阅读说明：本技术 用于确定旋转构件的至少一个旋转参数的系统 (System for determining at least one rotation parameter of a rotating member ) 是由 C·杜莱特 C·弗拉米尔 E·范达姆 于 2020-03-12 设计创作，主要内容包括：本公开涉及用于确定旋转构件的至少一个旋转参数的系统。本发明涉及一种系统,该系统包括：编码器,该编码器具有被沿着螺距为p、角度为α的螺旋线延伸的过渡区(3)间隔开的交替的北磁极(2n)和南磁极(2s),磁道(2)具有N<Sub>pp</Sub>对北极(2n)和南极(2s),并且具有沿着过渡区(3)的法线(N)测得的磁极宽度L<Sub>p</Sub>,其使得：N<Sub>pp</Sub>＝πa/l并且L<Sub>p</Sub>＝p*cosα；以及至少一个传感器,该至少一个传感器能够借助于至少两个灵敏磁性元件(5)的安装件(4、4’)来检测垂直于所述磁道和所述过渡区的平面中的旋转磁场,所述安装件被部署在距磁道(2)径向读取距离处并且被布置为递送正交信号。(The present disclosure relates to a system comprising an encoder having alternating north (2N) and south (2s) magnetic poles spaced by a transition region (3) extending along a helix of pitch p and angle α, the track (2) having N pp A north pole (2N) and a south pole (2s) and has a pole width L measured along a normal (N) of the transition region (3) p Which is such that: n is a radical of pp Pi a/L and L p P cos α, and at least one sensor capable of detecting, by means of the mounts (4, 4') of at least two sensitive magnetic elements (5), a perpendicular to said elementsA rotating magnetic field in the plane of the track and the transition zone, the mount being disposed at a radial read distance from the track (2) and arranged to deliver quadrature signals.)

1. A system for determining at least one rotation parameter of a rotating member, the system comprising:

-an encoder (1) intended to be rotationally associated with a rotating member in such a way as to move together with it, comprising a body having a cylindrical periphery with a radius a around a rotation axis (X), said periphery having alternating north (2n) and south (2s) poles of width/separated by transition zones (3), each of said transition zones extending along a helix of pitch p and angle α so as to form a multipolar track (2), said multipolar track (2) being able to be launched at a vertical to the rotating member, said multipolar track (2) being able to be launched with a high magnetic field strength, said multipolar track being able to be made to rotate along a single axis, said magnetic field strength being equal to the magnetic fieldA periodic magnetic field rotating in the plane of the track and the transition zone, the track having N_ppA north pole (2N) and a south pole (2s) and has a pole width L measured along a normal (N) of the transition region (3)_pSo that:

N_pppi a/L and L_p＝p*cosα；

-at least one sensor able to detect the rotating magnetic field emitted by the encoder by means of a mount (4, 4') of at least two sensitive magnetic elements (5) disposed at a radial reading distance from the track (2) and arranged to deliver orthogonal signals (V)₀₁、V₀₂；V'₀₁、V'₀₂)。

2. The system for determining according to claim 1, characterized in that said mount (4, 4') comprises a wheatstone bridge circuit with four sensitive elements (5), said circuit being disposed in a plane perpendicular to the track (2) so as to detect the magnetic field emitted by said track rotating in said plane.

3. System for determining according to one of claims 1 or 2, characterized in that each sensitive element (5) comprises at least one pattern with a tunnel magnetoresistive material substrate, the resistance of which varies according to the detected magnetic field.

4. System for determining according to one of claims 1 to 3, characterized in that it comprises two sensors whose mounts (4, 4') are obtained by delivering orthogonal signals (V), respectively₀₁、V₀₂；V'₀₁、V'₀₂) Spaced apart by a distance e measured along a normal (N) to the transition zone (3), the system further comprising means for subtracting the signals so as to form orthogonal signals (SIN, COS).

5. The system for determining according to claim 4, characterized in that said distance e is such that: e ═ L_pmod2L_p。

6. The system for determining according to claim 4, characterized in that said distance e is such that:

0.55L_pmod 2L_p<e<0.82L_pmod 2L_p(ii) a Or

1.18L_pmod 2L_p<e<1.45L_pmod 2L_p。

7. The system for determining of claim 6, wherein the distance e is substantially equal to 2/3L_pmod 2L_pOr 4/3Lp mod 2L_p。

Technical Field

The invention relates to a system for determining at least one rotation parameter of a rotating member, said system comprising an encoder emitting a periodic magnetic field and a sensor capable of detecting said magnetic field.

Background

In many applications, it is desirable to know at least one rotation parameter of a rotating member, such as its position, its speed, its acceleration or its direction of movement, in real time and with optimal mass.

