CN112113585B - Encoder and method for detecting absolute angle of encoder - Google Patents

Abstract

The application provides an encoder and a method for detecting an absolute angle of the encoder. The encoder includes: the magnetic field generator comprises a first multi-pair of polar magnets and a second multi-pair of polar magnets which are coaxially and annularly arranged, wherein the first multi-pair of polar magnets comprise m pairs of magnetic poles, the second multi-pair of polar magnets comprise n pairs of magnetic poles, and m and n are natural numbers larger than 2 and are mutually prime; the first group of Hall elements comprise a first linear Hall sensor and a second linear Hall sensor, are arranged adjacent to the first multi-pole magnet, and output a first group of detection signals according to magnetic pole signals of the first multi-pole magnet; and the second group of Hall elements comprise a third linear Hall sensor and a fourth linear Hall sensor, are arranged adjacent to the second multi-pair-pole magnet, and output a second group of detection signals according to magnetic pole signals of the second multi-pair-pole magnet. The absolute angle detection of the encoder is realized through the 4 linear Hall elements, and the problem of the number of the Hall elements which are switched on and off is solved.

Description

Encoder and method for detecting absolute angle of encoder

technical field

The present application relates to the technical field of encoders, and in particular, to an encoder and a method for detecting an absolute angle of the encoder.

Background technique

At present, the angular displacement sensors widely used in high-precision servo platforms in the field of industrial control include resolvers, photoelectric encoders and magnetoelectric encoders. The magnetoelectric encoder is mainly composed of permanent magnets and magnetic sensitive elements. The magneto-sensitive element can sense the spatial magnetic field change caused by the rotating motion of the permanent magnet through the Hall effect or the magnetoresistance effect, and can convert this magnetic field change into a voltage signal change, and can achieve the rotation component through the subsequent signal processing system. The purpose of angular displacement detection. Compared with resolvers and photoelectric encoders, magnetoelectric encoders have the advantages of simple structure, high temperature resistance, oil resistance, shock resistance, small size, and low cost. They have unique advantages in applications with miniaturization and harsh environmental conditions.

The magnetoelectric encoder is mainly composed of a magnetic signal generating structure and a signal processing circuit. The source of the magnetic signal is called a magnet. According to the number of magnetic poles of the magnet, magnetoelectric encoders can be divided into single-pole magnetoelectric encoders and multi-pole magnetoelectric encoders. At present, the commonly used multi-pair magnetoelectric encoders mainly include the following: one is a combined magnetoelectric encoder with a single pair of poles and multiple pairs of poles; Electric encoder. The above two multi-pair magnetoelectric encoders collect the original magnetic field signals through 4 linear Hall elements. However, in the application process, the stress characteristics and magnetic field characteristics of the single pair of pole permanent magnets make the angle measurement method of the combined encoder unsuitable for occasions with large axial diameters. And the limitation of the difference of the number of pole pairs by 1 leads to the limitation of the application of the encoder. For example, the original error of a multi-pair magnetoelectric encoder needs to be limited within a certain range, and the limitation that the number of pole pairs differs by 1 makes it difficult to meet this requirement.

In addition, there is also a magnetoelectric encoder that uses double multi-pair pole permanent magnets with inner and outer ring pole pairs that are relatively prime, using two linear Halls to measure the single-cycle angle, and several switch Halls to measure the position of the magnetic poles . The encoder can be applied to the working conditions with small axial size and large radial size, and expands the application range of the magnetoelectric encoder on the basis of improving the accuracy.

SUMMARY OF THE INVENTION

Based on this, the present application provides an encoder, which can realize the absolute angle calculation of the encoder by adopting multiple pairs of pole magnets and four linear Hall sensors using inner and outer ring magnetic poles that are relatively prime.

According to a first aspect of the present application, an encoder is provided, comprising:

Coaxial annular arrangement of the first multi-pair pole magnets and the second multi-pair pole magnets, wherein,

The first multiple pairs of pole magnets include m pairs of poles, the second multiple pairs of pole magnets include n pairs of poles, and m and n are natural numbers greater than 2 and are relatively prime to each other;

The first group of Hall elements, including a first linear Hall sensor and a second linear Hall sensor, are arranged adjacent to the first multi-pair pole magnets, and output the first multi-pole magnet according to the magnetic pole signals of the first multi-pole magnets. a set of detection signals;

The second group of Hall elements, including a third linear Hall sensor and a fourth linear Hall sensor, are disposed adjacent to the second multi-pair pole magnets, and output the second multi-pole magnet according to the magnetic pole signals of the second multi-pole magnets. group heartbeat.

According to some embodiments of the present application, the phase difference between the output signals of the first linear Hall sensor and the second linear Hall sensor is 90 degrees.

According to some embodiments of the present application, the phase difference between the output signals of the third linear Hall sensor and the fourth linear Hall sensor is 90 degrees.

According to some embodiments of the present application, the first linear Hall sensor and the third linear Hall sensor are aligned at one end.

