CN117289186B - A magnetic grid sensor - Google Patents

Abstract

The present invention provides a magnetic grid sensor. The magnetic grid sensor includes one or more magnetic induction elements composed of four magnetoresistances connected in series or in parallel. The four magnetoresistances are TMR or AMR and are spatially distributed to form The square array; combined with the specific bias settings and sensitivity settings between the four magnetoresistances, the magnetic grid sensor has the ability to resist interference magnetic fields in the sensitive direction and interference magnetic fields perpendicular to the sensitivity direction, and reduces the assembly of the magnetic grid sensor. Accuracy requirements. The magnetic grid sensor provided by the present invention has strong anti-interference ability, high measurement accuracy, simple assembly, and has strong fault tolerance for its own position deviation during its movement relative to the magnetic grid scale.

Description

A magnetic grid sensor

Technical field

This application relates to the technical field of magnetic sensors or the technical field of position detection, and specifically to a magnetic grid sensor with strong anti-interference ability and high stability.

Background technique

Displacement detection, especially high-precision displacement detection, is one of the key technologies required in the fields of automatic control and measurement and detection. Especially in aerospace, machinery manufacturing, high-precision CNC machine tools and other application fields, it is often necessary to obtain the position of the observation object in real time and with high precision. Limited by the system's limitations on the position sensor and the processing capabilities of other parts of the system for position information, the displacement sensor is generally required to have high resolution, small size, light weight, fast response speed, good stability, etc. It is best to be able to Conveniently output digital signals.

The magnetic grid measurement system is the most commonly used and basic type of digital displacement sensor system. The magnetic grid displacement sensor system, due to its high resistance to vibration and impact, is suitable for use in industrial environments such as water, oil, dust, and high temperatures; and due to its simple structure, small size, and high measurement accuracy, it can meet a large number of applications Scenario constraints on displacement sensors are widely used.

The magnetic grid displacement magnetic sensor is a device that uses the mutual magnetic interaction between the magnetic head (magnetic grid sensor) and the magnetic scale to measure displacement. It mainly consists of a control circuit, a magnetic head, a magnetic scale and other parts. Among them, the magnetic scale uses non-magnetic metal as the base, or steel plated with a layer of antimagnetic material (such as 0.15-0.20mm thick copper) as the base; the surface of the base is evenly coated with This is achieved by layering a magnetic film with a thickness of 0.10-0.20mm (commonly used is Ni-Co-P alloy), and then recording a magnetic signal of a certain wavelength (small magnetic poles arranged at equal distances). When the magnetic grating sensor moves, the periodically changing magnetic field will generate changing magnetic field signals through the magnetically sensitive part of the sensor, thereby measuring the position and movement of the sensor.

In actual use, while the magnetic grid sensor senses the periodic magnetic field of the magnetic scale, it is also affected by the interference magnetic field, resulting in reduced detection accuracy. The interference magnetic field does not only exist in the direction of the magnetic pole arrangement of the magnetic scale (magnetic grid direction), but also exists in the direction perpendicular to the magnetic pole arrangement of the magnetic scale. In fact, in addition to the environmental magnetic field such as the geomagnetic field, the interference magnetic field also comes from the assembly process of the sensor and the movement of the magnetic head relative to the magnetic grid. The influence of this part of the interference magnetic field is often not only ignored, but also the measurement impact it brings is difficult to eliminate. As shown in Figure 1, when the magnetic induction unit is composed of corrected magnetic resistance C1 and magnetic resistance in series with opposite sensitive directions (both parallel to the arrangement direction of the magnetic poles of the magnetic scale). In the absence of other external field interference, the sensed magnetic grid magnetic field has no component perpendicular to the sensitivity only when the corrected magnetoresistance C1 and magnetoresistance R1 are at the N-S level horizontal central axis of the magnetic grid. However, this position is difficult to achieve in actual assembly. Even if it is as close to the central axis as possible, due to the deviation/jitter in the movement of the magnetic head relative to the magnetic grid, the position of the corrected magnetic resistance C1 and the magnetic resistance R1 relative to the "central axis" is also in the process of changing, and the self-felt The magnetic field component perpendicular to the magnetic pole arrangement direction of the magnetic scale is also constantly changing.

