Eccentricity self-compensating magnetic encoder
By employing a combination of a dual-rail vernier code disk and a tunneling magnetoresistive sensor in the magnetic encoder, the measurement error problem caused by eccentricity error was solved, and high-precision rotation detection was achieved.
Patent Information
- Application Number
- CN202511653047.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-12
- Publication Date
- 2026-01-09
AI Technical Summary
Measurement errors caused by eccentricity during installation of magnetic encoders are difficult to avoid, affecting the accuracy of rotation detection.
It adopts a dual-rail vernier code disk structure, with different numbers of magnetic pole pairs on the inner and outer rail code disks. Two tunneling magnetoresistive sensors are used to measure the magnetic field changes of the inner and outer rail code disks respectively. The magnetic field signals are weighted and compensated through algorithm processing to eliminate eccentricity error.
It significantly improves the measurement accuracy of magnetic encoders, reduces fixed-cycle measurement errors caused by eccentricity errors, and enhances the accuracy of rotation detection.
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Figure CN121297907A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of magnetic encoder, and particularly relates to an eccentric self-compensation magnetic encoder. BACKGROUND
[0002] The magnetoresistance sensor is the latest generation of high-performance magnetic sensing technology for magnetic field detection, which is significantly superior to the traditional Hall effect sensor and can meet the needs of high-end measurement scenarios. However, in actual installation and use, the assembly error between the encoder and the motor shaft leads to eccentricity. Once the eccentricity deviation occurs, the detection sensitivity of the magnetic sensor will change with the viewing angle period during the rotation detection, forming a fixed period of measurement error, which becomes the main error source affecting the overall accuracy and is difficult to avoid. SUMMARY
[0003] The eccentric self-compensation magnetic encoder provided by the present application can compensate the measurement error caused by the eccentric error of the magnetic encoder during installation, so as to improve the measurement accuracy.
[0004] The present application provides an eccentric self-compensation magnetic encoder, the method comprising: A double-track vernier code disc, the double-track vernier code disc comprises an inner track code disc and an outer track code disc, wherein the inner track code disc comprises n pairs of annularly arranged magnetic poles, and the outer track code disc comprises m pairs of annularly arranged magnetic poles, wherein |m-n|=1; A first tunneling magnetoresistance sensor, the first tunneling magnetoresistance sensor corresponds to the inner track code disc, so that the first tunneling magnetoresistance sensor acquires the magnetic field change of the inner track code disc; A second tunneling magnetoresistance sensor, the second tunneling magnetoresistance sensor corresponds to the outer track code disc, so that the second tunneling magnetoresistance sensor acquires the magnetic field change of the outer track code disc; Wherein, the first tunneling magnetoresistance sensor and the second tunneling magnetoresistance sensor are respectively arranged on both sides of the axis of the double-track vernier code disc, and the center line of the first tunneling magnetoresistance sensor and the second tunneling magnetoresistance sensor and the axis of the double-track vernier code disc have an eccentric error caused by installation.
[0005] Optionally, the first tunneling magnetoresistance sensor and the second tunneling magnetoresistance sensor are both arranged parallel to the plane on which the double-track vernier code disc is arranged.
[0006] Optionally, the center position of the first tunneling magnetoresistance sensor is arranged at a position corresponding to the inner circle edge of the inner track code disc, and the center position of the second tunneling magnetoresistance sensor is arranged at a position corresponding to the outer circle edge of the outer track code disc.
[0007] Optionally, the first tunneling magnetoresistance sensor and the second tunneling magnetoresistance sensor are both arranged perpendicularly to a plane in which the dual-track vernier scale disc is located.
[0008] Optionally, the first tunneling magnetoresistance sensor is arranged inside the inner track scale disc corresponding to a height of the inner track scale disc, and the second tunneling magnetoresistance sensor is arranged outside the outer track scale disc corresponding to a height of the outer track scale disc.