According to some embodiments of the present application, the first pairs of pole magnets are located in the outer ring, the second pairs of pole magnets are located in the inner ring, and m is greater than n.

According to some embodiments of the present application, m and n are prime numbers.

According to some embodiments of the present application, the first plurality of pairs of pole magnets are arranged such that the magnetization direction is consistent with the radial direction or the axial direction of the ring.

According to some embodiments of the present application, the second plurality of pairs of pole magnets are arranged such that the magnetization direction is the same as the radial direction or the axial direction of the ring.

According to a first aspect of the present application, a method for detecting an absolute angle of an encoder is provided, which is applied to the above-mentioned encoder, including:

Obtain the first group of detection signals or the second group of detection signals through the first group of Hall elements or the second group of Hall elements, respectively;

Perform angle calculation on the first group of detection signals or the second group of detection signals to obtain a first angle value or a second angle value;

The first angle value is determined according to the number m of magnetic pole pairs of the first multi-pair pole magnet, the number n of magnetic pole pairs of the second multi-pair pole magnet, the first angle value, and the second angle value The corresponding magnetic pole interval;

The absolute angle of the encoder is calculated according to the magnetic pole interval, the number m of magnetic pole pairs of the first multi-pole magnet, and the first angle value.

According to some embodiments of the present application, performing angle calculation on the first group of detection signals or the second group of detection signals to obtain a first angle value or a second angle value, including:

A/D conversion is performed on the first group of detection signals or the second group of detection signals to obtain a first group of voltage values or a second group of voltage values;

According to the positive or negative and the numerical value of the voltage values in the first group of voltage values or the second group of voltage values, obtain the angle interval where the first group of detection signals or the second group of detection signals are located;

According to the angle interval, the first angle value or the second angle value is obtained by using an arctangent algorithm for the first group of voltage values or the second group of voltage values.

According to some embodiments of the present application, according to the number m of pole pairs of the first multi-pair pole magnet, the number n of magnetic pole pairs of the second multi-pair pole magnet, the first angle value, the second angle value , determine the magnetic pole interval corresponding to the first angle value, including:

Determine a set of theoretical values of magnetic pole position characteristic values according to the number m of magnetic pole pairs of the first multi-pair pole magnet and the number n of magnetic pole pairs of the second multi-pair pole magnet;

According to the number m of magnetic pole pairs of the first multi-pair pole magnet, the number of magnetic pole pairs n of the second multi-pair pole magnet, the first angle value and the second angle value, obtain the magnetic pole position characteristic calculation value;

Comparing the calculated value of the magnetic pole position characteristic with a set of theoretical values to obtain the characteristic value of the magnetic pole position;

The magnetic pole interval is calculated according to the characteristic value of the magnetic pole position.

According to some embodiments of the present application, according to the number of pole pairs m of the first multi-pair pole magnet, the number of pole pairs n of the second multi-pair pole magnet, the first angle value and the second angle value , obtain the calculated value of the magnetic pole position feature, including:

The calculated value of the magnetic pole position characteristic is calculated according to the following formula,

Wherein, _θ'i is the first angle value obtained by actual measurement, _θ'j is the second angle obtained by actual measurement, m is the number of magnetic pole pairs of the first multi-pole magnet, and n is the second multi-pair The number of pole pairs of the pole magnet.

According to some embodiments of the present application, the calculated value of the magnetic pole position characteristic is compared with a set of theoretical values to obtain the characteristic value of the magnetic pole position, including:

performing interval expansion on the set of theoretical values to obtain a set of theoretical value intervals;

The theoretical value corresponding to the interval including the magnetic pole position characteristic value in the set of theoretical value intervals is used as the magnetic pole position characteristic value.

According to some embodiments of the present application, interval expansion is performed on the set of theoretical values to obtain a set of theoretical value intervals, including:

The interval expansion is performed according to the following formula,

Among them, λ _i is the theoretical value of the magnet position characteristic.

According to some embodiments of the present application, calculating the absolute angle of the encoder according to the magnetic pole interval, the number of pole pairs m of the first multi-pole magnet, and the first angle value, includes:

The absolute angle is calculated according to the following formula,

θ=(N _i -1)×360°/m+θ _i /m

Among them, θ is the absolute angle value of the encoder; θ _i is the first angle value measured by the first group of linear Halls; N _i is the magnetic pole interval where θ _i is located; m is the magnetic pole pair of the first multi-pole magnet number m.

Additional aspects and advantages of the present application will be set forth, in part, from the following description, and in part will become apparent from the following description, or may be learned by practice of the present application.

Description of drawings

In order to illustrate the technical solutions in the embodiments of the present application more clearly, the following briefly introduces the drawings that are used in the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can also be obtained from these drawings without exceeding the scope of protection claimed in the present application.

FIG. 1 shows a perspective view of an encoder structure according to an exemplary embodiment of the present application.

