High-precision angle or linear contactless magnetic position sensor

Abstract

The present invention relates to an angular or linear contactless magnetic position sensor (C) comprising a permanent magnet (A) generating a nonlinearly varying magnetic field, and at least a first pair of probes associated with the permanent magnet (A), each probe being capable of measuring at least two magnetic field components at the same point. A processing circuit is connected to the first pair and configured to utilize at least some of the measurements provided by the first pair of probes to deliver a position signal representative of the absolute position of the permanent magnet (A).

Description

[Technical Field]

[0001] The present invention relates to the field of contactless magnetic and / or electromagnetic position sensors for precise measurement of absolute angular or linear position. Such sensors make it possible to detect angular position or linear displacement with a high accuracy of the order of 0.1% of the total stroke, or <0.5° for detections performed over a full revolution. Such systems are robust to disturbances and can be very accurate, and are used in particular in the automotive and robotics industries. [Background technology]

[0002] In the prior art, document EP 1 083 406 describes a rotation sensor consisting of a ring magnet and two magnetically sensitive sensing elements that measure the radial component of the magnetic field generated by the diametrically magnetized ring magnet. When positioned orthogonally, these two magnetically sensitive elements generate two sinusoidal signals, and by implementing the arctangent function (Atan) of these two signals, the angular position of the rotating magnet can be detected.

[0003] The drawback of this solution is its sensitivity to the placement of the magnetically sensitive sensing elements for calculating the exact angle value. This solution is also sensitive to any external magnetic field. In fact, any stray magnetic field having a component measurable by at least one of the two magnetically sensitive elements will induce significant nonlinearity errors.

[0004] Also known is the document US Patent No. 7,741,839, which presents the principle of a rotation sensor comprising a ring magnet and two magnetically sensitive sensing elements that measure two orthogonal components of the magnetic field generated by the ring magnet at the same point. These two elements generate two sinusoidal signals, and by implementing the Atan function of these two signals, the angular position of the rotating magnet can be detected.

[0005] The accuracy of the detected signal is not satisfactory and is limited by large variations in signal amplitude, leading to erroneous angular position calculations. This solution is also sensitive to any external magnetic fields.

[0006] Although the document US Patent No. 7,030,608 describes several configurations that achieve uniformity between the magnetic field components, the effect is generally very limited and requires a large footprint. Furthermore, the problem of sensitivity to external magnetic fields is not resolved, making this solution highly inadequate for many applications.

[0007] To improve accuracy, document FR 2 893 410 proposes applying a compensation factor (gain) to the ratio of the signals supplied by the magnetically sensitive sensing elements located at the same point, equal to the ratio of the maximum amplitudes of the orthogonal magnetic field components measured. This improves the nonlinearity of the signal, but the design remains limited to the case of a diametrically magnetized ring magnet.

[0008] Document EP 1989505 describes a linear or rotary transducer featuring a magnet whose magnetization is linearly variable. Again, by applying a proportionality factor (gain), it is possible to determine the linear or angular displacement of the magnet relative to the probe. However, even here, the accuracy is still insufficient, especially when the magnet's magnetization harmonics are large or when the magnet contains inhomogeneities.

[0009] Document FR 2965347 reports a case-by-case definition of gain values ​​through numerous tests or calculations to define gain values ​​different from the simple ratio of the maximum amplitudes of the components. This solution improves the measurement accuracy, but the setup (test bench, simulation) remains very complex and is limited to specific configurations.

[0010] A drawback of the latter solution is its sensitivity to external magnetic fields.

[0011] French Patent No. 2923903 describes an angle or linear sensor using two sets of orthogonally arranged probes with a magnet whose magnetization direction changes linearly with displacement. Each probe has a pair of magnetically sensitive sensing elements that measure orthogonal magnetic field components. By combining these different magnetic field components to obtain two signals of equal orthogonal intensity, it is possible to obtain an angle measurement that is insensitive to external magnetic fields under certain conditions. However, the sensor's angular accuracy remains moderate. The same principle applies to linear transducers.

[0012] WO 2009 / 101270 expands on the above principle by introducing third and fourth sets of magnetically sensitive sensing elements that are "carefully" offset from the first and second sets and positioned between them in the same way. By combining the signals from these four sets of magnetically sensitive sensing elements, it is possible to obtain angle measurements that are insensitive to external magnetic fields under certain conditions and improve the accuracy of the sensor (at least over a half mechanical rotation, i.e., 180°) by correcting magnetization errors associated with the magnet's geometry (particularly by compensating for magnetization harmonics). Given the number of elements involved (four separate probes), this solution remains highly sensitive to probe positioning errors and is still too inaccurate, with a nonlinearity of ±0.1% over a 180° angular range, i.e., an accuracy of ±0.18° over this angular range at best. This is still too inaccurate for certain automotive and robotic applications.

