodiments;

[0013] Figure 3 is a top view of an absolute linear position system in accordance with one or more embodiments, and a corresponding side view of the absolute linear position system;

[0014] Figure 4A and Figure 4B Determining an absolute angle from single point polar coordinate P(0, r) measurements is shown in accordance with one or more embodiments;

[0015] Figure 5 is a flowchart of a method for computing a runtime absolute linear position in accordance with one or more embodiments; and

[0016] Figures 6A-6D An absolute linear positioning system with an alternative magnetic sensor arrangement is shown in accordance with one or more embodiments. DETAILED DESCRIPTION

[0017] In the following, details are set forth to provide a more thorough explanation of exemplary embodiments. It will be apparent, however, that the embodiments can be practiced without these specific details. In other instances, well known structures and devices are shown in block diagram form or in schematic form to avoid obscuring the embodiments. Additionally, the features of the different embodiments described hereinafter can be combined with each other, unless specifically noted otherwise. It is also understood that other embodiments can be used and structural or logical changes can be made without departing from the scope defined by the claims. Accordingly, the following detailed description is not to be taken in a limiting sense.

[0018] Furthermore, identical or similar elements or elements having identical or similar functions are denoted by the same reference numerals throughout the description and drawings of the present disclosure. Description of identical or similar elements is not redundant in the description of this disclosure. Accordingly, the description of identical or similar elements can be interchanged.

[0019] Directional terms, such as "top," "bottom," "front," "back," "positioned on," "positioned below," "positioned above," "positioned behind," "positioned in front of," "positioned on top of," "positioned below," and the like, can be used with respect to the described drawings and / or elements therein. Because embodiments can be positioned in a number of different orientations, directional terms are used for illustrative purposes and not limitation. In some cases, directional terms can be exchanged with equivalent directional terms based on the orientation of the embodiment, as long as the general directional relationship between elements and their general purpose are maintained.

[0020] In the present disclosure, expressions including ordinal numbers, such as "first," "second," and the like, can modify various elements. However, the elements are not limited by the above expressions. For example, the above expressions do not limit the sequence and / or importance of the elements. The above expressions are used merely to distinguish an element from another element. For example, a first block and a second block represent different blocks although both of them are blocks. For example, a first element can be referred to as a second element, and similarly, a second element can be referred to as a first element without departing from the scope of the present disclosure.

[0021] It is understood that when a component is referred to as being "connected" or "coupled" to another component, it can be directly connected or coupled to the other component, or intervening components can be present. In contrast, when a component is referred to as being "directly connected" or "directly coupled" to another component, there are no intervening components present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., "between" versus "directly between," "adjacent" versus "directly adjacent," etc.).

[0022] In the embodiments described herein or shown in the figures, any direct electrical connection or coupling, i.e. any connection or coupling without additional intervening elements, can also be realized by an indirect connection or coupling, i.e. a connection or coupling with one or more additional intervening elements, and vice versa, as long as the general purpose of the connection or coupling, e.g. the transmission of a particular type of signal or the transmission of a particular type of information, is substantially maintained. Features of different embodiments can be combined to form further embodiments. For example, variations or modifications described in one of the embodiments can also be applicable to the other embodiments, unless otherwise stated.

[0023] According to certain implementation requirements, the storage medium can include RAM, ROM, PROM, EPROM, EEPROM, flash memory, or any other medium that stores electronically readable control signals which co-operate with (or are capable of co-operating with) a programmable computer system so that a corresponding method is carried out. The storage medium can therefore be regarded as a computer-readable non-transitory storage medium.

[0024] Furthermore, the instructions can be executed by one or more processors, such as one or more central processing units, digital signal processors, general purpose microprocessors, application specific integrated circuits, field programmable logic arrays or other equivalent integrated or discrete logic circuitry. Accordingly, the term "processor", as used herein can refer to any of the foregoing structure or any other structure suitable for implementation of the techniques described herein. In addition, in some aspects, the functionality described herein can be provided within dedicated hardware and / or software modules. Also, the techniques could be fully implemented in one or more circuits or logic elements. The "controller" comprising one or more processors can use electrical signals and digital algorithms to perform its receiving, analyzing and control functions, which can also include corrective functions.

[0025] Signal conditioning as used herein refers to processing of an analog signal in a manner that the signal meets the requirements of the next stage for further processing. Signal conditioning can include conversion from analog to digital (e.g. by an analog-to-digital converter), amplification, filtering, conversion, biasing, range matching, isolation, and any other process that makes the sensor output suitable for the required post-conditioning processing.

[0026] Embodiments relate to sensors and sensor systems, and to acquiring information about sensors and sensor systems. A sensor can refer to a component that converts a physical quantity to be measured into an electrical signal, e.g. a current signal or a voltage signal. The physical quantity can for example include a magnetic field, an electric field, a pressure, a force, an electric current, or a voltage, but is not limited thereto. As described herein, a sensor device can be a linear position sensor that measures an absolute position of an object by sensing a magnetic field.

[0027] For example, a magnetic field sensor includes one or more magnetic field sensor elements that measure one or more characteristics of a magnetic field (e.g., magnetic field flux density, field strength, field angle, field direction, field orientation, etc.). The magnetic field can be generated by a magnet, a current-carrying conductor (e.g., an electrical wire), the Earth, or other magnetic field source. Each magnetic field sensor element is configured to generate a sensor signal (e.g., a voltage signal) in response to one or more magnetic fields affecting the sensor element. Thus, the sensor signal is indicative of the magnitude and / or direction of the magnetic field affecting the sensor element.