FIG. 2 shows a plan view of an encoder structure according to an exemplary embodiment of the present application.

FIG. 3 shows a flowchart of an absolute angle detection method according to an exemplary embodiment of the present application.

Figure 4 shows a schematic diagram of the linear Hall sensor signal detection in the encoder.

FIG. 5 shows a schematic diagram of the detection signal position of the linear Hall element according to the exemplary embodiment of the present application.

FIG. 6 shows a schematic diagram of the positions of the inner and outer magnetic poles of an example embodiment of the present application.

FIG. 7 shows a schematic diagram of the number of theoretical values of the magnetic pole position characteristic according to an exemplary embodiment of the present application.

FIG. 8 shows a schematic diagram of the distribution of calculated values of magnetic pole position characteristics according to an exemplary embodiment of the present application.

FIG. 9 shows a schematic diagram of the distribution interval of the calculated value of the magnetic pole position feature according to the exemplary embodiment of the present application.

FIG. 10 shows a schematic diagram of an absolute angle calculation process according to an exemplary embodiment of the present application.

Detailed ways

Example embodiments are described more fully below with reference to the accompanying drawings. Example embodiments, however, can be embodied in various forms and should not be construed as limited to the embodiments set forth herein. These embodiments are provided so that this application will be thorough and complete, and will fully convey the concept of example embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar parts, and thus their repeated descriptions will be omitted.

Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided in order to give a thorough understanding of the embodiments of the present application. However, those skilled in the art will appreciate that the technical solutions of the present application may be practiced without one or more of the specific details, or other methods, components, devices, steps, etc. may be employed. In other instances, well-known methods, devices, implementations, or operations have not been shown or described in detail to avoid obscuring aspects of the present application.

It will be understood that, although the terms first, second, etc. may be used herein to describe various components, these components should not be limited by these terms. These terms are used to distinguish one component from another. Accordingly, a first component discussed below could be referred to as a second component without departing from the teachings of the concepts herein. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

Those skilled in the art will appreciate that the drawings are merely schematic representations of example embodiments and may not be to scale. The modules or processes in the drawings are not necessarily necessary to implement the present application, and therefore cannot be used to limit the protection scope of the present application.

In the existing inner and outer ring pole pairs and coprime multi-pair pole magnetoelectric encoders, two linear Hall elements need to be used to measure the single-cycle angle, and several switch Hall elements are used to determine the magnetic pole interval. The inventors of the present invention found that, during the use of the encoder structure, when the number of pole pairs of the permanent magnets is large, a large number of switching Hall elements need to be used. Therefore, the encoder structure cannot be applied in the case where the number of pole pairs of the ring-shaped permanent magnet is particularly large.

In order to solve the above-mentioned problems, the present application provides a magnetoelectric encoder, which uses multiple pairs of magnetic poles and four linear Hall elements whose inner and outer ring pole pairs are relatively prime to realize the detection of absolute angle, thus being suitable for the number of ring permanent magnet pole pairs. A very large number of scenes. The technical solutions of the present application will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows a perspective view of an encoder structure according to an exemplary embodiment of the present application.

FIG. 2 shows a plan view of an encoder structure according to an exemplary embodiment of the present application.

As shown in FIG. 1 and FIG. 2 , the present application provides an encoder 100 , including: a first plurality of pairs of pole magnets 110 and a second plurality of pairs of pole magnets 120 that are coaxially arranged in a first space plane. The first multi-pair-pole magnet 110 includes m pairs of magnetic poles, and the second multi-pair-pole magnet 120 includes n pairs of magnetic poles, where m and n are natural numbers greater than 2 and are relatively prime to each other. For example, according to some embodiments, m and n are prime numbers. As shown in FIGS. 1 and 2 , in this embodiment, m is 5 and n is 3, but the present application is not limited thereto.

According to an example embodiment of the present application, the first multi-pair of pole magnets 110 are located in the outer ring, the second multi-pair of pole magnets 120 are located in the inner ring, and the number m of poles of the first multi-pair of pole magnets 110 is greater than that of the second multi-pair of poles The number n of opposite poles of the magnet 120 . This is because the diameter of the outer ring is larger than that of the inner ring, and in order to make the magnet size uniform, the number of magnets in the outer ring is larger than the number of magnets in the inner ring.

According to some embodiments of the present application, the first plurality of pairs of pole magnets 110 may be arranged such that the magnetization direction is consistent with the radial direction or the axial direction of the ring. In the embodiments shown in FIGS. 1 and 2 , the magnetization directions of the first plurality of pairs of pole magnets 110 are set in the axial direction. The second plurality of pairs of pole magnets 120 may also be arranged such that the magnetization direction is consistent with the radial direction or the axial direction of the ring. In the embodiment shown in FIGS. 1 and 2 , the magnetization directions of the second multiple pairs of pole magnets 120 are set in the axial direction. The magnetization direction is not limited to this, and the magnetization direction of the first multi-pair pole magnets 110 can also be set to be radial, and the magnetization direction of the second multi-pole magnet 120 can be set to the axial direction, or the first multi-pole magnets 110, the The magnetization directions of the two pairs of pole magnets 120 are all set to be radial, which is not limited in this application.

