Non-contact position sensor equipped with a permanent magnet, measuring device, and method of applying the non-contact position sensor.

Abstract

The invention relates to a contactless position sensor comprising a permanent magnet generating a magnetic field and at least one element (or magnetically sensitive element) for detecting the magnetic field in at least two directions, the permanent magnet being movable in the direction of movement and having a magnetization that is continuously variable in the direction of movement, the variation in magnetization having a shape that corresponds to a combination of at least two different quasi-periodic contributions along different field components, the sensor further comprising a computer for combining the values ​​of these field components and for determining a precise value of the position.

Description

[Technical Field]

[0001] The present invention relates to the field of non-contact magnetic and / or electromagnetic position sensors for precise measurement of absolute angular position or absolute linear position. Such sensors enable the detection of angular position or linear displacement with high accuracy of about 0.1% of the total stroke or <0.5° for detection performed with a full rotation.

[0002] Prior art has provided known devices for measuring the magnetic field of a reference point's angular (or linear) position, which are angularly (or linearly) movable around an axis relative to a fixed point. Such measuring devices typically include a rotating magnetic element (or magnetoresistive (MR) element) and a magnetosensitive (MS) element for calculating the angular position of the magnetic element relative to the reference point, and for measuring the magnetic flux or the axial and / or radial components of this magnetic flux (or field).

[0003] The first sensor solution, a "360° Hall effect sensor" type or "sine wave sensor-cosine sensor" sensor, uses a single probe to measure at least two components of the magnetic field, or uses a magnetic circuit that generates a proportional change in magnetic flux during deflection motion. The accuracy of such measuring devices is limited (typically ≥1° mechanical angle) and may be considered insufficient for certain applications (e.g., robotics).

[0004] While sensors of the same type using at least two Hall effect probes can improve the accuracy of such measuring devices, particularly through the configuration of different field components, they still remain close to a 0.5° mechanical angle and may still be considered insufficient for certain applications (e.g., machine tools).

[0005] Another family of ferromagnetic sensors with a coiled stator, commonly called resolvers (e.g., reluctance resolvers), uses a system of transmitter and receiver magnetic coils distributed across the stator. While the accuracy of these resolvers is crucial, these sensors are described as bulky, expensive, and complex to assemble at application. They are widely used in industrial (e.g., machine tools) and automotive sectors (power steering, transmissions), but remain limited to a few high-range applications.

[0006] The third family of sensors deploys several magnetic tracks (each carrying a given magnetization profile or magnetic flux) and is generally indexed among them.

[0007] "Nonius" or "Vernier effect" type sensors, which have a different number of magnetic pole pairs on two tracks and generate a phase shift in the magnetic signal used to determine the angular (or linear) position, are part of this third family.

[0008] It is also known that in this family, multi-pole "encoder" type sensors capable of creating combined digital signals can enable the determination of relative or absolute angular position, or that sensors combining a "360° Hall effect sensor" and an "encoder" type digital sensor can enable the combination of coarse analog measurements over a full rotation with numerous digital signals, and that these measurements can be locally refined through a dedicated algorithm, enabling the calculation of accurate angular values.

[0009] These sensors (or encoders) are extremely precise (<0.5°) and smaller than resolvers, but require at least two magnetic tracks (or EMCs) and at least one magnetic probe (or EMS) per track. These sensors are described as more expensive and complex to assemble than sensors with only a single EMC. Their use is generally limited to high-precision positioning technologies found in satellites, machine tools, assembly robots, and medical robots. [Background technology]

[0010] Patent Document 1 describes a process for parameterizing an absolute position measurement system that includes a permanent magnet, at least one probe that moves relative to the magnet over a predetermined travel distance, and a calculation unit that supplies position information calculated as a function of the arctangent of the ratio of correction coefficients G between probe output signals (these signals are pseudo-sine waves and are orthogonal signals). This process includes an optimization operation consisting of selecting a value for the coefficient G that minimizes the error in the measurement system caused by the pseudo-sine wave nature of the output signals from the probes.