Contents of the invention

In order to solve the above-mentioned shortcomings of the existing magnetic grid sensors and enable the magnetic grid sensors to suppress the influence of the interference magnetic field perpendicular to the direction of the magnetic pole arrangement of the magnetic grid scale, the invention provides a device with strong anti-interference ability, high measurement accuracy and good assembly process. Magnetic sensor for less stringent requirements.

The technical solution provided by the present invention is implemented as: a magnetic grid sensor, including one or more magnetic induction elements composed of four magnetoresistances connected in series or in parallel. The four magnetoresistances are TMR or AMR and are spatially distributed. form phalanx. Two of the four magnetoresistances constitute the first group of magnetoresistance, and the remaining two constitute the second group of magnetoresistance; the bias magnetic fields of the two magnetoresistances in the first group of magnetoresistance and the second group of magnetoresistance are equal in size. And the directions are opposite and perpendicular to the periodic arrangement direction of the NS magnetic poles of the magnetic scale. The two magnetic resistors in the first group of magnetic resistors are connected in space parallel to the periodic arrangement direction of the NS magnetic poles of the magnetic scale, and the two magnetic resistors in the second group of magnetic resistors are respectively in NS with respect to the magnetic poles of the magnetic scale. The periodic direction is symmetrical about the central axis. The bias magnetic field directions of any two reluctances in the first group of reluctances and the second group of reluctances that are symmetrical about the central axis of the magnetic poles of the magnetic scale in the NS periodic direction are opposite.

Furthermore, the two magnetoresistive sensitivity coefficients in the first group of magnetoresistance are of the same size, and the sensitive direction of one magnetoresistive is parallel to the periodic arrangement direction of N-S magnetic poles of the magnetic scale, while the sensitive direction of the other magnetoresistive is anti-parallel. In the direction of the N-S periodic arrangement of magnetic poles of the magnetic scale; the sensitive directions of any two reluctances in the first group of magnetoresistance and the second group of magnetoresistance that are symmetrical about the central axis of the magnetic scale magnetic poles in the N-S periodic direction are the same. Through the spatial arrangement of the four magnetoresistances of the magnetic induction element, any magnetoresistance in the direction parallel and perpendicular to the magnetic pole arrangement of the magnetic scale has a phase to eliminate the influence of the interference field in the direction perpendicular to the arrangement of the magnetic scale. Magnetic resistance. Even if the magnetic grating sensor is displaced/jittered in the direction perpendicular to the magnetic scale arrangement during use, the stability and accuracy of the measurement signal can be maintained.

Preferably, the distance between the two magnetic resistors in the first group of magnetic resistors in the direction parallel to the periodic arrangement of the N-S magnetic poles of the magnetic scale is d:

;

Among them, k is an odd number, and L is the magnetic grating pitch. Such setting can increase the output signal of the magnetic induction element and improve the output sensitivity.

Preferably, the distance between the two magnetic resistors in the first group of magnetic resistors in the direction parallel to the periodic arrangement of the N-S magnetic poles of the magnetic scale is d:

;

Among them, L is the magnetic grating pitch, and n is an even number greater than 2. Such an arrangement can suppress the even harmonic error of the magnetic induction element and improve the quality of the output signal.

Preferably, the distance between the two magnetic resistors in the first group of magnetic resistors in the direction parallel to the periodic arrangement of the N-S magnetic poles of the magnetic scale is d:

;

Among them, L is the magnetic grating pitch, and m is an odd number greater than 1. By arranging the magnetoresistance in the magnetic induction element along the above-mentioned distance parallel to the N-S pole periodic arrangement direction of the magnetic grating, odd harmonic errors of the magnetic induction element are suppressed and the quality of the output signal is improved.

Further, the magnetic grating sensor includes at least an inductive half bridge composed of two of the magnetic inductive elements, and each of the magnetic inductive elements serves as an arm of the inductive half bridge; the same inductive half bridge The projection distance of the two magnetic induction elements of the bridge in the direction parallel to the periodic arrangement of N-S magnetic poles of the magnetic scale is D:

;

Among them, L is the magnetic grating pitch, and k is a positive integer.