[0028] According to one or more embodiments, the magnetic field sensor and the sensor circuit are both housed (i.e., integrated) in the same chip package (e.g., a plastic-encased package, such as a leaded or leadless package, or a surface mount device (SMD) package). This chip package is also referred to as a sensor package. The sensor assembly can be combined with an anti-bias magnet to form a sensor module, a sensor device, etc.

[0029] Thus, the one or more magnetic field sensor elements included in the sensor assembly are exposed to a magnetic field, and, for example, the sensor signal (e.g., a voltage signal) provided by each magnetic field sensor element is proportional to the magnitude of the magnetic field. Moreover, it should be understood that the terms "sensor" and "sensing element" can be used interchangeably in this specification, and the terms "sensor signal" and "measurement" can be used interchangeably in this specification.

[0030] The sensor circuit can be referred to as a signal processing circuit and / or a signal conditioning circuit that receives signals (i.e., sensor signals) from the magnetic field sensor elements in the form of raw measurement data and derives a measurement signal representative of the magnetic field from the sensor signals. The sensor circuit can include an analog-to-digital converter (ADC) that converts the analog signals from the one or more sensor elements into digital signals. The sensor circuit can also include a digital signal processor (DSP) that performs certain processing on the digital signals, which will be discussed below. Thus, the sensor assembly includes circuitry that conditions and amplifies the small signals of the magnetic field sensor elements through signal processing and / or conditioning.

[0031] A sensor device as used herein can refer to a device that includes a sensor and a sensor circuit as described above. The sensor device can be integrated on a single semiconductor chip (e.g., a silicon die or chip), although in other embodiments multiple chips can be used to implement the sensor device. Thus, the sensor and the sensor circuit are disposed on the same semiconductor die or on multiple dies in the same package. For example, the sensor can be on one die and the sensor circuit can be on another die such that they are electrically connected to each other within the package. In this case, the dies can be composed of the same or different semiconductor materials, e.g., GaAs and silicon, or the sensor can be sputtered onto a ceramic or glass sheet that is not a semiconductor.

[0032] Magnetic field sensor elements include, but are not limited to, Hall effect devices and magnetoresistive sensors, commonly referred to as XMR sensors, a collective term for anisotropic magnetoresistive (AMR) sensors, giant magnetoresistive (GMR) sensors, tunneling magnetoresistive (TMR) sensors, etc.

[0033] A vertical Hall sensor is a magnetic field sensor composed of a Hall element perpendicular to the plane of the sensor chip (e.g., extending from the main surface of the chip to the bulk of the chip). It senses magnetic fields perpendicular to its defined sensitive edge (up, right, or left with respect to the main surface of the chip). This generally means that a vertical Hall sensor is sensitive to magnetic field components that extend parallel to its surface and parallel to or within the main surface of the chip in which the integrated vertical Hall sensor is located. In particular, a vertical Hall sensor can extend vertically from the main surface into the chip (e.g., into the semiconductor substrate). The plane of sensitivity can be referred to herein as a "sensitivity axis" or "sensing axis," and each sensing axis has a reference direction. For a vertical Hall sensor element, the voltage value output by the sensor element varies as a function of the magnetic field strength in the direction of its sensing axis. For the purposes of this disclosure, the main surface of the sensor chip is defined in the XY plane, and the vertical Hall sensor is sensitive to fields in the XY plane (e.g., the X direction, the Y direction, or directions therebetween).

[0034] On the other hand, a lateral (planar) Hall sensor is composed of a Hall element in the same plane as the main surface of the sensor chip. It senses magnetic fields perpendicular to its plane. This means that they are sensitive to magnetic fields that are perpendicular to the main surface of the chip or out of plane. The plane of sensitivity can be referred to herein as a "sensitivity axis" or "sensing axis," and each sensing axis has a reference direction. Similar to a vertical Hall sensor element, the voltage value output by a lateral Hall sensor element varies as a function of the magnetic field strength in the direction of its sensing axis. For the purposes of this disclosure, the main surface of the sensor chip is defined within the XY plane, and the lateral Hall sensor is sensitive to fields aligned in the Z direction, which is perpendicular to the XY plane.

[0035] Figure 1A schematic block diagram of an absolute linear position sensor 100 is shown in accordance with one or more embodiments. The absolute linear position sensor 100 includes a magnetic field sensor 110 that includes a first sensor bridge circuit that includes magnetic field sensor elements 111-114 that are sensitive to a first in-plane magnetic field component (e.g., x-component) generated by a linear multi-pole strip magnet 150 (not shown). The magnetic field sensor elements 111-114 are XMR sensor elements arranged in a Wheatstone bridge configuration, with two output terminals VP1 and VN1 tapped from each leg of the bridge. The first sensor bridge circuit is configured to output a first output signal V1 that is a differential voltage between the output terminals VP1 and VN1. In this embodiment, the first output signal V1 represents a cosine sensor signal.