[0011] Also, Patent Document 2 The report also describes an angular or linear magnetic position sensor comprising a movable element consisting of at least one magnet having a magnetization direction that changes linearly along the direction of movement of the magnet within a surface defined by the direction of movement and normal direction, at least four magnetic sensing elements, and at least one processing circuit that delivers a signal according to the absolute position of the movable element, wherein the first set of magnetic sensing elements consists of a pair of magnetic sensing elements located at the same point, spatially offset from the second set of magnetic sensing elements, and the magnetic sensing elements of the first and second sets of magnetic sensing elements consist of a pair of magnetic sensing elements located at the same point in the direction of movement of the magnet. The magnetic sensing elements of the first and second sets of magnetic sensing elements are capable of measuring the tangential component of the magnetic field, and the magnetic sensing elements of the first and second sets of magnetic sensing elements are capable of measuring the normal component of the magnetic field. The processing circuit is capable of producing at least two algebraic combinations, each algebraic combination including components of the first set of magnetic sensing elements and components of the second set of magnetic sensing elements to define two sinusoidal signals substantially 90° out of phase.

[0012] Patent Document 3It is also known and describes a solution to implement two 360° non-contact sensors to create an absolute multi-turn sensor. The first non-contact sensor is used to measure the rotation angle of a rotating member from 0 to 360°, and the second sensor is used to determine the number of complete rotations of the rotating member. A mechanical system for continuous gear reduction with ratio n is integrated between the two sensors. The input shaft of the reduction gear is connected to the first sensor, and the rotor of the second sensor is connected to the output shaft of the reduction gear. For every complete rotation of the first sensor, the second sensor rotates only 1 / n. The second sensor allows for measurements of the entire absolute angle with limited accuracy and resolution, but this problem is solved by allowing the first sensor to refine the measurements of the second sensor, thereby obtaining very good accuracy and resolution over 360°. In addition, if the first sensor fails, the second sensor can even detect the position in the rotation of the rotating member (with a resolution reduced by n), thus enabling the detection of the first sensor's malfunction.

[0013] Patent Document 4 This describes another solution for a linear or curved rotational motion magnetic sensor using at least one permanent magnet and at least one magnetic sensing element that are movable relative to each other, characterized in that the magnet has a magnetization direction that changes substantially linearly along the direction of movement of the magnet across a surface defined by the direction of movement and the normal direction, excluding diametrical magnetization in the case of a rotational sensor.

[0014] Patent Document 5Describes another disk-shaped solution having a point (P) rotatable about an axis (Z). The first sensor cooperates with a first magnetic element integral with the disk to measure the approximate angular position (θa) of the point (P) with respect to the origin (O). The second magnetic element is circumferentially disposed around the disk. The second sensor is disposed at the origin (O) and measures the angular position of the upstream end of this second magnetic element with respect to the origin (O) for the second magnetic element located on the opposite side of this second sensor. The means determines which second element is positioned opposite the second sensor as a function of the approximate angular position (θa). The means calculates the precise angular position (θ) of the reference point (P) as a function of the value measured by the second determined element and the second sensor.

Prior Art Documents

Patent Documents

[0015]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0016] Disadvantages of prior art The simplest prior art magnetic sensors cannot obtain an angular accuracy (or linear accuracy) sufficient to be successfully used in applications requiring high-precision positioning.

Means for Solving the Problems

[0017] Solution provided by the present invention The object of the present invention is to improve upon this major drawback by providing a simple and inexpensive device for magnetic measurement of angular or linear position. According to the most commonly accepted view, the present invention relates to a non-contact position sensor comprising a permanent magnet (or magnetic coding element) that generates a magnetic field, and at least one sensing element (or magnetic sensing element) of the magnetic field in at least two directions, wherein the permanent magnet is movable in the direction of movement, has a continuously variable magnetization along the direction of movement, and such change in magnetization according to various field components represents a shape corresponding to a combination of at least two (quasi)periodic contributions, and the sensor further comprises a computer for combining the values ​​of these field components and determining a precise position value.

[0018] The term "quasi-periodic" refers to a generalization of periodic combinations that have slight fluctuations from one period to another, but with a pattern that maintains a constant interval between each individual pattern.

[0019] The detection element may be optionally placed within the magnetic flux centrifuge.

