CN112113585B - Encoder and method for detecting absolute angle of encoder - Google Patents
Encoder and method for detecting absolute angle of encoder Download PDFInfo
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- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/12—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
- G01D5/14—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage
- G01D5/142—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage using Hall-effect devices
- G01D5/145—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage using Hall-effect devices influenced by the relative movement between the Hall device and magnetic fields
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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
Technical Field
The application relates to the technical field of encoders, in particular to an encoder and a detection method of an absolute angle of the encoder.
Background
The angular displacement sensor widely adopted by the high-precision servo platform in the field of industrial control at present comprises a rotary transformer, a photoelectric encoder and a magnetoelectric encoder. The magnetoelectric encoder is mainly composed of a permanent magnet and a magnetic sensing element. The magnetic sensing element can sense the space magnetic field change caused by the rotation of the permanent magnet through the Hall effect or the magnetic resistance effect, can convert the magnetic field change into the change of a voltage signal, and can achieve the purpose of detecting the angular displacement of the rotating component through a subsequent signal processing system. Compared with a rotary transformer and a photoelectric encoder, the magnetoelectric encoder has the advantages of simple structure, high temperature resistance, oil stain resistance, impact resistance, small volume, low cost and the like, and has unique advantages in application places with miniaturization and severe environmental conditions.
The magnetoelectric encoder is mainly composed of a magnetic signal generating structure and a signal processing circuit, wherein a magnetic signal generating source is called a magnet. The magnetoelectric encoders may be classified into a single-pair magnetoelectric encoder and a multi-pair magnetoelectric encoder according to the difference in the number of magnetic poles of the magnet. The current commonly used multi-pair pole magnetoelectric encoders mainly comprise the following components: one is a combined magnetoelectric encoder with a single pair of poles and a plurality of pairs of poles, and the other is a vernier caliper type magnetoelectric encoder with the difference of 1 between the pole pairs of the inner ring permanent magnet and the outer ring permanent magnet. The two multi-pair-pole magnetoelectric encoders acquire original magnetic field signals through 4 linear Hall elements. However, in the application process, the stress characteristic and the magnetic field characteristic of the single-pole permanent magnet are required, so that the angle measuring method of the combined encoder is not suitable for occasions with large axial diameters. The limiting condition that the difference of the pole pair number is 1 leads to the limited application condition of the encoder. For example, the original error of a multi-pair pole magnetoelectric encoder needs to be limited in a certain range, and the limitation condition that the difference between the pole pairs is 1 makes the requirement difficult to meet.
In addition, a magnetoelectric encoder adopts a double multi-pair-pole permanent magnet with inner and outer ring pole pairs which are coprime, adopts two linear Hall sensors to measure the single-period angle, and adopts a plurality of switch Hall sensors to measure the positions of magnetic poles. The magneto-electric encoder can be applied to working conditions of small axial size and large radial size, and the application range of the magneto-electric encoder is expanded on the basis of improving accuracy.
Disclosure of Invention
Based on this, this application provides an encoder, adopts many pairs of utmost point magnet and 4 linear hall sensor that adopt interior outer loop magnetic pole number to be reciprocal matter, can realize the absolute angle calculation of encoder.
According to a first aspect of the present application, there is provided an encoder comprising:
a first and a second plurality of pairs of polar magnets arranged coaxially and annularly, wherein,
the first multi-pair of polar magnets comprises m pairs of magnetic poles, the second multi-pair of polar magnets comprises n pairs of magnetic poles, and m and n are natural numbers larger than 2 and are coprime to each other;
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.
According to some embodiments of the present application, the output signals of the first and second linear hall sensors are 90 degrees out of phase.
According to some embodiments of the present application, the output signals of the third and fourth linear hall sensors are 90 degrees out of phase.
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 application, the first plurality of pairs of pole magnets are located on an outer ring, the second plurality of pairs of pole magnets are located on an inner ring, and m is greater than n.
According to some embodiments of the application, m and n are prime numbers.
According to some embodiments of the application, the first plurality of pairs of pole magnets are arranged with a magnetization direction coinciding with a radial or axial direction of the ring.
According to some embodiments of the application, the second plurality of pairs of pole magnets are arranged with a magnetization direction that coincides with a radial or axial direction of the ring.