[0036] The magnetic field sensor 110 also includes a second sensor bridge circuit that includes magnetic field sensor elements 115-118 that are also sensitive to the first in-plane magnetic field component (e.g., x-component) of the linear multi-pole strip magnet 150. The magnetic field sensor elements 115-118 are XMR sensor elements arranged in a Wheatstone bridge configuration, with two output terminals VP2 and VN2 tapped from each leg of the bridge. The second sensor bridge circuit is configured to output a second output signal V2 that is a differential voltage between the output terminals VP2 and VN2. In this embodiment, the second output signal V2 represents a sine sensor signal. In other words, the two output signals V1 and V2 have a 90° phase shift from each other. The 90° phase shift is generated with respect to the pole pitch of the linear multi-pole strip magnet 150 due to the spacing or distance between the two bridge circuits. It will be understood that the output signal V2 can be considered a cosine signal and the output signal V1 can be considered a sine signal, or vice versa. The two output signals V1 and V2 are provided to a sensor circuit 120 of the magnetic field sensor 110 and used for the calculation and determination of the absolute linear position.

[0037] The magnetization direction of the reference layers of the magneto resistors of the first sensor bridge circuit 111-114 is parallel or anti-parallel to the magnetization direction of the second reference layers of the magneto resistors of the second sensor bridge circuit 115-118. The magnetization direction of the reference layers can be parallel or anti-parallel to the magnetic field component that is to be sensed. The magneto resistors of the first sensor bridge circuit 111-114 and the magneto resistors of the second sensor bridge circuit 115-118 are arranged in a plane on the same substrate. The centers of the respective first sensor bridge circuit 111-114 and second sensor bridge circuit 115-118 are spaced apart by a physical distance along the sensor x-axis.

[0038] It is also noted that magnetic field sensor elements 116a and 116b are connected in parallel in the upper segment of the right leg of the second sensor bridge circuit, and magnetic field sensor elements 117a and 117b are connected in parallel in the lower segment of the left leg of the second sensor bridge circuit (i.e., diagonally opposite the upper right segment).

[0039] Magnetic field sensor elements 116a and 116b are located on opposite sides of the sensor IC (e.g., 116a on the right and 116b on the left), and magnetic field sensor element 115 is located in the center of the sensor IC. In this way, the measurements by 116a and 116b are combined from two different locations in one leg of the bridge, and have the same total resistance as magnetic field sensor element 115 placed in the center of the bridge, which forms the opposite leg.

[0040] Likewise, magnetic field sensor elements 117a and 117b are located on opposite sides of the sensor IC (e.g., 117a on the right and 117b on the left), and magnetic field sensor element 118 is located in the center of the sensor IC. In this way, the measurements by 117a and 117b are combined from two different locations in one leg of the bridge, and have the same total resistance as magnetic field sensor element 118 placed in the center of the bridge, which forms the opposite leg.

[0041] It is also noted that magnetic field sensor 110 is not limited to XMR sensor elements. For example, due to sensitivity to in-plane magnetic field components, vertically oriented Hall effect sensor elements can be used that are appropriately spaced apart relative to one another to generate two output signals VI and V2 that have a 90° phase shift relative to one another. For example, the first sensor bridge circuit can be replaced with one or more first Hall effect sensor elements, and the second sensor bridge circuit can be replaced with one or more second Hall effect sensor elements. The sensor signals from the first Hall effect sensor elements can be combined by sensor circuit 120 in a manner that generates first output signal VI, and the sensor signals from the second Hall effect sensor elements can be combined by sensor circuit 120 in a manner that generates second output signal V2.

[0042] Sensor circuit 120 can include at least one processor and one or more signal conditioning components that enable the sensor circuit to process output signals VI and V2 and ultimately determine an absolute linear position of absolute linear position sensor 100 relative to linear multi-pole bar magnet 150 and / or relative to a series of linear positions. The absolute linear position can refer to an absolute linear position of the sensor on its linear path 202, an absolute linear (minimum) distance d of the sensor 100 to the magnet 150, or in the case where the sensor 100 is fixed and the magnet 150 is movable, the absolute linear position can refer to an absolute linear position of the magnet on its linear path 201.

[0043] The sensor circuit 120 is configured to perform an absolute position measurement. It comprises a converter 130 for converting the two output signals V1 and V2 from the (V1, V2 space) into a measurement signal S in polar coordinates space (0, r) polar where 0 is the angle coefficient and r is the radius coefficient. Each point in the polar coordinates space is determined by the distance (i.e. the radius) from a reference point and the angle 0 from a reference direction (e.g. from the V1 axis).

[0044] The sensor circuit 120 further comprises an absolute position calculation unit 140, which receives the measurement signal S polar and computes therefrom an absolute linear position. The absolute position calculation unit 140 then generates a position output signal Spos representing the absolute linear position. The converter 130 and the absolute position calculation unit 140 can be the same or different processors, which are respectively configured to perform the signal conversion and the absolute linear position calculation. Thus, the sensor circuit 120 comprises one or more processors or processing circuits configured to determine the absolute linear position based on the output signals V1 and V2.

[0045] Figure 2 is a top view of an absolute linear positioning system 200 according to one or more embodiments. The absolute linear position system 200 comprises the absolute linear position sensor 100 and a linear multi-pole strip magnet 150. The linear multi-pole strip magnet 150 has a plurality of pole pairs 212-S, 212-N extending along a multi-pole extension direction 201 (i.e. a magnetic axis). The multi-pole extension direction 201 is also a center axis of the multi-pole strip magnet 150, which extends in a longitudinal dimension of the multi-pole strip magnet 150 and through the center of each pole 212-S, 212-N. Further, the south and north magnetic poles 212-S, 212-N of the multi-pole strip magnet 150 each have a width p corresponding to a pole pitch of the multi-pole strip magnet 150.