[0009] Optionally, the first tunneling magnetoresistance sensor comprises two first tunneling magnetoresistance units with orthogonal magnetization directions of pinning layers, wherein one of the first tunneling magnetoresistance units outputs a sine signal with rotation of the inner track scale disc, and the other of the first tunneling magnetoresistance units outputs a cosine signal with rotation of the inner track scale disc. The second tunneling magnetoresistance sensor comprises two second tunneling magnetoresistance units with orthogonal magnetization directions of pinning layers, wherein one of the second tunneling magnetoresistance units outputs a sine signal with rotation of the outer track scale disc, and the other of the second tunneling magnetoresistance units outputs a cosine signal with rotation of the outer track scale disc.
[0010] Optionally, a free layer of the first tunneling magnetoresistance sensor reaches saturation magnetization at the inner track scale disc, and a free layer of the second tunneling magnetoresistance sensor reaches saturation magnetization at the outer track scale disc.
[0011] Optionally, a number n of pole pairs of the inner track scale disc and a number m of pole pairs of the outer track scale disc satisfy n = m - 1.
[0012] Optionally, a number n of pole pairs of the inner track scale disc and a number m of pole pairs of the outer track scale disc satisfy m = n - 1.
[0013] Optionally, magnetization directions of the pinning layers and the free layers of the first tunneling magnetoresistance sensor and the second tunneling magnetoresistance sensor are both in-plane.
[0014] In the technical scheme provided by the application, by constructing a double-track vernier code disc, the number of pole pairs of the inner track code disc and the outer track code disc is set to be different, and two tunneling magnetoresistance sensors are used to measure the magnetic field change of the inner track code disc and the outer track code disc, so that the phase difference of the magnetic field of the inner track code disc and the outer track code disc has uniqueness in the angle on the double-track vernier code disc, so that the absolute value of the rotation angle of the tunneling magnetoresistance sensor on the double-track vernier code disc can be calculated; and since the first tunneling magnetoresistance sensor and the second tunneling magnetoresistance sensor are arranged on the two sides of the axis of the double-track vernier code disc, when eccentric error occurs, with the rotation of the motor, the magnetic field change frequencies measured by the first tunneling magnetoresistance sensor and the second tunneling magnetoresistance sensor will show opposite change trends, when one of the magnetic field change frequencies changes from fast to slow, the other magnetic field change will show a change trend from slow to fast. Therefore, the inner and outer ring angle change trends calculated based on the magnetic field change trends are also opposite, and on this basis, the signals of the magnetic field changes sensed by the two tunneling magnetoresistance sensors can be processed by algorithm after weighted compensation to approach the accurate position. BRIEF DESCRIPTION OF DRAWINGS
[0015] Figure 1 FIG. 1 is a structural schematic diagram of an eccentric self-compensation magnetic encoder according to an embodiment of the application; Figure 2 FIG. 2 is a structural schematic diagram of an eccentric self-compensation magnetic encoder according to another embodiment of the application; Figure 3 FIG. 3 is a structural schematic diagram of an eccentric self-compensation magnetic encoder according to another embodiment of the application; Figure 4 FIG. 4 is a compensation principle diagram of an eccentric self-compensation magnetic encoder according to another embodiment of the application; Figure 5 FIG. 5 is a compensation result diagram of an eccentric self-compensation magnetic encoder according to another embodiment of the application. DETAILED DESCRIPTION
[0016] In order to make the purpose, technical scheme and advantages of the embodiments of the application clearer, the technical scheme of the embodiments of the application will be described clearly and completely below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the application.
[0017] The embodiments of the application provide an eccentric self-compensation magnetic encoder, as shown in FIG. 1, which comprises an inner track code disc, an outer track code disc and a motor. Figure 1 The method comprises the following steps: The double-track vernier code disc comprises an inner track code disc and an outer track code disc, wherein the inner track code disc comprises n pairs of annularly arranged magnetic poles, and the outer track code disc comprises m pairs of annularly arranged magnetic poles, and |m-n|=1. The first tunneling magnetoresistance sensor corresponds to the inner track code disc, so that the first tunneling magnetoresistance sensor acquires the magnetic field change of the inner track code disc. The second tunneling magnetoresistance sensor corresponds to the outer track code disc, so that the second tunneling magnetoresistance sensor acquires the magnetic field change of the outer track code disc. The first tunneling magnetoresistance sensor and the second tunneling magnetoresistance sensor are respectively arranged on two sides of the axis of the double-track vernier code disc, and the center line of the first tunneling magnetoresistance sensor and the second tunneling magnetoresistance sensor and the axis of the double-track vernier code disc have an eccentric error caused by installation.