According to a first aspect of the present application, there is provided a method for detecting an absolute angle of an encoder, which is applied to the encoder, and includes:
respectively obtaining a first group of detection signals or a second group of detection signals through a first group of Hall elements or a second group of Hall elements;
carrying out 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;
determining a magnetic pole interval corresponding to the first angle value according to the magnetic pole pair number m of the first multi-pair magnet, the magnetic pole pair number n of the second multi-pair magnet, the first angle value and the second angle value;
and calculating the absolute angle of the encoder according to the magnetic pole interval, the magnetic pole pair number m of the first multi-pair magnetic body and the first angle value.
According to some embodiments of the present application, performing an angle solution on the first set of detection signals or the second set of detection signals to obtain a first angle value or a second angle value includes:
carrying out A/D conversion 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;
obtaining an angle interval where the first group of detection signals or the second group of detection signals are located according to the positive and negative of the voltage values in the first group of voltage values or the second group of voltage values and the magnitude of the voltage values;
and obtaining a first angle value or a second angle value by adopting an arc tangent algorithm for the first group of voltage values or the second group of voltage values according to the angle interval.
According to some embodiments of the present application, determining a magnetic pole section corresponding to the first angle value according to the number of magnetic pole pairs m of the first multi-pair magnet, the number of magnetic pole pairs n of the second multi-pair magnet, the first angle value, and the second angle value includes:
determining a group of theoretical values of the characteristic values of the magnetic pole positions according to the number m of the magnetic pole pairs of the first multi-pair magnet and the number n of the magnetic pole pairs of the second multi-pair magnet;
obtaining a magnetic pole position characteristic calculation value according to the magnetic pole pair number m of the first multi-pair magnet, the magnetic pole pair number n of the second multi-pair magnet, the first angle value and the second angle value;
comparing the calculated magnetic pole position characteristic value with a group of theoretical values to obtain a magnetic pole position characteristic value;
and calculating the magnetic pole section according to the characteristic value of the magnetic pole position.
According to some embodiments of the application, obtaining a magnetic pole position feature calculated value from 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 comprises:
the calculated value of the magnetic pole position characteristic is calculated according to the following formula,
wherein, theta' i Is a first angle value, theta ', obtained by actual measurement' j For the second angle obtained by actual measurement, m is the number of pole pairs of the first multi-pair pole magnet, and n is the number of pole pairs of the second multi-pair pole magnet.
According to some embodiments of the application, comparing the calculated magnetic pole position characteristic value with a set of theoretical values to obtain a magnetic pole position characteristic value comprises:
carrying out interval expansion on the group of theoretical values to obtain a group of theoretical value intervals;
and taking the theoretical value corresponding to the interval containing the characteristic value of the magnetic pole position in the group of theoretical value intervals as the characteristic value of the magnetic pole position.
According to some embodiments of the present application, the performing interval expansion on the set of theoretical values to obtain a set of theoretical value intervals includes:
the interval expansion is performed according to the following formula,
wherein λ is i Is a magnet position characteristic theoretical value.
According to some embodiments of the present application, calculating an absolute angle of an encoder from the magnetic pole section, the number of magnetic pole pairs m of the first multi-pair 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
wherein, theta is an absolute angle value of the encoder; theta.theta. i A first angle value measured for a first set of linear hall; n is a radical of hydrogen i Is theta i The magnetic pole section is located; m being a first plurality of pairs of polar magnetsThe number of magnetic pole pairs m.
Additional aspects and advantages of the present application will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the present application.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without exceeding the protection scope of 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 of 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.
Fig. 4 shows a signal detection schematic diagram of a linear hall sensor in an encoder.
Fig. 5 is a schematic diagram illustrating a detection signal position of a linear hall element according to an exemplary embodiment of the present application.
Fig. 6 shows the inner and outer magnetic pole position intent of an example embodiment of the present application.
Fig. 7 is a diagram illustrating a number of values of a theoretical value of a magnetic pole position characteristic in an exemplary embodiment of the present application.
Fig. 8 is a diagram illustrating a distribution of magnetic pole position feature calculation values according to an exemplary embodiment of the present application.