[0046] The position (e.g. distance) of the absolute linear position sensor 100 changes relative to the multi-pole strip magnet 150 as one of the two (magnetic poles) is moved along a linear trajectory (path). For example, the multi-pole strip magnet 150 can be fixed in place and the absolute linear position sensor 100 is configured to move along a linear path 202. The linear path 202 corresponds to an x-direction, which is also the direction of movement or displacement of the absolute linear position sensor 100. Alternatively, the absolute linear position sensor 100 can be fixed in place and the multi-pole strip magnet 150 can be configured to move along the multi-pole extension direction 201, which also serves as a linear path. In either case, the two lines 201 and 202 have an angular displacement

[0047] Furthermore, the linear path 202 is vertically overlapping with the multipole bar magnet 150. The lines 201 and 202 can intersect at one end of the multipole bar magnet 150, but this is not required.

[0048] As an angular displacement As a result, the strength of the magnetic field (e.g., the strength of the x-component of the magnetic field) varies linearly along the x-direction (i.e., along the linear path 202). As the absolute linear position sensor 100 moves along the linear path 202, the amplitude of the magnetic field varies based on two factors, including: (1) a sinusoidal variation due to the alternating arrangement of magnetic north and south poles; and (2) a linear variation due to the increasing or decreasing distance of the absolute linear position sensor 100 relative to the multipole bar magnet 150 (i.e., relative to the multipole extension direction 201). The linear variation is a linear increase or linear decrease in the peak-to-peak amplitude of the magnetic field along the linear path 202.

[0049] As the distance between the absolute linear position sensor 100 and the multipole bar magnet 150 increases, the strength (peak-to-peak amplitude) of the x-component of the magnetic field detectable at the absolute linear position sensor 100 decreases. Conversely, as the distance between the absolute linear position sensor 100 and the multipole bar magnet 150 decreases, the strength (peak-to-peak amplitude) of the x-component of the magnetic field detectable at the absolute linear position sensor 100 increases.

[0050] The output signals V1 and V2 represent both the sinusoidal variation and the linear variation in the strength of the magnetic field in the x-component as the position (e.g., distance) of the absolute linear position sensor 100 relative to the multipole bar magnet 150 changes. Thus, the output signals V1 and V2 are both damped sinusoidal signals that are 90° out of phase with respect to each other. As the absolute linear position sensor 100 moves along the linear path 202, the sinusoidal curves of the output signals V1 and V2 experience a linear variation in peak-to-peak amplitude. As the sensor 100 moves in the positive x-direction, the distance between the sensor 100 and the multipole bar magnet 150 increases, and the amplitude of the sinusoidal curves of the output signals V1 and V2 decreases. As the sensor 100 moves in the negative x-direction, the distance between the sensor 100 and the multipole bar magnet 150 decreases, and the amplitude of the sinusoidal curves of the output signals V1 and V2 increases. Thus, the linear amplitude of the sinusoidal curves depends on the absolute linear position variation of the absolute linear position sensor 100 relative to the multipole bar magnet 150, and thus also on the absolute linear position of the sensor 100 on the linear path 202.

[0051] As described above, the converter 130 is configured to convert the two output signals V1 and V2 from the (V1, V2 space) to a measurement signal S polar in the polar coordinate space (0, r), where 0 is the angular coefficient and r is the radius coefficient. This conversion is performed by the converter 130 according to the following equations: V1 = S cos(0) V2 = S sin(0) where V1 and V2 are the output signals from the (V1, V2 space), S is the measurement signal in the polar coordinate space (0, r), and 0 is the angular coefficient.Figure 2 The result is the measurement signal S polar whose representation has a spiral pattern that decreases in amplitude as the sensor 100 moves along the linear path 202 in the positive x-direction and increases in amplitude as the sensor 100 moves along the linear path 202 in the negative x-direction. The spiral pattern is at maximum amplitude when the sensor 100 is located directly above the leftmost side of the multipole bar magnet 150. The amplitude of the measurement signal S polar continuously increases or decreases based on the linear motion of the sensor 100 according to the spiral pattern.

[0052] The above principle can be described as measuring absolute position by linearly decreasing / increasing magnetic field variations on linear motion using two decreasing / increasing sinusoidal signals V1 and V2 from two discrete linearized XMR bridges.

[0053] Figure 3 is a top view of the absolute linear positioning system 200 with a corresponding side view of the absolute linear positioning system 200 according to one or more embodiments. In the top view, the sensor 100 is arranged on a printed circuit board (PCB) 203 with a y-offset relative to the multipole bar magnet 150 such that the linear path 202 intersects the multipole extension direction 201 at a predetermined position (e.g., above the first magnetic pole disposed at one end of the multipole bar magnet 150). Furthermore, in the side view, an operational linear range L is defined. The operational linear range L is the range of movement in which the sensor 100 can move and map to absolute linear positions within this range.

[0054] For example, the outer endpoint of the spiral pattern of the measurement signal S polar is mapped to the left edge of the operational linear range L, and the inner endpoint of the spiral pattern of the measurement signal S polar is mapped to the right edge of the operational linear range L. When the sensor 100 moves outside the operational linear range L, the sensor circuit 120 is unable to calculate the absolute linear position. Therefore, the operational linear range L is defined by a predetermined x-offset relative to the multipole bar magnet 150.