Further, the magnetic grating sensor includes at least a Wheatstone full bridge composed of two inductive half bridges. The phase difference between the output signals of the two inductive half-bridges constituting the Wheatstone full bridge is set to , to eliminate the h-order harmonic error; where h is a positive integer.

The magnetic grid sensor provided by the present invention has high detection accuracy and anti-interference ability. It can not only suppress the influence of the interference magnetic field parallel to the magnetic pole arrangement direction of the magnetic scale scale and perpendicular to the magnetic pole arrangement direction of the magnetic scale scale, but also eliminate the influence of the magnetic grid sensor. The impact of jitter on measurement during use. The magnetic grid sensor provided by the present invention also has the characteristics of mature and simple manufacturing process and easy assembly (the assembly process requirements are not strict).

Description of the drawings

In order to explain the technical solutions of the embodiments of the present application more clearly, the drawings required to be used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present application and therefore do not illustrate the technical solutions of the embodiments of the present application. It should be regarded as a limitation of the scope. For those of ordinary skill in the art, other relevant drawings can be obtained based on these drawings without exerting creative efforts.

Figure 1 is a schematic diagram of the core part of an existing anti-interference magnetic grid sensor.

Figure 2 is a schematic diagram of the magnetic grating sensor provided by the present invention in one embodiment.

Detailed ways

The technical solution of the present invention will be described clearly and completely below with reference to the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

In the embodiment shown in Figure 2, the magnetic grid sensor provided by the present invention includes one or more magnetic induction elements composed of four magnetoresistances connected in series or in parallel. The four magnetoresistances are TMR or AMR (respectively). are R1, R2, R3, R4) in Figure 2, distributed in space to form phalanx.

Among the four magnetic resistors, R1 and R2 constitute the first group of magnetic resistors, and R3 and R4 constitute the second group of magnetic resistors. The two magnetoresistance bias magnetic fields in the first group of magnetoresistance and the second group of magnetoresistance are equal in magnitude and opposite in direction, and are both perpendicular to the periodic arrangement direction of the N-S magnetic poles of the magnetic scale. The directions of the bias magnetic fields of the four magnetoresistances are as shown by the corresponding arrows in Figure 2. The bias magnetic fields of the magnetoresistances R1 and R2 are in opposite directions, the bias magnetic fields of the magnetoresistances R3 and R4 are in the opposite directions, and the magnetoresistances R1-R4 are in the opposite direction. The directions of the bias magnetic field are perpendicular to the periodic arrangement direction of the N-S magnetic poles of the magnetic scale. The spatial position connection line of the magnetic resistors R1 and R2 is parallel to the N-S magnetic pole periodic arrangement direction of the magnetic scale. The spatial position connection line of the magnetic resistors R3 and R4 is also parallel to the N-S magnetic pole periodic arrangement direction of the magnetic scale scale. The positions of the magnetic resistance R1 and the magnetic resistance R3, and the positions of the magnetic resistance R2 and the magnetic resistance R4 are respectively symmetrical about the central axis of the magnetic pole of the magnetic scale in the N-S periodic direction. The bias magnetic field directions of any two reluctances in the first group of reluctances and the second group of reluctances that are symmetrical about the central axis of the magnetic poles of the magnetic scale in the N-S periodic direction are opposite.