Fig. 9 is a schematic diagram illustrating a magnetic pole position feature calculation value distribution interval according to an 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 Description
Example embodiments will now be described more fully hereinafter with reference to the accompanying drawings. Example embodiments may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. These embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of example embodiments to those skilled in the art. The same reference numerals denote the same or similar parts in the drawings, and thus, a repetitive description thereof 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 to give a thorough understanding of embodiments of the application. One skilled in the relevant art will recognize, however, that the embodiments of the present application can be practiced without one or more of the specific details, or with other methods, components, devices, steps, and so forth. In other instances, well-known methods, devices, implementations, or operations have not been shown or described in detail to avoid obscuring aspects of the 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 element from another. Thus, a first component discussed below could be termed a second component without departing from the teachings of the present concepts. 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 exemplary embodiments, which may not be to scale. The modules or processes in the figures are not necessarily required to practice the present application and therefore should not be used to limit the scope of the present application.
In the existing inner and outer ring pole pair number coprime multi-pair pole magnetoelectric encoder, two linear Hall elements are needed to measure the single-period angle, and a plurality of switch Hall elements are used for judging the magnetic pole interval. The inventor finds that in the use process of the encoder structure, under the condition that the number of pole pairs of the permanent magnet is large, a large number of switch Hall elements are needed. Therefore, the encoder structure cannot be applied to a case where the number of pole pairs of the annular permanent magnet is particularly large.
In order to solve the problem, the application provides a magnetoelectric encoder, uses many pairs of magnetic poles and four linear hall elements of the inner and outer ring pole pair reciprocity, realizes the detection of absolute angle to be applicable to the scene that the annular permanent magnet pole pair number is very many. The technical solution 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 of an exemplary embodiment of the present application.
As shown in fig. 1 and 2, the present application provides an encoder 100, including: a first plurality of pairs of polar magnets 110 and a second plurality of pairs of polar magnets 120 arranged coaxially and annularly in a first spatial plane. The first multi-pair polar magnet 110 includes m pairs of magnetic poles, and the second multi-pair polar magnet 120 includes n pairs of magnetic poles, where m and n are natural numbers greater than 2 and coprime to each other. For example, according to some embodiments, m and n are prime numbers. In the present embodiment, m is 5 and n is 3 as shown in fig. 1 and 2, but the present application is not limited thereto.
According to an example embodiment of the present application, the first multi-pair magnet 110 is located at the outer ring and the second multi-pair magnet 120 is located at the inner ring, and the number of poles m of the first multi-pair magnet 110 is greater than the number of poles n of the second multi-pair magnet 120. This is because the diameter of the outer ring is larger than that of the inner ring, and the number of magnets of the outer ring is larger than that of the inner ring in order to make the size of the magnets uniform.
According to some embodiments of the present application, the first multi-pair pole magnet 110 may be arranged with a magnetization direction that coincides with a radial or axial direction of the ring. In the embodiment shown in fig. 1 and 2, the magnetization direction of the first multi-pair pole magnet 110 is arranged to be axial. The second plurality of pairs of polar magnets 120 may also be arranged with a magnetization direction that coincides with the radial or axial direction of the ring. In the embodiment shown in fig. 1 and 2, the magnetization direction of the second multi-pair pole magnet 120 is set to be axial. The magnetization direction is not limited to this, and the magnetization direction of the first multi-pair pole magnet 110 may be set to be radial, the magnetization direction of the second multi-pair pole magnet 120 may be set to be axial, or the magnetization directions of the first multi-pair pole magnet 110 and the second multi-pair pole magnet 120 may be set to be radial, which is not limited in the present application.
The first and second multi-pair magnets 110 and 120 may be formed by adhering a plurality of magnetic pairs, but is not limited thereto. According to the embodiment of the application, the magnet can be made of neodymium iron boron permanent magnet materials, and a plurality of magnets can be attached to the substrate or directly attached to the end portion of the rotating shaft. According to some embodiments, a plurality of magnets may be disposed on the support plate. The support plate may have a ring-shaped configuration, and the second plurality of pairs of pole magnets 120 may be arranged along a circumferential normal direction of the inner hole thereof. The first plurality of pairs of polar magnets 110 are secured to the annular surface of the support plate. The fixing means may be an adhesive bond.
As shown in fig. 1 and 2, the encoder 100 further includes a first set of hall elements and a second set of hall elements for detecting magnetic signals generated by the multi-pole magnet. And a first group of hall elements including a first linear hall sensor 111 and a second linear hall sensor 112, which are disposed adjacent to the first multi-pole magnet 110, and which output a first group of detection signals according to magnetic pole signals of the first multi-pole magnet 110. The output signals of the first and second linear hall sensors 111 and 112 are 90 degrees out of phase.