[0055] The absolute position calculation unit 140 is configured to determine the absolute linear position of the sensor 100 along the linear path 202 within the operational linear range L by evaluating the polar coordinates P(0, r) of the measurement signal S polar . That is, it evaluates the angular component 0 of the measurement signal S polar relative to the V1 and V2 axes and the radial component (i.e., amplitude component) of the measurement signal S polar . The amplitude of the measurement signal S polarrepeats, which is a property of the spiral pattern. However, when the angular component θ is considered in combination with the radial component r, the exact position can be determined. In other words, the polar coordinates P(θ, r) measure the signal S polar The absolute linear position of the sensor 100 along the linear path 202 within the operational linear range L is unique. The polar coordinates P(θ, r) are in one-to-one correspondence with the absolute position.

[0056] Figure 4A and 4B Fig. 6 illustrates the determination of absolute angles from single-point polar coordinate P(θ, r) measurements according to one or more embodiments. The absolute position calculation unit 140 then converts the absolute angles into absolute linear positions of the sensor 100 along the linear path 202 within the operational linear range L by applying the absolute angles to a position conversion algorithm (e.g., Equation 1).

[0057] In Figure 4A , the plurality of absolute angles θ abs1 , θ abs2 , θ abs3 ,... θ absN are mapped to corresponding polar coordinates P1(θ1, r1), P2(θ1, r2), P3(θ1, r3),... PN(θ K , r J ) by a function f, where J and K are arbitrary integers, and N is the number of polar coordinates. The applied function f establishes a one-to-one correspondence between each absolute angle and a different polar coordinate P. Alternatively, the mapping can be performed directly between absolute linear positions and corresponding polar coordinates. In other words, the applied function establishes a one-to-one correspondence between each absolute linear position along the linear path 202 within the operational linear range L and a different polar coordinate P. Furthermore, the absolute angles can be linked to the absolute linear positions of the absolute angles, respectively, and used to further determine the absolute linear positions based on their correspondence.

[0058] Alternatively, the absolute position calculation unit 140 can include a look-up table (LUT) that stores absolute angle values linked to polar coordinates, and the LUT outputs the absolute angle corresponding to the measured polar coordinates P(θ, r) received from the converter 130. Alternatively, the absolute position calculation unit 140 can include a LUT that stores absolute linear positions linked to polar coordinates, and the LUT outputs the absolute linear position corresponding to the measured polar coordinates P(θ, r) received from the converter 130.

[0059] In Figure 4B , the absolute position calculation unit 140 is configured to determine the polar coordinates P(θ, r) of the measurement signal S polar by extracting the angular component θ and the radial component r therefrom, and to apply an inverse function of the function f (i.e., the inverse function f -1) to determine the absolute angle. -1

[0060] Once the absolute position calculation unit 140 has computed the absolute angle θ abs , the absolute linear position can be computed according to equation 1 :

[0061]

[0062] where p is the pole distance of the multi-pole bar magnet 150. The position output signal S pos has a value representing the computed absolute linear position.

[0063] The measured signal S polar can be modeled according to equation 2 using Euler's formula:

[0064]

[0065] where A represents the initial amplitude, d represents the damping coefficient, c represents the spiral offset value (complex number), φ0represents the initial phase, and i represents the imaginary number. The coefficients A, d, c, and φ0are model parameters that can be determined from the measurement points during End of Line (EOL) testing of the sensor system 200. The model parameters (A, d, φ0, c) of the spiral function Spiral(θ abs ) can be obtained using regression (curve fitting) on the measured data of the known absolute angle θ abs used as a reference by the sensor circuit 120 in EOL. After this calibration process, the final computed parameter values of the spiral model are stored in the sensor circuit 120.

[0066] The absolute angle θ abs is computed according to equations 3, 4, 5, and 6:

[0067] θ abs = θ m - θ0Equation (3),

[0068] θ m = ATAN2(V1, V2) Equation (4),

[0069] θ0= ATAN2(V10, V20) Equation (5),

[0070] r = sqrt(V1 2 + V2 2 ) Equation (6),

[0071] where θ m represents the measured polar coordinates P(θ​m , r) is the measured angle at the initial position, V10 is the value of V1 at the initial position, V20 is the value of V2 at the initial position, r is the measured radius of the polar coordinates P(0 m , r), and sqrt denotes the square root function. ATAN is the arctangent value of its two input values (e.g., ATAN2(V1 / V2)), also denoted as tan -1 .

[0072] Figure 5 is a flowchart of a method 500 for calculating the absolute linear position in run-time, according to one or more embodiments. The flowchart 500 is a computational flow implemented by the sensor circuit 120 (i.e., the converter 130 and the absolute position calculation unit 140).

[0073] The converter 130 receives the output signals V1 and V2 from the magnetic field sensor 110 and calculates the polar coordinates 0 m and r (operations 505 and 510) according to equations 4 and 6.

[0074] The absolute position calculation unit 140 receives the polar coordinates 0 m and r and generates the set of possible radii r set = {r0, r1, r2,.., r N} in operation 515 by looping equations 7 and 8 from n = 0, 1, 2,... N.

[0075] 0n = 2p n + (0 m - 0o) equation (7),

[0076] r n = ||Sprial(0 n )|| equation (8),

[0077] where N denotes the integer part of the maximum number of turns in the spiral trajectory. For example: if the spiral has 3 turns then N is 3, if the spiral has 4.5 turns then N is 4. This can be expressed as The mathematical notation refers to the floor(x) function in software languages. There are several function examples here: Therefore, N is a predefined integer determined by the system design. N can be calculated from where 0 a_max is the maximum absolute angle, which is equal to the maximum number of spiral turns * 360 degrees.