[0018] In the technical scheme provided in the embodiment of the application, by constructing the double-track vernier code disc, the number of magnetic pole pairs of the inner track code disc and the outer track code disc is set to different numbers, and two tunneling magnetoresistance sensors are used to measure the magnetic field changes of the inner track code disc and the outer track code disc, so that the phase difference of the magnetic fields of the inner track code disc and the outer track code disc has a unique angle on the double-track vernier code disc, and thus the absolute value of the rotation angle of the tunneling magnetoresistance sensor on the double-track vernier code disc can be calculated; and since the first tunneling magnetoresistance sensor and the second tunneling magnetoresistance sensor are respectively arranged on two sides of the axis of the double-track vernier code disc, when the eccentric error occurs, with the rotation of the motor, the magnetic field change frequencies measured by the first tunneling magnetoresistance sensor and the second tunneling magnetoresistance sensor will present opposite change trends, and when one of the magnetic field change frequencies changes from fast to slow, the other magnetic field change will present a change trend from slow to fast. Therefore, the inner and outer ring angle change trends calculated based on the magnetic field change trends are also opposite, and on this basis, the signals of the magnetic field changes sensed by the two tunneling magnetoresistance sensors can be processed by an algorithm after weighted compensation, so as to approach the accurate position.
[0019] As an optional implementation manner, as shown in Figure 2 The first tunneling magnetoresistance sensor and the second tunneling magnetoresistance sensor are both arranged parallel to the plane on which the double-track vernier code disc is arranged.
[0020] As an optional implementation manner, the center position of the first tunneling magnetoresistance sensor is arranged at a position corresponding to the edge of the inner circle of the inner track code disc, and the center position of the second tunneling magnetoresistance sensor is arranged at a position corresponding to the edge of the outer circle of the outer track code disc.
[0021] As an optional implementation manner, as shown in Figure 3The first tunneling magnetoresistance sensor and the second tunneling magnetoresistance sensor are both arranged perpendicularly to the plane of the dual-track vernier scale disc.
[0022] As an optional implementation, the first tunneling magnetoresistance sensor is arranged inside the inner track scale disc corresponding to the height of the inner track scale disc, and the second tunneling magnetoresistance sensor is arranged outside the outer track scale disc corresponding to the height of the outer track scale disc.
[0023] As an optional implementation, the first tunneling magnetoresistance sensor includes two first tunneling magnetoresistance units with orthogonal magnetization directions of the pinned layer, one of which outputs a sine signal with the rotation of the inner track scale disc, and the other outputs a cosine signal with the rotation of the inner track scale disc. The second tunneling magnetoresistance sensor includes two second tunneling magnetoresistance units with orthogonal magnetization directions of the pinned layer, one of which outputs a sine signal with the rotation of the outer track scale disc, and the other outputs a cosine signal with the rotation of the outer track scale disc.
[0024] As an optional implementation, the free layer of the first tunneling magnetoresistance sensor reaches saturation magnetization at the inner track scale disc, and the free layer of the second tunneling magnetoresistance sensor reaches saturation magnetization at the outer track scale disc.
[0025] As an optional implementation, the number n of pole pairs of the inner track scale disc and the number m of pole pairs of the outer track scale disc satisfy n = m - 1.
[0026] As an optional implementation, the number n of pole pairs of the inner track scale disc and the number m of pole pairs of the outer track scale disc satisfy m = n - 1.
[0027] As an optional implementation, the magnetization directions of the pinned layer and the free layer of the first tunneling magnetoresistance sensor and the second tunneling magnetoresistance sensor are both in-plane.