The first multiple pairs of pole magnets 110 and the second multiple pairs of pole magnets 120 may both be formed by adhering a plurality of pole pairs, but not limited thereto. According to the embodiments of the present application, the magnets can be made of NdFeB permanent magnet materials, and a plurality of magnets can be attached to the substrate, or directly attached to, for example, the end of the rotating shaft. According to some embodiments, a plurality of magnets may be provided on the support plate. The support plate may be an annular structure, and the second plurality of pairs of pole magnets 120 may be disposed along the circumferential direction of the inner hole of the support plate. The first plurality of pairs of pole magnets 110 are fixed on the annular surface of the support plate. The fixing method can be glued.

As shown in FIGS. 1 and 2 , the encoder 100 further includes a first group of Hall elements and a second group of Hall elements for detecting magnetic signals generated by the multiple pairs of pole magnets. The first group of Hall elements, including the first linear Hall sensor 111 and the second linear Hall sensor 112, are disposed adjacent to the first multi-pair pole magnets 110, and The magnetic pole signal outputs the first group of detection signals. The output signals of the first linear Hall sensor 111 and the second linear Hall sensor 112 have a phase difference of 90 degrees.

The second group of Hall elements, including the third linear Hall sensor 121 and the fourth linear Hall sensor 122, are disposed adjacent to the second multi-pair pole magnets 120, according to the magnetic poles of the second multi-pole magnets 120 The signal outputs a second set of detection signals. The output signals of the third linear Hall sensor 121 and the fourth linear Hall sensor 122 are out of phase by 90 degrees. According to some embodiments, in the above encoder structure, the first linear Hall sensor 111 and the third linear Hall sensor 121 are aligned at one end.

FIG. 3 shows a flowchart of a method for detecting an absolute angle of an encoder according to an exemplary embodiment of the present application.

The present application also provides a method for detecting the absolute angle of the above-mentioned encoder, comprising:

In step S310, the first group of detection signals or the second group of detection signals are obtained through the first group of Hall elements or the second group of Hall elements, respectively.

The encoder provided in this application includes two sets of magnetic pole pairs in the inner ring and the outer ring with multiple pairs of pole magnets that are relatively prime. coupling. The magnetic field around the two sets of magnets exhibits a sinusoidal distribution in the circumferential direction. The two linear Hall sensors in the first group of Hall elements and the second group of Hall elements respectively arranged corresponding to the inner and outer ring multi-paired pole magnets are arranged at an included angle of 90° electrical angle. The principle of detecting the magnetic signal of a group of multiple pairs of pole magnets by two linear Hall sensors is described below with reference to Figures 4 and 5.

Figure 4 shows a schematic diagram of the linear Hall sensor signal detection in the encoder.

FIG. 5 shows a schematic diagram of the detection signal position of the linear Hall element according to the exemplary embodiment of the present application.

The magnetic field changes regularly at any point in the space where the magnet rotates with the rotating shaft. Using two linear Hall sensors with a difference of 90°, this change can be converted into a positive and a cosine electrical signal, and the electrical signal changes. The frequency is the same as the frequency at which the magnetic poles rotate. As shown in Figures 4 and 5, for a group of multi-pole magnets with 3 pairs of poles, when the magnetic poles rotate once, the linear Hall sensors A and B respectively detect three periods of sine and cosine signals, that is, a group of detection signals. . The first group of detection signals can be obtained through the first group of Hall elements arranged in the outer ring. The second group of detection signals can be obtained through the second group of Hall elements arranged in the inner ring.

In step S320, angle calculation is performed on the first group of detection signals or the second group of detection signals to obtain a first angle value or a second angle value.

After the sine and cosine signals are obtained by applying the linear Hall sensor, the digital voltage value of a certain number of digits can be obtained through the A/D conversion circuit. That is, A/D conversion is performed on the first group of detection signals or the second group of detection signals to obtain the first group of voltage values or the second group of voltage values. At this time, although the digital voltage value has a certain relationship with the measured angle value of the encoder, it is not the measured angle value of the encoder, and angle calculation is required.

For the signals of each group of magnetic poles, the spatial positions of the two Hall sensors are different by 90°, so that the sine and cosine signals output by the two Hall sensors are different in phase by 90°. At this time, the signal with phase advance can be regarded as a sine signal, and the signal with phase lag can be regarded as a cosine signal. The tangent value of the signal at this point can be obtained by dividing the sine signal by the cosine signal, and then the arc tangent of the tangent value can be obtained to obtain the actual angle value of the position of the point.