[0020] This magnetization is advantageous because it has different periods p and n * The second pattern is a signal that carries the first pattern, and this dual pattern allows for the combination of coarse and fine measurements of position in the deflection motion, performed via measurements of at least two components of the magnetic field.

[0021] Advantageously, the carrier and carrier signals are indexed to each other to create a phase shift proportional to the bias motion performed.

[0022] According to certain embodiments, the carrier and carrier signal are non-periodic.

[0023] Preferably, the magnetization has at least one magnetic anomaly for detecting a given position in a complete mechanical rotation or bias motion.

[0024] According to one modified form, the magnetization change has a shape corresponding to a combination of three periodic changes, with period m * A third pattern of p (a real number m > 0, constant or variable over displacement) allows, for example, the detection of one or more given positions in a complete mechanical rotation or biased motion.

[0025] According to one modified form, the permanent magnet (or magnetic retaining element) comprises at least one multipole permanent magnet or multipole magnet assembly.

[0026] In one modified form, the permanent magnet is all or part of the rotor of an electric motor, generator, actuator, speed reducer, or coupler.

[0027] Advantageously, the permanent magnet consists of a set of current loops.

[0028] In one modified form, the magnetization change has a shape corresponding to a combination of numerous periodic or quasi-periodic fluctuations, enabling accurate detection of the position within the bias motion, determining the number of bias motions produced, and enhancing the accuracy of the measurement and its resilience to external disturbances (e.g., parasitic magnetic fields).

[0029] Advantageously, the magnetic sensing element comprises at least one Hall probe or a quasi-point assembly of the magnetic sensing element that measures at least two magnetic field component directions.

[0030] According to one alternative configuration, the magnetically sensitive element is composed of a magnetoresistive probe.

[0031] In another alternative configuration, the magnetically sensitive element is an eddy current probe.

[0032] In another alternative configuration, the magnetic sensing element comprises multiple probes.

[0033] According to a particular embodiment, the sensor further comprises means for calculating and storing the calculated angular value and / or linearity of the sensor.

[0034] According to a particular embodiment, the measuring device according to the present invention combines analog and digital detection of magnetic field components, for example, to save computation time.

[0035] Optionally, the device has a degraded operating mode (combination of field components) in the event of a failure of one of the field components, or an operating mode (combination of field components) that allows for compensation of measurement disturbances of external origin.

[0036] The present invention also relates to a measuring device comprising means for calculating and storing the calculated angular values ​​and / or linearity of a sensor.

[0037] The present invention also relates to the application of the aforementioned position sensors to a composite system including force, torque, acceleration, braking, phase shift, overall velocity, direction of movement, rotational speed, inertia, imbalance, vibration, noise, harmonic components, temperature, pressure, current, and voltage, or to the measurement of additional values.

[0038] Detailed description of one non-limiting exemplary embodiment The present invention will be better understood by reading the following description relating to non-limiting exemplary embodiments shown in the accompanying drawings. [Brief explanation of the drawing]

[0039] [Figure 1] A schematic diagram of the angular position sensor according to the present invention is shown. [Figure 2] An exemplary magnetization profile according to the present invention is shown. [Figure 3] This shows the curve of change in the magnetic field component measured by the measuring probe. [Figure 4] The curves and envelope signals of the change in magnetic field components measured by the measuring probe are shown. [Figure 5] This shows a curve of change in fine signal components, containing P increments that are phase-shifted by one-quarter of the period p. [Figure 6] The curves of change in signals Brad and Btan, and exemplary combinations of these signals for determining the "coarseness" of the angular value (atan) in bias motion are shown. [Figure 7] The curves of signal change in P increments derived from components Bz and Btan, and exemplary combinations of these signals for "fine-grained" determination of the angular value (atan) in bias motion are shown. [Figure 8] A second example of a magnetization profile according to the present invention and an explanation of the position measurement indicated by the red line are shown. [Figure 9] A third example of a magnetization profile according to the present invention, adjusted to N'=2, P'=32, and T'=0, is shown. [Figure 10] A fourth example of a magnetization profile according to the present invention, adjusted to N''=2, P''=82, and T''=0, is shown. [Figure 11] A fifth example of a magnetization profile according to the present invention, adjusted to N=8, P=32, and T=0, is shown. [Figure 12] This demonstrates a detection principle adapted to curved displacement. [Figure 13] This demonstrates a detection principle adapted to linear displacement. [Modes for carrying out the invention]

