System for determining at least one rotation parameter of a rotating member
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),所述磁道具有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;以及传感器,该传感器能够借助于至少两个灵敏磁性元件(4<Sub>1</Sub>、4<Sub>2</Sub>;5<Sub>1</Sub>、5<Sub>2</Sub>)检测由所述编码器发射的周期磁场,所述至少两个灵敏磁性元件部署在距磁道(2)径向读取距离处,所述灵敏元件相对于彼此部署成递送正交信号。(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 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 a sensor which can be activated by means of at least two sensitive magnetic elements (4) 1 、4 2 ;5 1 、5 2 ) Detection ofA periodic magnetic field emitted by the encoder, the at least two sensitive magnetic elements being disposed at a radial read distance from the track (2), the sensitive elements being disposed relative to each other to deliver orthogonal 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 rotary member in such a way as to move together with it, said encoder 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 multipole track (2), said multipole track (2) being capable of emitting a periodic magnetic field representative of the rotation of said encoder, said track having NppA 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 is a radical ofppPi a/L and Lp=p*cosα;
A sensor which can be activated by means of at least two sensitive magnetic elements (4, 5; 4)1、42;51、52) Detecting a periodic magnetic field emitted by the encoder, the at least two sensitive magnetic elements being disposed at a radial read distance from the track (2), the sensitive elements being disposed relative to each other to deliver orthogonal signals.
2. The system for determining according to claim 1, characterized in that the sensor comprises at least two sensitive elements (4, 5), the at least two sensitive elements (4, 5) being spaced apart by a distance d measured along the normal (N) of the transition region (3), d being equal to Lp/2mod Lp。
3. The system for determining according to claim 2, characterized in that said two sensitive elements (4, 5) are aligned along a circumferential direction.
4. The system for determining according to claim 2, characterized in that the two sensitive elements (4, 5) are aligned along a normal (N) of the transition zone (3).
5. The system for determining according to claim 2, characterized in that said two sensitive elements (4, 5) are aligned along a rotation axis (X).
6. System for determining according to claim 1, characterized in that said sensor comprises at least two sets of two sensitive elements (4)1、42;51、52) One group of sensitive elements (4)1、42;51、52) With another set of sensitive elements (5)1、52、41、42) Is separated by a distance d measured along the normal (N) of the transition region (3), d being equal to Lp/2mod Lp。
7. System for determining according to claim 6, characterized in that said sensor further comprises two sensitive elements (4) for subtracting each of said groups1、42;51、52) Delivered signal (V)1,V2) The apparatus of (1).
8. System for determining according to one of claims 6 or 7, characterized in that a set of sensitive elements (4)1、42;51、52) Spaced apart by a distance e measured along the normal (N) to the transition zone (3), the distance e being such that: e ═ Lpmod 2Lp。
9. System for determining according to one of claims 6 or 7, characterized in that a set of sensitive elements (4)1、42;51、52) Spaced apart by a distance e measured along the normal (N) to the transition zone (3), the distance e being such that:
0.55Lpmod 2Lp<e<0.82Lpmod 2Lp(ii) a Or
1.18Lpmod 2Lp<e<1.45Lpmod 2Lp。
10. The system for determining of claim 9, wherein the distance e is substantially equal to 2/3Lpmod 2LpOr 4/3Lpmod 2Lp。
11. System for determining according to any of claims 6 to 10, characterized in that the sensitive element (4)1、42;51、52) Are aligned.
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.