Through the above-mentioned spatial arrangement of the magnetic resistors R1-R4, any magnetic resistor can have adjacent magnetic resistors to eliminate magnetic field interference perpendicular to the magnetic pole arrangement direction of the magnetic scale. Even if the magnetic grating sensor is displaced/jittered in the direction perpendicular to the magnetic scale arrangement during use, the stability and accuracy of the measurement signal can be maintained. As shown in Figure 2, if the positions of the magnetic reluctances R1 and R3 can remain symmetrical with respect to the central axis of the magnetic poles of the magnetic scale in the N-S periodic direction, then theoretically, the cooperation of the magnetic reluctances R1 and R3 and the cooperation of the magnetic reluctances R2 and R4 can be used to offset the vertical The interference of the magnetic field in the direction of the periodic arrangement of the N-S magnetic poles of the magnetic scale. Even if the magnetic grid sensor is in actual use (in motion relative to the magnetic scale), it jitters in the direction perpendicular to the magnetic pole arrangement of the magnetic scale, causing the magnetic resistance R3, R1, and the magnetic resistance R2, R4 to be unable to maintain the magnetic poles relative to the magnetic scale. It is symmetrical about the central axis in the N-S periodic direction. At this time, the magnetic resistance R1 and R2 cooperate with each other, and the magnetic resistance R3 and R4 cooperate with each other to eliminate the interference of the magnetic field perpendicular to the N-S magnetic pole periodic arrangement direction of the magnetic scale. Even if the magnetic grating sensor is displaced/jittered in the direction perpendicular to the magnetic scale arrangement during use, the stability and accuracy of the measurement signal can be maintained.

Further, in order to make the magnetic grid sensor have the anti-interference ability of the magnetic field that is parallel to the N-S magnetic pole periodic arrangement direction of the magnetic grid scale, the sensitivity coefficients of the magnetoresistances R1 and R2 in the first group of magnetoresistance are set to be the same, In the opposite direction. One of the sensitive directions of the magnetoresistance R1 and R2 is parallel to the periodic arrangement direction of the N-S magnetic poles of the magnetic scale, and the sensitive direction of the other magnetoresistance is anti-parallel to the periodic arrangement direction of the N-S magnetic poles of the magnetic scale. The sensitive directions of magnetic resistors R1 and R3 are the same, and the sensitive directions of magnetic resistors R2 and R4 are the same. Through the above-mentioned limitations on the sensitive directions of the magnetoresistance R1-R4, the magnetic grid sensor provided by the present invention can not only eliminate the influence of the interference magnetic field perpendicular to the arrangement direction of the magnetic scale scale, but also eliminate the influence of the magnetic pole arrangement direction parallel to the magnetic scale scale. on the influence of interfering magnetic fields.

Preferably, the distance between the two magnetic resistors in the first group of magnetic resistors in the direction parallel to the periodic arrangement of the N-S magnetic poles of the magnetic scale is d:

;

Among them, k is an odd number, and L is the magnetic grating pitch. Such setting can increase the output signal of the magnetic induction element and improve the output sensitivity.

Preferably, the distance between the two magnetic resistors in the first group of magnetic resistors in the direction parallel to the periodic arrangement of the N-S magnetic poles of the magnetic scale is d:

;

Among them, L is the magnetic grating pitch, and n is an even number greater than 2. Such an arrangement can suppress even harmonic errors in the output signal of the magnetic induction element and improve the quality of the output signal.

Preferably, the distance between the two magnetic resistors in the first group of magnetic resistors in the direction parallel to the periodic arrangement of the N-S magnetic poles of the magnetic scale is d:

;

Among them, L is the magnetic grating pitch, and m is an odd number greater than 1. By arranging the magnetoresistance in the magnetic induction element along the above distance parallel to the N-S pole periodic arrangement direction of the magnetic grating, odd harmonic errors in the output signal of the magnetic induction element can be further suppressed and the quality of the output signal can be improved.

Further, the magnetic grating sensor includes at least an inductive half bridge composed of two magnetic inductive elements; the two magnetic inductive elements in the inductive half bridge respectively serve as the inductive half bridge. 2 bridge arms (that is, each magnetic induction element serves as a bridge arm of the induction half bridge); the projection distance of the two magnetic induction elements of the same induction half bridge in the direction parallel to the periodic arrangement of the N-S magnetic poles of the magnetic scale. for D:

;

Among them, L is the magnetic grating pitch, and k is a positive integer.

Further, the magnetic grating sensor includes at least a Wheatstone full bridge composed of two inductive half bridges. Preferably, the phase difference between the output signals of the two inductive half-bridges constituting the Wheatstone full bridge is set to , to eliminate the h-order harmonic error; where h is a positive integer.