And a second group of hall elements including a third linear hall sensor 121 and a fourth linear hall sensor 122, which are disposed adjacent to the second multi-pole magnet 120, and output a second group detection signal according to magnetic pole signals of the second multi-pole magnet 120. The output signals of the third and fourth linear hall sensors 121 and 122 are 90 degrees out of phase. According to some embodiments, in the encoder structure described above, the first linear hall sensor 111 and the third linear hall sensor 121 are aligned at one end.
Fig. 3 shows a flow chart of an encoder absolute angle detection method according to an example embodiment of the present application.
The present application further provides a method for detecting an absolute angle of the encoder, including:
in step S310, a first set of detection signals or a second set of detection signals is obtained through the first set of hall elements or the second set of hall elements, respectively.
The encoder provided by the application comprises a multi-pair-pole magnet with two groups of magnetic poles of an inner ring and an outer ring, wherein the magnetic poles are opposite and prime, the two groups of magnets are coaxially arranged on a motor rotating shaft and are isolated by adopting an isolation means so as to prevent magnetic field coupling. The magnetic field around the two sets of magnets appears sinusoidal in the circumferential direction. Two linear Hall sensors in the first group of Hall elements and the second group of Hall elements which are respectively arranged corresponding to the inner ring multi-pair pole magnets and the outer ring multi-pair pole magnets are arranged at an included angle of 90 degrees in electrical angle. The principle of two linear hall sensors detecting the magnetic signal of a set of multiple pairs of pole magnets is described below with reference to fig. 4 and 5.
Fig. 4 shows a signal detection schematic diagram of a linear hall sensor in an encoder.
Fig. 5 is a schematic diagram illustrating a detection signal position of a linear hall element according to an exemplary embodiment of the present application.
The magnetic field change of any point in the space of the magnet is regular when the magnet rotates along with the rotating shaft for a circle, the change can be converted into sine and cosine electric signals by utilizing two linear Hall sensors with the position difference of 90 degrees, and the change frequency of the electric signals is the same as the rotation frequency of the magnetic poles. As shown in fig. 4 and 5, for a group of multi-pair magnets with 3 pairs of poles, the magnetic poles rotate once, and the linear hall sensors a and B respectively detect three periods of sine and cosine signals, i.e., a group of detection signals. A first set of detection signals is obtained by a first set of Hall elements arranged on the outer ring. A second set of detection signals may be obtained by a second set of hall elements arranged in the inner ring.
In step S320, an angle solution is performed on the first set of detection signals or the second set of detection signals to obtain a first angle value or a second angle value.
After sine and cosine signals are obtained by using the linear Hall sensor, a digital voltage value with a certain digit can be obtained through the A/D conversion circuit. That is, the first group of detection signals or the second group of detection signals are a/D converted to obtain the first group of voltage values or the second group of voltage values. The digital voltage value at this time has a certain relationship with the measurement angle value of the encoder, but is not the measurement angle value of the encoder, and the angle calculation is also required.
For the signals of each group of magnetic poles, the positions of the two Hall sensors are different by 90 degrees in space, so that sine and cosine signals output by the two Hall sensors are different by 90 degrees in phase. At this time, the signal with the phase advance is regarded as a sine signal, and the signal with the phase lag is regarded as a cosine signal. And dividing the sine signal by the cosine signal to obtain a tangent value of the point signal, and then performing arc tangent processing on the tangent value to obtain an actual angle value of the point position.
Since the interval of the tangent function is [ -90 °,90 ° ], directly performing angle solution according to the above process will result in an interval error of angle solution. Therefore, it is necessary to solve the problem of interval errors by an interval dividing method, that is, obtaining the angle interval where the first group of detection signals or the second group of detection signals are located according to the positive and negative and the magnitude of the voltage value in the first group of voltage values or the second group of voltage values.
Taking the angle calculation of a set of magnetic poles as an example, 360 ° of the set of magnetic poles can be divided into 8 equal-length sections at intervals of 45 °. The position of the Hall signal at the moment is judged by judging the magnitude and the positive and negative of the detected voltage values of the two linear Hall elements, and the implementation principle of the inter-partition arc tangent algorithm is shown in the following table. The principle of implementing the angle solution of the inter-partition arctan algorithm is shown in table 1. Wherein, VA and VB are linear Hall detection signals with phase difference of 90 degrees.