[0013] EP 2711663 describes a sensor with two tracks and at least two probes, which allows for very high angular accuracy by combining global detection from the first track with finer measurements from a second, multi-pole track. However, this solution requires high overall detection accuracy, possibly by using additional probes (four in total) on the sensor. The drawback of this solution is its high sensitivity to external magnetic fields and its susceptibility to errors in the positioning of the probes and the two magnetic tracks.

[0014] Also known in the prior art is document FR 3 118 804, which provides a simple angular or linear displacement measuring device using (at least) one magnetically sensitive sensing element capable of measuring at least two magnetic field components and a magnetized magnet with a magnetization profile comprising a combination of at least two periodic contributions that allows the simultaneous calculation of global position in a rotation (or multiple rotations) and more accurate local position and displacement values.

[0015] A drawback of some of the prior art solutions is their sensitivity to external magnetic fields.

[0016] While it is always possible to shield the transducer, this adds components, significantly increases manufacturing costs, and increases the overall size of the transducer.

[0017] [Object of the Invention] The present invention proposes to at least partially solve the above-mentioned problems by utilizing the principles disclosed in document FR 3 118 804. In particular, the invention facilitates the calculation of global and local positions. In particular, the invention makes it possible to easily achieve accurate angular (or linear) position measurements and can be configured to be insensitive to external magnetic fields. Summary of the Invention

[0018] To this end, the object of the present invention is to propose an angular or linear contactless magnetic position sensor. a permanent magnet generating a magnetic field that varies nonlinearly in the direction of movement, the variation comprising the combination of at least one first quasi-periodic signal, called "carrier signal", and at least one second quasi-periodic signal, called "carrier signal", in various magnetic field components, the first and second signals being different from each other; at least one first probe pair including a first primary probe and a first secondary probe, the first pair being associated with a permanent magnet, each probe capable of measuring at least two magnetic field components at a single point; and a processing circuit connected to the probe and configured to utilize at least a portion of the measurements provided by the probe to deliver a position signal representative of the absolute position of the permanent magnet.

[0019] According to the invention, the two probes of the first probe pair are positioned relative to each other such that a first quasi-periodic signal representative of global position and a second quasi-periodic signal representative of local position can be separated by differential combination of measurements of magnetic field components.

[0020] According to other advantageous, non-limiting features of the present invention, taken alone or in any technically feasible combination, the magnetic position sensor comprises a second probe pair comprising a second primary probe and a second secondary probe, the second probe pair being associated with a permanent magnet, each probe of the second probe pair being capable of measuring at least two magnetic field components at the same point, the two probe pairs being positioned relative to each other so as to obtain quadrature matching of signals obtained by differential coupling; the processing circuitry establishes: Measurement of the global position of the sensor by combining the magnetic field components according to the following formula: Atan2((Br1+Bt3)+(Br2+Bt4); Gain * ((Br3-Bt1)+(Br4-Bt2))) or Measurement of the local position of the sensor by combining the magnetic field components according to the following formula: Atan2((Br3-Bt1)-(Br4-Bt2); Gain* (Bz1-Bz2)) where Bri, Bti, and Bzi represent the radial, tangential, and axial magnetic fields measured by the probe with index i, respectively, and gain is a quantity selected to minimize the calculated angular error based on the sensor deflection. - the processing circuit establishes a measure of the local position of the sensor by combining the magnetic field components according to the following formula: Atan2((Bz3-Bt1)-(Bz4-Bt2); Gain * ((Bz1+Bt3)-(Bz2+Bt4))), where Bri, Bti, and Bzi represent the radial, tangential, and axial magnetic fields measured by the probe with index i, respectively, and gain is a quantity selected to minimize the angular error calculated with respect to the sensor deflection. the processing circuit establishes simultaneous global and / or local position measurements at different faces of the permanent magnet; The permanent magnet is a multi-pole magnet or magnet assembly, or an equivalent machined magnet. Advantageously, the permanent magnet consists of a set of current loops. the permanent magnet comprises all or part of the rotor of an electric motor, generator, actuator, gear reducer, coupler, gearbox, or oscillator; each probe comprises a plurality of magnetically sensitive elements selected from the list consisting of Hall probes, magnetoresistive elements, eddy current elements, and detection coils; The permanent magnet has the shape of a disk, a ring or a cylinder, and the probes of the at least one pair of probes are arranged around the magnet. the probes of at least one pair of probes are separated by a first angle value corresponding to a half period of the carrier signal; the probes of the first probe pair and the probes of the second probe pair are respectively separated from each other by a second angle value substantially equal to a quarter period of the carrier signal; the first angle value and / or the second angle value are adjustable; the processing circuitry is configured to correct the calculated angle value using an angle compensation factor; - The correction of the calculated angle value is based on trigonometric functions. The processing circuitry is configured to combine analog and digital detection of the magnetic field components.