[0028] In some embodiments, the in-plane tunneling magnetoresistance sensor has a saturation magnetic field. When the magnetic field generated by the scale disc is greater than the saturation magnetic field, the sine and cosine sensor groups in the tunneling magnetoresistance sensor only respond to the direction change of the magnetic field generated by the scale disc, and are irrelevant to the fluctuation amplitude of the magnetic field intensity. The tunneling magnetoresistance sensor reading the outer magnetic track can reach saturation magnetization at the outer magnetic track of the scale disc, and the tunneling magnetoresistance sensor reading the inner magnetic track can reach saturation magnetization at the inner magnetic track of the scale disc, thereby ensuring that the two tunneling magnetoresistance sensors only respond to the magnetic field direction change of the corresponding magnetic track.
[0029] As shown in FIG. 1, the scale disc 100 includes an inner track scale disc 110 and an outer track scale disc 120. The inner track scale disc 110 and the outer track scale disc 120 are arranged in parallel and concentrically, and the inner track scale disc 110 is arranged inside the outer track scale disc 120. Figure 4As shown, the compensation principle of the eccentric self-compensation magnetic encoder in the foregoing embodiments is illustrated as follows: In Figure 4 , the point where r1 and r2 are commonly connected is the rotation axis of the motor, and the point where p1 and p2 are commonly connected is the geometric center of the double-track vernier scale disc, and thus it can be known that ε is the eccentric error and θ is the actual rotation angle of the motor. According to the geometric relationship diagram and the cosine theorem shown in Figure 4 , it can be known that , that is, under the premise of fixed eccentric error, p1 will periodically change with the rotation angle of the motor. Similarly, according to the geometric relationship diagram and the cosine theorem shown in Figure 4 , it can be known that , that is, under the premise of fixed eccentric error, p2 will periodically change with the rotation angle of the motor. It should be noted that the change trend of p1 and p2 is opposite, and since p1 and p2 represent the actual distance from the tunneling magnetoresistance sensor to the double-track vernier scale disc, p1 and p2 further represent the angular velocity of the tunneling magnetoresistance sensor relative to the double-track vernier scale disc, that is, the frequency change of the tunneling magnetoresistance sensor magnetic field change curve, and since the frequency change trends of the magnetic field change curves of the two tunneling magnetoresistance sensors are opposite, the inner and outer ring angle change trends calculated based on the magnetic field change trends are also opposite, and on this basis, the signals of the magnetic field changes of the two tunneling magnetoresistance sensors can be processed and compensated by algorithm to approach the accurate position. Further, in order to more accurately measure the rotation position of the motor, the two tunneling magnetoresistance sensor magnetic field change curves calculated based on the foregoing p1 and p2 can be weighted, that is, the magnetic field change curve generated by the first tunneling magnetoresistance sensor with p1 is weighted with the magnetic field change curve generated by the second tunneling magnetoresistance sensor with p2 in the time axis after calculation to obtain an absolute angle that approaches the accurate position after self-compensation. The signals generated by the relationship between the foregoing p1 and p2 and ε can be obtained by simulation or measurement in advance to obtain prior data, and after the encoder is installed on the motor, the installed data is obtained by measurement, the installed data is compared with the prior data to obtain the corresponding curve relationship, and then the weighted data is applied in the process of measuring the rotation angle of the motor. It should be understood that since the maximum and minimum amplitudes of p1 and p2 are only related to ε, the corresponding curve relationship can be obtained by amplitude data comparison, and it is not necessary to apply θ angle. Meanwhile, the curve relationship between p1 and p2 and ε can be applied after the amplitude and the frequency of the magnetic field change curve are aligned in the weighting process.
[0030] As shown in Figure 5As shown, the horizontal axis is the rotation angle of the motor, the vertical axis is the error angle, the solid curve is the curve measured by the magnetic encoder with eccentric self-compensation, and the dotted curve is the curve measured by the magnetic encoder without eccentric self-compensation. Figure 5 In the above, the number of magnetic pole pairs of the inner track code disc in the double-track vernier code disc is set to 20, the number of magnetic pole pairs of the outer track code disc is set to 21, the eccentricity ε is 50 um, the radius r1 of the inner track code disc is 17 mm, and the radius r2 of the outer track code disc is 22 mm as an exemplary embodiment. When the encoder is not used with eccentric self-compensation, the measurement accuracy is about 0.6 degrees (dotted line), and when the magnetic encoder with eccentric self-compensation of the foregoing embodiments is used, the measurement accuracy is improved to 0.002 degrees (solid line). Obviously, the measurement accuracy of the magnetic encoder with eccentric self-compensation is significantly improved.