For this purpose, document WO-2006/064169 proposes the use of an encoder intended to be integrated with the moving member and to form thereon a track capable of emitting a pseudo-sinusoidal magnetic field at a reading distance from a sensor comprising several sensitive elements.

Advantageously, each sensitive element may comprise at least one pattern having a substrate of tunnel magneto-resistive (TMR) material whose resistance varies in accordance with the magnetic field detected, for example as described in document WO-2004/083881.

In order to determine the movement parameters of the moving member from the variations of the detected magnetic field, document WO-2006/064169 provides a combination of signals representative of the resistance of each sensitive element, so as to deliver two signals that are orthogonal and of the same amplitude, which can be used to calculate said parameters.

Document WO-2018/051011 proposes a system for determination in which the track of the encoder has alternating north and south magnetic poles separated by transition zones, each pole extending along an archimedean spiral. This embodiment makes it possible to separate the number of poles, the width of the poles and the diameter of the encoder with respect to the axial reading of the magnetic field delivered by the encoder. It is thus possible to have few poles while still having a magnetic signal whose sinusoidality is good.

Moreover, some applications require a radial reading of the magnetic field delivered by the encoder, in particular due to limitations regarding the available space. To this end, an encoder is known which comprises a body having a cylindrical periphery with a track formed thereon, the track having a magnetic transition region aligned with the axis of rotation.

In this embodiment, the width of the magnetic pole is the ratio of the circumference to the number of magnetic poles, which causes problems for encoders with a small number of pole pairs (typically less than 6) because the magnetic pole width becomes quite large, in particular about ten millimeters.

These wide poles provide a poorly sinusoidal magnetic signal with low read gaps, becoming saturated with odd harmonics, unsuitable for accurate angular measurements, requiring sensitive elements far from the track, which is detrimental to the amplitude of the signal and therefore to its good detection by the sensitive elements.

In addition, a wide pole requires that the thickness of the encoder be also larger in order to keep the sinusoid and amplitude of the magnetic signal sufficient. This is disadvantageous for the integration of the encoder on a small area and complicates the magnetization method, since a larger thickness of material has to be magnetically saturated.

We also know from document JP-2003-979797971 a system in which two sensors are arranged with respect to a track for measuring the same unidirectional component of the magnetic field at two locations, the locations being determined such that the signals delivered by the sensors are orthogonal.

Disclosure of Invention

The present invention aims to complement the prior art by proposing a system for determination by radial reading of the magnetic field delivered by an encoder, in which a compromise can be reached between the periodicity and the amplitude of the detected magnetic field, without imposing any particular dimensional constraints on the encoder, which is particularly relevant for magnetic encoders in which the number of pole pairs is small.

In particular, the encoder with radial reading according to the invention allows the pole width of each pole to be independent of the number of pole pairs, so that a small number of pole pairs with suitably positioned sensitive elements can be coordinated with respect to the sinusoidity and amplitude of the magnetic field to be detected.

To this end, the invention proposes a system for determining at least one rotation parameter of a rotating member, said system comprising:

-an encoder intended to be rotationally associated with the rotating member in such a way as to move together with the rotating member, said encoder comprising a body having a cylindrical periphery with a radius a around the axis of rotation, said periphery having alternating north and south magnetic poles of width/separated by transition zones, each of said transition zones extending along a helix of pitch p and angle αThereby forming a multipole magnetic track capable of emitting a periodic magnetic field rotating in a plane perpendicular to said magnetic track and said transition zone, said magnetic track having N_ppFor north and south poles and having a pole width L measured along the normal to the transition region_pSo that: n is a radical of_ppPi a/L and L_p＝p*cosα；

-at least one sensor capable of detecting the rotating magnetic field emitted by the encoder by means of a mount of at least two sensitive magnetic elements, the mount being disposed at a radial read distance from the track and being arranged to deliver quadrature signals.

Drawings

Other features and advantages of the present invention will appear from the following description, with reference to the accompanying drawings, in which:

fig. 1a and 1b schematically show an encoder of a system for determining according to the invention in a perspective view (fig. 1a) and a side view (fig. 1b), respectively;

FIG. 2 is a plan view of the cylindrical periphery of the encoder of FIGS. 1a and 1 b;

fig. 3 schematically shows an embodiment of an arrangement according to the invention at a radial reading distance of the mount of the sensitive element with respect to the encoder;

FIG. 4 is a diagram of a mount for a sensitive element according to an embodiment of the present invention;

figure 5 shows quadrature signals delivered by the mount according to figure 4;

fig. 6 schematically shows an embodiment of an arrangement according to the invention at a radial reading distance of the mounts of two sensitive elements with respect to the encoder;

fig. 7 is an integrated view of the mount of fig. 6 in an apparatus for subtraction.