[0021] According to another aspect, the present invention proposes to use the contactless magnetic position sensor defined above to measure additional values ​​on complex systems, including force, torque, acceleration, braking, phase shift, overall speed, direction of movement, distance, number of rotations, inertia, imbalance, vibration, noise, harmonic content, temperature, pressure, current, voltage, current, frequency, information encoding. [Brief explanation of the drawings]

[0022] Other features and advantages of the present invention will become apparent from the following detailed description of the invention which refers to the accompanying drawings. [Figure 1] 1 shows a rotary encoder structure constructed in accordance with the present invention; [Figure 2] 3 shows the evolution curves of the magnetic field components measured by the quasi-point probe of the sensor according to the invention; [Figure 3] 1 shows the evolution curves of the radial magnetic field components measured by a first pair of probes phase shifted by a first selected angle value, and the additive combination of these measurements. [Figure 4] 1 shows the evolution curves of the radial magnetic field components measured by two pairs of probes arranged relative to each other in a configuration according to the invention in order to calculate the global angular position. [Figure 5] 1 shows the evolution curve of the global angle value obtained by combining the radial components measured by four probes arranged relative to each other in a configuration according to the invention. [Figure 6] 1A and 1B show the combination of the tangential and axial components of the magnetic field obtained by combining measurements provided by four probes arranged relative to each other in a configuration according to the invention. [Figure 7]1A and 1B show the combination of the tangential and axial components of the magnetic field obtained by combining measurements provided by four probes arranged relative to each other in a configuration according to the invention. [Figure 8] 1 shows the evolution curves of the radial magnetic field components measured by two pairs of probes arranged relative to each other in a configuration according to the invention in order to calculate the local angular position. [Figure 9] 1 shows the evolution curve of local angle values ​​obtained by combining the radial components measured by four probes arranged relative to each other in a configuration according to the invention. [Figure 10] 1 shows the evolution curves of magnetic field components measured by two pairs of probes arranged relative to each other in a configuration according to the invention, the measurements being combined together to make the calculation of global angular position less sensitive to external magnetic fields. [Figure 11] 11 shows the results of an angular position calculation provided by a sensor according to the invention implementing the coupling of FIG. 10 . [Figure 12] 1 shows the evolution curves of magnetic field components measured by two pairs of probes arranged relative to each other in a configuration according to the invention, the measurements being combined together to make the calculation of local angular position less sensitive to external magnetic fields. [Figure 13] 13 shows the results of an angular position calculation provided by a sensor according to the invention implementing the coupling of FIG. 12. [Figure 14] 13 shows the evolution curves of magnetic field components measured by two pairs of probes arranged relative to each other in a configuration according to the invention, the measurements being combined together according to an alternative combination to that shown in FIG. 12. [Figure 15] 15 shows the results of an angular position calculation provided by a sensor according to the invention implementing the coupling of FIG. 14. [Figure 16a] 1 shows the effect of an external magnetic field on the angular error. [Figure 16b] 1 shows the effect of an external magnetic field on the angular error. [Figure 17a] 1 shows the effect of an external magnetic field on the angular error. [Figure 17b]1 shows the effect of an external magnetic field on the angular error. [Figure 18a] 1 shows the effect of an external magnetic field on the angular error. [Figure 18b] 1 shows the effect of an external magnetic field on the angular error. [Figure 19] 1 shows a sensor C according to the invention in a linear configuration. [Figure 20] 10 shows the results of angular position calculations provided by a sensor according to the invention operating in degraded mode with only one pair of probes. [Figure 21] 10 shows the results of angular position calculations provided by a sensor according to the invention operating in degraded mode with only one pair of probes. [Figure 22] FIG. 22 shows another rotary encoder structure of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0023] Figure 1 shows the structure of a magnetic position sensor C in one embodiment. The magnetic flux generated by a disk-shaped permanent magnet A is collected around it by at least four sets of sensing elements 1-4 (or magnetic sensors) positioned radially or axially without contacting the magnet. The permanent magnets can have any shape other than the disk shape of magnet A shown in Figure 1, in particular a ring or cylindrical shape.

[0024] Each set of sensing elements measures at least two components of magnetic induction at the same point, if necessary, via a magnetic flux collector defining an air gap in which the sensing elements 1-4 are located. The magnetically sensitive elements can include, for example, Hall probes, magnetoresistive elements, eddy current elements, and detection coils. As is well known, each set of magnetically sensitive elements can be integrated into a housing to form a magnetic probe capable of detecting two or three magnetic field components. For simplicity, in the remainder of this description, "probe" refers to a set of magnetically sensitive elements capable of detecting two or three magnetic field components at almost any given moment. However, this designation in no way limits the implementation of the principles of the present invention, which can include arranging several sets of magnetically sensitive elements in the same housing to detect magnetic field components at multiple points.