For this Wheatstone full-bridge circuit, the signals output by its two inductive half-bridges respectively contain h-order harmonics, that is, sinθ+ sinhθ and sin(θ+2π/h) + sinh(θ+2π/h) respectively. The output of the Wheatstone full bridge is the difference between the outputs of the two inductive half bridges and is sinθ-sin (θ+2π/h). As a result, the h-order harmonic error is eliminated.

The above descriptions are only preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of this application shall be included in the protection scope of this application. The above are only specific embodiments of the present application, but the protection scope of the present application is not limited thereto. Any person familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application. should be covered by the protection scope of this application. Therefore, the protection scope of this application should be determined by the protection scope of the claims.

Claims (8)

1. A magnetic grating sensor is characterized by comprising one or more magnetic induction elements formed by connecting 4 magnetic resistances in series or parallel, wherein the 4 magnetic resistances are TMR or AMR and are distributed in spaceIs a square matrix of (a);

2 of the 4 magnetoresistors form a first set of magnetoresistors, and the remaining 2 form a second set of magnetoresistors; the 2 magnetic resistance bias magnetic fields in the first group of magnetic resistance and the second group of magnetic resistance are equal in size and opposite in direction and are perpendicular to the periodic arrangement direction of the N-S magnetic poles of the magnetic grid ruler; the position connecting lines of the 2 magnetic resistances of the first group of magnetic resistances on the space position are parallel to the periodic arrangement direction of the N-S magnetic poles of the magnetic grid ruler, and are respectively symmetrical to the 2 magnetic resistances of the second group of magnetic resistances about the central axis of the magnetic poles of the magnetic grid ruler in the N-S periodic direction; any 2 magnetic resistances in the first group of magnetic resistances and the second group of magnetic resistances which are symmetrical about the central axis of the magnetic grid ruler magnetic pole in the N-S period direction have opposite bias magnetic field directions.

2. The magnetic grid sensor according to claim 1, wherein 2 magneto-resistance sensitivity coefficients in the first set of magneto-resistances are the same in magnitude, wherein 1 magneto-resistance sensitivity direction is parallel to the magnetic grid ruler N-S magnetic pole periodic arrangement direction, and the other 1 magneto-resistance sensitivity direction is anti-parallel to the magnetic grid ruler N-S magnetic pole periodic arrangement direction; the sensitivity directions of any 2 magnetic resistances in the first group of magnetic resistances and the second group of magnetic resistances, which are symmetrical with respect to the central axis of the magnetic grid ruler magnetic pole in the N-S period direction, are the same.

3. The magnetic grid sensor according to claim 2, wherein 2 magnetic resistances in the first set of magnetic resistances are separated by a distance d in a direction parallel to the periodic arrangement of the magnetic poles of the magnetic grid ruler N-S:

；

wherein k is an odd number, and L is a magnetic grid distance.

4. The magnetic grid sensor according to claim 2, wherein 2 magnetic resistances in the first set of magnetic resistances are separated by a distance d in a direction parallel to the periodic arrangement of the magnetic poles of the magnetic grid ruler N-S:

；

wherein L is the magnetic grid distance, and n is an even number larger than 2.

5. The magnetic grid sensor according to claim 2, wherein 2 magnetic resistances in the first set of magnetic resistances are separated by a distance d in a direction parallel to the periodic arrangement of the magnetic poles of the magnetic grid ruler N-S:

；

wherein L is the magnetic grid distance, and m is an odd number greater than 1.

6. The magnetic grid sensor according to any one of claims 2-5, comprising at least an inductive half-bridge of 2 magnetic induction elements, each of the magnetic induction elements acting as one leg of the inductive half-bridge; the projection distance of the 2 magnetic induction elements of the same induction half bridge in the periodic arrangement direction of the N-S magnetic poles of the magnetic grid ruler is D:

；

wherein L is the magnetic grid distance, and k is a positive integer.

7. The magnetic grid sensor according to claim 6 comprising at least one wheatstone full bridge consisting of two said inductive half-bridges.

8. The magnetic grid sensor according to claim 7, wherein a phase difference between the output signals of two of the sense half-bridges constituting the wheatstone full bridge is set toTo eliminate the h-order harmonic error; wherein h is a positive integer.