[0040] Mechanical structure of an exemplary angle sensor according to the present invention Figure 1 shows a rotation sensor structure according to the present invention. The magnetic flux generated by a disk-shaped permanent magnet (1) is collected around it via a magnetic flux collector that defines an air gap in which the detection elements (2, 3), typically a Hall probe, are located, if necessary, by one or two detection elements (2, 3) located radially or axially, which measure two components of magnetic induction along two orthogonal axes. In the prior art, the magnetization is variable in some cases in the diametrical direction and in other cases in the radial and / or axial directions.

[0041] It is known that each permanent magnet has a magnetization whose direction is defined by a magnetization vector. This magnetization vector defines the direction of the magnetic field inside the magnet. This direction depends on how the magnet is polarized during its manufacture. For example, a “ring” shaped non-polarized magnet placed in a sufficiently uniform unidirectional magnetic field has a magnetization direction oriented along the direction of this magnetic field. When the magnetic field is oriented perpendicular to the axis of rotation of the magnet (this is called diametrical magnetization), and the magnet rotates and moves around its axis, the direction of magnetization observed at a fixed point in space inside the magnet is therefore continuously variable according to a linear function. This invention relates to a family of sensors in which the magnetization direction of a permanent magnet changes multi-periodically. This is the case when the magnetization direction takes the same value when the magnet moves a predetermined distance (the period of the signal following one of the field components).

[0042] General principles of the present invention The sensors according to the present invention are distinguished by a complex magnetization profile that results in a multiperiodic change in the amplitude of magnetization (or orientation of magnetization relative to an axis or reference point) as a function of the relative trajectory between the measured air gap and the magnet, measured at a single measurement point, with respect to a single annular, disc-shaped, tubular, or annular magnet, as shown according to the non-limiting example in Figure 2. In this example, Bx=Brad (curve 10), By=Btan (curve 11), Bz (curve 12), and in this profile, the number of signal increments along various measurement axes is N=2, P=216, and T=4 (wherein N is the number of increments defined on the carrier signal, and P and T are the number of increments defined on the carried signal).

[0043] The magnetization level is measured at a single point by one or more magnetically sensitive elements located at substantially the same point, for example, by a Triaxis-type (trademark) Hall probe, enabling high-precision calculation of angular (or linear) position (<0.5° for detection performed with full rotation), and is relatively compact and easy to assemble.

[0044] The magnetization profile consists of a (carrier) pattern with period p containing p measurement increments, and a period p with N increments. * It exists according to an example of a (carrier) pattern of n (a real number n>0, constant or variable). This dual pattern allows for a combination of coarse detection (coarse output) and finer detection of absolute position (fine output). Measurement increments are constructed, for example, by measuring magnetic poles. Thus, two poles of opposite polarity can constitute a given period of the period.

[0045] Figure 2 illustrates the two patterns described above, enabling two types of position calculations: - A "coarse" output that enables reading of the position on rotation, this output signal consists of a predetermined number of N incremental measurements distributed over a measurement interval (e.g., 1 mechanical rotation), in which case the components [Brad, Btan] or [Bz, Btan] can be used to calculate the angle value by calculating the arctangent of the ratio of these components. - A "fine" output is carried by a "coarse" signal, which allows for localized precision in the measurement of angular position. This output signal contains a predetermined number of P measurement increments over the measurement interval, and in this precision case, the components [Bz, Btan] can be used to calculate the angular value. - Additionally, one or more magnetic anomalies causing an atypical flow (13) function as a “count rotations” metric, allowing for the counting of the number of rotations or events performed beyond the first bias motion. This output signal includes a predetermined number of T measurement increments over the measurement interval.

[0046] In the example shown in Figure 2, the proposed magnetization profile is noteworthy for N=2, P=216, and T=4.

[0047] By processing each signal and combining these signals, an absolute indication of the angular position is obtained for detection performed by one or more mechanical rotations of the sensor.