Fig. 8 is a graph showing the filtering of the third harmonic according to the distance between the mounts of the sensitive elements of the sensor.

Detailed Description

In connection with these figures, a system for determining at least one rotation parameter of a rotating member relative to a stationary structure is described. In particular, the parameters of the rotating member may be selected from its position, its speed, its direction of rotation, its acceleration or its direction of movement (in particular the axis).

In a particular application, the system may be used in connection with the control of a brushless dc motor, in particular so that the absolute angular position of a pair of motor poles of the rotor relative to the stator may be known.

The system for determining comprises an encoder 1 intended to be integrally formed with a rotary member to move therewith, said encoder comprising a body having a cylindrical periphery of radius a about a rotation axis X, on which a track 2 is formed, which track 2 is able to emit a periodic magnetic field representative of the rotation of said encoder. In particular, the emitted magnetic field may be sinusoidal or pseudo-sinusoidal, i.e. have at least one portion that can be correctly approximated by a sinusoid.

The track 2 has an alternation of north and south magnetic poles 2n, 2s of width l separated by transition zones 3, each of which extends along a helix of pitch p and angle a.

Thus, the track has N_ppFor north and south poles and has a pole width L measured along a normal N of the transition zone 3_pSo that: n is a radical of_ppPi a/L and L_pTrack 2 delivers a pseudo-sinusoidal magnetic signal with a spatial period along the normal N equal to λ 2L α_p. In particular, the periodic magnetic field delivered by the track 2 rotates in a plane perpendicular to said track and the transition zone 3.

The magnetic field generated by the encoder 1 on a pair of poles 2n, 2s is a combination of a perfect fundamental sinusoidal component to be measured for the purpose of determining the parameters and several odd-order harmonics (3, 5, etc.).

If it is assumed that the encoder 1 rotates at a constant rotational speed ω, the magnetic field can be represented in the following way:

H(t)＝H₁.sinωt+H₃.sin3ωt+H₅.sin5ωt+…

amplitude H of third harmonic₃Can generally represent the fundamental amplitude H ₁5 percent of. Amplitude H of the third harmonic depending on the position and read distance of the sensor₃This ratio of (c) may be much higher.

The spiral geometry of the track 2 is in particular such that the number N of pole pairs 2N, 2s_ppAnd a magnetic pole width L_pCan be chosen independently of the radius a of the track 2. With reference to fig. 1a and 1b, the encoder 1 comprises four pairs of poles 2n, 2s, which is particularly suitable for controlling a motor having four pairs of poles, the system providing an absolute position, i.e. a 90 ° mechanical angle, on one pair of motor poles.

According to an embodiment, the encoder 1 is formed by magnets on the cylindrical periphery of the multipole track 2. In particular, the magnet may be formed by an annular matrix, for example made of a substrate of plastic or elastomeric material, in which magnetic particles, in particular particles of ferrite or rare earth (such as NdFeB) are dispersed.

The system for determining comprises at least one sensor intended to be integral with the fixed structure, said sensor being able to detect the rotating magnetic field emitted by the encoder 1. To this end, the sensor comprises a mount 4 of at least two sensitive magnetic elements 5, which is disposed at a radial reading distance from the track 2, in order to deliver quadrature signals representative of the rotation of the encoder 1.

Each of the sensitive elements 5 may be chosen in particular from magnetically sensitive probes. For example, a Hall, tunneling magneto-resistive (TMR), anisotropic magneto-resistive (AMR), or giant magneto-resistive (GMR) probe can measure each of two components of the magnetic field (perpendicular and tangential to the encoder 1).

In particular, as described in document WO-2004/083881, each element 5 forms a tunnel junction by comprising a stack of a reference magnetic layer, an insulating spacer layer and a magnetic layer sensitive to the field to be detected, the resistance of the stack being dependent on the relative orientation of the magnetisation of the magnetic layers.

Advantageously, each sensitive element 5 may comprise at least one pattern with a substrate of magnetoresistive material, the resistance of which varies according to the magnetic field, in particular with a tunneling effect, the sensitive element 5 being able to comprise a single motif (motif) or a group of motifs connected in series or in parallel.

In order to be able to determine the rotation parameters of the rotating member, the signals delivered by the mount 4 of the sensitive element 5 must preferably be orthogonal, i.e. geometrically offset by 90 ° divided by N_pp. In particular, it is known to determine the angular position of the encoder 1 by using such quadrature signals in sensors or in associated calculators, for example by directly calculating the arctangent function using a look-up table (LUT) or CORDIC type of method.