[0031] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.
Claims
1. An eccentric self-compensating magnetic encoder, characterized in that, The method includes: A dual-rail vernier code disk, comprising an inner rail code disk and an outer rail code disk, wherein the inner rail code disk comprises n pairs of magnetic poles arranged in a ring, and the outer rail code disk comprises m pairs of magnetic poles arranged in a ring, wherein |mn|=1; A first tunneling magnetoresistive sensor, corresponding to the inner rail code disk, is used to acquire changes in the magnetic field of the inner rail code disk. A second tunneling magnetoresistive sensor, corresponding to the outer rail encoder, is used to acquire changes in the magnetic field of the outer rail encoder. The first tunneling magnetoresistive sensor and the second tunneling magnetoresistive sensor are respectively disposed on both sides of the axis of the dual-rail vernier code disk. The line connecting the centers of the first tunneling magnetoresistive sensor and the second tunneling magnetoresistive sensor has an eccentricity error with the axis of the dual-rail vernier code disk due to installation.
2. The eccentric self-compensating magnetic encoder according to claim 1, characterized in that, Both the first tunneling magnetoresistive sensor and the second tunneling magnetoresistive sensor are arranged parallel to the plane of the dual-rail vernier code disk.
3. The eccentric self-compensating magnetic encoder according to claim 2, characterized in that, The center position of the first tunneling magnetoresistive sensor is set at the position corresponding to the inner edge of the inner rail code disk, and the center position of the second tunneling magnetoresistive sensor is set at the position corresponding to the outer edge of the outer rail code disk.
4. The eccentric self-compensating magnetic encoder according to claim 1, characterized in that, Both the first tunneling magnetoresistive sensor and the second tunneling magnetoresistive sensor are arranged perpendicular to the plane of the dual-rail vernier code disk.
5. The eccentric self-compensating magnetic encoder according to claim 4, characterized in that, The first tunneling magnetoresistive sensor is disposed inside the inner rail code disk, corresponding to the height of the inner rail code disk, and the second tunneling magnetoresistive sensor is disposed outside the outer rail code disk, corresponding to the height of the outer rail code disk.
6. The eccentric self-compensating magnetic encoder according to claim 1, characterized in that, The first tunneling magnetoresistive sensor includes two first tunneling magnetoresistive units with the magnetization directions of the pinned layers arranged orthogonally. One of the first tunneling magnetoresistive units outputs a sine signal as the inner rail code disk rotates, and the other first tunneling magnetoresistive unit outputs a cosine signal as the inner rail code disk rotates. The second tunneling magnetoresistive sensor includes two second tunneling magnetoresistive units with the magnetization directions of the pinned layers arranged orthogonally. One of the second tunneling magnetoresistive units outputs a sine signal as the outer rail code disk rotates, and the other second tunneling magnetoresistive unit outputs a cosine signal as the outer rail code disk rotates.
7. The eccentric self-compensating magnetic encoder according to claim 1, characterized in that, The free layer of the first tunneling magnetoresistive sensor reaches saturation magnetization at the inner rail code disk, and the free layer of the second tunneling magnetoresistive sensor reaches saturation magnetization at the outer rail code disk.
8. The eccentric self-compensating magnetic encoder according to claim 1, characterized in that, The number of magnetic pole pairs n of the inner rail encoder disk and the number of magnetic pole pairs m of the outer rail encoder disk satisfy n=m-1.
9. The eccentric self-compensating magnetic encoder according to claim 1, characterized in that, The number of magnetic pole pairs n of the inner rail encoder disk and the number of magnetic pole pairs m of the outer rail encoder disk satisfy m=n-1.
10. The eccentric self-compensating magnetic encoder according to claim 1, characterized in that, The magnetization directions of the pinned layer and the free layer of both the first tunneling magnetoresistive sensor and the second tunneling magnetoresistive sensor are in-plane oriented.