Since the interval of the tangent function is [-90°, 90°], performing the angle calculation directly according to the above process will result in an error in the interval of the angle calculation. Therefore, it is necessary to solve the problem of interval errors by dividing the interval, that is, to obtain the first group of detection signals or the first group of detection signals according to the positive or negative and the magnitude of the voltage values in the first group of voltage values or the second group of voltage values. The angular interval where the two sets of detection signals are located.

Taking the angle calculation of a group of magnetic poles as an example, the 360° of the group of magnetic poles can be divided into 8 intervals of equal length at 45° intervals. The position of the Hall signal at this time is judged by judging the magnitude and positive and negative of the detected voltage values of the two linear Hall elements. The realization principle of the partition arc tangent algorithm is shown in the following table. The realization principle of the angle calculation of the interval arctangent algorithm is shown in Table 1. Among them, VA and VB are linear Hall detection signals with a phase difference of 90°.

Table 1 Division of angle intervals

Through the above division of the angle interval, the conversion of the signal collected by the Hall element into the angle signal can be realized, and the converted angle interval range is [0°, 360°].

For the encoder of the present application, according to the positive and negative voltage values and the magnitude of the voltage values in the first group of voltage values and the second group of voltage values, the angle interval where the first group of detection signals and the second group of detection signals are located can be obtained. According to the angle interval, the first angle value or the second angle value can be obtained by using the arc tangent algorithm for the first group of voltage values or the second group of voltage values according to Table 1.

In the process of angle measurement, two sets of multiple pairs of pole magnets rotate with the rotating shaft, and the linear Hall element remains stationary to receive the changing magnetic field signals generated by the magnetic poles during the rotation process. The induction signal of the linear Hall is processed by the above-mentioned arctangent look-up table method, and the angle value of a single magnetic pole period of the measuring magnet can be obtained. After the angle value of a single cycle is determined, the magnetic pole interval in which the angle value is located needs to be determined, so that the absolute angle value detected by the encoder can be obtained.

In the encoder absolute angle detection method provided by the present application, the magnetic pole interval where the measurement angle is located is identified according to the relative positional relationship between the two sets of magnets. For two sets of multi-pole magnets, the first multi-pair magnet with more pole pairs can be used as the measuring magnet, and the second multi-pair magnet with fewer pole pairs can be used as the reference magnet. The calculation of the absolute angle value can be carried out according to the following formula:

θ=(N _i -1)×360°/m+θ _i /m (1)

Among them: θ is the absolute angle value output by the encoder; θ _i is the single-cycle angle value measured by the linear Hall element of the measuring magnet pole; N _i is the magnetic pole interval where θ _i is located; m is the total number of magnetic pole pairs of the measuring magnet.

For the encoder shown in Figure 6, there is an angular difference θ _x between the initial magnetic pole installation positions of the inner and outer groups of magnets, and the absolute angle value output by the encoder can also be expressed as:

θ=(N _j -1)×360°/n+θ _j /n+θ _x (2)

Among them: θ is the absolute angle value output by the encoder; θ _j is the single-cycle angle value measured by the linear Hall element of the reference magnet; N _j is the magnetic pole interval where θ _j is located; n is the total number of magnetic pole pairs of the reference magnet.

On the basis of obtaining the first angle value or the second angle value, and determining the corresponding magnetic pole interval, the absolute angle value can be calculated according to formula (1) or (2).

In step S330, according to the number of magnetic pole pairs m of the first multi-pair pole magnet, the number of magnetic pole pairs n of the second multi-pair pole magnet, the first angle value, and the second angle value, determine the The magnetic pole interval corresponding to the first angle value.

When the same single-cycle angle is measured by the linear Hall element on the measuring magnet, the two single-cycle angles measured by the linear Hall on the corresponding reference magnet are different, so that the number of magnetic pole pairs where the measuring magnetic pole is currently located, that is, the magnetic pole interval can be distinguished. . For the encoder magnet structure provided in this application, when the greatest common divisor of the number of pole pairs m and n of the measuring magnet and the reference magnet is 1, that is, mutual prime, each pair of poles of the measuring magnet has a corresponding Non-repeated reference pole section. The following proves by contradictory method.

Assuming that there are positive integers N _i1 , N _i2 , N _j1 , N _j2 , N _i1 ≠N _i2 , the following formula holds:

Among them, θ _i is the single-cycle angle value measured by the Hall element of the measured magnetic pole linearity, N _i1 , N _i2 ∈[1,m], is the measurement magnetic pole interval corresponding to the two measured θ _i ; θ _j is the reference magnetic pole linearity The single-cycle angle value measured by Hall, N _j1 , N _j2 ∈[1,n], is the reference magnetic pole interval corresponding to the two measurements of θ _j ; θ _x is the installation angle of the starting point of a pair of magnetic poles in the two sets of magnetic poles Difference.

Subtracting the two equations in formula (3), we can get:

Since m and n are relatively prime, and N _i1 -N _i2 ∈[1,m-1], formula (4) is always invalid, that is, formula (3) is always invalid.