[0048] For other magnetization patterns and / or other collection points of field values, the field component field component B rad 、 B tan 、 and B z of Other combinations may be advantageous for calculating this absolute angular position.

[0049] The principle of calculating the position will be more easily understood through the description of an example having a simpler field profile, for example N = 2, P = 8, and T = 0 (Figure 3).

[0050] Component B z is , the transporting component having N increments (23) (refer to the curve (24) Poly(Bz) of the envelope signal average - Figure 4) and the transporting signal having P increments obtained by subtracting from the average of the envelope signal to signal B z (not shown in Figure 4) can be easily decomposed, and the curve (20) corresponds to the change in signal B rad of the curve (21) corresponds to the change in signal B tan and the curve (22) corresponds to the change in signal B z of.

[0051] Similarly, Btan component minutes , the component B z to provides an envelope at n increments of phase shifted by a quarter cycle n * p with respect to the equivalent signal calculated for. It also provides a detailed signal including p increments phase shifted by a quarter cycle p (Figure 5).

[0052] The average of the Bz envelope (denoted as env(Bz)) and the average of Btan (denoted as env(Btan)) can be combined, for example, by calculating the angle Theta(N) (where N refers to the number of increments) to calculate a "coarse" output signal: Theta(N)=Atan(env(Bz) / (env(Btan) * Gain))

[0053] Similarly, signal B rad This can be directly combined with the signal env(Btan) to determine the angle Theta(N) (where N refers to the number of increments). Theta(N) = Atan(Brad / (env(Btan) * Gain (displayed as atan in Figure 6)

[0054] The value of the "gain" parameter is calculated to bring the intensity ratio close to 1, limiting the distortion of the signal calculated relative to the ideal signal (shown as BFL, best fit line, in Figure 6).

[0055] Considering signal distortion and indexing deviation, the linearity of this signal, along with significant nonlinearity in the output signal, is perfectly sufficient to determine the angular position in rotation.

[0056] To further refine this angular position measurement, the signal can be combined with P increments resulting from components Bz and Btan, as shown in Figure 7.

[0057] When N=4, a precise linear signal is defined by 1 / 4 of the total mechanical deviation motion (e.g., one rotation of 360°).

[0058] By combining the two output signals, the following can be identified: ○ "Coarse" output: Angular sector of the measured increment P ○ Has a "fine" output: Precise angular value in this sector of the increment P.

[0059] In the example shown in Figure 8 (measurements at values ​​indicated by dotted lines), the "coarse" output shows a measurement of approximately 130° (therefore, the measurement points are located at the first increment N and the third increment P according to Bz), the "fine" output shows an electrical angle of 320° at increment P=3, which is 320 / P=40° mechanical angle at increment P3. For the accuracy of NL obtained with the "fine" output, it is 45°(first increment P) + 45°(second increment P) + 40°(reading at third increment P) = a total of 130°. Typically, an electrical angle of + / -3° over an increment P is, in this specification, + / -3° / P = + / -0.375° mechanical angle. Therefore, the measured value is absolutely 130° ± 0.375°.

[0060] By adding a rotation count index (T=1 or T=2, not shown), the counter can be incremented by easily detecting when the number of flow peaks detected in (for example) Bz exceeds a certain threshold. Thus, the angle value in the last rotation and the number of complete rotations produced can be determined.

[0061] Those skilled in the art will immediately understand that the angular accuracy of the sensor becomes increasingly important as the number of increments P is important.

[0062] We want to increase the accuracy of the ratio sensor relative to the same positional accuracy obtained from processing over an increment of N: To reach a mechanical angle of + / - 0.09°, P' / P = 4 (Figure 9) To reach a mechanical angle of + / - 0.036°, P'' / P = 10.25 (Figure 10).

[0063] For the practical implementation of this sensor, the following can be considered without limitation: A probe fixed to a moving magnet, A movable probe relative to a fixed magnet. ○ or a mixture of two preceding items

[0064] Mechanical structure of an exemplary linear or curved displacement sensor according to the present invention Figures 12 and 13 show alternative embodiments of curved and straight displacement sensors, respectively. forever The magnet (1) has a flat or curved shape (wound around a cylindrical hub) and has a magnetization whose orientation changes depending on field components corresponding to at least two different combinations of quasi-periodic contributions. A magnetic field sensing element (11) (or magnetic sensing element) in at least two directions makes it possible to calculate the value of the linear displacement.