TABLE 1 division of the Angle intervals
Through the division of the angle intervals, the conversion from the signals collected by the Hall elements to the angle signals can be realized, and the range of the converted angle intervals is [0 degrees, 360 degrees ].
For the encoder of the present application, the angle intervals in which the first group of detection signals and the second group of detection signals are located can be obtained according to the positivity, the negativity and the magnitude of the voltage values in the first group of voltage values and the second group of voltage values. From the angle interval, the first angle value or the second angle value can be obtained by applying the arctan algorithm to the first set of voltage values or the second set of voltage values according to table 1.
In the process of angle measurement, two groups of multi-pair pole magnets rotate along with the rotating shaft, and the linear Hall element is kept static and used for receiving a magnetic field signal of change generated by the magnetic poles in the rotating process. The induction signal of the linear hall is processed by the above-mentioned arc tangent table lookup method, and the angle value of the single magnetic pole period of the measuring magnet can be obtained. After the angular value of the single period is determined, the magnetic pole interval where the angular value is located needs to be determined, and then the absolute angular value detected by the encoder can be obtained.
In the encoder absolute angle detection method provided by the application, the magnetic pole section where the measurement angle is located is identified according to the relative position relationship between the two groups of magnets. For the two sets of multi-pole magnets, a first multi-pole magnet with a large number of pole pairs may be used as the measurement magnet, and a second multi-pole magnet with a small number of pole pairs may be used as the reference magnet. The absolute angle value can be calculated according to the following formula:
θ＝(N i -1)×360°/m+θ i /m (1)
wherein: theta is an absolute angle value output by the encoder; theta.theta. i Measuring the monocycle angle value measured by the magnet polar linear Hall element; n is a radical of i Is theta i The magnetic pole section is located; and m is the total number of pole pairs of the measuring magnet.
For the encoder shown in fig. 6, there is an angular difference θ between the initial magnetic pole mounting positions of the inner and outer sets of magnets x Then the absolute angle value of the encoder output can also be expressed as:
θ＝(N j -1)×360°/n+θ j /n+θ x (2)
wherein: theta is an absolute angle value output by the encoder; theta j The single period angle value measured for the reference magnet linear hall element; n is a radical of j Is theta j The magnetic pole section is located; n is the total number of pole pairs of the reference magnet.
On the basis of obtaining the first angle value or the second angle value, determining the corresponding magnetic pole section, and calculating the absolute angle value according to the formula (1) or (2).
In step S330, a magnetic pole section corresponding to the first angle value is determined according to the number of magnetic pole pairs m of the first multi-pole magnet, the number of magnetic pole pairs n of the second multi-pole magnet, the first angle value, and the second angle value.
When the linear Hall elements on the measuring magnet measure the same single-period angle, the two single-period angles measured by the linear Hall elements on the corresponding reference magnet are different, so that the magnetic pole pair number, namely the magnetic pole interval, where the measuring magnetic pole is located at present can be distinguished. With the encoder magnet structure provided by the present application, in the case where the greatest common divisor of the number m, n of the magnetic pole pairs of the measurement magnet and the reference magnet is 1, i.e., is relatively prime, each of the opposite poles of the measurement magnet has a non-repeating reference magnetic pole portion corresponding thereto. This is demonstrated below by a back-proof method.
Assuming the presence of a positive integer N i1 ,N i2 ,N j1 ,N j2 ,N i1 ≠N i2 The following equation holds:
wherein theta is i For measuring the angular value of a single period, N, measured by a linear Hall element of a magnetic pole i1 ,N i2 ∈[1,m]Two times for measuring theta i The corresponding measuring magnetic pole interval; theta.theta. j Angular value of monocycle measured for a linear hall of reference pole, N j1 ,N j2 ∈[1,n]Two times for measuring theta j A corresponding reference magnetic pole section; theta x The difference of the installation angle of the starting point of one pair of magnetic poles in the two groups of magnetic poles.
Subtracting the two equations in equation (3) yields:
since m, N are coprime, and N i1 -N i2 ∈[1,m-1]Therefore, the formula (4) is not established constantly, that is, the formula (3) is not established constantly.