[0078] In operation 520, the absolute position calculation unit 140 calculates the absolute linear position L nDetermine the index k, where index k corresponds to one of the storage models for different spiral patterns. Radius r k It is the radius closest to the measured radius r among the storage models. Accordingly, the appropriate model is selected based on the measured radius r. Specifically, in operation 520, the absolute position calculation unit 140 determines the index k. The index k can be determined from r. set ={r0, r1, r2, ..., r N Select an element r from} n To obtain, where r n It is the value that is closest to the measured value of r. If r n If the value of r is chosen as the closest to the measurement, then k becomes n (k = n). For example, consider the following case:

[0079] ·N=3,

[0080] ·r set ={r0=2.3, r1=3.5, r2=4.7, r3=6.9} This is obtained from operation 515.

[0081] The measured value of r is 4.6.

[0082] If r = 4.6, then r set The element r that is closest to the measured value of r n If r² = 4.7, then k becomes 2. This means that the measured point P has 2 full circles + (θ) m -θ0) rotations. In other words, it takes two full rotations from the center of the spiral along the spiral path, plus an additional value (θ). m Only by -θ0) can we reach P.

[0083] Once according to r n Once index k is determined, the absolute angle θ can be calculated using formula 9 from absolute position calculation unit 140. abs (Operation 525).

[0084] θ abs =2πk+(θ) m -θ0) formula (9).

[0085] Once the absolute angle θ abs Once determined, the absolute position calculation unit 140 calculates the absolute linear position using Formula 1 (operation 530).

[0086] Figures 6A-6DAn absolute linear position system with an alternative magnetic sensor arrangement is illustrated in accordance with one or more embodiments. As the absolute linear position of the sensor 100 changes relative to the magnet, each magnetic sensor arrangement produces a linear change in the peak-to-peak amplitude of the magnetic field strength. For example, the field strength of the magnetic field produced by the magnet varies linearly along a linear trajectory (e.g., linear path 202). The magnet can be movably fixed, and the sensor 100 can be configured to change its position along the linear path 202. In this case, the produced magnetic field field strength is different at each position along the linear path 202 according to a linear variation, along with a sinusoidal variation. Alternatively, the sensor 100 can be movably fixed and the magnet can be configured to move along the central axis 201. In this case, the magnetic field field strength produced by the magnet at the position of the stationary sensor 100 varies linearly as the magnet moves along its linear trajectory.

[0087] Figure 6A A top view of an absolute linear position system 600A is shown that includes a sensor 100 and a multi-pole bar magnet 160 with a conical shape. Here, the central axis 201 of the magnet 160 and the linear path 202 are parallel to each other (i.e., the displacement angle is zero). However, due to the conical shape of the multi-pole bar magnet 160, the magnetic field strength varies linearly along the linear path, and the strength (peak-to-peak amplitude) is highest at the thickest portion of the magnet 160 (i.e., the left side), and the strength (peak-to-peak amplitude) is lowest at the thinnest portion of the magnet 160 (i.e., the right side). Thus, as the sensor 100 moves along the linear path 202, the measured magnetic field experiences a sinusoidal variation due to the alternating north and south poles and a linear variation in the peak-to-peak amplitude due to the conical shape of the magnet 160. The sensor 100 is configured to determine its absolute linear position along its linear path 202, or determine the absolute linear (minimum) distance d to the magnet 160, using any of the methods described above.

[0088] Figure 6B A side view of an absolute linear position system 600B is illustrated that includes a sensor 100 and a multi-pole bar magnet 150 that is tilted vertically relative to the sensor 100 in the XZ plane, rather than as in the previous embodiments in the XY plane. Figure 2 and Figure 3The magnetic field strength generated by the magnet 150 varies linearly along the linear path 202 due to the horizontal tilt in the XY plane. Accordingly, the vertical distance between the sensor 100 and the multipole bar magnet 150 varies along the linear path 202. The closer the sensor 100 is to the multipole bar magnet 150, the stronger the magnetic field. Thus, as the sensor 100 moves along the linear path 202, the measured magnetic field experiences a sinusoidal variation due to the alternating north and south poles and a linear variation in peak-to-peak amplitude due to the changing distance d of the magnet 150 from the linear path 202. The sensor 100 is configured to determine its absolute linear position along its linear path 202 or determine the absolute linear (minimum) distance d to the magnet 150 using any of the methods described above.

[0089] Figure 6C A side view of an absolute linear position system 600C including a sensor 100 and a multipole bar magnet 170 having a tapered shape is shown. The absolute linear position system 600C is similar to the absolute linear position system 600A shown Figure 6A except that the magnet 170 is vertically tapered instead of horizontally tapered. Thus, the magnetic field strength along the linear path 202 experiences a linear variation. As the sensor 100 moves along the linear path 202, the measured magnetic field experiences a sinusoidal variation due to the alternating north and south poles and a linear variation in peak-to-peak amplitude due to the tapered shape of the magnet 170. The sensor 100 is configured to determine its absolute linear position along its linear path 202 or determine the absolute linear (minimum) distance d to the magnet 170 using any of the methods described above.