[0065] The detection principle of the present invention can be easily adapted to measure linear or curved displacement. For this purpose, in order to properly understand the principle, it is sufficient to open and rewind a ring or magnetized disk (1) in one's mind (Figure 12): the magnetization profile changes continuously according to the linear motion of the resulting magnetic track (Figure 13).

[0066] The mode of position detection and calculation remains unchanged. The linear displacement value is obtained by indexing this displacement to the angular change of the magnetic field over which it is performed: for example, a 360° rotation of the magnetic field over a 20 mm path constitutes our carrier signal.

[0067] The superposition of more precise periodic patterns (e.g., a 360° rotation of the field over a 5mm path repeated over a total of 20mm) is considered to enable our carried signal to obtain a more precise detection of this linear displacement, as described earlier. Generally considering the accuracy of these 360° ±3° electrical angles, an accuracy of ±0.041mm is obtained for linear displacement.

[0068] Finally, by adding one or more point magnetic anomalies (which constitute our second carrier signal), it becomes possible to detect one or more specific locations on the linear displacement.

Claims

1. A non-contact position sensor comprising a permanent magnet (1) that generates a magnetic field, and at least one detection element (3, 11) of the magnetic field in at least two directions, wherein the permanent magnet (1) is movable in the direction of movement and has a continuously variable magnetization along the direction of movement. The change in magnetization is configured to generate a magnetic field component exhibiting a combination of at least two different quasi-periodic contributions, and the non-contact position sensor further comprises a computer configured to combine the detected values ​​of the magnetic field component and determine an accurate position value, wherein the magnetization is periodic p * A non-contact position sensor characterized by having a carrier frequency of n (n is a real number > 0, constant or variable in biased motion), determining a coarse position by measurement, and having at least one secondary signal carried by a lower period p, thereby providing a fine measurement of the position by processing the signal.

2. The non-contact position sensor according to claim 1, characterized in that the carrier and the carrier signal are indexed to each other, thereby creating a phase shift of the magnetic field component that is proportional to the deviation motion performed.

3. The non-contact position sensor according to claim 2, characterized in that the carrier and transport signal are non-periodic.

4. The non-contact position sensor according to claim 2, characterized in that the magnetization has at least one magnetic anomaly for detecting a predetermined position during a complete mechanical rotation or deflection motion.

5. The non-contact position sensor according to claim 2, characterized in that the permanent magnet comprises at least one multi-pole permanent magnet or a multi-pole magnet assembly.

6. The non-contact position sensor according to claim 1, characterized in that the permanent magnet is all or part of the rotor of an electric motor, generator, actuator, reducer, or coupler.

7. The non-contact position sensor according to claim 1, characterized in that the permanent magnet consists of a set of current loops.

8. The non-contact position sensor according to claim 1, characterized in that the detection element comprises at least one Hall probe or a quasi-fixed point assembly of a magnetic sensing element that measures at least two magnetic field components.

9. The non-contact position sensor according to claim 1, characterized in that the detection element consists of a magnetoresistive probe.

10. The non-contact position sensor according to claim 1, characterized in that the detection element is an eddy current probe.

11. The non-contact position sensor according to claim 1, characterized in that the detection element comprises a plurality of probes.

12. A measuring device comprising a non-contact position sensor according to any one of claims 1 to 11, the measuring device further comprising means for calculating an angle value and storing the calculated angle value.

13. A measuring device comprising a non-contact position sensor according to any one of claims 1 to 11, the measuring device including a degradation operation mode (combination of the magnetic field components) when one of the magnetic field components degrades.

14. A measuring device according to any one of claims 12 to 13, comprising an operating mode (combination of magnetic field components) that enables compensation for measurement disturbances of external origin.

15. The measuring device according to any one of claims 12 to 14, which combines analog detection and digital detection of the magnetic field component.

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