Further from equation (4):
equation (5) for arbitrarily different N i And N corresponding thereto j Neither is true. That is, equation 5 does not hold for different measurement pole pairs and corresponding reference pole pairs. It can be demonstrated that when the linear hall elements on the measuring poles measure the same monocycle angle, the two monocycle angles measured by the linear hall elements on the corresponding reference poles are different. Thus, the magnetic pole section where the measuring magnetic pole is located at present can be distinguished through the position relation between the measuring magnetic pole and the reference magnetic pole.
Modified from equations (1) and (2) to obtain:
is provided with
And defined as a magnetic pole position characteristic value. As can be seen from equation (6), when the reference magnetic pole and the measurement magnetic pole are not changed, the magnetic pole position characteristic value is not changed. When at least one of them changes, the magnetic pole position characteristic value will also change and be different from the values corresponding to the other magnetic poles, otherwise equation (5) holds, contradictory to the premise that the magnetic pole pair is relatively prime. Therefore, the magnetic pole section where the magnetic pole is located at present can be determined by calculating the characteristic value of the magnetic pole position.
When theta is measured x When the magnetic pole position characteristic value lambda is not equal to 0, namely the starting points of a certain pair of magnetic poles of the two groups of magnetic poles of the inner ring and the outer ring are not superposed, the starting points of the coordinates cannot be changed to ensure that the magnetic poles are superposed, and the magnetic pole position characteristic value lambda has m + n different values. As shown in fig. 7.
Fig. 7 is a schematic diagram illustrating the number of values of the theoretical value of the magnetic pole position characteristic in the exemplary embodiment of the present application.
In fig. 7, the measurement magnet is m pairs of poles, and m is 3, so the planar development of 3 pairs of poles is represented by 3 boxes. The reference magnet is n antipodes, n is 2, and the reference magnet is flattenedAfter the surface is unfolded, 2 vertical lines are introduced in 3 boxes. Due to theta x Not equal to 0, therefore, a total of m + n +1 lines will be divided into m + n parts. That is, for an encoder having a set of 3 pairs of pole magnets and a set of 2 pairs of pole magnets, the position feature value has 5 different values. By analogy, for an encoder with 5 pairs of pole magnets and 3 pairs of pole magnets, the magnetic pole position characteristic value has 8 different values.
After the two groups of magnets of the inner ring and the outer ring are installed, theta x Then m + n different values are fixed. From the number m of pole pairs of the first multi-pair pole magnet and the number n of pole pairs of the second multi-pair pole magnet, a set of theoretical values of the characteristic values of the magnetic pole positions can be determined. Take the encoder structure shown in FIG. 6 as an example, θ x When the rotation direction of the magnet is clockwise =75 °, the characteristic values of the magnetic pole positions obtained by calibration and the corresponding magnetic pole sections are shown in table 2.
TABLE 2 correspondence between lambda values and measured poles
Fig. 8 is a diagram illustrating a distribution of magnetic pole position characteristic calculation values according to an exemplary embodiment of the present application.
In the process of using the encoder to carry out actual measurement, because the single-period angle calculation of the encoder has errors, random errors exist in the angle measurement of the reference magnetic pole and the angle measurement of the measurement magnetic pole. The calculated value of the magnetic pole position characteristic actually obtained by calculation is not a constant value when the current magnetic pole is not changed.
The error of the single-period angle solution of the outer ring magnetic pole and the inner ring magnetic pole is assumed to be sigma (sigma is more than 0). The theoretical value of the position characteristic of the magnetic theory before error introduction can be expressed as follows:
after the introduction of the error(s),
It can be seen that the value of λ changes from constant value to value range due to the existence of error
After introducing the error, the value of lambda is equivalent to the value obtained by performing the amplitude of lambda on the basis of the original theoretical value
As shown in fig. 8. In this case, if the fluctuation is too large, the magnetic pole determination sections overlap, and the position characteristic value fails.
In order to solve the problem of position characteristic value failure caused by angle errors, the set of theoretical values are subjected to interval expansion to obtain a set of theoretical value intervals. And then, taking the theoretical value corresponding to the interval containing the magnetic pole position characteristic calculated value in the group of theoretical value intervals as the magnetic pole position characteristic value. The following description is made with reference to fig. 8.
Because the length of each judgment interval is
In case of no overlap, the following relationship exists between λ values:
according to equation (6), the minimum pitch of the calculated values of the magnetic pole position characteristics can be expressed as:
for any N i None of the formulas (5) hold, and N i1 ,N i2 ,N j1 ,N j2 Are all positive integers, thus giving:
|n(N i1 -N i2 )-m(N j1 -N j2 )| min ≥1 (11)
substituting equation (11) into equation (9) yields:
in summary, in intervals
By distinguishing a group of theoretical value intervals of the magnetic pole position characteristic value, the problem of position characteristic value fluctuation can be solved, as shown in fig. 9.