To this end, with respect to fig. 4, the mount 4 may comprise two wheatstone bridge circuits with four sensitive elements 5, said circuits being disposed in a plane perpendicular to the track 2, so as to detect the magnetic field emitted by said track rotating in said plane.

In particular, fig. 5 shows the quadrature signal V delivered by the bridge as a function of the tilt angle γ of the magnetic field₀₁And V₀₂Which is such that:

V₀₁＝(+V₀₁)–(-V₀₁)；

V₀₂＝(+V₀₂)–(-V₀₂)。

with regard to the application of the system in controlling an electric motor, the signal delivered to the control calculator has a good sinusoidity allowing in particular:

better performance, in particular at start-up, for example in terms of time to reach a speed setting or a position setting;

a more "gentle" operation, with no torque shift occurring in steady state;

-less energy consumption;

-a lower operating temperature;

a greater maximum torque.

In particular, fig. 3 shows a mount 4 in an intermediate position on the periphery of the encoder 1 so as to be as far as possible apart from the edges of said encoder.

With respect to fig. 6, the system for determining comprises two sensors, whose mountings 4, 4' deliver orthogonal signals V respectively₀₁、V₀₂And V'₀₁、V'₀₂Spaced apart by a distance measured along the normal N of the transition zone 3e, the system further comprises means for subtracting the signals to form orthogonal SIN, COS signals.

Fig. 7 shows an embodiment in which the signals formed are:

SIN＝(+SIN)–(-SIN)；

+ SIN equals (+ V)₀₁)–(+V’₀₁),

-SIN is equal to (-V)₀₁)–(-V’₀₁)；

COS＝(+COS)–(-COS)；

+ COS equals (+ V)₀₂)–(+V’₀₂),

-COS equals (-V)₀₂)–(-V’₀₂)。

This embodiment allows filtering noise from the outside (e.g. from the motor or adjacent interconnects). In practice, if the magnetic field comprises the same noise component on different mounts 4, 4', this same noise component will be subtracted from the output signals SIN, COS.

By respectively in the magnetic phase phi₁And phi₂The mountings 4, 4' are positioned, i.e. by spacing them apart by a distance e measured along the normal N of the transition zone 3, such thatDelivered signal V₁(ii) COS or SIN and V₂either-COS or-SIN may be written as:

g is the assumed same gain of the mounting 4, 4', ω is the speed of rotation, H_iIs the amplitude of the fundamental frequency for i-1 and the amplitude of the ith harmonic for i-3, 5, etc.

The subtractor circuit calculates the SIN or COS difference, which is then written as:

with respect to fig. 6, L is equal to e_pmod 2L_pI.e., the mounts are offset by 180 ° mod 360 °, the difference is written as:

it can be seen that after the subtraction, the third and fifth harmonics are preserved and have the same gain 2 as the fundamental.

In order to obtain an accurate determination of the rotation parameter, a filtered signal of at least the third harmonic is measured. However, it is difficult to make any fixed compensation for the error caused by the harmonics, in particular because it depends on the measurement conditions (gap, position of the sensor). Furthermore, calibration is also difficult for large volume and low cost applications.

FIG. 8 shows a deviation valueFiltering the third harmonic.

When the distance e is substantially equal to 2/3L_pmod 2L_pOr 4/3L_pmod 2L_pWhen, the difference is written as:

in this case, the third harmonic is cancelled out, and after the subtraction, the gains of the fundamental wave and the fifth harmonic are 1.73. A third order harmonic spatial filter is then implemented while still retaining 86.5% of the fundamental.

In general, with respect to fig. 8, it is considered that a third-order harmonic filter will function if it removes at least 3dB from its value without filtering with respect to the amplitude of the fundamental wave, and therefore requires:

or

Expressed in terms of distance, in order to obtain filtering of the third order harmonics, it is therefore required that the mounts 4, 4' are spaced apart by a distance e measured along the normal N of the transition zone 3, which is such that:

0.55L_pmod 2L_p<e<0.82L_pmod 2L_p(ii) a Or

1.18L_pmod 2L_p<e<1.45L_pmod 2L_p

In particular, the distance e between the mounts 4, 4' may be varied within the ranges mentioned above in order to optimize the coupling filter-gain. Furthermore, the mounts 4, 4' may be aligned along the normal N of the transition zone 3, aligned along the axis X or offset along a circumference (fig. 6), depending on the available space.

Suppressing or at least attenuating third order harmonics in the processed signal to determine the rotation parameter is not only beneficial with respect to the accuracy of the determination, but also beneficial to the processing algorithm of the signal that performs the following operations:

-removing the offset of the signal;

-balancing the amplitude of the signal;

-phase correction between said signals.