From formula (4), it can be further obtained:

Formula (5) does not hold for any different N _i and its corresponding N _j . That is, for different measurement magnetic pole pairs and corresponding reference magnetic pole pairs, Equation 5 does not hold. Therefore, it can be proved that when the linear Hall element on the measuring pole measures the same single-cycle angle, the two single-cycle angles measured by the linear Hall element on the corresponding reference magnetic pole are different. In this way, the magnetic pole interval in which the measured magnetic pole is currently located can be distinguished by the positional relationship between the measured magnetic pole and the reference magnetic pole.

From formula (1) and formula (2) deformation can be obtained:

并将其定义为磁极位置特征值。由公式(6)可以看出，当参考磁极与测量磁极不变时，磁极位置特征值不变。当其中至少一个变化时，磁极位置特征值也将变化，并且与其他磁极对应的值不同，否则等式(5)成立，与磁极对数互质的前提相矛盾。由此，可以通过计算磁极位置特征值来确定当前所在的磁极区间。Assume

and define it as the magnetic pole position eigenvalue. It can be seen from formula (6) that when the reference magnetic pole and the measuring magnetic pole are unchanged, the eigenvalue of the magnetic pole position is unchanged. When at least one of them changes, the magnetic pole position eigenvalues will also change and are different from the values corresponding to the other magnetic poles, otherwise equation (5) holds, contradicting the premise that the pole pairs are relatively prime. Therefore, the current magnetic pole interval can be determined by calculating the characteristic value of the magnetic pole position.

When θ _x ≠ 0, that is, the starting points of a pair of magnetic poles of the inner ring and the outer ring do not overlap, and cannot be made to overlap by changing the coordinate starting points, there are m+n different values of the magnetic pole position eigenvalue λ. As shown in Figure 7.

FIG. 7 shows a schematic diagram of the number of theoretical values of the magnetic pole position characteristic according to an exemplary embodiment of the present application.

In Fig. 7, the measuring magnet is m pairs of poles, and m is 3, so three boxes are used to represent the plane development of the three pairs of magnetic poles. The reference magnet is n pairs of poles, and n is 2. After plane expansion, it is equivalent to introducing 2 vertical lines into 3 boxes. Since θ _x ≠0, a total of m+n+1 lines will be divided into m+n parts. That is, for a set of encoders with 3 pairs of pole magnets and a set of 2 pairs of pole magnets, there are 5 different values for the position characteristic value. By analogy, for a set of encoders with 5 pairs of pole magnets and a set of 3 pairs of pole magnets, there are 8 different values for the magnetic pole position eigenvalues.

After the two sets of magnets in the inner and outer rings are installed, the value of θ _x has been determined, and the m+n different values are already fixed. According to the number m of magnetic pole pairs of the first multi-pair pole magnet and the number n of magnetic pole pairs of the second multi-pair pole magnet, a set of theoretical values of the eigenvalues of the magnetic pole position can be determined. Taking the encoder structure shown in FIG. 6 as an example, when θ _x = 75°, when the rotation direction of the magnet is clockwise, the eigenvalues of the magnetic pole position and the corresponding magnetic pole interval obtained by calibration are shown in Table 2.

Table 2 Correspondence between λ value and measuring magnetic pole

FIG. 8 shows a schematic diagram of the distribution of calculated values of magnetic pole position characteristics according to an exemplary embodiment of the present application.

In the actual measurement process using the above encoder, due to the error in the single-cycle angle solution of the encoder, there are random errors in the angle measurement of the reference magnetic pole and the measurement magnetic pole. Then, the calculated value of the magnetic pole position feature actually obtained by calculation is not a fixed value when the current magnetic pole is unchanged.

It is assumed that the errors of the single-cycle angle calculation of the outer ring magnetic pole and the inner ring magnetic pole are both σ (σ > 0). The theoretical value of the magnetic pole theory position characteristic before the error is introduced can be expressed as:

After introducing errors,

可以将其定义为磁极位置特征计算值。

It can be defined as the calculated value of the magnetic pole position feature.

引入误差后，λ的值相当于在原来理论值的基础上进行了幅值为

的无规则波动，如图8所示。在这种情况下，若波动过大，将导致磁极判断区间重叠，从而导致位置特征值失效。It can be seen that due to the existence of errors, the value of λ has changed from a fixed value to a range of values.

After introducing the error, the value of λ is equivalent to the amplitude value based on the original theoretical value.

random fluctuations, as shown in Figure 8. In this case, if the fluctuation is too large, the magnetic pole judgment intervals will overlap, resulting in the invalidation of the position characteristic value.

In order to solve the problem of the failure of the position eigenvalues caused by the angle error, the interval expansion is performed on the set of theoretical values to obtain a set of theoretical value intervals. Then, the theoretical value corresponding to the interval including the calculated value of the magnetic pole position characteristic in the set of theoretical value intervals is used as the magnetic pole position characteristic value. The following description will be made with reference to FIG. 8 .