In the actual detection process, the magnetic pole position characteristic calculation value lambda is calculated according to the following formula * ：
Wherein, theta' i Is a first angle value, theta ', obtained by actual measurement' j For the second angle value obtained by actual measurement, m is the number of pole pairs of the first multi-pair pole magnet, and n is the number of pole pairs of the second multi-pair pole magnet.
Calculated to obtain lambda * And then comparing the magnetic pole position characteristic calculation value with a group of theoretical value intervals P (i) to obtain a magnetic pole position characteristic value. For example, the λ is judged * 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), the identification of the magnetic pole position can be completed through the correspondence between the regions and the magnetic poles in table 2, that is, the magnetic pole interval is calculated according to the characteristic value of the magnetic pole position.
In step S340, an absolute angle of an encoder is calculated according to the magnetic pole section, the magnetic pole pair number m of the first multi-pole magnet, and the first angle value.
After the angle value of the single period and the magnetic pole interval where the angle value is located are determined, the absolute angle value detected by the encoder on the measuring magnetic pole can be obtained according to the formula (1).
Fig. 10 is a schematic diagram illustrating an absolute angle calculation process according to an exemplary embodiment of the present application.
As shown in fig. 10, according to the above scheme, the encoder provided by the present application is used to calculate the first angle values θ of the measurement magnetic pole and the reference magnetic pole through four linear hall sensors respectively i And a second angle value theta j Then, the absolute angle detection calculation process is performed as follows:
in step S101, the number of pole pairs m of the first multi-pair magnet, the number of pole pairs n of the second multi-pair magnet, and the first angle value θ are input i And a second angle value theta j And k =1 (k represents the cycle judgment time), k belongs to [1, m + n ]]。
In step S102, a 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 section P (k). If λ belongs to the section P (k), the process proceeds to step S103. If the lambda does not belong to the interval P (K), K = K +1, and the interval judgment is carried out again until the interval to which the lambda belongs is found.
In step S104, the magnetic pole section N is determined based on the correspondence relationship (shown in table 2) between the theoretical value of the characteristic magnetic pole position corresponding to the section P (i) to which λ belongs and the magnetic pole section i 。
In step S105, a first angle value theta is calculated based on the number of pairs m of magnetic poles of the first multi-pair magnet i A second angle value theta j A magnetic pole section N i The absolute angle θ is calculated according to the following formula.
θ＝(N i -1)×360°/m+θ i /m。
The application provides an encoder can realize the absolute angle of encoder and calculate through adopting many pairs of polar magnets and 4 linear hall elements of the inner and outer ring magnetic pole number coprime, has effectively solved and has used two linear hall elements, a plurality of switch hall element to carry out the application restriction problem that absolute angle calculated.
It should be noted that the embodiments described above with reference to the drawings are only intended to illustrate the present invention, and do not limit the scope of the present invention. It will be understood by those skilled in the art that various modifications and equivalent arrangements can be made without departing from the spirit and scope of the invention. Furthermore, unless the context indicates otherwise, words that appear in the singular include the plural and vice versa. Additionally, all or a portion of any embodiment may be utilized with all or a portion of any other embodiment, unless stated otherwise.
Claims (14)
1. A detection method of an absolute angle of an encoder comprises a first multi-pair magnet and a second multi-pair magnet which are coaxially and annularly arranged, wherein the first multi-pair magnet comprises m pairs of magnetic poles, the second multi-pair magnet comprises 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; 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-pole magnet, and output a second group of detection signals according to magnetic pole signals of the second multi-pole magnet; the detection method is characterized by comprising the following steps:
respectively obtaining a first group of detection signals and a second group of detection signals through a first group of Hall elements and a second group of Hall elements;
respectively carrying out 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;
determining a group of theoretical values of the characteristic values of the magnetic pole positions according to the number m of the magnetic pole pairs of the first multi-pair magnet and the number n of the magnetic pole pairs of the second multi-pair magnet;
obtaining a magnetic pole position characteristic calculated value according to the magnetic pole pair number m of the first multi-pair pole magnet, the magnetic pole pair number n of the second multi-pair pole magnet, the first angle value and the second angle value;
comparing the magnetic pole position characteristic calculation value with a group of theoretical values to obtain a magnetic pole position characteristic value;
calculating a magnetic pole interval corresponding to the first angle value according to the magnetic pole position characteristic value;
and calculating the absolute angle of the encoder according to the magnetic pole interval, the magnetic pole pair number m of the first multi-pair magnetic body and the first angle value.