[0025] Thus, the magnetic position sensor C shown in FIG. 1 has four probes 1-4, including a first primary probe 1 and a second primary probe 2 on the one hand, and a first secondary probe 3 and a second secondary probe 4 on the other hand. The first primary probe 1 and the first secondary probe 2 form a first probe pair 1, 2 that are angularly out of phase with each other by a first separation angle θ. The second primary probe 3 and the second secondary probe 4 form a second probe pair 3, 4 that are angularly out of phase with each other by the first separation angle θ. The first probe pair 1, 2 and the second probe pair 3, 4 are angularly out of phase with each other by a second separation angle β.

[0026] In the next section of this description we will look at the advantages of such an arrangement.

[0027] The permanent magnet A may be a multi-pole magnet or magnet assembly, or an equivalent machined magnet. This magnet may comprise all or part of the rotor of an electric motor, generator, actuator, gear reducer, coupler, gearbox, or oscillator. Advantageously, the permanent magnet comprises a set of current loops.

[0028] The sensor also comprises a processing circuit connected to the probes 1 to 4 and configured to output a position signal that depends on the absolute position (deflection) of the permanent magnet A.

[0029] The magnetic position sensor C according to the invention has a magnetization profile according to the teachings of document FR 3 118 804 cited in the introduction of this application. This profile is complex and results in multi-periodic variations in the magnetization profile (or its orientation relative to an axis or reference point) depending on the relative trajectory of the measurement air gap and the magnet. The permanent magnet A generates a magnetic field that varies nonlinearly along the direction of movement, the variations exhibiting a form corresponding to the combination of at least two different quasi-periodic contributions.

[0030] This magnetization profile can be presented in a first so-called "carrier" pattern containing P measurement increments with a period p. It contains N increments with a period p. * It is also possible to include a second so-called "carrier" pattern with n (real number n>0, constant or variable). This double pattern allows combining a coarse detection (global output of the sensor) with a finer detection of the absolute position (local output of the sensor). The measurement increments are constituted, for example, by measuring the magnetic poles. Thus, two poles of opposite polarity can constitute a given period of the period. It is also possible to provide at least one magnetic anomaly resulting in an atypical magnetic flux in the magnetization profile, which serves as a "revolution counting" indicator, making it possible to count the number of revolutions or events that have been performed beyond the first excursion. This output signal includes a predetermined number T of measurement increments over the measurement interval.

[0031] 2 shows three magnetic field components (radial component Br, tangential component Bt, and axial component Bz) from one of probes 1-4 for a magnetization profile having N=2 increments on the carrier signal and P=48 increments on the carried signal for an angular stroke of 360° (one full rotation). The number T of magnetic anomalies, used as a "revolution count" indicator to aid in counting the number of rotations, is set to zero so as not to unnecessarily complicate the description of the present invention.

[0032] Note that there is always (at least) a first angle value (called θ) separating the two probes, which allows the generation of a sine wave with a period representing the carrier signal by carefully combining measurements made by two probes from the same probe pair. This first angle value θ corresponds approximately to half a period of the carried signal. Figure 3 shows the results of the radial magnetic field measurements Br1 and Br2 provided by the first primary probe 1 and the first secondary probe 2, respectively, for a first separation angle value θ of approximately 7.5° (P=48 in this configuration) for the first primary probe 1 and the first secondary probe 2, as well as the sum of these two signals Br1+Br2.

[0033] By carefully combining measurements made by a second primary probe 3 and a second secondary probe 4 that are phase shifted by the same first angle value θ, it can be seen that there is always (at least) a second angle value (denoted β) separating the first primary probe 1 and the first secondary probe 2 from the second primary probe 3 and the second secondary probe 4, respectively, and that combining the measurements of the magnetic field components produced by these probes 3, 4 makes it possible to generate a second sine wave, orthogonal to the sine wave obtained from the first pair of probes 1, 2, and having a period representing the carrier signal. This second angle value β corresponds approximately to one-quarter period of the carrier signal.

[0034] Figure 4 shows the results of the radial magnetic field measurements Br3, Br4 provided by the probes of the second probe pair 3, 4 respectively, as well as the sum Br3+Br4 of these two measurements, for a second separation angle value β of the order of 90° (N=2 in this configuration).

[0035] Figure 5 shows the results of the angular position calculation provided by sensor C having the configuration described in this invention, which yields the result shown in Figure 4. This calculation uses the arctangent of two orthogonal sinusoids from the measured radial component Brad, combined by addition. The angular error of the calculated global position is + / - 5° over one revolution.

[0036] The same strategy can be advantageously applied to the tangential Bt and axial Bz components of the magnetic field, as shown in Figures 6 and 7, respectively. The tangential Bt and axial Bz components are combined into pairs by addition. This allows for three sets of curves with similar magnitudes in the pairs, allowing for accurate calculation of the overall angle value.

[0037] To calculate local position, the same approach can be used, this time combining the magnetic field components to enhance the carrier signal, by subtracting two by two the components supplied by the same pair of probes, as shown in Figure 8.