要想不出现重叠的情况，λ值之间存在下列关系：Since the length of each judgment interval is

To avoid overlapping, the following relationship exists between the λ values:

According to formula (6), the minimum spacing of the calculated value of the magnetic pole position feature can be expressed as:

For any N _i , formula (5) does not hold, and N _i1 , N _i2 , N _j1 , and N _j2 are all positive integers, so we can get:

|n(N _i1 -N _i2 )-m(N _j1 -N _j2 )| _min ≥1 (11)

Substituting formula (11) into formula (9) can get:

对磁极位置特征值的一组理论值区间进行判别，可以解决位置特征值波动的情况，如图9所示。In summary, the interval

By judging a set of theoretical value intervals of the magnetic pole position eigenvalues, the fluctuation of the position eigenvalues can be solved, as shown in Figure 9.

In the actual detection process, the calculated value λ ^* of the magnetic pole position characteristic is calculated according to the following formula:

Among them, _θ'i is the first angle value obtained by actual measurement, _θ'j is the second angle value obtained by actual measurement, m is the number of pole pairs of the first multi-pair magnet, and n is the second multi-pair magnet. Pole pairs.

After λ ^* is calculated, the calculated value of the magnetic pole position characteristic is compared with a set of theoretical value intervals P(i) to obtain the characteristic value of the magnetic pole position. For example, it is determined that λ ^* belongs to the ith sub-interval P(i) of the set interval P. Then, according to the theoretical value λ corresponding to the ith sub-interval P(i), through the corresponding relationship between the regions and the magnetic poles in Table 2, the identification of the magnetic pole position can be completed, that is, according to the characteristic value of the magnetic pole position, the magnetic pole interval is calculated.

In step S340, the absolute angle of the encoder is calculated according to the magnetic pole interval, the number m of magnetic pole pairs of the first multi-pole magnet, and the first angle value.

After determining the angle value of a single cycle and the magnetic pole interval in which the angle value is located, the absolute angle value detected by the encoder on the measuring magnetic pole can be obtained according to the formula (1).

FIG. 10 shows a schematic diagram of an absolute angle calculation process according to an exemplary embodiment of the present application.

As shown in FIG. 10 , according to the above solution, using the encoder provided by the present application, the first angle value θ _i and the second angle value θ _j of the measurement magnetic pole and the reference magnetic pole are respectively calculated through four linear Hall sensors, and then the The calculation process of absolute angle detection is as follows:

In step S101, input the number of pole pairs m of the first multi-pair pole magnet, the number of pole pairs n of the second multi-pair pole magnet, the first angle value θ _i and the second angle value θ _j , and k=1 (k represents Cycle judgment times), k∈[1, m+n].

In step S102, the magnetic pole position characteristic value is calculated according to the following formula.

In step S103, the magnetic pole position characteristic value calculated in step S102 is compared with the magnetic pole position characteristic theoretical value interval P(k). If λ belongs to the interval P(k), go to step S103. If λ does not belong to the interval P(k), then K=K+1, and the interval judgment is performed again until the interval to which λ belongs is found.

In step S104, the magnetic pole interval Ni is determined according to the corresponding relationship between the theoretical value of the magnetic pole position characteristic corresponding to the interval P( _i ) to which λ belongs and the magnetic pole interval (as shown in Table 2).

In step S105 , the absolute angle θ is calculated according to the following formula according to the number m of magnetic pole pairs, the first angle value θ _i , the second angle value θ _j , and the magnetic pole interval _Ni of the first multi-pole magnet.

θ=(N _i −1)×360°/m+θ _i /m.

The encoder provided by this application can realize the absolute angle calculation of the encoder by using multiple pairs of pole magnets with mutually prime magnetic poles in the inner and outer rings and four linear Hall elements, effectively solving the problem of using two linear Hall elements and several switches. Application limitation of Hall element for absolute angle calculation.

It should be noted that the various embodiments described above with reference to the accompanying drawings are only used to illustrate the present invention, but not to limit the scope of the present invention. Those of ordinary skill in the art should understand that modifications or equivalent substitutions made to the present invention without departing from the spirit and scope of the present invention should all be included within the scope of the present invention. Furthermore, unless the context otherwise requires, words appearing in the singular include the plural and vice versa. Additionally, all or a portion of any embodiment may be used in conjunction with all or a portion of any other embodiment, unless specifically stated otherwise.