[0090] Figure 6D A side view of an absolute linear position system 600D including a sensor 100 and a multipole bar magnet 180 having a magnetization gradient along its central axis 201 from one end of the magnet to the opposite end of the magnet is shown. Thus, the direction of the magnetization gradient is parallel to the linear path 202. For example, the magnetization can be strongest on the left side of the magnet 180 and weakest on the right side of the magnet 180, or vice versa. Thus, the magnetic field strength generated by the magnet varies linearly in peak-to-peak amplitude from its left side to its right side due to the magnetization gradient, or vice versa. As a result, the peak-to-peak amplitude of the magnetic field strength varies linearly along the linear path 202, despite the distance d between the sensor 100 and the magnet 180 can remain constant.

[0091] Thus, as the sensor 100 moves along the linear path 202, the measured magnetic field experiences a sinusoidal variation due to the alternating north and south poles and a linear variation due to the magnetization gradient. The sensor 100 is configured to determine its absolute linear position along its linear path 202 using any of the methods described above.

[0092] Although various embodiments have been described, it will be apparent to those of ordinary skill in the art that many more embodiments and implementations can be within the scope of the application. Therefore, the true scope of the application is not limited to the embodiments disclosed but is in accordance with the appended claims, together with the full scope of equivalents thereof. With respect to the various functions described above with regard to the components or structures (components, devices, circuits, systems, etc.) performing the various functions, unless otherwise specified, the terminology used to describe such components (including references to "means") is intended to be generic and to correspond to any component or structure that performs the particular function (i.e., functional equivalents) even if it is not structurally equivalent to the disclosed structure performing the function in the exemplary implementations of the application shown herein.

[0093] Furthermore, the appended claims are hereby incorporated into the description, wherein each claim can stand on its own as a separate example embodiment. While each claim can stand on its own as a separate example embodiment, it is noted that, although a dependent claim can refer in the claims to a specific combination with one or more other claims, other example embodiments can include the dependent claim in combination with each of the other dependent or independent claims. Such combinations are hereby expressly proposed in this disclosure in addition to what is explicitly stated above. Further, it is intended to include any additional claim that includes features of any other independent claim, even if this claim does not directly depend on the independent claim.

[0094] It should also be noted that the methods disclosed in the specification or claims can be implemented by a device having means for performing each of the actions of the methods.

[0095] Furthermore, it should be understood that the disclosure of a specific number of acts or functions in this specification or claims should not be construed as limiting the claims to a particular sequence of acts or functions, unless otherwise specified. Thus, acts or functions disclosed in one or more acts are not necessarily performed in the order in which they are disclosed. Further, it should be appreciated that, in some embodiments, a single act can include multiple sub-acts or be broken down into multiple sub-acts, and these sub-acts can be performed at different times or even in different orders. Unless expressly stated to the contrary, these sub-acts can be included in and form part of the disclosure of a single act.

Claims

1. An absolute position measurement system, comprising: a multipole magnet comprising alternating magnetic poles extending along a multipole extension direction, wherein the multipole magnet has a linearly varying configuration with respect to a linear path, and the multipole magnet is configured to generate a magnetic field along the linear path; and a magnetic sensor configured to move along the linear path, wherein the magnetic sensor comprises a first sensor element arrangement configured to generate a first sensor signal in response to the magnetic field, and a second sensor element arrangement configured to generate a second sensor signal in response to the magnetic field, wherein, as the magnetic sensor moves along the linear path, the first sensor signal has a first sinusoidal waveform having a first linearly varying peak-to-peak amplitude, and the second sensor signal has a second sinusoidal waveform having a second linearly varying peak-to-peak amplitude, wherein the second sinusoidal waveform is phase-shifted with respect to the first sinusoidal waveform, wherein the magnetic sensor further comprises a processing circuit configured to: receive the first sensor signal and the second sensor signal, compute polar coordinates based on the first sensor signal and the second sensor signal, generate a set of radii based on the polar coordinates, compute an absolute angle based on radii contained in the set of radii, and compute an absolute position of the magnetic sensor based on the absolute angle.

2. The absolute position measurement system of claim 1, wherein: the first sensor element arrangement comprises a first plurality of sensor elements sensitive to an in-plane magnetic field component of the magnetic field, and the second sensor element arrangement comprises a second plurality of sensor elements sensitive to the in-plane magnetic field component of the magnetic field.

3. The absolute position measurement system of claim 2, wherein the in-plane magnetic field component is aligned with the linear path.

4. The absolute position measurement system of claim 2, wherein: the first sensor element arrangement is a first sensor bridge circuit, the second sensor element arrangement is a second sensor bridge circuit, and the first sensor bridge circuit and the second sensor bridge circuit are arranged in a plane and are spaced apart along a sensor axis.

5. The absolute position measurement system of claim 1, wherein: the polar coordinates comprise an angle component and a radius component, and the polar coordinates are unique to the absolute position of the magnetic sensor.

6. The absolute position measurement system of claim 1, wherein: the processing circuit is configured to generate a polar coordinate signal based on the first sensor signal and the second sensor signal, wherein the polar coordinate signal is indicative of the absolute position of the magnetic sensor. as the magnetic sensor moves along the linear path, the polar coordinate signal has a spiral pattern, an amplitude of the spiral pattern varying based on the linearly varying configuration of the multipole magnet.

7. The absolute position measurement system of claim 6, wherein, ​ 8. The absolute position measurement system of claim 6, wherein, The polar coordinate signal comprises an angle component and a radius component in a polar coordinate space, and the processing circuitry is configured to determine the angle component and the radius component and to calculate an absolute position of the magnetic sensor based on the angle component and the radius component.