[0038] Thus, Figure 9 shows the results of the angular position calculation provided by sensor C having the configuration described in this invention, which yields the results shown in Figure 8. This calculation uses the arctangent of two orthogonal sinusoids from the radial component Brad. The angular error of the calculated local position is + / - 3.5° over a fraction of a revolution (one pair increment of the carried signal, i.e., approximately 15° of mechanical angle in the exemplary configuration). The angular accuracy of the mechanical angle measurement is therefore 3.5 / 24 pair increments (P = 48), i.e., + / - 0.15°.

[0039] The same strategy can be advantageously applied to the tangential component Bt and the axial component Bz. Three sets of curves (not shown) with similar magnitudes in pairs can be obtained, allowing for accurate calculation of local angle values.

[0040] This very general approach makes it easy to see the advantage of differential processing of at least one of the measured magnetic field components. "Differential processing or combination" is understood to mean the combination, by difference or addition, of the magnetic field components from at least some of the probes 1 to 4 of the sensor C. This makes it possible to emphasize the carrier signals for calculating the global angle (position in rotation) and the carrier signals for calculating the local angle (position in the increment under consideration) by elementary calculations.

[0041] The simultaneous calculation of both angle values ​​guarantees instantaneous and absolute knowledge of the exact angular (or linear) position without requiring a minimum deviation to complete the initial calculation.

[0042] The use of component ratios utilized in the tangent arc calculation ensures that the angle calculation is essentially insensitive to temperature changes: since the components are affected in the same way, the ratios do not change.

[0043] However, conventionally used magnetic field components remain sensitive to external magnetic fields. To compensate for this phenomenon, the signal provided by the probe can be combined to incorporate external field compensation, so that the detection is insensitive to stray external magnetic fields.

[0044] Referring to FIG. 1, the following can be seen: The first secondary probe 2, positioned along the first axis x, measures the radial magnetic field Br2 of the magnet plus the projection Hx of the external magnetic field Hext along the first axis x, i.e., Br2 + Hx. Similarly, the second secondary probe 4, positioned along the second axis y, perpendicular to the axis x, measures the tangential magnetic field Bt4 of the magnet 4 minus the projection Hx of the external magnetic field Hext along the first axis x, i.e., Bt4 - Hx. The sum of these two measurements (Br2 + Hx) + (Bt4 - Hx) is therefore independent of the component Hx of the external magnetic field along the first axis x. The same observation can be made by selecting other pairs of probes in quadrature 1, 3. - The first secondary probe 2, positioned along the first axis x, measures the tangential magnetic field Bt2+Hy of the magnet to which the projection Hy of the external magnetic field Hext along the second axis y is added. Similarly, the second secondary probe 4, positioned along the second axis y, measures the radial magnetic field Br4 of the magnet 4, Br4+Hy, to which the projection Hy of the external magnetic field Hext along the second axis y is also added. Therefore, the difference between these two measurements (Bt2+Hy)-(Br4+Hy) is not affected by this component Hy of the external magnetic field Hext along the second axis y. The same observation can be made by selecting other pairs of probes in quadrature 1, 3. Finally, the first secondary probe 2, positioned along the first axis x, measures the axial magnetic field Bz2+Hz of the magnet, to which is added the projection Hz of the external magnetic field Hext along the third axis z (which together with the first and second axes x, y form a trihedron). Similarly, the second secondary probe 4, positioned along the second axis y, measures Bz4+Hz, i.e. the axial magnetic field Bz4 of the magnet 4, to which is also added the projection Hz of the external magnetic field Hext along the axis z. The difference between these two measurements (Bz2+Hz)-(Bz4+Hz) is therefore not affected by this component Hz of the external magnetic field Hext along the third axis z.

[0045] This explanation is based on the assumption that the external magnetic field impinges uniformly on all four probes. In reality, the small but unavoidable distances between the probes result in small variations without significantly affecting the final angular accuracy.

[0046] By combining the magnetic field components according to the formula (the expression is simplified): Br1 + Bt3 and Br2 + Bt4, as well as their addition; Br3-Bt1 and Br4-Bt2, as well as their addition;

[0047] As shown in Figure 10, it is possible to obtain a robust detection of the external magnetic field for global angular position calculation.

[0048] Figure 11 shows the result of the angular position calculation provided by sensor C, which implements the above combination. This calculation uses the arctangent (or Atan2 function) of the ratio of two curves of equal intensity. ·Atan2((Br1+Bt3)+(Br2+Bt4); Gain * ((Br3-Bt1)+(Br4-Bt2))) The gain value is adjusted to minimize the calculated angular error for the sensor deflection (here 0.998).

[0049] Angles measured on a full machine lathe give angular position values ​​of + / - 5° (Figure 11).

[0050] Advantageously, by combining the magnetic field components according to the formula (shown in FIG. 12): Br3-Bt1 and Br4-Bt2, and their subtraction ·Bz1-Bz2; It is possible to obtain a robust detection of the external magnetic field for local angular position calculation.