2. The detection method according to claim 1, wherein performing an angle calculation on the first and second sets of detection signals to obtain first and second angle values comprises:
carrying out A/D conversion 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;
obtaining angle intervals of the first group of detection signals and the second group of detection signals according to the positive and negative of the voltage values in the first group of voltage values and the second group of voltage values and the magnitude of the voltage values;
and obtaining a first angle value and a second angle value by adopting an arc tangent algorithm for the first group of voltage values and the second group of voltage values according to the angle interval.
3. The detection method according to claim 1, wherein obtaining a magnetic pole position feature calculated value from 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 includes:
the calculated value of the magnetic pole position characteristic is calculated according to the following formula,
wherein, theta i ' first angle value obtained for actual measurement, θ j ' is a second angle value obtained by actual measurement, m is the number of pole pairs of the first multi-pair pole magnet, and n is the number of pole pairs of the second multi-pair pole magnet.
4. The detection method according to claim 1, wherein comparing the calculated magnetic pole position characteristic value with a set of theoretical values to obtain a magnetic pole position characteristic value comprises:
carrying out interval expansion on the group of theoretical values to obtain a group of theoretical value intervals;
and taking the theoretical value corresponding to the interval containing the magnetic pole position characteristic value in the group of theoretical value intervals as the magnetic pole position characteristic value.
5. The method of claim 4, wherein the step of performing interval expansion on the set of theoretical values to obtain a set of theoretical value intervals comprises:
the interval expansion is performed according to the following formula,
wherein λ is i Is a magnet position characteristic theoretical value.
6. The detection method according to claim 1, wherein calculating an absolute angle of an encoder from the magnetic pole section, the number m of magnetic pole pairs 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
wherein, theta is an absolute angle value of the encoder; theta.theta. i A first angle value measured for a first set of linear hall; n is a radical of i Is theta i The magnetic pole section is located.
7. An encoder capable of detecting an absolute angle by the detection method according to any one of claims 1 to 6, wherein there is an angular difference in the initial magnetic pole installation positions of the first and second multi-pair pole magnets.
8. The encoder of claim 7, wherein the output signals of the first and second linear hall sensors are 90 degrees out of phase.
9. The encoder of claim 8, wherein the output signals of the third and fourth linear hall sensors are 90 degrees out of phase.
10. The encoder of claim 9, wherein the first and third linear hall sensors are aligned at one end.
11. The encoder of claim 7, wherein the first plurality of pairs of pole magnets are located in an outer ring and the second plurality of pairs of pole magnets are located in an inner ring, and m is greater than n.
12. The encoder of claim 7, wherein m and n are prime numbers.
13. The encoder of claim 7, wherein the first plurality of pairs of pole magnets are arranged with a magnetization direction that coincides with a radial or axial direction of the ring.
14. The encoder of claim 13, wherein the second plurality of pairs of pole magnets are arranged with a magnetization direction that coincides with a radial or axial direction of the ring.
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| CN114216393B (en) * | 2022-02-21 | 2022-05-17 | 泉州昆泰芯微电子科技有限公司 | Rotation angle detection device, knob, learning tool, and entertainment tool |
| CN115824273B (en) * | 2022-09-23 | 2023-06-16 | 哈尔滨理工大学 | Spherical multi-winding magneto-electric encoder and angle resolving method thereof |
| CN117007086B (en) * | 2023-09-28 | 2023-12-08 | 山西省机电设计研究院有限公司 | High-precision magnetoelectric encoder and method for detecting absolute angle of magnetoelectric encoder |
| CN116989828B (en) * | 2023-09-28 | 2023-12-08 | 山西省机电设计研究院有限公司 | Large-diameter magnetic ring encoder and detection method for absolute angle of magnetic ring encoder |
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| US20120229123A1 (en) * | 2011-03-09 | 2012-09-13 | Chi-Yuan Cheng | Magnetic ring encoding device for composite signals |
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