9. The absolute position measurement system of claim 1, wherein, The absolute position is an absolute linear position of the magnetic sensor along the linear path.

10. The absolute position measurement system of claim 1, wherein, The absolute position is an absolute distance of the magnetic sensor from the multipole magnet.

11. The absolute position measurement system of claim 1, wherein, The second sinusoidal waveform is phase-shifted by 90° with respect to the first sinusoidal waveform.

12. The absolute position measurement system of claim 1, wherein, The multipole extension direction intersects the linear path.

13. The absolute position measurement system of claim 1, wherein, The multipole magnet has a linear tapering with respect to the linear path.

14. The absolute position measurement system of claim 1, wherein, The multipole magnet has a linear magnetization gradient along the multipole extension direction such that the strength of the magnetic field varies linearly along the linear path according to the linear magnetization gradient.

15. An absolute position measurement system, comprising: a multipole magnet comprising alternating magnetic poles extending along a multipole extension direction, wherein the multipole magnet has a linearly varying configuration with respect to a linear path, and the multipole magnet is configured to generate a magnetic field along the linear path, the magnetic field having a strength that experiences a sinusoidal variation along the linear path due to the alternating magnetic poles and a linear variation along the linear path according to the linearly varying configuration with respect to the linear path; and a magnetic sensor configured to move along the linear path, wherein the magnetic sensor comprises a first sensor element arrangement configured to generate a first sensor signal and a second sensor element arrangement configured to generate a second sensor signal that is phase-shifted with respect to the first sensor signal, wherein the magnetic sensor further comprises processing circuitry configured to: receive the first sensor signal and the second sensor signal, compute polar coordinates based on the first sensor signal and the second sensor signal, generate a set of radii based on the polar coordinates, compute an absolute angle based on radii contained in the set of radii, and compute an absolute position of the magnetic sensor based on the absolute angle.

16. The absolute position measurement system of claim 15, wherein, The first sensor signal has a first sinusoidal waveform with a first linearly varying peak-to-peak amplitude, and the second sensor signal has a second sinusoidal waveform with a second linearly varying peak-to-peak amplitude, wherein the second sinusoidal waveform is phase-shifted with respect to the first sinusoidal waveform.

17. The absolute position measurement system of claim 15, wherein: the polar coordinates comprise an angle component and a radius component, and the polar coordinates are unique for the absolute position of the magnetic sensor.

18. The absolute position measurement system of claim 15, wherein, The absolute position is an absolute linear position of the magnetic sensor along the linear path.

19. The absolute position measurement system of claim 15, wherein, The absolute position is an absolute distance of the magnetic sensor from the multipole magnet.

20. An absolute position measurement system, comprising: A multipole magnet includes alternating magnetic poles extending along a multipole extension direction aligned with a linear path. The multipole magnet is configured to move along the linear path, wherein the multipole magnet has a linear configuration that changes relative to a fixed position as the multipole magnet moves along the linear path, and wherein the multipole magnet is configured to generate a magnetic field at the fixed position. A magnetic sensor that is movably fixed at the fixed position. The magnetic sensor includes a first sensor element arrangement and a second sensor element arrangement, the first sensor element arrangement being configured to generate a first sensor signal in response to the magnetic field, and the second sensor element arrangement being configured to generate a second sensor signal in response to the magnetic field. As the magnetic sensor moves along the linear path, the first sensor signal has a first sinusoidal waveform with a first linearly varying peak-to-peak amplitude, and the second sensor signal has a second sinusoidal waveform with a second linearly varying peak-to-peak amplitude, wherein the second sinusoidal waveform is phase-shifted relative to the first sinusoidal waveform. The magnetic sensor further includes a processing circuit, which is configured to: Receive the first sensor signal and the second sensor signal. Calculate polar coordinates based on the first sensor signal and the second sensor signal. Generate a set of radii based on the polar coordinates. The absolute angle is calculated based on the radii included in the set of radii, and The absolute position of the magnetic sensor is calculated based on the absolute angle.

21. A method for measuring the absolute position of a magnetic sensor, the method comprising: The first sensor element of the magnetic sensor is arranged to generate a first sensor signal in response to a magnetic field. The second sensor element of the magnetic sensor is arranged to generate a second sensor signal in response to the magnetic field. As the magnetic sensor moves along the linear path, the first sensor signal has a first sine wave with a first linearly varying peak-to-peak amplitude, and the second sensor signal has a second sine wave with a second linearly varying peak-to-peak amplitude, wherein the second sine wave is phase-shifted relative to the first sine wave. Calculate polar coordinates based on the first sensor signal and the second sensor signal. The radius is determined based on the polar coordinates. Calculate the absolute angle based on the radius; and The processing circuit calculates the absolute position of the magnetic sensor based on the absolute angle.

22. The method of claim 21, wherein the polar coordinates include angular and radial components, and the polar coordinates are unique for the absolute position of the magnetic sensor.

23. The method of claim 21, wherein: Calculating the absolute position of the magnetic sensor includes: generating a polar coordinate signal based on the first sensor signal and the second sensor signal, wherein the polar coordinate signal includes angular and radial components in polar coordinate space, and Computing the absolute position of the magnetic sensor further comprises determining the angular component and the radius component and computing the absolute position of the magnetic sensor based on the angular component and the radius component.

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