[0051] The value of the local angular position is calculated using the arctangent (or Atan2 function) of the ratio of two curves of equal intensity. ·Atan2((Br3-Bt1)-(Br4-Bt2); Gain * (Bz1-Bz2)) The gain value is adjusted to minimize the calculated angular error relative to the sensor deflection (here 0.933).

[0052] The angle calculated over one period (one pair of increments) of the carried signal gives a local angular position value of + / - 5° (electrical), as shown in Figure 13. For mechanical angles, the measured angular accuracy is 5 / 24 = + / - 0.21° mechanical over a full rotation, and the angular error measured for each pair of increments over the rotation remains very similar.

[0053] According to the particular embodiment shown in FIG. 14, the coupling of the magnetic field components follows the formula: Subtraction of Bz1+Bt3 and Bz2+Bt4, Bz3-Bt1, Bz4-Bt2, and their subtraction,

[0054] It is possible to obtain a second detection for calculating the local angular position, generally with improved accuracy.

[0055] The value of the local angular position is calculated using the arctangent (or Atan2) of the ratio of two curves of equal intensity. ·atan2((Bz3-Bt1)-(Bz4-Bt2);Gain * ((Bz1+Bt3)-(Bz2+Bt4))) The gain value is adjusted to minimize the calculated angular error for the sensor deflection (here 0.995).

[0056] The angle calculated over one period (one pair of increments) of the carried signal gives a local angular position value of + / - 3° (electrical) as shown in Figure 15. For mechanical angles, the measured angular accuracy is 3 / 24 = + / - 0.125° mechanical over a full rotation, and the angular error measured for each pair of increments over the rotation remains very similar.

[0057] 16a and 16b show the effect of an external magnetic field Hext (measured with one probe alone: ​​Bx=10 mT, By=-3 mT, and Bz=7 mT; uniform across all probes) on the measured magnetic field components without (FIG. 16a) and with (FIG. 16b) an external magnetic field Hext. 16a and 16b show the effect of an external magnetic field Hext (measured with one probe alone: ​​Bx=10 mT, By=-3 mT, and Bz=7 mT; uniform across all probes) on the measured magnetic field components without (FIG. 16a) and with (FIG. 16b) an external magnetic field Hext.

[0058] Figures 17a, 17b and 18a, 18b compare the calculated angular errors in the two cases. - In Figure 17, in the presence of an external magnetic field Hext, (a) the global angular position and (b) the local position measured for one increment. In FIG. 18, in the absence of an external magnetic field Hext, (a) for the global angular position and (b) for the local position measured for one increment.

[0059] As expected, the signal does not change. Other tested field strengths confirm these measurements.

[0060] Those skilled in the art will easily understand the difference between the present invention and the solution proposed by prior art WO 2009 / 101270 for calculating the angular stroke, which is performed by radial detection on a diametrically magnetized ring for a magnetic field that varies linearly with angular position. In sensor C according to the present invention, the magnetic field measured by the magnetically sensitive element does not vary linearly with angular position. This is particularly clear in FIG. 10. Therefore, the two approaches cannot be confused.

[0061] A sensor C according to this specification may include signal processing circuitry for combining the components to determine instantaneous global and local angle values, which may also perform various compensations required to correct these angle values.

[0062] To reduce computation time, the device can combine analog and digital detection of the magnetic field components.

[0063] According to a particular embodiment, the sensor C further comprises means for storing the angle values ​​and linearity coefficients used to compensate for the linearity of the sensor, these storage resources being accessible to the signal processing circuitry, which can use them to apply a process to compensate for the linearity of the sensor.

[0064] According to a particular embodiment, the sensor further comprises means for determining an opposing increment or pair of increments based on the overall angular position, said increment or pair of increments being called "active".

[0065] Each active increment is associated with (for example) a sequence number or a global angular position (identified, for example, by a zero crossing of one of the magnetic field components or a combination of the components). This method ensures, in a simple and accurate way, that the read increment corresponds to the calculated global value without the risk of errors with neighboring increments.

[0066] Each local angle value calculated at an active increment can be used as a local angle value or a full-scale percentage, or directly as a global angle value (by dividing the read value by the number of increment pairs (here 24) and then adding it to the global angle position associated with the active increment pair). For example, 183.4° calculated at an increment corresponding to a global position (zero crossing) of 157.3° immediately gives an angular position of 157.30 + 183.4 / 24 = 164.94°.

[0067] Since each increment may contain magnetization anomalies, the exact angle value of each increment can be used to respect the true angle value read on the magnetic track. Thus, for a pair of increments of 15.7° (not 15° as theoretically expected), 157.30 + 183.4 / (360 / 15.7) = 165.29°.

[0068] According to a particular embodiment, an angle compensation factor is calculated for each increment (i) according to Increment Factor (i) = Theoretical Increment Angle Value / Measured Increment Value, and this factor is used to correct local and / or global angle values.

[0069] According to certain embodiments, the magnetic field component detection mode can be axial or radial, or a combination thereof.