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 a rotary member in such a way as to move together with the rotary 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 α so as to form a multipole track capable of emitting a periodic magnetic field representative of the rotation of said encoder, said track having NppFor north and south poles and having a pole width L measured along the normal to the transition regionpSo that:Npppi a/L and Lp=p*cosα;
-a sensor capable of detecting the periodic magnetic field emitted by the encoder by means of at least two sensitive magnetic elements disposed at a radial read distance from the track, the sensitive elements being disposed relative to each other so as to deliver orthogonal 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;
FIGS. 3a and 3b schematically show alternative embodiments of the arrangement at a radial reading distance with respect to the sensitive element of the encoder according to the invention, respectively;
fig. 4a and 4b schematically show alternative embodiments of the arrangement at a radial reading distance with respect to the group-wise sensitive elements of the encoder according to the invention, respectively;
fig. 5a, 5b and 5c schematically show alternative embodiments of the arrangement at a radial reading distance with respect to the group-wise sensitive elements of the encoder according to the invention, respectively;
fig. 6 is a graph showing the filtering of the third harmonic according to the distance between the sensitive elements of the group.
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
The
Thus, the track has NppFor north and south poles and has a pole width L measured along a normal N of the
In particular, the magnetic field generated by the encoder 1 on a pair of
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
The spiral geometry of the
According to an embodiment, the encoder 1 is formed by magnets on the cylindrical periphery of the
The system for determining comprises a sensor intended to be integrated with the fixed structure, said sensor being able to detect the periodic magnetic field emitted by the encoder 1. To this end, the sensor comprises at least two sensitive
Each of the
In particular, as described in document WO-2004/083881, each
Advantageously, each
Alternatively, hall elements may be used, for example, to measure the normal component of the magnetic field delivered by the encoder 1 only. The use of the normal field alone is advantageous because it corrects the chording more than the tangential field.
In order to be able to determine the rotation parameters of the rotating member, the signals delivered by the
To this end, with respect to fig. 3a and 3b, the sensor comprises at least two
Thus, a good compromise is obtained between the sinusoidity and the amplitude of the detected signal. In particular, a pole width L of between 2mm and 6mm may be utilizedpThen even using N of the encoder 1pp(this number is less than 6) pairs of
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. 3a shows two
With respect to fig. 4a to 5c, the sensor comprises at least two sets of two sensitive elements 41、42;51、52In which a set of sensitive elements 41、42;51、52With another set of sensitive elements 41、42;51、52Is separated by a distance d, measured along the normal N of the
Thus, with respect to such repetition of the
In practice, it is assumed that the sensor also comprises two sensitive elements 4 for subtracting each of these groups1、42;51、52Delivered signal (V)1,V2) If the magnetic field is in different sensitive elements 41、42;51、52Including the same noise component, the same noise component will be subtracted from the output signal.
By respectively in the magnetic phase phi1And phi2Position a set of sensitive elements 41、42;51、52I.e. by spacing them apart by a distance e measured along the normal N of the
g is a sensitive element 41、42;51、52Is the assumed same gain, ω is the speed of rotation, HiIs for a fundamental frequency amplitude sum pair of i-1The amplitude of the ith harmonic at
The subtractor circuit calculates a difference, which is then written as:
with respect to fig. 4a and 4b, L is equal to epmod 2LpI.e. a set of sensitive elements 41、42;51、52Offset 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
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. 6 shows a method for determining a deviation value according to an offset value
Filtering the third harmonic.With respect to the case where the distance e is substantially equal to 2/3Lpmod 2LpOr 4/3Lpmod 2LpFig. 5a to 5c, 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. 6, it is considered that a third-order harmonic filter will work if it removes at least 3dB from its value without filtering with respect to the amplitude of the fundamental wave, so it is required:
or
Expressed in terms of distance, in order to obtain filtering of the third harmonic, a set of sensitive elements 4 is therefore required1、42;51、52Spaced apart by a distance e measured along the normal N of the
0.55Lpmod 2Lp<e<0.82Lpmod 2Lp(ii) a Or
1.18Lpmod 2Lp<e<1.45Lpmod 2Lp
In particular, a set of sensitive elements 41、42;51、52The distance e between can be varied within the ranges mentioned above in order to optimize the coupling filter-gain. In addition, a set of sensitive elements 4, according to the available space1、42;51、52May be aligned along the normal N (fig. 4a and 5b) or along the circumference (fig. 5c) of the
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.
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