Claims (14)

1. A detection method for an absolute angle of an encoder, the encoder comprising a first multi-pair pole magnet and a second multi-pair pole magnet arranged in a coaxial ring, wherein the first multi-pair pole magnet comprises m pairs of magnetic poles , the second multiple pairs of pole magnets include n pairs of magnetic poles, m and n are natural numbers greater than 2 and are mutually prime; the first group of Hall elements includes a first linear Hall sensor and a second linear Hall sensor, and The first multiple pairs of pole magnets are arranged adjacent to each other, and output a first set of detection signals according to the magnetic pole signals of the first multiple pairs of pole magnets; the second set of Hall elements includes a third linear Hall sensor and a fourth linear Hall sensor. The Hall sensor is arranged adjacent to the second multi-pair pole magnet, and outputs a second set of detection signals according to the magnetic pole signals of the second multi-pair pole magnet; it is characterized in that, the detection method includes: Obtain the first group of detection signals and the second group of detection signals through the first group of Hall elements and the second group of Hall elements, respectively; Perform angle calculation on the first group of detection signals and the second group of detection signals to obtain a first angle value and a second angle value; Determine a set of theoretical values of magnetic pole position characteristic values according to the number m of magnetic pole pairs of the first multi-pair pole magnet and the number n of magnetic pole pairs of the second multi-pair pole magnet; According to the number m of magnetic pole pairs of the first multi-pair pole magnet, the number of magnetic pole pairs n of the second multi-pair pole magnet, the first angle value and the second angle value, obtain the magnetic pole position characteristic calculation value; Comparing the calculated value of the magnetic pole position characteristic with a set of theoretical values to obtain the characteristic value of the magnetic pole position; Calculate the magnetic pole interval corresponding to the first angle value according to the characteristic value of the magnetic pole position; The absolute angle of the encoder is calculated according to the magnetic pole interval, the number m of magnetic pole pairs of the first multi-pole magnet, and the first angle value. 2. The detection method according to claim 1, characterized in that, performing angle calculation on the first group of detection signals and the second group of detection signals to obtain the first angle value and the second angle value, comprising: A/D conversion is performed on the first group of detection signals and the second group of detection signals to obtain a first group of voltage values and a second group of voltage values; According to the positive and negative and the numerical value of the voltage values in the first group of voltage values and the second group of voltage values, obtain the angle interval where the first group of detection signals and the second group of detection signals are located; According to the angle interval, the first angle value and the second angle value are obtained by using an arctangent algorithm for the first group of voltage values and the second group of voltage values. 3 . The detection method according to claim 1 , wherein the number of pole pairs m of the first multi-pair pole magnet, the number of magnetic pole pairs n of the second multi-pair pole magnet, the first angle value and the second angle value to obtain the calculated value of the magnetic pole position feature, including: The calculated value of the magnetic pole position characteristic is calculated according to the following formula,

Wherein, θ _i ' is the first angle value obtained by actual measurement, θ _j ' is the second angle value obtained by actual measurement, m is the number of pole pairs of the first multi-pole magnet, and n is the second multi-pole magnet. The number of pole pairs for the counter magnet. 4. The detection method according to claim 1, wherein the calculated value of the magnetic pole position characteristic is compared with a set of theoretical values to obtain the characteristic value of the magnetic pole position, comprising: performing interval expansion on the set of theoretical values to obtain a set of theoretical value intervals; The theoretical value corresponding to the interval including the magnetic pole position characteristic value in the set of theoretical value intervals is used as the magnetic pole position characteristic value. 5. The detection method according to claim 4, characterized in that, performing interval expansion on the group of theoretical values to obtain a group of theoretical value intervals, comprising: The interval expansion is performed according to the following formula,

Among them, λ _i is the theoretical value of the magnet position characteristic. 6 . The detection method according to claim 1 , wherein the absolute angle of the encoder is calculated according to the magnetic pole interval, the number m of magnetic pole pairs of the first multi-pole magnet, and the first angle value, comprising: 7 . : The absolute angle is calculated according to the following formula, θ=(N _i -1)×360°/m+θ _i /m Among them, θ is the absolute angle value of the encoder; θ _i is the first angle value measured by the first group of linear Halls; N _i is the magnetic pole interval where θ _i is located. 7 . An encoder, characterized in that an absolute angle can be detected by the detection method according to any one of claims 1 to 6 , and the engagement between the first and second pairs of pole magnets is There is an angular difference in the installation position of the starting magnetic pole. 8 . The encoder according to claim 7 , wherein the output signals of the first linear Hall sensor and the second linear Hall sensor have a phase difference of 90 degrees. 9 . 9 . The encoder according to claim 8 , wherein the output signals of the third linear Hall sensor and the fourth linear Hall sensor have a phase difference of 90 degrees. 10 . 10. The encoder of claim 9, wherein the first linear Hall sensor and the third linear Hall sensor are aligned at one end. 11 . The encoder according to claim 7 , wherein the first plurality of pairs of pole magnets are located on the outer ring, the second multiple pairs of pole magnets are located on the inner ring, and m is greater than n. 12 . 12. The encoder of claim 7, wherein m and n are prime numbers. 13. The encoder according to claim 7, wherein the first plurality of pairs of pole magnets are arranged such that the magnetization direction is consistent with the radial direction or the axial direction of the ring. 14. The encoder according to claim 13, wherein the second multiple pairs of pole magnets are arranged such that the magnetization direction is the same as the radial direction or the axial direction of the ring.

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