[0070] In certain embodiments, the magnetic field component detection modes can be performed simultaneously for different sides of the magnetic target.

[0071] According to certain embodiments, the sensor further comprises self-calibration means that allow certain calculated values ​​to be adjusted during the life of the sensor in order to maintain an optimum performance level.

[0072] According to a particular embodiment, the sensor further comprises diagnostic means making it possible to signal possible faults (probe, magnetic sensitive element, magnetic track, communication, calculation, temperature, external magnetic field, sensor stroke, speed, etc.) and to activate possible degradation modes, making it possible for the sensor to operate with reduced performance, in particular degradation modes that allow detection using a minimum number of magnetic sensitive elements.

[0073] Figure 20 gives a good indication of global position calculations using only signals from 2θ-shifted probes (e.g., first probe pair 1, 2 or second probe pair 3, 4 - left graph). Global position (right graph) is obtained by Atan(Bz / Btan) or Asin(Brad) calculations, where Brad, Btan, and Brz correspond to the sum of the radial, tangential, and axial magnetic field components provided by each of the two probes, respectively. Calculated linearity is + / - 6° over a full mechanical rotation.

[0074] Figure 21 gives a good indication of the local position calculation using only the signals from the two probes phase-shifted by a first angle value θ. The local position is obtained by an Atan(Bz / Btan) or Asin(Brad) calculation, where Brad, Btan, and Brz correspond to the difference between the radial, tangential, and axial magnetic field components provided by each of the two probes, respectively (Figure 21). The calculated linearity is + / - 3° over a pair of increments, i.e., + / - 0.125° or one full mechanical rotation.

[0075] Other combinations of magnetic field components for separating global and / or local angular positions can be selected to implement effective detection modes according to the expected operating conditions.

[0076] In particular, as shown in Figure 22 a first probe pair 1, 2 phase-shifted by a first angle value θ corresponding to half a period of the carrier signal, which can be used to determine the local position; a second probe pair 3, 4, phase shifted by an angle value corresponding to one signal period, which can be used to determine the global position;

[0077] In this case, the first and second probe pairs can be separated by an arbitrary second angle value (β), for example, chosen to be zero.

[0078] The method for determining the precise angular position according to the calculated angle measurements involves first calculating the global and local positions. In a second step, compensation values ​​for these angular positions can be defined. Finally, detection diagnostics can be performed to verify the measurements and, if necessary, initiate a degradation detection mode. From the calculated angle values, values ​​for the rotation speed and direction are determined.

[0079] According to certain embodiments, a mathematical function (such as a polynomial) can be used to compensate the angle value (or linear deviation) calculation, with each increment being associated with a set of coefficients (six coefficients for a polynomial of degree 5) required to define this function and the combination of the function.

[0080] According to certain embodiments, trigonometric functions (or their equivalents) can be used to compensate the angular value (or linear deviation) calculations. Each increment would be associated with a set of coefficients required to define that function (e.g., intensity, period, angular offset) and combination of functions.

[0081] According to certain embodiments, the sensor can use only a very small number of magnetically sensitive elements capable of measuring one or more magnetic field components or any combination in order to meet space or cost requirements. This solution can also be envisaged for detection over a very limited stroke (less than 360° in the case of a rotation sensor).

[0082] In another variant, the measurement device can include several probes, each positioned at a specific point, allowing for a double or triple operation mode. By averaging all the values ​​obtained by all these probes, it is possible to obtain an average angle value that reduces the uncertainty associated with a single probe set (for example, a set of four probes capable of measuring one or more magnetic field components). Thus, for example, the use of five, six, seven, or eight probes can be envisaged to create a fully redundant sensor for applications requiring maximum completeness and reliability (ASILD type for automotive applications). This can also be used to enrich the coupling of different magnetic field components.

[0083] Naturally, the invention is not limited to the described embodiments, and variant embodiments can be added thereto without departing from the scope of the invention as defined by the claims.

[0084] In this way, the sensor C can have a linear configuration as shown in Figure 19. This linear configuration can be obtained by mentally expanding the solutions obtained for axial or radial angle detection. Since the magnetic field profiles of the various magnetic field components are similar, the process remains the same, taking care to correctly position (linearly space) the sets of magnetically sensitive elements in order to obtain valid first and second angle values ​​β and θ for the differential analysis.

[0085] Regardless of whether the sensor C is linear or disk-shaped, the set of magnetically sensitive elements can be repositioned relative to the permanent magnet, thereby adjusting the first angle value θ and / or the second angle value β.

[0086] Sensors can be used to measure quantities in complex systems in addition to angular or linear displacement, which may correspond to force, torque, acceleration, braking, phase shift, overall velocity, direction of movement, distance, rotational speed, inertia, imbalance, vibration, noise, harmonic content, temperature, pressure, current, voltage, current, frequency, and information encoding.

Claims

1. A non-contact angular or linear magnetic position sensor (C), a permanent magnet (A) generating a magnetic field that varies nonlinearly in the direction of movement, said variation comprising the combination of at least one first quasi-periodic signal, called "carrier signal", and at least one second quasi-periodic signal, called "carrier signal", in the various magnetic field components, said first and second signals being different from each other; at least one first pair of probes (1, 2; 3, 4) comprising a first primary probe (1) and a first secondary probe (2; 4), said first pair being associated with said permanent magnet (A), each probe being capable of measuring at least two magnetic field components at a single point; and a processing circuit connected to said probe and configured to utilize at least some of the measurements provided by said probe to deliver a position signal representative of said absolute position of said permanent magnet (A); a contactless angular or linear magnetic position sensor (C) characterized in that the two probes of the first probe pair (1, 2) are separated by a first angle value (θ) corresponding to half a period of a carrier signal, allowing a first quasi-periodic signal representative of a global position and a second quasi-periodic signal representative of a local position to be separated by differential combination of magnetic field component measurements.

2. 2. The magnetic position sensor (C) of claim 1, comprising a second probe pair (3, 4) comprising a second main probe (3) and a second secondary probe (4) separated by an angle value corresponding to the period of the carrier signal.

3. 2. The magnetic position sensor (C) of claim 1, further comprising a second probe pair (3, 4) comprising a second primary probe (3) and a second secondary probe (4), the second probe pair (3, 4) being associated with the permanent magnet (A), each probe of the second probe pair (3, 4) being capable of measuring at least two magnetic field components at the same point, the two probe pairs (1, 2; 3, 4) being positioned relative to each other to obtain quadrature matching obtained from the signals by differential coupling.

4. 4. The non-contact magnetic position sensor (C) of claim 3, wherein the probes of the first probe pair (1, 2) and the probes of the second probe pair (3, 4) are respectively separated from each other by a second angular value (β) substantially equal to a quarter period of a carrier signal.

5. 5. The contactless magnetic position sensor (C) according to claim 4, wherein the first angle value (θ) and / or the second angle value (β) are adjustable.

6. The processing circuitry establishes: Measurement of the global position of the sensor by combining the magnetic field components according to the following formula: Atan2((Br1+Bt3)+(Br2+Bt4); Gain ＊ ((Br3-Bt1)+(Br4-Bt2))) or Measurement of the local position of the sensor by combining the magnetic field components according to the following formula: Atan2((Br3-Bt1)-(Br4-Bt2); Gain ＊ (Bz1-Bz2)) where Bri, Bti, and Bzi represent the radial, tangential, and axial magnetic fields measured by the probe with index i, respectively, and the gain is an amount selected to minimize an angular error calculated based on the deflection of the sensor.

7. The processing circuitry establishes a measure of the local position of the sensor by combining the magnetic field components according to the following equation: Atan2((Bz3-Bt1)-(Bz4-Bt2); gain ＊ ((Bz1+Bt3)-(Bz2+Bt4))), where Bri, Bti, and Bzi represent the radial, tangential, and axial magnetic fields measured by the probe with index i, respectively, and the gain is an amount selected to minimize the angular error calculated with respect to the deflection of the sensor.

8. A contactless magnetic position sensor (C) according to any one of claims 1 to 7, wherein said permanent magnet (A) is a multi-pole magnet or magnet assembly or an equivalent machined magnet.

9. A contactless magnetic position sensor (C) according to any one of claims 1 to 7, wherein the permanent magnet (A) consists of a set of current loops.

10. The non-contact magnetic position sensor (C) according to any one of claims 1 to 9, wherein the permanent magnet (A) comprises all or part of a rotor of an electric motor, generator, actuator, gear reducer, coupler, gearbox or oscillator.

11. A contactless magnetic position sensor (C) according to any one of claims 1 to 10, wherein each probe (1, 2; 3, 4) comprises a plurality of magnetically sensitive elements selected from the list consisting of Hall probes, magnetoresistive elements, eddy current elements and detection coils.

12. The non-contact magnetic position sensor (C) according to any one of claims 1 to 11, wherein the permanent magnet (A) has the shape of a disk, a ring or a cylinder, and the probes of at least one pair of probes (1, 2; 3, 4) are arranged around the magnet.

13. The contactless magnetic position sensor (C) according to any one of claims 1 to 12, wherein the processing circuitry is configured to correct the calculated angle value using an angle compensation factor.

14. 14. The contactless magnetic position sensor (C) of claim 13, wherein the correction of the calculated angle value is based on a trigonometric function.

15. 15. A contactless magnetic position sensor (C) according to claim 13 or 14, wherein the processing circuitry is configured to combine analog and digital detection of the magnetic field components.

16. Use of a contactless magnetic position sensor (C) according to any one of claims 1 to 15 for measuring additional values ​​on complex systems, including force, torque, acceleration, braking, phase shift, overall speed, direction of movement, distance, number of rotations, inertia, imbalance, vibration, noise, harmonic content, temperature, pressure, current, voltage, current, frequency, information encoding.

Images